Formation Of Toxic By-products Research Articles

Recent Developments and Challenges in the Application of Fungal Laccase for the Biodegradation of Textile Dye Pollutants

Abstract: According to the European Environment Agency, the textile industry is responsible for 20% of global water pollution due to dyeing and finishing products, thus facing severe environmental challenges. It is essential to design more biocompatible and sustainable treatment processes capable of removing dyes from industrial wastewater to fight this environmental hazard. Chemical industries must change traditional chemical-based concepts to more environmentally friendly and greener processes to remove pollutants, including dyes. Enzymatic bioremediation is a smart tool and a promising alternative for environmental pollutant degradation. The use of enzymes in dye decolourization makes the process a green and clean alternative to conventional chemical treatments. Moreover, enzymemediated biocatalysis decreases the formation of toxic by-products compared to chemical reactions. The most used enzyme for the decolourization of dyes is laccase. Laccase is a multicopper oxidase found in diverse organisms such as fungi. It promotes the oxidation of phenolic compounds and has a wide range of substrate specificity, making it a promising enzyme for removing different dyes used by the textile industry, including recalcitrant aromatic dyes. The present article gives a comprehensive revision of textile dye decolourization, its types, recent developments in laccase-mediated dye bioremediation technologies, the mechanism of biocatalysis, and their limitations and challenges. Emphasis on the chemical pathways of laccase reaction mechanisms for dye bioremediation processes is also provided. In addition, a brief overview of textile industries and the respective traditional treatment processes for textile wastewater is presented.

Integrated pathway mining and selection of an artificial CYP79-mediated bypass to improve benzylisoquinoline alkaloid biosynthesis

BackgroundComputational mining of useful enzymes and biosynthesis pathways is a powerful strategy for metabolic engineering. Through systematic exploration of all conceivable combinations of enzyme reactions, including both known compounds and those inferred from the chemical structures of established reactions, we can uncover previously undiscovered enzymatic processes. The application of the novel alternative pathways enables us to improve microbial bioproduction by bypassing or reinforcing metabolic bottlenecks. Benzylisoquinoline alkaloids (BIAs) are a diverse group of plant-derived compounds with important pharmaceutical properties. BIA biosynthesis has developed into a prime example of metabolic engineering and microbial bioproduction. The early bottleneck of BIA production in Escherichia coli consists of 3,4-dihydroxyphenylacetaldehyde (DHPAA) production and conversion to tetrahydropapaveroline (THP). Previous studies have selected monoamine oxidase (MAO) and DHPAA synthase (DHPAAS) to produce DHPAA from dopamine and oxygen; however, both of these enzymes produce toxic hydrogen peroxide as a byproduct.ResultsIn the current study, in silico pathway design is applied to relieve the bottleneck of DHPAA production in the synthetic BIA pathway. Specifically, the cytochrome P450 enzyme, tyrosine N-monooxygenase (CYP79), is identified to bypass the established MAO- and DHPAAS-mediated pathways in an alternative arylacetaldoxime route to DHPAA with a peroxide-independent mechanism. The application of this pathway is proposed to result in less formation of toxic byproducts, leading to improved production of reticuline (up to 60 mg/L at the flask scale) when compared with that from the conventional MAO pathway.ConclusionsThis study showed improved reticuline production using the bypass pathway predicted by the M-path computational platform. Reticuline production in E. coli exceeded that of the conventional MAO-mediated pathway. The study provides a clear example of the integration of pathway mining and enzyme design in creating artificial metabolic pathways and suggests further potential applications of this strategy in metabolic engineering.

Optimisation of treatment efficiency and effluent toxicity during carbamazepine degradation via electrochemical oxidation

The commercialisation of electrochemical advanced oxidation processes (eAOPs) as a method for removing recalcitrant pollutants from wastewater is currently limited due to the potential for the formation of toxic by-products. In this regard, this research comprised a comprehensive optimisation study aimed at finding a balance between minimising the toxicity effects observed via phytotoxicity assays and maximising the eAOP degradation efficiency under low energy requirements. To this end, carbamazepine (CBZ) was selected as the target pollutant in synthetic wastewater, and the operating conditions considered for optimisation were the nature of the anolyte (i.e., sulfate- or chloride-based), its concentration, and the current density applied. Together with the identification of the CBZ transformation products and their estimated toxicity based on the ECOSAR model, the optimum treatment was found to correspond to the degradation in 500 mg L−1 of a sulfate-based anolyte at a current density of 10 A m−2. These conditions led to the fewest and least toxic transformation products and favoured plant growth indices in phytotoxicity tests. Even if additional process improvements are required to reduce effluent toxicity, continuing such a multi-target optimisation approach can lead to innocuous electrochemical wastewater treatment.

