Natural Sunlight Irradiation Research Articles

Metalloporphyrin and Ionic Liquid-Functionalized Covalent Organic Frameworks for Catalytic CO2 Cycloaddition via Visible-Light-Induced Photothermal Conversion.

We report the construction of a porphyrin and imidazolium-ionic liquid (IL)-decorated and quinoline-linked covalent organic framework (COF, abbreviated as COF-P1-1) via a three-component one-pot Povarov reaction. After post-synthetic metallization of COF-P1-1 with Co(II) ions, the metallized COF-PI-2 is generated. COF-PI-2 is chemically stable and displays highly selective CO2 adsorption and good visible-light-induced photothermal conversion ability (ΔT = 26 °C). Furthermore, the coexistence of Co(II)-porphyrin and imidazolium-IL within COF-PI-2 has guaranteed its highly efficient activity for CO2 cycloaddition. Of note, the needed thermal energy for the reactions is derived from the photothermal conversion of the Co(II)-porphyrin COF upon visible-light irradiation. More importantly, the CO2 cycloaddition herein is a "window ledge" reaction, and it can proceed smoothly upon natural sunlight irradiation. In addition, a scaled-up CO2 cycloaddition can be readily achieved using a COF-PI-2@chitosan aerogel-based fixed-bed model reactor. Our research provides a new avenue for COF-based greenhouse gas disposal in an eco-friendly and energy- and source-saving way.

Straightforward Synthesis of Mn3O4/ZnO/Eu2O3-Based Ternary Heterostructure Nano-Photocatalyst and Its Application for the Photodegradation of Methyl Orange and Methylene Blue Dyes.

Zinc oxide-ternary heterostructure Mn3O4/ZnO/Eu2O3 nanocomposites were successfully prepared via waste curd as fuel by a facile one-pot combustion procedure. The fabricated heterostructures were characterized utilizing XRD, UV–Visible, FT-IR, FE-SEM, HRTEM and EDX analysis. The photocatalytic degradation efficacy of the synthesized ternary nanocomposite was evaluated utilizing model organic pollutants of methylene blue (MB) and methyl orange (MO) in water as examples of cationic dyes and anionic dyes, respectively, under natural solar irradiation. The effect of various experimental factors, viz. the effect of a light source, catalyst dosage, irradiation time, pH of dye solution and dye concentration on the photodegradation activity, was systematically studied. The ternary Mn3O4/ZnO/Eu2O3 photocatalyst exhibited excellent MB and MO degradation activity of 98% and 96%, respectively, at 150 min under natural sunlight irradiation. Experiments further conclude that the fabricated nanocomposite exhibits pH-dependent photocatalytic efficacy, and for best results, concentrations of dye and catalysts have to be maintained in a specific range. The prepared photocatalysts are exemplary and could be employed for wastewater handling and several ecological applications.

Photocatalytic activity of CdO/ZnO nanocomposite for methylene blue dye and parameters optimisation using response surface methodology

ABSTRACT In this work, CdO/ZnO nanocomposites was synthesised by chemical co-precipitation followed by thermal treatment method, characterised and its photocatalytic activity for the degradation of methylene blue (MB) dye studied. Study of the effects of operational parameters of dye initial concentration, catalyst dose, and pH on the degradation efficiency of the dye was carried out with response surface methodology (RSM) employing the central composite design (CCD) model and that the maximum predicted degradation percentage of the dye obtained was 81.6% at the optimum values of initial catalyst dose, dye concentration and reaction mixture pH of 30 mg, 13 ppm and 10, respectively, under natural sunlight irradiation for a period of 3 h. The measured experimental value at the indicated levels of the factors was 83.14% during the same degradation time and this is in reasonable agreement with the predicted value. Test for reactive radical species showed that HO. and O2 -. are engaged in the decomposition process of the dye. Further, the CdO/ZnO nanocomposite catalyst retained its degradation efficiency by about 96% over 4 consecutive cycles, indicating its stability and potential application for practical decontamination of wastewater from toxic organic pollutants.

