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Effect of Heavy Metal Co-Contaminants on Selenite Bioreduction by Anaerobic Granular Sludge
Published in Joyabrata Mal, Microbial Synthesis of Chalcogenide Nanoparticles, 2018
The use of sulfate reducing bacteria in metal bioremediation processes has been widely reported, for example, bioprecipitation as metal sulfide for cadmium (White et al., 1998), zinc and lead (Guo et al., 2010; Hien Hoa et al., 2007). However, to the best of our knowledge, there is no study on the effect of heavy metal co-contaminants on selenium oxyanion bioreduction or vice versa. Therefore, the objective of this work was to investigate microbial reduction of selenite in the presence of heavy metals. In this study, experiments were performed on selenite reduction by anaerobic granular sludge in the presence of different concentrations of three heavy metals, i.e. Cd(II), Zn(II) and Pb(II). Time course profiles of selenite removal along with the fate of bioreduced selenium and heavy metals were analyzed.
Value-Added Microbial Byproducts
Published in Volodymyr Ivanov, Environmental Microbiology for Engineers, 2020
Cellulose-containing wastes and iron ore mining dust can be used for the production of relatively cheap grout containing dissolved ferrous salts, urea, and urease. This technology combines the three following bioprocesses: acidogenic fermentation of cellulose-containing agricultural or food processing residuals with the production of mainly acetic acidsimultaneous bioreduction of hematite iron ore using products of acidogenic fermentation and iron-reducing bacteria:4Fe2O3+17CH3COOH→8Fe(CH3COOH)2(dissolved)+2CO2+10H2Obiooxidation and bioprecipitation of ferrous chelates using urea and urease or urease-producing bacteria:Fe2++1.5(NH2)2CO+0.25O2+5.5H2O+urease→Fe(OH)3↓+1.5(NH4)2CO3+2H+
The use of seawater in mining
Published in Mineral Processing and Extractive Metallurgy Review, 2018
Luis A. Cisternas, Edelmira D. Gálvez
An alternative to the use of desalinated water and raw seawater is partial desalination in order to eliminate or reduce the presence of species that cause problems in the extractive metallurgical processes. Although this alternative has not been, effectively, implemented, different studies have considered this alternative. Most of them focus on the reduction of calcium and/or magnesium ions from seawater because the high salinity of seawater is not the main problem in the flotation of sulfide copper ores but the presence of those ions. The presence of those ions produces a reduction in the recovery of molybdenite in minerals Cu-Mo (Castro et al., 2014; Castro and Laskowski, 2015) because of the precipitation of colloids, and can reduce molybdenum grade in the concentrate for the coprecipitation of CaSO4 (Lucay et al., 2015). Recently, Uribe et al., (2017) have shown that the presence of magnesium and calcium cations can reduce de recovery of chalcopyrite if kaolinite is also present in the ore. Proposals for the reduction of calcium and magnesium from seawater include proposals to precipitate them using lime or other alkalinizing agent (Castro, 2010), alkalinizing agent mixture (Jeldres et al., 2017a), alkalinizing agent mixture/CO2 (Cruz et al., 2016; Zhao et al., 2013), and bioprecipitation with bacteria (Arias et al., 2017). A study by Concha et al. (2016) compares the costs of using desalinated seawater by reverse osmosis (SWRO), raw seawater (SW), and seawater pre-treated with lime (TSW) in the context of the Chilean scenario. For this purpose, they considered a mining plant located 160 km from the coast and 3,500 m.a.s.l., and whose water demand is 1,157 L/s. The study includes CAPEX and OPEX cost of seawater treatment technology (intake and outfall structures) and the seawater conveyance system (pipelines and pumping system). Water costs at the treatment plant are 1.42, 0.47, and 0.30 USD/m3 for SWRO, TSW, and SW, respectively. It is then clear that the use of raw seawater is the cheapest; however, this requires changes in the process and transport that add other costs. The precipitation of Mg and Ca appears then as a very promising option, especially if more efficient ways or processes are considered. Water transportation costs are significant due to the high altitude at which copper mines are located in Chile. Therefore, considering the water cost at the flotation plant, the costs are 5.58, 4.70 and 4.53 USD/m3 for SWRO, TSW, and SW respectively. Then the seawater distribution system requires more studies to improve its efficiency.