Removal of residual pesticides in vegetables using ozone microbubbles

An improved process for removal and recovery of heavy petroleum from solids using a ferrate-based hybrid oxidant

Persulfate oxidants are widely used in soil remediation and wastewater treatment but perform poorly in degrading polycyclic aromatic hydrocarbons (PAHs), especially heavy fractions in solids. Herein, we propose the utilization of a green peroxymonosulfate-ferrate-FeS (PFI) oxidant as a promising process aid for remediating soils contaminated with heavy petroleum components, including asphaltenes and resins. The PFI oxidant could degrade heavy petroleum fractions because of dual activation of the peroxymonosulfate and ferrate by FeS at ambient conditions. Nevertheless, when dealing with soil with high oil content (>10%), the degradation efficiency remains limited (<30%) regardless of the quantity of oxidants employed. Surface elemental analysis shows that a coating of secondary products (Fe(OH)3, Fe2O3) on the surface and in pores of the soil-pollutant matrix explains the failure of oxidation and inefficient use of oxidant. To address this issue, a strategy of pre-solvent extraction-oxidation hybrid process with sequent acidic washing is proposed, where dichloromethane serves as the solvent, and PFI acts as the oxidant. In this system over 90% of the oil could be recovered with an oxidation efficiency of 80% by alleviating the problem of iron oxide coating the matrix surface. The oxidant consumption is also reduced to 70 wt% of the sludge. The PFI oxidant is found to exhibit excellent universality in treating oily sludge with low petroleum content (<2%), reducing the petroleum content in the residue to less than 0.3 wt% (meeting the national standards). The degradation of low oil content sludge by the PFI oxidant followed pseudo first-order kinetics. These findings not only elucidate the failure of PFI oxidation for high oil content oily sludge and identify its potential engineering application range, but also offer a practical strategy for processing petroleum-contaminated soil with varying oil contents through wet oxidation.

Key factors impacting treatment efficiency in actual copper mineral processing wastewater by ozonation

Ozone advanced oxidation has been widely used in water treatment, but little research has been reported on the application of ozone to difficult-to-degrade mineral wastewater. In this paper, the effect of ozonation application in the treatment of copper mineral processing wastewater, which is difficult to be effectively treated by traditional processes due to its complex composition, was investigated. The effects of ozonation time, ozone concentration, temperature and pH on the degradation of organic compounds in the wastewater by ozonation were researched. It was found that the chemical oxygen demand (COD) of the wastewater could be reduced by 83.02% by ozonation under optimal treatment conditions. In addition, the mechanism of ozone degradation of the difficult-to-degrade wastewater was studied, and the reasons for the fluctuating variations of COD and ammonia nitrogen during ozonation treatment were explained.

Application of Near Infrared Spectroscopy to Monitor the Quality Change of Sour Cherry Stored under Modified Atmosphere Conditions

Determining and applying ‘good’ postharvest and quality control practices for otherwise highly sensitive fruits, such as sour cherry, is critical, as they serve as excellent media for a wide variety of microbial contaminants. The objective of this research was to report two series of experiments on the modified atmosphere storage (MAP) of sour cherries (Prunus cerasus L. var. Kántorjánosi, Újfehértói fürtös). Firstly, the significant effect of different washing pre-treatments on various quality indices was examined (i.e., headspace gas composition, weight loss, decay rate, color, firmness, soluble solid content, total plate count) in MAP-packed fruits. Subsequently, the applicability of near infrared (NIR) spectroscopy combined with chemometrics was investigated to detect the effect of various storage conditions (packed as control or MAP, stored at 3 or 5 °C) on sour cherries of different perceived ripeness. Significant differences were found for oxygen concentration when two perforations were applied on the packages of ‘Kántorjánosi’ (p < 0.01); weight loss when ‘Kánorjánosi’ (p < 0.001) and ‘Újfehértói fürtös’ (p < 0.01) were packed in MAP; SSC when ‘Újfehértói fürtös’ samples were ozone-treated (p < 0.05); and total plate count when ‘Kántorjánosi’ samples were ozone-treated (p < 0.01). The difference spectra reflected the high variability in the samples, and the detectable effects of different packaging. Based on the investigations with the soft independent modelling of class analogies (SIMCA), different packaging and storage resulted in significant differences in most of the cases even on the first storage day, which in many cases increased by the end of storage. The soft independent modelling of class analogies proved to be suitable for classification with apparent error rates between 0 and 0.5 during prediction regardless of ripeness. The research findings suggest the further correlation of NIR spectroscopic and reference parameters to support postharvest handling and fast quality control.

Degradation of malathion and carbosulfan by ozone water and analysis of their by-products

BACKGROUND

Treatment by ozone water is an emerging technology for the degradation of pesticide residues in vegetables. The ozone dissolved in water generates hydroxyl radicals (^· OH), which are highly effective in decomposing organic substances, such as malathion and carbosulfan.

RESULTS

We found that washing pak choi with 2.0 mg L^-1 ozone water for 30 min resulted in 58.3% and 38.2% degradation of the malathion and carbosulfan contents respectively, and the degradation rates of these pure pesticides were 83.0% and 66.3% respectively. In addition, the 'first + first'-order reaction kinetic model was found to predict the trend in the pesticide content during ozone water treatment. Based on investigations by gas chromatography-mass spectrometry combined with the structures of the pesticides, the by-products generated were identified. More specifically, the ozonation-based degradation of carbosulfan generated carbofuran and benzofuranol, whereas malathion produced succinic acid and phosphoric acid. Although some new harmful compounds were formed during degradation of the parent pesticides, these were only present in trace quantities and were transient intermediates that eventually disappeared during the reaction.

