Exploring chitosan-loaded activated carbon fiber for the enhanced adsorption of Pb(II)-EDTA complex from electroplating wastewater in batch and continuous processes

Abstract

The heavy metal complexes found in electroplating wastewater possess strong stability and present serious risks to human health and water environment quality. Herein, chitosan-loaded activated carbon fiber (CS/ACF) was successfully designed to adsorb Pb(II)-EDTA from electroplating wastewater. Characterization results revealed that CS was successfully loaded onto ACF surface, and plenty of oxygen/nitrogen functional groups appeared on CS/ACF. Adsorption performances of ACF and CS/ACF for Pb(II)-EDTA were compared by batch adsorption experiments. Pb(II)-EDTA adsorption by CS/ACF was minimally influenced by pH0 over a broad range (2.00–12.00), while pH0 had a higher impact on Pb(II)-EDTA adsorption by ACF. Adsorption equilibrium on CS/ACF could be achieved within 30 min with 99.40% of Pb(II)-EDTA (0.1988 mmol∙g−1) removal. By contrast, ACF could only eliminate 52.75% of Pb(II)-EDTA (0.1055 mmol∙g−1). The Freundlich model was appropriate for depicting Pb(II)-EDTA adsorption by ACF, and the Langmuir model exhibited an improved fit for Pb(II)-EDTA adsorption by CS/ACF. Several characterizations were employed to verify that the excellent adsorption performance of CS/ACF for Pb(II)-EDTA was chiefly ascribed to hydrogen bonding, and inner-sphere complexation. Fixed-bed dynamic adsorption of Pb(II)-EDTA on CS/ACF was significantly affected by the bed height, Pb(II)-EDTA influent concentration, and influent flow rate. Thomas and Yoon-Nelson models were more suitable to depict the dynamic adsorption breakthrough curve of Pb(II)-EDTA on CS/ACF. Ten adsorption-desorption cycle experiments indicated that CS/ACF was attractive for excellent reusability, durability, and structural stability. This work suggests beneficial strategies for heavy metal complexes removal from electroplating wastewater and sheds new light for the further practical applications of ACF.