8.4.2 Arsenic Removal from Contaminated Soils
There are many arsenic removal approaches that could be divided primarily into
three categories, physical, chemical, and biological (Lim et al. 2014).
8.4.3 Physical Approach
One of the popular approaches is, mixing both the uncontaminated and contaminated
soils together till the arsenic concentration reaches an acceptable level (Lim et al.
2014; Mahimairaja et al. 2005). Soil washing is a physicochemical approach
whereby the soil contaminated with arsenic is washed in presence of chemicals
such as sulphuric/nitric/phosphoric acids, and/or hydrogen bromide (Lim et al.
2014).
8.4.4 Chemical Approach
The chemical approach employed for the purpose as extractant is costly and often is
restricted to soil washing at smaller-scale operations (Mahimairaja et al. 2005).
Cement could also immobilise soluble Arsenites and has been successfully used to
stabilise arsenic-rich sludge (Sullivan et al. 2010). Furthermore, additives, such as,
surfactants, cosolvents, etc. could also enhance the soil flushing efficiencies using
aqueous solutions. Surfactant alone was about 80–85% efficient in laboratory
conditions, while more complex processes such as polymer injection enhanced the
efficiency (Atteia et al. 2013). Available chemical remediation approaches involve
methods such as adsorption by using specific media, immobilisation, modified
coagulation along with filtration, precipitations, immobilisations and complexation
(Duarte et al. 2009; Mahimairaja et al. 2005). Coagulation along with filtration for
arsenic removal is quite economical but often displayed lower (<90%) efficiencies
(Lim et al. 2014).
8.4.5 Biological Approach
Biological measures are broadly distinguished as phytoremediation and microbiallymediated remediation. Plants and microbes, especially the ones thriving in arsenicrich environment, have evolved themselves to sustain and metabolise arsenic and
their metalloids. Some bacteria convert the inorganic and organic arsenic to
trimethyl-arsine (less toxic gaseous arsenic), particularly under anaerobic conditions.
This could be accomplished through various ways including biomethylation,
8 Arsenic Contamination: Sources, Chemistry and Remediation Strategies
225
There are many arsenic removal approaches that could be divided primarily into
three categories, physical, chemical, and biological (Lim et al. 2014).
8.4.3 Physical Approach
One of the popular approaches is, mixing both the uncontaminated and contaminated
soils together till the arsenic concentration reaches an acceptable level (Lim et al.
2014; Mahimairaja et al. 2005). Soil washing is a physicochemical approach
whereby the soil contaminated with arsenic is washed in presence of chemicals
such as sulphuric/nitric/phosphoric acids, and/or hydrogen bromide (Lim et al.
2014).
8.4.4 Chemical Approach
The chemical approach employed for the purpose as extractant is costly and often is
restricted to soil washing at smaller-scale operations (Mahimairaja et al. 2005).
Cement could also immobilise soluble Arsenites and has been successfully used to
stabilise arsenic-rich sludge (Sullivan et al. 2010). Furthermore, additives, such as,
surfactants, cosolvents, etc. could also enhance the soil flushing efficiencies using
aqueous solutions. Surfactant alone was about 80–85% efficient in laboratory
conditions, while more complex processes such as polymer injection enhanced the
efficiency (Atteia et al. 2013). Available chemical remediation approaches involve
methods such as adsorption by using specific media, immobilisation, modified
coagulation along with filtration, precipitations, immobilisations and complexation
(Duarte et al. 2009; Mahimairaja et al. 2005). Coagulation along with filtration for
arsenic removal is quite economical but often displayed lower (<90%) efficiencies
(Lim et al. 2014).
8.4.5 Biological Approach
Biological measures are broadly distinguished as phytoremediation and microbiallymediated remediation. Plants and microbes, especially the ones thriving in arsenicrich environment, have evolved themselves to sustain and metabolise arsenic and
their metalloids. Some bacteria convert the inorganic and organic arsenic to
trimethyl-arsine (less toxic gaseous arsenic), particularly under anaerobic conditions.
This could be accomplished through various ways including biomethylation,
8 Arsenic Contamination: Sources, Chemistry and Remediation Strategies
225