Equilibrium and Kinetic Modelling of Aqueous Cadmium Ion and Activated Carbon Adsorption System

Despite their extensive and decade-long application in wastewater treatment, activated carbon remains one of the most viable adsorbents, with substantive practical application, due to their high pollutant binding capacity. In this study, commercially available activated charcoal was applied in the uptake of aqueous cadmium [Cd(II)] ion. The effect of some process variables on the Cd (II) uptake was investigated via batch mode. Furthermore, the adsorbents' surface charge (pH(PZC)), surface morphology (using SEM) and available surface functional groups (using FTIR) were explained. The pH dependence of the present adsorption system was revealed, while the optimum pH was recorded at pH 5.0. Similarly, the Cd (II) uptake (mg/g) decreased with increasing adsorbent dosage due to possible active sites clogging, overcrowding and interference. Furthermore, the isothermal and kinetics analyses of the experimental data, which were aptly validated using the hybrid error model, respectively depicted the Langmuir isotherm and pseudo-second-order kinetic model as the best fit. A Langmuir adsorption capacity of 682.5 mg g(-1) was also recorded in the study. Consequently, the present adsorption system was characterized by an equilibrium timeframe of industrial practicability; hence, the adsorbent was successfully applied for the aqueous Cd (II) uptake.

Automated summary

Activated carbon, with its high pollutant binding capacity, remains one of the most viable adsorbents for wastewater treatment, as demonstrated in the study which focused on the uptake of aqueous cadmium [Cd(II)] ions. The research revealed the pH dependence of the adsorption system, with pH 5.0 identified as the optimum condition, and a decrease in Cd (II) uptake with increasing adsorbent dosage due to potential active sites clogging. The study also validated the Langmuir isotherm and pseudo-second-order kinetic model as the best fit for the experimental data, highlighting the industrial practicality of the adsorption system.