Article pubs.acs.org/est
Combining Ferric Salt and Cactus Mucilage for Arsenic Removal from Water Dawn I. Fox,‡ Daniela M. Stebbins,† and Norma A. Alcantar*,† †
Department of Chemical & Biomedical Engineering, University of South Florida, 4202 E Fowler Ave ENB 118, Tampa Florida 33620, United States ‡ Department of Chemistry, University of Guyana, Turkeyen Campus, Greater Georgetown, Guyana S Supporting Information *
ABSTRACT: New methods to remediate arsenic-contaminated water continue to be studied, particularly to fill the need for accessible methods that can significantly impact developing communities. A combination of cactus mucilage and ferric (Fe(III)) salt was investigated as a flocculation−coagulation system to remove arsenic (As) from water. As(V) solutions, ferric nitrate, and mucilage suspensions were mixed and left to stand for various periods of time. Visual and SEM observations confirmed the flocculation action of the mucilage as visible flocs formed and settled to the bottom of the tubes within 3 min. The colloidal suspensions without mucilage were stable for up to 1 week. Sample aliquots were tested for dissolved and total arsenic by ICP-MS and HGAFS. Mucilage treatment improved As removal (over Fe(III)-only treatment); the system removed 75−96% As in 30 min. At neutral pH, removal was dependent on Fe(III) and mucilage concentration and the age of the Fe(III) solution. The process is fast, achieving maximum removal in 30 min, with the majority of As removed in 10−15 min. Standard jar tests with 1000 μg/L As(III) showed that arsenic removal and settling rates were pH-dependent; As removal was between 52% (high pH) and 66% (low pH).
■
INTRODUCTION This work focused on a new use of cactus mucilage as a natural flocculant for the removal of arsenic from water, following coprecipitation by treatment with ferric salt. It is envisioned that this technology will add to the available options for accessible and sustainable arsenic removal technologies. Arsenic contamination of water was recognized as a global public health problem as early as the 1990s. The volume of ongoing research into mitigating technologies is indirect evidence for the fact that, to date, this problem has not been resolved satisfactorily. Recent research in several parts of the world shows high contents of arsenic in different water resources. Arsenic was identified as one of the major pollutants in the process effluent from a gold mining industry in Ghana, with an average concentration of 10.0 mg/L,1 and in French Mediterranean coastal areas with arsenic concentration in sediment of 16−391 mg/kg.2 Tap water, groundwater, and river water in West Bengal, India, had arsenic concentrations of 8.9− 52.4 mg/L.3 Many conventional technologies exist to remove arsenic from drinking water. These include precipitation (coagulation− flocculation−sedimentation), lime softening, adsorption, ion exchange, membrane filtration, phytoremediation, and electrocoagulation. However, depending on the arsenic species and concentration, as well as the volumes of water to be treated, conventional water treatments can be inaccessible to poor © 2016 American Chemical Society
communities, particularly rural communities in developing or emerging economies. As such, the motivation for this work is to provide an alternative arsenic removal technology that is accessible on account of being made from readily available materials, requiring little or no fossil fuel energy to operate, and being also low-maintenance and easy to operate. We envision that the technology may be suitable to treat As-contaminated surface water and groundwater and project that it has the wider potential to increase the overall efficiency of the main stream technologies for arsenic removal. The majority of low-cost technologies designed for accessibility are based on sorptive filtration with iron and iron oxides to capitalize on their strong affinity for arsenic. Generally, adsorptive technologies are capable of bringing arsenic levels well below the 50 μg/L limit set by some developing countries and depending on the influent concentration to within the 10 μg/L proposed by the World Health Organization (WHO). Another popular adaptation for low-cost arsenic removal is scaled-down coagulation−flocculation− sedimentation treatment. Simply, the arsenic is co-precipitated, and a coagulant is added to make the particles stick together Received: Revised: Accepted: Published: 2507
August 26, 2015 January 4, 2016 January 29, 2016 January 29, 2016 DOI: 10.1021/acs.est.5b04145 Environ. Sci. Technol. 2016, 50, 2507−2513
Environmental Science & Technology
■
