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Graphite carbon nitride (g-C3N4) is a promising photocatalyst for its high catalytic activity, low-cost and high-biosafety characteristics. Due to the complexity of underwater photochemical reaction conditions and the disadvantages of g-C3N4 itself such as low specific surface area, easy recombination of photogenerated electron–hole pairs and insufficient light absorption capacity, the application of g-C3N4 in the field of water purification is limited. For improving underwater photocatalytic performance of g-C3N4, a g-C3N4/carbon nanotubes (CNT-CN) composite photocatalyst with high specific surface area and enhanced light absorption capacity were prepared by in situ solvothermal method. Its photodegradation efficiency at different underwater transmission light was further studied. The results show that CNT has good compatibility with g-C3N4. g-C3N4 can grow in situ on the surface of CNT and form a stable composite structure. Moreover, its degradation efficiency under long-wavelength irradiation is improved significantly. The degradation rate of CNT-CN at 550-700 nm was about 3 times than that of g-C3N4. Furthermore, CNT-CN can maintain higher photocatalytic activity under water. At 40 cm depth where light intensity and ultraviolet spectra were attenuated 63.8% and 80.1%, respectively, the degradation rate of CNT-CN3 can still reach 3.49 times than that of g-C3N4. Based on this study, the introduction of CNT effectively promotes the electron–hole separation efficiency of g-C3N4, widens its spectral response range, and thus improves its underwater degradation efficiency. [ABSTRACT FROM AUTHOR]

A series of boron carbon nitride–pyromellitic dianhydride (BCNPA) composites were successfully synthesized for the first time, where BCNPA3 exhibited the best adsorption and photodegradation performances for tetracycline (TC) under visible-light irradiation. 1H NMR characterization confirmed the fact that BCNPA3 was formed via the dehydration reaction between the OH groups in BCN and COOH groups in PA. Elemental N in BCNPA3 could capture protons and increase the pH of the TC solution from 3.73 to 6.80; consequently, TC changed from the positive state (pH 3.73) to the neutral state (pH 6.80). Subsequently, the adsorption capacity of BCNPA3 for TC increased from 66.24 mg g−1 (at pH 3.73) to 74.66 mg g−1 (at pH 6.80). This may be attributed to the fact that these captured protons can work as adsorption sites, too. Furthermore, the photodegradation efficiency of BCNPA3 for TC at pH 6.80 under visible-light irradiation was also higher than that at pH 3.73 (95% vs. 87%), because TC at pH 6.80 is less stable than that at pH 3.73. More interestingly, Cr(VI) could only be photoreduced into Cr(III) by BCNPA3 under visible-light irradiation when it coexisted with TC. This could be attributed to the fact that the photodegradation of TC increased the separation efficiency of the photoinduced electron and hole; consequently, the photoinduced electrons had sufficient time to reduce Cr(VI). Photoinduced ˙O2− and holes had the main contribution toward TC photodegradation by BCNPA3, while photoinduced electrons were responsible for Cr(VI) photoreduction. The adsorption and photodegradation performances of BCNPA3 for TC and Cr(VI) could be easily recovered under visible-light irradiation. [ABSTRACT FROM AUTHOR]

Herein, we present the preparation of nano-TiO2-silicone resin composite films by double liquid phase spray deposition. The films exhibit better adhesion stability and photocatalytic activity under a hydrodynamic erosion condition than conventional nano-TiO2 composite films. The TiO2 layer morphology and effective TiO2 coverage ratio (CR) were affected by the initial curing time (ICT) of the silicone resin, e.g., the increase in an ICT from 10 to 40 min resulted in a CR change from 79.1 to 98.7%. The surface morphology evolution of composite films was studied under a hydrodynamic erosion period of 4 weeks. Obtained results allowed the 4-week evolution to be divided into four stages (pitting, crack pregnant, banded stripping, and surface stripping periods), additionally revealed that the CR of all samples was remained above 65%. The photocatalytic activity of composite films before and after 4-week hydrodynamic erosion was evaluated by rhodamine B degradation experiments. The 4-week erosion only led to the decrease of the photodegradation efficiencies by less than 40% in all cases. Thus, the fabricated TiO2-silicone composite films demonstrated excellent durability and photocatalytic activity under the conditions of long-term hydrodynamic erosion, allowing one to conclude that this work paves the way to the fabrication of next-generation photocatalytic materials for industrial applications. [ABSTRACT FROM AUTHOR]

