Development of the adsorption capability of MCM-41 particles synthesized at room temperature using 8-hydroxyquinoline-5-sulfonic acid for removal of Co(II) and Cr(VI) in binary systems

Abstract

A novel MCM-41 material containing 8-hyrdoxyquinoline-5-sulfonic acid (HQS/MCM-41) synthesized by in-situ coprecipitation of 8-HQS into MCM-41 was developed in this study. The performance of HQS/MCM-41 as a dual-function material for simultaneous adsorption of Co(II) cations and Cr(VI) anions was evaluated. The results showed that 8-HQS-free MCM-41 has the ability to adsorb Cr(VI) anions while failed in case of Co(II) cations. By using HQS/MCM-41, almost complete removals are achieved for both Co(II) and Cr(VI) in binary systems in pH ranges 3.5–8.5 and 3–4.3, respectively, which reflected the importance of the developing agent 8-HQS. Both Lagergren’s pseudo-first-order and Ho’s pseudo-second-order kinetic models succeeded to describe the kinetic data of Cr(VI) anions while those of Co(II) cations are better fitted by Lagergren’s model. Equilibrium isotherms of Co(II) and Cr(VI) ions are better described by Temkin and Freundlich isotherm models, respectively. Adsorption capacities of Co(II) and Cr(VI) using HQS/MCM-41 are compared with those reported in literature using other materials. The radiation and thermal stability of the synthesized material were further evaluated. Desorption of Co(II) and Cr(VI) loaded onto HQS/MCM-41 was tested using different inorganic and organic desorbing agents. Eventually, the adsorption mechanism of Co(II) and Cr(VI) ions onto HQS/MCM-41 was suggested.