(forming larger particles). These particles are then flocculated (grown into bigger, heavier “flocs”) and sedimented or allowed to settle. The clean water then can be filtered or decanted to separate it from the arsenic-bearing precipitate. The advantages of this method are its relative simplicity and low capital cost. Typically, ferric salts (chloride or sulfate) are used as coagulants because they are effective, common, and relatively inexpensive. Flocculants are used to enhance separation by producing larger, denser flocs, which settle faster and shorten the sedimentation time. Furthermore, the use of flocculants also decreases the dosage of coagulant needed. The three main types of flocculants are inorganic salts such as alum, synthetic organic polyionic polymers such as polyacrylamide (PAC), and natural polymer flocculants such as pectin and chitosan. Interest in natural flocculants has increased recently because they are generally less toxic, more environmentally friendly and biodegradable, and, in some instances, less expensive and more abundant than synthetic flocculants. Plant-based mucilages, like several natural polymers, have shown the ability to act as flocculants including starches, cellulose, gums, and pectins.4,5 In this work, we investigated the use of cactus mucilage as a natural flocculant to settle arsenic precipitated by ferric salt. Cactus mucilage is a natural hydrocolloid extracted from the pads of the Opuntia ficus-indica (OFI), also known as the prickly pear cactus and nopal. The cactus is native to Mexico, where it is commonly eaten as a vegetable in soups and salads; we expect the mucilage extract to be biocompatible and biodegradable. A total of two distinct mucilage extracts are obtainable from the OFI pads; a nongelling extract (NE) and a gelling extract (GE). The GE is a pectin, a structural component of the cell wall, and is chemically similar to citrus pectin.6 The mucilage has been used indigenously to clarify turbid water since ancient times. In our research group, we seek to understand the scientific principles of the flocculant properties of the mucilage and to introduce it to various water treatment applications. The extracts have been shown to flocculate particles and bacteria and to interact with arsenic.7−9 In this work, we applied the mucilage as a flocculant to a system using ferric salt as a precipitant and coagulant to remove arsenic from water. Our work is the first to apply the cactus mucilage in this type of combined system (ferric salt and mucilage) for arsenic removal. The GE was shown to successfully flocculate the colloidal hydrous ferric oxide−arsenic complex (represented as FeOx− As) formed from dosing As(V) and As(III) solutions with hydrolyzed ferric solution. The trapping of the FeOx−As complex by the mucilage also aids convenient disposal of the arsenic-bearing waste material. Safe disposal of arsenic-bearing sludge following decantation or filtration is essential to the successful deployment of this technology. Stabilization and solidification is the immobilizing of the As waste by mixing with lime or cement into a mortar, which can be used to make bricks. It is reliable for reducing the leaching and return of arsenic to the environment and suitable for iron-containing wastes, even under long-term simulations.10−12 As such, it is a viable end-of-life route for the present technology. Passive aeration is the storage of the Asbearing waste in containers vented by a network of pipes allowing air into the material. It has been used in West Bengal, India and presents a simpler alternative for containment.13 Although developed for arsenic removal, it is envisaged that the mucilage may be applied to other systems in which solid− liquid separation is desired.
Article
MATERIALS AND METHODS
Mucilage was extracted from the stems (pads) of the O. ficusindica cactus. Pads were obtained from a private nursery, originally purchased from Living Stones Nursery (Tucson, AZ). Water intake was controlled to ensure they all grew at the same rate. No other controls were necessary because different growing conditions affect only the mucilage and pectin content of the pads.14 All chemicals used were analytical grade or better and purchased from Fisher Scientific (Pittsburgh, PA).The mucilage was extracted following protocols published elsewhere.15 The typical extraction yield is 2% wet weight of the cactus pads. The As(V) stock solution used was prepared by dissolving solid sodium arsenate in sufficient deionized water to bring the final As concentration to 1000 μg/L. The As(V) stock solution was continuously aerated using an aquarium aerator, which maintained the dissolved arsenic in the oxidized arsenate form. The 1000 mg/L As(III) stock solution was prepared following the U.S. Environmental Protection Agency (USEPA) method 200.8.16 Batch Experiments. As(V) solutions (10 mL of 100 μg/L As) were treated with ferric nitrate (Fe(NO3)3.9H2O) and GE to attain final Fe(III) concentrations of 0−50 mg/L and final mucilage concentrations of 0−500 mg/L. The solutions were thoroughly mixed and then left to stand for various time periods. To determine the maximum As removal, we left test solutions to stand