Min Of Solar Light Irradiation Research Articles

Sodium titanium oxide/zinc oxide (STO/ZnO) photocomposites for efficient dye degradation applications

Abstract In this study, sodium titanium oxide (Na2Ti3O7, termed STO) and sodium titanate/zinc oxide (STO/ZnO) photocomposites were prepared for the first time. A low-cost hydrothermal technique was employed to fabricate the STO/ZnO photocomposites with varying ZnO weight ratios: STO/0.25ZnO, STO/0.5ZnO, and STO/ZnO. The prepared photocomposites were investigated for the decomposition of methylene blue dye (MB) under natural visible light illumination and an artificial tungsten halogen lamp. The STO/ZnO photocomposite exhibits high photodegradation performance, which can be correlated with its properties and characterization. The X-ray diffraction analysis reveals that STO has an average crystallite size of 69.1 nm, ZnO has an average crystallite size of 41.4 nm, and the combination of STO/ZnO results in a reduced average crystallite size of 39.5 nm. The bandgap (E g) of STO/ZnO is 2.53 eV after controlling the ZnO weight ratio. The photocatalytic efficiency of the STO/ZnO photocomposite was 100% for MB within 60 min of solar light irradiation, compared to 33.7% for STO and 25.8% for ZnO. The effect of STO/ZnO dosage and MB concentration was investigated. Furthermore, the kinetics and mechanisms of the photocatalytic process were examined. The results suggest that STO/ZnO has promising potential for practical applications in wastewater treatment.

Preparation, characterization of green synthesis FeO nanoparticles and their photocatalytic activity towards Basic Fuschin dye

In the current study, a green and facile route for the synthesis of iron oxide nanoparticles (FeO-NPs) was adopted. The FeO-NPs were fabricated via a single step green route using aqueous leaf extract of Aegle marmelos (A. marmelos) as capping/reducing and stabilizing agents.The active phytochemicals present in the A. marmelos extract was reduced and stabilized the metal ions to FeO-NPs. This product was analyzed by FTIR spectral studies. Magnetic FeO-NPs surface morphology and particles sizes were determined by HRTEM to reveals spherical shapes with average diameter 18.78 nm. The instrumentally confirmed FeO-NPs were determining the antimicrobial activity against the pathogenic strains of the bacteria Streptococcus Sp and the fungus Candida Sp. The results of the microbial investigation show that when the concentration of synthesized FeO-NPs increase with the increases the activity. The antioxidant properties of synthesized FeO-NPs were evaluated by the DPPH assay. The FeO-NPs displayed a dose-dependent cytotoxicity property against breast carcinoma MDA-MB-231 cells, and the value of IC50 was found to be 304 μg/mL. The obtained FeO-NPs were used as photocatalyst in the degradation/reduction of environmentally polluted organic wastewater dyes. After 20 min of solar light irradiation shows 97 % of degradation efficiency was achieved with 1 mL of FeO-NPs. It is observed all the results, the green synthesized FeO-NPs could be effectively materials and used in several fields like industrial, agricultural, medical, food safety, and dye waste applications.

Eco-friendly synthesis of biochar supported with zinc oxide as a heterogeneous catalyst for photocatalytic decontamination of Rhodamine B under sunlight illumination

In the current study, biochar, as a porous and low-cost carbon derived from Pontederia crassipes L. leaves, was loaded with zinc oxide for the photocatalytic discoloration of Rhodamine B dye in aqueous suspension under solar light irradiation. For the comparison, the unmodified zinc oxide and biochar samples were prepared. The synthesizing materials were investigated by X-ray powder diffraction, UV-DRS spectrophotometer, field emission scanning electron microscopy, Fourier transform infrared spectrometer, and Raman spectroscopy. The synthesized ZnO/Biochar hybrid has improved features, besides narrowing the band gap energy, and enhancing the surface area of the photocatalyst. The ZnO/biochar nanohybrid displayed an excellent photocatalytic degradation efficiency (99. 67 %) of Rhodamine B in the presence of H2O2 with 120 min of solar light irradiation. The results of recyclability study of ZnO/Biochar in the photocatalysis process verified its physical and chemical stability after five repeated cycles, hence it retained of 82.24 % of initial activity. Furthermore, the photocatalytic discoloration reaction was compatible with the pseudo-first-order kinetic model

