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Abstract: The electrochemical behaviors of a marmatite – carbon paste electrode with the chemical leaching of Fe3+ ions, or the microbial leaching using Acidithiobacillus ferrooxidans, were compared. The cyclic voltammograms of the electrode in the presence and absence of bacterial strains showed that the leaching process of marmatite was carried out by the different reactions occurring in the interface of the marmatite electrode — leach liquid. The polarization currents of the electrode under the differently applied potentials suggested that the microbial leaching of marmatite could be accelerated by the applied potential. The SEM observations indicated that the corrosion pits formed in the electrode surface were similar to the attached bacterial cells in shape and size, other than that by the chemical leaching of Fe3+ ions. The contact leaching of the attached cells on the mineral substrate played an important role on the dissolution of marmatite in addition to the chemical leaching of Fe3+ ions. [Copyright &y& Elsevier]

Abstract: The electrochemical behavior of marmatite–carbon paste electrode in the presence and absence of Acidithiobacillus ferrooxidans was investigated by electrochemical impedance spectroscopy (EIS) measurement. The effects of the concentration of Fe3+ ions, bacterial strain and temperature on the EIS spectra of the marmatite electrode were examined. The experimental data indicated that the impedance diagrams of the marmatite electrode in the different electrolytes had the similar features with two semicircles in the higher frequency range and a line in the lower frequency range. An equivalent circuit has been considered for the analysis of the EIS spectra of the marmatite electrode in the solution of 10g/L Fe2+ ions without and with microorganisms. The fitting of experimental data along with a preliminary estimation for the characteristic parameters of the impedance model could validate the proposed mechanism, which suggested that the dissolution of marmatite proceeded by the similar kinetic processes occurring in the marmatite–solution interface in the different systems during the leaching process. [Copyright &y& Elsevier]

Abstract: The treatment of Be-contaminated wastewater has been paid little attention, although beryllium (Be) and its compounds are of high toxicity. In this research, aerobic granule was for the first time introduced to remove Be from aqueous solution. Influencing factors including reaction time, initial Be concentration, pH, biosorbent dosage, and coexistent metal ions (Cd, Cu, and Fe) were investigated in batch experiments. The aerobic granule, characterized by element analysis and CLSM, was abundant in carboxyl, phosphoryl, amine and hydroxyl groups. Potentiometric titration experiment demonstrated that the pH effect on biosorption depended on the surface charge of granule (pHzpc =2.4) and the species of Be (Be2+, Be(OH)+, and Be(OH)2) in solution. The coexistent metal ions would either inhibit Be uptake through competitive biosorption or promote Be uptake via coprecipitation, depending on the K sp of coexistent metals. Kinetic and isotherm modeling studies revealed that the experiment data could be well described by pseudo-second-order model and Langmuir isotherm, respectively. The maximum biosorption capacity obtained in this experiment was 14.0mg/g. The sequential extraction test and XPS analysis suggested that precipitation and ion exchange were the dominant mechanisms under the experimental conditions, and FTIR analysis revealed that functional groups like carboxyl and hydroxyl played an important role in the biosorption of Be. [Copyright &y& Elsevier]

Abstract: Based on energetic analysis, a novel approach for copper electrodeposition via cathodic reduction in microbial fuel cells (MFCs) was proposed for the removal of copper and recovery of copper solids as metal copper and/or Cu2O in a cathode with simultaneous electricity generation with organic matter. This was examined by using dual-chamber MFCs (chamber volume, 1L) with different concentrations of CuSO4 solution (50.3±5.8, 183.3±0.4, 482.4±9.6, 1007.9±52.0 and 6412.5±26.7mg Cu2+/L) as catholyte at pH 4.7, and different resistors (0, 15, 390 and 1000Ω) as external load. With glucose as a substrate and anaerobic sludge as an inoculum, the maximum power density generated was 339mW/m3 at an initial 6412.5±26.7mg Cu2+/L concentration. High Cu2+ removal efficiency (>99%) and final Cu2+ concentration below the USA EPA maximum contaminant level (MCL) for drinking water (1.3mg/L) was observed at an initial 196.2±0.4mg Cu2+/L concentration with an external resistor of 15Ω, or without an external resistor. X-ray diffraction analysis confirmed that Cu2+ was reduced to cuprous oxide (Cu2O) and metal copper (Cu) on the cathodes. Non-reduced brochantite precipitates were observed as major copper precipitates in the MFC with a high initial Cu2+ concentration (0.1M) but not in the others. The sustainability of high Cu2+ removal (>96%) by MFC was further examined by fed-batch mode for eight cycles. [Copyright &y& Elsevier]

Aerobic granules were utilized as an effective biosorbent to remove Cr3+ from aqueous solution. The results showed that the initial pH, contact time, and Cr3+ concentration affected the biosorption process significantly. Both Freundlich and Langmuir isotherms were able to describe the equilibrium data reasonably with high correlation coefficients (R 2 >0.95) and pseudo-second-order model best fitted the biosorption process at experimental conditions. Moreover, Environmental Scanning Electronic microscope (ESEM), X-ray energy dispersion (EDX), and Fourier transform infrared (FTIR) analyses revealed that metal complexation, chemical precipitation, and ion exchange were involved in the removal of Cr3+ with aerobic granules. Further analysis by a metal ion fraction test demonstrated that metal complexation could be the dominant mechanism of biosorption, whereas chemical precipitation and ion exchange appeared only to have minor role in the overall Cr3+ biosorption process. [Copyright &y& Elsevier]