for 24 h. Sample aliquots were then taken from the top of the test tubules to measure dissolved Fe and As and from the bottom to measure total As. To determine As removal at various time intervals, we ran batch experiments for periods between 5 min to 24 h, and samples were taken from the top only to measure dissolved Fe and As. For total As determination, 1 mL samples taken from the bottom of the column were digested by adding 2 drops of concentrated HNO3 and heating 1−2 h on a water bath at 100 °C. As concentration was then determined using Hydride Generation−Atomic Fluorescence Spectroscopy (HG-AFS). To determine dissolved Fe and As, we acidified and analyzed 1 mL samples taken from the top of the column by inductively coupled plasma mass spectrometry (ICP-MS). These residual concentrations of dissolved species were used to calculate the percent of species removed by difference. Several controls were run: As(V) only, Fe(III) only, mucilage only, Fe(III) and As(V), Fe(III) and mucilage, and As(V) and mucilage solutions. All tests were run in triplicate at room temperature and ambient conditions. To study the effect of Fe(III) and mucilage concentration, we used a simple OVAT design, which is appropriate for this fundamental research work. Jar Test Experiments. The standard practice for coagulation−flocculation jar test ASTM D2035-0817 was used for flocculation of As(III) experiments. Cactus mucilage (50 mg/L) was used as a natural flocculant to settle As(III) (initial concentration 1000 μg/L) co-precipitated by ferric salt (Fe 80 mg/L) under various pH conditions (4, 7, and 10). The pH of the suspension was adjusted by adding NaOH or HNO3. The reactor was initially set at 200 rpm for 1 min followed by 15 min of slow mixing at 10 rpm. The settling rate and diameter of flocs were monitored by video camera equipped with close-up lens. After standing for 15 min, samples of the supernatant were taken. Turbidity, pH and temperature were measured and acidified samples were kept at 4 °C until analysis by ICP-MS. Volume and content of the settled solids were also measured. 2508
DOI: 10.1021/acs.est.5b04145 Environ. Sci. Technol. 2016, 50, 2507−2513
Article
Environmental Science & Technology
■
concentration of 100 μg/L. Solutions similarly prepared but without mucilage were stable to precipitation for 1 week. The enhanced settling of the solution is thought to occur by the following sequence: the hydrolysis of the Fe(III) salt to hydrous ferric oxides, followed by the strong binding of the As by the hydrous ferric oxides, and the coagulation−flocculation of the iron oxide−arsenic (FeOx−As) complex formed by the mucilage to form flocs large enough to settle out of solution. Although the entire process is sensitive to solution pH, we posit that the adsorption of As(III) by hydrous ferric oxide is the most challenging step and warranted investigation. We expect the first step, hydrolysis Fe(III), to be stable for pH 2−14. Hydrous ferric oxide (HFO) forms on rapid hydrolysis of the ferric ion at temperatures 20−30 °C and is stable over a wide pH range (2−14) under oxic ambient conditions, as shown by the potential-pH diagram of iron in water. This pH range brackets the pH of most natural waters (6−8). HFO will dissolve at pH < 2; as such, only acidic water (e.g., process water) would require pH adjustment to facilitate the hydrolysis of ferric ion. The second step in the process is the interaction between HFO and the As species. Arsenic adsorption on iron oxide phases varies with pH, As speciation, initial As concentration, and As/Fe ratio.18−22 Numerous studies have demonstrated the robustness and greater ease of As(V) removal (relative to As(III)) by iron oxide adsorption under a wide range of conditions and solution pH.23−29 For this reason, we have focused our preliminary investigation of pH dependence of our system on the As(III) species; our findings are discussed when the Jar test experiments are presented. The final step in the process is the coagulation−flocculation of the FeOx−As complex by the mucilage resulting in larger flocs, which settle rapidly. The main mechanisms for colloid destabilization are electrical double-layer compression, adsorp-
RESULTS AND DISCUSSION Mucilage Action. The effect of adding cactus mucilage to solutions with ferric salt and As was easily seen with the naked eye because flocs formed immediately after mixing and standing. The mucilage enhanced the coagulation and flocculation of the precipitates. Figure 1 shows the dense
Figure 1. Coagulation and flocculation process of mucilage−FeOx−As system over the time. Triplicates of the experimental units are shown for each time (0, 3, 5, and 10 min). Mucilage enhanced the settling of the FeOx−As complex in a few minutes. The control without mucilage did not precipitate during the experimental time. Concentrations used: mucilage, 100 mg/L; Fe (III), 40 mg/L; and As(V), 100 μg/L.
