Formation Of Harmful By-products Research Articles

Deciphering the Mechanisms and Biotechnological Implications of Nanoparticle Synthesis Through Microbial Consortia.

Nanomaterial synthesis is a growing study area because of its extensive range of uses. Nanoparticles' high surface-to-volume ratio and rapid interaction with various particles make them appealing for diverse applications. Traditional physical and chemical methods for creating metal nanoparticles are becoming outdated because they involve complex manufacturing processes, high energy consumption, and the formation of harmful by-products that pose major dangers to human health and the environment. Therefore, there is an increasing need to find alternative, cost-effective, dependable, biocompatible, and environmentally acceptable ways of producing nanoparticles. The process of synthesizing nanoparticles using microbes has become highly intriguing because of their ability to create nanoparticles of varying sizes, shapes, and compositions, each with unique physicochemical properties. Microbes are commonly used in nanoparticle production because they are easy to work with, can use low-cost materials, such as agricultural waste, are cheap to scale up, and can adsorb and reduce metal ions into nanoparticles through metabolic activities. Biogenic synthesis of nanoparticles provides a clean, nontoxic, ecologically friendly, and sustainable method using renewable ingredients for reducing metals and stabilizing nanoparticles. Nanomaterials produced by bacteria can serve as an effective pollution control method due to their many functional groups that can effectively target contaminants for efficient bioremediation, aiding in environmental cleanup. At the end of the paper, we will discuss the obstacles that hinder the use of biosynthesized nanoparticles and microbial-based nanoparticles. The paper aims to explore the sustainability of microorganisms in the burgeoning field of green nanotechnology.

A Simple and Efficient Approach for the Synthesis of Aryl-3-(trifluoromethyl)-1H-1,2,4-triazol-5(4H)-one Derivatives

AbstractIn this work, a series of 4-aryl-3-(trifluoromethyl)-1H-1,2,4-triazol-5(4H)-one derivatives is synthesized through nucleophilic intramolecular cyclization reactions of ethyl 2-(2,2,2-trifluoro-1-(arylimino)ethyl)hydrazine-1-carboxylate intermediates, which are themselves prepared in high yields via reactions of ethyl chloroformate and N-aryl-2,2,2-trifluoroacetimidoyl chloride derivatives. Some of the merits of the reported procedure are an operationally simple and concise method, the ready availability of starting materials, excellent product yields, no formation of harmful by-products and easy purification of the products.

A Pragmatic Approach for Chlorine Decay Modeling in Multiple-Source Water Distribution Networks Based on Trace Analysis

Providing water with adequate quality to users is one of the main concerns for water utilities. In most countries, this is ensured through the introduction of disinfectants, such as chlorine, which are subjected to decay over time, with consequent loss of disinfection action and the possible formation of harmful by-products. In this context, water quality models can be a useful tool to support management and, thus, ensure sufficient standards in all network points, but most of these models require the input of reaction parameters which could be difficult to obtain based on the information available to water utilities, especially in the case of complex water distribution networks (WDNs) supplied by more than one source. This study proposes a pragmatic, interval-number-based method to model chlorine decay in complex WDNs by relying on the use of the network hydraulic model and the results of trace analysis, which are exploited to obtain overall reaction rates. The method is applied to the case of a real WDN supplied by water sources with different qualitative features. The results obtained highlight that the method can help water utilities in the identification of overall water quality parameters.

Fabrication of samarium doped MOF-808 as an efficient photocatalyst for the removal of the drug cefaclor from water.

MOFs are emerging photocatalysts designed by tuning organic ligands and metal centers for optimal efficiency. In this study, a samarium decorated MOF-808(Ce) metal organic framework was fabricated by facile hydrothermal synthesis. The synthesized samarium decorated MOF-808(Ce) was characterized by using analytical techniques such as SEM, EDX, XRD and TGA to study its morphological, thermal and structural properties. SEM images showed that MOF-808(Ce) comprised of truncated octahedrons. The morphology of the material was changed upon Sm incorporation. Sm/MOF-808(Ce) exhibited better UV-vis light absorption properties than MOF-808(Ce) as evidenced by its slightly higher band gap value. This material was exploited for the degradation of the drug cefaclor from water. Cefaclor removal followed double a first order in parallel model (DFOP). Under UV light, 97.7% of the cefaclor was removed in only 20 minutes and after 60 minutes this removal efficiency was increased to 99.25%. These features exhibited that samarium decorated MOF has immense potential for the photocatalytic degradation of cefaclor as it generates e- and h+ to enhance the photocatalytic efficiency and it is a promising candidate to treat wastewater without formation of harmful byproducts.

