Journal of Environmental Management 206 (2018) 330e348
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Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Review
Prospects of banana waste utilization in wastewater treatment: A review Tanweer Ahmad a, Mohammed Danish b, * a
Department of Chemistry, College of Natural and Computational Science, Madda Walabu University, Bale Robe, Ethiopia Universiti Kuala Lumpur Malaysian Institute of Chemical and Bioengineering Technology, Lot No. 1988, Kawasan Perindustrian Bandar Vendor, Taboh Naning, Alor Gajah, 78000, Melaka, Malaysia
b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 July 2017 Received in revised form 19 September 2017 Accepted 26 October 2017
This review article explores utilization of banana waste (fruit peels, pseudo-stem, trunks, and leaves) as precursor materials to produce an adsorbent, and its application against environmental pollutants such as heavy metals, dyes, organic pollutants, pesticides, and various other gaseous pollutants. In recent past, quite a good number of research articles have been published on the utilization of low-cost adsorbents derived from biomass wastes. The literature survey on banana waste derived adsorbents shown that due to the abundance of banana waste worldwide, it also considered as low-cost adsorbents with promising future application against various environmental pollutants. Furthermore, raw banana biomass can be chemically modified to prepare efficient adsorbent as per requirement; chemical surface functional group modification may enhance the multiple uses of the adsorbent with industrial standard. It was evident from a literature survey that banana waste derived adsorbents have significant removal efficiency against various pollutants. Most of the published articles on banana waste derived adsorbents have been discussed critically, and the conclusion is drawn based on the results reported. Some results with poorly performed experiments were also discussed and pointed out their lacking in reporting. Based on literature survey, the future research prospect on banana wastes has a significant impact on upcoming research strategy. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Adsorption Banana waste Metal ions Dyes Radionuclides Pesticides
Contents 1. 2.
3.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 Utilization of banana waste derived adsorbents against environmental pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 2.1. Metal ions removal through banana waste derived adsorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 2.2. Removal of dyes from wastewater using banana waste derived adsorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 2.3. Removal of pesticides from contaminated water using banana waste derived adsorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 2.4. Removal of miscellaneous water-soluble organic compounds using banana waste derived adsorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 2.5. Removal of water-soluble inorganic anions using banana waste derived adsorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 2.6. Removal of water-soluble radioactive nuclides using banana waste derived adsorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 2.7. Removal of miscellaneous pollutants using banana waste derived adsorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 2.8. Possible mechanism of adsorption onto banana waste adsorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Conclusion and future perspective of research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
* Corresponding author. E-mail addresses: (M. Danish).
1. Introduction
[email protected],
https://doi.org/10.1016/j.jenvman.2017.10.061 0301-4797/© 2017 Elsevier Ltd. All rights reserved.
[email protected] Pristine water is an essential solvent for all living being growing
T. Ahmad, M. Danish / Journal of Environmental Management 206 (2018) 330e348
on planet earth, although bottom billions population on earth are struggling to get fresh potable water. The scarcity of water is the major concern of contemporary world. For last few decades, demand for potable water has increased exponentially due to rapid ~o population growth, the burgeoning of industrial growth and el nin ~ a effect on regular rainfall. With the modernization of and la nin civilization, many industrial products are entered into our lifestyle like plastics, phenolic products, petrol operated cars, industrial level food processing units. These industries and their products effectively degraded the existing pristine water source and polluted the soil, air, and water bodies to such an extent that it has an affecting human life. Presently, its effect showing through some specific diseases that occur across the world like arsenic contamination in many parts of West Bengal jute growing farmers in India, mercury contamination in Minamata Bay fish in Japan, due to the use of DDT contamination in water many birds became endangered species. In many countries, groundwater is the primary source of potable water for their local inhabitants in villages, small and medium cities. However, the ground and surface water quality are deteriorating due to the use of fertilizers and pesticides in agricultural activities, antibiotics, dyes, and heavy metals in industrial activities. The various industrial effluents continuously discharging into the river and ponds contain a wide variety of pollutants that are slowly entered into the natural ecosystem, it has a significant toxic impact on human health, aquatic habitats, and plant species. Recently, some highly toxic chemicals have been detected at alarming levels in drinking water at different parts of developing nations, posing a serious threat to human and aquatic life. Initially, when the chemical load was less, the soil function as an adsorbent to separate the toxicants from water and clean water pass to an underground aquifer, but with the rise of population and concentration of toxicants the soil adsorption capacity exhausted and now toxicants percolating to groundwater. The serious health problems like cancer, kidney failure, liver disorder, etc., arise owing to the high concentration of chemical pollutants. There is an urgent need of environmentally friendly and cheaper adsorbent material to eliminate chemical toxicants from potable water to improve the water quality. A wide range of scientific methods is accessible to a researcher with varying degree of success to minimize the water contamination. Some of reported techniques are reverse osmosis, solvent extraction, flocculation, membrane separation, filtration, chemical precipitation, oxidation, reduction, coagulation, ion exchange, evaporation, electrolysis (Ali and Jain, 2005; Gupta and Ali, 2003; Wojnarovits et al., 2010), photochemical reactions (Fox and Dulay, 1993), activated sludge (Bromley-Challenor et al., 2000), anaerobic and aerobic treatment (dos Santos et al., 2007), microbial reduction (Shen and Wang, 1994), bacterial treatment (LaPara et al., 2000), irradiation by nuclear radiation (Basfar and Abdel Rehim, 2002), electrodialysis (Ali et al., 2011), ultrasonic treatment (Suzuki et al., 2000), magnetic separation (Karapinar, 2003), and adsorption (Gupta and Ali, 2008; Danish et al., 2011a, 2011b, 2016a, 2016b; Li et al., 2016; Hashem and Amin, 2016) used to remove and/ or separate toxic contaminants from aqueous solutions. However, some of the techniques mentioned above have high operational cost, need highly skilled labor, and generates sludge at the end of the operation. Compared to other techniques adsorption methods have an advantage. The adsorption techniques through costeffective adsorbents offer some benefits such as easy to operate, so not required any high-skilled labor, environmentally safe, no health risk for the operator, and the process is non-destructive so that contaminants can be separated and recycled (Ahmad et al., 2011). The macropores, mesopores, and micropores in adsorbents can serve as a molecular sieve. Hence, it can be used for the adsorption of soluble and insoluble pollutants with large
