Comparison of the removal and adsorption mechanisms of cadmium and lead from aqueous solution by activated carbons prepared from Typha angustifolia and Salix matsudana

Abstract

Activated carbon adsorption is a promising technique for treatment of low-concentration heavy metal pollutants with high efficiency, simple operation, and flexibility; however, the cost of commercial activated carbon is too high. Therefore, much attention has been paid to activated carbon derived from low-cost agricultural and forest wastes. In this work, adsorption of Cd and Pb in aqueous solutions were conducted through batch experiments using Typha angustifolia carbon (TC) and Salix matsudana carbon (SC) prepared by phosphoric acid activation, and the adsorbents were characterized using SEM, FTIR, XPS, elemental analyzer, BET surface area, and zeta potential measurements. Both TC and SC mainly encompassed mesopores and bonds of O–H, C–O, CO, and PO/P–O–C. The BET surface area and isoelectric point (pH_IEP) of TC and SC was 130.42 and 234.42 m² g⁻¹ and 3.45 and 4.38, respectively. The adsorption capacity of Cd and Pb for TC and SC both relied positively on the pH and humic acid but negatively on NaCl in the media. The adsorption process was spontaneous and endothermic, involved physicochemical reactions, and fitted well with the pseudo second-order and Langmuir models. Both the intraparticle diffusion and the chemical reaction were the rate limiting steps during adsorption. The maximum sorption capacity of Cd and Pb was 48.08 and 61.73 mg g⁻¹ (TC) and 40.98 and 58.82 mg g⁻¹ (SC), respectively, at pH 5 and 25 °C. The adsorption–desorption results showed that both activated carbons had good regeneration and reusability properties. The results suggested that both TC and SC had potential applications in the removal of Cd and Pb from aqueous solutions.