Study On Removal And Its Mechanism Of Heavy Metals By Acidithiobacillus Ferrooxidans In Steel-picking Sulfuric Acid Pickling Waste Liquor

Steel-pickling sulfuric acid waste liquor contains large amounts of acidic substances andmetal ions, in particular, contains lots of Fe2+, its pH is usually about2.0or even lower. It canseriously erode soil and hydraulic structure equipment. The traditional treatment approachwas neutralization,but it wasted much sulfuric acid and produced large amounts of solid wasteas secondary pollution. Steel pickling liquor reclamation is still in the primary stage andmainly through physical, chemical methods, but its recovery rate was low meanwhile theanti-corrosion and operating cost was very high.The biological method with acidophilicbacteria, oxidizing ferrous ions into ferric ion,eliminated the need of neutralizing acidfacilities and expenses. Fe3+produced during oxidation process can be recycled asmetallurgical raw materials and flocculant. It is significant for metallurgy and machinery torealize pollution elimination and energy saving. In this paper, we isolated a acidophilicstrain,then built a continuous flow complete mixed biological reactor.The optimum operatingconditions,the tolerance of the strain and the remove of heavy metals ion were investigated.Atlast, a preliminary inquiry of the removal mechanism were studied.The main conclusionswere as follows:1、An acidophilic strain was isolated from drainage in Shan xi coal mine, after16SrDNA amplification and sequencing analysis, it was identified to be Acidithiobacillusferrooxidans, and the gene accession number was KF378735.2、Built a completely mixed bioreactor. By single factor experiments,the results showedthat the optimum retention time of the reactor was13h.3、The tolerance of heavy metals of the strain were proved to be1600mg/l,900mg/l,500mg/l and600mg/l for Zn2+、Ni2+、Cu2+、Cd2+.its much higher than inpure culture flask shaking experiments tolerance values (Zn2+1000mg/l, Ni2+250mg/l,Cu2+300mg/l, Cd2+200mg/l).4、The removal rate of metal ions of the strain and the changes of ferric ionconcentration in the process were Investigated，and showed the maximum removal rates wereup to100%、95.7%、68.3%、80%for Zn2+(300mg/l)、Ni2+(100mg/l)、Cu2+(100mg/l)、Cd2+(100mg/l).5、Heavy metal removal mechanism of the strain was conducted in a preliminaryinquiry, and results showed that the strain of heavy metal removal mechanism hasco-precipitation, and to different metal ions, the contribution value of co-precipitation wasdifferent, respectively Zn2+94%, Ni2+25%, Cu2+10.7%, Cd2+33.3%.