Investigating carrier mobility in hollow and mesoporous ZnSe/ZnTe heterostructures: Microscopic observations of swift charge transfer and visible-light-driven dye decomposition

We report herein a one-pot hydrothermal approach to synthesize zinc selenide (ZnSe)/zinc telluride (ZnTe) heterostructures - a set of common cation-based photocatalysts. The crystal structure and phase purity of the heterostructures were verified by powder X-ray diffraction (PXRD) analysis, while field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques were employed to study their morphology, microstructures, and surface electronic states, respectively. Notably, a detailed XPS analysis was conducted to discern the chemical species present on the surface of the photocatalyst, providing valuable insights into the compound's stability in an aqueous medium. Furthermore, the synthesized hybrid structures were utilized to fabricate Schottky barrier diodes, enabling a study of their electrical and dielectric properties using the Spatial-charge-limited conduction (SCLC) mechanism. The key charge transport parameters for all the photocatalysts, namely, carriers' mobility and transit time, influencing the photo response and consequently, dye degradation were estimated. Notably, the ZnSe/ZnTe heterostructure, comprising 50 % ZnSe and 50 % ZnTe, exhibited the highest mobility (3.36 × 10-6 S/m in the dark, increasing to 1.70 × 10-5 S/m in light) and proved to be the most effective photocatalyst for degrading Rhodamine B (with up to ∼ 78 % degradation over 60 min of solar light irradiation) - underscoring the pivotal role of carriers' mobility in governing the photocatalytic activity. Moreover, the ZnSe/ZnTe heterostructure demonstrated a remarkable reduction in the photo-corrosion process, a key challenge affecting the photocatalytic activity of numerous materials. Our discussion highlighted the efficient separation of photoinduced electron-hole pairs in the ZnSe/ZnTe heterostructure, facilitated by the synergistic effects of ZnSe and ZnTe, leading to the achievement of the highest photocatalytic performance.

Tuning the Photocatalytic Performance of Ni-Zn Ferrite Catalyst Using Nd Doping for Solar Light-Driven Catalytic Degradation of Methylene Blue

In this paper, we describe the creation of a moderate band gap Nd-substituted Ni-Zn ferrite as a nano photo catalyst via a simple and cost-effective process of solution combustion. Nd substitution alters the crystallite size, shape, band gap, and magnetic characteristics of Ni-Zn ferrite significantly. Investigations using X-ray diffraction revealed that all samples display a pure phase. The average crystallite size was determined to be between 31.34 and 38.67 nm. On Nd doping, morphology investigations indicated that the shape of nanoparticles changed from approximately spherical to stacked grains. Band gap experiments confirmed the red shift in optical band gap on Nd doping. The synthesized catalysts Ni0.5Zn0.5Fe2O4 (Nd0), Ni0.5Zn0.45Nd0.05Fe2O4 (Nd1), and Ni0.5Zn0.5Nd0.05Fe1.95O4 (Nd2) have been effectively used for the degradation of methylene blue dye under the solar light irradiation. The sample with Nd substitution on Fe sites had the highest methylene blue degradation efficiency. Nd2 photo catalyst degrades the methylene blue dye with a degradation efficiency of 98% in 90 min of solar light irradiation. The photocatalytic activity is triggered by the existence of oxygen vacancies and a mixed valence state of Ni, Fe, and Nd, as confirmed by the XPS investigation. In addition, the investigations on scavenging reveal that the hydroxyl radical is a reactive component in the degradation process. The degradation route has been investigated in relation to the many potential reactions and discovered reactive substances.

