Removal of Hg²⁺ by carboxyl-terminated hyperbranched poly(amidoamine) dendrimers grafted superparamagnetic...

In this research, carboxyl-terminated hyperbranched poly(amidoamine) dendrimers grafted superparamagnetic nanoparticles (CT-HPMNPs) with core-shell structure were synthesized by the chemical co-precipitation method, the core of superparamagnetic iron oxide nanoparticles and a shell of polyamidoamines (PAMAM) and carboxyl groups, as a novel adsorbent for removing Hg²⁺ from aqueous systems. The surface of the particles was modified by 3-(aminopropyl) triethoxysilane, and finally, PAMAM and carboxyl dendrimers were grown on the surface up to 5.5 generation. The synthesized polymer was characterized physically and morphologically using different techniques. Also, they were evaluated in terms of adsorption capacity to remove inorganic pollutants of Hg²⁺, selectivity, and reusability. The adsorption mechanism Hg²⁺ onto CT-HPMNPs was investigated by single-step and two-step isotherms that the adsorption capacity of Hg²⁺ obtained 72.3 and 32.88 mg g^-1 respectively at pH 5, adsorbent dosage 2 g L^-1, Hg²⁺ initial concentrations 20 mg L^-1, contact time 60 min, and temperature of 298 K by CT-HPMNPs. Also, the kinetics of Hg²⁺ followed the pseudo-second-order model and adsorption isotherms of Hg²⁺ onto CT-HPMNPs were fitted well by Freundlich (as a single-step) and two-step adsorption models with a correlation coefficient of 0.9997 and 0.9999 respectively. The results showed a significant potential of Hg²⁺ ions removing from industrial wastewater and spiked water by CT-HPMNPs.