An Efficient and Regenerable Quaternary Starch for Removal of

Article pubs.acs.org/IECR

An Efficient and Regenerable Quaternary Starch for Removal of Nitrate from Aqueous Solutions Kalpana Chauhan,*,† Jasvinder Kaur,† Prem Singh,† Poonam Sharma,‡ Praveen Sharma,§ and Ghanshyam S. Chauhan∥ †

School of Chemistry, Shoolini University, Solan 173229, India Department of Bioinformatics/Biotechnology and Pharmacy, Jaypee University of Information Technology, Solan, India § Himachal Pradesh State Pollution Control Board, Shimla 171009, India ∥ Department of Chemistry, Himachal Pradesh University, Shimla 171005, India ‡

ABSTRACT: This paper presents a study of NO3− ions sorption from an aqueous solution using quaternary starch derivatives. For this, the derivatization was carried out by an improvised method for the synthesis of a gemini-like structure, which is unique and has two quaternary ammonium functionality per anhydroglucose units of starch. Mohr’s method was used to characterize the synthesized bis-quaternary starch as chloride ion content, and the results supported a chloride content of 13.5−14.4% with the total ion exchange capacity of 3.8−4.2 mequiv/g. A series of batch experiments were conducted to examine the effects of structure, contact time, concentration, pH, and effect of co-ions on the sorption of NO3−. The results showed an increase in sorption capacity with an increase in the concentration of NO3−, while the presence of competing anions such as PO43−, HCO3−, and SO42− showed marginal effect on the NO3− sorption capacity. The increase in pH from 4.0 to 6.5 also effected the NO3− sorption process marginally. Moreover, the quaternary starch exhibited 78.5% efficiency even after the eighth sorption− desorption cycle. The kinetic and thermodynamic adsorptions of NO3− ions from the aqueous solutions were also investigated for the synthesized quaternary starch derivative. The adsorption kinetics data were best described by the pseudo-second-order rate equation. The equilibrium data agreed well with the Langmuir model. The maximum capacity for quaternary starch can be deduced from the obtained correlation coefficients and was calculated at ≈205 mg/g in the isotherm model, which is preferential to the earlier reported commercialized Purolite technology. In conclusion, the bis-quaternary starch structure is successfully synthesized in uniform and high modification and shows significant potential for removal of NO3− ions from aqueous solution.

1. INTRODUCTION The NO3− concentration in ground and surface waters is increasing daily in many parts of the world including India.1 Recently, the Central Ground Water Board (CGWB), Ministry of Water Resources, Government of India, reported contamination of groundwater by NO3− up to 105 mg/L in 14 districts in 9 Indian states.2 The World Health Organization (WHO) has set a limit of 50 mg/L of NO3− (11.3 mg/L NO3−N) in drinking water,3 whereas the Bureau of Indian Standards4 set a current maximum allowable concentration of 45 mg/L of NO3− (10.2 mg/L NO3−N). The worldwide intensive use of fertilizers for agriculture to meet the growing need of society has increased the amount of reactive nitrogen in terrestrial and aquatic ecosystems.5,6 Besides nitrogenous fertilizers, various anthropogenic sources like municipal waste, animal waste, septic tanks, landfills, industrial processes, and soil organic matter are also the major sources of NO3− contamination of groundwater.7 Nitrates are highly soluble salts in water and can move easily through soil into the drinking water supply.8 The majority of the global population depends on surface water for drinking purposes. In rural areas, there are few alternative sources of drinking water. Nitrogen is necessary for all living things, but a high concentration of NO3− in drinking water has potential detrimental effects to health, particularly for infants and pregnant women. Excess consumption of highly NO3−© XXXX American Chemical Society

contaminated water is reported to cause various health related problems such as methemoglobinemia, stomach cancer (due to nitrosamine or nitrosamide),9 increased infant mortality, central nervous system birth defects, non-Hodgkin’s lymphoma, initiation of kidney diseases, oral cancer, colon cancer, rectum and other gastrointestinal cancers, and Alzheimer’s disease.10 Nitrate, being a highly soluble salt in water, is difficult to remove above the maximum admissible concentration and is a technical challenge. As a result, the research on processes of removing NO3− from water is gaining importance. Several NO3− removal technologies have been tested such as reverse osmosis,11 biological denitrification,12 catalytic reduction,13 ion exchange process,14 electrodialysis,15 and bioelectrochemical process.16 Among the various chemical, biological, and physical treatments used for NO3− removal, adsorption or ion exchange technology is attracting global interest and is considered a better option due to its ease of operation, convenience, simplicity of design,17−22 effectiveness, recovery, and relatively low cost.23,24 In addition, the groundwater is dynamic in nature and has some common competing anions such as sulfate, phosphate, bicarbonate, and chloride; their presence would Received: October 18, 2015 Revised: January 30, 2016 Accepted: February 6, 2016

A

DOI: 10.1021/acs.iecr.5b03923 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research

Figure 1. Proposed structure for bis-quaternary ammonium starch (gemini-like structure).

significantly influence NO3− removal with the exchangeable sites in ion exchange resins. Therefore, there is need for further study to find resins selective for nitrate over other ions. Several ion exchange resins are developed for the denitrification of drinking water, but an amine-functionalized membrane is reported25−27 that is capable of removing the NO3− pollutant. Also, the ammonium-type anion exchange resin with Cl− as the exchangeable group is affirmed as being extra proficient and selective for removing NO3− from different aqueous media.28,29 The selectivity could be further increased by variation of the alkyl unit from the trimethyl to triethyl of the carbon side chains surrounding the nitrogen in the ammonium functional group of resins.30 Recently, styrene−divinylbenzene copolymer resins prepared in various chain lengths on the exchangeable sites by chloromethylation and quaternarization are proved with more preferable absorption toward NO3− than commercial D201 and Purolite A300 in the presence of competing ions.31 The higher selectivity is possibly due to longer alkyl chains at the exchange sites of the styrene−divinylbenzene copolymer resin. However, there are some major problems with commercially available anion exchange resins, such as, high processing cost, nongreen functionalization with carcinogenic reagents, and nonbiodegradability, thus limiting their application on large scales.32,33 Consequently, waste biomass is the best economical choice to prevent usage of expensive exhaustible petroleum as raw materials and to avoid water pollution by hazardous chemicals. According to literature, it is well known that biomass is used as an interesting alternative for solid carbon sources to achieve denitrification.34,35 Moreover, the idea of converting biomass into ion exchangers with amine functionalization has also been explored in finding inexpensive, effective, and environmentally friendly anion exchangers from agricultural byproducts.36−40 The modification is achieved that results in an alternative anion exchanger with comparable capacity to commercial resins for NO3− removal from water.38 In biopolymer, starch is one of the most important renewable resources because of its biodegradability, easy availability, and low cost. The chemical modification of starch in ionic structure offers an interesting alternative to petrochemical resources by developing new products with exceptional performance.41−47 But, the reagents of reactions to convert starch as ion exchangers are nongreen and involve the use of genotoxic carcinogens, such as, epichlorhyderin, glycidyltrimethylammonium chloride, etc. Therefore, the main goal of this research is to prepare green ion exchangers with a high degree of ionic modification for extraordinary removal capability of NO3− ions. The authors reported a new process of starch functionalization in a bisquaternary ammonium structure (gemini structure), and the

