Photocatalytic Purification Research Articles

PEG assisted P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst with enhanced elimination of emerging organic pollutants in salinity condition under solar light illumination

In this study, the effect of salinity on degradation of model environmental pollutants (organic dyes and E. coli) was investigated using polyethylene glycol (PEG) assisted P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst. The photocatalyst was firstly synthesized with structure modifier PEG to determine the optimum molecular weight by sol-gel method, and was characterized by XRD, UV–Vis, PL, SEM, TEM, EDS, and photocurrent experiment. The PEG300 modified P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst was found to be the optimal molecular weight which exhibited small crystalline size, narrow band gap, better absorption ability, smaller particles size, large photocurrent density, low recombination rate and higher photocatalytic activity among other PEG modified photocatalyst. The PEG300-P/Ag/Ag2O/Ag3PO4/TiO2 photocatalytic degradation of emerging organic pollutants such as rhodamine B, methyl orange, and methylene blue was significantly higher at aqueous NaCl (2.6 and 3.2 wt%) and artificial salinity (25 and 35‰) compared to freshwater under simulated solar light illumination. Furthermore, the elimination of organic dyes under different environmental factors such as initial pH, light intensity, reaction temperature showed substantial degradation in real environmental conditions at salinity. Moreover, PEG300-P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst demonstrated high practicability on complete inactivation of E. coli, simultaneous degradation of organic dyes, and high stability in seawater. Superoxide anion (O2−) radicals was found to be the dominant reactive species, and subsequent formation of Cl and free chlorine oxidative agents further improved the photocatalytic purification process. The PEG300-P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst showed great potential in treating environmental organic pollutants at salinity condition under solar light illumination.

Sustainable scientific advancements modified Ag2O-ZnO thin films characterization and application of photocatalytic purification of carcinogenic dye in deionizer water and contaminated sea water solutions and synthetic, natural based dye-sensitized solar cells

The manuscript studied the preparation of ZnO as well as Ag2O-ZnO thin films deposited on glass substrates by spray pyrolysis approach at 500 °C. The photocatalytic activity of Ag2O-ZnO nanocomposite material was studied via the Photodegradation reaction of Rhodamine B (Rh B) dye under UV-light irradiation in Deionizer water which shows high activity as compared by Contamination of sea water. The Zinc was Zincacetylacetonate (ZnC10H14O5) at the atomic concentration and then dissolved in the ethanol and Ag NO3 (0.1 M) dissolved in ethanol. The effect of silver Oxide-Zinc Oxide Nanocomposite material on the structural, surface morphological, electrical and optical properties of Ag2O-ZnO thin films were studied. HR-SEM and HR-TEM image shows exposed that the surface morphology of the films nanoflower shaped structure. The presence of Silver, Zinc and Oxygen are confirmed the presence of peaks, using EDS analysis. X-ray diffraction (XRD) patterns accepted the successful growth of high quality thin films which is polycrystalline nature. The PL analysis shows in Ag2O-ZnO is certified to the low recombination of electron-hole pairs by transfer of electrons and holes between ZnO and UV–Vis DRS analysis. The photocatalytic activity of Ag2O-ZnO nanocomposite material was studied from Photodegradation study of Rhodamine B (Rh B) dye under UV-light irradiation of Deionizer water was high activity that Contamination of sea water. As a reaction of this the material was found to be stable and reusable, which extends to a high antibacterial activity and the electrochemical study from synthetic based and Natural based.DSSCS analysis showed increased current is short circuit by Ag2O-ZnO thin film nanocomposite material was industrial applications.

