ZnO Dosage Research Articles

Zinc oxide application alleviates arsenic-mediated oxidative stress via physio-biochemical mechanism in rice.

Arsenic (As) pollution in cultivated soils poses a significant risk to the sustainable growth of agriculture and jeopardizes food security. However, the mechanisms underlying how zinc (Zn) regulates the toxic effects induced by As in plants remain poorly understood. Hence, this study aimed to explore the potential of ZnO as an effective and environmentally friendly amendment to alleviate As toxicity in rice, thereby addressing the significant risk posed by As pollution in cultivated soils. Through a hydroponic experiment, the study assessed the mitigating effects of different ZnO dosages (Zn5, 5mg L-1; Zn15, 15mg L-1; Zn30, 30mg L-1) on rice seedlings exposed to varying levels of As stress (As0, 0µM L-1; As25, 25µM L-1). The findings of the study demonstrate significant improvements in plant height and biomass (shoot and root), with a notable increase of 16-40% observed in the Zn15 treatment, and an even more substantial enhancement of 29-53% observed in the Zn30 treatment under As stress, compared to respective control treatment. Furthermore, in the Zn30 treatment, the shoot and root As contents substantially reduced by 47% and 63%, respectively, relative to the control treatment. The elevated Zn contents in shoots and roots enhanced antioxidant enzyme activities (POD, SOD, and CAT), and decreased MDA contents (13-25%) and H2O2 contents (11-27%), indicating the mitigation of oxidative stress. Moreover, the expression of antioxidant-related genes, OsSOD-Cu/Zn, OsCATA, OsCATB, and OsAPX1 was reduced when rice seedlings were exposed to As stress and significantly enhanced after Zn addition. Overall, the research suggests that ZnO application could effectively mitigate As uptake and toxicity in rice plants cultivated in As-contaminated soils, offering potential solutions for sustainable agriculture and food security.

Use of ZIF‐8 as vulcanization additive to optimize natural rubber composites to lower the amount of ZnO

AbstractZinc oxide (ZnO) is widely used as an activator in the vulcanization process of natural rubber. However, due to its poor compatibility with natural rubber, a large amount of ZnO needs to use, and the unreacted ZnO can precipitate in various ways, posing significant harm to aquatic organisms and microorganisms. Therefore, it is necessary to reduce the dosage of ZnO in order to minimize its environmental impact. In this study, we applied ZIF‐8, a zinc‐based metal–organic framework, as a vulcanization additive in natural rubber. and it was found that ZIF‐8 could promote the rubber vulcanization reaction by adsorbing sulfur, promoting sulfur ring‐opening, and providing different ligand interactions of Zn2+. Moreover, even at low usage levels of ZIF‐8, it effectively reduces the amount of ZnO while simultaneously improving the mechanical properties of the samples. This work provides an effective method to reduce the amount of ZnO without sacrificing the rubber properties and provides a new idea for the application of ZIF‐8 in rubber materials.Highlights ZIF‐8 enhances properties of natural rubber composites with low ZnO dosages. Revealing the reason why ZIF‐8 promotes the vulcanization of natural rubber. Investigation of the effect of ZIF‐8 on the vulcanization properties of natural rubber.

Tailoring ZnO nanorods for efficient photocatalytic production of H2O2 from water without sacrificial agents: A study on length optimization

In this study, we investigated the optimal length of zinc oxide nanorods (ZnO NRs) for the production of photocatalytic hydrogen peroxide (H2O2) using a hydrothermal method at 150 °C with reaction times ranging from 2 to 12 h. The study found that the size of the crystals increased when the reaction duration was extended, resulting in an increase in the size from 26 to 48 nm. SEM measurements indicated that ZnO exhibited longitudinal growth along the c-axis, increasing the nanorod length from 1 μm to 3.5 μm. The bandgaps of the ZnO NRs were between 3.21 and 3.25 eV. The optimal conditions for H2O2 production were identified to be 10 min of sonication and 15 min of UV illumination. The generation of H2O2 increased with the dosage of ZnO, ranging from 0.01 to 0.3 g/20 ml. The highest H2O2 production was attained by employing ZnO NRs at 1.6 μm in length with 49 mgL−1 Under UV irradiation and 28 mgL−1 under sonication irradiation. This study offers new perspectives for the design and production of H2O2 using ZnO NRs of a certain length, which may be beneficial for environmental remediation and energy generation.

