粤北大宝山多金属矿酸性矿山废水中氧化亚铁硫杆菌对黄铁矿的生物氧化作用研究

A study of the bio-oxidation of pyrite by Acidithiobacillus ferrooxidans from the acid mine drainage in the Dabaoshan polymetallic ore deposit,northern Guangdong

利用从大宝山尾矿库酸性矿山废水培养得到的氧化亚铁硫杆菌(A.f.菌)和废矿石中的黄铁矿进行不同pH值条件下加菌和不加菌氧化实验。通过测定实验过程溶液的阳离子、硫酸根离子含量和pH值,并通过实验固体产物的XRD分析和反应前后黄铁矿表面的扫描电镜(SEM)对比分析,探讨了大宝山酸性矿山废水中的A.f.菌在不同pH值条件下对黄铁矿的氧化作用。认为:大宝山黄铁矿氧化过程中除了产生Fe离子之外,还产生了Cd、As等毒性离子,黄铁矿在pH值为2.00的环境下比pH值为3.00的环境下更容易被氧化;A.f.菌对黄铁矿的氧化有明显的促进作用,在实验条件的30d内使黄铁矿的表观氧化速率提高2～3倍;黄铁矿的生物氧化作用应该包括非接触的间接氧化作用和接触氧化作用。

The microbial oxidation of sulfide minerals in wet metallurgy has been widely studied.In recent years,the reaction between the bacterium Acidithiobacillus ferrooxidans （A.f.） and pyrite in mining environments has also aroused attention and become a focus in the study of reactions between microorganisms and minerals.In this paper,a strain of A.f.isolated from the acid mine drainage （AMD） and the mineral pyrite from the tailings of the Dabaoshan Mine were used to probe into the bio-oxidation of pyrite.Experiments were designed to compare the differences between abiotic oxidation and bio-oxidation of pyrite under different pH conditions and to investigate the effects of A.f.and pH conditions on the oxidation of pyrite.Before the experiment,the pyrite was crushed to less than 0.18 mm in size,immersed in an absolute ethyl alcohol for 30 minutes,and then washed with deionized water 3 times and put in a 50℃ vacuum drying oven for 2 hours for experimental uses.A small amount of the prepared pyrite powder was used to observe its surface morphology under a cold field emission scanning electron microscope.All the immersing experiments were then carried out in 250 mL conical flasks at a cleaning work station.A density of 3% of pulp （3 g of pyrite powder in a 100 mL solution） was added to each flask.The pyrite powder was added to a 9 K culture medium without Fe2＋,inoculated with 10% （the ratio between the volume of bacterial suspension added in and that of the total solution） of A.f.suspension,and adjusted to pH 2.00 and 3.00 respectively by using 1：1 H2SO4.The experimental flasks were put in an oscillator for shaking cultures at a constant temperature of 30℃ and a rotating speed of 150 r/min,oscillating 20 hours a day.Experiments without adding A.f.suspension were also conducted at the same time for comparison.The concentrations of cations such as Fe2＋,As5＋ and Cd2＋,anion SO2-4 and pH values during the experiments were measured regularly.Some of the solid experimental results were collected and dried in a 50℃ vacuum drying oven and then analyzed with XRD.A small quantity of the collected solid result was washed with deionized water 3 times,dried in a 50℃ vacuum drying oven and then investigated under a cold field emission scanning electron microscope.The experimental results showed that Fe2＋,Cd2＋,As5＋ ions were produced by the oxidation of pyrite and that the pyrite is easier to be oxidized at pH 2 than at pH 3.The bacterium A.f.promoted the oxidation of pyrite by raising the apparent oxidation rate by 2～3 times in 30 days of the experiment.The bio-oxidations of pyrite may include indirect oxidation and contact oxidation.The results will provide valuable reference for source remediation of the AMD pollution in the Dabaoshan Mine.