Plastic optical fibres applied on the photocatalytic degradation of phenol with Ag2MoO4 and ß-Ag2MoO4/Ag3PO4 under visible light

ABSTRACT In this study, plastic optical fibre (POF) was considered as a light-transmitting medium and substrate for use in a photocatalytic environmental purification system, using Ag2MoO4 and β-Ag2MoO4/Ag3PO4 as photocatalysts. Pure Ag2MoO4 and a β-Ag2MoO4/Ag3PO4 composite were synthesized using a facile precipitation method. The composition, structures and optical properties of as-prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), UV/Vis diffuse reflectance spectroscopy (UV/Vis DRS), BET surface area and TGA/DTG. The catalysts were immobilized on POF and on the glass reactor surface and their efficiency in the phenol degradation was evaluated in a batch reactor under visible light. The use of POF offers advantages such as ease of handling and good adherence characteristics to support Ag2MoO4. The photoactivity follows the order β-Ag2MoO4/Ag3PO4 ≅ Ag2MoO4 > TiO2 P25, for photocatalysts immobilized on the glass reactor surface or in aqueous suspension. The immobilization of Ag2MoO4 on POF revealed that thinner Ag2MoO4 coatings achieved faster pollutant removal rates from solution, and the optimal catalyst deposition is 0.64 mg/cm2, causing maximum the light penetration and electron–hole generation close to the solid–liquid interface.

DyVO4/boron-doped g-C3N4 composite photocatalytic materials with enhanced visible-light purification properties

Novel DyVO4/boron-doped graphitic carbon nitride (DyVO4/g-C3N4B) composite photocatalytic materials were successfully fabricated by a facile heating method, and their crystal structure, morphology, light absorption properties were analyzed by various technologies. With the increases of DyVO4 content, the visible-light photocatalytic properties of DyVO4/g-C3N4B catalysts first increase and then decrease, and the 5.7% DyVO4/g-C3N4B catalyst with a proper DyVO4 content-shows the highest photocatalytic purification performance. Its NO conversion ratio is >1.6 time higher than that of DyVO4, g-C3N4 and g-C3N4B. And its Cr(VI) reduction ratio is 2.6, 2.1 and 1.8 times higher than that of DyVO4, g-C3N4 and g-C3N4B, respectively. The obviously enhanced visible-light purification properties of 5.7% DyVO4/g-C3N4B are mainly ascribed to the fact that proper DyVO4 modified g-C3N4B promotes the efficient separation of photo-generated electron-hole pairs by the band alignment between g-C3N4B and DyVO4, as well as contributes to the narrowest band gap and the best photo-response in 420–700 nm region. Moreover, 5.7% DyVO4/g-C3N4B also shows enough catalytic stability as evidenced by the four recycling experiments. This work provides some useful insights to design and synthesize a series of novel and highly efficient g-C3N4-based composite photocatalytic materials for environmental purification applications.

A procession on photocatalyst for solar fuel production and waste treatment

Conversion of solar energy into hydrogen is one the most promising renewable energy technology which is stimulated after detection of increasing global energy consumption and climate changes by the emission of fossil fuel. Photocatalytic water splitting use semiconductor materials having the electronic structure suitable for charge (electron and hole) injection for water decomposition to produce H2 and O2. Many inorganic materials are now using as active photocatalyst for water reduction since artificial photocatalytic water splitting has discovered for the very first time in 1971. Beyond, metal oxides, sulfides, and nitrides are the common photocatalytic semiconductor. To material science, research in this compass has brought huge grip that commits to the development of visible light active substances progressively. In this review along with the introduction of solar fuel, photocatalyst and photocatalytic water splitting, up-and-coming photocatalysts for solar-to-fuel conversion and photocatalytic purification of environment are discussed. We address TiO2 based, carbon based and two dimensional materials based photocatalyst for solar fuel production and waste treatment.