Photocatalytic degradation of oxytetracycline using ZnO catalyst

AbstractIn the present study, the degradation of oxytetracycline (OTC) under ultraviolet (UV) light in the presence of ZnO catalyst was investigated, and optimum parameters for degradation efficiency were determined. Different pH values, ZnO dosages, reaction times, OTC concentrations, and UV lights were used in this study. The optimum conditions found were as follows: pH 4, ZnO 1 g L−1, reaction time 25 min, and OTC concentration 10 mg L−1. Degradation efficiency was 42.1%, 76%, 70.7%, and 61.7% for ZnO and photocatalytic (for UV‐A, UV‐B, and UV‐C) degradation at optimal conditions, respectively. The resulting products after the photocatalytic oxidation of OTC were determined in the study. To identify the toxicity of degradation products and OTC, the lowest LC 50 (50% lethal concentration) and EC 50 (50% effective concentration) values were found. The resulting ethanamine, 2‐(2,6‐dimethylphenoxy)‐N‐methyl‐ by‐products were observed to be more toxic than OTC. Furthermore, it was seen that isopropoxy carbamic acid, ethyl ester by‐products were formed, whose presence is environmentally risky for aquatic environments due to their low EC50 values.

Photocatalytic degradation process of antibiotic sulfamethoxazole by ZnO in aquatic systems: a dynamic kinetic model based on contributions of OH radical, oxygenated radical intermediates and dissolved oxygen

The photocatalytic degradation process of sulfamethoxazole (SMX) using ZnO in aquatic systems has been systematically studied by varying initial SMX concentration from 0 to 15 mgL−1 , ZnO dosage from 0 to 4 gL−1 and UV light intensity at the light source from 0 to 18 W(m-lamp length)−1 at natural pH. Almost complete degradations of SMX were achieved within 120 min for the initial SMX concentration ≤15 mgL−1 with ZnO dosage of 3 gL−1 and UV light intensity of 18 W(m-lamp length)−1. The photocatalytic degradation process was found to be interacted with the dissolved oxygen (DO) consumption. With oxygen supply through the gas-liquid free-surface, the DO concentration decreased significantly in the initial SMX degradation phase and increased asymptotically to the saturated DO concentration after achieving about 80% SMX degradation. The change in DO concentration was probably controlled by the oxygen consumption in the formation of oxygenated radical intermediates. A novel dynamic kinetic model based on the fundamental reactions of photocatalysis and the formation of oxygenated radical intermediates was developed. In the modeling the dynamic concentration profiles of OH radical and DO are considered. The dynamics of SMX degradation process by ZnO was simulated reasonably by the proposed model.

Efficient wastewater treatment in petroleum refineries: Hybrid electro-fenton and photocatalysis (UV/ZnO) process