precipitate formed within 10 min by solutions containing mucilage (100 mg/L), Fe (40 mg/L), and As(V) with initial
Figure 2. Scanning electron microscope images of experimental treatment aliquots. The basic three “ingredients” to prepare the mucilage−FeOx−As complex are shown at top. Nanocrystals of arsenic(V) oxide (100 μg/L) are shown in the top left, hydrolyzed ferric nitrate (40 mg/L) in the top center, and cactus mucilage (100 mg/L) in the top right. Aggregated flocs of mucilage−FeOx−As complex are shown in the bottom left (×3000 magnification), bottom center (×1000 magnification), and bottom right (×500 magnification). The flocs average size is 150 μm × 250 μm. 2509
DOI: 10.1021/acs.est.5b04145 Environ. Sci. Technol. 2016, 50, 2507−2513
Article
Environmental Science & Technology
mucilage because the mucilage flocculated and transported the FeOx−As complex to the bottom of the tube. Effect of Mucilage Concentration. Mucilage concentration was varied to deduce the optimal mucilage dosage at high (50 mg/L) and low (5 mg/L) Fe concentrations. At high Fe concentration, As(V) removal increased with increasing mucilage concentration, reaching a maximum of 96% removed at 100 mg/L GE and then decreasing slightly with further increase in mucilage concentration. Further increases in mucilage concentration beyond 100 mg/L were disadvantageous to As(V) removal. This is probably due to the higher mucilage concentrations causing a vertical accumulation of mucilage in the water column, thereby preventing efficient settling. At low Fe concentration, there was lower As(V) removal (10−20%), which did not correlate with mucilage concentration. These results are shown in Figure 4. It appears that
tion and charge neutralization, enmeshment in a precipitate, and interparticle bridging.30 The mucilage is thought to act mainly by adsorption and bridging mechanisms.8,31,32 Apart from pH-sensitive electrostatic interactions and hydrogenbonding adsorption routes, the mucilage may be able to “stick” to colloidal particles of the iron oxide−arsenic complex by van der Waals interactions due to it being relatively larger; these interactions are not pH-sensitive33 and become important when the particle and the mucilage have similar charges. We noted fresh ferric nitrate solutions did not perform as well as aged solutions; this was due to incomplete hydrolysis of the fresh solutions, which was supported by the literature.34 Scanning electron microscopy (SEM) also has shown the difference among the treatments and confirmed the role of the mucilage as a flocculant. A comparison of SEM images of the control with only arsenic, control with only iron, control with only mucilage, and the combination, under the best experimental conditions (mucilage 100 mg/L, Fe (III) 40 mg/L and As(V) 100 μg/L), are shown in Figure 2. The controls with only arsenic and only iron did not present flocs (Figure 2 panels 1 and 2); the control with only mucilage showed a thin layer of the dried pectin with formation of small size flocs (Figures 2 and 3); the treatment with the presence of arsenic, iron, and mucilage (GE) showed the formation of larger and stable mucilage-FeOx−As flocs (Figure 2 panels 4a, 4b, and 4c).
Figure 4. Arsenic(V) removal as a function of GE concentration (Fe 40 mg/L). Optimal arsenic removal observed at 100 mg/L GE; optimal Fe removal observed at 250 mg/L GE.
FeOx−As complex formation is the controlling step in the process; the mucilage appears to provide a framework or surface on which colloid nuclei can aggregate and form larger flocs. As such, any variable that enhances complex formation, such as increasing Fe concentration, is expected to enhance the overall process. In these experiments, the As(V) challenge was 100 μg/L, so at the best performance, the As(V) residual was less than 10 μg/L, which is the maximum contaminant level proposed by WHO. Effect of Fe (III) Concentration. The effect of increasing the Fe(III) dosage from 5 to 50 mg/L is shown in Figure 5. As expected, arsenic removal increased with increasing Fe(III) concentration, reaching a maximum of 90% removal at 40 mg/ L; further increase in Fe(III) concentration did not yield greater As(V) removal. These results corroborate the earlier finding that forming the FeOx−As complex is the controlling step in the process. Under these conditions, the maximum removal was reached when the As(V) available by diffusiononly mass transfer was exhausted.