detailed procedure for the synthesis has been reported in our earlier study.48 There is no report to the best of authors knowledge for the synthesis of biopolymers with gemini-like structures, which are explored for NO3− sorption. The density and uniformity of functional groups anchored on the backbone polysaccharide are important criteria, which enhance anion partitioning between the functionalized biopolymer and the solution phase. The effects of structure, initial concentration of NO3−, pH, and competitive ions on NO3− removal performance were investigated. The synthesized products were also studied for their environmental impact or biodegradation studies in native, quaternized, and NO3− loaded form to define the green prospective of the synthesized products. Kinetic and equilibrium studies for the removal of NO3− from aqueous solutions were also conducted to conclude the maximum adsorption capacity for the synthesized quaternary starch.

2. EXPERIMENTAL SECTION 2.1. Materials. Starch (Fisher Scientific, Mumbai, India), glutaraldehyde, and amylase were obtained from HiMedia Laboratories, and all other chemicals were of analytical grade and were used as received. 2.2. Preparation of Quaternary Ammonium-Functionalized Starch. Cross-linked quaternary starch and non-crosslinked quaternary starch were prepared by following an earlier reported procedure.48 In the process of quaternization, initially starch was modified by oxidation reaction to obtain dialdehyde starch. The dialdehyde starch was then functionalized by amination and quaternization reactions in amine and bisquaternary structures, respectively. Amine starch was also crosslinked separately with glutaraldehyde (GA), and the obtained cross-linked starch was functionalized by quaternization reactions. The synthesized products are extensively characterized for reproducibility of results and are referred to abbreviations throughout the paper, i.e., SQA, SAM-Cl-GA, and SQA-Cl-GA for quaternary starch, cross-linked amine starch, and cross-linked quaternary starch, respectively. In these terms S stands for starch, SAM for amine starch, Cl for cross-linker, and SQA for quaternary starch. The starch structure unit with a bisquaternary ammonium unit is represented in Figure 1. 2.3. Characterization. FTIR spectra were performed to evaluate the successful completion of the quaternization reaction on a PerkinElmer spectrophotometer using KBr pellets. The synthesized quaternary starch products were also characterized for magnitude of quaternization by ion exchange capacity measurements. Ion exchange capacity depends on the presence of a number of ion exchange groups that exist in the quaternary structure and can be measured by the titration method. This method determines the chloride ion concenB


Article


where qe and qt are the amount of NO3− adsorbed at equilibrium and at time t (mg/g), respectively. The adsorption rate constant k1 (min−1) can be calculated from the slope of the linear plot of log (qe − qt) against t. The sorption data was further treated by the pseudo-second-order kinetic model. The pseudo-second-order kinetic-model is expressed as52

tration of the sample solution and blank by titrating it against 0.1 M silver nitrate solution using a chromate indicator.49 The chloride ion concentration was calculated as follows: %concentration =

(V1 − V0) × N × 35.5 × 100 W × 1000

t 1 t = + 2 qt q k 2qe e

where V1 and V0 are volume of AgNO3 used by the sample solution and blank set, respectively. N is normality of the AgNO3 solution, and W is weight of the sample taken (g). 2.4. Adsorption Experiments of Quaternary-Functionalized Starch. A sorption study was carried out by taking 0.1 g of starch derivatives in 50 mL of a standard NO3− ion solution. The kinetics of the adsorption was determined by analyzing uptake of the NO3− ions from the aqueous solution with time. For detection, 1.0 mL of the of supernatant solution sample was withdrawn to determine the residual concentrations in the effluent solution at definite intervals of time, i.e., 30, 60, 120, 180, 240, 300, 480, and 1440 min. The effect of various parameters, such as pH (4.5, 6.5, 7.5 and 9.0), initial NO3− concentration (10, 50, 100, 250, 500, and 1000 ppm), and presence of competitive ions of sulfate, bicarbonate, and phosphate (100 and 500 ppm), was investigated with contact time. Regeneration of SQA-Cl-GA was achieved by using 0.025 M NaCl for 4 h. The regenerated product was washed thoroughly with double distilled water to remove free chloride ions and was then dried at room temperature. The sorption− desorption cycles were carried out eight times. All experiments were carried out in triplicate, and the average of the three observations was taken and reported. The colorimetric technique (UV−visible spectrophotometer, Systronics 2205) is used to quantify the extent of NO3− removal capacity of the synthesized starch derivatives at 220 nm.50 The color reaction involves the reaction of rejected NO3− ions from the sorption set and 0.1 N HCl (0.1 mL) as a color developing agent in a total of 5 mL of solution. The unknown concentration of the rejected filtrate was detected by using a standard curve, which was generated by taking 10 standard concentrations. The results of the adsorption were calculated by using the following equations:

where k2 (g/mg min) is the equilibrium rate constant of the pseudo-second-order model. The values of k2 can be determined from the intercept of the graph plotted between t/qt against t. The insight for the removal mechanism of the NO3− sorption can be concluded from the Weber−Morris model. The Weber−Morris model is expressed by the following equation:53 qt = K p t1/2 + C

where Kp is the intraparticle diffusion rate constant (mg g−1 min1/2) and is obtained from the slope. In order to test the existence of intraparticle diffusion in the adsorption process, the amount of NO3− adsorbed qt at any time t (mg/g) was plotted as a function of square root of time (t1/2). The adsorption data was also analyzed using the Elovich equation, which has the following linear form:54 qt = (1/β )ln(αβ ) + (1/β )ln t

where α is the initial sorption rate constant (mmol/g min), and the parameter β is related to the extent of surface coverage and activation energy for chemisorption (g/mmol). 2.6. Adsorption Isotherms. The study of the adsorption isotherms allow the accurate capacity estimation of material in adsorption. The most common isotherms applied in the solid/ liquid systems are the Langmuir and Freundlich equilibrium isotherms. The data obtained in the experiment are tested with two isotherms to successfully represent the sorption behavior of the NO3− ion from solution to the quaternized product phase. The Langmuir isotherm is the simplest of all mechanistic models. The Langmuir equation correlates the amount of adsorbate adsorbed with the equilibrium aqueous concentration when the whole surface of the adsorbent is completely covered by a monolayer of the adsorbate. Further adsorption is not possible, and this indicates a saturation of adsorbent. The linear transformation of the Langmuir equation55 is given as

Percent uptake (Pu) Amount of anions sorbed = × 100 Total ions in the feed solution Adsorption capacity (Q , mg/g) =

