A mini-review on membrane fouling

One-step removal of Cr(VI) at alkaline pH by UV/sulfite process: Reduction to Cr(III) and in situ Cr(III) precipitation

A comprehensive study on membrane fouling in submerged membrane bioreactors operated under different aeration intensities

Membrane fouling in a membrane bioreactor: High filtration resistance of gel layer and its underlying mechanism

Lithium–sulfur battery possesses high energy density but suffers from severe capacity fading due to the dissolution of lithium polysulfides. Novel design and mechanisms to encapsulate lithium polysulfides are greatly desired by high-performance lithium–sulfur batteries towards practical applications. Herein, we report a strategy of utilizing anthraquinone, a natural abundant organic molecule, to suppress dissolution and diffusion of polysulfides species through redox reactions during cycling. The keto groups of anthraquinone play a critical role in forming strong Lewis acid-based chemical bonding. This mechanism leads to a long cycling stability of sulfur-based electrodes. With a high sulfur content of ~73%, a low capacity decay of 0.019% per cycle for 300 cycles and retention of 81.7% over 500 cycles at 0.5 C rate can be achieved. This finding and understanding paves an alternative avenue for the future design of sulfur–based cathodes toward the practical application of lithium–sulfur batteries. Novel cathode design holds the key to enabling high performance lithium-sulfur batteries. Here the authors utilize anthraquinone to chemically stabilize polysulfides, revealing that the keto groups of anthraquinone play a critical role in forming strong Lewis acid-based chemical bonding.

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Chemisorption of polysulfides through redox reactions with organic molecules for lithium–sulfur batteries

Cr(VI) biotreatment has attracted a substantial amount of interest due to its cost effectiveness and environmental friendliness. However, the slow Cr(VI) bioreduction rate and the formed organo-Cr(III) in solution are bottlenecks for biotechnology application. In this study, a novel strain, Acinetobacter sp. HK-1, capable of reducing Cr(VI) and immobilizing Cr(III) was isolated. Under optimal conditions, the Cr(VI) reduction rate could reach 3.82 mg h(-1) g cell(-1). To improve the Cr(VI) reduction rate, two quinone/graphene oxide composites (Q-GOs) were first prepared via a one-step covalent chemical reaction. The results showed that 2-amino-3-chloro-1,4-naphthoquinone-GO (NQ-GO) exhibited a better catalytic performance in Cr(VI) reduction compared to 2-aminoanthraquinone-GO. Specifically, in the presence of 50 mg L(-1) NQ-GO, a Cr(VI) removal rate of 190 mg h(-1) g cell(-1), which was the highest rate obtained, was achieved. The increased Cr(VI) reduction rate is mainly the result of NQ-GO significantly increasing the Cr(VI) reduction activity of cell membrane proteins containing dominant Cr(VI) reductases. X-ray photoelectron spectroscopy analysis found that Cr(VI) was reduced to insoluble Cr(III), which was immobilized by glycolipids secreted by strain HK-1. These findings indicate that the application of strain HK-1 and NQ-GO is a promising strategy for enhancing the treatment of Cr(VI)-containing wastewater.

Cr(VI) reduction and Cr(III) immobilization by Acinetobacter sp. HK-1 with the assistance of a novel quinone/graphene oxide composite.

Cake layer morphology in microfiltration of activated sludge wastewater based on fractal analysis