Figure 3. Performance of the iron−mucilage system compared to system with iron only; As(V) 100 μg/L, GE 100 mg/L, and Fe 40 mg/ L. Concentrations are 1:10 dilutions of samples taken from the bottom of the columns. The increase of arsenic concentration at the bottom of the solution can be seen, demonstrating arsenic precipitation along with mucilage flocs.
Taken together, these results visibly demonstrate the effective flocculation action of the mucilage in the FeOx−As system. Arsenic Removal. Arsenic solutions treated with iron and mucilage showed superior arsenic removal to solutions treated with only iron. Figure 3 shows the As concentration of samples taken from the bottom of the test tubules, digested, and analyzed for total arsenic. Note that in the control (iron-only treatment), the total As(V) concentration was lower and fairly constant over time compared to the samples treated with 2510
DOI: 10.1021/acs.est.5b04145 Environ. Sci. Technol. 2016, 50, 2507−2513
Article
Environmental Science & Technology
conditions of 50 mg/L Fe(III), 100 mg/L mucilage, and As(V) of 100 μg/L. The process was fast, achieving equilibrium within 30 min, with the majority of the removal being achieved in 10− 15 min. There was some variation observed in the equilibrium end point; As(V) removal at 24 h ranged from 75−96%; this was due to different extents of hydrolysis of the dissolved Fe(III) salt. Following these results, aged Fe(III) solutions were used to benefit from maximal hydrolysis and HFO formation. The shape of the curves for the time-based experiments speaks to the adsorption of the particles of FeOx−As complex on the mucilage surface. Equilibrium (maximum removal) is achieved when no more surface sites are available or can be accessed by the complex. Moreover, the adsorption time is limited by the settling of the mucilage, which sinks faster as it gets heavier with adsorbed FeOx−As particles. Jar Test Experiments. Mucilage treatment was effective at aiding As(III) removal from iron-treated samples in standard jar test experiments. Figure 7 shows that mucilage-treated samples showed higher As(III) removal than control samples treated with iron only or receiving no treatment. However, both arsenic removal and settling velocity were affected by pH. The arsenic removal was significantly higher on the mucilage and FeOx system at pH 4 (up to 66.4% removal), with the arsenic concentration dropping from the initial 1000.3 to 336.5 μg/L (Figure 7). As(III) has a pKa of 9.2, being mostly uncharged in pH below 9.2. At low pH values, the removal of As(III) could be due to physical adsorption on the mucilage-iron complex net, rather than assigned to any type of ion-exchange process.36 Surface area of the mucilage-iron complex may related to the increase of As (III) removal capacity at low pH values.36 Settling velocity was affected by the pH, with the pH 4 showing faster settling (0.81 ± 0.06 cm/s) than did pH 7 (0.57 ± 0.04 cm/s) and pH 10 with no visible precipitate formation. In comparison, the settling velocity of chitosan polymer was reported to vary from less than 0.1 up to 0.35 mm/sec depending on the dosage and pH values,37 while Brostow et al. (2008)33 reported settling velocities from 0.43 to 0.64 cm/s for various cationic polysaccharides on Fe ore. The floc size on the mucilage−FeOx−As system at pH 4 were 2.25 times larger than control Fe, and the formation of the first floc was faster, with the flocculation process initiating instantly after the fast mixing stage. However, there was no significant change on the settling rate comparing the mucilage treated system at pH 4
Figure 5. Arsenic(V) removal as a function of Fe(III) concentration (GE 100 mg/L). Optimal As(V) and Fe(III) removal seen at 40 mg/L Fe(III) concentration.
Fe(III) residuals were calculated from the determination of dissolved Fe(III) in samples taken from the top of the test tubules. The best (lowest) residual value was 7.5 mg/L at 250 mg/L GE, and the highest residual was 43 mg/L at 5 mg/L GE. The USEPA has set the secondary maximum contaminant level for Fe at 0.3 mg/L.35 Although it is not a toxic pollutant, dissolved Fe imparts a metallic taste and smell to potable water, which makes it unpalatable. In a nonconventional setting, these residual dissolved Fe concentrations may be lowered to potable range by aeration to promote precipitation of iron oxide followed by sand filtration. From these results, we infer that mucilage treatment improved arsenic removal in the FeOx−As system and that important factors are mucilage and Fe(III) concentration and age of the Fe(III) solution. Time-Based Experiments. Figure 6 shows the time-based As(V) removal by mucilage and iron combination acquired by batch experiments. The plot represents the amount of As(V) removed by the mucilage over time for the optimized initial
Figure 6. Time-based As(V) removal after 6 h (left) and 24 h (right). Maximum removal was generally observed by 30 min; the fastest removal rate was within first 10 min. 2511
DOI: 10.1021/acs.est.5b04145 Environ. Sci. Technol. 2016, 50, 2507−2513
Article
Environmental Science & Technology
Figure 7. As(III) concentration (left) and removal (right) after the standard practice for coagulation−flocculation jar test using cactus mucilage (50 mg/L) and ferric salt (Fe 80 mg/L) under various pH conditions (4, 7, and 10).