Synthesis of polyoxometalates supported on HZSM-5 for the photocatalytic purification of crude terephthalic acid under mild conditions

Phosphomolybdic (PMo) and vanadium-containing phosphomolybdic (PV2Mo) acids were synthesized and supported on HZSM-5 zeolite via a wet impregnation technique and used as photocatalysts for the purification of terephthalic acid (TA) via an economic process. Nowadays, purified TA can be obtained from crude TA due to their great commercial importance by separating 4-carboxybenzaldehyde (4-CBA), which represents high environmental toxicity and negatively affects the applications of TA. For these reasons, conversion of 4-CBA to TA is highly desirable for both enhancing the efficiency of purified TA production and environmental reasons. The synthesized catalysts were characterized by XRD, FTIR, Raman spectroscopy, BET, SEM, and TEM. The purification process was carried out by under different parameters as VUV irradiation, persulfate (PS), time, and different types of catalysts (PMo or PV2Mo)/HZSM-5. This kind of combination showed complete removal of the 4-CBA with a high yield of PTA in 2 h. The high efficiency attributed to the acidity of the polyoxometalates/HZSM-5, which increase the selectivity to oxidize 4-CBA at room temperature and much shorter reaction time compared to other common methods.

Engineering of reduced graphene oxide on nanosheet–g-C3N4/perylene imide heterojunction for enhanced photocatalytic redox performance

g-C3N4-based photocatalysts are recognized as promising candidates for photocatalytic purification of air and solar energy conversions; but their practical application is still limited by the sluggish charge transfer dynamic. Herein, a Z-scheme ternary heterojunction (nanosheet–g-C3N4 [NCN]/perylene imide [PI]/reduced graphene oxide [rGO], NCN/PI/rGO) was successfully constructed. For experimental comparison, NCN/rGO/PI was concurrently synthesized through different reaction sequences. In these ternary heterojunction systems, the introduction order of rGO affects the morphology structure and the interaction between phases and results in two diverse electron transfer modes which determine the different photocatalytic redox performances. The as-obtained NCN/PI/rGO Z-scheme heterostructure exhibited superior photocatalytic activity towards the photocatalytic removal of NO and generation of H2O2 under visible light irradiation. Such photocatalytic activity was about 1.58 and 1.23 times higher than those of NCN and NCN/PI, respectively, in NO removal. Such enhanced photocatalytic properties can be ascribed to the two-step electron transfer process involving the CB electrons in PI combined with the VB holes of NCN via the Z-scheme pathway (process I, PI→NCN) because PI was grown in situ on the NCN through thermal condensation polymerisation. This process enabled intimate contact between NCN and PI and a short charge-transfer distance. The residual electrons in the CB of NCN then flowed into the rGO (process II, PI→NCN→rGO). Thus, the simultaneous occurrence of two electron transfers processes I and II help improve the photocatalytic activity. Constructing NCN/PI/rGO Z-scheme heterostructures is anticipated to be an effective strategy for developing high-performance photocatalysts that facilitate the utilisation of solar energy.

Simultaneous removal of heavy metal ions and organic pollutant by BiOBr/Ti3C2 nanocomposite

Photocatalytic purification of wastewater is a very attractive method to remove pollutants. However, it has not been widely used in the industry due to limitations in photocatalytic performance and the complexity and diversity of contaminants. It is of great significance to simultaneous treatment of multiple pollutants. In this work, we designed and successfully synthesized a BiOBr/Ti3C2 nanocomposite by electrostatically driven self-assembly method. The degradation performance of BiOBr/Ti3C2 nanocomposite was evaluated by the degradation efficiency of rhodamine B (RhB), 2,4-Dinitrophenol (2,4-DNP) and Cr(VI). By coupling the Ti3C2 with BiOBr, the degradation activity of BiOBr was greatly improved. The degradation apparent rate constant of rhodamine B(RhB), 2,4-Dinitrophenol (2,4-DNP) and Cr(VI) with BiOBr/Ti3C2 were 1.2, 1.3, 6 times that of BiOBr, respectively. The photocatalytic performance of BiOBr/Ti3C2 toward RhB still maintained 85.6% after 5 cycles. The use of BiOBr/Ti3C2 deal with the multicomponent pollutants has also been achieved. The results showed that RhB and Cr(VI) can be completely removed with 80 min by BiOBr/Ti3C2. The enhanced catalytic performance mainly arises from the formation of Schottky junction at BiOBr-Ti3C2 interface, which greatly promoted the separation of carriers. This work provides a new insight into the design of Ti3C2 based Schottky photocatalysts.

