ABSTRACT
Biohydrometallurgy is generally considered as a green technology for the recycling of industrial solid waste. In this study, an indigenous fungal strain named Y5 with the ability of high-yielding organic acids was isolated and applied in bioleaching of waste printed circuit boards (PCBs). The strain Y5 was identified as Penicillium chrysogenum by morphological and molecular identification. Meanwhile, we investigated that an optimal set of culturing conditions for the fungal growth and acids secretion was 15 g/L glucose with initial pH 5.0, temperature 25°C and shaking speed 120 rpm in shaken flasks culture. Moreover, three bioleaching processes such as one-step, two-step and spent medium processes were conducted to extract copper from waste PCBs. Spent medium bioleaching showed higher copper extraction percentage and it was 47% under 5%(w/v) pulp density. Transmission electron microscope (TEM) observation combining with energy dispersive analysis of X-rays (EDAX) showed that the leached metal ions did not obviously damage the hypha cells. All above results indicated that P.chrysogenum strain Y5 has the tolerance to metal ions, suggesting its potential in recycling of metals from waste PCBs in industry.
Subject(s)
Copper/pharmacokinetics , Electronic Waste , Industrial Waste , Penicillium chrysogenum/isolation & purification , Penicillium chrysogenum/metabolism , Recycling/methods , Biodegradation, Environmental , Copper/analysis , Copper/isolation & purification , Green Chemistry Technology/methods , Metallurgy/methods , Metals, Heavy/chemistry , Metals, Heavy/isolation & purification , Metals, Heavy/pharmacokinetics , Microscopy, Electron, Transmission , Penicillium chrysogenum/cytology , Soil Pollutants/chemistry , Soil Pollutants/isolation & purification , Soil Pollutants/pharmacokineticsABSTRACT
To study the effect of heavy metal pollution on microbial communities, microbial diversity and community structure of soils near Qingshuitang industrial district in Zhuzhou, China, were analyzed by Illumina high-throughput sequencing technology. In this study, the microbial diversity and community relative abundance decreased with increased heavy metal pollution level. Proteobacteria (49.56%) were the most abundant phylum in all samples, followed by Chloroflexi (13.07%) and Acidobacteria (8.77%). The microbial community structures of all samples were similar. The overlap of OTUs was 52.64%, and the structures of the abundant OTUs subcommunities were more similar than the rare OTUs community structures were. Heavy metals caused increases in Proteobacteria and Chloroflexi and decreases in Acidobacteria and Nitrospirae. According to Spearman's correlation, Proteobacteria was significantly negatively correlated with Cr, whereas Chloroflexi was positively correlated with Cr. Cd, Cu, Pb, and Zn were significantly negatively correlated with Nitrospirae. These results showed that heavy metal pollution is an important factor affecting the soil microbial structure in the soil of the Qingshuitang industrial district.
Subject(s)
Bacteria/classification , Metals, Heavy/analysis , Microbiota , Soil Microbiology , Soil Pollutants/analysis , China , IndustryABSTRACT
To seek a feasible technique for processing waste printed circuit boards (PCBs), pretreatment of PCBs by table separation and further bioleached by moderate thermophiles in a stirred tank reactor were investigated. The shaking table separation, conducted after grinding and sieving of PCBs, produced two fractions: metal-rich parts (RPCBs), which is more suitable for pyrometallurgy process than untreated PCBs, and metal-poor parts (PPCBs) with only 8.83% metals was then bioleached by a mixed culture of moderate thermophiles effectively. After adaptation, the mixed culture could tolerate 80 g/L PPCBs. The bioleaching results showed that metals recovery was 85.23% Zn, 76.59% Cu and 70.16% Al in only 7 days. Trace Pb and Sn were detected in the leachate because of precipitating. The microorganism community structure was analyzed by amplified ribosomal DNA restriction analysis. Two moderately thermophilic bacteria species were identified as Leptospirillum ferriphilum and Acidithiobacillus caldus. Furthermore, uncultured Thermoplasmatales archaeon was also detected in the leaching system. It was also shown that moderate thermophiles revealed best bioleaching ability when compared with mesophiles and the mixture of mesophiles and moderate thermophiles. Finally, we designed a two-stage process model according to the present study to achieve semi-industrial waste PCBs recycling and economic feasibility analysis indicated that the process was profitable.