Inhibition of bromate formation in plasmon-enhanced catalytic ozonation over silver-doped spinel ferrite

High energy consumption and formation of harmful byproducts are two challenges faced by advanced oxidation processes (AOPs). While much research efforts have been devoted to improving the treatment efficiency, byproduct formation and control calls for more attention. In this study, the underlying mechanism of bromate formation inhibition during a novel plasmon-enhanced catalytic ozonation process with silver-doped spinel ferrite (0.5wt%Ag/MnFe2O4) as the catalysts was investigated. By scrutinizing the effects of each factor (i.e. irradiation, catalyst, ozone) as well as the combinations of different factors on major Br species involved in bromate formation, examining the distribution of Br species, and probing the reactive oxygen species partaking in the reactions, it was found that accelerated ozone decomposition which inhibited two main bromate formation pathways and surface reduction of Br species (e.g. HOBr/OBr− and BrO3−) contributed to the inhibition of bromate formation, both of which can be enhanced by the plasmonic effects of Ag and the good affinity between Ag and Br. A kinetic model was developed by simultaneously solving 95 reactions to predict the aqueous concentrations of Br species during different ozonation processes. The good agreement between the model prediction and experimental data further corroborated the hypothesized reaction mechanism.

Byproduct formation in heterogeneous catalytic ozonation processes

Heterogeneous catalytic ozonation (HCO) is a promising advanced oxidation process (AOP) that can effectively degrade recalcitrant organic pollutants; but formation of harmful byproducts should be carefully evaluated.

A Green Route to Benzyl Phenyl Sulfide from Thioanisole and Benzyl Alcohol over Dual Functional Ionic Liquids.

Benzyl phenyl sulfide is a kind of important chemicals with wide usage, which is mainly prepared through a nucleophilic reaction of thiophenol with benzyl chlorides or benzyl alcohols, suffering from inherent drawbacks, such as low efficiency, requirements for equivalent acid or base catalysts and formation of harmful byproducts and waste. Herein, we report a green route to access various benzyl phenyl sulfide derivatives in good to excellent yields under mild conditions via the reaction of thioanisoles with benzyl alcohols over ionic liquid 1-propylsulfonate-3-methylimidazolium trifluoromethanesulfonate ([SO3 HPrMIm][OTf]). Mechanism investigation indicates that the synergic effect of cation and anion of [SO3 HPrMIm][OTf] activates thioanisoles and benzyl alcohols via hydrogen bonding, thus catalyzes the dehydration of benzyl alcohol to dibenzyl ether and the subsequent metathesis reaction between dibenzyl ether and benzyl phenyl sulfide, finally generating benzyl phenyl sulfide derivatives. This is a simple, highly efficient, and green approach to produce benzyl phenyl sulfide derivatives, which has promising application potentials.

N-nitrosodimethylamine formation during oxidation of N,N-dimethylhydrazine compounds by peroxymonosulfate: Kinetics, reactive species, mechanism and influencing factors

This study found that peroxymonosulfate (PMS) oxidation without activation has the potential to generate a suspected human carcinogen, N-nitrosodimethylamine (NDMA), in water containing N,N-dimethylhydrazine compounds. Considerable amounts of NDMA formed from three compounds by PMS oxidation were observed. 1,1,1′,1′-Tetramethyl-4,4′-(methylene-di-p-phenylene) disemicarbazide (TMDS), which is an industrial antiyellowing agent and light stabilizer, was used as a representative to elucidate the kinetics, transformation products, mechanism and NDMA formation pathways of PMS oxidation. TMDS degradation and NDMA formation involved direct PMS oxidation and singlet oxygen (1O2) oxidation. The oxidation by PMS/1O2 was pH-dependent, which was related to the pH-dependent characteristics of the reactive oxygen species and intermediates. The degradation mechanism of TMDS mainly included the side chain cleavage, dealkylation, and O-addition. NDMA was generated from TMDS mainly via O-addition and 1,1-dimethylhydrazine (UDMH) generation. The cleavage of amide nitrogen in O-addition products and primary amine nitrogen in UDMH are likely the key steps in NDMA generation. The results emphasized that the formation of harmful by-products should be taken into account when assessing the feasibility of PMS oxidation.