(0.81 ± 0.06 cm/s) with the control Fe-only treated system (0.85 ± 0.07 cm/s). We propose that the pH dependence of the mucilage− FeOx−As(III) system can be explained by considering the charges on the various species involved and the ways in which they interact. The hydrolysis of ferric ion to form hydrous ferric oxide (represented here as FeOx) is stable in the pH range studied (4, 7, and 10) but is expected to be faster and more stable at high pH. Once formed the FeOx surface charge responds to pH by the representative equilibria FeOH2+⇔ FeOH at low and neutral pH (yielding neutral and positive surface) and FeOH⇔FeO− at high pH (yielding neutral and negative surface).38 The speciation of As(III) is also pHdependent; the uncharged H3AsO3 species dominates below pH 9.2, and the negatively charged H2AsO3− dominates above. The pH dependence of adsorption of As(III) onto FeOx species is debated in the literature as increasing with increasing pH20 or, conversely, being independent of pH.39,40 We hypothesize that at high pH, the interaction may in fact be hindered by electrostatic repulsions between a negative surface charge on FeOx species and the negatively charged H2AsO3−, which would account for the lack of visible FeOx−As(III) complex formation at pH 10. The interaction between the mucilage and the FeOx−As complex is expected to be primarily interparticle bridging by van der Waals interactions and, hence, does not depend significantly on pH. Overall, these results show mucilage treatment improved arsenic removal from the FeOx−As(III) system, with pH being an important variable.
■
supported by the National Science Foundation (RAPID NSF CBET 103489 and 1057897). The authors acknowledge partial support from the Gulf of Mexico Research Initiative. We acknowledge financial support for one of the authors (DIF) provided by the Schlumberger Foundation Faculty for the Future fellowship.
■
(1) Acheampong, M. A.; Paksirajan, K.; Lens, P. N. L. Assessment of the effluent quality from a gold mining industry in Ghana. Environ. Sci. Pollut. Res. 2013, 20, 3799−3811. (2) Mamindy-Pajany, Y.; Bataillard, P.; Seby, F.; Crouzet, C.; Moulin, A.; Guezennec, A.; Hurel, C.; Marmier, N.; Battaglia-Brunet, F. Arsenic in marine sediments from the Mediterranean coast: Speciation in the solid phase and occurrence of thioarsenates. Soil Sediment Contam. 2013, 22 (8), 984−1002. (3) Sharma, P.; Asad, S.; Ali, A. Bioluminescent bioreporter for assessment of arsenic contamination in water samples of India. J. Biosci. 2013, 38 (2), 251−258. (4) Choy, S. Y.; Prasad, K. M. N.; Wu, T. Y.; Raghunandan, M. E.; Ramanan, R. N. Utilization of plant-based natural coagulants as future alternatives towards sustainable water clarification. J. Environ. Sci. 2014, 26 (11), 2178−2189. (5) Yin, C.-Y. Emerging usage of plant-based coagulants for water and wastewater treatment. Process Biochem. 2010, 45 (9), 1437−1444. (6) Cardenas, A.; Goycoolea, F. M.; Rinaudo, M. On the gelling behaviour of ’nopal’ (Opuntia ficus indica) low methoxyl pectin. Carbohydr. Polym. 2008, 73 (2), 212−222. (7) Buttice, A. L.; Stroot, J. M.; Lim, D. V.; Stroot, P. G.; Alcantar, N. A. Removal of Sediment and Bacteria from Water Using Green Chemistry. Environ. Sci. Technol. 2010, 44 (9), 3514−3519. (8) Miller, S. M.; Fugate, E. J.; Craver, V. O.; Smith, J. A.; Zimmerman, J. B. Toward understanding the efficacy and mechanism of Opuntia spp. as a natural coagulant for potential application in water treatment. Environ. Sci. Technol. 