Bacterial Mining

Abstract

Bacterial mining (biomining) represents the use of microorganisms to leach out metals from ores or mine tailings (wastes), followed by the subsequent recovery of metals of interest from the leaching solution. This leaching of metals from ores is a natural process, which can be considerably accelerated by inducing and/or supporting the microbial activity of certain species with the ability to solubilize metals. This process is usually known as biosolubilization and constitutes the basis of many remedial technologies for environments polluted with metals, and also providing the additional potential for recovery of any particular metal of interest. Bacterial mining is part of a vast research field that emerged relatively recently as a border science called biohydrometallurgy. This research field became very important in the context of raw material crises on which technological crises is grafted. In other words, the conventional technologies operating for metal extraction, mainly in the case of lower grade ores, are generally disruptive and less cost-efficient when compared to biomining. Thus, during the last 10–15 years, the interest in biohydrometallurgy, and subsequently in bacterial mining, has increased. The focus has been on two main topics—mineral bioprocessing and biorecovery.     

Aquathermolysis of heavy oil in reservoir conditions with the use of oil-soluble catalysts: part I – changes in composition of saturated hydrocarbons

Abstract

This paper is devoted to the study of aquathermolysis processes of heavy oil produced by CSS technology on Boca de Jaruco oil field. Various catalysts based on cobalt, nickel, iron and copper were used for intensification of in-situ upgrading processes of heavy oil. The first paper in series is presented results of transformation of crude oil and its saturate fraction after thermal treatment with and without catalysts by SARA analysis, MALDI mass-spectrometry, FTIR-spectroscopy and gas chromatography. It is revealed, that catalysts provide more deep conversion of asphaltenes and resins into lighter hydrocarbons. Particularly, for the given heavy oil, catalysts based on iron and nickel organic salts are more effective to reduce the content of high molecular weight components (asphaltenes). Saturates fraction after thermal treatment in presence of the catalysts is enriched with lighter alkanes in comparison to the crude oil treated without catalysts. Obtained results show that crude oil recovered by catalytic aquathermolysis processes will be better quality than the original oil in the place.     

β-环糊精交联聚合物对铜、铅和锌的吸附性能

β-环糊精经微波法酰化制得丙烯酸β-环糊精酯(β-CD-AA),再与烯丙基-联苯基醚(ABE)、丙烯酰胺(AM)、N,N-亚甲基双丙酰胺共聚合成β-CD交联聚合物AM/ABE/β-CD-AA,分别采用FTIR和TG技术对其结构和热稳定性进行了表征。以该聚合物为吸附剂,考察了金属离子溶液初始质量浓度、吸附温度及体系pH等条件对Cu2+,Pb2+,Zn2+吸附性能的影响。实验结果表明,AM/ABE/β-CD-AA共聚物对Cu2+,Pb2+,Zn2+的静态吸附量不同,其中,对Zn2+的吸附性能较为突出:在35℃、Zn2+初始质量浓度200mg/L、体系pH=3～4时,最大静态吸附量达50.1mg/g;AM/ABE/β-CD-AA共聚物对Cu2+,Pb2+,Zn2+的吸附符合Freundlich吸附等温方程。     

Analysis of environmental chemical residues in products of emerging aquaculture industry in Uganda as case study for Sub-Saharan Africa

A study was conducted to analyse market-regulated heavy metals (lead, mercury and cadmium), organochlorine pesticides and total polychlorinated biphenyls (PCBs) in samples of 38 farmed fish comprising Nile tilapia (Oreochromis niloticus) (20 samples) and African catfish (Clarias gariepinus) (18 samples) from ten selected fish farms in Uganda. The goal of this case study was to understand the safety of aquaculture products from Sub-Saharan Africa. Lead was detected in all the 38 samples (maximum = 1.08 mg kg^?1 (dry weight)), mercury in 31 out of 38 samples (maximum = 0.35 mg kg^?1 (dry weight)), and cadmium in two samples (maximum = 0.03 mg kg^?1 (dry weight)). Total levels of PCBs were below the limit of detection of 0.02 mg kg^?1 (wet weight) in all the samples. Traces of 4,4′-dichloro-diphenyldichloroethylene (DDE) were detected in ten out of 38 samples (maximum = 0.01 mg kg^?1 (wet weight)) making it the most prevalent organochlorine pesticide. Other pesticides detected were: 4,4′-dichloro-diphenyl-trichloroethane (DDT) and endosulfan sulphate, which were found in one fish sample (both 0.002 mg kg^?1 (wet weight)). There was no statistically significant difference between the levels of lead and mercury in catfish and tilapia (t-test at p = 0.05). More catfish samples (eight) contained DDE as compared with tilapia (two). Cadmium, DDT and endosufan sulphate were only detected in catfish implying that catfish is more prone to contamination than tilapia. The levels of contaminants were below the US Food and Drug Administration (USFDA) action levels and European Union maximum residue limits (MRLs), indicating that such fish have the potential for export to these markets.     

A survey of selected essential and heavy metals in milk from different regions of Egypt using ICP-AES

The aim of this paper was to assess the content of selected essential metals (Fe, Zn, Cu and Cr) and some heavy metals (Pb and Cd) in raw cow's milk collected from different Egyptian areas during different periods of one year (January–February, May–June and September–October 2009). Twenty-one samples of raw milk were analysed using inductively coupled plasma–atomic emission spectrometry for quantitative determination. The highest metal accumulation levels for Cd, Cr, Fe and Cu are found in milk samples collected from Shubra, while samples from Menofia and Tanash are high in Pb and Zn, respectively. On the other hand, the highest metal accumulation levels were during January–February for Cd, Cr and Zn. In the period of May–June, the content of Pb, Cu and Fe were the highest, while the samples during the September–October period are characterised by the lowest metal content.     

