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Black phosphorus-CdS-La2Ti2O7 ternary composite: Effective noble metal-free photocatalyst for full solar spectrum activated H-2 production
No full textWide-bandgap semiconductor photocatalysts such as La2Ti2O7 (LTO) are stable but can only work under ultraviolet (UV) light, while narrow-bandgap semiconductor photocatalysts such as CdS and black phosphorus (BP) with broad-wavelength range absorption generally have low stability and high electron-hole pairs recombination rate. In this work, ternary heterostructure composing of BP quantum dots (QDs), CdS nanoparticles (NPs) and LTO nanosteps (NSP) is developed for the first time to make full use of their respective advantages, which offers a promising approach to achieving desired stability and solar energy harvesting. As an effective noble metal-free photocatalyst, BP-CdS-LTO composite generates H-2 from Na2S/Na2SO3 aqueous solution with a rate of 0.96 mmol g(-1) h(-1) under solar light irradiation, and 0.26 mmol g(-1) h(-1) in the near-infrared (NIR) range. In this system, BP serves as a NIR photosensitizer; CdS not only contributes to visible light absorption but also bonds with BP to promote the transmission of photogenerated charge carriers; LTO absorbs UV light as well as provides reaction sites for photoinduced electrons. Femtosecond transient absorption spectroscopy is used to elucidate the kinetics of the injection of photogenerated electrons from BP QDs to CdS NPs and finally to LTO. This work provides deep insight into charge transfer between semiconductors with different band alignments, which can open a new avenue for more rationally designing heterostuctured photocatalysts for H-2 production
Fabrication of a highly permeable composite nanofiltration membrane via interfacial polymerization by adding a novel acyl chloride monomer with an anhydride group
No full textIn this study, a novel acyl chloride monomer trimellitic anhydride chloride (TAC) with an anhydride group was blended with trimesoyl chloride (TMC) as organic phase monomers to fabricate high-flux nanofiltration membranes. Due to the reaction activity differences of organic phase monomers (TMC and TAC) with piperazine, the chemical compositions and structures of polyamide active layer could be tailored through varying the TAC content. It was found that the participation of TAC could yield a looser polyamide separation layer on the polysulfone support membrane, along with an increased surface roughness, hydrophilicity, pore size and negative charge density. As a result, the resultant membrane exhibited excellent water-salt separation. When the TAC concentration was increased to 0.04 wt%, the optimized membrane exhibited a high pure water permeability (PWP) of 13.2 Lm(-2)h(-1) bar(-1), up to 2-fold, in comparison with the pristine membrane, whereas the salt rejections of Na2SO4, MgSO4 and NaCl were 97.6%, 92.7%, and 34.0%, respectively. This work provided a novel and facile strategy to develop high-flux NF membrane
Production and structural characterization of a new type of polysaccharide from nitrogen-limited Arthrospira platensis cultivated in outdoor industrial-scale open raceway ponds
No full textBackgroundCarbohydrates are major biomass source in fuel-targeted biorefinery. Arthrospira platensis is the largest commercialized microalgae with good environmental tolerance and high biomass production. However, the traditional target of A. platensis cultivation is the protein, which is the downstream product of carbohydrates. Aiming to provide the alternative non-food carbohydrates source, the feasible manipulation technology on the cultivation is needed, as well as new separation methodology to achieve maximum utilization of overall biomass.ResultsThe present study aimed to demonstrate the feasibility of industrially producing carbohydrate-enriched A. platensis and characterize the structure of the polysaccharide involved. Cultivated in industrial-scale outdoor open raceway ponds under nitrogen limitation, A. platensis accumulated maximally 64.3%DW of carbohydrate. The maximum biomass and carbohydrate productivity reached 27.5gm(-2)day(-1) and 26.2gm(-2)day(-1), respectively. The efficient extraction and purification of the polysaccharides include a high-pressure homogenization-assisted hot water extraction followed by flocculation with a non-toxic flocculant ZTC1+1, with the polysaccharide purity and total recovery reaching 81% and 75%, respectively. The purified polysaccharide was mainly composed of (13)(14)- or (13)(12)--glucan with a molecular weight of 300-700kDa, which differed from the commonly acknowledged glycogen.ConclusionsBy the way of controlled nitrogen limitation, the high carbohydrate production of A. platensis in the industrial scale was achieved. The -glucan from A. platensis could be a potential glucose source for industrial applications. A non-toxic separation method of carbohydrate was applied to maintain the possibility of utilization of residue in high-value field