G-C3N4 nanosheets functionalized yttrium-doped ZrO2 nanoparticles for efficient photocatalytic Cr(VI) reduction and energy storage applications

Novel g-C3N4 functionalized yttrium-doped ZrO2 hybrid heterostructured (g-YZr) nanoparticles have been synthesized to investigate photocatalytic Cr(VI) reduction as well as electrochemical energy storage applications. The nanoparticles have been characterized to examine their structural, optical, and photocatalytic properties. XRD confirmed the incorporation of dopant ions and heterostructure development between g-C3N4 and doped ZrO2. When g-C3N4 was doped with ZrO2, the ability of light adsorption was greatly enhanced due to the narrow band gap. The distinctive structure of g-YZr exhibited outstanding photocatalytic Cr(VI) reduction owing to its superior surface area, which greatly prevented the charge carriers' recombination rate and exhibited superior photocatalytic performance within 90 min of solar light irradiation. Furthermore, these catalysts demonstrated similar catalytic Cr(VI) reduction activity following four repeatability tests, indicating the exceptional structural stability of g-YZr catalysts. The electrochemical performance of the electrodes revealed that g-YZr exhibited superior specific capacitance over the other electrodes owing to extra energetic sites and robust synergic effect. Enhanced specific capacitance and long cyclic stability of the hybrid heterostructures displayed their usefulness for energy storage applications.

Fabrication of TiO2/NiO p-n Nanocomposite for Enhancement Dye Photodegradation under Solar Radiation.

A p-n nanocomposite based on TiO2 nanotubes (NTs) and NiO nanoparticles (NPs) was designed and optimized in this study to improve the photocatalytic performance of methylene blue (MB). The hydrothermal technique has been used to produce TiO2/NiO nanocomposites with different NiO NPs weight ratios; 1TiO2:1NiO, 1TiO2:2NiO, and 1TiO2:3NiO. The crystal phase, chemical composition, optical properties, and morphology of TiO2/NiO were explored by various techniques. TiO2 NTs have a monoclinic structure, while NiO NPs have a cubic structure, according to the structural study. The bandgap of TiO2 NTs was reduced from 3.54 eV to 2.69 eV after controlling the NiO NPs weight ratio. The TiO2/2NiO nanocomposite showed the best photodegradation efficiency. Within 45 min of solar light irradiation, the efficiency of MB dye degradation using TiO2/2NiO hits 99.5% versus 73% using pure TiO2 NTs. Furthermore, the catalytic photodegradation efficiency did not deteriorate significantly even after five reusability cycles, intimating the high stability of the TiO2/2NiO nanocomposite. This suggests that the loading of NiO NPs into TiO2 NTs lowers the recombination of photo-produced electron/hole pairs and enlarged solar spectral response range, which results in improved photocatalytic activity. The mechanism of charge transfer in the TiO2/NiO and kinetic models were discussed for the photodegradation of MB.

Solar-light-driven photocatalytic performance of Cr and Co doped Sr1-xCoxFe12-yCryO19 and effect of doping on optical, structural and dielectric properties

A series of Co2+ and Cr3+ doped strontium hexaferrite (Sr1-xCoxFe12-yCryO19) nanoparticles were synthesized via micro-emulsion technique. Effect of Co and Cr ions doping was estimated using structural, dielectric, photocatalytic and optical properties of Sr1-xCoxFe12-yCryO19. The Sr1-xCoxFe12-yCryO19 were characterized employing X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR), (Scanning electron microscopy) SEM and UV–Vis spectroscopy. The XRD analysis confirmed formation of hexagonal M-type ferrites with average crystallite size of 38 nm. Dielectric properties analysis revealed that the of Sr1-xCoxFe12-yCryO19 has high dielectric constant, low dielectric and tangent loss versus SrFe12O19. The band gap energy decreased with the Co2+ and Cr3+ contents due to incorporation of sub band gaps and reduction of particle size. The photocatalytic activity (PCA) of Sr1-xCoxFe12-yCryO19 was evaluated by degrading the Rhodamine B (RhB) dye under solar light irradiation. The Sr1-xCoxFe12-yCryO19 degraded up to 87.6% of dye in 45 min of solar light irradiation with rate constant of 0.03834 min−1. Results revealed that Co2+ and Cr3+ doping tuned the optical properties and Sr1-xCoxFe12-yCryO19 has potential to harvest the solar light for photocatalytic applications. The high electrical conductivity and tuned band gap make such materials as feasible to utilize them efficiently in photovoltaic cells, SOFCs and as an encouraging photocatalyst for water remediation.