A Review on the Degradation of Pollutants by Fenton-Like Systems Based on Zero-Valent Iron and Persulfate: Effects of Reduction Potentials, pH, and Anions Occurring in Waste Waters.

Among the advanced oxidation processes (AOPs), the Fenton reaction has attracted much attention in recent years for the treatment of water and wastewater. This review provides insight into a particular variant of the process, where soluble Fe(II) salts are replaced by zero-valent iron (ZVI), and hydrogen peroxide (H2O2) is replaced by persulfate (S2O82−). Heterogeneous Fenton with ZVI has the advantage of minimizing a major problem found with homogeneous Fenton. Indeed, the precipitation of Fe(III) at pH > 4 interferes with the recycling of Fe species and inhibits oxidation in homogeneous Fenton; in contrast, suspended ZVI as iron source is less sensitive to the increase of pH. Moreover, persulfate favors the production of sulfate radicals (SO4•−) that are more selective towards pollutant degradation, compared to the hydroxyl radicals (•OH) produced in classic, H2O2-based Fenton. Higher selectivity means that degradation of SO4•−-reactive contaminants is less affected by interfering agents typically found in wastewater; however, the ability of SO4•− to oxidize H2O/OH− to •OH makes it difficult to obtain conditions where SO4•− is the only reactive species. Research results have shown that ZVI-Fenton with persulfate works best at acidic pH, but it is often possible to get reasonable degradation at pH values that are not too far from neutrality. Moreover, inorganic ions that are very common in water and wastewater (Cl−, HCO3−, CO32−, NO3−, NO2−) can sometimes inhibit degradation by scavenging SO4•− and/or •OH, but in other cases they even enhance the process. Therefore, ZVI-Fenton with persulfate might perform unexpectedly well in some saline waters, although the possible formation of harmful by-products upon oxidation of the anions cannot be ruled out.

Human health risk estimation and predictive modeling of halogenated disinfection by- products (chloroform) in swimming pool waters: a case study of Dhanbad, Jharkhand, India.

Disinfection is an important process to make the water free from harmful pathogenic substances, but sometimes it results in the formation of harmful by-products. Development of predictive models is required to define the concentration of THMs in pool water. Majority of studies reported inhalation to be the most significant THMs exposure route which is more likely to be dependent upon the concentration of THMs in pool water and in air. THMs concentration in the analyzed pool water samples and in air was found to be 197.18 ± 16.31μgL-1 and 0.033μgm3-1, respectively. Statistical parameters such as high correlation coefficients, high R2 values, low standard error, and low mean square error of prediction indicated the validity of MLR based linear model over non-linear model. Therefore, linear model can be most suitably used to pre-assess and predict the THMs levels in swimming pool water. Risk estimation studies was conducted by using the united states environmental protection agency (USEPA) Swimmer Exposure Assessment Model (SWIMODEL). The lifetime time cancer risk values related to chloroform exceeded 10-6 for both the sub-population. Inhalation exposure leads to maximum risk and contributed up to 99% to total cancer risk. Risk due to other exposure pathways like accidental ingestion and skin contact was found to be negligible and insignificant. Monte Carlo simulation results revealed that the simulated THMs risk values for the studied exposure pathways lies within ±3.1% of the average risk values obtained using SWIMODEL. Hence, the risk estimates obtained using SWIMODEL seemed to be appropriate in determining the potential risk exposure of THMs on human health. Variation in input parameters like body weight (BW) and skin surface area (SA) leads to difference in risk estimates for the studied population. Non cancer risk was found to be insignificant as represented by low hazard quotient (HQ < 1) values. Through monitoring and regulations on control of THMs in swimming pool water is required to minimize the risk associated.