(C0 − Ct ) ×V M

ce/qe = 1/KLqm + ce/qm

where ce is equilibrium NO3− concentration in solution (mg/ L), qe is amount of NO3− adsorbed at equillbruim (mg/g), qm (mg/g) is the measure of adsorption capacity under the experimental conditions, and KL is the constant related to the energy of adsorption (L/mg). In order to predict the efficiency of the adsorption process, a dimensionless constant separation factor, RL, was used to indicate the nature of adsorption56, according to following equation:

where Q is the amount of NO3− ions adsorbed onto the product (mg/g), V is the volume of aqueous phase (L), M is the weight of polymer (g), C 0 and C t (mg/L) are concentrations of ions in the feed solution and aqueous phase after treatment for a certain period of time t, respectively. 2.5. Adsorption Kinetics of NO3− Removal. In order to examine the order of the adsorption process, several kinetic models were used to test the experimental data. The kinetic data were fitted by reaction-based models, namely, pseudo-firstorder, pseudo-second-order, intraparticle diffusion, and Elovich equation. The linear equation for the first-order rate expression is given by following expression:51 log(qe − qt ) = log qe −

RL = 1/(1 + bC0)

where b is the Langmuir constant, and C0 is initial NO3− concentration. The value of RL = 0 indicates that the isotherm is irreversible; otherwise, the isotherm is reversible. For 0 < RL < 1, the isotherm is favorable, while RL > 1 shows unfavorable isotherm.

k1 t 2.303 C


Article


Figure 2. FTIR spectrum of SQA-Cl-GA.

spectrophotometer. Evidence that N-alkylation supports the formation of SQA-Cl-GA is shown in Figure 2. The peak at 1382 cm−1 due to CH3 bending is ascribed to the successful derivatization of starch in the quaternary ammonium structure. Furthermore, the increase in intensity of the broad peak at ≈2154 cm−1 (N−CH3 stretching) is also accountable for the intense and uniform N-alkylation in SQA-Cl-GA. Cross-linked quaternary starch is also characterized for degree of quaternization by precipitation titration. 60 The results supported a degree of quaternization of 62%−68%. The resultant starch polymers have bis-quaternary ammonium groups (active sites) with exchangeable chloride, which is expected to be an efficient sorbent in the NO3− ion uptake. Since the main contribution to the NO3− uptake is by ion exchange, the high extent of quaternization is important for potential applications. Mohr’s method was also used to determine chloride ion content in synthesized SQA-Cl-GA, and the results supported a chloride content of 13.5 ± 1.0% with a total ion exchange capacity of 3.8−4.2 mequiv/g. 3.1. Nitrate Sorption. 3.1.1. Effect of Time. Biomass has already been proved capable iof NO3− sorption in the literature.38,61 In this study, starch quaternary derivatives, i.e., SQA and SQA-Cl-GA, were evaluated for NO3− immobilization with contact time up to 24 h to achieve equilibrium (Figure 3). The results show an initial rapid increase in adsorption from 32% to 75.6% and 35% to 84.6% for SQA and SQA-Cl-GA, respectively, at 360 min.38 There is no appreciable change in percent uptake of NO3− ions after 360 min. The more preferential results of SQA-Cl-GA are accounted by matrix opening due to incorporation of spacer groups between adjacent polymeric chains, which results in greater influx of NO3− ions in the gel phase to interact with the otherwise inaccessible quaternary sites in the bulk of an anionic exchanger. An insignificant decrease (only 1−2%) in the removal rate with time after attaining equilibrium may be due to the fact that initially all the quaternary ammonium groups contain Cl−, which are exchanged by NO3− ions. But after attaining equilibrium, this exchange might be equally possible

The Freundlich equation is also used for determining the applicability of heterogeneous surface energy in the adsorption process. The linear form of the Freundlich equation is represented as57 log qe = log K f + 1/n log Ce

where qe is the amount adsorbed per unit mass of adsorbent (mg/g), Ce is the equilibrium adsorbate concentration in solution, Kf and n are the Freundlich constant related to the adsorption capacity and adsorption intensity, respectively. 2.7. Biodegradation Studies. The biodegradation study was assessed via colorimetric analysis using a 3,5-dinitosalicylic acid (DNSA) reagent.58 For this, 0.1 g of starch/quaternary starch/NO3− -loaded quaternary starch was taken in buffered solution of pH 7.4 (20 mL). Then 1.0 mg of amylase was added as the biocatalyst for biodegradation. A control was also kept in parallel in which no amylase was taken. These were incubated for definite intervals of time at 35 °C for degradation characterization. The DNSA reagent was added to theses sets, and these were kept in a boiling water bath for 10 min for color development. The solution was cooled to room temperature and then centrifuged to allow the solid to settle. The optical density (OD) of the remaining fluid was recorded on a UV−vis spectrophotometer (UV−visible spectrophotometer, Systronics 2205) at 540 nM by setting it to zero OD by blank set. From the observed OD values, enzyme activity was calculated.59 The degradation characterization was also confirmed by %weight loss at the end of the degradation experiment (48 h). The samples were removed and dried for the calculation of %weight loss.

3. RESULTS AND DISCUSSION Starch-based derivatives were synthesized as per our earlier proposed process and characterized for reproducibility of the results.48 The confirmation for the synthesis of SQA-Cl-GA was performed with FTIR and titrimetry. The FTIR spectrum of cross-liked starch in a quaternary state was recorded in the range of 4000−500 cm −1 in KBr on a PerkinElmer D


Article


obtained are presented in graphical form in Figures 4a and b, which clearly depict the effect of initial feed concentrations of NO3− on removal capacity of SQA and SQA-Cl-GA with time, respectively. In general, the NO3− removal efficiency from the aqueous solution increases with an increase in the initial NO3− concentration. It is evident from the graphs that maximal percent uptake increases from 58.9% to 81.8% for SQA and 61.8% to 89% for SQA-Cl-GA with the increase in the initial concentration from 10 to 1000 ppm. The maximum uptake is attained within 360 min and then leveled off toward the equilibrium adsorption capacity. The higher uptake of NO3 − with concentration may be due to the availability of more quaternary sites on the surface of anionic exchangers. In general, an increase in concentration of the salt solution causes a decrease in hydrophilicity of the adsorbent, which increases their permeation for enhanced sorption with concentration.62 From the graphs, it is clear that there is a marginal increase in percent uptake of NO3− beyond 500 ppm; this may be due to nonavailability of the quaternary ammonium group with exchangeable chloride ions at higher initial NO3− concentrations. The competition between increasing Cl− ion and NO3− ions for the exchangeable quaternary sites on starch might be responsible for the decrease in NO3− uptake at higher concentration.63 3.1.3. Effect of pH. The pH of solution has importance and a limiting effect on the ion adsorption processes. Therefore, the exchange of NO3− in SQA and SQA-Cl-GA was examined at different pH values (4.5, 6.5, 7.5, and 9.0) with 500 ppm concentration at 30 °C (Figure 5). It is apparent that the NO3− sorption capacity increases slightly as the pH increases from 4.5 to 6.5, and then the sorption capacity marginally decreases in alkaline medium from pH 7.5 to 9.0. On pH variation, the maximum NO3− exchange is observed at pH 6.5. SQA has a