(Invited) Particulate Photocatalysts with Perovskite-Type Structures and Their Application in Water Splitting

Sunlight-driven water splitting is studied actively for production of renewable solar hydrogen as a storable and transportable energy carrier. Both the efficiency and scalability of water- splitting systems are essential factors for practical application of renewable solar hydrogen because of the low areal density of solar energy [1]. It is desirable to develop particulate photocatalysts and their reaction systems that efficiently split water, because such systems can be spread over wide areas by inexpensive processes potentially. The author’s group has studied various oxide and oxynitride semiconductors as photocatalysts for water splitting. In my talk, recent progress in photocatalytic materials and reactors will be presented with focus on perovskite-type materials.SrTiO3 loaded with proper cocatalysts has been known to be active in overall water splitting under ultraviolet light irradiation since 1980s. Recently, the apparent quantum yield (AQY) of this photocatalyst in overall water splitting has been improved drastically [2]. The author's group has found that doping Al3+ into the titanium site of SrTiO3 boosts the water splitting activity by two orders of magnitude [3]. By refining the preparation conditions of the Al-doped SrTiO3 (SrTiO3:Al) photocatalyst and the loading conditions of cocatalysts working as hydrogen and oxygen evolution sites, the AQY of overall water splitting has reached more than 90% at 365 nm [2], equivalent to an internal quantum efficiency of almost unity. This quantum efficiency is the highest yet reported and indicate that a particulate photocatalyst can drive the greatly endergonic overall water splitting reaction at a quantum efficiency comparable to values obtained from photon-to-chemical or photon-to-current conversion in photosynthesis or photovoltaic systems, respectively.Photocatalyst sheets based on SrTiO3:Al contained in a panel-type reactor split water into hydrogen and oxygen and release gas bubbles at a rate corresponding to a solar-to-hydrogen energy conversion efficiency of 10% under intense ultrviolet illumination even when the water depth is merely 1 mm [4]. Moreover, the photocatalyst can maintain 80% of its initial activity during 1300 h of constant simulated sunlight irradiation at ambient pressure with appropriate surface modifications [5]. A prototype 1-m2-sized panel reactor containing SrTiO3:Al photocatalyst sheets splits water under natural sunlight irradiation without a significant loss of the intrinsic activity of the photocatalyst sheets. A solar hydrogen production system with a greater size (100 m2) was recently built, and its performance and system characteristics are under investigation.SrTiO3:Al harvests only the ultraviolet light of the sunlight. It is essential to develop photocatalysts active under visible light irradiation. BaTaO2N is a visible light that can evolve hydrogen and oxygen from aqueous solutions containing sacrificial electron donors and acceptors, respectively. Recently, the AQYs of BaTaO2N in these sacrificial reactions have been improved significantly. Highly-crystalline BaTaO2N can be synthesized by directly nitriding a mixture of BaCO3 in the presence of RbCl flux [6]. The resultant BaTaO2N shows decent hydrogen evolution activity when a platinum cocatalyst is loaded by impregnation. By optimizing the cocatalyst loading conditions, the electron transfer from the BaTaO2N photocatalyst to the platinum cocatalyst, and thus the hydrogen evolution activity, was enhanced. The AQY of the resultant Pt-loaded BaTaO2N reached 6.8% at 420 nm in the sacrificial hydrogen evolution reaction. This is exceptionally high among nitride-type photocatalysts with visible light absorption of up to 650 nm.In conventional synthesis, BaTaO2N is nitrided from a mixture of BaCO3, Ta2O5, Ba- and Ta-containing complex oxides, often in the presence of flux. However, these starting materials have different crystal structures from the product BaTaO2N, and so the crystal structures have to be change during the nitridation. This is thought to induce defects in the product material. Therefore, a perovskite-type oxide with a Ba/Ta molar ratio of unity was designed, namely a complex oxide nominally denoted as Na1/4Ba3/4Zn1/4Ta3/4O3 [7]. This oxide can be nitrided into BaTaO2N because Na and Zn components are volatile at high temperature. The resultant BaTaO2N exhibited an AQY of 11.9% at 420 nm in the sacrificial oxygen evolution reaction after loading of a cobalt oxide cocatalyst. Hisatomi et al. Catal. 2019, 2, 387.Takata et al., Nature 2020, 581, 411.Ham et al., Mater. Chem. A 2016, 4, 3027.Goto et al., Joule 2018, 2, 509.Lyu et al. Sci. 2019, 10, 3196.Luo et al., Growth Des. 2020, 20, 255.Jadhav et al. J. Mater. Chem. A. 2020, 8, 1127.