Efficiently removing dissolved organic pollutants in landfill leachate concentrate using dual-anode Fe2+/HClO system: The significance of insolubilization based on oxidative coupling of organics

The strategy to mineralize dissolved organics for the decontamination of landfill leachate concentrate (LLC) is expensive. Because mineralization requires high stoichiometric ratio of oxidants (e.g., •OH) or electron transfer (i.e., energy) to the pollutant molecules. Whereas, transferring the dissolved organic pollutants into separable insoluble matters is an energy-saving strategy. Herein, we developed a dual-anode Fe2+/HClO system for removing dissolved organic pollutants in LLC through insolubilization based on oxidative coupling. In this system, the majority of dissolved organic pollutants were transferred into insoluble substances, which could be removed easily. As a result, 89.8 % of the dissolved organic carbon (DOC) in LLC was fast removed in 3 h with a low specific energy consumption (SEC, 4.0 kWh kg−1 COD and 17.6 kWh kg−1 DOC), and the formation of toxic by-products can be well controlled to total organic chlorine (TOCl) < 0.1 mg/L. The formation of insoluble substances was attributed to the oxidative coupling of organic small molecules into the macromolecular ones. This was evidenced by the generation of insoluble compounds with the larger molecular mass, and the formation of coupling or polymerization products of the model pollutant (guaiacol). The predominant mechanism was proposed that Fe(IV) was generated in the dual-anode Fe2+/HClO system, and Fe(IV) oxidized pollutants to produce organic radicals, then the organic radicals coupled and polymerized to form larger molecules and insoluble compounds. This work offers a novel electrochemical method for efficient removal of organic pollutants in LLC with minimal toxic by-products generated, and revealed the significance of oxidative coupling process in the electrochemical Fe2+/HClO system.

Identification and Mechanistic Analysis of Toxic Degradation Products in the Advanced Oxidation Pathways of Fluoroquinolone Antibiotics.

The degradation of fluoroquinolones (FQs) via advanced oxidation processes (AOPs) is a promising avenue, yet the complete mineralization of certain FQ molecules remains elusive, raising concerns about the formation of toxic by-products. This study delineates five primary AOP degradation pathways for 16 commercially available FQ molecules, inferred from existing literature. Density functional theory (DFT) was employed to calculate the bond dissociation energies within these pathways to elucidate the correlation between bond strength and molecular architecture. Subsequently, Comparative Molecular Similarity Index Analysis (CoMSIA) models were constructed for various degradation reactions, including piperazine ring cleavage, defluorination, hydroxylation, and piperazine ring hydroxylation. Three-dimensional contour maps generated from these models provide a deeper understanding of the interplay between FQ molecular structure and bond dissociation energy. Furthermore, toxicity predictions for 16 FQ molecules and their advanced oxidation intermediates, conducted using VEGA 1.2.3 software, indicate that degradation products from pathways P2 and P5 pose a heightened health risk relative to their parent compounds. Furthermore, the application of the Multwfn program to compute the Fukui function for FQ molecules discerns the disparity in degradation propensities, highlighting that N atoms with higher f0 values can augment the likelihood of piperazine ring cleavage. HOMO-LUMO distribution diagrams further confirm that methoxy substitution at the 1-position leads to a dilution of HOMOs on the piperazine ring and an increased energy gap for free radical reactions, diminishing the reactivity with hydroxyl radicals. This study elucidates the pivotal role of structural characteristics in FQ antibiotics for their degradation efficiency within AOPs and unveils the underlying mechanisms of bond dissociation energy disparities. The toxicity parameter predictions for FQ molecules and their intermediates offer unique perspectives and theoretical underpinnings for mitigating the use of high-risk FQs and for devising targeted degradation strategies to circumvent the generation of toxic intermediates in AOPs through molecular structure optimization.