In order to explore the influence of various carbon introduction on the morphology and photodegradation performance of C/g-C 3 N 4 composites, three kinds of different carbon materials: carbon nanotubes (CNT), graphene (GN) and carbon fibers (CF) were introduced to modify g-C 3 N 4 , and the morphologies, light absorption capacities and the underwater purifications of the composite photocatalysts were investigated. Results showed that the composites synthesized with different carbon substrates shows great differences in growth morphology. In addition, the introduction of various carbon sources also has a great impact on the physical and chemical properties of the composites. Compared with GN/g-C 3 N 4 and CF/g-C 3 N 4 , CNT/g-C 3 N 4 shows strong light absorption ability, especially in long-wavelength region (570–660 nm). To further study the difference of degradation ability of the composites in the underwater environment, the purification performance of modified g-C 3 N 4 at different water depths were carried out. The results show that under 40 cm of water, where the light intensity and ultra violet spectral are seriously attenuated, the purification efficiency of CNT/g-C 3 N 4 at 40 cm is 3.35 times than that of g-C 3 N 4. This work provides insight in the design of highly efficient metal-free photocatalysts for the environmental remediation. [Display omitted] • The effects of morphology difference on the degradation performance of C/g-C 3 N 4 composite photocatalysts were discussed. • The degradation efficiencies of C/g-C 3 N 4 under long wavelength irradiation were significantly enhanced. • The purification performances of C/g-C 3 N 4 over methyl orange at actual underwater transmission light were tested. • The experimental results are significance for the practical application of photocatalytic degradation. [ABSTRACT FROM AUTHOR]

A series of boron nitride-pyromellitic dianhydride composites have been successfully synthesized by calcinating the mixtures of boron nitride (BN) and pyromellitic dianhydride (PA) at 350 °C, in which the composite (BNPA2) has the largest adsorption quantity (65.1 mg/g) for rhodamine B (RhB) and the best photo-removal efficiency for RhB under visible light irradiation. 1H NMR characterizations for BN, PA and BNPA2 suggest that this composite is formed via the reaction between the OH groups in BN and PA. BNPA2 can also adsorb neutral red (NR), methyl orange (MO), tetracycline (TC) and atrazine (AT). NR and MO can be photo-removed by BNPA2 under visible light irradiation. Colorless TC and AT can also be degraded by BNPA2 under visible light irradiation, suggesting that BNPA2 is visible light responsible photocatalyst. BNPA2 has the highest photo-removal efficiency for the cationic RhB and NR, followed by the anionic MO. This is from that BNPA2 has negative surface. When anionic MO mixes with cationic RhB (or NR) together, BNPA2 prefers to remove cationic RhB (or NR) from the mixture solution under visible light irradiation and the removal efficiency of anionic MO by BNPA2 is also increased. Thus, electrostatic interactions between dyes and BNPA2 as well as between dyes play significant role in the removal process. •O2− makes a main contribution for this photo-removal of these aromatic pollutants (dyes, TC and AT) by BNPA2 under visible light irradiation. Furthermore, the removal performance of BNPA2 for RhB, TC and AT can be effectively regenerated by visible light irradiation. • Boron Nitride-Pyromellitic Dianhydride composite (BNPA2) is first time synthesized with BN and PA as precursors. • BNPA2 can remove organic pollutants (dyes and atrazine) via adsorption and photodegradation. • BNPA2 is visible light responsive photocatalyst and the photocatalytic performance of BN is from sensitization. • Electrostatic attraction between dyes and BNPA2 play significant role during the removal process of dyes. • Visible light irradiation can regenerate the removal performance of BNPA2 for dyes. [ABSTRACT FROM AUTHOR]