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Utilization of visible light and the separation of electron–hole pairs is the forever theme of photocatalysis. In this work, a series of carbon quantum dots decorated bismuth oxychloride (CQDs/BiOCl) were prepared by solvothermal method, and served as photocatalysts for Rhodamine B (RhB) degradation under visible light. CQDs/BiOCl-8 (8 mL CQDs) can remove 97% RhB (20 mg/L) within 40 min, which is 11.3 times higher than pure BiOCl. This can be attributed to the fact that the excitation-independent up-conversion fluorescent characteristics of CQDs enable BiOCl to be excited by visible light. Furthermore, CQDs acted as electron libraries, which enhanced the separation of photoinduced electron–hole pairs in BiOCl. Quenching experiments confirmed that the superoxide (·O2−) and hole (h+) were main reactive oxygen species (ROS) for RhB degradation. This study provides a strategy to design highly efficient photocatalysts for environmental remediation. [ABSTRACT FROM AUTHOR]

Slow and random transfer of pollutants and photo-induced carriers on photocatalysts causes loss of efficiency in photodegradation of contaminants. Enhancing and directing mass transfer of them are considered as two major methods for improving the photodegradation of pollutants over photocatalysts. Here in this work, we focused on the design of a novel photocatalyst which not only accelerated the transfer rate of Cr(VI) and electrons but also provided specific transfer routes for them. By careful characterizations, it is indicated that 2-((2-(2-aminoethylamino)ethylimino)methyl)phenol (AEMP) was covalently attached onto activated carbon (AC), which enhanced Cr(VI) transfer from bulk solution to AC through electrostatic or coordinative interactions. The external mass transfer coefficient (Kf) of Cr(VI) over TiO2/AC-AEMP was estimated as 1.75 × 10−6 m s−1, which was ~ 12.79 and ~ 5.96 times that of TiO2 and TiO2/AC, respectively. Dense and homogeneous heterojunctions between AC and TiO2 were acquired synchronically by forming Ti–O–C linkages, which increased traveling of electrons from TiO2 to AC. Accordingly, Cr(VI) can capture photo-induced electrons on the surface of AC via concrete routes and then be reduced efficiently. The results showed that the photoreduction rate of Cr(VI) on TiO2/AC-AEMP reached to ~ 92.7%, and the overall photocatalytic activity of this well-designed TiO2/AC-AEMP has been enhanced significantly by 5.5 times compared to TiO2/AC. The enhanced photocatalytic activity of TiO2/AC-AEMP was mainly attributed to an improved synergetic process of mass transfer–induced adsorption–photoreduction by forming specific transfer routes for accelerative motion of Cr(VI) and electrons. This work provides a feasible strategy to improve the photoactivity of photocatalysts for the degradation of pollutants by effective mass transfer. [ABSTRACT FROM AUTHOR]

Araneose Ti3+ self-doped TiO2/SiO2 nanowires (RTiO2/SiO2) were prepared and anchored onto a polyethersulfone (PES) membrane. Careful characterizations and measurements indicated a covalent grafting of SiO2 onto reduced TiO2 (RTiO2) through Ti–O–Si linkages, acquiring uniformed RTiO2/SiO2 nanowires of almost complete anatase and benign hydrophilicity. The RTiO2/SiO2-based PES membrane showed a significantly enhanced visible light–driven degradation rate of methylene blue (MB) (90.7%), compared with that on bare PES (11.1%) and PES-RTiO2 (59.6%) membranes. The residual MB in filtered water was less than 5% after reusing three times. The normalized permeate flux of the modified membrane was 0.83, and the transmembrane pressure only increased by 0.4 MPa under irradiation of visible light. The improved performance of the PES-RTiO2/SiO2 was attributed to efficient intercept of MB molecular, light harvesting of visible light, and separation of charge carriers on araneose RTiO2/SiO2 nanowires. [ABSTRACT FROM AUTHOR]

Ultrasonication has drawn an increasing attention as one of cell disruption methods for extracting cellular compounds or controlling algal blooms. However, the effects of biological and physical properties of microalgae on cell disruption were not well understood. In this work, cell disruption of six microalgae, namely, Chlamydomonas reinhardtii, Chlorella pyrenoidosa, Microcystis aeruginosa (three strains: PCC 7806, FACHB 469, and FACHB 1343), and Synechococcus elongatus, was compared mutually based on their characteristics induced by a low-frequency ultrasound (35 kHz, 0.043 W mL). Results showed that the most sensitive strain was C. reinhardtii which has a hydroxyproline-rich-glycoproteins cell wall and a larger cell size (normally 10 μm in diameter). More than 80% of the cells of C. reinhardtii were ruptured after sonication for 5 min. In comparison, C. pyrenoidosa, a cellulose-rich-wall algal species with a medium size of 4-6 μm, and M. aeruginosa FACHB 1343, a peptidoglycan-wall species with a smaller average size of 2.3 μm, were highly resistant to ultrasound. Only 7.5 and 7.7% of cell disruption were achieved for C. pyrenoidosa and M. aeruginosa FACHB 1343, respectively, when they were sonicated for 60 min. Declumping effect was dominant in these strains. This suggested that cellulose-rich-wall algal species might be much more resistant than hydroxyproline-rich glycoproteins, and peptidoglycan-wall species to sonication. It also revealed that the larger cell size was more susceptible to sonication the cell would be. This research provides useful insights into choosing the low-cost microalgae for extraction or controlling specific microalgal blooms in water systems using ultrasound. [ABSTRACT FROM AUTHOR]