Effective removal of Pb(ii) from synthetic wastewater using Ti3C2Tx MXene†
MXene (Ti3C2Tx) was used to remove heavy metals from aqueous solutions; we focused principally on Pb(II) adsorption by MXene using several performance tests and various forms of characterization. Powder activated carbon (PAC) served as the control material of MXene. We used scanning electron microscopy, porosimetry, and a zeta potential analyzer to evaluate the intrinsic properties of MXene and PAC. Although the surface area of MXene was ∼50-fold less than that of PAC, MXene exhibited better adsorption because of its higher negative surface charge. We systematically evaluated MXene-mediated Pb(II) adsorption both kinetically and isothermally, and found that adsorption was well-explained by a pseudo-second-order kinetic and the Freundlich isotherm models, respectively. Notably, attainment of equilibrium within 30 min is valuable when MXene serves as an adsorbent. The principal Pb(II) adsorption mechanism in play was electrostatic attraction, as revealed by experimental results using solutions of different pH levels, ionic strengths, and humic acid concentrations. MXene exhibited good adsorption of four different heavy metals [Pb(II), Cu(II), Zn(II), and Cd(II)] from single-electrolyte solutions. The Pb(II) adsorption mechanisms in play were ion exchange and inner-sphere complex formation, as revealed by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Additionally, MXene exhibited good re-usability over four cycles of adsorption/desorption. Therefore, MXene may be very valuable when heavy metals must be removed from wastewater, judging from good adsorption properties and re-usability.