Generation of dichloroacetonitrile with the co-presence of g-C3N4 and chloride in peroxymonosulfate/Vis system: Impacts and mechanism

Monitoring and regulating the formation of toxic byproducts in advanced oxidation processes (AOPs) is of great significance for their practical application in water treatment. In this work, we found that dichloroacetonitrile (DCAN), a common N-containing byproduct in chloramination disinfection, can be formed with the co-presence of g-C3N4 and chloride in a peroxymonosulfate (PMS) system. The measured value was 12.01 μM within 12 h under the given conditions. Structure analysis of raw and used g-C3N4 demonstrated that g-C3N4 decomposition indeed occurred, and C = N bonds acted as primary active sites, releasing N resources for subsequent DCAN formation. Additionally, multiple parameters, including the reactant (i.e., g-C3N4, PMS, Cl-, phenol) dose and solution pH, were observed to remarkably affect the yield of DCAN. Phenol was identified as the organic precursor of DCAN and may cooperate with inorganic chloramine to promote DCAN formation via the decarboxylation pathway. This study highlights the generation of DCAN in N-involved catalyst-based AOPs and improves understanding of the DCAN formation mechanism.

Reuse of Treated Wastewater for Crop Irrigation: Water Suitability, Fertilization Potential, and Impact on Selected Soil Physicochemical Properties

This study evaluates the suitability of treated wastewater (TWW: secondary effluent and membrane effluent) for crop irrigation and the resultant impact on crop growth and soil physicochemical characteristics. Carrot seeds (Daucus carota subsp. sativus) were grown on loam soil and irrigated with tap water (Tap), secondary effluent (SE), and membrane effluent (ME) until maturity. Bacteriological analyses showed four log counts of E. coli and thermotolerant coliforms for secondary effluent, making it unsafe for the irrigation of carrots. Tap water and membrane effluent fulfilled the microbial limit for water reuse and were suitable for irrigation. The sodium absorption ratio, Kelly index, and magnesium hazard assessments indicated that all three irrigation water streams were suitable for irrigation. The average mass of carrot fruits for Tap, SE, and ME was 2.14 g, 3.96 g, and 3.03 g, respectively. A similar trend was observed for the dry matter composition: Tap had 15.9%, SE had 18.3%, and ME had 16.6%. The soil pH increased from 7.08 to 7.26, 7.39, and 7.33 for tap water-, secondary effluent-, and membrane effluent-irrigated soils, respectively. Nitrate-nitrogen and potassium levels increased in the TWW-irrigated soil, while that of the tap water-irrigated soil decreased. Sodium levels in the TWW-irrigated soil increased significantly but did not induce soil sodicity. The application of the TWW enhanced the growth of the carrot plants and increased the soil nutrient levels. Hence, using TWW in agricultural irrigation could promote food production and also limit the overdependency on freshwater resources. However, TWW should be disinfected by using UV disinfection and ozonation to reduce the risk of microbial contamination. Such disinfection methods may not lead to the formation of toxic byproducts, and therefore secondary pollution to crops is not anticipated.

Persistent free radicals of activated carbon induce highly toxic by-products formation during chlorination

Both activated carbon (AC) and chlorine are commonly used in water treatment processes and thus the exposure of chlorine to AC surface is unavoidable under some circumstances. Therefore, evaluating the effects of AC, particularly the persistent free radicals (PFRs) of AC on the chlorination by-products is critical for drinking water safety. Here, through comparison of the chlorination process of different ACs with similar pore structure but different PFR intensities, it was found that AC with more PFRs generated more unknown by-products with lower relative cell viability (85%). The Fourier transform ion cyclotron resonance- mass spectrometry results showed that the proportions of one-chlorine and nitrogen containing by-products generated by AC with higher PFR intensity were 19.6% and 16.9%, respectively, which were higher than those generated by AC with lower PFR intensity. Furthermore, the polycyclic aromatic compounds and polyphenols with high toxicity were only found in the chlorination products of AC with high PFR intensity. The PFRs of AC could promote the chlorine decay and induce the generation of superoxide radical and chlorine radical, and thus led to the formation of more toxic by-products. This study provides new insights into the risks of water chlorination process and by-product formation in the presence of AC.

