|
|||||||
| Effective and efficient arsenic removal from water using industrial waste as adsorbent by adsorption method | |||||||
| Paper Id :
16546 Submission Date :
2022-10-10 Acceptance Date :
2022-10-16 Publication Date :
2022-10-25
This is an open-access research paper/article distributed under the terms of the Creative Commons Attribution 4.0 International, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. For verification of this paper, please visit on
http://www.socialresearchfoundation.com/resonance.php#8
|
|||||||
| |||||||
| Abstract |
Arsenic is a universally distributed element which may be found in earth’s crust, atmosphere and in water. It is mobilized through a combination of natural processes as well as through a range of anthropogenic activities. But most of the environmental arsenic problems are the result of its mobilization under natural conditions. In the environment several sources of As in ground water and dinking water have a greatest challenge for helth of human. In aqueous stream, the well-known poison arsenic exists commonly in trivalent and penta valent arsenic forms. The trivalent species is of great environmental concern not only because of its considerably high toxicity but also in view of its high mobility and solubility. A combination of high toxicity and widespread occurrence of arsenic has created a pressing need to develop an effective arsenic remedial technique. Thus, in order to decontaminate arsenic from dilute solutions, adsorption processes have been developed using a low cost adsorbent. In the present work we have developed carbonaceous adsorbent from fertilizer industry plant waste. The characterization of adsorbent prepared has shown that the carbonaceous
adsorbent prepared from carbon slurry possesses high porosity and maximum surface area. The adsorption of arsenic on prepared a carbonaceous adsorbent is significant in acidic medium. The results indicate that carbonaceous adsorbent can be employed as an adsorbent for reducing arsenic concentrations to less than 166.7 μg/L (with 1 g/L adsorbent dose and initial arsenic concentration of 200 μg/L) in water for use in small systems. Moreover, the carbonaceous adsorbent (approximately one third cost per kilogram) can be used for the removal of arsenic as a low-cost alternative to activated charcoal.
|
||||||
|---|---|---|---|---|---|---|---|
| Keywords | Adsorption, Low Cost, Carbonaceous Adsorbent, Arsenic, Industrial Waste. | ||||||
| Introduction |
The next war may be due to freshwater, in a new era, the demand for freshwater consecutively increases globally. In earth's atmosphere, the total water supply of about 332.5 million mi3of water whereas 96% of water is saline water and approximately only 3% of water is freshwater. However, of the total freshwater 68% is locked up in glaciers and about 32% of freshwater is in the ground. Drinking water in the earth's atmosphere is 1.2%. Moreover, in the new era, environmental pollution has increased to a noticeable level due to global population growth, rapid industrialization growth increases the demand for products, industrial exploitation of natural resources, and persistent droughts[1-2] and water demand is consecutive increases because the freshwater consumed in many activities of humans i.e. dirking, bathing, fluxing, washing, and cooking, etc. Retaining fresh water in the earth atmosphere is a future challenge globally because of environmental pollution. Moreover, industrial growth and agricultural and municipal activities have contributed directly to the rise in the continuous discharge of dyes, heavy metals, phenolic and organic, and inorganic chemicals into water bodies[3]. Hence, heavy metals can be defined as metallic elements that have a relatively high density compared to water. With the assumption that heaviness and toxicity are interrelated, heavy metals also include metalloids, such as arsenic, that are able to induce toxicity at low levels of exposure[4]. Arsenic is situated in the periodic table in Group 15 and its atomic number is 33. Arsenic is rarely found as a free element in the natural environment, generally, it occurs mainly in four oxidation states (3, 0, +3, +5), while the two oxidation states common in drinking water are oxyanions of trivalent Arsenic (III) and pentavalent Arsenic[5]. Water contamination is one of the most critical issues being faced by society due to industrial and population growth. However, plenty of heavy metals contaminate the groundwater and surface water soil, and atmosphere day by day even in very low concentrations. Heavy metals are a group of trace elements that include metals and metalloids, such as arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, tin, and zinc[6]. Heavy metals are classified as toxic and carcinogenic; they are capable of accumulating in tissues and causing diseases and disorders. Arsenic contamination in drinking water, as well as groundwater, has become a serious threat to the environment, human health, and animals. The presence of toxic and carcinogenic arsenic in drinking water, as well as groundwater, is increasing continuously due to which a large number of people have potentially threat with various diseases. It is a worldwide problem, some of the most affected regions lie in the flood plains of the great rivers of Bangladesh, Nepal, West Bengal, and India. Arsenic is a poisonous element, odorless and tasteless, which can lead to health effects for humans, animals, and living organisms if present in more than the permissible limit of BIS. Humans and animals consume large quantities of water; therefore, its presence in drinking water is very serious and likely to adversely affect health. Long-term drinking water exposure to arsenic causes skin, lung, bladder, and kidney cancer as well as pigmentation changes, skin thickening, neurological disorders, muscular weakness, loss of appetite, and nausea. Arsenic enters drinking water supplies through natural deposits in the earth, agriculture, and industrial practices. However, contamination of aquatic systems is a serious environmental issue and therefore the development of efficient and suitable technology to remove arsenic from aqueous solutions is necessary. Therefore, it was thought necessary to develop an efficient method to reduce the concentration of arsenic in drinking water to a safe level as prescribed by BIS (10500:1991).
