Enzymatic hydrolysis lignin functionalized Ti₃C₂T_x nanosheets for effective removal of MB and Cu²⁺ ions

Functionalized two-dimensional Ti₃C₂T_x (TN-EHL) was prepared as an effective adsorbent for removal of methylene blue dye (MB) and copper ions (Cu²⁺). Enzymatic hydrolysis lignin (EHL), a reproducible natural resource, was used to functionalize the Ti₃C₂T_x nanosheets. EHL can not only introduce active functional groups into TN-EHL but also prevent the oxidation of Ti₃C₂T_x, thus promoting the adsorption performance of TN-EHL. The maximum adsorption capacities of TN-EHL50 (in which the EHL content is 50 wt%) for MB and Cu²⁺ were 293.7 mg g^-1 and 49.96 mg g^-1, respectively. The higher correlation coefficients (R²) of MB (0.9996) and Cu²⁺ (0.9995) indicating that their adsorption processes can be described by the pseudo-second-order kinetic model. The MB adsorption data fit the Freundlich isotherm with R² of 0.9953, whereas the Cu²⁺ ions adsorption data fit the Langmuir isotherm with R² of 0.9998. The thermodynamic analysis indicates that the adsorption process of MB and Cu²⁺ on TN-EHL50 is spontaneous and endothermic. Significantly, the Cu²⁺ ions were reduced to Cu₂O and CuO particles during the adsorption process. Therefore, TN-EHL has a great potential as an environmentally friendly adsorbent for MB removal and recovery of Cu²⁺ ions from wastewater.