Treatment of Aquaculture Wastewater through Chitin/ZnO Composite Photocatalyst

This paper proposed a newly explored composite photocatalyst, Chitin/ZnO, prepared via the sol-gel method for exploring its photocatalytic activity in the simulated aquaculture wastewater under UV irradiation. The study mainly involves the application of Chitin/ZnO from three aspects: the structure, the principle and the degradation efficiency. The effects of purification operation factors including mass ratio rate, dosage, calcination temperature, initial NH4+–N concentration and illumination conditions on the NH4+–N removal effectiveness were investigated. Optimum conditions were explored through orthogonal experiments, which revealed that 88.73% NH4+–N removal from 60 mg/L synthetic wastewater was achieved by direct illumination for 120 min. Additionally, Chitin/ZnO photocatalysts (mass ratio of 2:3) at a calcination temperature of 500 °C were favorable for Chitin loaded over a ZnO lattice. The obtained nanoparticles of Chitin/ZnO were characterized using SEM and X-ray diffraction. The purpose of this paper is to grope for an economical and easy method of Chitin/ZnO powder preparation and to provide a practical approach for future research on the photocatalytic purification of aquaculture wastewater.

Photocatalytic purification of water on TiO2 photocatalysts produced with application of plant extracts

Photocatalytic purification of water on TiO2 photocatalysts produced with application of plant extracts

In situconstruction of layered graphene-based nanofiltration membranes with interlayer photocatalytic purification function and their application for water treatment

Graphene-based filtration membranes with interlayer photocatalysis properties are constructed through anin situphoto-reduction strategy, showing their potential applications in water treatments.

USE OF TITANIUM OXIDE FOR DISINFECTION OF DANGEROUS CHEMICAL SUBSTANCES BY PHOTOCATALIS

TiO 2 coatings have high adhesion to the surface. Any surface applied with TiO 2 is easy to position for irradiation with light, in contrast to powders that need to be somehow placed and fixed on the surface. It has been proved that practically any organic compounds can be oxidized (mineralized) on the TiO 2 surface. In practice, any photocatalytic air purifier includes a porous carrier with TiO 2 deposited, which is irradiated with ultraviolet rays and through which the air is blown. Photocatalysis is suitable for household use, as it can occur at room temperature. For example, the thermocatalytic way of destroying harmful substances requires preheating of air to temperatures above 200 ° C. Photocatalysis destroys substances that penetrate even through activated carbon-based filters. Peculiarities of for mation of oxide coatings by plasma-electrolytic oxidation of titanium alloys are considered. Therefore, it is proposed to equip the design of collective defense systems on armored vehicles and stationary objects with the additional installation in a filter-sink of a network with a deposited layer of catalytic material that will neutralize various types of hazardous chemicals by photocatalytic purification of air by titanium oxides.

Fabrication of WO3 nanorods on reduced graphene oxide sheets with augmented visible light photocatalytic activity for efficient mineralization of dye

Direct evidence for greatly enhanced photocatalytic performance was observed in the photocatalytic purification of organic pollutant by applying tungsten trioxide (WO3) nanorods on reduced graphene oxide (RGO) sheets. We reported a viable strategy to fabricate WO3/RGO composites via an in-situ solvothermal method. In addition, the photocatalytic performance of as-prepared WO3 and WO3/RGO composites were evaluated by monitoring the degradation of methylthionine chloride (MB)-contained wastewater under visible light irradiation, where more than 94.1% photocatalytic degradation efficiency is achieved within 150 min by WG3 under visible light irradiation, being 71.8% higher than that of pure WO3. The enhanced photocatalytic activity of WO3/RGO composite is mainly attributed to the fact that the formation of well-defined WO3-RGO interfaces can efficiently restrain the recombination of photogenerated charges. Additionally, the mineralization degree of MB was analyzed by TOC. This work manufactures a promising application of current water-pollution issues owing to its great photocatalytic efficiency and high recyclability.