A variety of methods has been used in the past to remove arsenic from contaminated water Membrane Filtration, Solvent Extraction, Ion exchange, electrochemical treatment, Reverse Osmosis, and Adsorption, etc.
Many of these methods suffer from high capital and operating costs. Adsorption seems to be one of the most suitable methods due to its high efficiency, low cost, and ease of operation. Various adsorbents, such as carbon foam, activated carbon, zeolite, clay minerals, organic polymers, and biochar, even many waste materials, such as fly ash, reused sanding waste, biomass, and water treatment residue (WTR), have been used to removal of heavy metals by adsorption methods. The most effective heavy metal adsorbents, especially for the removal of arsenic, are metal oxides (Fe, Al, Mn oxides), such as WTRs, swamp iron ore, ferrihydrite, goethite, layered double hydroxide, red clay, and fertilizer industry waste.[7-22]. Although several reports have proved that the adsorption technique for the removal of arsenic is one of the best techniques for reducing the arsenic concentration in drinking water as per WHO guidelines or BIS guidelines[23]. The WHO guideline is 10 ppb (0.01 mg/L) for arsenic and as per BIS guidelines, 10 ppb (0.01 mg/L) concentration of arsenic has been prescribed as a permissible limit in the drinking water[24].
For developing countries like India, where people cannot afford costly means, the development of a low-cost and eco-friendly adsorbent is required for the removal of arsenic from water. Hence, in this study, a low-cost adsorbent from fertilizer industry waste has been developed and used for the removal of arsenic from water.
|
||||||
| Objective of study | The objectives of the research program carried out are summarized as under:
1. To prepare a stock solution (1000 mg/l) in purified water by dissolving 1.32 g of arsenic trioxide in 30 ml of 3 M sodium hydroxide solution.
2. To optimize conditions for efficient and reproducible determination of arsenic at low concentrations using an Atomic Absorbance Spectrophotometer.
3. To develop an eco-friendly and low-cost adsorbent from fertilizer industry waste (carbonaceous waste) for the removal of Arsenic from water.
4. To optimize conditions for the effective removal of arsenic from water using developed adsorbent,
Equilibrium Concentration, Contact Time, Effect of Temperature, pH Effect, and effect of Surface Area of Adsorbent
5. To develop an effective, efficient, fast, and reproducible adsorption method and the best condition to remove arsenic from water. |
||||||
| Review of Literature | The pollution of water bodies due to the
disposal of heavy metal wastes is an increasing worldwide concern for the last
few decades. Various methods are currently being investigated with varying
degree of success. The most widely applied methods for the metal removal from
water/waste waters are chemical and electrochemical precipitation, cationic and
anionic ion exchange resins, membrane filtration and sorption. The cost effectiveness
of most methods can be questionable. Whereas some methods such as ion-exchange
are costly, others such as precipitation techniques have problems for disposal
of heavy metal containing sludge. Apart from these, adsorption technique is
very popular due to simplicity and low cost. Although activated carbon is
frequently used as general adsorbent of inorganic and organic compounds,
alternative low cost adsorbents are being developed. Different adsorbents like
mesoporous silica have been used for the removal of aqueous heavy metals by
adsorption. Some of these include adsorbents like rice husks and rice bran,
tartaric acid modified rice husks, chitosan, lignin, modified lignin, cocoa
shells, coir fibers, carbon aerogels, coal, fly ash, red mud, clays, zeolites,
pottery, bone charcoal, seeds and seed husks etc. that are being actively
investigated with varying degree of success [22, 25-27] |
||||||
| Methodology | All chemicals, used in this study, were of analytical grade obtained either from, Renkem, Merck, Germany or SD Fine Chem. Ltd., India. A stock solution of arsenic was prepared using As2O3 in purified water. Purified analytical grade water was prepared using Millipore Milli-Q water purification systems. As solution of different concentrations were obtained by diluting the stock solution. Standard solution of As (1000 mg/L) for atomic absorption spectrophotometer was obtained from Merck, Germany. Standard acid and base solutions (0.5M H2SO4 and 1M NaOH) were used for pH adjustments.
