Ting Xiong

Highly efficient visible-light-induced photoactivity of Z-scheme Ag2CO3/Ag/WO3 photocatalysts for organic pollutant degradation

Novel and efficient Z-scheme Ag2CO3/Ag/WO3 with excellent visible-light-driven photocatalytic performance was fabricated using a facile deposition and photochemical reduction process. Surface, morphological, and structural properties of the resulting materials were characterized using N2 sorption–desorption and Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-vis and photoluminescence spectroscopy. The photocatalytic performances of the Ag2CO3/Ag/WO3 composites were evaluated by the degradation of rhodamine B (RhB), methyl orange (MO), ciprofloxacin (CIP), and tetracycline hydrochloride (TC) under visible light irradiation. The results demonstrate that the novel Z-scheme Ag2CO3/Ag/WO3 composites exhibit higher photocatalytic activity than pure Ag2CO3 rods and WO3 nanoparticles. The enhanced photocatalytic activity of Ag2CO3/Ag/WO3 can be ascribed to the extended absorption in the visible light region caused by a surface plasmon resonance (SPR) effect, effective separation of photogenerated charges, and the formation of a Z-scheme system. In addition, the photocatalyst exhibits high stability and reusability. This work could offer a new insight into the design and fabrication of advanced materials with Z-scheme structures for photocatalytic applications for organic pollutants removal from wastewater.

Implication of graphene oxide in Cd-contaminated soil: A case study of bacterial communities

The application of graphene oxide (GO) has attracted increasing concerns in the past decade regarding its environmental impacts, except for the impact of GO on a metal-contaminated soil system, due to its special properties. In the present work, the effects of GO on the migration and transformation of heavy metals and soil bacterial communities in Cd-contaminant soil were systematically evaluated. Soil samples were exposed to different doses of GO (0, 1, and 2xa0gxa0kg-1) over 60 days. The Community Bureau of Reference (BCR) sequential extraction procedure was used to reflect the interaction between GO and Cd. Several microbial parameters, including enzyme activities and bacterial community structure, were measured to determine the impacts of GO on polluted soil microbial communities. It was shown that Cd was immobilized by GO throughout the entire exposure period. Interestingly, the structure of the bacterial community changed. The relative abundance of the major bacterial phyla (e.g., Acidobacteria and Actinobacteria) increased, which was possibly attributed to the reduced toxicity of Cd in the presence of GO. However, GO exerted an adverse influence on the relative abundance of some phyla (e.g., WD272 and TM6). The diversity of bacterial communities was slightly restricted. The functional bacteria related to carbon and the nitrogen cycling were also affected, which, consequently, may influence the nutrient cycling in soil.

Visible-light-driven removal of tetracycline antibiotics and reclamation of hydrogen energy from natural water matrices and wastewater by polymeric carbon nitride foam

Water and energy are key sustainability issues that need to be addressed. Photocatalysis represents an attractive means to not only remediate polluted waters, but also harness solar energy. Unfortunately, the employment of photocatalysts remains a practical challenge in terms of high cost, low efficiency, secondary pollution and unexploited water matrices influence. This study investigated the feasibility of photocatalysis to both treat water and produce hydrogen with practical water systems. Polymeric carbon nitride foam (CNF) with large surface area and mesoporous structure was successfully prepared via the bubble-template effect of ammonium chloride decomposition during thermal condensation. The reaction kinetics, mechanisms, and effect of natural water matrices and wastewater on CNF-based photocatalytic removal of tetracycline hydrochloride (TC-HCl) were systematically investigated. Furthermore, the efficiency of clean hydrogen energy from natural water matrices and wastewater was also evaluated. It was found that the photocatalytic performance of CNF for TC-HCl removal was principally affected by calcination temperature in the presence of NH4Cl. The degradation rates of CNF-4 (calcined at 550u202f°C) were approximately 1.84, 2.49 and 7.47 times than that of the CNF-2 (calcined at 600u202f°C), CNF-1 (calcined at 500u202f°C) and GCN (without NH4Cl), respectively. Results indicate that the improved photocatalytic performance was predominantly ascribed to the large specific surface area, increased availability of exposed active sites, and enhanced transport and separation efficiency of the photogenerated carrier. Based on electron spin resonance, chemical trapping experiment and density functional theory calculation, photoinduced oxidizing species (·O2- and holes) initially attacked the C-N-C fragment of TC molecules, which were finally mineralized to CO2, water and inorganic matters. Under the synergistic influence of water constituents (including acidity and alkalinity, ion species and dissolved organic substances), various water matrices greatly affected the degradation rate of TC-HCl, with the highest removal efficiency of 78.9% in natural seawater, followed by reservoir water (75.0%), tap water (62.3%), deionized water (49.8%), reverse osmosis concentrate (32.7%) and pharmaceutical wastewater (18.9%). Interestingly, low amounts of the emerging microplastics slightly improved TC-HCl removal, whereas high amounts (1.428u202f×u202f107u202fP/cm3) restricted removal due to light absorption and the intrinsic adsorption interaction. Moreover, the photocatalysts were able over repeated usage. Notably, the hydrogen yields rates of polymeric carbon nitride foam were 352.2, 299.8, 184.9 and 94.3u202fμmol/g/h in natural seawater, pharmaceutical wastewater, water from reservoir and tap water, respectively. This study proves the potential of novel nonmetal porous photocatalyst to simultaneously treat wastewater while converting solar energy into clean hydrogen energy.

