| Acidithiobacillus ferrooxidans(A.ferrooxidans)and its soluble extracellular polymers(EPS)can promote the formation and transformation of secondary high-iron minerals such as schwertmannite and jarosite in environment.The iron minerals effectively remove heavy metals in polluted water environment and some harmful substances which lead to eutrophication of water bodies by adsorption,coprecipitation,structural elements combination and coordination complexation.In the natural environment,low molecular weight organic acid sodium is widespread,and it can potentially affect the migration of metals in the environment,which has a great influence on the earth’s biological cycle.This article mainly focuses on the effects of low molecular weight organic acid sodium on the formation of iron minerals in arsenic and phosphorus-containing iron bacteria-related solutions.By measuring the ion concentration,the minerals are characterized and analyzed by X-ray diffraction,infrared spectrometer and scanning electron microscope.The main research results are as follows:In the iron bacterial culture system,add low molecular weight organic acid sodium(10～40 mM sodium oxalate,10～40 mM sodium citrate,6～20 mM sodium malate)without additional contaminating ions:the addition of low molecular weight organic acid sodium in a lower concentration has no obvious effect on the ability of bacteria to oxidize Fe2+,which is beneficial to the conversion of schwertmannite to rhomboid jarosite.When the concentration is higher,it produces obvious inhibition,the iron precipitation products are mainly schwertmannite,and the formation of schwertmannite and the transformation of jarosite are inhibited.The addition of sodium malate is more likely to promote the conversion of schwertmannite to jarosite than sodium oxalate and sodium citrate.In the iron bacterial culture or EPS solution system containing suitable low molecular weight organic acid sodium(sodium oxalate SO 10,sodium citrate SC 10 and sodium malate SM10),the iron minerals formed after 7 days are mainly jarosite under the condition of no,one or two pollutants.However,in the iron bacteria culture containing sodium malate SM10 and As/P{1.0(g/L)/0.1(g/L)} coexisting,the conversion of iron phosphate into jarosite in the solution is inhibited.The one pollution containing only P under these two systems has a higher removal rate of P than the coexisting pollution containing As/P.There is no significant difference in the removal of As,which is not conducive to the removal of As.Add low molecular weight organic acid sodium(10～40 mM sodium oxalate,10～40 mM sodium citrate,or 6～20 mM sodium malate)to the iron bacteria culture system coexisting with As/P{1.0(g/L)/0.1(g/L)},the final minerals formed in the system is jarosite or iron phosphate.The addition of sodium citrate can reduce the removal of As,but the addition of sodium oxalate and sodium malate can increase the removal of As.The addition of three low molecular weight organic acid sodium all inhibit the removal of P by iron minerals.Add low molecular weight organic acid sodium(10～40 mM sodium oxalate,10～40 mM sodium citrate,or 6-20 mM sodium malate)to the EPS solution system coexisting with As/P{0.3(g/L)/0.1(g/L)},a small amount of iron minerals finally formed in the reaction solution is precipitated as jarosite.It has little effect on the removal of P.The removal rate of As by sodium oxalate is slightly higher than that of sodium citrate and sodium malate,and its removal rate increases with the increase of sodium oxalate concentration.The above research results provide a theoretical basis for the treatment or removal of one or coexisting pollutants in acid mine wastewater containing low molecular weight sodium organic acid,reveal the passivation and retention mechanism of toxic and harmful elements by iron minerals,which could provide practical significance for biological mineralization to remove pollutants in complex environment. |
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