In-situ assembled ZIF-67 on ultrasonically exfoliated MXene sheets as an effective heterostructure for Ni adsorption from water

Nickel (Ni) contamination in wastewater poses a serious environmental challenge due to its toxicity, persistence, and bioaccumulation. In this study, a novel hybrid adsorbent (ZIF@MX-U) was synthesized via in situ growth of ZIF-67 on ultrasonically exfoliated Ti₃C₂Tₓ MXene for efficient Ni removal. Ultrasonic exfoliation suppressed MXene restacking, yielding highly delaminated nanosheets that enabled uniform deposition of ZIF-67 crystals and improved accessibility of active sites. Successful integration of ZIF-67-MX-U was confirmed by XRD, FTIR, SEM, TEM, Raman spectroscopy, and N₂ adsorption–desorption analyses. The hybrid structure exhibited substantially enhanced surface area, porosity, and interlayer spacing compared with pristine MXene. Incorporation of hydrophilic MXene also improved the dispersion and stability of ZIF-67 in aqueous media. Adsorption kinetics followed a pseudo-second-order model, indicating predominant chemisorption of Ni via Co-Nx sites and MXene surface functional groups. Under the optimal pH value of 7 and ambient temperature, the hybrid adsorbent achieved 96.8% Ni removal. Furthermore, a maximum adsorption capacity of 47 mg.g −1 was obtained from the Langmuir isotherm analysis at higher initial Ni 2+ concentrations. Equilibrium data fit the Freundlich isotherm (R 2 > 0.99), suggesting multilayer adsorption on a heterogeneous surface. The adsorbent retained over 90% capacity after four cycles, demonstrating excellent stability and reusability and highlighting its strong potential for Ni removal.