CONCLUSION

Our results, therefore, indicate that ozone water treatment technology for pesticide residue degradation is worthy of popularization and application. © 2022 Society of Chemical Industry.

Nanobubble Technology Enhanced Ozonation Process for Ammonia Removal

Ozone (O3) has been widely used for water and wastewater treatment due to its strong oxidation ability, however, the utilization efficiency of O3 is constrained by its low solubility and short half-life during the treatment process. Thereby, an integrated approach using novel nanobubble technology and ozone oxidation method was studied in order to enhance the ozonization of ammonia. Artificial wastewater (AW) with an initial concentration of 1600 mg/L ammonia was used in this study. In the ozone-nanobubble treatment group, the concentration of nano-sized bubbles was 2.2 × 107 particles/mL, and the bubbles with <200 nm diameter were 14 times higher than those in the ozone-macrobubble treatment control group. Ozone aeration was operated for 5 min in both nanobubble treatment and control groups, however, the sampling and measurement were conducted for 30 min to compare the utilization of O3 for ammonia oxidation. H+ was the by-product of the ammonia ozonation process, thus the pH decreased from 8 to 7 and 7.5 in nanobubble treatment and control groups, respectively, after 30 min of operation. The fast removal of ammonia was observed in both systems in the first 10 min, where the concentration of ammonia decreased from 1600 mg/L to 835 and 1110 mg/L in nanobubble treatment and control groups, respectively. In the nanobubble treatment group, ammonia concentrations kept the fast-decreasing trend and reached the final removal performance of 82.5% at the end of the experiment, which was significantly higher than that (44.2%) in the control group. Moreover, the first-order kinetic model could be used to describe the removal processes and revealed a significantly higher kinetic rate constant (0.064 min−1) compared with that (0.017 min−1) in the control group. With these results, our study highlights the viability of the proposed integrated approach to enhance the ozonation of a high level of ammonia in contaminated water.

Utilizing Plackett-Burman design and response surface analysis to optimize ultrasonic cleaning of pesticide residues from rape

BACKGROUND

Pesticide residues in fruits and vegetables threaten food safety. Cleaning before eating is a usual way to remove pesticide residues, so it is very important to find the most efficient cleaning conditions for public health. However, many previous cleaning studies only focused on a single variable which required a large amount of time manpower and material resources. Plackett-Burman design (PBD) and response surface methodology can avoid the earlier-mentioned problems and have potential in studying the influence and interaction of multiple factors. In this study, the effect of five factors on the removal of triadimefon and boscalid from rape by ultrasonic washing was evaluated through PBD: pH of water, ultrasonic cleaning time, water temperature, initial residual concentration and volume of water.

RESULTS

Temperature had a significant effect on the rate of triadimefon removal while the other four factors impacted boscalid removal greatly. A higher temperature was better for the removal rate of triadimefon. Under alkaline environment, when initial residual concentration and cleaning time increased with decreasing water volume, the removal rate of boscalid increased. Furthermore, the interactions among factors were obtained. The regression coefficients of fitting equations about triadimefon and boscalid were 0.9657 and 0.9738, respectively.

CONCLUSION

Changing pH of water, cleaning time, water volume and temperature during the washing process of rape through PBD designed experiments represents a valid strategy for improving the removal rate of two pesticides residue. This study provides a reference for ultrasonic cleaning conditions by a sink dishwasher, which has a positive effect on food safety. © 2021 Society of Chemical Industry.

Uptake, translocation and metabolism of imidacloprid loaded within fluorescent mesoporous silica nanoparticles in tomato (Solanum lycopersicum)

Fluorescence-labeling technology has been widely used for rapid detection of pesticides in agricultural production. However, there are few studies on the use of this technology to investigate pesticide uptake and transport in plants with fluorescent nanoparticle formulations. Here, we investigated uptake, transport, accumulation and metabolism of imidacloprid loaded in fluorescent mesoporous SiO₂ nanoparticles (Im@FL-MSNs) in tomato plants, and compared the results with the pesticide application in granular formulation. The results revealed that Im@FL-MSNs applied via root uptake and foliar spray both could effectively transport in tomato plants and carry the imidacloprid to plant tissues. Neither Im@FL-MSNs nor imidacloprid was detected inside of tomato fruits from root uptake or foliar spray applications. Compared with the foliar application of granular formulation, imidacloprid in Im@FL-MSNs demonstrated a higher concentration in leaves (1.14 ± 0.07 mg/kg > 1.08 ± 0.04 mg/kg, 1.13 ± 0.09 mg/kg > 1.11 ± 0.02 mg/kg), longer half-life (0.84 d < 1.31 d, 0.90 d < 1.36 d) and small numbers of metabolites formed. These results suggest that mesoporous silica nanoparticles could serve as an effective and efficient pesticide carrier for achieving the high use efficiency in plant protection. The information is also helpful to guide the pesticide applications and assess the risks associated with environmental quality and dietary consumption of vegetables.

