Thermodynamic Studies of the Arsenic Adsorption on Iron Species Generated by Electrocoagulation

Table 1

Comparison of conventional processes for as removal [12, 13].

Technologies	Advantages	Disadvantages	% Removal
Oxidation/precipitation
Air oxidation	Relatively simple, low-cost but slow process	Mainly removes arsenic (V) and accelerate the oxidation process	80%
	In situ arsenic removal
	Also oxidizes other inorganic and organic constituents in water
Chemical oxidation	Relatively simple and fast process	Efficient control of the pH and oxidation step is needed	90%
	Oxidizes other impurities and kills microbes
	Minimum residual mass
Coagulation/coprecipitation
Alum coagulation	Relatively low capital cost and simple in operation	Produces toxic sludges	90%
	Durable powder chemicals are available	Low removal of arsenic
	Effective over a wider range of pH	Preoxidation may be required
Iron coagulation	Common chemicals are available	Medium removal of As (III)	94.5%
	More efficient than alum coagulation on weigh basis	Sedimentation and filtration needed
Lime softening	Most common, chemicals are available commercially	Readjustment of pH is required	91%
Sorption techniques
Activated alumina	Relatively well known and commercially available	Needs replacement after 4 to 5 regeneration	88%
Iron-coated sand	Expected to be cheap	Yet to be standardized	93%
	No regeneration is required	Produces toxic solid waste
	Remove both As (III) and As (V)
Ion exchange resin	Well-defined medium and capacity	High cost	87%
	The process is less dependent on pH of water	Requires high tech operation and maintenance
	Exclusive ion specific resin to remove arsenic	Regeneration creates a sludge disposal problem
		As (III) is difficult to remove
		Life of resins
Membrane techniques
Nanofiltration	Well-defined and high removal efficiency	Very high capital cost	95%
		Preconditioning
		High water rejection
Reverse osmosis	No toxic solid waste is produced	High tech operation and maintenance	96%
Electrodialysis	Capable of removing other contaminants	Toxic wastewater produced	95%