Hydrothermal synthesis of ZnO photocatalyst for detoxification of anionic azo dyes and antibiotic

The ZnO photocatalysts were prepared by a hydrothermal method by using the Zn2+/OH− mole ratio of 1:5, 1:12, and 1:18 denoted as ZnO-1, ZnO-2, and ZnO-3, respectively. All prepared photocatalysts showed the hexagonal phase with the band gap energy of around 3.19 eV and the specific surface area of about 10.6 m2g-1. These photocatalysts remained stable even heating up to 1000 °C. Interestingly, the synthesized ZnO-1photocatalyst provided the lowest PL intensity among all prepared photocatalysts. This indicated the lowest electron-hole recombination rate at the interface. Therefore, this sample exhibited the highest photoactivity. The complete photodegradation of RR141, CR, and OFL pollutants after 20, 60 and 180 min of solar light irradiation, respectively, was obtained. The photodegradation of the pollutants correlated well with the first-order kinetics model. The corresponding rate constants of 0.1432, 0.0494 and 0.0304 min−1 toward degradation of RR141, CR and OFL, respectively, were reported. The stability of the ZnO-1 photocatalyst after three times of use was confirmed. The ZnO-1 photocatalyst still provided high performance even after the third cycle indicating its promising reusability. The photogenerated electron played a vital role in removal of the pollutants. The present research demonstrates a promising route for fabrication of ZnO photocatalyst with high efficiency for detoxification of organic pollutants in wastewater.

Solar light-driven CoFe2O4/α-Ga2O3 heterojunction nanorods mediated activation of peroxymonosulfate for photocatalytic degradation of norflurazon

Low frequency (40 kHz) ultrasound-assisted technique was utilized in the synthesis of CoFe2O4, GaOOH and α-Ga2O3 nanorods. CoFe2O4 was tethered successfully at the crystal matrices of GaOOH and α-Ga2O3 nanorods to form heterojunction nanocatalysts (CoFe2O4/GaOOH; CoFe2O4/Ga2O3). The heterojunction nanocatalysts were characterized using various analytical tools to confirm the expected modifications. The band gap of GaOOH (Eg = 4.50 eV) and α-Ga2O3 (Eg = 4.46 eV) are reduced in the formed heterojunction nanocatalysts CoFe2O4/GaOOH (Eg =2.56 eV) and CoFe2O4/Ga2O3 (Eg = 2.51 eV), respectively. Moreover, the XRD and HR-TEM analyses demonstrate the formation of heterojunction nanocatalysts composed of the lattice diffusion of Co and Fe of CoFe2O4 into the matrix of α-Ga2O3 nanorods with good crystallinity. The photocatalytic efficiency was assessed during solar light-driven photocatalyic oxidation of norflurazon in single treatments and also assisted by peroxymonosulfate addition. The experimental results indicate that ~ 98% of the norflurazon (NRF) is oxidized within 40 min of solar light irradiation in the presence of CoFe2O4/α-Ga2O3 heterojunction nanophotocatalyst, having higher photocatalytic efficiency than benchmarked TiO2 nanoparticles (Degussa P25). Moreover, the results also show that the addition of peroxymonosulfate (PMS) boosts the photocatalytic oxidation and achieving 99% NRF oxidation within 10 min of solar light irradiation by the generation of SO4•− and •OH radicals. The novel synthesized heterojunction nanophotocatalyst (CoFe2O4/α-Ga2O3) results to be highly stable after six consecutive operating cycles.

Engineering of oxygen vacancy as defect sites in silicates for removal of diverse organic pollutants and enhanced aromatic alcohol oxidation

