Adsorptive removal of Cr(III)–EDTA chelate from an aqueous solution by magnetic mesoporous silica microspheres

Abstract

Abstract The 3-aminopropyltrimethoxysilane-modified magnetic mesoporous adsorbent (FNMs/APTES) was synthesized and applied to remove Cr(III)–EDTA chelates from water. The characterization of FNMs/APTES showed that the prepared adsorbent with a magnetic mesoporous structure was successfully grafted by APTES, which has good stability under acid conditions. The maximum capacities of FNMs/APTES for Cr(III)–EDTA adsorption at 15, 25 and 35 °C and pH 4.0 were 12.58, 13.13 and 14.00 mg·g−1, respectively. The adsorption isotherm of FNMs/APTES for Cr(III)–EDTA conforms to the Freundlich model, and the adsorption kinetic model accords with the pseudo-second-order kinetic model. Adsorption of Cr(III)–EDTA on the adsorbent was not affected in the presence of Na+, K+ and Ca2+ even at 100 mmol·L−1. Cr(III)–EDTA was anchored on FNMs/APTES through electrostatic interaction between protonated amino groups of adsorbents and Cr(III)–EDTA anions, and Cr(III)–EDTA chelates were adsorbed as a whole on the adsorbent. The Cr(III)–EDTA-saturated adsorbent can be readily regenerated in HCl solution and 83.03% of the initial Cr(III)–EDTA adsorption capacity remains after four adsorption–regeneration experiment cycles. The results highlighted that the FNMs/APTES as a potential adsorbent can be applied for the minimization of Cr(III)–EDTA chelates from water.