Mitigation of multiple pesticide residues in green bell pepper using natural extracts as an emerging trend in pesticide decontamination using GC–MS/MS

AbstractThe main objective of this work is to assess the effect of natural extracts and its characterization for the mitigation of multiple pesticide residues in green bell pepper. In this study, four plant extracts such as Acacia concinna, Albizia amara, Tamarindus indica, and Azadirachta indica have been used to mitigate the six pesticides present in green bell pepper and its phytochemical constituents were analyzed using gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC–MS/MS). In addition to that, the method for the quantification of six pesticide residues in green bell pepper using GC–MS/MS was validated according to SANTE/11312/2021 guidelines. The extracts of Acacia concinna, Albizia amara, Tamarindus indica, and Azadirachta indica were showed effective mitigation for selected pesticides. The phytochemical compounds present in plant extracts were correlated with its effect on the mitigation of multiple pesticide residues. The T. indica showed better pesticide mitigation efficiency when compared to A. indica, A. amara, and A. concinna, respectively. The plant extracts showed higher mitigation efficiency for organophosphorous pesticides than the synthetic pyrethroids. The nutritional and sensorial properties of green bell pepper were highly retained after pesticide decontamination using plant extracts. The results of this work indicated the application of plant extracts for the mitigation of multiple pesticides in green bell pepper by household and commercial processing units. This study addressed the balance between food safety and food quality.Practical ApplicationsPesticide contamination in vegetables is one of the major global food safety issues and it poses potent threat to human health. Pesticide decontamination is always a challenging task due to the unpredictability of types and levels of pesticides and the presences of multiple pesticides in contaminated vegetables. Washing of vegetables with water is the common procedure followed by both household and commercial units. However, washing of vegetables only with water is not enough to reduce the multiple pesticides residues to safe levels. The washing of vegetables with chemical solutions and other thermal and non‐thermal processing could result in toxic byproduct formation based on the types of pesticides present in contaminated sample. Hence, in this study, the plant extracts were characterized for its efficiency on the mitigation of multiple pesticide residues in vegetables has been analyzed by Gas Chromatography—Triple Quadrupole Tandem Mass Spectrometry and the method has been validated according to SANTE/11312/2021 guidelines. The phytochemical compounds of the plant extracts could be correlated with the effective multiple pesticide decontamination efficiency and the plant extracts were found to retain the physicochemical properties of vegetables during washing. The results of this study showed that the selected plant extracts could enhance the food safety without compromising food quality. The results of this study could be useful for the formulation of vegetables cleaning solutions for the effective mitigation of multiple pesticide residues.

Regulating the Thermal Behavior of Nitrocellulose by Stable Incorporation of a Green Supramolecular Salt

Commonly used inorganic potassium salts present challenges in nitrocellulose (NC)-based propellants due to poor dispersion, destabilization, and toxic byproduct formation. Environmental concerns drive interest in green flame suppressants. Here, we report a green supramolecular salt, carboxymethyl-cyclodextrin potassium (CM-CD-K) through alkalinization and etherification reaction. Molecular dynamic simulations reveal stronger interactions between CM-CD-K and NC. The loading of CM-CD-K within NC forms a stable structure with resistance to migration and defense against crystalline precipitation. Remarkably, static combustion tests show reduced flame areas and harmful gas concentrations compared to traditional potassium salt-doped NC. Kinetic analysis reveals a shift from order to Kamal-Sourour reaction with CM-CD-K addition. CD-based hybrid organic salts hold potential as eco-friendly propellant alternatives.

Removal of pollutants from water as a function of sustainable development

The realization of the concept of sustainable development is conditioned by the impact of human activities on natural resources, both renewable and nonrenewable. The basic areas that enable the concept of sustainable development are: food security, energy supply and environmental protection. Protection and use of water as the most important renewable resource is a problem present in all these areas. In the process of food and energy production, water is a raw material and means of work, and in environmental protection, the preservation of quality and protection of water from pollution, as well as water purification, is the most important problem. The constant increase in the number of inhabitants on planet Earth, as well as the accelerated development of society, industrial and technological, has led to the overexploitation of water resources, as well as increasing contamination of water. Decreasing the level of water quality reduces the possibility of its use, which has the immediate consequence of reducing its availability. Certain natural water selfpurification capacities can be reduced in extreme pollution or even completely eliminated. Such trends can lead, in the long term, to a significant reduction in water availability. Therefore, there is a constant need for simpler, more efficient and cheaper treatments for water purification. Conventional methods of water treatment of different origins are often accompanied by undesirable by-products, so modern research is aimed at finding environmentally friendly procedures. The ideal means for water treatment would be one that simultaneously disinfects, decomposes and oxidizes inorganic and organic pollutants, as well as removes colloidal or suspended material and heavy metals, without creating toxic side products. ferrate(VI) is recognized as one of the few such agents and is increasingly used in environmentally friendly water treatment processes. The use of ferrate(VI) as multifunctional chemical reagents has significant advantages in the simplicity and economic benefit of the water treatment procedure (use of one chemical, one dosing and mixing system and less production of sludge), as well as avoiding the formation of toxic by-products. The subject of this chapter is precisely the application of ferrate(VI) in the removal of pollutants from water of various origins in the function of sustainabledevelopment, through: reducing the use of chemicals, reducing the consumption of energy and water resources, environmentally friendly products, etc.

