Ultrasound-Assisted H₃PO₄, KOH, KH₂PO₄ Extracted Soil A Rsenic

Ultrasound is applied to environmental pollution remediation, which attracts a more concern. In this study, heavy metal extraction experiments were conducted by using solutions of KOH, KH2PO4 and H3PO4 as extractants under two different conditions (vibrating and ultrasound-vibrating). In order to research effects of concentrations of extractants, solid-liquid ratio, ultrasonic time, ultrasonic power, and action time on extraction efficiency and select the optimal extract condition, three extraction orthogonal experiments of As from a contaminated soil were conducted with ultrasound-enhanced KOH, KH2PO4 and H3PO4 solutions. And changes in species of As in the soil were analyzed using the sequential extraction procedures before and after extraction. The main results are as follows:(1) With the increase of concentration (0-2.0mol/L), the extraction ratios of As in the soil of three extractants (KOH, KH2PO4 and H3PO4) increased, and removal ratios of soil As were 1.23%-28.81%,1.20%-29.42%, and 1.46%-66.77%, respectively. H3PO4 could extract larger munber of As in soil than KOH and KH2PO4 under the vibrating condition.(2) Changes in species of As in the soil were analyzed using the sequential extraction procedures before and after extraction. Using KOH extraction, the species of As in soil change significantly, compare with the species of As before extraction, Al binding state of As and Fe binding state of As decreased 23.47%-53.19% and 53.12%-74.93%, respectively. And using KH2PO4 extraction, the species of As in soil change significantly, compare with the species of As before extraction, Fe binding state of As and Ca binding state of As decreased 57.32%-96.96%,36.01%-91.66%, respectively. And using H3PO4 extraction, the species of As in soil change significantly, compare with the species of As before extraction, Al binding state of As, Fe binding state of As and Ca binding state of As decreased 18.35%-61.72%, 57.75%-61.72% and 36.01%-91.66%, respectively.(3) Extraction orthogonal experiments of As from a contaminated soil were conducted with ultrasound-enhanced KOH, KH2PO4 and H3PO4 solutions, and theresults indicate that ultrasound enhanced the removal rates of As in soil by extractans. The optimal condition for KOH, KH2PO4 and H3PO4 extracting soil As under ultrasound-enhanced were all A4B2C3D1E4:extractans (KOH, KH2PO4 and H3PO4) concentration of 1.00 mol/L, soil to liquid rate of 1:10, irradiation time of 12 mins, ultrasound power of 2%and extraction 4 times. Under this condition, KOH, KH2PO4 and H3PO4 removal ratios of soil As were 65.25%,61.0%, and 66.03%, respectively.(4) The best removal rate of As in soil was by using ultrasound-enhanced extractants of H3PO4, and maximum removal rate of As in soil was% 66.03%. Under ultrasound-enhanced condition, the species of As in soil change significantly, compare with the species of As before ultrasound-enhanced extraction, the removal rates of Al binding state of As, Fe binding state of As, and Ca binding state of As were 67.25%, 95.01%, and 60.17%, respectively. The H3PO4 concentration and extraction times were the major factors for effect of the removal rates, and their data range value reached 15.52 and 37.86, respectively.