In this study, a new hybrid system composed of a photo-catalysis (UV/ZnO) process combined with an electro-Fenton (EF) process equipped with a micro porous graphite air diffusion cathode (MPGADC) was used to treat petroleum refinery wastewater (PRW). The hybrid system was operated in a batch recycle mode and its performance was investigated and optimized using a response surface methodology (RSM). Three operating parameters affecting on the removal efficiency (RE%) of chemical oxygen demand (COD) were investigated including current density (2–10 mA/cm2), ZnO dosage (0.05–0.35 g/L), and Fe2+concentration (0.05–0.15 mM). Results showed that the optimum operating conditions can be achieved using a current density of 6.44 mA/cm2, with ZnO dosage of 0.35 g/L, and concentration of Fe2+ ions at 0.05 mM in which RE% of 90.15% was obtained with requiring a total electrical energy consumption (EECT) of 19.102KWh/m3. Furthermore, analysis of variance (ANOVA) exhibited a high value of determination coefficient (R2) close to 98.24% indicating a satisfactory fit between the obtained regression model and the experimental results. Moreover, ANOVA results revealed that current density has the most significant effect on RE% with a contribution of 52.41% followed by ZnO dosage and Fe2+ concentration both of them with a contribution of 11.64%. The comparison between the individual photo-catalysis process and hybrid process showed that RE% increases from 77.83% to 90.15% making an enhancement by 15.83% in RE% while EECT decreased from 27.171to 19.102KWh/m3 making a reduction by 29.7% in EECT. Hence, combining EF with photo-catalysis process improves the efficiency and reduced the required energy in comparison with the individual photo-catalysis process. Therefore, the combined process could be considered as an alternative, sustainable, green and cost-effective method for treatment of refinery wastewaters.

Photo(electro)catalytic Performance of ZnO‐Based Nanopowders Prepared through Pulse Alternating Current Electrosynthesis in Alkaline Earth Chloride Electrolytes

AbstractPhoto(electro)catalysis is a technology that allows abundant and clean solar energy to be harvested as an essential step to achieving sustainable development goals. However, controllable and economically viable synthesis of nanocatalysts is one of the key challenges that hinder the practical application of many important energy‐related photo(electro)catalytic reactions. In this study insights into the electrosynthesis of ZnO‐based materials using pulse alternating current as a green oxidant and the alkaline earth metal chloride aqueous solutions as electrolytes were provided. The effect of electrolyte on composition and structure of final products was demonstrated. ZnO photocatalyst prepared in BaCl2 exhibited different activity tendency in photoelectrocatalytic and photocatalytic systems showing the highest photocurrent (0.18 mA cm−2) for ZnO photoelectrode annealed at 300 °C and maximum rate constant for methylene blue dye photodegradation in the presence of ZnO particles annealed at 500 °C. Optimized ZnO nanopowder was further employed for the degradation of 2,4‐dinitrophenol pollutant in a custom‐designed flow photoreactor operating under low‐power UV. 2,4‐dinitrophenol was degraded to 90.1 % at ZnO dosage of 0.2 mg L−1 within 280 min of illumination. Overall, the optimization of pulse alternating current electrosynthesis and post‐annealing might be promising and sustainable approach to ZnO‐based nanopowders for environmental photo(electro)catalytic applications.

Taguchi L9 (34) Orthogonal Array Design for Photocatalytic Degradation of Methylene Blue Dye by Green ZnO Particles Biosynthesized by Chrysanthemum spp. Flower Extract

The pollution of synthetic dyes in wastewater exerts many negative impacts on the environment and human health. There is an increasing demand for the degradation of dyes, with an emphasis on photocatalysis. Here, we investigated the bio-mediated synthesis of ZnO using Chrysanthemum spp. flower extract and its utilization for the removal of methylene blue dye under sunlight irradiation. The bandgap energy of green ZnO nanoparticles was determined to be 3.0. The Taguchi L9 (34) orthogonal array design was applied to optimize the photocatalytic degradation of methylene blue dye by green ZnO particles. Four parameters, including the initial concentration (10–50 mg/L), ZnO dosage (0.33–1.0 mg), contact time (30–120 min), and pH (4–10) of the solution, were surveyed based on the Taguchi design. We found that the test result (99.0%) at 10 mg/L was almost equivalent to the predicted value (99.5%) of degradation efficiency. The reaction mechanisms shed light on the major role of reactive oxygen species (•O2−, •OH). More importantly, the green ZnO particles could be reused for at least five cycles and demonstrated high stability.