Figure 3. Effect of structure on percent uptake of NO3− with time at 30 °C and 500 ppm.

for NO3− from the quaternary exchangeable positions with Cl− in solution (now present in high concentration in solution). Moreover, the adsorbent concentration gradient was also high at the start of the reaction. Later the rate of NO3− uptake by adsorbent is also reported with a marginal decrease due to the decrease in number of quaternary sites as well as NO3− concentration. 3.1.2. Effect of Concentration. To investigate the effect of structure and initial NO3− concentration on NO3− removal, the study was performed for SQA and SQA-Cl-GA at 30 °C. The initial concentration of the NO3− solution was varied from 10 to 1000 ppm with adsorbent dosage of 0.1 g. The results

Figure 4. Percent uptake of NO3− with concentration for (a) SQA and (b) SQA-Cl-GA at 30 °C. E


Article


products. The accelerated decrease in NO3− removal rates at pH 9.0 can be attributed to the competition between the OH− groups and NO3− anions for the active modified quaternary sites.64,65 3.1.4. Effect of Competitive Anions. Natural water has a dynamic nature and has some ions dissolved naturally. However, these competing ions for active sites on the adsorbent would interfere with the process of nitrate removal and would result in lower efficiency. Thus, it is crucial to determine the selectivity of resin for practical application in water considering its dynamic nature. The presence of competitive ions, such as phosphate, sulfate, or bicarbonate, is the most important interference in the removal process of NO3−, which reduces the ion exchanger capacity due to the displacement of the NO3− anions with the competitive anions. The results are shown in Figure 6a−c for SQA-Cl-GA. The results of the experiments show that the percentage of NO3− removal has increased with an increase in contact time. But no significant influence on NO3− removal is observed in the presence of competitive ions at 100 ppm concentration. It is clear from the figures that the presence of these anions reduced the maximum adsorption of NO3− from 84.8% to 81% or 81.3% for phosphate or bicarbonate and to 72% for sulfate. Bicarbonate has the least impact on the removal of NO3− compared to sulfate and phosphate. The order of the reduction of NO3− adsorption is sulfate > phosphate ≥ bicarbonate. The selectivity of SQA-Cl-GA for nitrate was also evaluated with increased concentration of competitive ions (500 ppm), and nitrate concentration was kept constant (500 mg/L). Figure 6 shows that the NO3− percent sorption decreases with an increased concentration of competitive ions as expected, but this is almost negligible in comparison to the increased ratio of NO3− to competitive ions in solution. In the presence of excess competitive ions (500 mg/L), the NO3− maximum removal efficiency decreases from 84.8% to 73% or 71% or 67% for phosphate or bicarbonate or sulfate, respectively. The results suggested that the order of the reduction of NO3− adsorption is sulfate > bicarbonate > phosphate and appears to be dependent on the initial concentration of competitive ions. In order to test the broaden application range of the SQA-ClGA exchanger, selectivity has also been tested in multi-anion

Figure 5. Percent uptake and retention capacity of NO3− with pH (concentration = 500 ppm, temperature = 30 °C, contact time = 4 h).

maximum percent uptake 75.6%, which decreases gradually to 68.6% at pH 9.0. A similar trend is observed for SQA-Cl-GA with maximum percent uptake of 85.2% at pH 6.5, which decreases to 78.0% at alkaline pH. The results are also reported with a maximum adsorption capacity of 189 and 213 mg/g for SQA and SQA-Cl-GA, respectively. At acidic pH, the results are comparable and can be accounted for by a highly protonated adsorbent surface, which is capable of attracting anionic species NO3− by electrostatic forces. Conversely, in higher pH values, the solution donates more hydroxide (OH−) groups, and the presence of a large amount of OH− ions in the aqueous solution starts competing with NO3− for binding with the quaternary ammonium group with exchangeable Cl− ion sites and results in lower sorption of NO3−. Similar results are reported that the maximum removal rate was obtained for some adsorbents with positive surface charges in the pH range of 5.0−8.0,63 and after a further increase in pH values, the NO3− adsorption rates started decreasing for biopolymeric quaternary

Figure 6. Effect of competitive ions on percent uptake of NO3− with time for SQA-Cl-GA: (a) sulfate, (b) phosphate, and (c) bicarbonate. F


Article

Industrial & Engineering Chemistry Research coexistence systems. Figure 7 shows the effects of sulfate, bicarbonate, and phosphate on NO3− adsorption by the SQA-Cl-

Figure 8. Retained sorption efficiency of SQA-Cl-GA for NO3− at various cycles (concentration = 500 ppm, temperature = 30 °C, contact time = 4 h, pH 6.5).

Figure 7. Effect of competitive ions as multi-anion coexistence systems on percent uptake of NO3− with time for SQA-Cl-GA.

repeatedly. The regeneration results are also supported by Q values, and the details are presented in Figure 8. In conclusion, this study supports preferential results for NO3−, even in competition with other ions and with the dynamic nature of water. One possible explanation for the results is that the synthesized bis-quaternary starch is a uniform structure with a high degree of quaternization. That is why synthesized exchangers are competing with the commercialized technology of Purolite International, Ltd.29 Purolite technology has two anion exchange resins, Purolite A520E and Purolite A300, for nitrate removal from aqueous solutions. Purolite 300A is a nonselective gel anion exchange resin used in all types of demineralization processes. Purolite A520E resin is functionalized with triethylamine exchange sites and is specially designed for the selective removal of nitrates from water.30,65 3.2. Kinetic Study. The mechanism of adsorption depends on the physical and/or chemical properties of the adsorbent and on the mass transfer process as well. Several kinetic models were used to predict the kinetics and mechanism of NO3− ion sorption by synthesized quaternary starch. The kinetic data for the adsorption of NO3− are based on curve fitting and are summarized for the pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich equation models in Table 1. It has been found that the resultant plots of pseudo-first-order, intraparticle diffusion, and Elovich equation kinetic models for NO3− sorption deviate from linearity with slightly lower correlation coefficient values in comparison to the pseudosecond-order model. Therefore, the best suitability of the kinetic data corresponds to the pseudo-second-order model32 for the entire adsorption period, which is also supported by least values of rate constant (g/mg min) for the pseudo-secondorder models ranging from ∼0.0001 to 0.056 as compared to other kinetic models. This indicates that the pseudo-secondorder model, which is based on the assumption that the ratelimiting step may be chemical sorption or chemisorption involving electrostatic attraction between quaternary ammonium group and NO3−, provides the best correlation of the data. Also the correlation coefficient, R2, has highest value

