Adsorption behaviors of hazardous methylene blue and hexavalent chromium on novel materials derived from Pterospermum acerifolium shells

Abstract

Heavy metal and dye are diffused pollutants in the wastewater, which impose a serious threat to the environment. Adsorption is the unconventional technique used for the sequestration of wastewater contaminants. Adsorbents prepared from Pterospermum acerifolium shells were successfully used for the first time for removing methylene blue and hexavalent chromium from aqueous solutions in a batch system. The effect of sulfuric acid, phosphoric acid treatments on Pterospermum acerifolium shells (SPAS, PPAS) and its native form (PAS) was investigated on the adsorption process. The influences of the solution pH (2.0–10.0), adsorbent dosage (0.01–0.1g), initial MB, Cr(VI) concentrations (50–250mg/L), and temperature (303−323K) were examined for the removal process. Thermodynamic parameters were estimated for the thermodynamical modeling of the adsorption processes. Langmuir isotherm model better described the MB and Cr(VI) removal process. The maximum adsorption capacity achieved was 125mg/g (PAS), 166.66mg/g (SPAS), and 250mg/g (PPAS) for MB removal and for Cr(VI) was 76.92mg/g (PAS), 142.85mg/g (SPAS), and 111.11mg/g (PPAS), respectively. The experimental data as a function of contact time was modeled using the adsorption kinetic equations of pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion models. The experimental adsorption data best correlated to pseudo-second order model. The shells of Pterospermum acerifolium are an efficient precursor for the preparation of adsorbents (PAS, SPAS, PPAS), successfully applied for the removal of methylene blue and hexavalent chromium from aqueous solutions.