Removal of pesticide residues from fresh vegetables by the coupled free chlorine/ultrasound process

Pesticide residue in vegetables has been considered as a serious food safety problem across the whole world. This study investigates a novel advanced oxidation process (AOP), namely the coupled free chlorine/ultrasound (FC/US) process for the removal of three typical pesticides from lettuce. The removal efficiencies of dimethoate (DMT), trichlorfon (TCF) and carbofuran (CBF) from lettuce reached 86.7%, 79.8% and 71.3%, respectively by the FC/US process. There existed a synergistic effect in the coupled FC/US process for pesticide removal and the synergistic factors reached 22.3%, 19.0% and 36.4% for DMT, TCF and CBF, respectively. Based on the analysis of mass balance of pesticides, the synergistic effect was probably attributed to the efficient oxidation of pesticides both in vegetables and in water by the generated free radicals and FC. The surface area and surface structure of vegetables strongly affected the removal of pesticides by FC/US. The removal efficiency of DMT increased from 80.9% to 88.1% as solution pH increased from 5.0 to 8.0, and then decreased to 84.1% when solution pH further increased to 9.0. When the ultrasonic frequency changed from 20 to 40 kHz, a remarkable improvement in pesticide removal by FC/US was observed. As the FC concentration increased from 0 to 15 mg L^-l, the removal efficiencies of pesticides increased firstly, and then became stagnant when the FC concentration further increased to 25 mg L^-l. The pesticide degradation pathways based on the identified intermediates were proposed. The total chlorophyll content was reduced by less than 5% after the FC/US process, indicating a negligible damage to the quality of vegetables. It suggests that the FC/US process is a promising AOP for pesticides removal from vegetables.

Global trends and characteristics of nano- and micro-bubbles research in environmental engineering over the past two decades: A scientometric analysis

The present study has two primary goals, the first goal is to investigate a bibliometric analysis and assess the trends to evaluate the global scientific production of microbubbles and nanobubbles from 2000 to 2020. The aim is to elucidate the cornucopia of benefits the two technologies (micro and nanobubbles) can offer in environmental sciences and environmental amelioration such as wastewater treatment, seed germination, separation processes, etc. The second goal is to explicate the reason behind every chart and trend through environmental engineering perspectives, which can confer value to each analysis. The data was acquired from the Web of Science and was delineated by VOS viewer software and GraphPad Prism. Considering 1034 publications in the area of micro-and nanobubbles, this study was conducted on four major aspects, including publication growth trend, countries contribution assessment, categories, journals and productivity, and keywords co-occurrence network analysis. This article revealed a notable growth in microbubbles and nanobubbles-related publications and a general growth trend in published articles in a 20-year period. China had the most significant collaboration with other countries, followed by the USA and Japan. The most dominant categories for microbubbles were environmental sciences and environmental engineering comprising 22.5% of the total publications, while multidisciplinary subjects such as nanotechnology and nanosciences (8%) were among the dominant categories for nanobubbles. Keyword's analysis results showed that microbubbles had reached the apex since their discovery. Consequently, they are being used mostly in water/wastewater treatment or environmental improvement. On the other hand, nanobubbles are still in their infancy, and their pervasive use is yet to be fully materialized. Most of the publications are still striving to understand the nature of nanobubbles and their stability; however, a critical analysis showed that during the past two years, the trend of using nanobubbles as a cost-effective and environmentally friendly approach has already begun.

The efficacy of washing strategies in the elimination of fungicide residues and the alterations on the quality of bell peppers

Food safety problems caused by pesticide residues in vegetables have become a top issue to raise public concern. In this study, bell peppers were grown in an experimental field and sprayed with two systemic (azoxystrobin and difenoconazole) and one contact (chlorothalonil) fungicides. Ozone (ozonated water and water continuously bubble with ozone) or conventional domestic (washing with distilled water, detergent, acetic acid, sodium bicarbonate, and sodium hypochlorite solutions) procedures were investigated to identify the most effective way to remove fungicide residues in bell peppers. The residues in the fruits and the washing solutions were determined by solid-liquid extraction with a low-temperature partition (SLE/LTP) and liquid-liquid extraction with a low-temperature partition (LLE/LTP), respectively, and analyzed by gas chromatography. Water continuously bubbled with ozone a concentration of 3 mg L^-1 was the most efficient treatment with removal of fungicides residues ranging from 67% to 87%. However, similar treatment at a lower concentration (1 mg L^-1) did not only efficiently removed fungicide residues (between 53% and 75%) but also preserving the quality of the fruit along a storage time of 13 days. Among the conventional solutions, sodium bicarbonate at 5% showed good efficiency removing between 60% and 81% of the fungicide residues from bell peppers, affecting the color quality of the fruit. Overall, the most affected physicochemical parameters in bell peppers after the treatments were weight loss, color, and vitamin C content.

Effect of ozone treatments on the removal of pesticide residues and postharvest quality in green pepper

The use of ozone as a tool in the storage of some horticultural produces is recommended for all steps from harvest to consumption. However, little is known about its effects on the removal of pesticides and postharvest physiology of fresh peppers. In the present study, the effects of ozone treatment on the removal of pesticides, storage life and quality of green peppers were investigated. Malathion, emamectin benzoate and acetamiprid were applied to pepper plants before harvest. Residue contents of peppers were measured at harvest time and after all treatments to determine the effect of ozone on the removal of pesticide residues. Peppers were subjected to four treatments: immersion in ozonated water (2 ppm) and only tap water (control) for 10 min, exposure to 2 ppm ozone gas in air and only air (control) for 45 min. Treated peppers were stored at 20 °C and 60 ± 5% relative humidity for 8 days, and some quality analyses were performed during storage. Ozonated water decreased, remarkable, pesticide residues in peppers compared to harvest time, but there was no meaningful changes in the samples treated with ozone in air. Ozone treatments suppressed clearly respiration rates and decreased weight losses of peppers compared to control groups. Ozonated water also maintained green color of peppers, with minimum change in h° values. Additionally, sensory quality of peppers was retarded by ozone application during storage. These findings revealed that ozone could be an alternative treatment to extend storage life of green peppers and remove pesticide residues.