GA exchanger. The competing anions result in a marginal decrease in the maximal adsorption capacity of NO3− from 84.8% for the nitrate system to 71.7% for multi-anion coexistence systems onto SQA-Cl-GA adsorbents. Interestingly, the extent of competing anions influencing the equilibrium capacity of the SQA-Cl-GA exchanger is almost similar to the binary coexistence system. In conclusion, the results indicate that SQA-Cl-GA has higher selectivity toward NO3− removal, and other anions hardly affect NO3− adsorption of the adsorbent. Hence, it is the most effective adsorbent in the removal of NO3− content in water. These observations can be justified as the quaternary ions exchanger is more hydrophobic and therefore selective in adsorbing NO3−, which has less hydration energy than competitive ions.29,30,66,67 The same results are noted by Johir et al.68 for Purolite A520E, which has a strong selectivity for nitrate due to its hydrophobicity. It is well known that the quaternary resins with longer triethyl functional groups in quaternary ammonium group are hydrophobic, which would change the interfacial interactions between anions and quaternary resin by reducing hydration energy.30 3.1.5. Regeneration Studies. Recovery of the adsorbed anions and repeated usability of the exchanger are important aspects for technological applications of treatment of industrial effluent. This makes the process cost efficient. The regenerability of the NO3−-loaded SQA-Cl-GA was studied using 0.025 M NaCl for 4 h.64 The results reveal 100% of actual desorption efficiency in SQA-Cl-GA for NO3−. Therefore, 4 h is fixed as the optimum contact time for regeneration. The regeneration studies were conducted up to the eighth cycle, and even then, 92% of the actual adsorption efficiency for NO3− is retained (Figure 8). The percent uptakes of SQA-Cl-GA initially and after each cycle are 84.6%, 84.8%, 84%, 83.6%, 82.6%, 80.9%, 80.1%, and 78.5%. The total decrease in sorption efficiency of SQA-ClGA after the eighth sorption−desorption cycle is only about 6.1%, which shows that SQA-Cl-GA has good potential to adsorb the NO3− from aqueous solutions even when used G


Article


Table 1. Kinetics Parameters Rate Constants (K) and Correlation Coefficient (R2) for NO3− Removal with SQA-Cl-GA for Pseudo-First-Order, Pseudo-Second-Order, Intraparticle Diffusion, and Elovich Equation Models at Different Reaction Parameters reaction parameters correlation coefficient (R2)

rate constant initial concentration (ppm)

pseudo-firstorder (min−1)

pseudo-second-order (g/mg min−1)

intraparticle diffusion model (mg g−1 min1/2)

pseudofirst-order

pseudosecond-order

intraparticle diffusion model

Elovich equation

10 50 100 250 500

0.4095 0.6845 0.7942 0.8772 0.9584

0.002 0.056 0.027 0.009 0.0001

0.1649 0.8475 1.7017 4.310 7.518

0.9489 0.9998 0.9925 0.9965 0.9983

0.9943 0.9977 0.9968 0.9988 0.9989

0.9930 0.9720 0.9732 0.9771 0.9796

0.9830 0.9916 0.9715 0.9592 0.9697

correlation coefficient (R2) values for the plots indicate good agreement of the NO3− sorption data with linearized isotherm models. The isotherm parameters are given in Table 2. Results

(0.9999) for SQA-Cl-GA in the pseudo-second-order model (Table 1). The sorption capacity values obtained from different kinetic models were compared with experimental values. These results also confirmed that the pseudo-second-order kinetic model has consistency with the experimentally determined values for NO3− adsorption (Figure 9).69 The value of the maximum

Table 2. Values of Parameters for Nitrate Sorption on SQACl-GA at 30 °C as Obtained from Langmuir and Freundlich Models Langmuir model initial concentration (ppm)

KL

10 50 100 250 500

0.119 0.011 0.016 0.022 4.032

Freundlich model

R2

Kf (mg/g)

1/n

R2

0.992 0.999 0.998 0.997 0.999

0.513 0.505 0.504 0.484 0.504

0.990 0.986 0.997 0.998 0.997

0.9992 0.9993 0.9994 0.9990 0.9999

indicate that NO3− sorption can be represented by the Langmuir and Freundlich models reasonably. Both models are then compared for experimental and theoretical adsorption capacity. In the results, Langmuir shows a better match with the values of sorption capacities obtained from experimental values (Figure 10), which is valid for monolayer sorption onto a surface with a finite number of identical quaternary sites. The Langmuir isotherm indicates the maximum uptake value of 208 mg of NO3−/g of bis-quaternary starch. The RL values are also calculated between 0 and 1 and indicates favorable adsorption.

Figure 9. Comparison of adsorption capacity (Q) of SQA-Cl-GA for NO3− in pseudo-second order, intraparticle diffusion, and Elovich equation models with experimental values of 500 ppm concentration, 30 o C temperature, and pH 6.5.

capacity is ≈201 mg of NO3−/g of bis-quaternary starch, which is more promising for commercial resins of Purolite A300 (183 mg/g of resin)70 and Purolite A520E (81.97 mg NO3−/g of resin).29 Moreover, high correlation coefficient values and comparable experimental and calculated Q values undoubtedly suggest that NO3− sorption kinetics can be approximated as pseudo-second order kinetics. This suggests that the sorption is chemisorption and the NO3− exchange rates are limited only by the NO3− ions and quaternary functional groups from the SQACl-GA resin surface that are available to interact. The Elovich equation also fits the experimental data well, which is also used to describe the chemisorption process. The agreement of the Elovich equation with experimental data may be explained by heterogeneity of the active sites.71 3.3. Equilibrium Sorption Isotherm. The adsorption isotherm is the equilibrium relationship between the ion concentration in the aqueous phase and the solid phase. The equilibrium isotherm of NO3− was prepared and compared with Langmuir and Freundlich isothermal models. The high

Figure 10. Comparison of isotherm models adsorption capacity (Q) with experimental values for SQA-Cl-GA at 30 °C and pH 6.5. H


Article


Figure 11. Sorption characterization results for NO3−: (a) FTIR spectrum for SQA-Cl-GA-NO3− and SEM image results of (b) SQA-Cl-GA at 500 magnification, (c) SQA-Cl-GA-NO3− at 500 magnification, (d) SQA-Cl-GA at 2000 magnification and (e) SQA-Cl-GA-NO3− at 3000 magnification.

3.4. Sorption Characterization by FTIR and SEM-EDX. FTIR spectra of the NO3−-loaded quaternary starch was recorded in the range of 4000−400 cm−1 in KBr on a PerkinElmer spectrophotometer to obtain evidence of NO3− uptake. The FTIR spectrum of SQA-Cl-GA-NO3− is presented in Figure 11a for confirmation of sorption. The IR representation provides the possible interaction of NO3− groups with nitrogen quaternary positions by the appearance of new absorption bands (when compared with its precursor in Figure 2) in the range of 1243−1450 cm−1 and 1600−1700 cm−1, characteristic for NO3− as well as the stretching vibration of N−O and NO bands. The sorption characterization is also supported with the change in position and intensity of the characteristic peaks of SQA-Cl-GA.48

Microphotographs of modified SQA-Cl-GA and SQA-Cl-GANO3− were obtained in support of the sorption study with a scanning electron microscope (Jeol JSM 6100) at various magnifications. SEM images of SQA-Cl-GA and SQA-Cl-GANO3− are shown in Figure 11b−e. From the SEM images, it is evident that SQA-Cl-GA possesses a heterogeneous surface due to small out-growths (Figure 11 b and d at 500 and 2000 magnification, repectively), and this surface roughness may possibly be useful in NO3− sorption from aqueous solutions. Moreover, synthesized SQA-Cl-GA is highly porous (highlighted by the circles in Figure 11b and d). After NO3− sorption, the surface of SQA-Cl-GA is attaining smoothness (Figure 11c and e). It is clear from the increased smoothness of the matrix surface in Figure 10c at 500 magnification and decrease in the porosity distance in Figure 11e (3000 magnification) that the I


Article


Figure 12. EDX spectrum of (a) SQA-Cl-GA and (b) SQA-Cl-GA-NO3−.

