The performances and mechanisms for Cr(VI) and Cr(III) removal using TMAOH delaminated Ti3C2Tx suspension

Ultra-thin MXene nanosheets (Nss) were facilely prepared via delaminating and intercalating the multi-layered MXene using tetramethylammonium hydroxide (TMAOH). Electron-rich characteristics, abundant surface active sites and the negative charges made MXene Nss having both good reduction ability and adsorption capacities, which would effectively remove anion Cr(VI) via reduction and remove cation Cr(III) via adsorption. Batch adsorption tests were carried out to study the pH impact, adsorption kinetics and isotherms. Upon adsorption, the well dispersed MXene Nss suspension was aggregated to form flocs and sediment at the bottom. The maximum Cr(VI) and Cr(III) removing capacities are calculated to be 554.9 mg/g at 318 K and 283 mg/g at 298 K, respectively. The mechanisms on Cr(VI)/Cr(III) adsorption were well studied employing SEM, TEM, XPS and FT-IR. In addition, the MXene Nss also showed good adsorption capacity towards other metal cations (such as Cu2+, Cd2+, and Pb2+), manifesting that the current MXene Nss has the potential to be used as a general-purpose adsorbent.