| Popis: |
Combination with apatite and phosphate solubilizing microbes is a new technique for lead remediation in soil. However, it is difficult to elucidate the detailed reaction processes and the mechanisms via only experiments, especially in explaining why the fluoropyromorphite is not the major product. In this study, GWB software was applied to stimulate the reaction progress in Pb remediation via the application of fungus Aspergillus niger and geological fluorapatite based on our previous experimental data. The oxalic acid was gradually added to the system(100 steps) to simulate oxalic acid secretion by Aspergillus niger in Titration of React module. The initial concentration of Pb2+ was 8.4 mmol·L-1, with the total addition of oxalic acid and fluorapatite of 2.0 g·L-1 and 8.3 g respectively. In React module, the pH value of the system, concentrations of ions(Pb2+、Ca2+、H2PO4-、F- and C2O42-), and formation of products during the addition of oxalic acid and fluorapatite can be tracked. Then, Act2 module was used to simulate the effects of oxalic acid and F- on Pb mineralization, i.e., during adding Pb cations to the filtered solution incubated with Aspergillus niger and fluorapatite. The results showed that the change of pH caused by oxalic acid was the most significant parameter influencing Pb mineralization. The Pb2+ was precipitated mainly as lead oxalate in the system, which was consistent with the previous experimental results. The stable fluoropyromorphite is only formed when the concentration of F- is higher than 27 mmol·L-1 under weak acid or alkaline environments. This study sheds bright light on the theoretical guidance for Pb remediation in soil via phosphate materials. |