Construction of MoO3 nanopaticles /g-C3N4 nanosheets 0D/2D heterojuntion photocatalysts for enhanced photocatalytic degradation of antibiotic pollutant

A new type of 0D-2D Z-scheme heterojunction photocatalyst (MoO3/g-C3N4) was successfully prepared via simple hydrothermal calcination method. The catalytic activities of MoO3/g-C3N4 was evaluated by the degradation effect of tetracycline. The results indicated that the 0D-2D MoO3/g-C3N4 Z-scheme heterojunction was significantly better than that of original g-C3N4. Especially, the optimal 0.5 wt% MoO3/g-C3N4 could reach 85.9% removal efficiency within 100 min under visible light irradiation (λ > 420 nm), and its degradation rate constant was 2.3 times higher than that of g-C3N4·In addition, the effects of real water matrix, natural sunlight irradiation on tetracycline removal were examined. Reactive-species-trapping experiments show that both photo-generated •O2− and h+ are the main active species in the photocatalytic process. Besides, the results of •O2− and •OH detection further indicated that the yield amount of •O2− and •OH in MoO3/g-C3N4 case showed enhancement when compared with g-C3N4. Moreover, the quite stable crystal structure and excellent recycling ability endowed the MoO3/g-C3N4 composite with a great potential for applying in photocatalytic fields.

Bandgap engineering of tetragonal phase CuFeS2 quantum dots via mixed-valence single-atomic Ag decoration for synergistic Cr(VI) reduction and RhB degradation

Bandgap engineering through single-atom site binding on semiconducting photocatalyst can boost the intrinsic activity, selectivity, carrier separation, and electron transport. Here, we report a mixed-valence Ag(0) and Ag(I) single atoms co-decorated semiconducting chalcopyrite quantum dots (Ag/CuFeS2 QDs) photocatalyst. It demonstrates efficient photocatalytic performances for specific organic dye (rhodamine B, denoted as RhB) as well as inorganic dye (Cr(VI)) removal in water under natural sunlight irradiation. The RhB degradation and Cr(VI) removal efficiencies by Ag/CuFeS2 QDs were 3.55 and 6.75 times higher than those of the naked CuFeS2 QDs at their optimal pH conditions, respectively. Besides, in a mixture of RhB and Cr(VI) solution under neutral condition, the removal ratio has been elevated from 30.2% to 79.4% for Cr(VI), and from 95.2% to 97.3% for RhB degradation by using Ag/CuFeS2 QDs after 2 h sunlight illumination. The intrinsic mechanism for the photocatalytic performance improvement is attributed to the narrow bandgap of the single-atomic Ag(I) anchored CuFeS2 QDs, which engineers the electronic structure as well as expands the optical light response range. Significantly, the highly active Ag(0)/CuFeS2 and Ag(I)/CuFeS2 effectively improve the separation efficiency of the carriers, thus enhancing the photocatalytic performances. This work presents a highly efficient single atom/QDs photocatalyst, constructed through bandgap engineering via mixed-valence single noble metal atoms binding on semiconducting QDs. It paves the way for developing high-efficiency single-atom photocatalysts for complex pollutions removal in dyeing wastewater environment.

Single-Step Production of a TiO2@MoS2 Heterostructure and Its Applications as a Supercapacitor Electrode and Photocatalyst for Reduction of Cr(VI) to Cr(III).

In this study, we have reported a one-step synthesis of a TiO2@MoS2 heterostructure. TiO2@MoS2 was synthesized using a facile and cost-effective method. The as-synthesized TiO2@MoS2 heterostructure was characterized by suitable spectroscopic techniques. The obtained TiO2@MoS2 was utilized as a supercapacitor electrode material. Electrochemical studies show that the TiO2@MoS2 heterostructure possesses a specific capacitance of 337 F/g at a current density of 1 A/g in an aqueous solution. Furthermore, an application as a photocatalyst for the photoreduction of toxic hexavalent chromium was reported for the first time. This heterostructure showed the photoreduction of Cr6+ to Cr3+ in 120 min with formic acid as a scavenger under direct sunlight. A plausible mechanism of photoreduction of Cr6+ to Cr3+ under natural sunlight irradiation using TiO2@MoS2 is proposed.