Efficient charge separation of the generated excitonic pair upon light irradiation is a crucial step in determining the efficiency of photocatalytic activity. Oxygen vacancy sites are known to overcome poor charge segregation. Herein, a hydrothermal approach was utilized to synthesize oxygen vacancy rich Bi2SiO5 nanoparticles (BSO NPs) with superior charge separation. Halide anion incorporation resulted in generation of oxygen vacancy sites along with a preferential growth of monoclinic over tetragonal phase. This phase transformation is advantageous as the monoclinic phase shows enhanced photocatalytic activity compared to the tetragonal. The synergetic effect of halide ions and oxygen vacancy sites on the surface led to increased photocatalytic activity arising from (1) enhanced light absorption towards visible spectrum from ultraviolet, (2) reduced bandgap, (3) surge in charge migration, and (4) increased surface area of the BSO NPs. Oxygen vacancy rich halide incorporated Bi2SiO5 NPs showed up to 12 times improved photocatalytic rate over pristine towards toxic dye pollutants. Photocatalytic tetracycline degradation mechanism was also studied displaying up to 83% degradation within 180 min of solar light irradiation. In addition, the developed photocatalyst is efficient towards synthesis of benzaldehyde from benzyl alcohol with high yield up to 40% within 4 h.

Solvothermal synthesis of CTAB capped and SDS capped BiOCl photocatalysts for degradation of rhodamine B (RhB) dye and fluoroquinolone antibiotics

A solvothermal route for reparation of the BiOCl photocatalysts using CTAB or SDS capping agent has been demonstrated. The surfactant strongly influences the morphology, surface area and photoactivity of the photocatalyst. The CTAB capped BiOCl photocatalyst, with high specific surface area and high electron-hole pairs separation rate, shows efficiency of 82–98% toward photodegradation of ofloxacin (OFL), norfloxacin (NOR), ciprofloxacin (CIP) and Rhodamine B (RhB) pollutants. In the case of the SDS capped BiOCl photocatalyst, the complete photodegradation of RhB dye was reported. The enhanced efficiency is due to the existence of SDS comprising polar head, which afford excellent water solubility, and non-polar tail which can facilitate adsorption of pollutant molecule on the surface of the photocatalyst. The capped photocatalyst also shows complete photodegradation of the pollutants after 40 ​min of solar light irradiation with good structural stability after the third run. The results strongly indicated that the added surfactants play an important role in enhancement of the photocatalytic performance. This work demonstrates a promising potential of the BiOCl photocatalysts for environmental protection.

Facile and inexpensive synthesis of Ag doped ZnO/CNTs composite: Study on the efficient photocatalytic activity and photocatalytic mechanism

In present study, an effective photocatalytic activity for Reactive Black GR and metronidazole degradation was evaluated using microwave-assisted prepared Ag doped ZnO, ZnO/CNTs and Ag doped ZnO/CNTs composites as photocatalyst under visible and sunlight irradiation. The photocatalysts were extensively characterized using a variety of standard tools. The results of XRD and XPS analysis identified the presence of Ag in synthesized composites. The introduction of Ag into the lattice of ZnO deteriorated crystal growth with the reduction of crystallites size, suppressed electron-hole pair's rate and shift in the optical absorption response from UV to visible region due to its surface plasmon resonance effect. The presence of CNTs enhanced the specific surface area of the composites meanwhile content of hydroxyl oxygen at the surface reduced concurrently, that increased the surface hydroxyl groups in the framework of ZnO. Moreover, CNTs acted as electron sink to significantly reduce the photocorrosion of ZnO, consequently improving the photostability of the synthesized samples. An appropriate amount of Ag (2 wt%) and CNTs (2 wt%) (AZC1 composite) was measured to be an optimized composition in accordance with the highest efficiency of the photocatalytic activity. The photocatalytic activity of AZC1 composite for the degradation of Reactive Black GR was measured to be 100% within just 30 min of solar light irradiation and 120 min of visible light illumination, while the corresponding metronidazole degradation was achieved within 40 min of solar light irradiation and 120 min of visible light illumination. A photocatalytic mechanism was proposed to explain the increased photocatalytic performance of the synthesized photocatalysts. This work represents an effective strategy to enhance the photocatalytic activity of ZnO and provides information to synthesize facile, inexpensive and eco-friendly Ag doped ZnO/CNTs photocatalysts.