Removal of tetramethylammonium hydroxide (TMAH) in semiconductor wastewater using the nano-ozone H2O2 process

In this study, we used a nano-ozone bubble to enhance the efficiency of the ozone/H₂O₂ process for the degradation of tetramethylammonium hydroxide (TMAH) found in semiconductor wastewater at high levels. The nano-ozone bubble significantly increased ozone mass transfer rate compared to that of the macro-ozone bubble. The half-life of nano-ozone bubbles was 23 times longer than that of the nano-ozone bubbles. Due to the high ozone mass transfer rate and its durability, the nano-ozone bubble increased the TMAH degradation rate compared to that of the macro-ozone. The addition of H₂O₂ significantly increased the TMAH degradation rate constant by OH production during the nano-ozone bubbles/H₂O₂ process. The optimum conditions for TMAH removal was 25 °C and pH 10. Within 90 min of the nano-ozone/H₂O₂ process, TOC removal was 65 % while 80 % of nitrogen was converted into nitrate (NO₃^-) with 95 % of TMAM removal. Decreases in acute (40-fold) and chronic (2-fold) toxicity were achieved after applying the nano-ozone/H₂O₂ process to TMAH containing wastewater. However, there was no significant chronic toxicity decrease during the nano-ozone/H₂O₂ process of TMAH.

Enhanced degradation of benzo[a]pyrene and toxicity reduction by microbubble ozonation

The microbubble technique has drawn great attention for efficient utilization of ozone for advance oxidation processes. Therefore, in this study, microbubble ozonation was investigated to evaluate the removal efficiency and toxicity reduction of benzo[a]pyrene. Compared with conventional macrobubble ozonation, microbubble ozonation produced higher concentrations of hydroxyl radicals and ozone in aqueous solutions, resulting in more efficient and persistent degradation of benzo[a]pyrene. Moreover, microbubble ozonation completely removed the acute toxicity of benzo[a]pyrene to Daphnia magna, whereas the toxicity reduction by macrobubble ozonation was not consistent owing possibly to toxic degradation products. These findings suggest that microbubble ozonation is a promising technique in terms of both chemical degradation and toxicity reduction of organic pollutants.

Evaluation of ozone technology as an alternative for degradation of free gossypol in cottonseed meal: a prospective study

Free gossypol is a toxic compound which naturally occurs in cottonseed and its derivates, affecting animal and possibly human health. Consequently, alternatives for gossypol destruction must be evaluated. This work evaluated the emerging technology of ozone processing for free gossypol destruction in cottonseed meal. Ozonation was carried out in the actual cottonseed meal and also a model system, designed to describe the involved mode of action. The model system consisted of glass pearls beads covered with free gossypol. Ozonation was performed in two ways: as a static process, i.e., without homogenising the sample after placing them in the reactor, and also homogenising it. Ozone degraded free gossypol in all the systems, but reaching different levels. Free gossypol reduction was higher in the model system than the cottonseed meal, and higher in the homogenised processing than the static one: cottonseed meal in homogenised (56%) and static (25%); model system homogenised (98%) and static (80%). The obtained differences suggest a problem of gas penetration in the solid particles, the effect of unexposed surfaces due to contact areas, and the reaction with other organic molecules further than the target. Ozonation is a promising technique for gossypol degradation in cottonseed meal, but additional strategies are needed to optimise the ozonation process and evaluate toxicological aspects.

Cold plasma for mitigating agrochemical and pesticide residue in food and water: Similarities with ozone and ultraviolet technologies

Pesticide and agrochemical residues in food and water are among hazardous chemicals that are associated with adverse health effects. Consequently, technologies for pesticide abatement in food and water remain in focus. Cold plasma is an emerging decontamination technology, that is being increasingly explored for the abatement of agrochemical and pesticide residue in food and water. In some cases, rapid and complete degradation of pesticide residues has come to light. Such promising results encourage exploring scale-up and commercialization. To achieve this, unraveling mechanisms involved in plasma decontamination and the nature of degradation products is needed. The present review identifies the mechanisms involved in plasma- assisted removal of pesticide residues from food and water, draws parallels with mechanism of ozone and ultraviolet technologies, investigates the chemistry of the intermediates and degradates, and identifies some future research needs. The review recognizes that mechanisms involved in plasma processes have overlapping similarities to those identified for ozone and ultraviolet light, involving oxidation by hydroxyl radical and photo-oxidation. The toxicity of intermediates and degradates in plasma processing have not received much attention. The safety aspects of end products form plasma led degradation of pesticides should be considered for practical exploitation. Identification of intermediates and degradation products, recognition of most potent plasma species, understanding the influence of co-existing entities, the energy efficiency of plasma reactors, and the process economics deserve research focus.

