MoS2 nanosheets embedded in α-FeOOH as an efficient cathode for enhanced MFC-electro-Fenton performance in wastewater treatment.

Microbial fuel cell-electro-Fenton system (MEF) has attracted attention due to refractory organic pollutants removal, where H2O2 is in-situ produced without external energy supply. Enhancement of H2O2 production and the activation of H2O2 to ·OH are the keys to improve degradation performance. Development of bifunctional catalytic cathode is a viable strategy. Herein, the α-FeOOH/MoS2 nanocomposites was fabricated by a novel facile hydrothermal method based on molybdenite-exfoliated MoS2 nanosheets suspension, which was used as modified cathode in a MEF system. The obtained α-FeOOH/1 wt%MoS2 cathode exhibited highest power density of 292.38 mW/m2, which was about 3.7 and 1.7 times higher than that of graphite plate and α-FeOOH, respectively. Doping of MoS2 nanosheets significantly enhanced electrocatalytic activity of the cathode and promoted in-situ H2O2 generation. Meanwhile, the exposed reductive Mo4+ on the surface of MoS2 could greatly facilitate the conversion cycle of Fe(III)/Fe(II), leading to the efficient activation of H2O2 into ·OH. The MEF with α-FeOOH/1 wt%MoS2 cathode exhibited excellent degradation and mineralization performance for MB, rhodamine B and tetracycline hydrochloride at optimized reaction condition. Furthermore, the MEF can simultaneously achieve MB oxidation and Cr(VI) reduction, and the corresponding removal ratio can reach up to 91.45% and 100%, respectively. Based on simple preparation method as well as recyclability and excellent catalytic property, the α-FeOOH/MoS2 composite catalyst is considered as a promising MEF cathode for efficient wastewater treatment.

Flocculation characteristics of a bioflocculant produced by the actinomycete Streptomyces sp. hsn06 on microalgae biomass.

BACKGROUND: Microbial flocculation is a good choice for harvest of microalgae biomass, which has gained extensive attention. There have been carried out massive studies in bacterial flocculation, many bacterial strains with flocculation activity were isolated and different types of bioflocculants were produced. However, harvest of algal biomass by bioflocculants which produced from actinomycete are deficiency. In this study, the bioflocculant from an actinomycete Streptomyces sp. hsn06 could be used to harvest Chlorella vulgaris biomass. RESULTS: Consecutive treatment with 20 mg·L- 1 bioflocculant and 5 mM CaCl2 for 5 min showed the highest flocculating activity. The bioflocculant was a nonprotein substance with thermal stability and pH stability, which can be used in comprehensive applications. Chemical analysis of the bioflocculant indicated that it is a small molecule substance of moderate polarity with containing triple bond and cumulated double bonds. Algal temperature, pH, and metal ions showed great effects on the flocculation efficiency of the bioflocculant. CONCLUSIONS: The bioflocculant produced by Streptomyces sp. hsn06 possesses the potential to harvest algal biomass with high-efficiency.