Resurrection of boron nitride in p-n type-II boron nitride/B-doped-g-C3N4 nanocomposite during solid-state Z-scheme charge transfer path for the degradation of tetracycline hydrochloride

Antibiotic contaminants have received much attention due to the increasing serious environmental concerns. In this work, for the first time, we have fabricated a series of significant type-II p-n heterostructure with Z-scheme charge transfer between p-type B-doped g-C3N4 with different proportion of n-type BN through a simple in-situ growth process. PXRD, FTIR, UV–Vis, FESEM, HRTEM and EIS analysis were applied for the detailed characterization of the as-prepared composites to study the crystal phase, structural features, optical and electrical properties. The photocatalytic behaviour of BN/BCN photocatalyst was investigated by the degradation of tetracycline hydrochloride under solar light illumination. Experimental results revealed that about 88.1% of TCH was degraded by the BN/BCN composite containing 4 wt% BN in the BN/BCN matrix, in 60 min of solar light irradiation. Reduction in recombination rate of photo generated electron-hole pair’s and enhanced visible light absorption ability is credited to the enhanced photocatalytic performance of BN/BCN composite. Trapping experiment for the scavenging agents has confirmed that superoxide (O2¯) and hydroxyl (OH) radicals are the main reactive species during the TCH degradation process. The high stability shown by the BN/BCN composite opens a new path for designing of significant BN based Z-scheme photocatalyst for prevention of environmental issues.

Hydrogen peroxide‐assisted photocatalysis under solar light irradiation: Interpretation of interaction effects between an active photocatalyst and H2O2

AbstractIn this work, the combination of H2O2 and an active visible‐light‐driven photocatalyst (Ag‐S/PEG/TiO2) was utilized under natural solar radiation for the degradation of 2‐nitrophenol (2‐NP), and interaction effects between the photocatalyst and hydrogen peroxide were analyzed. For this purpose, experiments were designed using the response surface methodology based on the central composite design. The resulting data was utilized to obtain a model for the prediction of response (the degradation efficiency) as a function of two independent factors (H2O2 concentration and the photocatalyst loading). The statistical analysis indicated that optimum values of each of the two independent factors decreased by increasing the other one and vice versa. Moreover, it was found that adding the optimal amount of H2O2 to the solution, which contained just the photocatalyst, can enhance the degradation significantly (up to 45 %). However, using higher concentrations of H2O2 may decrease the efficiency. The global optimum condition was found to be 545 ppm and 316 mM for Ag‐S/PEG/TiO2 loading and H2O2 concentration, respectively. In this condition, the degradation efficiency of 2‐NP reached 92.4 % after only 45 min of solar light irradiation.

Mixed-dimensional, three-level hierarchical nanostructures of silver and zinc oxide for fast photocatalytic degradation of multiple dyes

Three-level AgNWs/ZnO NRs/AgNPs hierarchical structures resembling nanoscale pine trees have been successfully synthesized using a three-step solution method. In particular, AgNPs were incorporated primarily for plasmonic light harvesting. The PL intensity of the hierarchical nanostructures was disclosed to drop by 89% at the most from the value of pure ZnO NRs, which indicated the remarkable retardation of carrier recombination. It is worth noting that the photocatalytic performance of the hierarchical nanostructures dominated over their counterparts such as pure ZnO NRs and AgNWs/ZnO NRs hybrid structures. Moreover, their photocatalytic efficiency remained high for a variety of organic dyes like methylene blue, methyl orange, and rhodamine B. The hierarchical nanostructures turned out to degrade 96.5% of dyes on average within a 30 min of solar light irradiation. In addition, they were also found to possess good recyclability. The overwhelming photocatalytic performance of the AgNWs/ZnO NRs/AgNPs hierarchical structures was discussed on the basis of fast electron transfer and surface plasmon resonance. The unique design and superb performance of the hierarchical nanostructures can offer a new possibility to step closer to the realization of ideal photocatalysts with high reactivity for a wide range of pollutants.