Non-thermal technologies: Solution for hazardous pesticides reduction in fruits and vegetables

Pesticide residues in the food above the maximum permissible residual limit (MRL) for safe consumption are a severe concern today. Though unit operations employed in domestic and industrial-scale processing of foods such as high-temperature decontamination and chemical washings degrade the agrochemicals and reduce toxicity, eliminating pesticides from the fresh and raw fruits and vegetables with the retainment of nutritional and organoleptic attributes demand appropriate non-thermal technologies. In this review, the potential of novel technologies like the pulsed electric field, high-pressure processing, irradiation, ozone, ultrasonication, and cold plasma for the reduction of pesticides in fruits and vegetables have been discussed in terms of their mechanism of action, playing around factors, advantages, and limitations. All the reviewed non-thermal technologies exhibited promising effects on pesticide degradation with their unique mechanism of action. Also, these techniques' potential to reduce the pesticides below MRLs and yield nontoxic metabolites in fruits and vegetables were analyzed. However, investigating the impact of the technologies on the nutritional and organoleptic quality profile of the commodities at the processing conditions causing noticeable pesticide reduction and the pathways of degradation reactions of various pesticides with each emerging technology should be studied to enhance the applicability.

Ozone treatment pak choi for the removal of malathion and carbosulfan pesticide residues

Since the beginning of the widespread use of pesticides, their removal from food has become a serious concern. In this study, the removal of residual pesticides (malathion and carbosulfan) from pak choi via treatment with ozonated water was investigated. Under the optimal treatment conditions, i.e., 2.0 mg/L ozonated water and a treatment duration of 15 min, malathion and carbosulfan were degraded by 53.0 and 33.0%, respectively, without any significant changes in color. Even though there was a slight decrease in vitamin C content (~7.9 mg/100 g) following the treatments, a significant decrease in the microbial colonies on the vegetables was observed. Additionally, the pesticide degradation mechanism showed good fitting with a "first + first"-order kinetic model (R² > 0.9), and the slope (k) indicated that ozone had a more prominent degradation effect on malathion than on carbosulfan. Therefore, this study provides a theoretical basis for controlling agricultural pesticide residues in household applications.

Microbubble ozonation of the antioxidant butylated hydroxytoluene: Degradation kinetics and toxicity reduction

Butylated hydroxytoluene (BHT) is recognized as a crucial pollutant in aquatic environments, but efforts to achieve its complete removal are without success. The aim of this study was to investigate the degradation efficiency of BHT in water using ozone microbubbles (OMB), coupled with toxicity change assessment at sub-lethal BHT concentrations (0.34, 0.45 and 0.90 μM) based on oxidative stress biomarkers in Daphnia magna. The efficiency of OMB on ozone gas mass transfer was assessed and the contribution of hydroxyl radicals (·OH) in the degradation of BHT was determined using p-chlorobenzoic acid (pCBA) probe compound and a ·OH radical scavenger (sodium carbonate, Na₂CO₃). The ozone gas mass transfer coefficient (k_La = 1.02 × 10^-2 s^-1) was much larger than the ozone self-decomposition rate (k_d = 8 × 10^-4 s^-1) implying little influence of self-decomposing ozone in the volumetric ozone transfer during OMB generation. Generally, OMB improved ozone gas mass transfer (1.3-19-fold) relative to conventional ozone techniques, while indirect reaction of BHT with ·OH was dominant (82%) over the direct reaction with molecular ozone. Addition of 15, 25 and 35 mM Na₂CO₃ reduced BHT degradation by 30, 50 and 65%, respectively, indicating the significance of ·OH in the degradation of BHT. Increase in initial BHT concentration correspondingly reduced its removal rate by OMB possibly due to increase in metabolites produced during ozonation. Post BHT treatment exposure tests recorded significant (p < 0.05) reductions in oxidative stress (according to enzyme activities changes) in D. magna compared to pretreatment tests, demonstrating the effectiveness of OMB in detoxification of BHT. Overall, the results of the study indicate that OMB is extremely efficient in complete degradation of BHT in water and, consequently, significantly (p < 0.05) reducing its toxicity.

Hyphenated dispersive solid- and liquid-phase microextraction technique based on a hydrophobic deep eutectic solvent: application for trace analysis of pesticides in fruit juices

BACKGROUND

Pesticides are extensively used worldwide to control plant pathogens and prevent agricultural product damage. However, they can pollute the environment and endanger human health. So far, a variety of sample preparation methods have been developed for the analysis of pesticide residues.

RESULTS

A hyphenated solid-liquid microextraction method based on a new adsorbent of magnetic graphene oxide functionalized by (3-glycidyloxypropyl)trimethoxysilane and a deep eutectic solvent (choline chloride/4-chlorophenol (1:2)) was developed for extraction/preconcentration of trace levels of pesticides. The sorbent was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. In-syringe magnetic dispersive solid-phase extraction in tandem with dispersive liquid-liquid microextraction followed by gas chromatography was applied for the analysis of the selected pesticides. The main parameters governing sample preparation efficiency, including adsorbent dosage, desorption conditions, pH, extraction time, deep eutectic solvent volume, and salt concentration, were investigated. The linear ranges were 0.024-500 μg L^-1 with 0.9971-0.9999 linearity factor (R² ). The limits of detection and quantification were 0.006-0.038 and 0.024-0.126 μg L^-1 , respectively. The relative standard deviations were 0.5-4.2% for intra-day analysis and 2.7-4.6% for inter-day analysis. Enrichment factors were in the range 210-540.

CONCLUSIONS

The method was successfully applied for the determination of malathion, heptachlor epoxide, endrin, dichlorodiphenyltrichloroethane, azinphos ethyl, cypermethrin, and deltamethrin in fruit juice samples (apple, pineapple, cherry, peach, and red and green grape juices) and the recoveries were within the range 71-115%. © 2020 Society of Chemical Industry.