Figure 13. Proposed ion exchange mechanism for quaternary ammonium starch.

Table 3. Biodegradation Characterization of SQA-Cl-GA before and after NO3− Adsorption polymer

activity of enzyme (U/mL−1 min−1)

weight after degradation (initial weight = 0.1 g)

%weight loss

starch SQA-Cl-GA SQA-Cl-GA-NO3−

88.85 59.44 42.34

0.062 0.084 0.091

38 16 9

Figure 14. SEM images results support biodegradation after amylase action on SQA-Cl-GA-NO3−.

In conclusion, the results suggest that NO3− is adsorbed onto

absorbed nitrate anions are aggregated on the surface of SQA-ClGA. Additionally, the EDX characterization results also support NO3− sorption. SQA-Cl-GA has 8.18% chloride content in the EDX result (Figure 12a) in comparison to 0.12% chloride in SQA-Cl-GA-NO3− (Figure 12b). The results can be accounted for by NO3− sorption, which replaces chloride from the matrix.

the quaternary ammonium starch surface through electrostatic attraction between NO3− and the positively charged quaternary sites. Therefore, the mechanism of NO3− sorption by the quaternary starch may be proposed as is given in Figure 13. J


Article

Industrial & Engineering Chemistry Research Notes

3.5. Biodegradation Studies. The synthesized green exchangers are efficient sorbents with the additional advantage of biodegradability. However, as in the synthetic exchanger, nonbiodegradability creates a thoughtful problem of waste disposal. The modification by grafting or network formation increases the application spectrum for natural polymers. Therefore, to describe the use-profile and technological acceptability of these exchangers, biodegradation by amylase was studied for starch, SQA-Cl-GA-NO3− and SQA-Cl-GA. It has been observed that polymers show the highest enzyme activity within 1 h (Table 3). In comparison, starch has the highest activity followed by SQA-Cl-GA and SQA-Cl-GA-NO3−. The lesser activity in the case of SQA-Cl-GA is accounted for by the uniform derivatization of starch in a quaternary structure (62%−68%). The quaternary reaction occurs at C-2 and C-3 of the anhydroglucose ring. The details for the characterization are presented in our earlier study.48 The high degree of substitution offers steric resistance to amylase, which attacks the glycosidic linkage of the starch chains. Furthermore, the cross-linking and three-dimensional structure of the exchanger lowers the availability of amylase to the glycosidic linkage; hence, enzyme activity is observed to be lower as compared to the starch. The observed enzyme activity is lower for SQA-Cl-GA-NO3− than its precursors, but it is still appreciable. The trends in results are accountable for NO3− sorption, hence lesser approachability and activity of the enzyme. At the end of the degradation, the remaining quaternary starch was removed and dried for the calculation of %weight loss. The maximum weight loss is 38% for pure starch, while SQA-Cl-GA and SQA-Cl-GA-NO3− show % weight loss of 16% and 9%, respectively. SEM characterization is explored to confirm biodegradation, and the results are presented in Figure 14. The results clearly demonstrate the degradation of anion-loaded SQA-Cl-GA after amylase action. The surface is attaining roughness due to starch removal. The latter can be seen as porous structures or voids on the quaternary starch surface.

The authors declare no competing financial interest.

■

(1) Singh, P. K.; Srivastav, A. L.; Ghosh, D. K.; Sharma, Y. C. Preparation and properties of hydrous bismuth oxides for nitrate removal from aqueous solutions. Desalin. Water Treat. 2012, 40 (1−3), 144−152. (2) CGWB (Central Ground Water Board). Report of Central Ground Water Board; Ministry of Water Resources, Government of India, 2010. (3) Bureau of Indian Standards (BIS). Specifications for Drinking Water; IS 10500:1991, New Delhi, 1991/2003. (4) Milmile, S. N.; Pande, J. V.; Karmakar; Bansiwal, S. A.; Chakrabarti, T.; Biniwale, R. B. Equilibrium isotherm and kinetic modeling of the adsorption of nitrates by anion exchange Indion NSSR resin. Desalination 2011, 276, 38−44. (5) Galloway, J. N.; Townsend, A. R.; Erisman, J. W.; Bekunda, M.; Cai, Z. C.; Freney, J. R.; Martinelli, L. A.; Seitzinger, S. P.; Sutton, M. A. Science 2008, 320, 889. (6) Zhang, H.; Hiscock, K. M. Modelling the effect of forest cover in mitigating nitrate contamination of groundwater: a case study of the Sherwood Sandstone aquifier in the East Midlands UK. J. Hydrol. 2011, 399, 212−225. (7) Trevisan, M.; Padovani, L.; Capri, E. Nonpoint -source agricultural hazard index- A case study of the province of Cremona, Italy. Environ. Manage. 2000, 26 (5), 577−584. (8) Wasik, E.; Bohdziewicz, J.; Blasszezyk, M. Removal of nitrate ions from natural water using a membrane bioreactor. Sep. Purif. Technol. 2001, 22−23, 383−392. (9) Lohumi, N.; Gosain, S.; Jain, A.; Gupta, V. K.; Verma, K. K. Determination of nitrate in environmental water samples by conversion into nitrophenols and solid phase extraction−spectrophotometry, liquid chromatography or gas chromatography−mass spectrometry. Anal. Chim. Acta 2004, 505 (2), 231−237. (10) Comly, H. H. Cyanosis in infants caused by nitrates in well water. JAMA, J. Am. Med. Assoc. 1987, 257 (20), 2788−2792. (11) Schoeman, J. J.; Steyn, A. Nitrate removal with reverse osmosis in a rural area in South Africa. Desalination 2003, 155, 15−26. (12) Aslan, S.; Cakici, H. Biological denitrification of drinking water in a slow sand filter. J. Hazard. Mater. 2007, 148 (1−2), 253−258. (13) Reddy, J. K.; Lin, J. P. Nitrate removal from groundwater using catalytic reduction. Water Res. 2000, 34 (3), 995−1001. (14) Boumediene, M.; Achour, D. Denitrification of underground water by specific resin exchange of ion. Desalination 2004, 168, 187− 194. (15) Ben Ali, M. A.; Rakib, M.; Laborie, S.; Viers, P.; Durand, G. Coupling of bipolar membrane electrodialysis and ammonia stripping for direct treatment of wastewaters containing ammonium nitrate. J. Membr. Sci. 2004, 244, 89−96. (16) Della Rocca, C.; Belgiorno, V.; Meric, S. Overview of in-situ applicable nitrate removal processes. Desalination 2007, 204 (1−3), 46−62. (17) Afkhami, A.; Madrakian, T.; Karimi, Z. The effect of acid treatment of carbon cloth on the adsorption of nitrite and nitrate ions. J. Hazard. Mater. 2007, 144 (1), 427−431. (18) Ozturk, N.; Bektas, T. E. Nitrate removal from aqueous solution by adsorption onto various materials. J. Hazard. Mater. 2004, 112, 155−162. (19) Hasnat, M. A.; Ahamad, N.; Nizam Uddin, S. M.; Mohamed, N. Silver modified platinum surface/H+ conducting Nafion membrane for cathodic reduction of nitrate ions. Appl. Surf. Sci. 2012, 258 (7), 3309−3314. (20) Sharma, Y. C.; Singh, B.; Agrawal, A.; Weng, C. H. Removal of chromium by riverbed sand from water and wastewater: effect of important parameters. J. Hazard. Mater. 2008, 151 (2−3), 789−793. (21) Bhatnagar, A.; Sillanpaa, M. A review of emerging adsorbents for nitrate removal from water. Chem. Eng. J. 2011, 168, 493−504.

