嗜酸性細(xì)菌浸出線路板的吸附行為、動(dòng)力學(xué)及機(jī)理研究
發(fā)布時(shí)間：2018-09-09 09:16
【摘要】：電子廢棄物特別是廢舊線路板中含有豐富的金屬資源,具有很大的回收價(jià)值。近年來(lái),生物浸出技術(shù)引起了廣泛關(guān)注。目前,廢舊線路板中有價(jià)金屬浸出的研究主要集中在初始Fe2+離子濃度、初始pH值、粉末投加量、接種量等浸出條件。嗜酸性細(xì)菌浸出線路板中金屬的機(jī)理一般借鑒浸礦領(lǐng)域的成果,但是線路板中的有價(jià)金屬大多為零價(jià),其浸出機(jī)理的研究很少,特別是吸附行為、吸附動(dòng)力學(xué)及吸附機(jī)理有待深入研究。因此,本研究在驗(yàn)證存在接觸浸出機(jī)制的基礎(chǔ)上,研究了菌體在線路板粉末表面的吸附行為和動(dòng)力學(xué)特性,以脂多糖為代表物質(zhì)驗(yàn)證了其在吸附過(guò)程中的作用及可能的吸附機(jī)制。主要結(jié)果如下:(1)通過(guò)化學(xué)浸出、不同初始亞鐵濃度、透析袋實(shí)驗(yàn),驗(yàn)證了生物浸出線路板粉末機(jī)制并考察了吸附在接觸浸出機(jī)制中的作用。結(jié)果表明,化學(xué)浸出組銅的浸出率僅為2.3%,而生物浸出組為83.8%。透析袋阻隔細(xì)菌與金屬粉末的直接接觸導(dǎo)致其銅浸出率僅為47.9%,而未加透析袋組銅的浸出率為81.43%。這表明,生物浸出包含接觸浸出和非接觸浸出兩種機(jī)制類型,接觸浸出機(jī)制在生物浸出過(guò)程起著重要作用。其中,吸附是接觸浸出發(fā)生的第一步,這意味著線路板粉末可能會(huì)與細(xì)菌存在吸附行為。(2)通過(guò)考察接種不同濃度氧化亞鐵硫桿菌(A.ferrooxidans)浸出線路板中銅的吸附行為,探索了菌體在線路板粉末表面的吸附過(guò)程,分析了其吸附行為的動(dòng)力學(xué)特性。結(jié)果顯示,A.ferrooxidans在線路板粉末表面存在吸附,且于5 h內(nèi)達(dá)到平衡。隨著初始菌濃度的增大,吸附速率和吸附的微生物量也隨之增大。當(dāng)初始菌體濃度為2.4×105、2.4×107和2.4×109 cells/mL時(shí),對(duì)應(yīng)的最大吸附量分別是1.8701、2.3552和2.9833 mg/g,吸附的微生物量占總生物量的比例分別達(dá)到43.75%、53.97%和55.94%。A.ferrooxidans在線路板粉末表面的吸附行為符合吸附一級(jí)動(dòng)力學(xué)模型。(3)為了驗(yàn)證脂多糖在吸附過(guò)程中作用,設(shè)計(jì)并驗(yàn)證了EDTA法去除A.ferrooxidans表面脂多糖的效果和對(duì)菌生長(zhǎng)活性的影響。采用苯酚硫酸法對(duì)處理前后多糖測(cè)定結(jié)果表明,游離的多糖量分別為50.14μg/1010cells和563.14ug/1010cells。同時(shí),采用釕紅染料吸附法進(jìn)一步驗(yàn)證了上述剝離的脂多糖量,處理前后細(xì)菌的釕紅吸附量分別27.9mg/1012cells和7.46mg/1012cells。統(tǒng)計(jì)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表面脂多糖后會(huì)導(dǎo)致菌體生長(zhǎng)活性的減弱,但經(jīng)過(guò)一段時(shí)間的培養(yǎng)菌體又恢復(fù)其生長(zhǎng)活性。(4)通過(guò)設(shè)計(jì)未處理組、EDTA處理組、EDTA+LPS處理組三組實(shí)驗(yàn),采用Zeta電位和紅外光譜技術(shù),研究脂多糖對(duì)A.ferrooxidans在線路板粉末表面的吸附作用方式的影響。Zeta電位結(jié)果表明,0h到5h時(shí),未反應(yīng)組、EDTA處理組及EDTA+LPS處理組的等電點(diǎn)分別由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;菌體與線路板粉末作用24h后,各實(shí)驗(yàn)組菌體的等電點(diǎn)均在6.0左右。表明,在A.ferrooxidans和線路板粉末吸附過(guò)程中,靜電作用大于疏水力作用,吸附過(guò)程主要在靜電力驅(qū)動(dòng)下完成的。FTIR結(jié)果表明,0h、5h、24h,三組不同處理菌體表面均含有-CH3、-CH2、-CH、-CONH、COO-、-NH3、-NH2、-NH官能表面團(tuán),均含有一定量的蛋白質(zhì);0h時(shí),僅未處理組菌體表面有特殊的官能團(tuán)CH3CO-;5h時(shí),三組菌表面均未發(fā)現(xiàn)特殊的官能團(tuán);24h時(shí),三組菌體表面均存在特殊的官能團(tuán)CH3CO-。表明,在A.ferrooxidans和線路板粉末吸附過(guò)程中,脂多糖參與菌體在線路板粉末表面的吸附過(guò)程,且參與吸附過(guò)程的可能主要官能團(tuán)為乙酰基;此外,蛋白質(zhì)在菌體吸附到線路板粉末過(guò)程中可能也發(fā)揮一定作用。
[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.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X705;X172
本文編號(hào)：2231959
[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.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X705;X172
【參考文獻(xiàn)】
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