Remediation of NAPL-contaminated porous media using micro-nano ozone bubbles: Bench-scale experiments

Aqueous solutions of micro-nano bubbles (MNBs) containing ozone gas were injected through a NAPL-contaminated glass bead column. The glass column (15 cm × 2.5 cm) was packed with glass beads: the first 12 cm was packed with coarse glass beads while much finer glass beads were used to pack the remaining 3.0 cm of the column. Decane was used as the representative NAPL, to which an oil-soluble fluorescence tracer was added. The fluorescence tracer was considered as a constituent of the NAPL that readily reacts with ozone. Air and ozone-containing oxygen were used to generate MNB solutions, and injected through the column. In addition, H₂O₂ was introduced to the O₃-containing MNB (O₃-MNB) solution to investigate the effect of hydroxyl free radicals on the NAPL removal. An ozone gas sparging experiment was also conducted for comparison. After 72 h of O₃-MNB application, a significant mass of n-decane (27.6% of the initial mass applied) was removed from the column. H₂O₂ injection into the column during O₃-MNB application was effective in increasing the n-decane mass removal by 22%, compared to the O₃-MNB experiment. The rate of NAPL removal during O₃-MNB flushing was significant, although slower than ozone sparging. During O₃-MNB application, fast decay of fluorescence was observed; whereas, during co-injection of H₂O₂ and O₃-MNB solutions, only a slight change in the fluorescence was observed. This indicates that oxidative degradation of NAPL during H₂O₂ and O₃-MNB injection takes place only at the NAPL-water interface due to the reactivity of hydroxyl free radical, whereas ozone diffusion into NAPL induced the decay of the fluorescence tracer in the bulk NAPL. The removal characteristics during MNB application and ozone gas sparging were investigated based on the analysis of NAPL using mass spectrophotometer. When O₃-MNB and H₂O₂ were co-injected, only n-decane was detected in the NAPL; while when O₃-MNB was used for flushing, oxidative products were found in the NAPL. More hydrophilic compounds were found in the NAPL after ozone sparging. This implies different removal mechanisms depending on the kind of oxidation agent, and the state of oxidizing fluid. Based on the findings in this study, the application of O₃-MNB could be a feasible option for cleaning up NAPL-contaminated aquifers.

Enhanced Degradation of Pharmaceutical Compounds by a Microbubble Ozonation Process: Effects of Temperature, pH, and Humic Acids

This study systematically investigated the feasibility of the microbubble ozonation process to degrade the 17α-ethinylestradiol, ibuprofen, and atenolol through the comparison with the millibubble ozonation process for elucidating the degradation behavior and mechanisms during the microbubble ozonation processes. The proportions of small microbubbles (diameter 1–25 μm) were increased with increasing the cavity pump frequency (40 Hz: 51.4%; 50 Hz: 57.5%; 60 Hz: 59.9%). The increased concentrations of O3 and OH radicals due to the higher specific area of O3 microbubbles compared to O3 millibubbles could facilitate their mass transfer at the gas–water interface. Furthermore, the elevated reactivity of O3 by increasing the temperature might improve the degradation of the pharmaceutical compounds, which was more pronounced for the microbubble ozonated waters than the millibubble ozonated waters. Although the degradation efficiency of the pharmaceutical compounds during the microbubble ozonation processes was significantly influenced by the existence of humic acids compared to the millibubble ozonation process, the increased solubilization rate of O3 and OH radicals by collapsing O3 microbubbles enhanced the degradation of the pharmaceutical compounds. Overall, these results clearly showed that the microbubble ozonation process could be an alternative option to conventional ozonation processes for the abatement of the pharmaceutical compounds.

Use of ozone and detergent for removal of pesticides and improving storage quality of tomato

The efficiencies of two conventional domestic procedures (immersion in pure water and detergent solution at 0.25 and 1%) and two treatments using ozone (immersion in water with bubbling O₃ and immersion in ozonated water, both at 1 and 3 mg L^-1) were evaluated for the removal of residues of the fungicides azoxystrobin, chlorothalonil and difenoconazole in tomatoes. The fungicides were sprayed on the fruits at the recommended concentration for the crop. The residues in the tomatoes and in the washing solutions were determined by extraction with low-temperature partition techniques and analysis by gas chromatography. More concentrated solutions were more effective in removing pesticide residues. The water bubbled with ozone at 3 mg L^-1 was the most efficient treatment for the removal of fungicides, reaching a reduction of 70-90% of the residues. However, the treatments with the lowest concentration of ozone had lower loss of fruit mass during storage.

Effect of ozone treatment on the phenylpropanoid biosynthesis of postharvest strawberries

Ozone treatment at a suitable concentration can improve the antioxidant capacity of postharvest fruits. However, few studies have examined the antioxidant bioactive compounds in ozone-treated postharvest strawberries, especially in relation to proteomics. In this study, the total phenol content (TPC), total flavonoid content (TFC), and total anthocyanin content (TAC) were used as the main antioxidant compound indicators and unlabeled proteomics was used to study the metabolism of phenylpropanoids in postharvest strawberries (Jingtaoxiang) treated with different concentrations of ozone (0, 1, 3, and 5 ppm) throughout the duration of storage. The results showed that the postharvest strawberries treated with 5 ppm ozone concentration exhibited improved accumulation of total phenols, flavonoids and anthocyanins in the antioxidant bioactive compounds, which was beneficial to the expression of phenylpropanoid metabolism-related proteins over the whole storage period compared with the other three groups. The results of proteomics were consistent with the changes in the key metabolites of phenylpropanoids, which indicated that ozone treatment at a suitable concentration aids the accumulation of TPC, TAC and TFC by promoting the key proteins associated with phenylpropanoid metabolism.

