Synthesis of sucrose-derived porous carbon-doped Zr_xLa_1-xOOH materials and their superior performance for the simultaneous immobilization of arsenite and fluoride from binary systems

Amorphous forms of mixed lanthanum-zirconium oxyhydroxide (Zr_xLa_1-xOOH) composite materials, containing porous sucrose carbon as a dopant (PSC-Zr_xLa_1-xOOH), were successfully prepared via co-precipitation and characterized by BET surface area analysis, Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) Energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA). These synthesized materials were utilized for the simultaneous adsorption of AsO₃ ³⁻ and F⁻ from a binary mixture solution in batch tests. The Zr_xLa_1-xOOH and PSC-Zr_xLa_1-xOOH composite materials showed both fast adsorption rates and high adsorption capacities towards AsO₃ ³⁻ and F⁻ in aqueous solution. Most attractively, Zr_xLa_1-xOOH and PSC-Zr_xLa_1-xOOH showed better F⁻ adsorption capacity when the pH was lower than 7, better AsO₃ ³⁻ removal when the pH was higher than 9 and were superior to previously reported metallic oxide-based sorbents. The mechanism can be interpreted based on the HSAB principle, where the bimetallic oxyhydroxides become “soft acids”, while La³⁺ and Zr⁴⁺ are categorized as “hard acids”. Moreover, the PSC-Zr_xLa_1-xOOH adsorbent demonstrated high selectivity for AsO₃ ³⁻ in the co-existence of other ions in a triple component system. The fast adsorption kinetics and high capacity make the designed PSC-Zr_xLa_1-xOOH adsorbent a promising advanced material for the removal of AsO₃ ³⁻ and F⁻ from water in practical applications.