Occurrence of bisphenol A in surface and drinking waters and its physicochemical removal technologies

Bisphenol A (BPA), an endocrine disrupting compound, has caused wide public concerns due to its wide occurrence in environment and harmful effects. BPA has been detected in many surface waters and drinking water with the maximum concentrations up to tens of μg·L−1. The physicochemical technology options in eliminating BPA can be divided into four categories: oxidation, advanced oxidation, adsorption and membrane filtration. Each removal option has its own limitation and merits in removing BPA. Oxidation and advanced oxidation generally can remove BPA efficiently while they also have some drawbacks, such as high cost, the generation of a variety of transformation products that are even more toxic than the parent compound and difficult to be mineralized. Only few advanced oxidation methods have been reported to be able to mineralize BPA completely. Therefore, it is important not only to identify the major initial transformation products but also to assess their estrogenic activity relative to the parent compounds when oxidation methods are employed to remove BPA. Without formation of harmful by-products, physical separation methods such as activated carbon adsorption and membrane processes are able to remove BPA in water effluents and thus have potential as BPA removal technologies. However, the necessary regeneration of activated carbon and the low BPA removal efficiency when the membrane became saturated may limit the application of activated carbon adsorption and membrane processes for BPA removal. Hybrid processes, e.g. combining adsorption and biologic process or combining membrane and oxidation process, which can achieve simultaneous physical separation and degradation of BPA, will be highly preferred in future.

Recent Advancements in the Treatment of Municipal Wastewater Reverse Osmosis Concentrate—An Overview

Greater use of reverse osmosis (RO)-based processes in municipal wastewater reclamation presents the water industry with a major challenge regarding the sustainable management of the resultant RO concentrate (ROC) generated. This has promoted interest in investigating different approaches for the cost-effective treatment of ROC to reduce the risks associated with its disposal or reuse. This review highlights and discusses research on the treatment of ROC generated mainly from domestic wastewater.Methods employed for the treatment of municipal ROC are predominantly physicochemical processes, although biological processes with varying degrees of success in terms of the removal of organic content have also been reported. Relatively little attention has been paid to the quantification and removal of micropollutants. Due to the recalcitrant nature of some of the organics in ROC, advanced oxidation processes (AOPs) have been demonstrated to be the most effective for breaking down various pollutants and improving the biodegradability of the ROC. UV/H2O2, electrochemical oxidation, and ozonation are among the most studied AOPs for the treatment of ROC, and some have investigated posttreatment changes such as effect on molecular weight distribution and biodegradability improvement. Although these treatments appear to be promising, high energy consumption and the formation of harmful by-products during oxidative treatments are challenges that are yet to be fully addressed. Most studies have been conducted at laboratory scale and therefore large-scale investigation should be carried out to validate the effectiveness of these technologies.

Statistical analysis of trihalomethanes in treated-water tanks: seasonality, local variability and correlations

Chlorine was accepted as an effective disinfectant for drinking water in early 1900s. Because of chlorination, chlorine has dramatically reduced the incidence of waterborne diseases. An unwanted side effect is the formation of harmful by-products upon chlorination. The most significant group of disinfection by-products formed during chlorination is the trihalomethanes (THMs). In this reason, European Union initiated the maximum contaminant level (MCL) of total concentration of THMs to 100 μg L-1. Because of this regulation, operational parameters of the WTP and raw water quality characteristics need to be studied in depth in order for THMs to be minimised. Statistical analysis is necessary for this purpose employing the parametric two-way ANOVA for the concentrations of chloroform (CHCl3) and dichlorobromomethane (CHCl2Br) and the analysis of variance on data ranks of chlorodibromomethane (CHClBr2) concentration. Chlorine dose, postchlorination, bromide levels, reaction temperature, reaction duration and dissolved organic carbon levels as well as pH of raw water, are the factors that affect the rate of THMs formation and the total THMs yield. Athens Water Supply and Sewerage Company (EYDAP SA), as the water supplier of a city with 3.5 million inhabitants, makes continuous attempts to improve water quality.