Intensifying ozonation treatment of municipal secondary effluent using a combination of microbubbles and ultraviolet irradiation

Ozonation treatment of municipal secondary effluent is complicated by the low solubility of ozone and inefficient production of hydroxyl free radicals from ozone decomposition. To resolve these problems, this study investigated methods for intensifying ozonation treatment, using a combination of microbubbles and ultraviolet (UV) irradiation (UV/MBO). The high efficiency of the method was illustrated by treating river water containing refractory components derived from secondary effluent in a wastewater treatment plant. The results showed that the ozone mass transfer coefficient in a microbubble system was an order of magnitude compared with a conventional macrobubble system at the initial stage. The amount of ·OH generated during the treatment was quantified using a fluorescent probe analysis. The amount of ·OH in the UV/MBO system was almost 2-6 times more than the amount found with conventional ozonation using macrobubbles (CO), CO with UV irradiation (UV/CO), and microbubble ozonation (MBO) units. The UV/MBO system achieved chemical oxygen demand (COD), UV₂₅₄, and UV₄₀₀ removal performance rates of up to 37.50%, 81.15%, and 94.74% respectively. These levels were 2-36% higher than those in other systems. The coupling UV/MBO treatment significantly reduced all five categories of substances according to EEM spectra and fluorescence regional integration. The distribution of fractions with different molecular weights (MW) was altered and the UV₂₅₄ of MW (< 500 Da) increased by 15.8%. The biodegradability of the water was significantly improved, as indicated by the TOC/UV₂₅₄. This is ascribed to the enhanced degradation of refractory organics in the water. The combination of the UV/microbubble technique with ozonation could provide an efficient approach for advanced wastewater treatment. Graphical abstract.

Comparison of Different Home/Commercial Washing Strategies for Ten Typical Pesticide Residue Removal Effects in Kumquat, Spinach and Cucumber

Home processing can reduce pesticide residues in agricultural products, and the common forms of treatment include washing, peeling, blanching, and cooking. In this study, the removal effects of tap water, micron calcium solution, alkaline electrolyzed water (AlEW), ozone water, active oxygen, and sodium bicarbonate on 10 typical pesticide residues in kumquat, cucumber, and spinach were investigated. The residue magnitudes were determined by chromatography–tandem mass spectrometry (GC-MS/MS, LC-MS/MS), combined with the QuEChERS pretreatment method. The model tests showed that the results of soaking and greenhouse were close. The removal effects of pesticide residues in kumquat and cucumber washing by alkaline electrolyzed water with a high pH value, micron calcium, and active oxygen solution were better than other washing solutions. The sodium bicarbonate solution, ozone water, and active oxygen solution were more effective in reducing pesticide residues in spinach than others. Active oxygen solution showed a better removal efficiency for the 10 pesticides than other treatments because of its alkalinity and oxidizability. Among the ten pesticides, pyrethroid pesticides had a higher removal rate. Additionally, chlorpyrifos were the most difficult to remove. For the majority of pesticides, the pesticide residue magnitudes showed a gradual reduction when increasing the washing time. The results indicated that alkaline solutions were effective for the reduction of pesticide residues when the washing time was longer than 15 min.

A Review on Ultrasonic Catalytic Microbubbles Ozonation Processes: Properties, Hydroxyl Radicals Generation Pathway and Potential in Application

Ozone-based advanced oxidant processes (AOPs) have attracted remarkable attention as an alternative and effective approach for mineralization of refractory organics to innocuous substances. Key issues for ozone-based AOPs mainly focused on how to enhance ozone mass transfer and improve the production of hydroxyl radicals. Unfortunately, great efforts have been made, though, the application of ozone-based AOPs still remained in the laboratory scale due to lack of understanding of mechanisms of these hybrid processes. Besides, obtaining the balance of economical-technical feasibility is a great challenge. Ultrasonic catalytic microbubbles ozonation could be considered as a promising method, despite that there are a few studies that addressed this potential technology. Therefore, in this review, summaries about ozone-based microbubbles process, ultrasonic catalytic ozonation process, and ultrasonic catalytic microbubbles ozonation process have been provided in order to give a novel prospective about these hybrid technologies. The main influential parameters, such as initial pH, ozone dosage, intake flow rate, operating temperature, bubble size distributions, ultrasonic frequency, ultrasonic power density, and natural water constituents have also been well discussed. We truly hope that this paper will bring convenience to researchers that are devoted in the field of application of ozone-based AOPs for mineralizing refractory organics in wastewater.

Dissolution enhancement and mathematical modeling of removal of residual trichloroethene in sands by ozonation during flushing with micro-nano-bubble solution

Soil flushing using micro-nano-sized bubbles (MNB) in water as the flushing solution was tested in laboratory sand columns for the cleanup of residual trichloroethene (TCE) non-aqueous-phase-liquid (NAPL). Experiments considering flushing with MNB as well as ozone MNB (OZMNB) in water to treat soils contaminated with residual TCE liquid were conducted to examine effects of ozone on dissolution enhancement. The degrees of residual TCE saturation in soils, ranging from 0.44% to 7.6%, were tested. During flushings, aqueous TCE concentrations at the column exit were monitored and TCE masses remained in the columns after flushing were determined. Experimental results between runs with MNB and OZMNB in water revealed that dissolution enhancement was dependent on residual saturation conditions, and the maximum enhancement was around 9%. Governing equations consisting of three coupled partial differential equations (PDEs) were developed to model the system, and high-order finite difference (HOFD) method was employed to solve these PDEs. From mathematical modeling of reactive mass transfer under low residual saturation conditions (0.44% and 1.9%), experimental data were simulated and important controlling mechanisms were identified. It was concluded that a specific parameter pertinent to NAPL-water interfacial area in the Sherwood number had to be modified to satisfactorily describe the dissolution of TCE in the presence of MNB in water.

