Removal of nickel ions from industrial wastewater using tms-EDTA-functionalized Ti₃C₂T_x: Experimental and statistical physics modeling

This study investigates the surface modification of Ti₃C₂T_x MXene using tms-EDTA (EDTA@MXene) to develop an efficient adsorbent for divalent heavy metal cations, such as Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, and Zn²⁺, from contaminated water. EDTA@MXene showed significantly enhanced adsorption capacities for these ions compared to pristine MXene. Using nickel ion (Ni²⁺) as a model adsorbate, EDTA@MXene demonstrated remarkable removal efficiency, reaching a maximum adsorption capacity of 249.5 mg/g as compared to the 61.4 mg/g of pristine MXene with fast kinetics and attaining equilibrium within 30 min. The results indicated that Ni²⁺ adsorption followed a pseudo-second-order kinetic model, with equilibrium data fitting both Langmuir and Freundlich isotherm models. As the classical adsorption models remained inconclusive on the underlying adsorption mechanisms, advanced statistical physics models were subsequently applied for deeper investigation. The findings revealed that Ni²⁺ ions adsorbed onto the surface in a non-parallel orientation. The adsorption process was reversible, endothermic, and driven mainly by physical interactions, with higher temperatures favoring greater adsorption capacity. EDTA@MXene demonstrated excellent reusability, maintaining high (>80 %) regeneration efficiency after five regeneration cycles. It also exhibited a high adsorption capacity for Ni²⁺ ions from nickel electroplating wastewater, highlighting its potential for real application in the treatment of metal-contaminated industrial wastewater.