Adsorptive performance of tetracarboxylic acid-modified magnetic silica nanocomposite for recoverable efficient removal of toxic Cd(II) from aqueous environment: Equilibrium, isotherm, and reusability studies

Herein, mesoporous magnetic nanocomposite (Fe3O4@SBTCA) was specifically designed and fabricated for its high efficient application in the removal of toxic Cd(II) ions from aquatic environment. The struc- ture, surface characteristics, and composition of the magnetic nanocomposites were characterized by FT- IR, BET analysis, XRD, TEM, EDX, Zeta potential measurement and TGA analysis. TEM images and XRD exhibited the average particle size of Fe3O4@SBTCA nanocomposite was less than 22 nm. The impact of different variables on the Cd(II) adsorption were explored using batch method and the findings revealed that the highest adsorption capacity was 158.68 mg/g achieved at pH 7.5 and solution temperature of 25 C after 120 min agitation at 100 rpm. Nonlinear Elovich models of pseudo first-order and pseudo second-order equations were applied to study the adsorption kinetics and the results reveal that the pseudo first order kinetics was the best to describe the adsorption kinetics. The results of isotherm adsorption modeling reveal that the non-linear Freundlich isotherm could fit the data better than others, such as Dubinin Radushkevich and Langmuir models, indicating the Cd(II) adsorption on Fe3O4@SBTCA was physisorption in nature. The thermodynamic analysis verified that the adsorption process was exothermic. The Fe3O4@SBTCA showed good recoverable efficiency up to four times of recycling.