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adsorption capacity. Undoubtedly, large surface area activated carbons are considered as a highly efficient adsorbent against various toxicants (Bansal and Goyal, 2005). Nevertheless, its extensive use in effluent treatment is sometimes restricted owing to the scarcity of cheaper activated carbons. The unconventional adsorbents from biomass waste and other carbon-rich sources have been tested against water-soluble contaminants; the reported research works have been reviewed extensively (Ahmad et al., 2011, 2010, 2012; Patel, 2012; Rafatullah et al., 2013; Nor et al., 2013; Abdolali et al., 2014; Mohan et al., 2014; Anastopoulos and Kyzas, 2014; Yahya et al., 2015; Bhatnagar et al., 2015; Jain et al., 2016; Gupta et al., 2015; Adegoke and Bello, 2015; Bhatnagar et al., 2010). It has been reported that under ordinary conditions, the activated carbon produced from various low-cost raw materials have little or poor adsorption capacity against various pollutants as compared to commercial coal-based activated carbon (Bhatnagar et al., 2015; DeMessie et al., 2015). Therefore, search for the low-cost raw material as well as the production method of activated carbon is going on. Many agricultural wastes were tried as an adsorbent, among them, banana waste has been of significant importance because it has various parts that can be utilized such as banana fruit peels, trunks, pseudo-stems, leaves, and piths. These parts of banana wastes have been extensively studied as an adsorbent against a wide range of pollutants. Banana wastes have attracted researcher's attention as an effective raw material for adsorbents owing to abundantly available, post fruit harvesting no proper utilization of the banana waste by the farmers, and a significant amount of carbon compounds present in it. Moreover, banana tree waste can cause serious environmental threat if its waste not properly managed, it can produce greenhouse gas if dumped in wet conditions. Usually, farmers threw the banana tree waste in rivers and ponds where it degraded slowly and formed methane, and other gases spread putricible smell and affect the nearby ecosystem. Therefore the selection of banana tree and fruit waste as an effective adsorbent material is a smart choice for sustainable future. Banana plants belong to the family Musaceae. The banana species suitable for consumption, belong to Australimusa and Eumusa series that has the different origin of the same genus. The commonly available human consumable banana is a member of Musa accuminata species. The worldwide growing species of Musa are M. cavendishii, M. paradisiaca, and M. sapientum (Mohapatra et al., 2010). Banana tree can bear fruit (nearly 20 fruits of banana grow to a hand (tier) and 3e20 hands can grow in a cluster) once in a lifetime, so lots of biomass waste generated from the tree. The banana plant has been initially grown in India, and Southeast Asian region (Malaysia and Japan). Whereas, some banana species are considered to be genetically linked with some African banana species (Anwar et al., 2010; De Langhe et al., 2009). Banana fruit is one of the most popular and highly nutritional fruit crops cultivated in more than 130 countries; the largest banana producing countries are located in tropical and sub-tropical regions. India, China, Philippines, Brazil, and Ecuador are the top 5 bananas growing countries according to 2016 data. The production of banana has considerable economic importance. In India, the banana production in 2016 was about 27.6 million metric ton, while the total world production of banana during 2016 was about 144 million metric ton (Vezina and den Bergh, 2016; Ali and Saeed, 2015). Among several wastes generated due to banana tree and fruit, the banana peel is one of the important waste generated in large quantities due to banana fruit consumption. Banana peel contributes about 40% of total weight of the fresh banana fruit (Anhwange et al., 2008). According to banana production data mentioned in above paragraph, it is evident that the banana industry produces banana peels more than 57.6 million metric tons annually. Banana
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peel contains carbon-rich organic compounds such as cellulose, hemicellulose, pectin substances, chlorophyll pigments, and some other low molecular weight compounds (Xiaomin et al., 2007). It is experimentally verified to be a good source of pectin (10e21%), lignin (6e12%), cellulose (7.6e9.6%), hemicelluloses (6.4e9.4%), and galacturonic acid (Mohapatra et al., 2010). Several tons of banana peel wastes are produced every day in fruit markets and household garbage, creating a nuisance smell due to anaerobic digestion of the biomass produces gases that are also affecting the natural balance of the atmospheric gases. Although ripe bananas are consumed without any processing, still large volumes of banana are industrially processed to convert it into banana chips and other long shelf-life products that generate a large quantity of banana peel waste. The food processing plants used to dispose of banana peels in a typical landfill. The conversion of banana peel into a useful material would thus bring an additional economic gain for the agricultural industry. The pseudo-stem of the banana produces a single bunch of banana fruit before drying and replaced by new pseudo-stem. The pseudo-stems are the stem of the banana tree that supplies nutrients from the soil to the fruits; it becomes waste after the banana fruit is harvested. It is estimated that each hectare of banana plantation produces nearly 220 tons of biomass waste. These banana wastes are disposed of by the cultivators into the rivers, lakes, or dump in low-lying areas; it is causing a serious threat to biosphere due to the release of greenhouse gas (Shah et al., 2005). Worldwide environmental science and engineering researchers engaged in experimenting to utilize such biomass materials to convert it into useful materials to prevent environmental toxicant generated due to it, and at the same time providing affordable waste disposal techniques. Therefore, it is rational that commercially feasible option to this issue should include the utilization of banana waste in new products formation for environmental remediation rather than disposal. Compared to other biomass wastes used as an adsorbent, banana wastes have been of great importance, because various parts of the banana tree have been extensively studied as an adsorbent against cationic, anionic, and neutral pollutants. Banana tree wastes have gained the wide interest of researcher due to abundantly available and significant adsorption capacity against water-soluble pollutants. According to our survey through various online and offline sources, no review on banana waste derived adsorbent is available for researchers to get an overview of banana waste utilization in wastewater treatment industry. In this review article, we tried to provide detail study of banana waste derived adsorbents utilization against various water-soluble pollutants such as dyes, heavy metals, pesticides, oils, organic compounds, etc. Past 20 years published data tabulated in this review with some of the significant findings are discussed in detail. The authors mentioned adsorption capacities of a banana tree, and fruit waste derived adsorbent, it should be taken at the particular set of experimental conditions rather than as an absolute adsorption capacity. 2. Utilization of banana waste derived adsorbents against environmental pollutants 2.1. Metal ions removal through banana waste derived adsorbents Mixing of water-soluble contaminants in aquifers owing to the indiscriminate disposal of heavy metal ions has been a matter of concern worldwide. Heavy metal ions are toxic to aquatic species (flora and fauna) and human beings even at low concentrations. The heavy metal ions pollution mainly originated from photography, iron and steel, electroplating, leatherworking, electric appliance manufacturing, metal surface treating, mining and
smelting, surface finishing industry, energy and fuel production, fertilizer and pesticide industry and application, metallurgy, aerospace and atomic energy installation industries. Due to nonbiodegradable nature of metal ions, it accumulates and transferred to a different living organism along with their food chain. Hence, their toxic effects are more expressed in the animals at higher trophic levels. They are causing a serious and chronic health issues to human. Banana wastes have been extensively explored by the researcher, as an adsorbent against a wide range of metal ions. DeMessie et al. (2015) compared the surface properties and adsorption capacity of the pyrolyzed and dried activated banana peel with commercial activated carbon (F-400) against an aqueous solution of Cu(II) ions. Pyrolytic activation of dried banana peels gives larger mesopores (49 Å) but smaller surface area (38.49 m2/g) adsorbent with dominantly negative surface charges compared to commercial activated carbon (F-400) that have smaller mesopores (30 Å) and large surface area (819 m2/g). The adsorption capacities of the commercial activated carbon (F-400) (2.39 mg/g) and prepared activated dried banana peel (38.4 mg/g) were compared and reported that later have better adsorption capacity. Although the dried banana peel has smaller surface area, the reason for the better adsorption capacity was the presence of opposite charge on the surface of the adsorbent. The banana peel derived adsorbents achieved a removal efficiency of 96% at lower initial concentration solutions. The isotherm data better fitted to the Langmuir isotherm. The sorption against time data fitted to a pseudo-second-order kinetic equation for both the adsorbents. The mechanism of adsorption against Cu(II) ions was explained through ion exchange and electrostatic interactions. The adsorbents from the banana peel and stem by direct sunlight drying and then activated with sodium hydroxide and formalin solutions (Hasanah et al., 2012). The prepared adsorbent was tested against Cu(II) ion present in textile industry effluent. The batch adsorption experiment was run to identify the suitable type of activating agent, adsorbent particle