High Surface Area SnO2 -Ta2 O5 Composite for Visible Light-driven Photocatalytic Degradation of an Organic Dye.

SnO2 -Ta2 O5 nanocomposite was synthesized by a facile coprecipitation method and further calcined to obtain crystalline powder. Phase formation, morphology, bandgap and photocatalytic properties were analyzed using powder X-ray diffraction, scanning electron microscopy, UV-Vis diffused reflectance spectroscopy, BET surface area and Raman spectroscopy, respectively. Effect of calcination temperature on the crystallinity of the composite was studied. The as-prepared samples of SnO2 , Ta2 O5 and SnO2 -10wt%Ta2 O5 composite as well as the calcined composite sample were tested for photocatalytic activity for methylene blue dye degradation under visible light. Photocatalytic studies reveal that the as-prepared SnO2 -10wt%Ta2 O5 composite showed the best photocatalytic activity for the degradation of methylene blue (MB) by harvesting visible-light radiation efficiently. Further mineralization of methylene blue, estimated by COD analysis, is found to have degraded with an efficiency of 91.6%. The study demonstrates that heterostructure of SnO2 -Ta2 O5 nanocomposite could be applied in photocatalytic purification of organic pollutants.

Synthesis and properties of a CO oxidation catalyst based on plasma-chemical silicon carbide, titanium dioxide, and palladium

A catalyst based on plasma-chemical β-SiC and TiO2 with a palladium content of 10 wt % has been synthesized. The dependence of the rate of the CO oxidation reaction at room temperature and low CO concentrations (less than 100 mg/m3) on the β-SiC content has been studied. It has been found that with a β-SiC content of 8 to 10 wt %, the catalyst has a maximum reaction rate, which is three times that on a catalyst based on pure TiO2 including palladium clusters. The catalysts are promising for use in catalytic and photocatalytic air purification systems.

A Novel Photocatalytic Purification System for Fish Culture

The accumulation of nitrogen compounds represents a pivotal problem in the management of fish culture. Several methods were investigated in the last decades for treatment of waste waters, and the use of photocatalytic materials has received increasing attention. The photocatalytic degradation (PCD) process with titanium dioxide (TiO2) represents the most promising single-step method to promote the removal of nitrogen compounds from water. The present study compares for the first time the effects on fish culture of a classical mechanical, biological, and ultraviolet purification system to a TiO2-PCD one, with particular emphasis on water chemistry and on physiological responses in zebrafish. Fish were exposed for 14 days to the two different purification systems and samplings were performed 7 and 14 days after the experiment beginning. The photocatalytic system showed excellent efficiency in removing nitrogen compounds from water with no significant adverse effects on fish. Physiological analysis on fish samples included histological analysis of gills and gut, TUNEL assay of the gills, and real-time polymerase chain reaction (liver) of genes involved in stress response and growth. No significant biological alterations were detectable on the cultured fish.

Constructing effective photocatalytic purification system with P-introduced g-C3N4 for elimination of UO22+

Due to the inherent defects of precursor molecular structure, the limited effect of structure in the formed g-C3N4 will weaken the extension of delocalization of π electrons between the adjacent tri-s-triazine or heptazine units of g-C3N4, which thus leads to poor visible-light absorption, low utilization efficiency of charge carrier. Herein, P-introduced g-C3N4 (PC3N4) photocatalysts were constructed by partially replacing C with tributyl phosphate as precursor, and the as-designed PC3N4 photocatalysts were used to eliminate aqueous uranyl ion by photocatalytic reduction technology under visible-light irradiation. Experimental and DFT revealed that introduction of P into g-C3N4 significantly modified its electronic structure, as reflected by the narrowed band gap, enhanced visible-light absorption as well as improved transfer capability of photogenerated charge. Therefore, photocatalytic activity of PC3N4 was much better than that of pristine g-C3N4 and conventional reducing-type photocatalysts. This study suggests an efficient strategy for construct effective visible-light-responsive photocatalysts for radioactive environmental remediation.