■

CONCLUSIONS This study shows that a bis-quaternary starch polymer with a high degree of quarterization (62%−68%) is an effective adsorbent for the removal of NO3− from an aqueous solution. In comparison to the commercial Purolite resins (≈183 mg of NO3−/g), cross-linked quaternary starch with a gemini-like structure showed a higher adsorption capacity (202 mg of NO3−/g) for NO3− removal due to the presence of more exchangeable sites with a total ion exchange capacity of 3.8−4.2 mequiv/g. Adsorption was found to be maximum in the pH range from 4.5 to 6.0. Addition of bicarbonate, sulfate, and phosphate as competitive ions marginally reduced the removal of NO3− at 100 ppm, whereas at 500 ppm, phosphate hardly influenced the removal. Adsorption kinetics conformed to a second-order kinetic model and adsorption followed Langmuir isotherms. The mechanism of adsorption was confirmed as an ion exchange between Cl− and NO3− anions. In conclusion, the newly synthesized quaternary starch has technological applications and can be applied more widely in ion exchange processes for practical purification of polluted water resources for nitrate removal in the near future.

■

REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. K


Article


carboxymethyl starch/quaternary ammonium salts complexes. Carbohydr. Polym. 2011, 83, 1680−1689. (43) Shimei, X.; Jingli, W.; Ronglan, W.; Jide, W. Effect of degree of substitution on adsorption behavior of Basic Green 4 by highly crosslinked amphoteric starch with quaternary ammonium and carboxyl groups. Carbohydr. Polym. 2006, 66, 55−59. (44) Auzely-Velty, R.; Rinaudo, M. Synthesis of starch derivatives with labile cationic groups. Int. J. Biol. Macromol. 2003, 31, 123−129. (45) Pal, S.; Mal, D.; Singh, R. P. Cationic starch: an effective flocculating agent. Carbohydr. Polym. 2005, 59 (4), 417−423. (46) Dencs, J.; Nos, G.; Dencs, B.; Marton, G. Investigation of solidphase starch modification reactions. Chem. Eng. Res. Des. 2004, 82 (2), 215−219. (47) Pour, Z. S.; Makvandi, P.; Ghaemy, M. Performance properties and antibacterial activity of crosslinked films of quaternary ammonium modified starch and poly(vinyl alcohol). Int. J. Biol. Macromol. 2015, 80, 596−604. (48) Chauhan, K.; Kaur, J.; Kumari, A.; Kumari, A.; Chauhan, G. S. Efficient method of starch functionalization to bis-quaternary structure unit. Int. J. Biol. Macromol. 2015, 80, 498−505. (49) Sheen, H. T.; Kahler, H. L. Effect of ion on mohr method for chloride determination. Ind. Eng. Chem., Anal. Ed. 1938, 10 (11), 628− 29. (50) Armstrong, F. A. J. Determination of nitrate in water ultraviolet spectrophotometry. Anal. Chem. 1963, 35 (9), 1292−1294. (51) Ozacar, M.; Sengil, I. A. Adsorption of reactive dyes on calcined alunite from aqueous solutions. J. Hazard. Mater. 2003, 98, 211−224. (52) Ozacar, M.; Sengyl, I. A. Two- stage batch sorber design using second order kinetic model for the sorption of metal complex dyes onto pine sawdust. Biochem. Eng. J. 2004, 21, 39−45. (53) Annadurai, G.; Juang, R. S.; Lee, D. J. Use of cellulose based wastes for adsorption of dyes from aqueous solutions. J. Hazard. Mater. 2002, 92, 263−274. (54) Ozacar, M.; Sengil, A. A kinetic study of metal complex dye sorption onto pine saw dust. Process Biochem. 2005, 40, 565−572. (55) Langmuir, I. The constitutional and fundamental properties of solids and liquids. J. Am. Chem. Soc. 1916, 38, 2221−2295. (56) Vijan, L. E.; Neagu, M. Adsorption isotherms of phenol and aniline on activated carbon. Rev. Roum. Chim. 2012, 57, 85−93. (57) Freundlich, H. M. F. Z. Uber die Adsorption im Losungen. Phys. Chem. 1906, 57A, 385−470. (58) Trimble, R. B.; Maley, F. Subunit structure of external invertase from Saccharomyces cerevisiae. J. Biol. Chem. 1977, 252, 4409−4412. (59) Kumar, R.; Kumar, A.; Chauhan, K.; Gupta, R.; Ahn, J.-H.; Chauhan, G. S. Removal of As(V) from water by pectin based active hydrogels following geochemical approach. Bioresour. Technol. 2009, 100, 1474−1477. (60) Ji, Q. X.; Zhong, D. Y.; Lü, R.; Zhang, W. Q.; Deng, J.; Chen, X. G. In vitro evaluation of the biomedical properties of chitosan and quaternized chitosan for dental applications. Carbohydr. Res. 2009, 344, 2424. (61) Karachalios, A.; Wazne, M. Nitrate removal from water by quaternization pine bark using a choline based ionic liquid analogue. J. Chem. Technol. Biotechnol. 2013, 88 (4), 664−671. (62) Sata, T.; Yamaguchi, T.; Matsusaki, K. Interaction between anionic polyelectrolytes and anion exchange membranes and change in membrane properties. J. Membr. Sci. 1995, 100, 229−238. (63) Li, W.; Mo, W.; Kang, C.; Zhang, M.; Meng, M.; Chen, M. Adsorption of nitrate from aqueous solution onto modified cassava (Mannihot esculenta) straw. Ecological Chemistry and Engineering S 2012, 19 (4), 629−638. (64) Dai, J.; Yang, H.; Yan, H.; Shangguan, Y.; Zheng, Q.; Cheng, R. Phosphate adsorption from aqueous solutions by disused adsorbents: Chitosan hydrogel beads after the removal of copper (II). Chem. Eng. J. 2011, 166, 970−977. (65) Dyer, A.; Hudson, M. J.; Williams, P. A. Ion Exchange Processes: Advances and Applications, Royal Society of Chemistry, Cambridge, 1993.

