Anionic competition on arsenate removal by modified granular ferric hydroxide adsorbent

Abstract

The presence of inorganic forms of arsenic in water causing a serious threat to human health. Exposure of arsenic can cause serious diseases such as skin discoloration, cancer of skin, kidney and lung, blood vessel diseases, high blood pressure, and reproductive disorders. Removal of arsenic to provide safe drinking water was conducted to investigate the effects of individual and combined anions (sulphate, nitrate, phosphate, and chloride ions) on the arsenate adsorption capacity of modified granular ferric hydroxide adsorbent in batch experiments. The observed adsorption data fit the Langmuir model well. The presence of sulphate (400 mg/l), nitrate (15 mg/l), and chloride (250 mg/l) ions did not significantly affect the arsenate adsorption and the maximum adsorption capacity of arsenic was reduced by less than 5%. In contrary, phosphate ions showed strong competition for the adsorption process as the maximum adsorption capacity of the material was reduced by 59.8 and 73% at concentrations of 0.2 and 0.5 mg/l, respectively. The results also showed that phosphate anions were slightly preferable than arsenate in their competitive adsorption by the adsorbent.