Scalable and sustainable production of Ti3C2Tz MXene and fluorine recovery from wastewater through cryolite precipitation

Abstract

Treatment of HF or HCl/LiF etched Ti₃C₂T_z with 0.05 M NaHCO₃ before water washing reduces the wastewater generated by 75%. When etched with HF, cryolite (Na₃AlF₆) precipitation from spent etching waste effectively removes fluorine from this waste stream, offers insight into the etching chemistry of MAX to MXene, and provides an effective analytical tool for optimization of MXene production. Additionally, washing HF etched multilayered Ti₃C₂T_z with 0.05 M NaHCO₃ allows for the production of delaminated Ti₃C₂T_z colloidal suspensions, which typically requires the use of TBAOH or DMSO for intercalation and subsequent delamination. Ti₃C₂T_z made with HCl/LiF and washed with 0.05 M NaHCO₃ yields a colloidal suspension with a concentration of 18 mg mL⁻¹ and a film conductivity of 1150 S cm⁻¹.