size, pH of the adsorbate solution, and contact time. The results implied that the optimum conditions for maximum adsorption of Cu(II) ion (adsorption capacity, 19.70 mg/g, removal efficiency, 89.01%) were formalin treated banana stem, with particle size 30 mesh, pH of Cu(II) ions solution 4.0, and contact time 12 h. The NaOH-treated banana peel adsorbent has adsorption capacity 13.24 mg/g and removal efficiency 59.81%, at particle size 20 mesh, pH of the Cu(II) ions solution 5.0, and contact time 24 h. The copper metal ions adsorption onto dried banana peel was experimentally tested by varying the independent parameters such as particle size, adsorbent dosage, solution pH, contact time, agitation speed, and temperature (Hossain et al., 2012). It was found that the low acidic solution (pH ¼ 6) favored the Cu(II) ion removal through the dried banana peel. The isotherm data were followed monolayer model; the adsorption capacity was calculated to be 27.78 mg/g. The pseudosecond-order kinetic model was followed by the Cu(II) ions adsorption onto the dried banana peel. For the recovery of the Cu(II) metal ions from the surface of the adsorbent, 0.10 N sulfuric acid solution was found to be effective for desorption. Around 94% of the adsorbed Cu(II) ions can be recovered through 0.1 N sulfuric acids washing. Renata et al. (2011) reported the adsorption capacity of grounded banana peel to remove lead and copper ions. The equilibrium of copper and lead adsorption achieved within 10 min, and the removal of Cu(II) and Pb(II) ions were favorable at pH > 3. The FTIR technique was used to characterize the banana peel powder, the spectra shown transmittance peaks of carboxylic and amine groups at 1730 cm1 and 889 cm1, respectively. The isotherm data of copper and lead were found to follow Langmuir model with maximum adsorption capacities 20.97 mg/g and 41.44 mg/g for
T. Ahmad, M. Danish / Journal of Environmental Management 206 (2018) 330e348
Cu(II) and Pb(II), respectively. The banana peel powder was also used in pre-concentration experiments and found nearly 20-fold enrichment factor, and still, the column could be reused for 11 cycles without much loss in recovery. The scheduled method was used for the estimation of Cu(II) and Pb(II) in a real sample of river water. The obtained results were validated by comparing with a standard reference adsorbents. The banana peels carbon foam (BPCF) was used against the various heavy metal ions such as Cu2þ, Pb2þ, Cd2þ and Cr6þ ions (Li et al., 2016). The role of adsorption parameters such as pH, contact time, temperature, and initial concentration was investigated in batch experiments. Kinetic and equilibrium data showed that the adsorption behavior was better described by the pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The maximum adsorption capacities of BPCF against Cu2þ, Pb2þ, Cd2þ, and Cr6þ were estimated to be 49.5, 45.6, 30.7 and 25.2 mg/g within 5 min equilibrium time. The adsorption against temperature data showed that the metal ions sorption onto the BPCF was an endothermic and spontaneous reaction process. The removal efficiency of the adsorbent (BPCF) for removing metal ions were reported to be 98.00% after 1 h contact time. Compared with other banana peel derived other adsorbents, BPCF showed significantly increased adsorption capacity against these four metal ions. This enhanced adsorption capacity of BPCF may be attributed to the ion exchange capacity and the favorable microprecipitation of metal ions on the surface. The removal of Pb(II) and Cd(II) ions through banana peel derived powdered adsorbent has been studied in a batch experiment (Anwar et al., 2010). Experimental parameters like banana peel powder dosage, pH, contact time, and agitation speed were evaluated to get maximum adsorption capacity. The obtained isotherm data were applied to Langmuir, Freundlich, and Temkin isotherms to describe adsorption behavior of Pb(II) and Cd(II) ions onto banana peel powder. The isotherm data were followed Langmuir model, the maximum adsorption capacity (qm) of banana peel powder against Pb(II) and Cd(II) ions were found to be 2.18 mg/ g and 5.71 mg/g, respectively. The banana trunk fibers (BTF) were utilized as an adsorbent for the removal of Cd(II), Cu(II), Fe(II), and Zn(II) from aqueous solutions (Sathasivam and Haris, 2010). The change in adsorption capacity of the BTF was investigated with the variation of pH, contact time, metal ions (Cd(II), Cu(II), Fe(II), and Zn(II)) initial concentration, BTF dosage, and ratio of [M2þ]/biomass at room temperature (25 C). The isotherm data were well explained by the Freundlich isotherm model, the adsorption capacity of BTF against Cd(II), Cu(II), Fe(II), and Zn(II) calculated through Freundlich model constant (Kf) were found to be 8.49, 2.68, 6.58, and 1.74 mg/g, respectively. Moreover, it was found that the adsorption capacity of BTF was strongly guided by the initial metal ion concentration and solution pH. The kinetics of adsorption of metal ions (Cd(II), Cu(II), Fe(II), and Zn(II)) onto BTF has followed the pseudo-second-order model. The BTF was tried to modify with different chemical methods (acetylation, mercerization, peroxide treatment, sulphuric acid treatment, stearic acid treatment, and formaldehyde treatment) to improve the adsorption capacity (qe) against the metal ions. But results indicated that there was no noticeable improvement in the adsorption capacity (qe) of chemically modified BTFs. From these results, a conclusion was drawn that either BTF surface was not effectively modified for enhancing the uptake of metal ions or BTF surface already having a suitable chemical composition for optimum removal of heavy metal ions. The banana stalk has been activated with acidic and basic activating agents and compared their adsorption capacity for Pb(II) ions removal from aqueous solution (Ogunleye et al., 2014). The prepared raw banana stalk (RBS), acid activated Banana Stalk (AABS), and base activated banana stalk (BABS) samples were also
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characterized by x-ray photoelectron spectroscopy (elemental composition) and FTIR (surface functional groups). The surface functional group analysis showed that RBS, AABS, and BABS are decorated with carboxyl, hydroxyl, and phenolic functional groups. The adsorption of Pb(II) ion onto RBS, AABS, and BABS were tested with a change in adsorbent dose, temperature, initial Pb(II) ion concentration, contact time, and pH of the solution. The equilibrium time for adsorption was established in 180 min and the removal efficiencies of RBS, AABS, and BABS were found to be 63.97%, 96.13%, and 66.90% for Pb(II) ions, respectively. The acid treated banana stalk adsorbent (AABS) had enhanced adsorption efficiency against Pb(II) ions, and the pseudo-second-order kinetic model was the common model for all three adsorbents to describe the rate of Pb(II) ion adsorption onto RBS, AABS, and BABS. The maximum adsorption capacity through Langmuir isotherm model was reported for AABS (qmax ¼ of 13.53 mg/g). Thermodynamic parameters suggested that adsorption of Pb(II) onto banana stalk adsorbents were spontaneous (DG0 values were negative) and endothermic (positive DH0 and DS0) in nature. From the finding of this study, it was inferred that acid activated banana stalk biosorbent was effective for lead ions removal from aqueous solution. The scavenging of Cd(II) from natural water aquifers (river, lake, and ponds) samples and industrial effluent (from Sindh, Pakistan) by banana peel derived adsorbents were investigated (Memon et al., 2008). The banana peel was dried and powdered for using it as an adsorbent. The authors also tried to modify the surface functional group of powdered banana peel through esterification reaction and compared their adsorption against aqueous solution Cd(II) ions. The experimental results revealed that after esterification of dried banana peel the adsorption capacity of the adsorbent diminished tremendously from 99% to 00%. So, it was inferred from the FTIR results that presence of eCOOH groups in the dried banana peel was responsible for the adsorption of the Cd(II) ions, when it converted into eCOOR, the adsorption of metal ions affected. The dried banana peel powder was explored for the adsorption of Cd(II) ion by varying the parameters such as pH, contact time, initial Cd(II) ion concentration, and temperature. It was reported that adsorption of Cd(II) onto dried banana peel powder was efficient and rapid (~97% within 10 min) at suitable pH value. The adsorption was found to be highly pH dependent. At pH 1.0, no significant amount of Cd(II) adsorbed on the dried banana peel powder. With the rise of pH of the solution adsorption of Cd(II) increased till pH 8.0, around 80% adsorption takes place at pH 3.0, then gradually adsorption increased up to 96% at pH 8.0, after pH 8.0 adsorption started to fall again. The metal binding to dried banana peel surface site was attributed to the presence of R-COO- groups which have pKa in the range of 3.5e5.0. The hydroxyl groups can also be found in most of the polysaccharides, but it is less abundant in the banana peel, hydroxyl groups acquire negative charge at high pH values. Hence, these functional groups served as the sorption sites for Cd(II) metal ions that were highly pH dependent. The influence of contact time on sorption of Cd(II) revealed that maximum adsorption takes place in 10 min, and only slight increase in adsorption was observed in next 20 min. The pseudo-second-order kinetic model was better explained the adsorption behavior of Cd(II) ions onto dried banana peel adsorbent. The effect of temperature study showed that adsorption of Cd(II) was observed to be increased with the rise of temperature, the standard enthalpy change and standard Gibbs free energy change indicated that adsorption was endothermic and spontaneous, respectively. The isotherm study was conducted in the concentration range of 0.10e500 mg/L, and it was observed that isotherm data was followed the monolayer adsorption (Langmuir model) at room temperature. The adsorption capacity (qe) of dried banana peel was calculated through Langmuir isotherm, and it was reported to be
