Investigation of Mercury(II) and Arsenic(V) adsorption onto sulphur functionalised pumice: a response surface approach for optimisation and modelling

Recently, millions of people are under the harmful influences of seriously toxic metals, all of which lead to irreversible damages to nature and living species' health. Therefore, the development of novel adsorbents with high affinity for target metals is critical to their removal from aqueous media. In this study, the effect of initial metal concentration (C-o), initial pH, adsorbent dosage and contact time for Hg(II) and As(V) adsorption were investigated using the Central Composite Design. In this context, pumice minerals with surface enriched by -SH groups(P-SH) were prepared with an effective and simple chemical method. As a result of the experimental studies, the optimum points for parameters affecting the adsorption of both metals were obtained with the model equation produced via Response Surface Methodology (RSM). With the numerical optimisation, the optimum values for Hg(II) removal were 6.33, 36.94 mg/L, 0.15 g and 120 min., and the optimum values for As(V) removal were 3.94, 7.17 mg/L, 0.15 g and 155.4 min. for initial pH, C-o, adsorbent dosage, and contact time, respectively. Hg(II) and As(V) adsorption yield in the obtained optimum conditions were determined as 92.14% and 88.02%, respectively. Under the optimum conditions, kinetic and isotherm studies were carried out for adsorption of both metals with P-SH. It was observed that the adsorption kinetics data for both metals were consistent with the pseudo-second-order equation and equilibrium data compatible with Freundlich and Langmuir isotherm models.Given all this, P-SH is thought to have potential applications for removing heavy metals from wastewater and will have important contributions to similar studies to be conducted.