Particle Sizing of Adsorbents:
All the powdered adsorbents were passed through different British Standard Sieves (BSS), and fractions corresponding to 100-150, 150-200, and 200-250 mesh were collected. Adsorption on particles of different sizes was studied in order to understand the effect of particle size of adsorbent material.
Preparation of Sample:
Arsenic trioxide (As2O3) was used as the source of Arsenic. A stock solution (1000 mg/l) was prepared in purified water by dissolving 1.32 g of arsenic trioxide in 30 ml of 3 M sodium hydroxide solution. The resulting solution was neutralized with 3 M sulphuric acid to a phenolphthalein endpoint and diluted to 1L with dilute sulphuric acid.
Preparation of Low Cost Adsorbent:
Carbonaceous Adsorbent:
Carbon slurry waste was collected from the National Fertilizer Limited Plant, Panipat (Haryana). It was found to consist of small, black and greasy granules and treated with hydrogen peroxide to oxidize the adhering organic material and then washed with water and heated to 200ºC till the evolution of black soot stopped. The dried material was then activated at 400ºC temperature in a muffle furnace for 2 h in air atmosphere. After the complete activation the materials was cooled and the ash content was removed by treating the material with 1 M hydrochloric acid and washed with distilled water three to four times and dried. The finished product was called carbonaceous adsorbent. |
||||||
| Sampling |
Batch Studies
Batch sorption experiments were conducted to obtain rate
and equilibrium data, using 250-ml Erlenmeyer flasks kept at room temperature;
a wrist action shaker was used for shaking the solution. The reaction mixture
consisted of a 50 ml arsenic solution of known concentration and the carbonaceous
adsorbent which was weighed (50 mg) and added to the solution. After completion of the required reaction time, the flask was removed followed by the solution was filtered using filter paper. All experiments were carried out at room
temperature (25◦C±1◦C). To study the effect of initial pH
(4.0–10.0) on arsenic uptake, experiments were performed with initial arsenic
concentrations of 200 μg/l and an adsorbent dose of 1 g/l at a fixed
contact time of 6 h. Isotherm studies were conducted with varying initial
arsenic concentrations (100–1000 μg/l), fixed adsorbent dose of 1 g/l,
and contact time of 6 h at pH 7.0. The effect of contact time was studied with
an initial arsenic concentration of 200 μg/l and an adsorbent dose of 1 g/l;
pH was kept at 7.0 and contact time was varied from 15 to 720 min. The effect
of adsorbent was studied by varying the dose from 1 to 10 g/l at a fixed
pH of 7.0 with an initial As the concentration of 200 μg/l and a contact
time of 12 h. |
||||||
| Result and Discussion |
Adsorption Isotherms Adsorption isotherm is a mathematical expression that relates the concentration of the adsorbate in the interface to its equilibrium concentration in the liquid phase. Before calculating the isotherm, equilibrium sorption capacity, qe, was determined by using the following equation: Where Ci and Ce are the initial and equilibrium concentration of metal element the solution (mg/L), respectively, V is volume of the solution (in Liter) and Ms is the weight of adsorbent (mg). The results from this computation were used in calculating the isotherm. In this research, Langmuir 26 and Freundlich 27 isotherm were studied. Langmuir Isotherm: For Langmuir isotherm the equation (ii) is given below:
Where b is the maximum adsorption capacity corresponding to complete monolayer coverage (mg of solute adsorbed per g of adsorbent) and Keq is the Langmuir constant related to energy of adsorption. The linear form can be used for linearization of experimental data by plotting Ce/qe against Ce. The Langmuir constants b and K can be evaluated from the slope and intercept of the following linear equation.
Freundlich Isotherm For Freundlish equation as stated in equation (iv),
where K and n are Freundlish constant. A plot of log Ce versus log qe yields a straight line which indicates the conformation of Freundlish isotherm for adsorption. The constant can determined from the slope and intercept.