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35.53 mg/g, which is considering to be good adsorption capacity for waste materials without any chemical or physical processing. The desorption ability of the dried banana peel adsorbent was tried with HNO3, H2SO4, HCl, NaOH, and NH3, and it was reported that 5 mL of 0.005 M HNO3 solution could recover 100% adsorbed Cd(II) ions. The removal of Cd (II) from aqueous solution was also tried with banana peels activated carbon (BPAC) in batch experiment (Mohammad et al., 2015a). The similar adsorption parameters as dried banana peel powder were tested for adsorption capacity of banana peel activated carbon (BPAC) at 25 C temperature. The percent removal of Cd(II) ions was reported to be 98.35% for 20 mg/ L synthetic Cd(II) solution with 0.80 g adsorbent dosage. The experimental percent removal of Cd(II) was found maximum at pH 4.0, and the kinetics of the of adsorption was followed, pseudosecond-order kinetic model. The isotherm data were followed the Langmuir model, that indicated monolayer of adsorption behavior. The surface characterization of the BPAC showed that major functional groups such as, -OH, -C¼O and aromatic rings were present. Memon et al. (2009) reported the adsorption and recovery of Cr(VI) from industrial wastewater using dried banana peel as an adsorbent. It was reported that the adsorption of Cr(VI) onto dried banana peel was found to be efficient and rapid (95% within 10 min) with adsorption capacity 131.56 mg/g at initial concentration range 0.10e100 ppm and adsorbent dosage 0.1 g. The adsorption was favored at lower pH (optimum pH was 2.0) and with the increase of solution pH the adsorption was found to be decreasing. The rapid adsorption was followed the pseudo-second-order kinetic model. The isotherm data were followed the Langmuir and DubinineRadushkevich (DeR) models at different isothermal temperatures. The thermodynamic studies revealed that Cr(VI) adsorption was spontaneous (negative free energy change) and exothermic (negative enthalpy change) in nature. The adsorbed Cr(VI) ions were recovered with 5 mL of 2.0 M H2SO4 solution. Presence of ferrous (Fe(II)) ions in the solution suppressed the adsorption of Cr(VI) ions onto the dried banana peel adsorbent, due to competitive adsorption of metal ions. The adsorption of Cr(VI) and Ni(II) ions from aqueous onto the ordinarily dried banana peel (BPD) and microwave activated banana peel (BPM) adsorbents were compared in batch experiments (Liu et al., 2014). The experimental results revealed that the adsorption capacity of microwave activated banana peel (BPM) adsorbent was much higher for Cr(VI) and Ni(II) ions compared to dried banana peel powder (BPD) adsorbent. The variation in pH of the adsorbate solution affected the adsorption capacity of both adsorbents (BPD and BPM) for Cr(VI) and Ni(II) ions, the lower pH (acidic) of the adsorbate solution was found to be better suited for maximum adsorption capacity. The kinetics of the Cr(VI) and the Ni(II) ions adsorption onto BPM was followed pseudo-second-order model. Whereas, the adsorption onto BPD was neither followed Lagergren first-order kinetic model nor pseudo-second-order model. The isotherm data of Cr(VI) and Ni(II) adsorption onto both the adsorbents (BPD and BPM) were followed the Freundlich isotherm model with high regression coefficient (R2) values. A summary of adsorption capacities of banana waste adsorbents for the removal of various metal ions has been presented in Table 1. 2.2. Removal of dyes from wastewater using banana waste derived adsorbents The natural dyes have old history to be used, but synthetic dyes have been used in the modern-day industries such as paper and pulp, textiles, plastics, leather, cosmetics, and food industries. The synthetic dyes have a slow degradation rate that causes numerous impact on the aquatic environment. Pollution caused by the
discharge of textile wastewater into the water bodies is a common issue for many developing countries. They impose a threat to the environment and ecosystem resulting to toxicity in human and aquatic organisms. The release of synthetic dyes through the industrial effluents into the water channels affects the people, who use these water for washing, bathing, and drinking in their daily activities (Sharma and Sobti, 2000). The dye contaminated water is acutely toxic to aquatic flora and fauna. It can instigate mutagenic and carcinogenic activity inside the living cell. It may cause severe damage to the human endocrine systems such as dysfunction of the kidneys, reproductive system, central nervous system, brain, and liver (Foo et al., 2013; Shen et al., 2009). Thus, the remediation of dyes from industrial as well as household wastewater is an urgent call before they contaminated our water surface and ground water source. In recent past, banana waste derived adsorbents have been investigated for its adsorption capacity against different classes of synthetic dyes. Under specified conditions of pH (4.0e8.0) and temperature (20 C), the maximum adsorption capacity of dried banana peel powder and activated banana peel carbon was found to be 18.647 mg/g and 19.671 mg/g, respectively (Amel et al., 2012). With the rise of the initial concentration of the dye solution, the sorption capacity of the adsorbents (dried banana peel powder and activated banana peel carbon) found increasing. The adsorption isotherm data suggested that methylene blue adsorption onto activated banana peel carbon was multilayer (followed Freundlich isotherm). Whereas, adsorption onto dried banana peel powder was monolayer (followed Langmuir isotherm). The adsorption rate of methylene blue followed the pseudo-second-order kinetic models for both the adsorbents. The surface characterization of the adsorbents through Fourier transformed infrared spectroscopy (FTIR) analysis indicated the presence of an amine, hydroxyl, and carbonyl functional groups, which is active binding sites for the biosorption of dye molecules from aqueous solution. Hameed et al. (2008) reported the sorption of methylene blue using banana stalk waste adsorbents. The adsorbent from banana stalk was prepared by drying it at 60 C for 48 h, then grind it into a fine powder, used it without any physical or chemical modification. The batch experiments were used to observe the effect of pH and initial dye concentration for maximum basic dye (methylene blue) removal. It was reported that at pH 2.0, the adsorption capacity of the dried banana stalk adsorbent was found to be poor (~30 mg/g). However, adsorption capacity raised significantly at pH 4.0 and remain almost constant till pH 12.0 (~85 mg/g) for 100 mg/L dye solution at 30 C, adsorbent dosage 1.0 g/L, and stirring speed 100 rpm. The variation in initial concentration of dye from 50 mg/l to 500 mg/L was observed at fixed pH (7.0), fixed temperature (30 C) and adsorbent dosage 1.0 g/L. At lower concentration of dye, the adsorption capacity was poor (~41.04 mg/g), but removal efficiency was higher (~75.87%), whereas at higher dye concentration the adsorption capacity was higher (~201 mg/g) and removal efficiency was lower (~40%). The adsorption isotherm data of methylene blue and banana stalk waste adsorbent were best represented by monolayer (Langmuir isotherm model), with the help of Langmuir isotherm model constant. The maximum monolayer adsorption capacity was calculated to be 243.90 mg/g. The pseudo-secondorder kinetic model was best represented the sorption rate of methylene blue onto dried banana stalk powder adsorbent. The adsorption of methylene blue through activated and inactivated banana peel powders were investigated (Gautam and Khan, 2016). The adsorption experiments were conducted under different pH, adsorbent dose, and contact time. For both the adsorbent it was observed that the removal efficiency decreased as the adsorption capacity increased. The percentage removal in activated banana peel powder adsorbent increased from 65% to 90%, when the dose
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Table 1 Adsorption capacities of banana waste based biosorbent for the removal of metal ions. Adsorbent
Adsorbate Qm (mg/g) Conc.
