Proton Self-Enhanced Hydroxyl-Enriched Cerium Oxide for Effective Arsenic Extraction from Strongly Acidic Wastewater

Acid recycling and arsenic recovery from strongly acidic wastewater are goals of the metallurgical industry to reduce carbon emissions. In this study, arsenic was recovered using a hydroxyl-enriched CeO₂ adsorbent, and the adsorption mechanism in a strongly acidic solution was investigated. The adsorption capacities of 88.59 mg/g for As(III) and 126.211 mg/g for As(V) at pH 1.0 are the highest reported values to date. It is revealed that the hydroxyl groups on the CeO₂ surface can buffer hydrogen ions, and the isoelectric point of the material can be reduced to pH 1.52. The binding energy of arsenic is -1.25 eV for the hydroxyl-enriched CeO₂ and -2.24 eV for CeO₂ without hydroxyl groups. Additionally, the protonated hydroxyl groups reduce the oxidation energy of As(III) and promote the adsorption of arsenic by forming new active sites in the strongly acidic solution. Nearly 98.11% of arsenic (initial concentration is 886.8 mg/L) is removed within 24 h without pH adjustment, indicating the feasibility of hydroxyl-enriched CeO₂ for recovering arsenic and acid. This work investigated the adsorption and proton-enhanced oxidation mechanism of arsenic by hydroxyl-enriched CeO₂ in strongly acidic wastewater.