Tian Gao,Ping Fu,Wan-Long Li,Wan-Ting Lin,Yuan-Hui Yu,Xiao-Jun Huang,Zhi-Kang Xu,Ling-Shu Wan
Nanofiltration (NF) membranes with superior permeability and selectivity are highly desirable for the applications. The development of non-polyamide loose NF membranes with high permeability and dye/salt selectivity has aroused great attention in recent years. In this work, 2-hydroxy-1,4-naphthoquinone, a natural compound commonly existed in plants, was chosen to prepare loose NF membranes via the co -deposition with polyethyleneimine (PEI). By optimizing the deposition conditions, we successfully fabricated amine-quinone network coatings on the surface of polyacrylonitrile (PAN) ultrafiltration membranes, and further cross-linked the coatings with glutaraldehyde to improve the compactness and stability. For this kind of loose NF membrane, the rejections to dyes with a molecular weight larger than 600 Da reach 98 %, and the water permeance keeps above 10 L·m −2 ·h −1 ·bar −1 . In contrast, the rejections to inorganic salts (NaCl, Na 2 SO 4 , MgCl 2 , and MgSO 4 ) are only about 10 %, and the selectivity of the dye molecule alcian blue against NaCl can reach 430. These results prove that this novel composite membrane can realize effective separation for dyes with different molecular weights and desalination for dye solutions. The present work will open up an avenue for designing loose NF membranes with novel separation layers.
Yi Sun,Junfeng Su,Amjad Ali,Tinglin Huang,Shuai Zhang,Yitian Min
The coexistence of multiple pollutants and lack of carbon sources are challenges for the biological treatment of wastewater. To achieve simultaneous removal of nitrate (NO 3 − -N) and cadmium (Cd 2+ ) at low carbon to nitrogen (C/N) ratios, 2-hydroxy-1,4-naphthoquinone (HNQ) was selected from three redox mediators as an accelerator for denitrification of heterotrophic strain Pseudomonas stutzeri sp. GF2 and autotrophic strain Zoogloea sp. FY6. Then, halloysite nanotubes immobilized with 2-hydroxy-1,4-naphthoquinone (HNTs-HNQ) were prepared and a bioreactor was constructed with immobilized redox mediator granules (IRMG) as the carrier, which was immobilized with HNTs-HNQ and inoculated with the two strains. The immobilized HNQ and the inoculated strains jointly improved the removal ability of NO 3 − -N and Cd 2+ and the removal efficiency of NO 3 − -N (25.0 mg L −1 ) and Cd 2+ (5.0 mg L −1 ) were 92.81% and 93.94% at C/N = 1.5 and hydraulic retention time (HRT) = 4 h. The Cd 2+ was removed by adsorption of iron oxides (FeO(OH) and Fe 3 O 4 ) and IRMG. The electron transport system activity (ETSA) of bacteria was improved and the composition of dissolved organic matter in the effluent was not affected by HNQ. The HNQ promoted the production of FeO(OH) and up-regulated the proportion of Zoogloea (54.75% in the microbial community), indicating that Zoogloea sp. FY6 was dominant in the microbial community . In addition, HNQ influenced the metabolic pathways and improved the relative abundance of some genes involved in nitrogen metabolism and the iron redox cycle.
Yang Li,Cai Tianming,Ding Dahu,Cai Tianjin,Jiang Canlan,Li Hua,Yang Qian,Chen Liwei
2-hydroxy-1,4 naphthoquinone (lawsone) is widely used and induces environmental pollutions during its production and application. In the present study, a lawsone-degrading bacterium strain, LH-3 was successfully isolated from the activated sludge. Based on the 16S rRNA gene analysis, the strain LH-3 phylogenetically belonged to the Pseudomonas taiwanensis . It could degrade 200 mg L −1 lawsone completely in 9 h with an inoculum quantity of 1% (v/v). The effects of environmental conditions on the degradation process and the degradation pathway were systematically investigated. LH-3 could maintain its high degradation efficiency under high salt condition. The identified intermediates of salicylic acid, 2-hydroxy-4-oxo-chroman-2-carboxylic acid, and catechol elucidated the potential degradation pathway. Furthermore, the immobilized LH-3 strain cells prepared with alginate gel and biochar performed excellent stability in nine successive degradation runs. It could sucessfully survive in laboratory scale sequencing batch reactor and become to be the dominant species. This study clearly revealed that LH-3 could serve as an attractive candidate for the microbial remediation of lawsone-containing wastewater.
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