Mechanism and kinetics of efficient removal of as from a high arsenic-bearing ZnSO4 solution using ultrasound enhanced oxygen

Abstract

The traditional lime method for arsenic (As) removal from high arsenic-bearing ZnSO4 solution has disadvantages such as high cost, large amount of wet residue, significant secondary hazards, and long process flow. This study developed a new technology for efficient As removal using ultrasound enhanced oxygen. The effects of zinc roasting dust (ZRD) addition, reaction temperature, oxygen flow rate, and ultrasound power on As removal efficiency were investigated. Under the optimal conditions, the removal rate of As reached 97.90 %. The1O2, O2∙- and •OH radicals generated during the ultrasound-enhanced oxygen process significantly enhance the oxidation efficiency of As(III) and Fe2+. Ultrasound can also refine particle size and improve the removal efficiency of As. Compared with traditional lime method, the reaction time and wet residue amount have been reduced by 40 % and 70.37 %, respectively. Field emission scanning electron microscopy (FE-SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses indicate that As in ZnSO4 solution was primarily removed through by Fe(OH)3 colloidal adsorption and amorphous FeAsO4. Kinetic analysis revealed that the neutralization and As removal process using ZRD under ultrasound and oxygen action conforms to the internal diffusion control model. Ultrasound-enhanced oxygen As removal can reduce the reaction activation energy from 26.94 to 21.02 kJ/mol, effectively lowering the reaction barrier for As removal and demonstrating faster reaction rates under ultrasound conditions. Ultrasound-enhanced oxygen removal of As from high arsenic-bearing ZnSO4 solution provides an efficient and low-cost potential solution for enterprises.