Facile Synthesis of Acyl-Hydrazone Composites Based on Hydrazide-Modified Formylated Polystyrene for Effective Removal of Heavy Metal Ions and Sulfides from Water

In this study, waste polystyrene was modified and upgraded to prepare formylated polystyrene, and the modified polystyrene acetyl hydrazone (LT-HPA) was synthesized by condensation with polymethyl-propionyl-hydrazine. It is proven that the modification of the adsorption material is successful by various characterization methods. In the subsequent pollutant removal study, pH, mass, concentration, contact time, and salt ion interference were investigated. The optimal pH for Cu(II) and sulfide removal was 5 and 11, respectively, and the optimal mass of adsorbent was 1 g/L. It was found that the maximum removal rate of Cu (II) was 231.51 mg/g. The adsorption equilibrium time was less than 40 min. This is due to the good adsorption activity of acyl hydrazide groups on the skeleton for Cu (II) through coordination. The maximum desulfurization amount in 60 min was 370.21 mg/g, which was mainly caused by the oxidation of sulfides by surface oxidizing groups. Isotherm and kinetic studies show that the adsorption processes of Cu (II) and sulfides are consistent with the Langmuir model and pseudo-second-order kinetic model. Thermodynamic parameters show that the removal of Cu (II) and sulfides is a spontaneous endothermic process. The adsorption mechanism is mainly chemical adsorption, supplemented by physical adsorption. After 10 regenerated adsorption/desorption cycles, the removal rates of Cu (II) and sulfides remained above 85%, indicating that polystyrenesulfonate acetylhydrazone (LT-HPA) adsorption materials have good reusability. In addition, the adsorbent has good thermal stability, salt resistance, and environmental friendliness. In summary, the modified formylated polystyrene acetyl hydrazone (LT-HPA) has a good application prospect in the removal of copper(II) and sulfides and provides a fresh way for upgrading polystyrene.