Characterization of the Prepared Adsorbents: The FTIR spectra of carbonaceous adsorbent and adsorbent
loaded with arsenic were recorded in dried KBr (0.1g). The FTIR spectra of
carbonaceous adsorbent (Fig.1) indicates the presence of prominent bands lying
at 1400, 1616, 3128 and 3408 cm-1. The first strong band at 1400 cm-1 may
be assigned to the presence of methyl and methylene group. The strong band
appearing at 1616 cm-1 might be attributed to C=S, C=C and C=O
stretch whereas, the bands appearing in the region 3128 and 3408 cm-1 may
be assigned to the presence of the alkyl group and OH group (Fig.1). As seen in
Fig.1, the intensity of absorbance peaks in the adsorbent loaded with arsenic
is slightly lower than that in the native one. The analysis of the FTIR spectra
showed the presence of functional groups able to interact with metal, whereas,
strong band at 1400 cm-1 is disappeared after loading arsenic
on adsorbent surface. The surface area was determined by nitrogen gas
adsorption for carbonaceous adsorbent and was found to be 360 m2/g 25.
The CHNS analytical data of adsorbent indicate the carbon content as 84.2 %
whereas, the carbon content decreased after loading Arsenic on adsorbent
surface, where the elemental analysis showed composition of carbon, hydrogen
and sulphur as 42.20, 2.52 and 5.01%.
Figure.1. IR spectra of carbonaceous adsorbent
before adsorption and after adsorption in KBr. Batch Studies: Effect of pH: The effect of variation of the initial solution pH
(4.0–10.0) on the adsorption of arsenic is illustrated in Fig. 2. The
efficiency of removal of arsenic increases with an increase in pH from 4.0 to
8.0 and almost constant on further increase in pH up to 10.0. The maximum
arsenic removal efficiency at pH 7.0 is 79%. The adsorption capacity increases
with an increase in pH, may be due to acidic nature of adsorbent.
Figure.2: Effect of pH on arsenic adsorption by low
cost adsorbent. Effect of Contact Time: Fig. 3 demonstrates the effect of contact time (15–720
min) on the adsorption of arsenic. It is clear from Fig. 3 that with using
developed carbonaceous adsorbent with 200-250 mesh size, adsorption efficiency
increases rapidly with increase in contact time up to 180 min; and a maximum
removal efficiency of 80% was achieved and remained fairly constant up to the
end of the experiment. The results also show that most of the removal (60%)
occurs in a contact time of 60 min. The data in Fig. 3 also indicates that the
time required for equilibrium adsorption is 6 hr.
Figure.3: Effect of contact time on arsenic adsorption on
carbonaceous adsorbent (temperature, 45ºC; particle size 200-250 mesh). Effect of Initial Arsenic Concentration: The effect of initial arsenic concentration (100–1000
μg/l) on uptake by carbonaceous adsorbent is illustrated in Fig. 4, which
reveals that removal efficiency is higher (74.0%) with a lower initial Arsenic
concentration (100 μg/l). A gradual decrease in arsenic uptake by adsorbent was
observed at higher initial concentrations of arsenic. The maximum removal
efficiencies at an initial arsenic concentration of 1000 μg/L are 16% for
carbonaceous adsorbent. The reason for the decrease in arsenic adsorption
efficiency at higher initial concentrations may be that the adsorbents porous
nature with higher surface area eventually become saturated with adsorbed
arsenic and at this point further addition of arsenic to the solution would not
be expected to increase the amount adsorbed removed significantly.
Figure.4: Effect of initial concentration of arsenic
adsorption on carbonaceous adsorbent (temperature, 25ºC; particle size 200-250
mesh). Effect of Temperature: The adsorptions of arsenic at different temperatures
(298, 308 and 318 K) were studied. The adsorption was found to increase with
increase in temperature from 298 to 318K (Fig.5). It reveals that the adsorbent
system is exothermic in nature for which the evaluations of thermodynamic
parameters were carried out. The adsorption data fitted to two adsorption
models (Langmuir and Freundlish) to find out the suitable model.
Figure.5: Effect of temperature of arsenic
adsorption on carbonaceous adsorbent (particle size 200-250 mesh). However, from Fig.6, it is observed that the experimental
data is fitted in Langmuir model. The maximum adsorption capacity on Langmuir
model at temperature 313K was found 166.67 µg/g while, for Freundlich model was
3.78 µg/g . This indicates that the Langmuir model was best fitted than
Freundlich model.