Pyrolyzed banana peel Cu(II) Banana Peel Cu(II) Banana Stem Cu(II) Banana peel Cu(II) Banana peel Cu(II) Banana peel Pb(II) Banana peel carbon foam Cu(II) Banana peel carbon foam Pb(II) Banana peel carbon foam Cd(II) Banana peel carbon foam Cr(VI) Banana peel Pb(II) Banana peel Cd(II) Banana trunk fiber Cd(II) Banana trunk fiber Cu(II) Banana trunk fiber Fe(II) Banana trunk fiber Zn(II) Raw banana stalk Pb(II) Acid activated banana stalk Pb(II) Base activated banana stalk Pb(II) Banana peel Cd(II) Banana peel AC Cd(II) Banana peel Cr(VI) Normally dried banana peel Ni(II) Normally dried banana peel Cr(VI) Microwave activated banana peel Ni(II) Microwave activated banana peel Cr(VI) Polymer-grafted banana stalk Pb(II) Polymer-grafted banana stalk Cd(II) Banana peel Cu(II) Banana peel Pb(II) Banana peel Zn(II) Banana peel Ni(II) Banana peel Cd(II) Banana peel cellulose Cu(II) Banana peel cellulose Pb(II) Banana peel cellulose Zn(II) Banana peel cellulose Ni(II) Banana peel cellulose Cd(II) Raw banana peel Fe(II) Grafted banana peel Fe(II) Charred banana peel Fe(II) Banana peel Cu(II) Banana frond AC Total iron Banana pith carbon Hg(II) Banana pith carbon Ni(II) Banana peel Zn(II) Banana trunk Cu Banana trunk As Banana trunk Pb Banana trunk Zn Banana peel Co(II) Banana peel Ni(II) Fresh banana peel biochar Pb(II) Dehydrated banana peel biochar Pb(II) Grafted banana peel Cr (VI) Banana peel activated carbon Cu (II) Banana peel activated carbon Ni(II) Banana peel activated carbon Pb(II) Activated banana stem fiber-HCl Hg (II) Fresh banana stem-HCl Hg (II) Formaldehyde polymerized banana stem Hg (II) Formaldehyde polymerized banana stem Pb (II) NaOH-modified banana peel Pb (II) Carboxyl banana stem Hg (II) Banana peel carbon Au (III) Banana peel activated carbon Mn (II)
351.1 13.235 19.7 27.78 41.44 20.97 49.5 45.6 30.7 25.2 2.18 5.71 8.49 2.68 6.58 1.74 e 13.53 e 35.52 0.719 131.56 8.71 7.22 14.97 24.13 185.34 65.88 52.36 25.91 21.88 54.35 34.13 140.85 101.01 104.17 133.33 76.92 1.47 0.93 1.81 42.69 12.81 e e e 1.03 1.04 0.94 1.04 9.02 8.91 193 359 3.83 14.3 27.4 34.5 372 28 132.25 91.74 90 90.33 801.7 11.806
e e e 10 mg/l e e e e e e 50 mg/ml 50 mg/ml 10 mg/l 10 mg/l 10 mg/l 10 mg/l e e e e 20 mg/l e e e e e 25 mg/dm3 25 mg/dm3 e e e e e e e e e e e e e 3.8 mg/ml 9.31 mg/l e e e e e e e e e e e 400 mg/l 85 mg/l 90.3 mg/l 74.4 mg/l e e e 10 mg/l e 10 mg/l e 20 mg/l
Contact Time Temp. e 24 h 12 h 24 h 10 min 10 min 5 min 5 min 5 min 5 min 20 min 20 min 60 min 60 min 60 min 60 min 180 min 180 min 180 min e e 30 min 5h 5h 5h 5h 3h 3h 24 h 24 h 24 h 24 h 24 h 24 h 24 h 24 h 24 h 24 h e e e e e 24 h 24 h 260 min 100 min 100 min 100 min 100 min 30 min 30 min 3h 3h 120 min e e e 3h 1.5 h e 1h 300 min 3h 30 min 2h
of the adsorbent was increased from 0.02 g to 0.10 g. In the case of inactivated adsorbent, the adsorption efficiency was increased from 55% to 84% with the increment of adsorbent dosage in the range of 0.02 g to 0.10 g. At fixed contact time of 120 min, the adsorption efficiency of two adsorbent has a noticeable difference. The
e e e 20 C e e 30 C 30 C 30 C 30 C 25 C 25 C 25 C 25 C 25 C 25 C e e e 30 C 25 C e 293 K 293 K 293 K 293 K 30 C 30 C 28 C 28 C 28 C 28 C 28 C 28 C 28 C 28 C 28 C 28 C e e e e 30 C
pH
e 5.0 4.0 6.0 3.0 3.0 4.0 4.0 4.0 4.0 5.0 3.0 5.0 5.0 5.0 5.0 e e e 8.0 4.0 2.0 e e e e 6.5 6.5 e e e e e e e e e e e e e e e 4.39 4.59 e 4.0 e 6.0 e 6.0 e 6.0 e 6.0 303 K 5.5 303 K 5.5 Room temperature e Room temperature e e 3.0 e 6.5 e 6.4 e 6.1 e 7.0 e 7.0 30 C 7.0 30 C 6.0 e 5.0 30 C e e 2.5 25 C 5.0
% Removal Ref. e e e e e e e e e e e e e e e e 63.97 96.13 66.9 97 98.35 95 e e e e e e e e e e e e e e e e e e e 89.47 95.14 100 96.4 90.5 95.8 75.4 99.36 97.24 e e e e 96 e e e e e 99.3 98.6 e 99.3 e 97.4
DeMessie et al. (2015) Hasanah et al. (2012) Hasanah et al. (2012) Hossain et al. (2012) Renata et al. (2011) Renata et al. (2011) Li et al. (2016) Li et al. (2016) Li et al. (2016) Li et al. (2016) Anwar et al. (2010) Anwar et al. (2010) Sathasivam and Haris (2010) Sathasivam and Haris (2010) Sathasivam and Haris (2010) Sathasivam and Haris (2010) Ogunleye et al. (2014) Ogunleye et al. (2014) Ogunleye et al. (2014) Memon et al. (2008) Mohammad et al. (2015a) Memon et al. (2009) Liu et al. (2014) Liu et al. (2014) Liu et al. (2014) Liu et al. (2014) Shibi et al. (2006) Shibi et al. (2006) Thirumavalavan et al. (2011) Thirumavalavan et al. (2011) Thirumavalavan et al. (2011) Thirumavalavan et al. (2011) Thirumavalavan et al. (2011)) Thirumavalavan et al. (2011) Thirumavalavan et al. (2011) Thirumavalavan et al. (2011) Thirumavalavan et al. (2011) Thirumavalavan et al. (2011) Yousaf and Sajjad (2015) Yousaf and Sajjad (2015) Yousaf and Sajjad (2015) Pandharipande and Deshpande (2013) Foo et al. (2013) Kadirvelu et al. (2003) Kadirvelu et al. (2003) Rajoriya and Kaur (2014) Yasim et al. (2016) Yasim et al. (2016) Yasim et al. (2016) Yasim et al. (2016) Abbasi et al. (2013) Abbasi et al. (2013) Zhou et al. (2017) Zhou et al. (2017) Ali et al. (2016) Thuan et al. (2017) Thuan et al. (2017) Thuan et al. (2017) Salamun et al. (2015) Salamun et al. (2015) Mullassery et al. (2014) Noeline et al. (2005) Massocatto et al. (2013) Anirudhan et al. (2007) Zheng and Wang (2013) Mahmoud et al. (2014)
adsorption efficiency of activated adsorbent was found to be 94%, whereas, for inactivated adsorbent, it was found to be 90%. The adsorption of methylene blue onto the banana peel adsorbent was followed the Langmuir isotherm model (i.e., the monolayer adsorption of methylene blue onto the banana peel adsorbent).
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Bello et al. (2012) reported the removal of malachite green dye using chemically treated banana stalk activated carbon. The solution pH was optimized for maximum removal of the malachite green dye through banana stalk activated carbon; it was observed pH 8.0 was the optimum pH for maximum adsorption. The isotherm data was best fitted to Langmuir model, the qmax (maximum adsorption capacity) calculated through the model was 141.76 mg/g. Initially, the rate of adsorption of dye was fast, and equilibrium attained within 120 min. The rate of adsorption was followed the pseudo-second-order kinetic model. The adsorption at various temperatures was used to calculate thermodynamic parameters such as a change in standard Gibbs free energy, enthalpy, and entropy; the results showed that adsorption process was spontaneous and endothermic. Desorption of malachite green was also studied using 0.50 M HCl solution to know the regeneration efficiency of activated carbon. It observed that 90.22e95.16% removal was possible after four cycles of regeneration. The adsorption of safranin dye was studied using banana pseudo-stem fibers (de Sousa et al., 2014). Results revealed that adsorption was pH dependent and also affected by the initial concentration of dye and temperature variations. The isotherm data were followed the Sip isotherm model with high precision. The qmax calculated through Sips model was 21.74 mg/g at 20 C, which was very close to the experimentally calculated qmax (18.61 mg/g) at 20 C with initial safranin dye concentration 40 mg/L. The adsorption against contact time data followed the pseudo-second-order kinetic model. The adsorption against temperature data showed that the adsorption of safranin dye onto banana pseudo-stem fiber was spontaneous (DG ¼ 30 kJ/mol) and exothermic (DH ¼ 17 kJ/mol) in nature. Kumar et al. (2010) explained the adsorption of acid violet 54 (AV54) dyes onto banana peel adsorbent. The adsorption was affected by the initial concentration of AV 54 dye, adsorbent dosage, solution pH, and temperature. The percentage of adsorption percentage decreased from 84.10% to 66.10%, as the initial concentration of AV54 dye increased from 50 mg/L to 200 mg/L. It was also observed that percentage removal increased from 42.10% to 85.20% as the adsorbent dosage increased from 0.10 g to 0.60 g in 100 mL dye solution. Maximum uptake of dye was reported for acidic (pH 2) solution. The isotherm data followed Langmuir isotherm model with a high coefficient of regression (R2 ¼ 0.9993). The adsorption data against time was followed a pseudo-second-order kinetic model more precisely. The effect of temperature on adsorption of AV54 dye was studied in batch mode at temperatures of 30, 40 and 50 C. It was observed that with the rise of temperature the adsorption capacity decreased from 20.63 mg/g (at temperature 30 C) to 11.46 mg/g (at temperature 50 C). Based on the temperature study the thermodynamic parameter showed that the biosorption process was exothermic. Methylene blue and orange II dyes were tried to remove from aqueous solution using banana peel derived large surface area (1950 m2/g) activated carbon (Ma et al., 2015). Results based on adsorption studies were used to calculate the maximum adsorption capacity of banana peel activated carbon against orange II, and methylene blue was 333 and 1263 mg/g, respectively. The isotherm and kinetic data were well fitted to Langmuir isotherm model and pseudo-second-order kinetic model. We summarized the adsorption capacities of banana waste derived adsorbents against various dyes in Table 2. 2.3. Removal of pesticides from contaminated water using banana waste derived adsorbents The use of synthetic pesticides in agricultural activities and residential area increased significantly that slowly transferred to surface and groundwater. The presence of pesticide in water signaling a great threat to the wildlife and the human life (Ahmad