(22) Sharma, Y. C.; Uma; Sinha, A. S. K.; Upadhyay, S. N. Characterization and adsorption studies of Cocos nucifera L. Activated Carbon for the Removal of Methylene Blue from Aqueous Solutions. J. Chem. Eng. Data 2010, 55, 2662. (23) Bae, B. U.; Jung, Y. H.; Han, W. W.; Shin, H. S. Improved brine recycling during nitrate removal using ion exchange. Water Res. 2002, 36, 3330−3340. (24) Saad, R.; Belkacemi, K.; Hamoudi, S. Adsorption of phosphate and nitrate anions on ammonium functionalized MCM-48: effects of experimental conditions. J. Colloid Interface Sci. 2007, 311, 375−385. (25) Samatya, S.; Yuksel, U.; Arda, M.; Kabay, N.; Yuksel, M. Investigation of selectivity and kinetic behavior of strong base ion exchange resins Purolite A520E for nitrate removal from aqueous solution. Sep. Sci. Technol. 2006, 41 (13), 2973−2988. (26) Chabani, M.; Amrane, A.; Bensmaili, A. Kinetics of nitrate adsorption on Amberlite IRA400 resin. Desalination 2007, 206 (1−3), 560−567. (27) Matosic, M.; Mijatovic, I.; Hodzic, E. Nitrate removal from drinking water using ion exchange comparison of chloride and bicarbonate form of the resins. Chem. Biochem. Eng. Q 2000, 14, 141− 146. (28) Kapoor, A.; Viraraghavan, T. Nitrate Removal from Drinking WaterReview. J. Environ. Eng. 1997, 123 (4), 371−380. (29) Samatya, S.; Kabay, N.; Yuksel, U.; Arda, M.; Yuksel, M. Removal of nitrate from aqueous solution by nitrate selective ion exchange resins. React. Funct. Polym. 2006, 66, 1206−1214. (30) Gu, B. H.; Ku, Y. K.; Jardine, P. M. Sorption and binary exchange of nitrate, sulfate, and uranium on an anion-exchange resin. Environ. Sci. Technol. 2004, 38, 3184−3188. (31) Song, H.; Zhou, Y.; Li, A.; Mueller, S. Selective removal of nitrate from water by a macroporous strong basic anion exchange resin. Desalination 2012, 296, 53−60. (32) Alikhani, M.; Moghbeli, M. R. Ion exchange polyHIPE type membrane for removing nitrate ions: preparation, characterization, kinetics and adsorption studies. Chem. Eng. J. 2014, 239, 93−104. (33) Ghaderi, A.; Abbasian, M.; Rahmani, S.; Namazi, H.; Baharvand, H.; Entezami, A. A. Preparation of ion exchange resin from styrene divnyl-benzene copolymer obtained by concentrated emulsion polymerization method. Iran. Polym. J. 2006, 15 (6), 497−504. (34) Xing, X.; Gao, B. Y.; Zhong, Q. Q.; Yue, Q. Y.; Li, Q. Sorption of nitrate onto amine crosslinked wheat straw: characteristics, column sorption and desorption properties. J. Hazard. Mater. 2011, 186, 206− 211. (35) Mishra, P. C.; Patel, R. K. Use of agricultural waste for the removal of nitrate-nitrogen from aqueous medium. J. Environ. Manage. 2009, 90, 519−522. (36) Orlando, U. S.; Baes, A. U.; Nishijima, W.; Okada, M. A new procedure to produce lignocellulosic anion exchangers from agricultural waste materials. Bioresour. Technol. 2002, 83, 195−198. (37) Orlando, U. S.; Okuda, T.; Nishijima, W.; Baes, A. U.; Okada, M. Chemical properties of anion exchangers prepared from waste natural materials. React. Funct. Polym. 2003, 55, 311−318. (38) Orlando, U. S.; Baes, A. U.; Nishijima, W.; Okada, M. Preparation of agricultural residue anion exchangers and its nitrate maximum adsorption capacity. Chemosphere 2002, 48, 1041−1046. (39) Li, Y.; Lin, X.; Zhuo, X.; Luo, X. Poly(vinyl alcohol)/ quaternized lignin composite absorbent: synthesis, characterization and application for nitrate adsorption. J. Appl. Polym. Sci. 2013, 128, 2746−2752. (40) Wang, Y.; Gao, B.-Y.; Yue, W.-W.; Yue, Q.-Y. Preparation and utilization of wheat straw anionic sorbent for the removal of nitrate from aqueous solution. J. Environ. Sci. 2007, 19, 1305−1310. (41) Heinze, T.; Haack, V.; Rensing, S. Starch derivatives of high degree of functionalization preparation of cationic 2-hydroxypropyltrimethylammonium chloride starch. Starch/Starke 2004, 56, 288− 296. (42) Balsamo, V.; Lopez-Carrasquero, F.; Laredo, E.; Conto, K.; Contreras, J.; Feijoo, J. L. Preparation and thermal stability of L


Article

Industrial & Engineering Chemistry Research (66) Sowmya, A.; Meenakshi, S. An efficient and regenerable quaternary amine modified chitosan beads for the removal of nitrate and phosphate anions. J. Environ. Chem. Eng. 2013, 1, 906−915. (67) Awual, R.; Jyo, A.; El-Safty, S. A.; Tamada, M.; Seko, N. A weakfibrous anion exchanger effective for rapid phosphate removal from water. J. Hazard. Mater. 2011, 188, 164−171. (68) Johir, M. A. H.; George, J.; Vigneswaran, S.; Kandasamy, J.; Grasmick, A. Removal and recovery of nutrients by ion exchange from high rate membrane bioreactor (MBR) effluent. Desalination 2011, 275, 197−202. (69) Singh, P. K.; Banerjee, S.; Srivastava, A. L.; Sharma, Y. C. Kinetic and equilibrium modeling for removal of nitrate from aqueous solution and drinking water by a potential adsorbent, hydrous bismuth oxide. RSC Adv. 2015, 5, 35365−35376. (70) Primo, O.; Rivero, M. J.; Urtiaga, A. M.; Ortiz, I. Nitrate removal from electro-oxidized landfill leachate by ion exchange. J. Hazard. Mater. 2009, 164, 389−393. (71) Teng, H.; Hsieh, C. Activation energy for oxygen chemisorption on carbon at low temperatures. Ind. Eng. Chem. Res. 1999, 38, 292− 297.

M


An Efficient and Regenerable Quaternary Starch for Removal of

Recommend Documents