Experimental Research On Inhibiting Oxidation And Acid Formation Of Pyrite By Microorganism

With characteristics of low pH, high volume, long duration, various and high concentration of heavy metals, acid mine drainage (AMD) has caused critical environmental problem both in mines and the ecological environment, and threatened human survival seriously. AMD has attracted wide attention. At present, the treatment of AMD mainly depends on the end of pipe control, which is not a permanent solution. While, based on inhibiting the oxidation of pyrite, source control of AMD has revealed considerable prospect and received more attention in recent years. In this paper, a situ system of mine remediation was investigated in order to inhibit the oxidation of pyrite. The situ remediation system was a system of inhibiting pyrite oxidation, and composed of remediate bacteria (mainly were sulfate reducing bacteria, SRB and iron reducing bacteria, IRB) and medium including sodium lactate and yeast extraction as organic carbon source. Using the system simulated the inhibition of AMD formation, and achieved considerable effect.Research on tryptone, yeast extract and sodium lactate served as organic carbon source in the inhibiting system indicated that, sodium lactate showed better ability of maintaining the growth of the SRB than tryptone and yeast extract. The medium of inhibiting system was established with sodium lactate and the OK salt.Research on the effect of carbon source to iron oxidizing bacteria indicated that, high concentration (>1.0 g/L) of sodium lactate could inhibit the growth of iron oxidizing bacteria and its ability of oxidizing ferrous ion effectively, while yeast extract showed little effect. Therefore, the concentration of sodium lactate in inhibiting system could be optimized from 6.0 g/L to 1.0 g/L, and 0.1 g/L yeast extract was used to maintain the growth of iron reducing bacteria.Research on optimized inhibiting system affectted inhibiting the pyrite oxidation was also conducted. The results showed that, the oxidation of pyrite in the inhibiting system was prevented, and the pH maintained neutral (6.62), and the ORP was under the critical potential level of pyrite oxidation (600 mV vs. SHE). Meanwhile, the concentration of total soluble Fe and sulfate decreased sharply and the inhibiting effect was significant. The remediate bacteria showed decisive function in preventing the pyrite oxidation. Sodium lactate slowed down the process of pyrite oxidation and acid formation, and maintained the growth of SRB. The remediate bacteria also adsorbed on the surface of pyrite and formatted attachment which was mainly complex of iron and organic, including vivianite and pyrrhotite. The inhibiting system could solidify the soluble Fe, which was helpful to the remediation of AMD.The microorganism community structure and dynamic development showed that, SRB were suitable for their growth and the associated bacteria could consume oxygen and build anaerobic environment, which was beneficial to the growth of SRB; meanwhile, iron oxidizing bacteria were inhibited. Real time PCR analysis of SRB and iron oxidizing bacteria indicated that SRB could grow steadily and the concentration of iron oxidizing bacteria was decreased sharply in the inhibiting system. The results above revealed the inhibiting system showed outstanding stability and sustainability, and the system showed considerable propest on the source control of AMD and mine situ-remediation.