Removal of diethyl phthalate from water by ozone microbubbles in a pilot plant

Ozone microbubbles (OMBs) were used to remove diethyl phthalate (DEP) from water in a pilot plant. The removal of DEP and the mineralization efficiency were investigated under various reaction conditions. The removal of DEP by OMBs was very effective at the high pH and high ozone generation rates. Almost complete mineralization of DEP could be achieved at the high pH. The contribution of OH was computed by using a hydroxyl radical scavenger (i.e. t-BuOH). In neutral and alkaline media, the reaction of DEP with OH dominated over its direct reaction with ozone. The overall oxidation reaction fitted a second-order kinetic model. The overall rate constant and the volumetric mass transfer coefficient of ozone slightly increased with increasing pH. The results indicate that the OMBs were efficient in terms of the reduction of concentration of DEP and its complete mineralization.

Degradation of bifenthrin and pirimiphos-methyl residues in stored wheat grains (Triticum aestivum L.) by ozonation

Pesticide insecticides are used on wheat grains in storage units but their efficiency is hindered by persistent residues in the grains. Therefore, this study aims to evaluate the effectiveness of ozone (O3) gas treatment on the degradation of residual bifenthrin and pirimiphos-methyl insecticides commonly used in storage wheat grains, as well as to evaluate degradation of their by-products. The residues of bifenthrin decreased after 180 min of exposure in a concentration of 60 μmol/mol (a 37.5 ± 7.4% reduction) with 20% moisture content and 0.9 water activity. On the other hand, under the same experimental conditions, the pirimiphos-methyl residues significantly decreased in the wheat grains (71.1 ± 8.6%) after 30 min of exposure. After O3 gas treatment, three by-products of pirimiphos-methyl (m/z=306.1) containing different molecular mass to charge ratios (m/z=278.1, 301.1 and 319.2) were identified by LC-MS. O3 is a strong oxidizer that has shown the potential to reduce pesticide residues in stored grain in order to ensure food quality and safety.

Fast adsorption and removal of 2-methyl-4-chlorophenoxy acetic acid from aqueous solution with amine functionalized zirconium metal–organic framework

An amino functionalized zirconium-based MOF named UiO-66-NH₂ was synthesized and explored as a novel adsorbent for the fast removal of 2-methyl-4-chlorophenoxy acetic acid (MCPA) in aqueous solution.

The use of ozone to extend the shelf-life and maintain quality of fresh produce

Fresh produce has been recognised as a healthy food, thus there is increasing consumer demand for fresh fruit and vegetables. The shelf-life of fresh produce, however, is relatively short and is limited by microbial contamination or visual, textural and nutritional quality loss. There are many methods to reduce/eliminate microorganisms present in food and ozone treatment is one of them. The use of ozone by the fresh produce industry is a good alternative to chemical treatments, e.g. the use of chlorine. The effectiveness of ozone as an antimicrobial agent has previously been reviewed and has been updated here, with the latest findings. The main focus of this review is on the effects of ozone on the fresh produce quality, defined by maintenance of texture, visual quality, taste and aroma, and nutritional content. Furthermore, ozone has been found to be efficient in reducing pesticide residues from the produce. The treatments that have the ability to reduce microbial contamination of the product without having an adverse effect on its visual, textural and nutritional quality can be recommended and subsequently incorporated into the supply chain. A good understanding of all the benefits and limitations related to the use of ozone is needed, and relevant information has been reviewed in this paper.

Effects of ultrasound combined with ozone on the degradation of organophosphorus pesticide residues on lettuce

Methamidophos (MDP) and dichlorvos (DDVP) are organophosphorous pesticides which are commonly used for pest control in agriculture to obtain better yields.

Recent developments in minimal processing: a tool to retain nutritional quality of food

The modernization during the last century resulted in urbanization coupled with modifications in lifestyles and dietary habits. In the same era, industrial developments made it easier to meet the requirements for processed foods. However, consumers are now interested in minimally processed foods owing to increase in their awareness to have fruits and vegetables with superior quality, and natural integrity with fewer additives. The food products deteriorate as a consequence of physiological aging, biochemical changes, high respiration rat,e and high ethylene production. These factors contribute substantially to discoloration, loss of firmness, development of off-flavors, acidification, and microbial spoilage. Simultaneously, food processors are using emerging approaches to process perishable commodities, along with enhanced nutritional and sensorial quality. The present review article is an effort to utilize the modern approaches to minimize the processing and deterioration. The techniques discussed in this paper include chlorination, ozonation, irradiation, photosensitization, edible coating, natural preservative use, high-pressure processing, microwave heating, ohmic heating, and hurdle technology. The consequences of these techniques on shelf-life stability, microbial safety, preservation of organoleptic and nutritional quality, and residue avoidance are the limelight of the paper. Moreover, the discussion has been made on the feasibility and operability of these techniques in modern-day processing.