Test And Mechanism Of Microbial Induced Solidification And Remediation Of Lead-zinc Tailings Containing Sulfur

The structure of lead-zinc tailings containing sulfur was loose,and it was easy to release a large number of heavy metal ions and SO₄^2-.Based on the microbial induced calcium carbonate deposition technology with environmental friendliness,strong adhesion,low energy consumption and low carbon emission,the effects of two typical mineralized microorganisms,sulfate-reducing bacteria(SRB)and Bacillus pasteurii,on the solidification of tailings particles were compared.Meanwhile,the remediation laws of SO₄^2-and heavy metals in sulfur-bearing lead-zinc tailings induced by microorganisms were analyzed.On the other hand,the feasibility of using microbial induction to solidify and repair sulfur-bearing lead-zinc tailings was explored.In the End,the regulation method based on SRB/Bacillus pasteurii was proposed.The main research results are as follows:(1)The optimal growth conditions of SRB and Bacillus pasteurii were 34.74°C,p H=8.00,COD/SO₄^2-=1.98 and 31.01°C,p H=9.07,urea concentration 0.50 mol/L,respectively.SRB and Bacillus pasteurii remained active under metal ion stress and induced mineralization to fix metal ions,which were used to repair metal pollutants released from sulfur-bearing lead tailings.Among them,the immobilization capacity of metal ions by SRB and Bacillus pasteurii were Cr>Fe²⁺>Pb²⁺>Mn²⁺>Zn²⁺>Cu²⁺and Fe²⁺>Cr³⁺>Zn²⁺>Mn²⁺>Cu²⁺>Pb²⁺,respectively.The SRB cultured for 14?86 h and Bacillus pasteurii cultured for 22?26 h were in the logarithmic growth phase,which were more suitable for microbial induced solidification and repair of sulfur-containing lead-zinc tailings.(2)The effect of sulfur-containing lead-zinc tailings induced by SRB and Bacillus pasteurii was compared by layered solidification method.The effects of sulfur-containing lead-zinc tailings addition amount,bacteria injection amount,bacteria injection time and tailings particle size on microbial induced solidification and repair of sulfur-containing lead-zinc tailings were investigated.The regulation method based on SRB/Bacillus pasteurii was proposed.The results illustrated that when adding 1 cm tailings in each layer,injecting 250 m L SRB,injecting SRB for14 d,and tailings particle size was more than 100 mesh,the effect of SRB induced repair of sulfur-containing lead-zinc tailings was the best.Besides,the fixation rates of SO₄^2-,Fe³⁺,Mn²⁺,Pb²⁺,Zn²⁺,Cu²⁺and total chromium in the leaching solution after repair were 95.44%,100%,87.09%,100%,95.54%,86.23%and 93.34%,respectively.When 2 cm tailings were added to each layer,100 m L bacterial solution/cementing solution was injected,cementing and curing for 10 d,and the particle size of tailings was more than 100 mesh,the effect of Bacillus pasteurii induction curing and remediation of sulfur-containing lead-zinc tailings was the best.The compressive strength was stable at 1 MPa after curing.In addition,the fixation rates of Fe³⁺,Zn²⁺,Pb²⁺,Cu²⁺and Cd²⁺in the leaching solution were 100%after remediation.Among them,the fixation rates of Mn²⁺and total Cr were 97.85%and 94.45%,respectively.(3)On account of single factor and response surface experiments,the key characteristic parameters of microbe-induced curing and remediation of sulfur-containing lead-zinc tailings were optimized.Among them,the key characteristic parameters of SRB induced solidification and repair of sulfur-containing lead-zinc tailings were as follows:the solid-liquid ratio of tailings to SRB was 33 g:300 m L,curing with bacteria for 12 d.At this time,the fixation rates of SO₄^2-,Fe³⁺,Mn²⁺,Zn²⁺,Pb²⁺,Cu²⁺,Cd²⁺and total Cr in sulfur-containing lead-zinc tailings were 99.98%,100%,92.89%,99.58%,100%,98.54%,100%and 100%,respectively.The key characteristic parameters of Bacillus pasteurii induced solidification and repair technology of sulfur-containing lead-zinc tailings were as follows:the solid-liquid ratio of tailings to bacterial solution(cementation solution)was 57.09 g:100 m L,and the bacterial curing was 10.23 d.At this time,the fixation rates of Fe³⁺,Mn²⁺,Zn²⁺,Pb²⁺,Cu²⁺,Cd²⁺and total Cr in sulfur-containing lead-zinc tailings were 100%,98.96%,100%,100%,100%and 94.79%,respectively.Furthermore,the compressive strength of the reinforced specimen was 1.27 MPa,which was far higher than the strength requirement of the backfill paste.(4)The ability of resistance to freeze-thaw cycle and acid corrosion of sulfate-containing lead-zinc tailings induced by SRB is higher than that of Bacillus pasteurii.At 125°C,vaterite in the tailings sample solidified by Bacillus pasteurii was transformed into aragonite and calcite,and the compressive strength of the sample was increased from 1.27 MPa to 1.53 MPa.(5)SEM,EDS,XPS,XRD,XRF,FTIR and IIIumina Miseq sequencing results indicated that the main mechanism of sulfur-containing lead-zinc tailings remediation induced by SRB was that Desulfovibrio?idahonensis and Desulfotomaculum?sp.in enriched SRB could metabolize SO₄^2-to induce the formation of metal sulfide crystals.The main mechanism of solidification of lead-zinc tailings containing sulfur attracted by Bacillus pasteurii was that Bacillus pasteurii catalyzes urea hydrolysis to produce CO₃^2-.After that Ca CO₃ crystals were formed by CO₃^2-and Ca²⁺with cell membrane,EPS and other nucleation sites which improved the compressive strength of tailings.There are 104 figures,23 tables and 214 references in this paper.