ZnO Promoted Persulfate Activation in Discharge Plasma System for Ofloxacin Degradation

This paper aims to investigate the promotion of persulfate (PS) activation by ZnO in discharge plasma systems for the degradation of ofloxacin (OFX). Scanning electron microscopy and transmission electron microscopy showed that ZnO nanoparticles were successfully prepared by a hydrothermal method. With an increase in the PS dosage, the removal efficiency of OFX first increased and then decreased. With an increase in the ZnO dosage, the removal efficiency of OFX showed a similar trend. Under the optimum 595 mg/L PS dosage and 295 mg/L ZnO dosage, the removal efficiency of OFX by plasma, plasma/ZnO, and plasma/ZnO/PS systems reached 53.6%, 82.8%, and 98.9%, respectively. Increasing the input power was beneficial to the degradation of OFX. ESR results showed that the addition of ZnO could further stimulate PS to produce more ·OH and ·SO4− than that of plasma alone. The capture agent experiment proved that ·OH, ·SO4−, ·O2−, and 1O2 all participated in the degradation of OFX. A total organic carbon (TOC) removal of 49.6% was obtained in the plasma/ZnO/PS system. Based on liquid chromatography-mass spectrometry (LC-MS) and the Toxicity Estimation Software Tool (TEST), degradation pathways and toxicity were analyzed. Compared to other technologies, it can be concluded that the plasma/ZnO/PS system is a promising technology for pollutant remediation.

Zinc oxide in alkali-activated slag (AAS): retardation mechanism, reaction kinetics and immobilization

The relatively fast setting of alkali-activated slag (AAS) greatly restricts its wide application. ZnO can serve as the retardant for AAS. However, the role of ZnO in AAS is not well understood. This paper investigates the retardation mechanism of ZnO in the AAS system and the effects of ZnO on the reaction and performance of AAS. Results showed that a ZnO dosage of 2 wt% prolonged the setting of AAS paste by 72 min and inhibited the growth of C-(A)-S-H gels within the first 6 h of the reaction. The retardation of ZnO in AAS could be attributed to the ‘nucleation inhibition’, in which Zn2+ inhibits the generation of calcium hydroxide precipitation owing to the preferential incorporation of Ca in the calcium zincate (CZ) phase, thus reducing the nucleation sites and slowing down C-(A)-S-H gels growth, until all Zn ions are transformed into CZ phase or bonded in the AAS framework. ZnO slightly reduced the compressive strength and reaction extent of AAS, and was immobilized in AAS through various physicochemical approaches. This study provides a new look into the interaction between ZnO and AAS systems.

Knowledge extraction of sonophotocatalytic treatment for acid blue 113 dye removal by artificial neural networks

Removing decolorizing acid blue 113 (AB113) dye from textile wastewater is challenging due to its high stability and resistance to removal. In this study, we used an artificial neural network (ANN) model to estimate the effect of five different variables on AB113 dye removal in the sonophotocatalytic process. The five variables considered were reaction time (5–25 min), pH (3–11), ZnO dosage (0.2–1.0 g/L), ultrasonic power (100–300 W/L), and persulphate dosage (0.2–3 mmol/L). The most effective model had a 5-7-1 architecture, with an average deviation of 0.44 and R2 of 0.99. A sensitivity analysis was used to analyze the impact of different process variables on removal efficiency and to identify the most effective variable settings for maximum dye removal. Then, an imaginary sonophotocatalytic system was created to measure the quantitative impact of other process parameters on AB113 dye removal. The optimum process parameters for maximum AB 113 removal were identified as 6.2 pH, 25 min reaction time, 300 W/L ultrasonic power, 1.0 g/L ZnO dosage, and 2.54 mmol/L persulfate dosage. The model created was able to identify trends in dye removal and can contribute to future experiments.