et al., 2010). Excessive use of pesticides disturbs the ecosystem by entering the food chain of a living organism. They are harmful to the living organism because of its toxicity, mutagenicity, and carcinogenicity. Acute exposure to pesticide causes neurobehavioral disorder, autoimmune disease, reproductive abnormalities, lifethreatening bleeding, malignant lymphoma, nausea, vomiting, sweating, etc. (Corsini et al., 2008). Therefore, pesticide-loaded effluent treatment is needed before mixed up with natural water bodies. Banana waste derived adsorbents have been widely investigated for its adsorption capacity against different types of watersoluble pesticides. Salman and Hameed (2010) reported the adsorption of carbofuran from contaminated water using banana stalk activated carbon (BSAC). The banana talk activated carbon was prepared through chemical activation using KOH in the presence of N2 and CO2 gas. The adsorption study was conducted with variation in the contact time, pH of the solution, initial carbofuran concentration, and temperature. It was reported that BSAC has BET surface area 981.62 m2/g and average pore width 2.88 nm was capable of maximum adsorption capacity of 164 mg/g at 50 C. The adsorption behavior was verified through Langmuir isotherm and pseudosecond-order kinetic model. The rise in temperature from 30 to 50 C increased the adsorption capacity of the BSAC from 156.3 mg/ g to 164.0 mg/g, respectively. The thermodynamic parameters of the adsorption of carbofuran were showing spontaneous and endothermic nature. The regeneration of pesticide was tested in three cycles using ethanol. The regeneration efficiency of BSAC was in the range of 96.97e97.35% after each cycle. While regenerated BSAC adsorption capacity against carbofuran decreased from 98.40 to 85.00% during first to third regeneration cycles. Salman et al. (2011) reported the same banana stalk activated carbon (BSAC) to investigate the removal of the pesticides 2, 4Dichlorophenoxyacetic acid and bentazon from aqueous solution. The adsorption data revealed that the maximum adsorption capacity of BSAC against 2, 4-dichlorophenoxyacetic acid and bentazon were 196.33 and 115.07 mg/g, respectively. The different adsorption capacity observed for 2, 4-dichlorophenoxyacetic acid and bentazon was due to the presence of eCl ions (electron-withdrawing group) on the aromatic ring and smaller molecular size of 2, 4-dichlorophenoxyacetic acid. The adsorption capacity against time data followed the pseudo-second-order kinetic model. The adsorption isotherm data were best-fitted multilayer adsorption isotherm model (Freundlich model). The adsorption of both pesticides (2, 4-dichlorophenoxyacetic acid and bentazon) against BSAC at temperatures of 30, 40 and 50 C were conducted and found that the adsorption capacity was decreasing with the rise of temperature. The thermodynamic parameters showed that the adsorption was feasible and spontaneous with exothermic in nature. Phosphoric acid treated charred banana peel was used as an adsorbent for the scavenging of atrazine from water solution (Chaparadza and Hossenlopp, 2012). The adsorption was observed to be pH and temperature dependent. The adsorbent was successfully removing more than 80% of atrazine from water at solution pH ranging between 2.0 and 8.0, the result indicated that charred banana peel adsorbent was suitable for acidic as well as the basic solution. The isotherm data of atrazine adsorption onto charred banana peel was followed Langmuir isotherm model, the maximum monolayer adsorption capacity was determined through the model was found to be 14 mg/g. The standard Gibbs free energy (DG ) and standard enthalpy change (DH ) values showed that the adsorption was spontaneous and endothermic. Mass transfer model was applied to prove that both external mass transfer and intraparticle diffusion have significant contribution in the scavenging mechanism. Silva et al. (2013) used banana peel as an adsorbent for the
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Table 2 Adsorption capacities of banana waste based biosorbent for the removal of dyes. Adsorbent
Adsorbate
Qm (mg/g)
Conc.
Contact Time
Temp.
pH
% Removal
Ref.
Banana peel Activated banana peel Pseudo stem banana fiber Banana fibre Banana peel AC Banana stalk AC Banana pith Banana peel AC Banana Bunch AC Banana stalk waste Banana pith carbon Banana pith carbon Banana pith carbon Banana pith carbon Banana pith carbon Banana peel AC Banana peel Banana peel Banana peel AC Banana peel AC Activated Banana peel Inactivated Banana peel Banana pith Banana pith Banana pith Banana peel AC Banana peel AC Banana empty fruit bunch AC-H3PO4 Banana empty fruit bunch AC-KOH Banana empty fruit bunch AC-Untreated Banana leaves AC NaOH treated banana pseudostem fibers Banana leaf
Methylene blue Methylene blue Safranin Novacron blue FN-R Methylene blue Malachite green Methylene blue Methyl orange Methyl orange Methylene blue Rhodamine-B Congo red Methylene blue Methyl violet Malachite green Methylene blue Orange II Methylene blue Orange II Methylene blue Methylene blue Methylene blue Rhodamine-B Direct red Acid Brilliant blue Methylene blue Methyl red Methylene blue Methylene blue Methylene blue Methylene blue Methyl red Methylene blue
18.647 19.671 21.74 e 620.0 141.76 e 0.86 0.89 243.90 e e e e e 225 25 225 333 1263 0.15 0.124 e 5.92 4.42 454.54 400 76.13 71.06 70.63 48.01 e 109.89
5-100 mg/l 5-100 mg/l 5-40 mg/l e 1000 mg/l e 25 mg/l e e e e e e e e e e e e e e e e e e e e e e e e e 250 mg/l
3h 3h 90 min 20 min 24 h 120 min 2h 90 min 90 min e 24 h 24 h 24 h 24 h 24 h 150 min e e e e 120 min 120 min e e e e e e e e e 42.94 min e
20 C 20 C 20 C e 25 C 303 K e 30 C 30 C 30 C e e e e e 25 C 25 C 25 C 25 C 25 C e e e e e 22 C 22 C e e e e e 30 C
4e8 4e8 7.5 2.0 9.0 8.0 e 5.0 5.0 7.0 3.20 5.01 4.02 4.26 4.11 e e e e e 4.0 4.0 4.0 3.0 3.0 6.0 6.0 e e e e 2.08 4.0
e e e 90.0 e e 89 e e e 82.65 76.55 93.35 37.45 48.20 e e e e e 94 90 87 e e e e e e e e 98.98 e
Amel et al. (2012) Amel et al. (2012) de Sousa et al. (2014) Khaleque and Roy (2016) Hashem and Amin (2016) Bello et al. (2012) El-Maghraby and Taha (2014) Prachpreecha et al. (2016) Prachpreecha et al. (2016) Hameed et al. (2008) Kadirvelu et al. (2003) Kadirvelu et al. (2003) Kadirvelu et al. (2003) Kadirvelu et al. (2003) Kadirvelu et al. (2003) Kong et al. (2016a) Ma et al. (2015) Ma et al. (2015) Ma et al. (2015) Ma et al. (2015) Gautam and Khan (2016) Gautam and Khan (2016) Namasivayam et al. (1993) Namasivayam et al. (1998) Namasivayam et al. (1998) Nowicki et al. (2016) Nowicki et al. (2016) Sugumaran et al. (2012) Sugumaran et al. (2012) Sugumaran et al. (2012) Martín-Gonz alez et al. (2013) Yet and Rahim (2014) Krishni et al. (2014)
removal of pesticides (atrazine and ametryne) from river and municipal wastewater treatment plant samples. The 23 factorial design experiment was used to optimize sample volume (50 mL), adsorbent mass (3 g), and stirring time (40 min) for the removal of both pesticides (atrazine and ametryne). The isotherm data of atrazine and ametryne were followed multilayer adsorption isotherm (Freundlich) model with high regression coefficient values of 0.992 and 0.994, respectively. The Freundlich constant for sorption (Kf sor) values obtained for the synthetic solution of atrazine and ametryne with a concentration in the range of 0.100e0.500 mg/mL were 35.8 and 54.1 (mg/g).(mg/mL)-N that correspond to 59.80% and 75.30% removal efficiency. The removal efficiency of banana peel adsorbent against municipally treated water samples for atrazine and ametryne was found to be 93.80 and 95.20%, respectively. When the river water samples tested for the removal efficiency of banana peel adsorbent, the result not verified because of the presence of other chemical species in the river water samples that compete with the pesticides and occupied the active sites of banana peel adsorbent. Hence, the adsorption of atrazine and ametryne was found less compared to municipal wastewater and synthetic pesticide-polluted water. The comparison study of the adsorption and desorption of ametryne and atrazine onto banana peel adsorbent showed that ametryne have high adsorption and desorption capability. This study recommended that no chemical modifications on the banana peel surface or pH adjustment of pesticide solution required for maximum adsorption. The adsorption ability of chemically (ZnCl2) activated banana pith carbon against carbaryl (1-naphthyl-N-methylcarbamate) solution was investigated (Sathishkumar et al., 2008a). The adsorption results revealed that the removal was pH dependent; the maximum removal (qmax ¼ 45.90 mg/g) was observed at pH 11. The adsorption isotherm data were described by the Langmuir as well
