Green synthesis of Pd@biochar using the extract and biochar of corn-husk wastes for electrochemical Cr(VI) reduction in plating wastewater

Abstract

In this study, Corn Husks, as an organic waste, were utilized to synthesize palladium nanoparticles (PdNPs) using a green approach and the related biochar as a support material for PdNPs to produce Pd@biochar nanocatalyst. Pd@biochar nanocatalysts were synthesized using the extracted liquid from corn husks and PdCl2 salt, and biochar was obtained by a hydrothermal process conducted on chapped corn husks. FESEM, UV-Vis, XRD, and FTIR were used to evaluate the physicochemical properties of the nanocatalyst and the formation of PdNPs using the implemented approach. The effect of the Pd@biochar mass ratio was explored, and nanocomposite with a mass of 0.06 palladium to biochar was the most favorable catalyst. The Design Expert software was applied to investigate and optimize the effect of parameters, such as pH, initial Cr(VI)concentration, and contact time, using the Response Surface Box Behnken method. The proposed model of Design Expert software indicated a 99.9% reduction of Cr(VI) at optimum conditions ( pH=1, initial Cr(VI) concentration= 100 mg L-1, contact time= 60 min). The kinetics of the electrochemical reaction showed a high correlation with the pseudo-first-order model at different concentrations of Cr(IV). The applicability of synthesized nanocatalyst in six cycles of the experiment was tested, and results pointed out only a 10% decrease in nanocatalyst efficiency, proving its high stability. The electrochemical reduction of Cr(VI) in real plating wastewater was investigated at optimum conditions, which resulted in a 99.7% reduction and 0.35 mg L-1 residual of Cr(IV), reaching Iran’s standard for industrisal wastewater discharge.