Understanding the influence of anti‐reversion agent and metal oxide dose on natural rubber–carbon black system

AbstractSulfidic linkages that are formed during the vulcanization process of natural rubber (NR) are unstable at a higher temperature and can be reversed into conjugated diene. To overcome such issue and to build a compound that is hostile to inversion and with increasing service life, anti‐reversion agent (ARA), for example, N,N′‐4,4′‐diphenylmethyene bismaleimide (BMDM), is added into the formulation. This work explains the conjugation reaction mechanism of conjugated diene and BMDM by means of gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy. The first phase of this study is associated with the change in ARA dosage keeping ZnO dosage the same. It is observed that 5 phr of BMDM and 2 phr ZnO combination (ARA4) shows lowest reversion at 160°C. The modulus value at 300% elongation increased 12% by the incorporation of BMDM as compared to the compound of no BMDM (ARA1). The second part is all about keeping BMDM dosage the same at 5 phr level and varying ZnO phr by 3, 4, and 5. From the overall results, it is observed that at a suitable dosage of BMDM and ZnO (5 phr BMDM and 3 phr ZnO combination [ARA5]), least reversion can be achieved and vulcanizates containing optimized BMDM and ZnO show better retention properties after aerobic aging as compared to ARA1.

Optimization of the petroleum wastewater treatment process using TiO2/Zn photocatalyst

The present study was conducted to investigate the optimum conditions in a laboratory work for the real petroleum wastewater treatment plant using both new methods (TiO2/ZnO/Fenton/Solar and TiO2/ZnO/Air/Solar) to remove Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) from the real petroleum wastewater from the Sohar oil refinery (SOR). Maximum treatment efficiency was obtained by the TiO2/ZnO/air/Solar process. The ZnO dosage of 54 g/L and TiO2 dosage 50 g/L were required for removing 74% of COD and 99% of TOC under optimal conditions. The solar photocatalyst of TiO2/ZnO/Fenton method was the most efficient in the neutral pH, therefore no need to adjust pH during this treatment. In acidic conditions, the solar photo-Fenton process was more efficient than the TiO2/ZnO/air process while it was less efficient than the TiO2/ZnO/air process in (pH>7). The Fe+2 and H2O2 concentration were the main factors to improve the efficiency of the TiO2/ZnO/Fenton/Solar process while pH and the TiO2 dosage were the main factors for the TiO2/ZnO/air/Solar process. The estimated cost of treatment for the TiO2/ZnO/air process was 9 $/m3 while it was 8 $/m3 by the TiO2/ZnO/Fenton process. The final expected effluent concentrations met the acceptable levels of COD and TOC set by the Wastewater Discharge Standard of Oman.

Optimisation and kinetic modelling of atenolol degradation by ZnO under solar irradiation

ABSTRACT The aim of this study is to investigate the atenolol (ATL) degradation in aqueous suspension using commercial ZnO photocatalysts under solar irradiation. Effects of various operating parameters such as the ZnO dosage (0.025 to 0.075 g L−1), as well as pH ranges (3–12), and the ATL concentration (5–30 mg L−1) were also studied in a batch system. Results show that alkaline medium favoured the photocatalytic degradation of ATL (pH~7) and the best value of ZnO dosage occurred in 0.075 g L−1. Also, the removal rate increased with increasing ATL concentration. Kinetic data indicated that the photocatalytic kinetics followed the second-order model at high concentration of ATL, third-order model at low concentration, and first order model when adjusted pH. The second-order rate constant (k2) increases from 0.064 to 0.13 L mg−1 mn−1 when ZnO dosage increases from 0.025 to 0.2 g L,−1 respectively. As well, the pH rises from 3 to 7 the first-order rate constant (k1) increases from 0.35 to 1.56 mn−1. Then, at pH = 12 the rate constant (k1) decreases to 0.74 mn−1. The biodegradability, based on the BOD5 to COD ratio, increased with the increased photocatalysis time.