2008, 42 (12), 4274−4279. (9) Young, K.; Anzalone, A.; Alcantar, N. Using the Mexican cactus as a natural-based process for removing contaminants in drinking water. Abstracts of Papers American Chemical Society 2005, 230, U3767. (10) Clancy, T. M.; Hayes, K. F.; Raskin, L. Arsenic Waste Management: A Critical Review of Testing and Disposal of ArsenicBearing Solid Wastes Generated during Arsenic Removal from Drinking Water. Environ. Sci. Technol. 2013, 47, 10799−10812. (11) Clancy, T. M.; Snyder, K. V.; Reddy, R.; Lanzirotti, A.; Amrose, S. E.; Raskin, L.; Hayes, K. F. Evaluating the cement stabilization of arsenic-bearing iron wastesfrom drinking water treatment. J. Hazard. Mater. 2015, 300, 522−529. (12) Sullivan, C.; Tyrer, M.; Cheeseman, C. R.; Graham, N. J. D. Disposal of water treatment wastes containing arsenic A review. Sci. Total Environ. 2010, 408, 1770−1778. (13) Sarkar, S.; Blaney, L. M.; Gupta, A.; Ghosh, D.; SenGupta, A. Arsenic removal from groundwater and its safe containment in a rural
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.5b04145. A table showing the standard jar test data. (PDF)
■
REFERENCES
AUTHOR INFORMATION
Corresponding Author
*Tel: (813) 974 8009; e-mail:
[email protected]. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS The authors acknowledge the help of Dr. Zachary Atlas, Department of Geology, University of South Florida for assistance with ICP-MS measurements. This research was 2512
DOI: 10.1021/acs.est.5b04145 Environ. Sci. Technol. 2016, 50, 2507−2513
Article
Environmental Science & Technology environment: Validation of a sustainable approach. Environ. Sci. Technol. 2008, 42, 4268−4273. (14) Valdivia, B. C. P.; Urdaneta, B. A. S. Nopalito and cactus pear (Opuntia spp.) polysaccharides: mucilage and pectin. Acta Hortic. 2006, 728, 241−247. (15) Fox, D.; Pichler, T.; Yeh, D.; Alcantar, N. Removing heavy metals in water: The interaction of cactus mucilage and arsenate (As(V)). Environ. Sci. Technol. 2012, 46 (8), 4553. (16) USEPA. Method 200.8 Determination of trace elements in waters and wastes by ICP-MS (Revision 5.4), 1994. (17) D 2035-08, Standard Practice for Coagulation-Flocculation Jar Test of Water; ASTM International: West Conshocken, PA, 2008. (18) Dixit, S.; Hering, J. G. Comparison of Arsenic(V) and Arsenic(III) Sorption onto Iron Oxide Minerals: Implications for Arsenic Mobility. Environ. Sci. Technol. 2003, 37 (18), 4182−4189. (19) Mamindy-Pajany, Y.; Hurel, C.; Marmier, N.; Romeo, M. Arsenic (V) adsorption from aqueous solution onto goethite, hematite, magnetite and zero-valent iron: Effects of pH, concentration and reversibility. Desalination 2011, 281, 93−99. (20) Raven, K. P.; Jain, A.; Loeppert, R. H. Arsenite and Arsenate Adsorption on Ferrihydrite: Kinetics, Equilibrium, and Adsorption Envelopes. Environ. Sci. Technol. 1998, 32, 344−349. (21) Waychunas, G. A.; Rea, B. A.; Fuller, C. C.; Davis, J. A. Surface chemistry of ferrihydrite: Part 1. EXAFS studies of the geometry of coprecipitated and adsorbed arsenate. Geochim. Cosmochim. Acta 1993, 57, 2251−2269. (22) Wilkie, J. A.; Hering, J. G. Adsorption of arsenic onto hydrous ferric oxide: effects of adsorbate/adsorbent ratios and co-occurring solutes. Colloids Surf., A 1996, 107, 97−110. (23) Cundy, A. B.; Hopkinson, L.; Whitby, R. L. D. Use of iron-based technologies in contaminated land and groundwater remediation: A review. Sci. Total Environ. 