Fabrication of alginate/humic acid/Fe-aminoclay hydrogel composed of a grafted-network for the efficient removal of strontium ions from aqueous solution

A polymer hydrogel composed of alginate/humic acid/Fe-aminoclay was fabricated and utilized as a potential adsorbent for the removal of strontium ions (Sr²⁺) from aqueous solution. The effects of adsorbate concentration, reaction pH, and time on the removal efficiency of Sr²⁺ were investigated. The results revealed that the adsorption capacity increases as the Sr²⁺ concentration increased from 1 to 10 ppm, which might be due to the more available adsorption sites. An additional increase in the Sr²⁺ concentration had no effect. The optimal pH and reaction time for the removal of Sr²⁺ were identified as pH 7 and 24 h, respectively, with an adsorbent dosage of 20 mg. The adsorption isotherm was fitted to the Freundlich model with a maximum Sr²⁺ adsorption capacity of 45.65 mg g⁻¹. The kinetic study showed that the adsorption behavior followed a pseudo-second-order kinetics. The hydrogel showed good selectivity toward Sr²⁺ even in the presence of competitive cations having a higher concentration than Sr²⁺. From the above results, it is expected that this biocompatible hydrogel material can be used as an adsorbent for the removal of radioactive strontium.