Effective Adsorption of Chlorinated Polyfluoroalkyl Ether Sulfonates from Wastewater by Nano-Activated Carbon: Performance and Mechanisms

Chlorinated polyfluoroalkyl ether sulfonates (F-53B) were often used as mist suppressants in the chrome plating industry, resulting in the large discharge of F-53B-containing electroplating wastewater into the aquatic environment. Due to the high toxicity of F-53B, increasing attention has been paid to its efficient removal from wastewater. In this study, three nano-activated carbons were successfully prepared from coconut shell carbons by a simple one-step KOH activation method. The nitrogen adsorption/desorption experiments showed that the synthesized coconut shell activated carbons possessed a well-developed nano-pore structure, which was favorable for the adsorption of F-53B. The results suggested that the adsorption of F-53B on the coconut shell activated carbons followed pseudo-second-order kinetics and was better fitted in the Langmuir isotherm, indicating that the adsorption of F-53B was mainly controlled by chemical adsorption and was mainly monolayer adsorption. Theoretical calculation results revealed that the faster adsorption rate of F-53B on CSAC_800 than on CSAC_600 and CSAC_700 could be contributed to the lower adsorption energy of F-53B on CSAC_800 and the higher self-diffusion coefficients of F-53B in CSAC_800. The higher adsorption capacity of CSAC_800 (qm = 537.6 mg·g−1) for F-53B than that of CSAC_600 (qm = 396.83 mg·g−1) and CSAC_700 (qm = 476.19 mg·g−1) could be attributed to the higher specific surface area and larger number of adsorption sites of CSAC_800. The results of this study demonstrate that coconut shell activated carbons with a well-developed nano-pore structure are an effective adsorbent for F-53B removal and have a good application prospect.