Removal of Cr(VI) ions from wastewater by sodium alginate-based polymers

Process wastes from industries such as metal plating, steelmaking, paint and pigment production, woodworking and leather tanning contain heavy metals in concentrations exceeding discharge limits. The adsorption method, which is used for the easy removal of these heavy metals, has become a focus in recent years due to its simple operation, the recyclability of heavy metal ions, the recyclability of adsorbents, and its effectiveness in the treatment of wastewater containing especially low concentrations of heavy metals. In the present study, cross-linked sodium alginate beads (CRSA) were modified in the presence of ethylenediamine (EDA) after grafting with glycidyl methacrylate (GMA) and the efficiency of the obtained product in Cr(VI) adsorption was investigated. In the study, as a result of differentiation of grafting reaction parameters for high graft efficacy, the CRSA-g-PGMA copolymer, which has 42% graft efficiency, was modified in the presence of EDA, and the characterization of the obtained products was carried out by FTIR and SEM analyzes. In the adsorption studies performed with the synthesized product, higher adsorption capacity was obtained at low pH. The adsorption capacity was 238.45 mg/g at the initiator concentration of 100 ppm, the adsorbent amount of 20 mg, the pH of 2, the contact time of 8 hours, and the reaction temperature at 25°C. Pseudo-first-order and pseudo-second-order kinetic models were used to determine the kinetic adsorption constants, and the pseudo-second-order model was found to be more suitable. Experimental data of adsorption equilibrium were evaluated with Langmuir and Freundlich isotherms in experiments carried out at different temperatures. The obtained results showed that the Langmuir isotherm model is more suitable. In addition, FTIR and SEM analyzes of Cr(VI) adsorbed polymer were also performed.