as Freundlich isotherm models equally with high regression coefficient (R2 ¼ 0.99). The pseudo-first-order kinetic model gave a better prediction of the adsorption data against time for carbaryl onto activated carbon. Desorption was successfully done using acetone with elution efficiency of 99.80%. Banana peel adsorbent was used for the adsorption of metribuzin from water solution (Haq et al., 2015). The batch mode of the adsorption experiment was conducted to find the optimum values for contact time, pH, adsorbent dosage, temperature, and initial pesticide concentrations. The maximum adsorption capacity of banana peel dried powder (several times cleaned with water before use as adsorbent) was reported to be 167 mg/g at optimum pH 3.0, contact time 60 min, and adsorbent dosage 0.10 g. The kinetic sorption data of metribuzin was fitted to pseudo-second-order kinetic model with high regression coefficient (R2 ¼ 9803). Langmuir model better explained the isotherm data with the highest correlation. The increase in temperature during adsorption process ceased the adsorption of metribuzin onto banana peel powder. The thermodynamic study was implied that the adsorption of metribuzin was spontaneous (negative value of DG ) and exothermic (negative value of DH ) in nature. A summary of adsorption capacity of banana waste-based bio-sorbents for various pesticides has been shown in Table 3. 2.4. Removal of miscellaneous water-soluble organic compounds using banana waste derived adsorbents Contamination of aquatic systems by organic pollutants poses significant public and environmental health risks in various part of the world. These pollutants originate from textile, agrochemical, and pharmaceutical industries (Chaukura et al., 2016). Organic pollutants have long persistence in the environment. They are
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Table 3 Adsorption capacities of banana waste based biosorbent for the removal of pesticides. Adsorbent
Adsorbate
Charred banana peel Banana AC Banana peel Banana peel Banana stalk AC Banana stalk AC Banana stalk AC Banana pith AC Banana peel Banana peel Banana peel Banana peel
Atrazine Oxamyl Atrazine Ametryne Carbofuran 2,4-dichlorophenoxy Bentazon Carbaryl Metribuzin 2,4-dichlorophenoxy 2,4-dichlorophenoxy 2,4-dichlorophenoxy
Qm (mg/g) Conc. 14.0 434.78 e e 164 acetic acid 196.33 115.07 45.9 167 acetic acid 22.73 propanoic acid 33.26 butyric acid 21.27
1-150 mg/l e e e e e e 10 mg/l 40 mg/ml 7.5 mg/l 7.5 mg/l 7.5 mg/l
resistant to degradation and are bio-accumulative. Therefore, they easily enter in the tissues of the living organism and can enhance their concentration through the food chain. These organic pollutants are hazardous due their numerous after effects. Some organic pollutants cause mutagenic and carcinogenic to human as well as animal cells. Other effects of organic pollutants are dysfunction of kidney, liver, brain, reproductive system, and central nervous system in human bodies (Zhou et al., 2015). Hence due to this reason, their removal from the environment is of great importance. Banana waste derived bio-sorbents have been widely investigated for the adsorption of various types of organic pollutants in wastewater samples. Removal of PAHs (polycyclic aromatic hydrocarbons) such as Naphthalene (C10H8), Fluorene (C13H10), and Phenanthrene (C14H10) through banana peel activated carbon was investigated (Gupta and Gupta, 2016). The ideal adsorption parameters such as contact time, adsorbent dose, pH, and temperature were found for maximum removal of the PAHs by varying one parameter at a time. It was reported that contact time 60 min was equilibrium time for all three PAHs. The increase in adsorbent dose increased the removal efficiency, but for a fixed concentration of 20 mg/L of PAHs solution the adsorbent dosage 0.206 g/L was optimum for fluorene and phenanthrene and 0.333 g/L for naphthalene solution. Low pH was found favorable for adsorption of all three PAHs because at low pH of the solution the surface of the adsorbent was remained positively charged, which helps in electrostatic attraction between the adsorbent and negatively charged PAH adsorbate. At a fixed temperature, the adsorption isotherm data was followed the Langmuir isotherm model, and with the increase of temperature adsorption capacity of the banana peel activated carbon was rising against PAHs. At 20 C temperature and contact time 80 min, the maximum adsorption capacity of the adsorbent through Langmuir model was calculated to be 333.33, 285.70, and 217.39 mg/g for naphthalene, fluorene, and phenanthrene, respectively. The thermodynamic parameters indicated that the adsorption of PAH was spontaneous and endothermic. Desorption of PAH through the different composition of NaOH and ethanol were tried, and it was concluded that 1.0 M NaOH in 50% Ethanol was the most effective solvent for quantitative desorption of phenanthrene (95%), naphthalene (97%), and fluorene (95%) samples. The authors claimed that banana peel activated carbon was cheap, effective, eco-friendly, and readily available adsorbent. Kong et al. (2016b) prepared surfactant modified banana truck adsorbent and investigated their removal efficiency against an aqueous solution of benzene. The banana trunk was modified by using various types of surfactants such as cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl sulphate (SDS), poly(ethylene glycol)-block-poly(propylene glycol)block-poly(ethylene glycol) (Pluronic 123), and 4- (1,1,3,3tetramethylbutyl)phenyl-polyethylene glycol (Triton X-100). The
Contact Time Temp. pH e 3h e e e e e e 60 min 60 min 60 min 60 min
25 25 e e 30 30 30 30 e e e e
C C
C C C C
7.0e8.2 6.7 e e 7.0 3.5 3.5 11.0 3.0 7.0 7.0 7.0
% Removal Ref. 99 e 59.8 75.3 e e e e e e e e
Chaparadza and Hossenlopp (2012) Mohammad et al. (2015b) Silva et al. (2013) Silva et al. (2013) Salman and Hameed (2010) Salman et al. (2011) Salman et al. (2011) Sathishkumar et al. (2008a) Haq et al. (2015) Okumus¸ et al. (2015) Okumus¸ et al. (2015) Okumus¸ et al. (2015)
adsorption of benzene through banana trunk modified by Triton X100 was found independent of pH of the solution, but adsorption capacity increases with the increasing initial concentration of benzene, decreasing adsorbent dosage, and increasing temperature. It was observed that the TX100 modified banana trunk had maximum adsorption capacity (0.281 mol/g) against benzene. The benzene adsorption onto surfactant-modified banana trunk was thermodynamically non-spontaneous, and with the rise of temperature, the adsorption was found to be increasing. The adsorption isotherm data followed the Langmuir isotherm model for all surface modified banana trunk adsorbent. The increment of adsorption with time was followed the pseudo-second kinetic model, and the mechanism of adsorption was explained through film diffusion, external mass transfer, and intraparticle diffusion. The surfactantmodified banana trunk adsorbents have incorporated the new surface functional groups that enhance the benzene adsorption capacity up to 397% as compared to the untreated banana trunk. The interactions between the benzene molecules and active adsorbent sites were electrostatic in nature due to the presence of charged species. Microwave-assisted char (MBPC) was synthesized from the raw banana peel (RBP) to investigate the adsorption performance of it against citric acid from aqueous solution (Pathak and Mandavgane, 2015). Due to microwave treatment, the surface area increased from 0.65 m2/g to 22.37 m2/g, which was 34.41 times more than raw banana peel. The FTIR results showed the interactions between the hydroxyl and amine groups during the adsorption process. The