Free-radical scavenging activity properties of ZnO sub-micron particles: size effect and kinetics

ZnO particles were synthesized to evaluate the free radical scavenging activity properties of the particles as a function of the particle size. To obtain different particle diameters, the product was heat-treated at 600 °C for 2, 72, and 168 h to promote particle growth, obtaining a d50 of 132, 275, and 403 nm, respectively. The free radical scavenging activity was estimated by a 2,2 diphenyl-1-picrylhydrazyl (DPPH) assay, under UV irradiation. The kinetics of the scavenging reaction was monitored for the three different sizes and four ZnO particle concentrations at different reaction times; we found increases at lower particles size, and a relatively low ZnO dosage of 200 μg mL−1. The results showed that the reaction probably presented a pseudo-first-order kinetics model, with Ea = 3.2 kcal mol−1. Finally, we calculated the EC50 for the 132-μm particles to be 97.65 μg/mL.

Solar nanophotocatalytic pretreatment of seawater: process optimization and performance evaluation using response surface methodology and genetic algorithm

In reverse osmosis seawater treatment process, membrane fouling can be mitigated by degrading organic pollutants present in the feed seawater. The present study evaluates the effectiveness of employing solar photocatalysis using TiO2/ZnO/H2O2 to pretreat reverse osmosis (RO) feed seawater under solar irradiation. Process optimisation and performance evaluation were undertaken using response surface methodology-desirability function and RSM integrated with genetic algorithm (RSM-GA). Statistical analysis was performed to determine the interactive relationships and main effects of input factors such as TiO2 dosage, H2O2 dosage, pH, reaction time and ZnO dosage. The performance evaluation was determined in terms of percentage removal of total organic carbon (TOC) and chemical oxygen demand (COD). The obtained optimum values using RSM-GA evaluation for TOC and COD removal were found to be 76.5% and 63.9%, respectively. The predicted RSM-GA results correspond well with the experimental results (TOC removal = 73.3%, COD removal = 61.2%). Utilization of renewable solar energy coupled with optimum utilisation of nanophotocatalysts enables this technique to be a unique treatment process for RO pretreatment of seawater and membrane fouling mitigation.

Facile Synthesis of Porous ZnO Nanoparticles Efficient for Photocatalytic Degradation of Biomass-Derived Bisphenol A Under Simulated Sunlight Irradiation.

Bisphenol A (BPA) produced from biomass is a typical endocrine disrupting compound that is carcinogenic and genotoxic and can be accumulated in water due to its extensive use and difficult degradation. In this study, the porous ZnO photocatalyst with core-shell structure and large surface area was successfully developed for the efficient photocatalytic degradation of BPA. The various effects of calcination temperatures, BPA concentrations, ZnO dosages, pH and inorganic ions on the degradation performance were systemically studied. The results showed that 99% degradation of BPA was achieved in 1 h using the porous ZnO calcined at 550°C under the conditions of 30 mg/L BPA, 1 g/L ZnO, and pH of 6.5. Besides, the inhibition effects of anions for the photocatalytic removal of BPA decreased in the order of H2 > > > Cl−, while the cations K+, Ca2+, and Na+ had little effect on the photocatalytic degradation of BPA. The results of scavenging experiments showed that h+, ·, and e− played the key role in the photocatalytic degradation process. Finally, the main pathways of BPA degradation were proposed based on ten intermediates found in the degradation process. This work may provide a good guideline to degrade various endocrine disrupting compounds in wastewater treatment.

Modelling of cefixime (CFIX) removal using photocatalyst/UV/polyurethane by response surface methodology (RSM): optimisation and kinetic study

