Synthesis and characterization of thiazolidinone -functionalized MCM-41 and kaolinite nanocomposites as the powerful and new adsorbents for heavy metal removal: process optimization using RSM-CCD

Abstract

Core – shell magnetic nanoparticles MCM-41 and nano-clays are working absorbents for elimination of heavy metal ions. Nanoparticles Fe₃O₄ are made by sol- gel method and are covered by silica and their surfaces are modified with suitable organic compounds. Organic clays also are one of usual absorbents which absorb diverse spectrum of organic pollutants and adsorption function of these compounds is relating to interlayer structure and their surface modification. In present research, for the first time, Kaolinite-NH₂@thiazolidinone and Fe₃O₄@MCM-41-NH₂@thiazolidinone nanocomposites were prepared and after structural approval by FTIR, VSM, XRD, SEM, TGA, BET, EDX technics, were used for adsorption of \({\mathrm{Pb}}^{2+}\) and Cd²⁺ from aqueous medium as an active absorbent. to urgent elimination and active heavy metal ions in aqueous solutions, MCM-41 and Kaolinite were modified with (3-aminopropyl) trietoxysilane (APTES) and then during a three-step reaction in condition without solvent with thioglycolic acid and benzaldehyde were reacted and finally, thiazolidinone was synthetized on their surfaces. Adsorption process and different conditions of absorbent dose, metal ion concentration, time and pH have been studied. For optimization conditions, method of response surface (RSM) has been used. 120 tests with two synthetic absorbents were performed for adsorption of Pb²⁺ and Cd²⁺, which most capacity of adsorption with the use of Fe₃O₄@MCM-41-NH₂@thiazolidinone was 768.25 mg/g in pH = 5 and 341.5 mg/g in pH = 7.5, respectively. Also, results indicated that most capacity of adsorption with the use of Kaolinite-NH₂@Thiazolidin for elimination of Pb²⁺ and Cd²⁺ were 552.81 mg/g in pH = 6.5 and 393.21 mg/g in pH = 7.5. Effect of pH, time, absorbent dose, and initial concentration of cations lonely and effect of their simultaneously in adsorption capacity and elimination percentage were evaluated.

Graphical Abstract