A novel quinone-modified graphene material was developed to enhance the catalytic performance of graphene for the transformation of environmental pollutants. Graphene oxide (GO) was first reduced with diethylenetriamine and the obtained NH2-RGO was further covalently modified with anthraquinone-2-sulfonic acid (AQS). The prepared AQS-modified RGO (AQS-RGO) was characterized by XPS, IR and SEM, respectively. The catalytic performance of AQS-RGO was investigated during azo dye Acid Yellow 36 (AY 36) decolorization. It was shown that pH and temperature had significant effects on AY 36 chemical decolorization by Na2S. At the pH of 6.0, AQS-RGO exhibited better catalytic performance compared with NH2-RGO due to the lower activation energy of the AQS-RGO amended system. AY 36 bio-decolorization could be enhanced in a dose-dependent manner with AQS-RGO. In the presence of 25 mg L−1 AQS-RGO, the AY 36 bio-decolorization rate was 6.7-fold higher than that mediated by NH2-RGO, indicating that AQS-RGO is a better electron-transfer mediator. Based on the above results, the electron transfer pathways of AQS-RGO-mediated AY 36 decolorization were proposed. These findings indicate that the application of AQS-RGO is a feasible method to enhance the treatment of azo dye-containing wastewater.

A novel quinone/reduced graphene oxide composite as a solid-phase redox mediator for chemical and biological Acid Yellow 36 reduction

The immobilization of quinone compounds is regarded as a promising strategy to accelerate anaerobic decolorization of xenobiotic compounds azo dyes in the presence of quinone-reducing microorganisms. However, little is known about the basic response of these microorganisms to immobilized quinones in the presence of azo dyes. In the present study, whole-genome DNA microarrays were used to investigate a quinone-reducing bacterium Escherichia coli K-12 transcription response to immobilized anthraquinone-2-sulfonate (AQSim) reduction and azo dye acid red 18 (AR 18) decolorization. Transcriptome analysis showed that AQSim was more accessible for the cells of E. coli K-12 than AR 18. Despite there being some differences between AQSim and soluble AQS mediated decolorization of AR 18, AQSim reduction and AR 18 decolorization, more similarity could be observed in the four processes. Among over 60 % shared genes, several groups of genes exhibited high expression levels, including those genes encoding terminal reductases, menaquinone biosynthesis, formate dehydrogenases and outer membrane proteins. Especially, nrfABCD, frdBCD and dsmABC encoding terminal reductases were significantly upregulated. Further gene deletion experiments demonstrated that the above three groups of genes were involved in AQSim-mediated AR 18 decolorization. In addition, significant upregulation of stress response genes was observed, which indicated the adaptation of E. coli K-12 to AQSim and AR 18 exposures.

Global transcriptome analysis of Escherichia coli exposed to immobilized anthraquinone-2-sulfonate and azo dye under anaerobic conditions.

The invention discloses an oxidized graphene material modified by a water-soluble anthraquinone compound and a preparation method of the graphene material and belongs to the technical field of water treatment of environmental engineering. The mass percent of the water-soluble anthraquinone compound in the material is 1-5%. The preparation method comprises the following steps: dispersing oxidized graphene into de-ionized water; adjusting the pH (Potential of Hydrogen) to 9-11 by using ammonia water; adding diethylenetriamine and reacting under a water bath condition at the temperature of higher than 95 DEG C; drying to obtain amino-modified graphene powder; dispersing the amino-modified graphene powder into a mixed solution of dichloromethane and absolute ethyl alcohol with the volume ratio of not more than 1 to obtain a mixed system in which the mass volume percent of the amino-modified graphene is 0.1%; and adding a dichloromethane solution of an anthraquinone compound containing a sulfonyl chloride radical and reacting at a room temperature. The material has a very good catalytic performance and the anaerobic organism conversion speed of organic matters which are difficult to degrade can be improved; the secondary pollution problem to the environment, caused by the loss of the water-soluble anthraquinone compound, is solved.

Haikun Zhang

Papers

Cr(VI) reduction and Cr(III) immobilization by Acinetobacter sp. HK-1 with the assistance of a novel quinone/graphene oxide composite.

Cake layer morphology in microfiltration of activated sludge wastewater based on fractal analysis

A novel quinone/reduced graphene oxide composite as a solid-phase redox mediator for chemical and biological Acid Yellow 36 reduction

Global transcriptome analysis of Escherichia coli exposed to immobilized anthraquinone-2-sulfonate and azo dye under anaerobic conditions.

Graphene material modified by water-soluble anthraquinone compound and preparation method of graphene material