concentration of basic sites (4.9 mmol/g) was found to be higher than acidic sites (0.75 mmol/g). The adsorption capacities for citric acid removal on MBPC and RBP were 147.06 mg/g and 76.13 mg/g at pH 4.75 and temperature 50 C. The equilibrium was achieved in about 240 and 330 min for adsorption of citric acid onto MBPC and RBP, respectively. The adsorption of citric acid onto RBP and MBPC were followed the pseudo-second-order kinetics model. Elovich model confirmed that the removal of citric acid onto MBPC was through chemisorption. The DG value for adsorption of citric acid onto RBP and MBPC were negative, which suggests that the adsorption was spontaneous. The decrease in DG with an increase in temperature indicated that the higher temperature favors the adsorption. The DH value for citric acid adsorption was found positive, indicated that surface interaction was heat consuming in nature (endothermic). Pathak et al. (2015) reported the scavenging behavior of banana peel as adsorbent against an aqueous solution of benzoic acid (BA) and salicylic acid (SA). The pH and temperature were a major driving force in adsorption at pH 3.68 for BA and 3.3 for SA and temperature 323 K for maximum adsorption capacities of benzoic acid (6.62 mg/g) and salicylic acid (9.80 mg/g). It was observed that with the rise of temperature adsorption capacity was found to be increasing, shows endothermic (positive DHo) nature of
T. Ahmad, M. Danish / Journal of Environmental Management 206 (2018) 330e348
adsorption for both the adsorbates. Irrespective of the adsorbate the isotherm data was followed Langmuir isotherm model. The kinetics of adsorption for both the adsorbate was found to be different, the BA followed the pseudo-second-order kinetic model, whereas, SA followed the pseudo-first-order kinetic model. The negative standard Gibbs free energy change (DGo) for both the adsorbate indicated that adsorption was spontaneous. After characterization of dried banana peel (BP) adsorbent, it was observed that it contains the basic functional group (4.90 mmol/g) more than the acidic functional group's sites (0.75 mmol/g). Although, BET surface area of BP was low (0.65 m2/g), but substantial adsorption of BA and SA onto banana peel adsorbent was reasoned based on the FTIR results that show the presence of amine and hydroxyl groups. The adsorption mechanism was explained through ion exchange and electrostatic force of attraction between the positively charged banana peel surface and negatively charged benzoate and succinate ions. Ingole et al. (2017) reported the removal efficiency of banana peels activated carbon (BPAC) against phenol. The percentage removal and adsorption capacity of BPAC were found to be decreased from 83% and 6.98 mg/g to 60% and 48.58 mg/g when the initial concentration increased from 50 ppm to 500 ppm, respectively. The adsorbate solution pH 6.0 was found to be optimum for the maximum phenol removal. The phenol adsorption was followed the pseudo-second-order kinetic model with R2 closure to unity. The isotherm data was applied to Toth and Redlich-Peterson models; both models have described the adsorption behavior of BPAC against phenol. The effect of temperature variation on adsorption was observed, it was found that the increase in temperature decreased the phenol adsorption onto BPAC, results are interpreted with spontaneous and exothermic adsorption behavior. Ali and Saeed (2015) also investigated the adsorption of phenol with chemically modified banana peels. The authors compared the adsorption capacity of five adsorbents, untreated banana peels (UTBPs), acid hydrolyzed banana peels (AcBPs), bleached banana peels (BBPs), alkali hydrolyzed banana peels (AlBPs), and grafted banana peels (GBPs). The results revealed that chemically treated banana peel adsorbent have adsorption capacity much larger than untreated banana peel adsorbent. The chemical activation removes the viscous compounds like lignin and pectin, and expose the cellulose to interact with the adsorbate molecules. The chemical activation also incorporates arylonitrile monomer to the cellulosic framework, which also improved its interaction with sorbate molecules. The phenol adsorption capacity through prepared adsorbents decreased in following order: GBPs > AlBPs> AcBPs > BBPs > UTBPs. The adsorption data were best described by second-order kinetic model and monolayer (Langmuir) adsorption isotherm mechanism. The adsorption of phenol at different temperatures showed that adsorption decreasing with increasing temperature, this indicated exothermic nature of adsorption and negative standard Gibbs free energy change (DG ) was the sign of spontaneous behavior. Achak et al. (2009) utilized banana peel as low-cost bio-adsorbent for the removal of phenolic compounds from wastewater originating from olive mills. The adsorption of phenolic compounds onto banana peel adsorbent was found to be quick and equilibrium achieved within 3 h of contact time. The solution pH above neutral (pH > 7.0) increased the adsorption, whereas, acidic solution (pH < 7.0) was found suitable for desorption of phenolic compounds. Higher adsorbent dosage (30 g/L) increased adsorption rates, and the maximum adsorption capacity of banana peel was observed to be 689 mg/g against phenolic compounds. The multilayer (Freundlich isotherm) adsorption was better described the phenolic compounds adsorption onto banana peel bio adsorbent. The pseudosecond-order kinetic model was followed by the adsorption
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capacity vs. time data. A nutshell information of adsorption capacities of various banana waste derived sorbents against commonly found organic pollutants have been shown in Table 4. 2.5. Removal of water-soluble inorganic anions using banana waste derived adsorbents Inorganic pollutants widely distributed in the wastewater due to the frequent use of inorganic salts in the industry as well as in domestic day to day activities. Mondal (2017) experimented on the fluoride polluted underground water cleaning through Natural banana (Musa acuminate) peel (NBP) adsorbent. Before adsorption experiments, characterization of NBP adsorbent was conducted through SEM, FTIR, and point of zero charges. The SEM images were shown highly rough irregular surface, FTIR spectra showing major peaks for -OH, -C¼O, and -N-H stretching peak, and pHzpc was observed at 5.63. The adsorption capacity of natural banana peel sorbent was found to be increasing at fluoride solution pH below 5.63, and pH 4.0 was reported to be optimum pH for maximum removal percent (94%) of fluoride ions through NBP adsorbent. The equilibrium of fluoride ion adsorption was achieved within 60 min, and kinetics of the adsorption was expressed through pseudo-second-order model and Bahangam's equation. The applicability of Bahangams's model shows that the fluoride adsorption onto NBP was pore diffusion control. The isotherm data was well fitted to D-R isotherm (R2 ¼ 0.995) model. The temperature effect on the adsorption of fluoride ion was inversely proportional, as the temperature increased the adsorption decreased, this effect suggested that the fluoride adsorption onto NBP was spontaneous (-ve DG ) and exothermic (-ve DH ) in nature. In this study, they also 3 2 observed the effect of co-ions (CO2 3 , PO4 , SO4 , NO3 , and Cl ) presence during adsorption of fluoride ions. The authors reported following order of interference of co-ions: 3 2 CO2 3 > PO4 > SO4 > NO3 > Cl . The carbonate ions strongly interfere in the adsorption of fluoride, due to the preferential binding sites of carbonate ions were present on the surface of NBP. Bhaumik and Mondal (2016) optimized the adsorption of aqueous fluoride ions onto modified banana peel dust through response surface method approach. Three types of banana peel dust were prepared untreated banana peel dust (BPD-1), modified banana peel dust (BPD-2), and calcium impregnated banana peel dust (BPD-3). The chemically modified banana peel adsorbents have improved surface area and surface chemical properties. The pHzpc (points of zero charge) of each chemically modified adsorbent such as BPD-1, BPD-2, and BPD-3 were experimentally determined and reported to be 6.2, 8.1 and 8.2, respectively. The Box-Behnken model of response surface methodology approach was used to explore and optimize the key independent factors on fluoride removal. The statistical data analysis was shown that a secondorder polynomial model was properly fit into the experimental data with coefficient of determination (R2) value of 0.9890, 0.9873 and 0.9938 for BPD-1, BPD-2, and BPD-3, respectively, and with probability> F value of