ABSTRACT The present study investigated the cefixime removal from aqueous solution using TiO2 and ZnO photocatalyst immobilised at polyurethane (PU) as well-asoptimized the effective parameters using response surface methodology (RSM). In this study, firstly, the polyurethane was synthesised and then photocatalysts were incorporated into the polyurethane. The experimental design was used to first determine the concentration of effective variables (pH, initial cefixime, catalyst dosage, and reaction time) and then optimize the independent variables based on the response (cefixime removal efficiency). The characteristics of photocatalyst were determined through scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The optimum variables for cefixime removal efficiency were pH of 4.80, catalyst dosage of 2.60 g/m2; initial cefixime concentration of 25.90 mg/L, and reaction time of 85 min for TiO2/ultraviolet (UV)/polyurethane (TiO2/UV/PU) process. In addition, the optimum conditions for the ZnO/ultraviolet/polyurethane (ZnO/UV/PU) process for pH of the solution, the dosage of ZnO, CFIX concentration, and reaction time were found to be6.70, 2.40 g/m2, 25 mg/L, and 89 min, respectively. The results of the kinetic model showed that experimental values were best fitted with the first-order model. Also, the results of a scavenger study represented that degradation of antibiotics and the generation of free radicals of hydroxide play an important role in the cefixime removal. Therefore, it is demonstrated that the CFIX antibiotic should significantly be removed from the aqueous solution using a photocatalyst/ultraviolet/polyurethane process.

Photocatalytic degradation of dissolved organic matter under ZnO-catalyzed artificial sunlight irradiation\xa0system

This study investigates the photocatalytic degradation of dissolved organic matter (DOM) under ZnO-assisted artificial sunlight system at various conditions (ZnO dosage, pH, and the presence of Cl−, SO42−, and HCO3−). The results show that the degradation of DOM follows a pseudo-first-order kinetics. Fluorescence excitation–emission matrices coupled with parallel factor (EEM-PARAFAC) analysis decomposes DOM into two fluorophores (C1 and C2). The total removals and photodegradation rates calculated with DOC, UV254, and the Fmax of C1 are similar, increasing with higher ZnO dosages and being highest in pH 7 and lowest in pH 4. ZnO dosage has a similar effect on DOM degradation when assessed using C2, as with C1, but pH effect is not consistent. As for the anions, HCO3− shows the strongest inhibition for DOC, UV254 and C1 while Cl− has the strongest facilitation effect for C2. The total removal and photodegradation rates calculated with the Fmax of C1 and C2 are higher than those calculated using DOC and UV254. This study demonstrates that the successful application of EEM-PARAFAC analysis in addition to traditional parameters can provide further insight into the photocatalytic degradation mechanisms associated with DOM in conjunction with a ZnO catalyst under artificial sunlight.

Mechanistic and kinetic insights of synergistic mineralization of ofloxacin using a sono-photo hybrid process

The present study reports an ultrasound-photocatalysis based hybrid method for effective degradation/mineralization of a bio-recalcitrant pharmaceutical pollutant, namely ofloxacin (OFLX). To understand the role of different techniques, individual and various combined ultrasound and ultraviolet along with H2O2, TiO2, and ZnO photo-catalyst were investigated in different protocols to understand synergistic effects and mechanistic insight of the mineralization process. Photocatalysts were characterized by FTIR, FE-SEM, TEM, EDX, BET, and EIS analysis. A significant synergistic index of 3.1 for mineralization of OFLX was obtained during the combined US/UV/H2O2/ZnO method due to higher oxidizing (OH) radical formation as compared to other binary and ternary hybrid methods. OFLX degradation and total organic carbon removal were 94.2% and 45.1%, respectively, using US/UV/H2O2/ZnO method at operating condition of H2O2/OFLX stoichiometric molar ratio = 5, ZnO dosage = 0.40 g L−1, 40 kHz ultrasonic frequency, 125 W UV power, reaction time of 120 min and pH 6.3 (natural pH). Kinetics of the degradation was well-represented by the power-law kinetic model with an order of reaction being 2.2 and 1.9 for US + UV + H2O2 + TiO2 and US + UV + H2O2 + ZnO, respectively. Besides, specific energy consumption (SEC), electrical energy per order (EEO), and the operating cost (OC) of each method employed was determined. A detailed OFLX degradation pathway has been suggested, and possible reasons for synergy are identified and discussed.