Insight on the plasmonic Z-scheme mechanism underlying the highly efficient photocatalytic activity of silver molybdate/silver vanadate composite in rhodamine B degradation

A facile deposition-precipitation method was applied to synthesize novel plasmonic Z-scheme Ag2MoO4/Ag3VO4 photocatalysts with different molar ratios of Ag2MoO4. The morphological, structural, and spectroscopic properties of the as-obtained samples were characterized through X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectral analysis. The photocatalytic performance of the synthesized photocatalysts in rhodamine B (RhB) degradation under visible light irradiation was evaluated. The 5% Ag2MoO4/Ag3VO4 composite displayed the highest photocatalytic activity among all samples and the RhB removal rate of 93% within 6u202fmin. The RhB removal rate of 5% Ag2MoO4/Ag3VO4 composite was higher than that of precursor Ag2MoO4 and Ag3VO4 compounds. The formation of Ag nanoparticles (Ag NPs) on the surface of Ag2MoO4/Ag3VO4 during photocatalysis resulted in the transformation of the Ag2MoO4/Ag3VO4 heterojunction to the Ag2MoO4/Ag/Ag3VO4 Z-scheme system, thus enhancing photocatalytic activity. Z-scheme Ag2MoO4/Ag/Ag3VO4 composites could efficiently facilitate charge transfer, promote redox ability, and restrain Ag3VO4 photocorrosion. The produced active species O2-, h+, and OH are vital for RhB degradation. The present work could benefit the development of advanced visible-light photocatalytic materials with future applications in environmental remediation.

Modified stannous sulfide nanoparticles with metal-organic framework: Toward efficient and enhanced photocatalytic reduction of chromium (VI) under visible light

Novel metal-organic framework/stannous sulfide (MIL-53(Fe)/SnS) nanocomposite photocatalysts were successfully synthesized by a one-step deposition process. The structure, composition and optical properties of the MIL-53(Fe)/SnS composite were systematically characterized by the X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform-infrared spectroscopy, UV-vis diffuse reflection spectroscopy and photoluminescence analysis. The photocatalytic performance of MIL-53(Fe)/SnS composite has been evaluated in the reduction of chromium (VI) under visible-light irradiation. Compared with pure MIL-53(Fe) and SnS, the MIL-53(Fe)/SnS composite exhibited enhanced photoreduction capability of chromium (VI) due to the strengthened absorption in the visible region, higher electron-hole separation rate and larger specific area. The MIL-53(Fe)/SnS composite with MIL-53(Fe) adding of 15u202fmg displayed optimal chromium (VI) reduction rate of 0.01878u202fmin-1, which was about 7.5 and 5.2 times than pure MIL-53(Fe) and SnS, respectively. The active species superoxide radical (O2-), electron(e-) and hole(h+) are essential toward chromium (VI) reduction. Lastly, a possible photocatalytic mechanism is proposed.

Near-infrared-driven Cr(VI) reduction in aqueous solution based on a MoS2/Sb2S3 photocatalyst

Exploiting photocatalysts with a full spectrum response undoubtedly holds great potential. Here, a novel MoS2/Sb2S3 composite with a wide-range photoresponse was fabricated through a facile hydrothermal method. The as-obtained photocatalyst was characterized via a variety of techniques used for analyzing morphology, structure, and physical–chemical and photoelectrochemical properties. It was indicated that the MoS2/Sb2S3 hybrid possessed fast electron transport and improved light absorption. Additionally, the composite presents remarkable photoelectric conversion efficiency and optimal MoS2/Sb2S3 could remove Cr(VI) with efficiencies of 84%, 99% and 72% when exposed to ultraviolet, visible and near-infrared (NIR) light, which are 16, 50 and 25 times greater than those of Sb2S3, respectively. The enhanced NIR photocatalytic efficiency may be explained by the enhanced NIR light absorption, favorable charge separation and, in particular, the sulfur vacancies in MoS2.

Immobilization of heavy metals in two contaminated soils using a modified magnesium silicate stabilizer

AbstractHeavy metal contamination is a severe environmental issue over the world. A lot of work has been done to develop effective stabilizers. In the present work, hydrothermal carbon-modified magnesium silicate (MS-C) was synthesized and used for the remediation of two heavy metal-polluted soils with different physicochemical properties. Soil samples were exposed to different doses of MS-C over 60xa0days (1, 3, and 5xa0wt%). The toxicity characteristic leaching procedure (TCLP) and the community bureau of reference sequential extraction procedure (BCR) were used to evaluate the remediation efficiency. The bioavailability of heavy metals in both soils was reduced by 20–86.7%, and the toxicity of heavy metals was reduced by 26.6–73.2% after MS-C added. Meanwhile, soil pH and water soluble organic carbon (WSOC) were increased. In addition, soil microbial biomass was increased, which indicated the improvement of soil condition. The immobilization of heavy metals was mainly caused by electrostatic attraction and cation exchange between MS-C and heavy metals. The significantly negative correlation between extractable heavy metals and pH/WSOC indicated the positive role of pH/WSOC in metal stabilization. Thus, this new stabilizer holds great application potentials for both single and multi-metal-contaminated soil remediation.n ᅟGraphical abstract