嗜酸性细菌浸出线路板的吸附行为、动力学及机理研究

发布时间：2018-09-09 09:16

【摘要】：电子废弃物特别是废旧线路板中含有丰富的金属资源,具有很大的回收价值。近年来,生物浸出技术引起了广泛关注。目前,废旧线路板中有价金属浸出的研究主要集中在初始Fe2+离子浓度、初始pH值、粉末投加量、接种量等浸出条件。嗜酸性细菌浸出线路板中金属的机理一般借鉴浸矿领域的成果,但是线路板中的有价金属大多为零价,其浸出机理的研究很少,特别是吸附行为、吸附动力学及吸附机理有待深入研究。因此,本研究在验证存在接触浸出机制的基础上,研究了菌体在线路板粉末表面的吸附行为和动力学特性,以脂多糖为代表物质验证了其在吸附过程中的作用及可能的吸附机制。主要结果如下:(1)通过化学浸出、不同初始亚铁浓度、透析袋实验,验证了生物浸出线路板粉末机制并考察了吸附在接触浸出机制中的作用。结果表明,化学浸出组铜的浸出率仅为2.3%,而生物浸出组为83.8%。透析袋阻隔细菌与金属粉末的直接接触导致其铜浸出率仅为47.9%,而未加透析袋组铜的浸出率为81.43%。这表明,生物浸出包含接触浸出和非接触浸出两种机制类型,接触浸出机制在生物浸出过程起着重要作用。其中,吸附是接触浸出发生的第一步,这意味着线路板粉末可能会与细菌存在吸附行为。(2)通过考察接种不同浓度氧化亚铁硫杆菌(A.ferrooxidans)浸出线路板中铜的吸附行为,探索了菌体在线路板粉末表面的吸附过程,分析了其吸附行为的动力学特性。结果显示,A.ferrooxidans在线路板粉末表面存在吸附,且于5 h内达到平衡。随着初始菌浓度的增大,吸附速率和吸附的微生物量也随之增大。当初始菌体浓度为2.4×105、2.4×107和2.4×109 cells/mL时,对应的最大吸附量分别是1.8701、2.3552和2.9833 mg/g,吸附的微生物量占总生物量的比例分别达到43.75%、53.97%和55.94%。A.ferrooxidans在线路板粉末表面的吸附行为符合吸附一级动力学模型。(3)为了验证脂多糖在吸附过程中作用,设计并验证了EDTA法去除A.ferrooxidans表面脂多糖的效果和对菌生长活性的影响。采用苯酚硫酸法对处理前后多糖测定结果表明,游离的多糖量分别为50.14μg/1010cells和563.14ug/1010cells。同时,采用钌红染料吸附法进一步验证了上述剥离的脂多糖量,处理前后细菌的钌红吸附量分别27.9mg/1012cells和7.46mg/1012cells。统计分析表明,EDTA法能有效去除A.ferrooxidans表面的脂多糖(P0.05)。EDTA法去除A.ferrooxidans表面脂多糖后会导致菌体生长活性的减弱,但经过一段时间的培养菌体又恢复其生长活性。(4)通过设计未处理组、EDTA处理组、EDTA+LPS处理组三组实验,采用Zeta电位和红外光谱技术,研究脂多糖对A.ferrooxidans在线路板粉末表面的吸附作用方式的影响。Zeta电位结果表明,0h到5h时,未反应组、EDTA处理组及EDTA+LPS处理组的等电点分别由2.5偏移到6.3左右、3.2偏移到4.2左右及2.8左右偏移到5.2;菌体与线路板粉末作用24h后,各实验组菌体的等电点均在6.0左右。表明,在A.ferrooxidans和线路板粉末吸附过程中,静电作用大于疏水力作用,吸附过程主要在静电力驱动下完成的。FTIR结果表明,0h、5h、24h,三组不同处理菌体表面均含有-CH3、-CH2、-CH、-CONH、COO-、-NH3、-NH2、-NH官能表面团,均含有一定量的蛋白质;0h时,仅未处理组菌体表面有特殊的官能团CH3CO-;5h时,三组菌表面均未发现特殊的官能团;24h时,三组菌体表面均存在特殊的官能团CH3CO-。表明,在A.ferrooxidans和线路板粉末吸附过程中,脂多糖参与菌体在线路板粉末表面的吸附过程,且参与吸附过程的可能主要官能团为乙酰基;此外,蛋白质在菌体吸附到线路板粉末过程中可能也发挥一定作用。
[Abstract]:In recent years, Bioleaching Technology has attracted wide attention. At present, the research on the leaching of valuable metals from waste circuit boards mainly focuses on the leaching conditions such as initial Fe2+ concentration, initial pH value, powder dosage and inoculation amount. The leaching mechanism of metals in PCB by sexual bacteria is generally based on the achievements in the field of leaching. However, most of the valuable metals in PCB are zero valent, and the leaching mechanism is seldom studied, especially the adsorption behavior, adsorption kinetics and adsorption mechanism. The adsorption behavior and kinetics of bacteria on the surface of PCB powders were investigated by using lipopolysaccharide as a representative substance. The main results are as follows: (1) Bioleaching mechanism of PCB powders was verified by chemical leaching, different initial ferrous concentration and dialysis bag test. The results showed that the leaching rate of copper in the chemical leaching group was only 2.3% while that in the biological leaching group was 83.8%. The leaching rate of copper in the dialysis bag was only 47.9% because of the barrier of direct contact between bacteria and metal powder, while that in the non-dialysis bag group was 81.43%. The contact leaching mechanism plays an important role in the bioleaching process. Adsorption is the first step of contact leaching, which means that there may be