Study of solar photocatalytic degradation of Acesulfame K to limit the outpouring of artificial sweeteners

Abstract In this study, the photocatalytic degradation of an artificial sweetener, Acesulfame K (ACK), has been investigated with TiO2 photocatalyst using a solar simulator. Adsorption of ACK on TiO2 surface follows Freundlich adsorption isotherm in the pH range of 6–8 and shows an adsorption coefficient of 0.002 L/mg. Parametric studies for solar photocatalytic degradation are performed varying initial concentrations of ACK, photocatalyst dosage, and solar light intensity. Photocatalytic degradation rate of ACK gradually decreases with increasing initial concentration of ACK, and the rate follows pseudo first-order kinetics. The degradation rate of ACK gradually increases as the TiO2 dosage is increased and reaches maximum at 0.8–1.0 g/L. The rate constant for ACK degradation has been found to be directly proportional to light intensity, obeying a power law model. Complete degradation of ACK for 10–20 mg/L initial concentration is observed within the first 30 min of solar light irradiation of 100 mW/cm2 at pH 6. Complete mineralization of ACK can be achieved in 6 h with dissolved organic carbon (DOC) less than 1 mg/L. Complete mineralization of ACK and its by-products is successfully achieved with an apparent quantum yield of 0.02% at 1 sun thus making the process sustainable. This study manifests the efficacy of the solar photocatalytic process on degrading emerging pollutants like ACK where the use of artificial UV lamp has successfully been substituted by solar light, the most abundantly found sustainable source of energy in nature. Moreover, the process followed in this study is devoid of the use of any hazardous chemicals.

Investigation of 2-nitrophenol solar degradation in the simultaneous presence of K2S2O8 and H2O2: Using experimental design and artificial neural network

In this study, the interaction effect of K2S2O8 (PDS) and H2O2 (as two powerful oxidants) was investigated on the solar degradation of 2-nitrophenol (2-NF) in the two systems, i.e. absence and presence of Ag/S/TiO2 photocatalyst. Experiments were designed based on the central composite design, and two methods of response surface methodology (RSM) and artificial neural network (ANN) were developed for modeling of the systems. Concentrations of PDS and H2O2 were considered as independent variables and 2-NF degradation efficiency was selected as the response. It was revealed that the predictive capacity of ANN model is more than RSM model according to their corresponding R2, R2adj, RMS, MAE, and AAD values. Therefore, ANN model was utilized to analyze the effects of the independent variables. Moreover, it was found that, by increasing the amount of either PDS or H2O2, less amount of the other oxidant was required to reach the highest degradation efficiency which shows the contributive effect of the oxidants on each other. By adding Ag/S/TiO2 visible-light-sensitive photocatalyst to the solution containing PDS and H2O2, a significant enhancement in the 2-NF degradation efficiency was observed. Using an ANN-genetic algorithm (ANN-GA) approach, the values of 172.1 mg/l and 80.9 mg/l were respectively obtained as optimum concentrations for PDS and H2O2 (in the presence of the photocatalyst). Under this condition, 2-NF degradation efficiency was predicted to be 96% after only 45 min of solar light irradiation that is in a good agreement with the actual degradation efficiency of 97.1% obtained at the optimum concentrations. In addition, the relative importance of the independent variables was studied using Garson method and it was found that PDS had more impact on the response in comparison with H2O2.

Enhancement of 2-chlorophenol photocatalytic degradation in the presence Co2+-doped ZnO nanoparticles under direct solar radiation

The performance of Co2+-doped ZnO nanoparticles, prepared using the sol–gel method, for 2-chlorophenol degradation under direct solar radiation was investigated. Various parameters were investigated during the degradation process, namely solar intensity, Co2+ ion concentration, loading concentrations of Co2+-doped ZnO, and pH. The photocatalytic degradation efficiency increased when the initial concentration of 2-chlorophenol decreased; the optimum concentration was 50 mg/L under similar experimental conditions. Moreover, optimum values, established on a sunny day, were 0.75 wt% of Co2+, a 1 g/L loading concentration, and a pH of 6.0, respectively. The highest degradation efficiency observed was 95 %, after only 90 min of solar light irradiation. The mechanism of visible photocatalytic degradation using Co2+-doped ZnO was explained as a strong electronic interaction between Co2+, Co3+ and ZnO, and a promotion in the charge separation, which enhanced the degradation performance. The fragmentation of 2-chlorophenol under the optimal conditions was investigated using HPLC, comparing standards of all intermediate compounds. The pathway of the fragmentation was proposed as involving hydroxyhydroquinone, catechol, and phenol formation, which were then converted to non-toxic compounds such as oxalic acid and acetic acid with further decomposition to CO2 and H2O.