Nanoconfined hydrous titanium oxides with excellent acid stability for selective and efficient removal of As(V) from acidic wastewater

Abstract

Efficient removal of arsenic from acidic industrial effluents is still a challenge because of the high arsenic concentrations and low pH. Herein, a millimeter-sized nanocomposite Ti-201, with excellent acid resistance in acidic arsenic-contaminated water, was synthesized by dispersing the nanosized titanium oxides inside the networking pores of a commercial anion exchanger (D201). Negligible titanium dissolution was observed from Ti-201 in the solution of acidic pHs (above 2). The resulting nanocomposite exhibited superior adsorption capacity and selectivity for As(V) removal from acidic solution, even in the presence of coexisting Cl−/NO3−/SO42− ions at higher concentrations. The adsorption kinetics and thermodynamics of the nanocomposite were also well investigated to elucidate the adsorption behavior. FTIR and XPS study suggested the impregnated titanium oxide nanoparticles played a dominant role during the adsorption process, and As(V) was mainly removed via ligand exchange reactions between arsenic species and hydroxyl groups on the nanoparticles. Besides, fixed-bed column experiments further proved its applicability for As(V) removal in synthetic acid effluents with a working capacity of 1800 BV. The exhausted adsorbent was also amenable to be regenerated by NaOH-NaCl solution for repeated use without any significant capacity loss. All the results demonstrated that the prepared Ti-201 nanocomposite was a promising alternative adsorbent for efficient As(V) removal from acidic contaminated water.