Selective Synergistic Catalytic Elimination of NOx and CH3SH via Engineering Deep Oxidation Sites against Toxic Byproducts Formation.

NOx and CH3SH as two typical air pollutants widely coexist in various energy and industrial processes; hence, it is urgent to develop highly efficient catalysts to synergistically eliminate NOx and CH3SH. However, the catalytic system for synergistically eliminating NOx and CH3SH is seldom investigated to date. Meanwhile, the deactivation effects of CH3SH on catalysts and the formation mechanism of toxic byproducts emitted from the synergistic catalytic elimination reaction are still vague. Herein, selective synergistic catalytic elimination (SSCE) of NOx and CH3SH via engineering deep oxidation sites over Cu-modified Nb-Fe composite oxides supported on TiO2 catalyst against toxic CO and HCN byproducts formation has been originally demonstrated. Various spectroscopic and microscopic characterizations demonstrate that the sufficient chemisorbed oxygen species induced by the persistent electron transfer from Nb-Fe composite oxides to copper oxides can deeply oxidize HCOOH to CO2 for avoiding highly toxic byproducts formation. This work is of significance in designing superior catalysts employed in more complex working conditions and sheds light on the progress in the SSCE of NOx and sulfur-containing volatile organic compounds.

Photocatalytic degradation of non-ionic, anionic, and cationic surfactants: from batch experiments through equilibrium/kinetic study to ecotoxicology analysis

Surface-active compounds constitute a group of important and widespread environmental pollutants. Among different methods used for their treatment, photocatalytic degradation is a promising and efficient solution. Nevertheless, the exact outcome of photodegradation of surfactants may be difficult to predict in case of concentrations used at the industrial scale and considering that the associated mechanism involves radicals which may potentially result in the formation of toxic by-products. In consequence, the aim of this study was to analyze the catalytic photodegradation of three groups of surfactants (three structurally diverse representatives of cationic, anionic, and non-ionic surfactants). Nanoparticles of zinc oxide were synthesized and used as a photocatalyst. The efficiency of photodegradation ranged from 93 to 100% at 10 mg/L, from 38 to 94% at 100 mg/L, and from 15 to 66% when the surfactants were supplied at 1000 mg/L, and the results depended on the structure of the compound subjected to treatment. Subsequent investigation of kinetics revealed that Freundlich, Langmuir or Dubinin-Radushkevich isotherms may be used to describe the adsorption of surfactants (1–65%) and allowed to establish the following order of reactivity: cationic > non-ionic > anionic. Subsequent LC–MS/MS studies of the residues were the basis for identification of photodegradation products for each respective compound. Ultimately, due to the fact that treated graywater is often used as potable water, the phytotoxicity of the degradation products was tested toward sorghum. It was established that in the majority of cases the treatment was efficient (in some cases stimulation of plant growth compared to control samples was observed), whereas an increase in toxicity was observed in case of two cationic surfactants (CTAB and benzalkonium chloride). Overall, the results presented in this study support the application of photocatalytic degradation as an efficient solution for treatment of surfactant-rich effluents.

Peracetic acid-based electrochemical treatment of sulfamethoxazole and real antibiotic wastewater: Different role of anode and cathode

Although has high oxidation capacity and low toxic by-product formation potential, the feasibility, mechanism, and antibiotic treatment performance of peracetic acid (PAA)-based electrochemical system remains unknown. This work systematically studied the electro-activation process of PAA, and distinguished the different mechanisms of anode and cathode. In the PAA-based electrochemical system, the anode mainly produces BDD(•OH), and the cathode is mainly the R-O• (especially CH3CO3•). These differences lead to different degradation pathway and toxicity evolution of sulfamethoxazole (SMX). The anode transformation products (TPs) show negative toxicity and are difficult to be further removed, while TPs from PAA-dominated cathode posed electron-donating effect and a tapering ecological risk. The BDD(•OH) can well mineralize the TPs produced from cathode. Moreover, the active chlorine produced by the anode can effectively avoid the accumulation of NH4+- N released by antibiotic degradation. In an undivided cell, PAA-based treatment for real antibiotic wastewater achieved 73.9%, 59.4%, 76.9%, and 31.7% of COD, TOC, NH4+- N, and TN removal, respectively. More importantly, when PAA existed in this system, the active chlorine and AOCl accumulation are inhibited (inhibition ratio 83.5% and 82.7%, respectively). This study provides theoretical and technical support for the practical application of PAA-based electrochemical system.