adsorption behavior between PCB powder and bacteria. (2) The adsorption rows of copper in PCB leached by inoculating different concentrations of Thiobacillus ferrooxidans were investigated. The results showed that A. ferrooxidans adsorbed on the powder surface of the circuit board and reached equilibrium within 5 h. With the increase of the initial bacterial concentration, the adsorption rate and biomass increased. The initial bacterial concentration was 2. When the adsorption capacity was 1.8701, 2.3552 and 2.9833 mg/g respectively, the proportion of the total biomass to the total biomass reached 43.75%, 53.97% and 55.94%. The adsorption behavior of A. ferrooxidans on the powder surface of circuit board conformed to the first-order kinetic model of adsorption. (3) In order to verify the adsorption of lipopolysaccharides on the circuit board, the adsorption behavior of lipopolysaccharides on the powder surface of circuit board accounted for 43.75%, 53.97% and 55.94% respectively. The effect of EDTA method on the removal of lipopolysaccharides from A. ferrooxidans and the effect on the growth activity of A. ferrooxidans were designed and verified. The amount of lipopolysaccharide stripped from A. ferrooxidans was 27.9 mg/1012 cells and 7.46 mg/1012 cells respectively. Statistical analysis showed that EDTA method could effectively remove lipopolysaccharide from A. ferrooxidans surface (P 0.05). After removing lipopolysaccharide from A. ferrooxidans surface by EDTA method, the growth activity of A. ferrooxidans was weakened, but after a period of culture. (4) Zeta potential and infrared spectroscopy were used to study the effect of lipopolysaccharides on the adsorption of A. ferrooxidans on the surface of circuit board powder. Zeta potential showed that the unreacted group, EDTA treatment group and EDTA + LPS treatment group had no effect on the adsorption of A. ferrooxidans on the surface of circuit board powder from 0 h to 5 H. The isoelectric point of the treatment group was shifted from 2.5 to 6.3, 3.2 to 4.2 and 2.8 to 5.2, respectively. After 24 hours of interaction with PCB powder, the isoelectric point of each experimental group was about 6.0. FTIR results showed that the surface of three groups of bacteria with different treatments contained a certain amount of protein at 0 h, 5 h, 24 h, and - CH3, - CH2, - CH, - CONH, COO -, - NH3, - NH2, - NH functional surface groups; at 0 h, only the surface of the untreated bacteria had a special functional group CH3CO -; at 5 h, no special functional groups were found on the surface of the three groups of bacteria; at 24 h, three groups of bacteria had no special functional groups. CH3CO-, a special functional group, was found on the surface of both A. ferrooxidans and PCB powders. The results showed that LPS participated in the adsorption process of PCB powders, and the main functional group involved in the adsorption process was acetyl group. In addition, protein might also play a role in the process of bacteria adsorbing to PCB powders. A certain effect.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X705;X172

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