Modelling lake-water photochemistry: Three-decade assessment of the steady-state concentration of photoreactive transients ([rad]OH, [formula omitted] and 3CDOM∗) in the surface water of polymictic Lake Peipsi (Estonia/Russia)

Over the last 3–4 decades, Lake Peipsi water (sampling site A, middle part of the lake, and site B, northern part) has experienced a statistically significant increase of bicarbonate, pH, chemical oxygen demand, nitrate (and nitrite in site B), due to combination of climate change and eutrophication. By photochemical modelling, we predicted a statistically significant decrease of radicals OH and CO3- (site A, by 45% and 35%, respectively) and an increase of triplet states of chromophoric dissolved organic matter (3CDOM∗; site B, by ∼25%). These species are involved in pollutant degradation, but formation of harmful by-products is more likely with 3CDOM∗ than with OH. Therefore, the photochemical self-cleansing ability of Lake Peipsi probably decreased with time, due to combined effects of climate change and eutrophication. In different environments (e.g. Lake Maggiore, NW Italy), ecosystem restoration policies had the additional advantage of enhancing sunlight-driven detoxification, suggesting that photochemical self-cleansing would be positively correlated with lake water quality.

Role of Bacteria in Arsenic Removal from an Aqueous Environment

Role of Bacteria in Arsenic Removal from an Aqueous Environment

Catalytic reduction of NO by hydrocarbons over a mechanical mixture of spinel Ni–Ga oxide and manganese oxide

NO reduction with propylene over Mn2O3, spinel Ni–Ga oxide and their mechanical mixtures has been investigated. Mn2O3 has no activity to NO reduction, but has a high activity for NO oxidation to NO2. Spinel Ni–Ga oxide showed an apparent activity to NO reduction only at temperatures above 400°C. Mixing of Mn2O3 to the Ni–Ga oxide resulted in a significant enhancement of NO reduction in the temperature range of 250–450°C. The optimal Mn2O3 content in the mixture catalyst was about 10–20 wt%. It is suggested that the synergetic effect of Mn2O3 and Ni–Ga oxide plays an important role in the catalysis of NO reduction. The Ni–Ga oxide and Mn2O3 mixture catalyst is superior to Pt/Al2O3 and Cu-ZSM-5 by showing a higher NO reduction conversion, resistance to water and negligible harmful by-product formation. Other lower hydrocarbons C2H4, C2H6 and C3H8 also give a maximum NO reduction conversion as high as 50%. The difference from using C3H6 is that the temperature at the maximum NO reduction is higher than it is with C3H6.

Selective reduction of NO x by ethanol on catalysts composed of Ag/Al 2O 3 and Cu/TiO 2 without formation of harmful by-products

An attempt was made to remove by-products such as NH 3, CH 3CN, HCN, CO and CH 3CHO which are produced from the reduction of lean NO x by ethanol over an alumina-supported silver catalyst. The efficiency of titania-supported noble metals, vanadium oxide, tungsten oxide, and copper sulfate for the removal of these compounds was examined. It was found that NH 3, CH 3CN, and HCN were easily oxidized to NO x and that the reduction of NO x to N 2 by these nitrogen-compounds did not occur effectively on noble metal catalysts. Among the tested catalysts, CuSO 4/TiO 2 was the most effective for simultaneously removing NH 3, CH 3CN, and HCN and reducing NO x to N 2 by using these nitrogen-compounds. Lean NO x were reduced to N 2 by ethanol effectively and the concentration of nitrogen-containing by-products was lowered over the composite catalyst, Ag/Al 2O 3+CuSO 4/TiO 2. However, in addition to CuSO 4/TiO 2, Pt/TiO 2 was required to remove harmful compounds completely. Consequently, a three-component composite catalyst, Ag/Al 2O 3+CuSO 4/TiO 2+Pt/TiO 2, has been employed in reducing lean NO x by ethanol. This composite catalyst has proved to be quite effective even in the presence of water vapor in that it can reduce lean NO x to N 2 by ethanol effectively and sufficiently lower the concentrations of all harmful by-products.