Efficient solar light facilitated photo-oxidative detoxification of gaseous 2-chloroethyl ethyl sulfide on ZrO2-doped g-C3N4 under dry and humid air

Photo-oxidation of chemical warfare agents is considered a promising strategy to cope with threats from accidental or intentional release. In this study, heterostructure photocatalysts comprising different amounts of zirconium oxide (ZrO2) over carbon nitride (CN) were synthesized via simple thermal exfoliation, followed by a precipitation method. The successful photocatalytic detoxification activity of the as-prepared photocatalyst was analyzed against 2-chloroethyl ethyl sulfide (CEES) under simulated solar light and natural sunlight irradiation in dry and humid air. As the CN/ZrO2 demonstrated a high surface area and oxygen doping, the addition of small amounts of the ZrO2 phase could lead to enhanced photoreactivity in surface chemistry. The as-prepared (CN/ZrO2-II) degraded 95% of CEES under simulated solar light and 70% under natural sunlight within 90 min. The photo-detoxification of CEES was associated with the generation of holes (h+) and activation of oxygen to superoxide radicals (•O2). Based on analysis results, a reaction mechanism was suggested. The activity of the used photocatalyst could be recovered to 90% of the fresh photocatalyst activity via simple water washing. However, as sulfurous compounds were accumulated on the surface in subsequent cyclic tests, solvent washing was also suggested to maintain high detoxification performance.

Low-cost and large mass producible phenolic resin for water disinfection and antibacterial coating under weak visible light LED or sunlight irradiation

In present study, we for the first time discovered the photocatalytic water disinfection and antibacterial ability of phenolic-formaldehyde (PR) resins irradiated by LED lamp or natural sunlight in various application modes. The novel narrow band-gap, low-cost and large mass easily producible resin photocatalysts exhibit advanced and stable Escherichia coli (E. coli) inactivation performance, which is better than some well-known metal and non-metal based visible light photocatalysts under the identical condition. We have provided a proof-of-concept demonstration of its practical application feasibility for water purification in both immobilized plastic bag and continuous flow-through reactor under weak LED lamp or natural sunlight irradiation. Furthermore, the PR resin coating film exhibits remarkable E. coli deactivation property under weak LED lamp irradiation. This work provides a new approach for developing resin-based products with antibacterial function or solar water purification products for practical use.

Facile Fabrication of a Mechanical, Chemical, Thermal, and Long‐Term Outdoor Durable Fluorine‐Free Superhydrophobic Coating

AbstractDespite their great self‐cleaning, anti‐dust, and anti‐icing properties superhydrophobic coatings show great promise in various practical applications in solar cells, car windows, powerlines, etc., superhydrophobic coatings encounter a large resistance in large‐scale practical applications due to their unsatisfactory long‐term mechanical, chemical, thermal, and weathering durability. This study demonstrates a cost‐effective, large‐scale applicable, mechanical, chemical, thermal, and long‐term weathering durable fluorine‐free superhydrophobic coating. This coating can be prepared with a simple spin‐coating or doctor‐blade painting or spray‐brush method, using SiO2 nanoparticles coated with methyl MQ silicone resin (Me‐MQ), and y‐methacryloxypropyltrimethoxysilane (KH‐570). This coating displays remarkable super‐hydrophobic performance with a large water contact angle of 168.8°, and a small sliding angle less than 1.0°, which survives tape peeling, sand impact, sandpaper abrasion, etching in acidic and alkaline environments, baking at high temperature up to 550 °C, and long‐term exposure to outdoor natural environment (under 16 months’ natural sunlight irradiation, UV irradiation, rain falls, high PM2.5, dust accumulation, etc.). The materials used are non‐fluorine, non‐toxic, environmentally friendly, and can be effectively applied to large glass surfaces using cost‐effective doctor‐blade painting and spray‐brush methods towards large‐scale applications. Therefore, this work can inspire and advance researches on superhydrophobic coatings towards practical applications.

