The Sustainable Development is the blueprint to achieve a better and more sustainable future for all. It addresses the global challenges we face, including poverty, inequality, climate change, environmental degradation, peace and justice etc. The world’s water related ecosystems are being degraded at an alarming rate.  To resolve this issue, UNDP set SDG-6 (Clean water and sanitation) to achieve by 2030. Clean water supply for all the population is the basic duty of all the concerning authorities.

Ground water has steadily emerged as the backbone of World’s agriculture and drinking water security. Contribution of ground water is nearly 62% in irrigation, 85% in rural water supply and 50% in urban water supply in India. Ground water is an annually replenish able resource but its availability is non- uniform in space and time. Ground water available in the zone of water level fluctuation is replenished annually with rainfall being the dominant contributor. Hence, the sustainable utilization of ground water resources demands a realistic quantitative assessment of clean ground water availability in this zone based on reasonably valid scientific principles. Arsenic contamination in ground water is a very well-known pollution in the world. It causes serious human health illness. So that arsenic detection processes and removal techniques are very important topics. The present note is a brief idea on the removal of arsenic from drinking water.

Remediation of arsenic is possible by the following i) measurement, ii) mitigation and iii) management. Measurement is the critical step for developing the mitigation approaches (Marrazza et al. 2000). To overcome toxicity of arsenic, it is necessary to develop efficient remediation technology with novel low-cost materials.

Arsenic contamination is found not only in drinking water, but also in industrial wastewater i.e. effluents from various industries. The major sources of arsenic are metallurgical industries, glassware and ceramic production, tannery operation, dyestuff, pesticide industries, some organic and inorganic chemical manufacturing, petroleum refining, and rare earth metals [1]. These effluents contain relatively higher As (V) compared to As (III) concentration. Thus, researchers have been trying to remove arsenic from the drinking water as well as industrial effluents [2]. During removal of arsenic from drinking water, the general technique followed is to first oxidize As (III) to As(V) which is generally adsorbed more (compared to arsenate) in common arsenic adsorbents [3]. Existing technologies for arsenic remediation are: oxidation/precipitation, coagulation/precipitation, Nano filtration, reverse osmosis, electro dialysis, adsorption, ion exchange foam flotation, solvent extraction, and bioremediation [4] . The advantages and disadvantages of the methods are described in (Table 1).

Table 1: Comparison of arsenic removal techniques (Saha and Sarkar, 2012).

Among various processes of arsenic removal, adsorption technology is mostly utilized because it can remove the disadvantages of conventional methods. Its simplicity, ease of operation and handling, regeneration capacity, and sludge-free operation have made adsorption the preferred choice for researchers [9].

Adsorption is a surface phenomenon and efficiently utilized for organic and inorganic pollutants removal. When an adsorbable solute comes in contact with a solid with a highly porous surface structure, liquid–solid intermolecular forces of attraction cause some of the solute molecules from the solution to interact or get deposited at the solid surface [8]. With time an equilibrium of adsorption between the solute (adsorbate) and adsorbent is attained. The adsorption amount (qe, mmol g⁻¹) of the molecules at the equilibrium step is determined according to the following equation:

q_e = V (Co-Ce) /M (Equation 1)

Where V is the solution volume (L); M is the mass of adsorbents (g); and Co and Ce are the initial and equilibrium adsorbate concentrations, respectively.

Adsorption is a mass transfer process. In this process a substance is transferred from the liquid phase to the surface of a solid, and gets bound to the surface by physical and/or chemical interactions. Large surface area results in high adsorption capacity and surface reactivity.

Polymer         

Synthetic ion exchange resins are widely used in water treatment. They can remove many undesirable dissolved solids from water. These resins usually have a cross-linked polymer skeleton, known as the ‘matrix’. Usually this matrix is made of polystyrene cross-linked with divinylbenzene. Several biopolymers have been reported for the remediation of arsenic [9]. Zouboulis et al prepared iron oxide containing alginate beads for removal of arsenic [10].  Guo et al. developed iron oxyhydroxide loaded cellulose for arsenic removal from ground water.

Nanoparticle

Nowadays nanotechnology is playing a crucial role in providing clean and affordable drinking water. Environmental nano technologies for the treatment of arsenic have drawn attention in the recent years. Although the area of nanoscience is relatively new, it is playing an important role in the development of novel arsenic removal processes [11].

Large surface area, high specificity, high reactivity, and catalytic potential make nanomaterials excellent choice for water treatment.

However, a stabilizer or surface modifier is necessary to prevent the agglomeration into micron-scale or larger aggregates, resulting in reduction in the specific surface area and adsorption capacity. Stabilizers such as, starch and carboxymethyl cellulose are used to control the size of various metal and metal oxide-based nanoparticles [12]. The use of polymeric stabilizers can make the nanoparticles fully dispersible in water.

The use of metal, metal oxides, mixed metal nanoparticles are commercially available and low-cost nanoparticle-impregnated adsorbents, nanotubes, and various nanocomposites have been reported by various researchers. Among the various nanoparticles, magnetic nanoparticles such as nano-zero valent iron (nZVI), magnetite (Fe₃O₄), and maghemite (γ-Fe₂O₃) nanoparticles, TiO₂ based nanoparticles and other metal based nanoparticles e.g. ceria, cupric oxide, aluminium oxide, zirconium oxide have been widely used in research and engineering applications for the treatment of contaminated water [13-15].

For arsenic removal from water several oxide-based adsorbents such as, activated alumina, activated carbon [16], iron- and manganese-coated sand, kaolinite clay, hydrated ferric oxide, activated bauxite, titanium oxide, cerium oxide has been utilized and published in literature.

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