Removal of Phosphate from Aqueous Solutions Using a New Modified Bentonite-Derived Hydrogel

A bentonite-based hydrogel was chemically modified to prepare a new effective adsorbent for the removal of phosphate from aqueous solutions using batch equilibrium experiments at the laboratory scale. The efficiency of the phosphate adsorption by the modified adsorbents followed the order: Al-Fe-hydrogel>Al-hydrogel>Fe-hydrogel>Rewoquate surfactant-hydrogel. Irasoft congruent to surfactant-hydrogel>raw hydrogel. The amount of Fe and Al, as determined in proportion to the cation exchange capacity (CEC) of the hydrogel, was the most important parameter for optimizing the modification process by pillaring solutions. The results showed that the phosphate adsorption was rapid and pH independent. The removal of phosphate reached up to 99 % at the optimized conditions. The adsorption data were well fitted by Langmuir and Freundlich models. According to the Langmuir model, the maximum adsorption capacity of the phosphate on the Fe-Al-hydrogel was 14.29 mg L-1. The removal of phosphate from an urban wastewater using the modified adsorbent was more than 99 %. The Fe-Al-hydrogel selectively adsorbed the phosphate from the solutions containing sulphate, bicarbonate, chloride, and nitrate. Based on the obtained results, the synthesized adsorbent could be used effectively to decontaminate the phosphate polluted water.