Electrochemical degradation of key drugs to treat COVID-19: Experimental analysis of the toxic by-products formation (PCDD/Fs)

Drug consumption has grown exponentially in recent decades, particularly during the COVID-19 pandemic, leading to their presence in various water sources. In this way, degradation technologies for pollutants, such as electrochemical oxidation (ELOX), have become crucial to safeguard the quality of natural resources. This study has as its starting point a previous research, which demonstrated the efficacy of ELOX in the removal of COVID-19 related-drugs, such as dexamethasone (DEX), paracetamol (PAR), amoxicillin (AMX), and sertraline (STR), using the electrolytes NaCl and Na2SO4. The present research aims to study the potential risks associated with the generation of toxic by-products, during the ELOX of cited drugs, specifically focusing on the highly chlorinated persistent organic pollutants (POPs), such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Dioxins and furans can be formed potentially in electrochemical systems from precursor molecules or non-precursor molecules in chloride medium. First, the degradation of the parent compounds was found to be complete. At this point, a comprehensive investigation was conducted to identify and analyse the by-products formed during the degradation process; precursors of PCDD/Fs, such as chlorophenols or hydroquinones were identified. Additionally, in continuation of the previous study, PCDD/Fs congeners were investigated, revealing elevated concentrations; the highest concentration obtained was for the congener 1,2,3,4,6,7,8-HpCDF (234.6 pg L−1 in NaCl) during degradation of the AMX. Finally, an assessment of the toxicity based on TEQ values was conducted, with DEX exhibiting the highest concentration among all compounds: 30.1 pg L−1 for NaCl medium. Therefore, the formation of minor by-products should not be underestimated, as they can significantly enhance the toxicity of the final sample, so the selection of the appropriate remediation technology, as well as the optimization of experimental operating variables, is determining in the treatment of pharmaceutical-contaminated waters.

PH-dependent bisphenol A transformation and iodine disinfection byproduct generation by peracetic acid: Kinetic and mechanistic explorations

Peracetic acid (PAA) is regarded as an environmentally friendly oxidant because of its low formation of toxic byproducts. However, this study revealed the potential risk of generating disinfection byproducts (DBPs) when treating iodine-containing wastewater with PAA. The transformation efficiency of bisphenol A (BPA), a commonly detected phenolic contaminant and a surrogate for phenolic moieties in dissolved organic matter, by PAA increased rapidly in the presence of I−, which was primarily attributed to the formation of active iodine (HOI/I2) in the system. Kinetic model simulations demonstrated that the second-order rate constant between PAA and HOI was 54.0 M−1 s−1 at pH 7.0, which was lower than the generation rate of HOI via the reaction between PAA and I−. Therefore, HOI can combine with BPA to produce iodine disinfection byproducts (I-DBPs). The transformation of BPA and the generation of I-DBPs in the I−/PAA system were highly pH-dependent. Specifically, acidic conditions were more favorable for BPA degradation because of the higher reaction rates of BPA and HOI. More iodinated aromatic products were detected after 5 min of the reaction under acidic and neutral conditions, resulting in higher toxicity towards E. coli. After 12 h of the reaction, more adsorbable organic iodine (AOI) was generated at alkaline conditions because HOI was not able to efficiency transform to IO3−. The presence of H2O2 in the PAA solution played a role in the reaction with HOI, particularly under alkaline conditions. This study significantly advances the understanding of the role of I− in BPA oxidation by PAA and provides a warning to further evaluate the potential environmental risk during the treatment of iodine-bearing wastewater with PAA.

