electrostatic force and/or van der Waals force between the adsorbent surface ions and
adsorbate molecules. Therefore, it is highly imperative to find the surface properties
of adsorbent first (e.g., polarity and surface area) before to consider in adsorption
process (Choong et al. 2007).
There are many different adsorbents has been utilized for the adsorption process
as appeared in Table 6.8. The absorbents are coal, activated carbon, fly ash,
kaolinite, red mud, montmorillonite, zeolites, goethite, iron hydroxide, chitosan,
zero-valent iron, titanium dioxide, cation-exchange resins and activated alumina.
Among these absorbents, the Table 6.8 outlines that iron-based adsorbents in
adsorption process is an emergent strategy for the removal process of arsenicpolluted water. The iron based adsorbents works very well because of the higher
affinity towards inorganic arsenic (Gupta et al. 2012). Iron could expel arsenic from
water either by behaving as a reductant, acting as a absorbent, contaminantimmobilizing or co-precipitant (Mondal et al. 2013).
There are many reports available in adsorption process and considered as the
extensively used method for the removal of arsenic from contaminated water
because of its multiple advantages such as high efficiency in removing arsenic
(Singh and Pant 2004; Mohan and Pittman 2007), easy handling and operation
(Jang et al. 2008), cost-viability (Anjum et al. 2011), and no sludge generation
(Singh et al. 2015). However, the maximum adsorption efficiency relies upon the
concentration of system and operating pH. At lower pH, As (V) adsorption is good,
while, for As (III), most extreme adsorption can be acquired between pH 4 and
9 (Lenoble et al. 2002). In addition, the competing ions, for example, silicate, and
phosphate, also present in the arsenic contaminated water which should be consider
for the adsorption locations (Giles et al. 2011). Besides the conditions of system, the
viability of arsenic adsorption can likewise be delayed by the kind of adsorbent
itself. In Table 6.8, various adsorbents have been reported for the expulsion of
arsenic with different adsorbent loading. However, traditional adsorbents shows
intermittent pore structures and low explicit surface areas, prompting lower adsorption limits. Absence of selectivity, feeble connections with metallic ions and recovery challenges can likewise limit the capacity of these sorbents in bringing arsenic
concentration down to levels lower than MCL (Habuda-Stanić and Nujić 2015;
Samiey et al. 2014).
Table 6.9 gives brief depictions of arsenic removal technology, where the correlation among those ordinary arsenic removal innovations along with their removal
viability and operational expenses are outlined in Table 6.10 (Mohan and Pittman
2007; Tuutijärvi 2013).
Among the previously mentioned innovations talked about up until now, adsorption is considered as the best for the treatment of water and wastewater as far as
accommodation, benefit, plan and critical arsenic expulsion effectiveness. Also, it is
most reasonable because of the accessibility of a wide scope of adsorbents.
6 Metal Oxides for Removal of Arsenic Contaminants from Water
165
adsorbate molecules. Therefore, it is highly imperative to find the surface properties
of adsorbent first (e.g., polarity and surface area) before to consider in adsorption
process (Choong et al. 2007).
There are many different adsorbents has been utilized for the adsorption process
as appeared in Table 6.8. The absorbents are coal, activated carbon, fly ash,
kaolinite, red mud, montmorillonite, zeolites, goethite, iron hydroxide, chitosan,
zero-valent iron, titanium dioxide, cation-exchange resins and activated alumina.
Among these absorbents, the Table 6.8 outlines that iron-based adsorbents in
adsorption process is an emergent strategy for the removal process of arsenicpolluted water. The iron based adsorbents works very well because of the higher
affinity towards inorganic arsenic (Gupta et al. 2012). Iron could expel arsenic from
water either by behaving as a reductant, acting as a absorbent, contaminantimmobilizing or co-precipitant (Mondal et al. 2013).
There are many reports available in adsorption process and considered as the
extensively used method for the removal of arsenic from contaminated water
because of its multiple advantages such as high efficiency in removing arsenic
(Singh and Pant 2004; Mohan and Pittman 2007), easy handling and operation
(Jang et al. 2008), cost-viability (Anjum et al. 2011), and no sludge generation
(Singh et al. 2015). However, the maximum adsorption efficiency relies upon the
concentration of system and operating pH. At lower pH, As (V) adsorption is good,
while, for As (III), most extreme adsorption can be acquired between pH 4 and
9 (Lenoble et al. 2002). In addition, the competing ions, for example, silicate, and
phosphate, also present in the arsenic contaminated water which should be consider
for the adsorption locations (Giles et al. 2011). Besides the conditions of system, the
viability of arsenic adsorption can likewise be delayed by the kind of adsorbent
itself. In Table 6.8, various adsorbents have been reported for the expulsion of
arsenic with different adsorbent loading. However, traditional adsorbents shows
intermittent pore structures and low explicit surface areas, prompting lower adsorption limits. Absence of selectivity, feeble connections with metallic ions and recovery challenges can likewise limit the capacity of these sorbents in bringing arsenic
concentration down to levels lower than MCL (Habuda-Stanić and Nujić 2015;
Samiey et al. 2014).
Table 6.9 gives brief depictions of arsenic removal technology, where the correlation among those ordinary arsenic removal innovations along with their removal
viability and operational expenses are outlined in Table 6.10 (Mohan and Pittman
2007; Tuutijärvi 2013).
Among the previously mentioned innovations talked about up until now, adsorption is considered as the best for the treatment of water and wastewater as far as
accommodation, benefit, plan and critical arsenic expulsion effectiveness. Also, it is
most reasonable because of the accessibility of a wide scope of adsorbents.
6 Metal Oxides for Removal of Arsenic Contaminants from Water
165