Lead,cadmium and chromium in raw and boiled portions of Norway lobster

Lead, cadmium and chromium levels were determined in different raw and boiled portions of Norway lobster caught in the central Adriatic Sea (Italy). In raw specimens, the lowest concentrations were always detected in the white meat. Lead and cadmium content in the edible portion never exceeded the maximum levels set by European legislation. The highest cadmium and chromium values (0.47 ± 0.04 and 0.62 ± 0.13 mg/kg wet weight, respectively) were detected in the brown meat, while the highest lead concentrations were found in the exoskeleton (0.21 ± 0.01 mg/kg wet weight). Also, the boiled samples showed the lowest metal levels in the white meat, even if a significant increase (p < 0.01) was found for lead and cadmium compared to the corresponding raw portions. Among metals, chromium showed the highest concentrations in both raw and boiled portions, but up to now, the European legislation did not envisage any limits in seafood.     

Toxic metal content in 52 frequently prescribed herbal medicines on the Korean market

This study was conducted to investigate the toxic metal content (Pb, As, Cd and Hg) of 52 frequently prescribed herbal medicines and to identify herbal medicines that exceed the Korea Food and Drug Administration (KFDA) maximum limits. A total of 3534 samples, including 1966 domestic samples and 1568 imported samples, were analysed using an Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Total amounts of Pb, As, Cd and Hg were significantly different between domestic (0.63 mg kg^?1) and imported (0.81 mg kg^?1) medicines (p < 0.05). Among the 52 kinds of samples, 4 kinds of herbs required quality control for Pb and 12 kinds of herbs required quality control for Cd. No sample contained As and Hg above the limits.     

Mercury and methylmercury bioaccessibility in swordfish

Concentrations of mercury (Hg) in swordfish (Xiphias gladius) present a food safety problem for many countries. This study analyses total Hg (t-Hg) concentrations in 27 samples of swordfish marketed in Spain in 2005 and in their bioaccessible fractions (soluble concentration in gastrointestinal medium), obtained after applying an in vitro digestion method. Methylmercury (MeHg) was also determined in the bioaccessible fractions. t-Hg concentrations in the samples were 0.41–2.11 mg kg^?1 wet weight, with a mean of 0.96 ± 0.47 mg kg^?1 wet weight. A total of 37% of the samples exceeded the Hg limit set by Spanish legislation (1.0 mg kg^?1 wet weight). Bioaccessible t-Hg concentrations were 0.17–1.72 mg kg^?1 wet weight (0.63 ± 0.4 mg kg^?1 wet weight), corresponding to 38–83% (64% ± 14%) of t-Hg. Bioaccessible MeHg concentrations, representing 94% of the bioaccessible t-Hg concentrations, were 0.16–1.53 mg kg^?1 wet weight, with a mean of 0.49 ± 0.32 mg kg^?1 wet weight. Children and adults who regularly consume this product in Spain have Hg and MeHg intakes that exceed the tolerable daily intake limits recommended by the Food and Agricultural Organization/World Health Organization (FAO/WHO) and US Environmental Protection Agency (USEPA). These results show the need for recommendations about swordfish consumption by population groups at risk in Spain.     

Occurrence of NDL-PCBs,DL-PCBs,PCDD/Fs,lead and cadmium in feed and in rainbow trout (Oncorhynchus mykiss) farmed in Italy

The safety of farmed rainbow trout (Oncorhynchus mykiss) is correlated with the quality of the production process. Polychlorinated biphenyls (PCBs), dioxins (polychlorinated dibenzodioxins and furans – PCDD/Fs), and heavy metals such as lead and cadmium were investigated because they can represent a risk for the consumer. The levels of these compounds in water, feed and specimens of trout farmed with two different feeds (A and B) were assessed. Their accumulation in muscle of A and B trout was evaluated and their dependence on the levels of feed contamination was considered. The results showed a widespread contamination in feed and in the examined trout, although lower than the European Union limits. For all compounds, concentrations in the farming waters were always < LOQs. Mean concentrations of NDL-PCBs in the A feed were significantly higher than in the B feed, except for PCBs 52 and 28. DL-PCB and PCDD/F concentrations were significantly higher in A feed. Lead and cadmium mean concentrations in A feed were 0.26 ± 0.01 and 0.1013 ± 0.0009 µg g^–1, respectively; and in B feed were 0.10 ± 0.01 and 0.0855 ± 0.0078 µg g^–1, respectively. The results showed that intakes for ∑DL-PCB + ∑PCDD/F ranged from 4.4% to 12% of the TDI, and for Pb and Cd from 1.9% to 2.7% and from 0.3% to 0.4% of the TDI, respectively.     

Levels of eight trace elements in edible mushrooms from a rural area

Eight trace elements were determined using ICP–MS in 78 fruiting body samples of 22 edible mushroom species. The mushrooms were collected from four sites in a rural area, unpolluted by human activity. Median values (dry matter) were as follows: Arsenic (As) 1.45?mg?kg^–1, barium (Ba) 1.41?mg?kg^–1, cobalt (Co) 0.28?mg?kg^–1, copper (Cu) 47.0?mg?kg^–1, rubidium (Rb) 130?mg?kg^–1, silver (Ag) 2.95?mg?kg^–1, thallium (Tl) 0.02?mg?kg^–1 and vanadium (V) 0.25?mg?kg^–1. Higher trace element accumulation was observed in samples of Macrolepiota procera, Macrolepiota rhacodes, Lycoperdon perlatum, Lycoperdon gigantea and Xerocomus chrysenteron for As and Cu, and in samples of Cantharellus cibarius and of genera Boletus and Suillus for Rb.