Deep mineralization of VOCs in an embedded hybrid structure CoFe2O4/MoS2/PMS wet scrubber system

Peroxymonosulfate (PMS)-based advanced oxidation processes in liquid phase systems can actively degrade toluene. In this work, the catechol structural surfactant was introduced to synthesize the dispersed and homogeneous CoFe2O4 nanospheres and embedded into MoS2 nanoflowers to form magnetically separable heterojunction catalysts. The innovative approach effectively mitigated the traditionally low reduction efficiency of transition metal ions during the heterogeneous activation process. In CoFe2O4/MoS2/PMS system, the toluene removal efficiency remained 95% within 2 h. The contribution of SO4⋅-, ·O2-, ·OH, and 1O2 was revealed by radical quenching experiment and electron paramagnetic resonance spectroscopy. The results illustrated that MoS2 offers ample reduction sites for facilitating PMS activation via Fe3+/Fe2+ redox interactions. Furthermore, an investigation into the toluene degradation pathway within the CoFe2O4/MoS2/PMS system revealed its capability to suppress the formation of toxic byproducts. This ambient-temperature liquid-phase method presented promising route for the removal of industrial volatile organic pollutants.

Hydrodynamic tearing of bacteria on nanotips for sustainable water disinfection

Water disinfection is conventionally achieved by oxidation or irradiation, which is often associated with a high carbon footprint and the formation of toxic byproducts. Here, we describe a nano-structured material that is highly effective at killing bacteria in water through a hydrodynamic mechanism. The material consists of carbon-coated, sharp Cu(OH)2 nanowires grown on a copper foam substrate. We show that mild water flow (e.g. driven from a storage tank) can efficiently tear up bacteria through a high dispersion force between the nanotip surface and the cell envelope. Bacterial cell rupture is due to tearing of the cell envelope rather than collisions. This mechanism produces rapid inactivation of bacteria in water, and achieved complete disinfection in a 30-day field test. Our approach exploits fluidic energy and does not require additional energy supply, thus offering an efficient and low-cost system that could potentially be incorporated in water treatment processes in wastewater facilities and rural communities.

Biosynthesis of silver nanoparticles with antioxidant and bactericidal activities using Capsicum annuum fruit extract

Metallic nanostructures, especially silver nanoparticles (AgNPs) have already found multiple applications in modern industry, science and medicine. Still, the production of nano-sized compounds often leads to the formation of toxic byproducts and possesses substantial environmental hazard. One of the promising solutions for the ecofriendly creation of nanomaterials predicts the use of a “green chemistry” approach using organisms, their parts or natural compounds to act as safe and effective producers of nanomaterials. Plant-mediated biosynthesis of silver nanoparticles includes the reduction of Ag+ to Ag0 by natural compounds, usually secondary metabolites which can be found in roots, leaves, cortex, fruits, flowers and seeds of various species. Aqueous extract of Capsicum annuum var. cv. (cultivar) Teja (S-17) fruits was used as a bioreducer for the reduction of AgNO3 solution to AgNPs. The formation of the AgNPs was confirmed by the presence of the Tyndall effect of light scattering combined with colour change of the solutions. The properties of the nanoparticles were assessed with UV-visible spectroscopy and scanning electron microscopy. In the present study, we report the experimental optimization of operating parameters needed for silver biotransformation by C. annuum. Biosynthesized nanoparticles were 13–22 nm in size and spherical in shape. Colloidal solutions of AgNPs were also confirmed to show antioxidant activity in vitro as analyzed by the reduction of DPPH radicals. Characterization and application of AgNPs as bactericidal agents on two Gram-positive (Micrococcus luteus, Staphylococcus aureus) and two Gram-negative (Escherichia coli, Pseudomonas aeruginosa) prokaryotic microorganisms demonstrated the prevalent influence on Gram-positive strains.

Gas purification technology from oxygen

The relevance of this research lies in the need of reproducing and expanding the technological scheme based on the gas field, located in the Orenburg Region. The technology for extracting oxygen from natural gas is not only underdeveloped — the market opportunities are perceived as limited, including the limitations of gas purification equipment (thus, the need for import). Therefore, the industry faces a new challenge — to develop expertise and competence in this area, which will further increase the economic part of the project. Objective: to implement the technology of APG (associated petroleum gas) purification from oxygen for its further supply to the main gas pipeline of Gazprom PJSC. The problem of purifying APG from high oxygen content is considered, showing the advantages and disadvantages of existing schemes, which is of high interest for practical application in field conditions. New environmentally friendly and cost-effective technologies for better treatment of the oxygen content of the APG in the field conditions are presented. The chosen technology excludes formation of toxic by-products and does not require construction of an expensive plant.