Effective removal of As from a high arsenic-bearing ZnSO4 solution by ultrasonic enhanced ozonation in a one-pot method

Abstract

Currently, removing arsenic (As) from ZnSO4 solution using lime presents several drawbacks, including high wet precipitate content, long reaction time, and the introduction of new impurities. In this study, we propose a novel ultrasonic (US) ozone one-pot method for effectively removing As from a high-arsenic ZnSO4 solution. In this method, as in ZnSO4 solution was removed by ultrasound enhanced ozone oxidation combined with zinc roasting dust (ZRD). No secondary pollution will occur with the addition of ZRD and ozone, as neither introduces new impurities. The experimental results show that under the conditions of initial As and Fe concentrations of 1640 mg/L and 2963 mg/L, US power of 480 W, frequency of 20 kHz, reaction temperature of 60 °C, reaction time of 1 h, ZRD dose of 12 g/L and gas flow rate of 900 mL/min, the removal rate of As can reach 99.4%. The introduction of US can further enhance the oxidation effect of ozone on As(III) and Fe2+ by increasing the solubility of ozone and promoting the production of OH radicals. Additionally, US cavitation and mechanical action increase the probability of contact between various reactants in the solution, facilitating the occurrence of reactions. US also reduces the aggregation of arsenic-containing precipitates and the encapsulation of ZRD by arsenic containing precipitates, thereby decreasing the amount of arsenic-containing precipitates. In comparison to the traditional lime method, this approach results in a significant reduction in the amount of arsenic-containing precipitate by 54.5% and a 60% decrease in the total reaction time. The As removal mechanism of our method encompasses ZRD neutralization, US-enhanced ozone mass transfer and decomposition, oxidation of As(III) and Fe2+, and adsorption and coprecipitation. Consequently, the proposed method provides a cost-effective, fast, safe and environmentally friendly alternative for treating arsenic-contaminated ZnSO4 solutions.