Figure.6: Langmuir model fit for adsorption of
arsenic at 298K, 303K and 313K (particle size 200-250 mesh).
|
||||||
| Conclusion |
The study of removal of arsenic by adsorption is an important field of environmental science which is likely to be helpful in protecting society from toxic metal like arsenic. Water purification and removal of toxic materials is very essentials for human, animal and living organisms. The adsorption method developed using low cost adsorbent from fertilizer industry waste and can also tried and tested for application in field for removal of other heavy metals, toxic impurities from surface drinking water as well as ground water. The adsorption characteristics of arsenic were investigated under batch experiments at different initial arsenic concentrations, contact time, pH values, adsorbent dosage levels, different temperature and particle size of adsorbent. The following results were obtained:
1. The percent removal of arsenic was high with lower initial concentration of arsenic.
2. The arsenic removal increased sharply in the first several hours, after which the removal rate become slow, eventually reaching equilibrium after a contact time of 12 h.
3. The removal of arsenic from drinking water increased with increase the particle size 100-150 t0 200-250 mesh of the adsorbent. This is due to fact small particles have higher surface area.
4. The pH of solution influenced arsenic adsorption differently. Generally, arsenic was fairly well removed at a wide pH range (6.5–10). The optimum pH for As removal was found as 7.0.
5. The adsorption was found to increase with increased in temperature from 298 to 318K. It reveals that the adsorbent system is exothermic in nature. According to Langmuir isotherm model, an increase in the initial concentration of arsenic decreased the percentage of arsenic adsorbed, but increased the adsorption capacity. Whereas, an increase in adsorbent dosage led to an increase in the arsenic removal percentage, while decrease in adsorption capacity. The maximum arsenic removal capacity of developed low cost adsorbent was 166.67 µg/g for removal of arsenic from drinking water. The present studies have helped to achieve the arsenic concentration required for drinking water purposes as per Indian Standards (IS: 10500, 1999). |
||||||
| Acknowledgement | Authors are thankful to the University Grant Commission (UGC), New Delhi (India) for financial support through grant no. 8-2 (41)/2011(MRP/NRCB). | ||||||
| References | 1. S. Singh, K. C. Barick, and D. Bahadur, “Functional oxide nanomaterials and nanocomposites for the removal of heavy metals and dyes,” Nanomater. Nanotechnol., vol. 3, no. 1, pp. 1–19, 2013, doi: 10.5772/57237.
2. S. Hao, Y. Zhong, F. Pepe, and W. Zhu, “Adsorption of Pb2+ and Cu2+ on anionic surfactant-templated aminofunctionalized mesoporous silicas,” Chem. Eng. J., vol. 189– 190, pp. 160–167, 2012, doi: 10.1016/j.cej.2012.02.047.
3. S. Singh, K. L. Wasewar, and S. K. Kansal, Low-cost adsorbents for removal of inorganic impurities from wastewater. INC, 2020.
4. P. B. Tchounwou, C. G. Yedjou, A. K. Patlolla, and D. J. Sutton, Heavy Metals Toxicity and the Environment. Molecular, Clinical and Environmental Toxicology., vol. 3, pp 133-164, 2012, doi: 10.1007/978-3-7643-8340-4_6.
5. J. D. Hem, Study and interpretation of the chemical characteristics of natural water. U.S. Geological Survey Water-supply paper, pp 2254, 263, 1992.
6. Li, C.; Zhou, K.; Qin, W.; Tian, C.; Qi, M.; Yan, X.; Han, W. A review on heavy metals contamination in soil: Effects, sources, and remediation techniques. Soil Sediment Contam. Int. J. 2019, 28, 380–394.
7. C.G. Lee, J. W. Jeon, M. J. Hwang, K. H. Ahn, C. Park, J. W. Choi, S. H. Lee, Lead and copper removal from aqueous solutions using carbon foam derived from phenol resin. Chemosphere 2015, 130, 59–65.
8. P. Maneechakr, S. Karnjanakom, Adsorption behaviour of Fe(II) and Cr(VI) on activated carbon: Surface chemistry, isotherm, kinetic and thermodynamic studies. J. Chem. Thermodyn. 2017, 106, 104–112.
9. R. Petrus, J. K. Warchol, Heavy metal removal by clinoptilolite. An equilibrium study in multi-component systems. Water Res. 2005, 39, 819–830.
10. T. Bajda, Z. Klapyta, Adsorption of chromate from aqueous solutions by HDTMA-modified clinoptilolite, glauconite and montmorillonite. Appl. Clay Sci. 2013, 86, 169–173.
11. T. Bajda, B. Szala, U. Solecka, Removal of lead and phosphate ions from aqueous solutions by organo-smectite. Environ. Technol. 2015, 36, 2872–2883.
