Comparative application of an irradiated and non-irradiated calcite-type material to improve the removal of Pb in batch and continuous processes

Abstract

The study compared the lead adsorption capacity of an irradiated and non-irradiated calcite-type material carried out in simulated wastewater. The adsorption capacity in the batch process was evaluated at different temperatures and initial concentrations. The equilibrium adsorption was fitted with the Langmuir and Dubinin – Radushkevich models. Kinetic results were described by the pseudo-second order and intraparticle-diffusion models. The thermodynamic parameters were evaluated as well. The highest adsorption capacity in the batch process (4.808 mg/g) was found at 40 °C, with 100 mg/L as initial concentration. The study was also conducted in a continuous mode using only the irradiated material, owing to its high adsorption capacity compared with the non-irradiated one. The effects of flow rate (5, 7.5 and 10 mL/min), initial concentration (60, 80 and 100 mg/L) and bed height (5, 7.5 and 10 cm) were evaluated. The highest adsorption capacity in the continuous process (4.602 mg/g) was achieved at 40 °C, with a 100 mg/L lead initial concentration solution, within a flow rate of 5 mL/min and a bed depth of 10 cm. The breakthrough time for a lead concentration at the exit of the column equal to 1 mg/L was 232.65 min. In this case, the effective mass transfer zone (MTZ) in the packed bed was 5.7 cm for a treated volume of 1163.25 mL and a lead removal of 86.98%. The column experimental results, in terms of the breakthrough curve, were better fitted with the Thomas and Yoon - Nelson models than with Dose – Reponse model.