Magnetically separable sulfur-doped SnFe2O4/graphene nanohybrids for effective photocatalytic purification of wastewater under visible light

In this report, magnetically recoverable sulfur-doped SnFe2O4/graphene (S-SFO/GR) nanohybrids have been successfully developed via a facile solvothermal method. The characterizations on the structural, morphology, and optical properties of the nanohybrids indicate that S-SFO particles are successfully embedded on the GR nanosheets. The photocatalytic activity has been evaluated by photocatalytic degradation of chlorotetracycline under visible light irradiation. Among the composites with various mass ratios, the quasi-first-order rate constant of the nanohybrids formed with 9wt% S in SFO and 15wt% GR (9S-SFO/GR-15) can reach as high as 1.83min−1, which is much higher than that of SFO (0.68min−1) and SFO/GR (0.91min−1), confirming the important role of S and GR for the photocatalytic process. The combination of the three components of S, SFO, and GR has enhanced the visible light absorption capability and inhibited the recombination of photogenerated electron-hole. The 9S-SFO/GR-15 nanohybrids can be recovered easily by a magnet and reused for five times with remained photocatalytic efficiency about 70%. A possible catalytic mechanism explaining the efficient photocatalytic performances of the prepared nanohybrids has been proposed.

Photocatalytic wastewater purification with simultaneous hydrogen production using MoS2 QD-decorated hierarchical assembly of ZnIn2S4 on reduced graphene oxide photocatalyst

It is attractive to photocatalytically purify wastewater and simultaneously convert solar energy into clean hydrogen energy. However, it is still a challenge owing to the relatively low photocatalytic efficiency of photocatalysts. In this study, we synthesized a molybdenum disulfide (MoS2) quantum dot-decorated 3D nanoarchitecture (MoS2QDs) of indium zinc sulfide (ZnIn2S4) and reduced grapheme oxide (MoS2QDs@ZnIn2S4@RGO) photocatalyst using a simple solvothermal method. The RGO promotes the electron transfer, and the highly dispersed MoS2QDs provides numerous catalytic sites. The photocatalytic purification of rhodamine B (RhB), eosin Y (EY), fulvic acid (FA), methylene blue (MB) and p-nitrophenol (PNP) in simulated wastewaters were further tested. The degradation efficiencies and TOC removal were 91% and 75% for PNP, 92.2% and 72% for FA, 98.5% and 80% for MB, 98.6% and 84% for EY, and 98.8% and 88% for RhB, respectively (Corganics = 20 mg/L, Ccatalyst = 1.25 g/L, t = 12 h, Ilight = 3.36 × 10−5 E L−1 s−1). Among these tests, the highest hydrogen production was achieved (45 μmol) during RhB degradation. Both experimental and calculational results prove that lower LUMO (lowest unoccupied molecular orbit) level of organic molecules was available for transferring electrons to catalysts, resulting in more efficient hydrogen production. Significantly, the removal efficiencies of natural organic substances in actual river water reached 76.3–98.4%, and COD reduced from 32 to 16 mg/L with 13.8 μmol H2 production after 12 h.

Cotton fabric-based facile solar photocatalytic purification of simulated real dye wastes

For the first time, this study presents solar photocatalytic processing of the real dye wastes remaining after finishing polyester/cotton (P/C) blends, rather than a pure organic dye solution as widely reported. A commonly used microencapsulation-based one-bath dyeing is investigated systematically, in order to simulate the real dyeing environment and to generate real dye wastes. The generated dye wastes are subsequently tackled by facile cotton fabric-based photocatalytic degradation involving a visible light-active TiO2 photocatalyst under solar light. Importantly, such a TiO2 photocatalyst is prepared without any calcination, doping, or coupling with plasmonic metal nanoparticles or narrow-band-gap semiconductors. As a result, the present visible light-responsive cotton fabric-based photocatalytic degradation of the simulated real dye wastes is expected to stimulate various industries for achieving simultaneous effective dyeing and processing of the dye wastes remained. This study also contributes to energy saving and environmental protection.