Cornstalk is usually directly used as a reductant in reductive leaching manganese. However, low utilization of cornstalk makes low manganese dissolution ratio. In the research, pretreatment for cornstalk was proposed to improve manganese dissolution ratio. Cornstalk was preprocessed by a heated sulfuric acid solution (1.2 M of sulfuric acid concentration) for 10 min at 80°C. Thereafter, both the pretreated solution and the residue were used as a reductant for manganese leaching. This method not only exhibited superior activity for hydrolyzing cornstalk but also enhanced manganese dissolution. These effects were attributed to an increase in the amount of reductive sugars resulting from lignin hydrolysis. Through acid pretreatment for cornstalk, the manganese dissolution ratio was improved from 50.14% to 83.46%. The present work demonstrates for the first time the effective acid pretreatment of cornstalk to provide a cost-effective reductant for manganese leaching.

A facultative anaerobic bacterium capable of generating electricity and degrading cyanide was isolated from a microbial fuel cell and was designated as MC-1. According to its morphological characteristics and the sequence analysis of 16S rDNA, the isolated bacterium was identified as a strain of Klebsiella sp. Cyclic voltammetry showed that the strain MC-1 exhibited high electrochemical activity. The preliminary electricity-production experiment showed that the strain MC-1 could use glucose–cyanide mixtures for electricity production in a microbial fuel cell (MFC). The maximum voltage was 412 mV, and the chemical oxygen demand (COD) removal rate and cyanide degradation rate were 88.34% and 99.51%, respectively, when the MFC was fed with glucose–cyanide mixtures. The results demonstrated that the strain MC-1 was promising for the bioremediation of cyanide-containing wastewater in MFCs.

In this paper, an approach of improving power generation of microbial fuel cells (MFCs) by using a HSO4− doped polyaniline modified carbon cloth anode was reported. The modification of carbon cloth anode was accomplished by electrochemical polymerization of aniline in 5% H2SO4 solution. A dual-chamber MFC reactor with the modified anode achieved a maximum power density of 5.16 W m−3, an internal resistance of 90 Ω, and a start-up time of 4 days, which was respectively 2.66 times higher, 65.5% lower, and 33.3% shorter than the corresponding values of the MFC with unmodified anode. Evidence from X-ray photoelectron spectroscopy and scanning electron microscopy results proved that the formation of biofilm on the anode surface could prevent the HSO4− doped polyaniline to be de-doped, and the results from electrochemical tests confirmed that the electrochemical activity of the modified anode was enhanced significantly after inoculation. Charge transfer was facilitated by polyaniline modification. All the results indicated that the polyaniline modification on the anode was an efficient approach of improving the performance of MFCs.

In microbial fuel cells (MFCs), the electron transfer from microorganisms to the cell anode is a decisive factor on the power output. Though quinone derivatives can function as electron shuttles, the electron shuttle pathways have so far not been demonstrated. In this paper, the mechanism of electron shuttle via an exogenous mediator was studied in MFCs using Geobacter metallireducens (G. metallireducens). 1-hydroxy-4-aminoanthraquinone was labeled by fluorescamine and the product (HAQ-F) showed strong and stable fluorescence. The addition of HAQ-F into MFCs increased cell voltage from 170 mV to 290 mV, suggesting that the redox mediator could facilitate electron transfer from bacteria to anode. Further, confocal laser scanning microscopy imaging indicated that HAQ-F was present in microbial cells, demonstrating that the redox mediator shuttled across the membranes to get reduced within cells.

Uranium-reducing bacteria were immobilized with sodium alginate, anthraquinone-2,6-disulfonate (AQDS), and carbon nanotubes (CNTs). The effects of different AQDS-CNTs contents, U(IV) concentrations, and metal ions on U(IV) reduction by immobilized beads were examined. Over 97.5% U(VI) (20 mg/L) was removed in 8 hr when the beads were added to 0.7% AQDS-CNTs, which was higher than that without AQDS-CNTs. This result may be attributed to the enhanced electron transfer by AQDS and CNTs. The reduction of U(VI) occurred at initial U(VI) concentrations of 10 to 100 mg/L and increased with increasing AQDS-CNT content from 0.1% to 1%. The presence of Fe(III), Cu(II) and Mn(II) slightly increased U(VI) reduction, whereas Cr(VI), Ni(II), Pb(II), and Zn(II) significantly inhibited U(VI) reduction. After eight successive incubation-washing cycles or 8 hr of retention time (HRT) for 48 hr of continuous operation, the removal efficiency of uranium was above 90% and 92%, respectively. The results indicate that the AQDS-CNT/AL/cell beads are suitable for the treatment of uranium-containing wastewaters.Anthraquinone-2,6-disulfonate (AQDS) and carbon nanotubes (CNTs) were used to immobilized the uranium reducing bacteria with sodium alginate for U(IV) reduction.The immobilized beads in the presence of AQDS and CNTs were more effective than free cells and immobilized beads without containing AQDS and CNTs. This is attributed to an enhanced electron transfer. Results indicate that the AQDS-CNT/AL/cell beads would be applicable to the treatment of uranium-containing wastewaters.Download full-size image