Keywords: 
• arsenite /
• metallurgical wastewater /
• granular TiO2 column /
• adsorbent regeneration

Abstract: Remediation of metallurgical industry wastewater has presented a great environmental challenge for decades. In this study,a remediation technique for As(Ⅲ) adsorptive removal,adsorbent regeneration,and As(Ⅲ) recovery was proposed. Using three granular TiO2 columns in series, As(III) with initial concentration of 2.5 g·L-1 could be reduced to below the wastewater discharge limit of 0.5 mg·L-1. Optimization of the empty bed contact time (EBCT) suggested that a 20 min EBCT was sufficient for As(Ⅲ)removal. The spent TiO2 could be regenerated using H2SO4 and NaOH. The X-ray diffraction patterns of pristine and spent TiO2 reveal no change in the crystalline structure,which ensures its high effectiveness after regeneration and enables its reuse. Synchrotron-radiation-based micro-beam X-ray fluorescence (μ-XRF) was used to analyze the in situ elemental composition of the solid residue after regeneration,revealing the coexistence of many heavy metals. Arsenic K-edge micro-focus X-ray absorption near-edge structure (μ-XANES) analysis suggested the existence of As(Ⅴ) in the solid residue,indicating that strong alkali conditions during the regeneration process may facilitate the oxidation of As(Ⅲ). The small amounts of solid residue produced during the adsorbent regeneration process may be used as a raw material for the production of arsenic compounds. The waste solution can be further treated after mixing with raw water to adjust the pH to neutral. This adsorption,regeneration,and reuse process provides an innovative technique for metallurgical industry wastewater remediation that is promising for practical applications.