Acid induced arsenic removal from soil amended with clay-biochar composite

Phytoremediation itself is not efficient enough to remove As from soil as all As bound fractions are not available for plants. Therefore, the use of extracting agent has been common. However, in general high potential for extraction have been seen by extracting agents like EDTA which is recognized as somewhat toxic. Not many studies showed the potential of organic acids with composites enhancing the extracting capacity. Therefore, three organic acids; acetic, citric and oxalic, and three inorganic acids; sulfuric, nitric, hydrochloric, were used to evaluate the desorption capacity of As into the soil solution from As contaminated soil together with two types of modified BC composites; Biochar-montmorillonite (BC-MT) and Biochar-Natural Red-Earth (BC-RE). Citric acid showed the better performance with As release compared to all other organic and inorganic acids which is 60% of the aqua regia digested arsenic in soil at highest acid concentration of 10 mM. The use of BC composites further enhanced the capability of As desorption with citric acid. The biochar-montmorillonite (BC-MT) composite showed 90% of desorption capacity with citric acid and for biochar-red earth (BC-RE) composite it was a 95% of escalation. Therefore, the citric acid with the presence of BC-MT and BC-RE composites have higher capacity to enhance the As desorption from As contaminated soils.