The effect study of Acetic acid on the scoria performance in removing of Malachite from aquatic environments: Determination of model, isotherms and reaction kinetics

Background and aim: Malachite due to its structural features and low degradability can be difficult in aquatic environments. Given the acetic acid effect on the physical and chemical characteristics of scoria, this study was aimed to evaluate acetic acid on the scoria performance in removing of Malachite from aquatic environments. Methods: This is lab scale study that carried out in vitro at different pH, adsorbent dosage, contact time and constant concentration of the dye. Residual concentrations of dye were measured in 665 nm. In order to understand adsorption process, obtained data were fitted by the Langmuir, Freundlich isotherms, and pseudo first and second order kinetics. Data were analyzed by design of experiments software (DOE). Results: The results showed that removing of dye increased with increasing of acid normality, pH, adsorbent dosage and contact time. The highest efficiency (100%) obtained for the modified adsorbent with Acetic acid 12 normality in pH=11, of adsorbent dose=1.4 g/L and contact time of 75 minutes. Adsorption data were proper obeyed from both the Langmuir isotherm and Freundlich adsorption and pseudo-second-order kinetic. Conclusion: According to the results, it can be concluded that Malachite adsorption by scoria occurs as both multi and mono layer and scoria treatment with acetic acid, due to wide chemical changes (especially silica/ alumina ratio) of adsorbent structure cause the increasing efficiency of its than natural scoria.