Photodynamic inactivation of Lasiodiplodia theobromae: lighting the way towards an environmentally friendly phytosanitary treatment.

The fungus Lasiodiplodia theobromae is one of the main causal agents of trunk canker and dieback of grapevine. The objective of this work was to evaluate the efficiency of photodynamic inactivation (PDI) of L. theobromae with synthetic and natural photosensitizers and irradiation with either sunlight or artificial photosynthetically active radiation. Although the growth of the mycelium could not be completely prevented with natural sunlight irradiation, phenothiazine dyes (methylene blue, MB; toluidine blue O, TBO), riboflavin and a cationic porphyrin (Tetra-Py+-Me) caused complete inhibition under continuous irradiation with artificial light. Free radicals were the main cytotoxic agents in the PDI with MB, indicating the predominance of the type I mechanism. PDI with MB or Tetra-Py+-Me may represent a promising approach for the sanitation of vine material in greenhouse nurseries, in order to reduce the risk of infection upon grafting.

Control of Structural Coloration by Natural Sunlight Irradiation on a Melanin Precursor Polymer Inspired by Skin Tanning.

Natural melanin affects the reflection and absorption of light, and it is known as an important element in producing bright structural colors in nature. In this study, we prepared core-shell particles using a melanin precursor polymer, that is, polytyrosine (PTy), as a shell layer by the oxidative polymerization of tyrosine ethyl ester (Ty) in the presence of cerium oxide (CeO2) core particles. Inspired by skin tanning, irradiating the CeO2@PTy core-shell particles with UV or natural sunlight caused melanization by extending the π-conjugated length of PTy, producing colloidal particles with the ability to absorb light. The pellet samples consisting of CeO2@PTy particles appeared whitish because of multiple scattered light. In contrast, the light absorption capacity of CeO2@PTy UV or CeO2@PTy Sun particles after light irradiation suppressed scattered light, dramatically improving the visibility of the structural color of the pellet samples made from these particles. Thus, a new method has been developed to control the visualization of structural colors to the human eye by irradiating the melanin precursor polymer with light.

Donor–Acceptor Type Conjugated Microporous Polymer as a Metal-Free Photocatalyst for Visible-Light-Driven Aerobic Oxidative Coupling of Amines

Developing cheap, highly efficient, metal-free heterogeneous photocatalysts remain a great challenge in photoredox reactions. Herein, we utilize a typical Suzuki coupling of low-cost triphenylamine derivative and 9,10-dibromoanthracene to synthesis a donor–acceptor type conjugated microporous polymer (denoted as PAA-CMP). As expected, heterogeneous PAA-CMP exhibits excellent photocatalytic performance, good functional group tolerance and satisfying recyclability in metal-free aerobic oxidative coupling of amines to imines driven by visible light, which is due to its absolute energy level positions and good physicochemical stability. More excitingly, PAA-CMP can enable the gram-scale air-oxidized photocatalytic conversion under natural sunlight irradiation, yielding the desired imine product with an isolated yield of 65% for 48 h. The current work provides a great application prospect for CMPs in low-cost and large-scale organic industrial production in the future. The prepared donor-acceptor (D-A) type conjugated microporous polymer (PAA-CMP) as a metal-free and heterogeneous photocatalyst enable the gram-scale air-oxidized photocatalytic conversion of benzylamine into N-benzylidenebenzylamine under natural sunlight irradiation, yielding the desired imine product with an isolated yield of 65%.