12. Y. He, Q. Q. Liu, J. Hu, C. X. Zhao, C. J. Peng, Q. Yang, H. L. Wang, H. L. Liu, Efficient removal of Pb(II) by amine functionalized porous organic polymer through post-synthetic modification. Sep. Purif. Technol. 2017, 180, 142–148.
13. Y. Y. Wang, Y. X. Liu, H. H. Lu, R. Q. Yang, S. M. Yang, Competitive adsorption of Pb(II), Cu(II), and Zn(II) ions onto hydroxyapatite-biochar nanocomposite in aqueous solutions. J. Solid State Chem. 2018, 261, 53–61.
14. J. G. Chen, H. N. Kong, D. Y. Wu, X. C. Chen, D. L. Zhang, Z. H. Sun, Phosphate immobilization from aqueous solution by fly ashes in relation to their composition. J. Hazard. Mater. 2007, 139, 293–300.
15. J. W. Lim, Y. Y. Chang, J. K. Yang, S. M. Lee, Adsorption of arsenic on the reused sanding wastes calcined at different temperatures. Colloids Surf. A Physicochem. Eng. Asp. 2009, 345, 65–70.
16. L. P. Lingamdinne, J. K. Yang, Y. Y. Chang, J. R. Koduru, Low-cost magnetized Lonicera japonica flower biomass for the sorption removal of heavy metals. Hydrometallurgy 2016, 165, 81–89.
17. D. Ocinski, I. Jacukowicz-Sobala, P. Mazur, J. Raczyk, E. Kociolek-Balawejder, Water treatment residuals containing iron and manganese oxides for arsenic removal from water—Characterization of physicochemical properties and adsorption studies. Chem. Eng. J. 2016, 294, 210–221.
18. M. Wołowiec, M. Komorowska-Kaufman, A. Pruss, G. Rzepa and T. Bajda, Removal of Heavy Metals and Metalloids from Water Using Drinking Water Treatment Residuals as Adsorbents: A Review. Minerals 2019, 9, 487; doi:10.3390/min9080487
19. Gupta, V.K., Saini, V.K., Jain, N.; Adsorption of As(III) from aqueous solutions by iron
oxide-coated sand. J. Colloid Int., 2005, 55;
20. V. K. Gupta, S .K. Srivastava, R. Tyagi, Design parameters for the treatment of phenolic wastes by carbon columns (obtained from fertilizer waste material). Water Res 2000, 34, 1543-1550.
21. M. S. M. Yusof et al., Arsenic adsorption mechanism on palm oil fuel ash (POFA) powder suspension, J. Hazard. Mater., 2020, 383, 121214; doi: 10.1016/j.jhazmat.2019.121214.
22. D. Mohan, C. U. Pittman Jr., Arsenic removal from water/wastewater using adsorbents—A critical review. J. Hazard. Mat., 2007, 142, 1-53; doi.org/10.1016/j.jhazmat.2007.01.006
23E. Meez, A. K. Tolkou, D. A. Giannakoudakis, I. A. Katsoyiannis, G. Z. Kyzas, activated Carbon for Arsenic Removal from Natural Waters and Wastewaters: A Review. Water, 2021, 13, 2982; doi.org/10.3390/w13212982
24. WHO (World Health Organisation), Environmental Health Criteria, 18: Arsenic, World Health Organisation, Geneva, 1981.
25. A. Bhatnagar, A. K. Jain, Column Studies of Phenols and Dyes Removal from Aqueous Solutions Utilizing Fertilizer Industry Waste. Int. J. Agri. Res. 2006, 1, 161-168; doi.org:10.3923/ijar.2006.161.168.
26. I. Langmuir, The adsorption of gases on plane surfaces of glass, mica and platinum,” J. Am. Chem. Soc., 1918, 40, 1361–1403.
27. H. M. F. Freundlich, Over the adsorption in solution. J. Phy. Chem., 1906, 57, 385–470.
28. L. Weerasundara, Y.-S. Ok, J. Bundschuh, Selective removal of arsenic in water: A critical review, Environmental Pollution, 2021, 268, 115668.
29. M. Victor-Ortega, H. Ratnaweera, Double filtration as an effective system for removal of arsenate and arsenite from drinking water through reverse
30. J. Guo, S. Luo, Z. Liu, T. Luo, Direct Arsenic Removal from Water Using Non-Membrane, Low-Temperature Directional Solvent Extraction, J. Chem. Eng. Data, 2021, doi.org/10.1021/acs.jced.9b00936 |
||||||
………………………………………………… (v)