2008, 400, 42−51. (24) Hussam, A.; Munir, A. K. M. A simple and effective arsenic filter based on composite iron matrix: Development and deployment studies for groundwater of Bangladesh. J. Environ. Sci. Health, Part A: Toxic/Hazard. Subst. Environ. Eng. 2007, 42, 1869−1878. (25) Mohan, D.; Pittman, C. U. Arsenic removal from water/ wastewater using adsorbents - A critical review. J. Hazard. Mater. 2007, 142 (1−2), 1−53. (26) Ngai, T. K. K.; Shrestha, R. R.; Dangol, B.; Maharjan, M.; Murcott, S. E. Design for sustainable development - Household drinking water filter for arsenic and pathogen treatment in Nepal. J. Environ. Sci. Health, Part A: Toxic/Hazard. Subst. Environ. Eng. 2007, 42 (12), 1879−1888. (27) Van Den Bergh, K.; Du Laing, G.; Montoya, J. C.; De Deckere, E.; Tack, F. Arsenic in drinking water wells on the Bolivian high plain: Field monitoring and effect of salinity on removal efficiency of ironoxides-containing filters. J. Environ. Sci. Health, Part A: Toxic/Hazard. Subst. Environ. Eng. 2010, 45 (13), 1741−1749. (28) Yuan, T.; Hu, J. Y.; Ong, S.; Luo, Q.; Ng, W. J. Arsenic removal from household drinking water by adsorption. J. Environ. Sci. Health, Part A: Toxic/Hazard. Subst. Environ. Eng. 2002, 37 (9), 1721−1736. (29) Yuan, T.; Luo, Q.; Hu, J.; Ong, S.; Ng, W. A study on arsenic removal from household drinking water. J. Environ. Sci. Health, Part A: Toxic/Hazard. Subst. Environ. Eng. 2003, 38 (9), 1731−1744. (30) Bratby, J. Coagulation and Flocculation: With an Emphasis on Water and Wastewater Treatment; Uplands Press Ltd: Croydon, England, 1980. (31) Okuda, T.; Baes, A. U.; Nishijima, W.; Okada, M. COAGULATION MECHANISM OF SALT SOLUTION-EXTRACTED ACTIVE COMPONENT IN MORINGA OLEIFERA SEEDS. Water Res. 2001, 35, 830−834. (32) Yin, C.-Y. Emerging usage of plant-based coagulants for water and wastewater treatment. Process Biochem. 2010, 45, 1437−1444. (33) Brostow, W.; Lobland, H. E. H.; Pal, S.; Singh, R. P. Settling rates for flocculation of iron and manganese ore-containing suspensions by cationic glycogen. Polym. Eng. Sci. 2008, 48 (10), 1892. (34) Dzombak, D. A.; Morel, F. M. M. Surface complexation modelling: Hydrous ferric oxide;. John Wiley & Sons: New York, 1990.
(35) Pontius, F. W. A current look at the federal drinking water regulations. Journal of the American Water Works Association 1992, 3, 36−50. (36) Glocheux, Y.; Albadarin, A. B.; Mangwandi, C.; Stewart, E.; Walker, G. M. Production of porous aluminium and iron sulphated oxyhydroxides using industrial grade coagulants for optimized arsenic removal from groundwater. J. Ind. Eng. Chem. 2015, 25, 56−66. (37) Pan, J. R.; Huang, C.; Chen, S.; Chung, Y. Evaluation of a modified chitosan biopolymer for coagulation of colloidal particles. Colloids Surf., A 1999, 147, 359−364. (38) Cornell, R.; Schwertmann, U. The iron oxides: Structure, properties, reactions, occurrences and uses; Wiley-VCH: Weinheim, 2003. (39) Aredes, S.; Klein, B.; Pawlik, M. The removal of arsenic from water using natural iron oxide minerals. J. Cleaner Prod. 2013, 60, 71− 76. (40) Razzouki, B.; El Hajjaji, S.; Azzaoui, K.; Errich, A.; Lamhamdi, A.; Berrabah, M.; Elansari, L. L. Physicochemical study of arsenic removal using iron hydroxide. Journal of Material and Environmental Science 2015, 6 (5), 1444−1450.
2513
DOI: 10.1021/acs.est.5b04145 Environ. Sci. Technol. 2016, 50, 2507−2513