Novel rare earth ions doped Bi2WO6/rGO hybrids assisted by ionic liquid with enhanced photocatalytic activity under natural sunlight

Rare earth ions doped Bi2WO6/rGO hybrids (Re-BWG) were synthesized by a two-step process, and the introduction of rGO was achieved with the assistance of imidazole based ionic liquids (IL). IL could enhance the dispersion uniformity of rGO, which was beneficial to the combination of Bi2WO6 (BWO) and rGO. Rare earth ions and rGO increased the separation of electron–hole pairs of BWO and enhanced the adsorption for pollutants. Physical-chemical properties of BWO and Re-BWG were investigated by XRD, SEM/TEM, XPS, UV-Vis DRS, PL, EIS, and N2 adsorption analysis. The photocatalytic activity of Re-BWG was envaulted by rhodamine (RhB) degradation under natural sunlight irradiation. Re-BWG possessed excellent photocatalytic activity compared to pure BWO. The proposed mechanism of photocatalytic degradation was deduced, in which the photogenerated O2•- and h+ (on the surface of Re-BWG) played the role of active species during reaction. The photocatalytic performance of Er-BWG was better than the other three Re (La, Ce, and Pr)-BWG hybrids, and the RhB removal efficiency was up to 99.12% within 60 min.

Stable and highly efficient natural sunlight driven photo-degradation of organic pollutants using hierarchical porous flower-like spinel nickel cobaltite nanoflakes

Hierarchical porous flower-like spinel nickel cobaltite (NiCo2O4) nanoflakes was synthesized by using simple and economical chemical method. The structure, morphology and optical properties of synthesizes nanoflakes were analyzed by using XRD, FE-SEM and UV–visible. The NiCo2O4 nanoflakes showed 96% degradation of TBO in 50 min and after 10 cycles of operation, the photocatalytic activity was enough for the 89% degradation of TBO under natural sun light. When compared with other photocatalysts materials, porous NiCo2O4nanoflakes showed excellent thermal and chemical stability and offer exceptional electron transfer rate during photocatalytic reactions for real environmental pollution cleanup applications. The efficient photocatalytic efficiency and stability of NiCo2O4 nanoflakes is attributed to its inimitable structure with large surface area along with maximum active sites. This augments the efficiency of harvesting sun light, and spread active species over surface to decrease e-/h+ pair recombination. On the whole, this work demonstrates that the synthesis of nanoflower NiCo2O4 can be used as potential candidate to remove organic pollutant and infections from water under natural sun light irradiations for industrial applications.

Excellent Photocatalytic degradation of Methylene Blue, Rhodamine B and Methyl Orange dyes by Ag-ZnO nanocomposite under natural sunlight irradiation

Highly efficient silver assisted ZnO nanocomposite (AZ) was fabricated by using the co-precipitation method. HR-SEM reveals the presence of nano rods, plates and balls. The incorporation of silver to ZnO reduces the bandgap of ZnO by the Surface Plasmon Resonance effect and this leads to the shift in the emission spectra from ultraviolet (UV) to the visible region. This provide an opportunity to capture large number of photons from the sunlight. The photocatalytic test was conducted under natural sunlight with cationic and anionic dyes. Among all the prepared samples, AZ-1 exhibited the highest photocatalytic degradation efficiency over methylene blue (MB) dye. The prepared samples would create the new pathway for degrading the industrial waste water treatment process.

Ultra-fast photoreduction of toxic Cr(VI) by CdS-rGO synthesized using single source precursor

Abstract Cadmium sulfide decorated with reduced graphene oxide (CdS-rGO) nanocomposites were synthesized by CdI2(LH)2 complex [where, LH = benzaldehyde thiosemicarbazone]. Various spectroscopic and analytical techniques were used for the characterization of the cadmium complex. The solvothermal decomposition method was employed to obtain CdS-rGO using CdI2(LH)2 complex as a single-source precursor (SSP) for CdS along with graphene oxide as the precursor for rGO and ethylene glycol as a solvent. The powder X-ray diffraction study of resultant CdS-rGO nanocomposites revealed a hexagonal phase for CdS. Scanning electron microscopy shows hierarchically structured cadmium sulfide-reduced graphene oxide nanocomposites. Transmission electron microscopy images reveal CdS nanoparticles associated with reduced graphene oxide sheets to form a nanocomposite. Raman spectroscopic studies show phonon mode at 310 cm−1 associated with the hexagonal phase of CdS. the band at 1349 cm−1and 1596 cm−1 correspond to phonon modes of rGO. The CdS-rGO nanocomposites demonstrated ultra-fast reduction of toxic Cr(VI) to less toxic Cr(III) under sunlight. A plausible mechanism for photoreduction of Cr(VI) to Cr(III) using CdS-rGO under natural sunlight irradiation is proposed. The role of valence and conduction band potential with a calculated redox potential of an acceptor species and facile transfer of electrons for fast photoreduction of Cr(VI) to Cr(III) is also discussed.

