Investigating the effect of Nitric acid (with different normalities) on the efficiency of scoria in Malachite removal from aquatic environments: determination of model, isotherms and reaction kinetics

Abstract

Background and Objective: Malachite, due to its features and low degradability, can be removed from aquatic environments with difficulty. Given the Nitric acid effect on the physical and chemical characteristics of scoria, this study was to evaluate the effect of sulfuric acid normality (1, 6 and 12) on the efficiency of scoria in Malachite removal from aquatic environments and to determine model, isotherms and reaction kinetics. Method: Adsorption processes were carried out in vitro at different pH values, adsorbent dosages, contact times and constant concentrations of the dye. Residual concentrations of dye was measured as 665 nm by a spectrophotometer (Cary 50 Perkin Elmer Co). In order to understand the adsorption process, the obtained data were fitted by the Langmuir, Freundlich isotherms, and pseudo-first and second-order kinetics. Findings: The results showed that the dye removal eas increased with the increase of acid normality, pH, adsorbent dosage and contact time. The highest efficiency (100%) was obtained for the adsorbent modified with sulfuric acid 6 and 12 normalities in pH =11, adsorbent dose of 1.4 g/L and contact time of 75 minutes. Adsorption data proper followed both the Langmuir isotherm, Freundlich adsorption and pseudo-second-order kinetic. Discussion and Conclusion: According to the results, it can be concluded that Malachite adsorption by scoria occurs in both multi-and mono-layerd forms and scoria treatment with Nitric acid, due to wide chemical changes (especially silica/alumina ratio) of adsorbent structure, increases the efficiency as compared to natural scoria