Intensified adsorption of chromium (VI) by catalpa-activated carbon from water and real electroplating industry wastewater

In the present study, a novel adsorbent, activated carbon produced from the catalpa tree fruit was evaluated for adsorption of Cr (VI) from water and real electroplating wastewater. The batch adsorption experiments were conducted to investigate the impact of various operational variables, namely contact time, pH, initial concentration of Cr (VI), and the dose of activated carbon. Experimental data were used to determine the most suitable isotherm and kinetic models. The optimal values of the process were identified at a contact time of 150 min, a pH 2, an initial Cr (VI) concentration of 40 mg/L, and an adsorbent dose of 0.6 g/L that led to mean Cr (VI) removal of 95% with adsorption capacity (q) equal to 75 mg/g. The Langmuir isotherm and pseudo-first-order kinetic models could well explain the adsorption equilibrium. Furthermore, the thermodynamic analysis indicated that the adsorption process was characterised by exothermicity. The efficiency of the adsorbent in removing Cr (VI) from the real electroplating wastewater was obtained about 80%. However, the required adsorbent dose was 1.5 g/L. The fruit of the catalpa tree represents a cost-effective material for producing activated carbon, with a high capacity for adsorbing Cr (VI) from aqueous solution and wastewater.