Enhanced removal of toxic Cr(vi) and Pb(ii) from water using carboxylic terminated Ti3C2Tx nanosheets

Abstract

The discharge of Cr(VI)and Pb(II) contaminants into water resources through industrial waste induces a considerable risk to human and marine life, which demands an effective removal of these toxic metal ions (MI) from the aquatic environment. This study presents a remarkable adsorption performance of the carboxylic terminated Ti₃C₂T_x nanosheets synthesized using ammonium bifluoride and citric acid and applied as adsorbents for the removal of Cr(VI)and Pb(II) from water. Adsorption efficiency was evaluated under sonication, MI concentration, and solution temperature at pH 5.5. Maximum adsorption capacities of 1090 mg g⁻¹ and 1135 mg g⁻¹ for Cr(VI) and Pb(II) were attained within 7 and 4 minutes, respectively. Moreover, adsorption kinetic and isotherm studies were conducted, and the experimental data was found to fit well with pseudo-second-order reaction and Freundlich models. It was also established that the main interactions to drive the adsorption reactions were the electrostatic forces between the adsorbates and Ti₃C₂T_x adsorbent. Furthermore, (–COOH) and (–OH) terminal groups were the main contributors to the adsorption of Cr(VI) and Pb(II) pollutants through an ion exchange mechanism. Besides the ion exchange mechanism, chemical coordination, entrapment of the adsorbates, and van der Waals forces lead to a physiochemical interaction between the MI and Ti₃C₂T_x nanosheets. In addition, Ti₃C₂T_x nanosheets showed better selectivity towards Pb(II) removal than Cr(VI) in an aqueous solution. The nanosheets also exhibited more than 80% removal efficiency even after six cycles of regeneration and reusability. Additionally, Ti₃C₂T_x nanosheets offered superior adsorption performance for Cr(VI) and Pb(II) compared to previously reported titanium carbide MXenes and activated carbon-based adsorbents. Hence, these high-quality and efficient Ti₃C₂T_x nanosheets can potentially eradicate other hazardous MI contaminants from wastewater.