PH-controlled mechanism of photocatalytic RhB degradation over g-C3N4 under sunlight irradiation.

Photocatalysis of dye degradation is one of green and cheap technologies for solving environmental pollution. Whereas it is rarely concerned that the degradation process varied with the change of solution condition, this work studied the influence of hydrion in the solution on the photodegradation process of Rhodamine B (RhB) over g-C3N4. The photocatalytic activity of RhB degradation was enhanced gradually with increased hydrion content in the system. The efficiency for RhB degradation over g-C3N4 in weak acidic system with interference of multiple metal-ions still reached near 95% after 30min of natural sunlight irradiation. A large amount of oxidation species and the hydroxylation mineralization process were induced by increasing the hydrion concentration. Two degradation processes for deethylation of four ethyl groups and the direct chromophoric degradation were discovered and proved by multifarious intermediates in different systems using the ESR technique, LC/MS and GC/MS analysis. In addition, the photosensitization played a critical role in the RhB degradation. A feasible degradation mechanism was proposed for the RhB degradation based on the experimental results.

A comparative study of photo-Fenton process assisted by natural sunlight, UV-A, or visible LED light irradiation for degradation of real textile wastewater: factorial designs, kinetics, cost assessment, and phytotoxicity studies

The present work aims to evaluate the treatment of the effluent from the textile industry via advanced oxidative processes of photo-Fenton assisted by different sources (natural sunlight, UV-A or visible LED lamps). To identify the best operating conditions, a factorial design was carried out for each process. It was observed that after the optimization of the processes, chemical oxygen demand (COD) removals greater than 88% were achieved. In addition, it was observed that the use of the LED lamp required lower reagent concentrations compared to solar and UV-A sources. A kinetic study was carried out under the best conditions obtained and it was observed that the sources showed rapid evolution, reaching a COD removal equilibrium with 30 min of reaction. Reagent monitoring was also carried out, and it was observed that they were not limiting to the reaction. Phytotoxicity analysis was also satisfactory since the treated effluents allowed a higher relative growth and germination index of the cucumber roots compared to the raw effluent. Finally, the cost analysis indicated that the use of LED lamps resulted in a reduction in electrical consumption compared to the UV-A lamp, as well as a reduction in the cost of reagents due to the lower concentration of reagents required compared to processes assisted by natural sunlight and UV-A.

Photoelectrocatalytic degradation of humic acid and disinfection over Ni TiO2-Ni/ AC-PTFE electrode under natural sunlight irradiation: Modeling, optimization and reaction pathway

NiTiO2NT and TiO2 nanotube-based photoelectrodes were prepared by anodic oxidation and employed for the degradation of humic acid (HA) and disinfection simultaneously by the photoelectrocatalytic (PEC) process under natural sunlight irradiation. Scanning electron microscopy coupled with energy-dispersive spectroscopy (EDX) studies confirmed that uniform nanotubes TiO2 covered all surface of Ti foil and Ni doped to TiO2NT. The highest efficiency for HA degradation and disinfection rate by PEC was observed for the NiTiO2NT photoelectrode. The influences of different parameters such as initial HA concentration (2–8 mg/L), voltage (2–20 V), bacterial density (2 × 102,104,107 CFU), time (30–60 min), light source (UV–Vis) and type of electrode (NiTiO2NT/AC-PTFE, TiO2NT/AC-PTFE) on disinfection of water and degradation of the HA were studied using response surface methodology (RSM). The results showed that the maximum degradation rate of HA and Log bacterial removal reached 87.18% and 3.77 after 60 min reaction time at a 20 V voltage with NiTiO2NT/AC-PTFE electrode and UV as a source of irradiation. Also, results showed that doping Ni to TiO2NT electrode increase PEC efficiency under Vis-light source. To determine the HA degradation pathway, the organic byproducts were identified by GC–MS analysis.