Formation Of Hazardous Byproducts Research Articles

The Catalytic Potential of Modified Clays: A Review

The need for innovative catalysts and catalytic support materials is continually growing due to demanding requirements, stricter environmental demands, and the ongoing development of new chemical processes. Since about 80% of all industrial processes involve catalysts, there is a continuing need to develop new catalyst materials and supports with suitable qualities to meet ongoing industrial demands. Not only must new catalysts have tailored properties, but they must also be suitable for large-scale production through environmentally friendly and cost-effective processes. Clay minerals, with their rich history in medicine and ceramics, are now emerging as potential catalysts. Their transformative potential is exemplified in applications such as hydrogenating the greenhouse gas CO2 into carbohydrate fuel, a crucial step in meeting the rising electrical demand. Moreover, advanced materials derived from clay minerals are proving their mettle in diverse photocatalytic reactions, from organic dye removal to pharmaceutical pollutant elimination and photocatalytic energy conversion through water splitting. Clay minerals in their natural state show a low catalytic activity, so to increase their reactivity, they must be activated. Depending on the requirements of a particular application, selecting an appropriate activation method for modifying a natural clay mineral is a critical consideration. Traditional clay mineral processing methods such as acid or alkaline treatment are used. Still, these have drawbacks such as high costs, long processing times, and the formation of hazardous by-products. Other activation processes, such as ultrasonication and mechanical activation routes, have been proposed to reduce the production of hazardous by-products. The main advantage of ultrasonication and microwave-assisted procedures is that they save time, whereas mechanochemical processing is simple and efficient. This short review focuses on modifying clay minerals using various new methods to create sophisticated and innovative new materials. Recent advances in catalytic reactions are specifically covered, including organic biogeochemical processes, photocatalytic processes, carbon nanotube synthesis, and energy conversion processes such as CO2 hydrogenation and dry reforming of methane.

Biomedical Applications and Patents on Metallic Nanoparticles

Aim: The manuscript aims to discuss the advanced biomedical applications and patents on metallic nanoparticles. Discussion: The preparation of metallic nanoparticles and their application are an influential area for research. There are various physical and chemical methods (viz. chemical reduction, thermal decomposition, etc.) for synthesizing silver nanoparticles; biological methods have been suggested as possible eco-friendly alternatives. The synthesis of metallic nanoparticles encounters many problems including solvent toxicity, the formation of hazardous by-products and consumption of energy. So it is important to design eco-friendly benign procedures for the synthesis of metallic nanoparticles. It is investigated from the study that metallic nanoparticles are used in the treatment of different diseases. Metallic nanoparticles are also used in the detection and therapy of cancer. These also have antifungal, antibacterial, anti-inflammatory, antiviral and anti-angiogenic properties. Conclusion: It is concluded from the manuscript that the synthesis of metallic nanoparticles is easy, eco-friendly, less time consuming and affordable. The metallic nanoparticles used in the biomedical field have an emerging future in nanoscience and nanotechnology.

Environmentally Persistent Free Radicals as Sources of POPs

Environmentally persistent free radicals (EPFRs) are a new class organic pollutant sharing some of the attributes of persistent organic pollutants (POPs). This opinion/short review aims to describe the properties of EPFRs that merit their recognition as an additional and potentially significant source of POPs. EPFRs are ubiquitous in diverse environments because of multiple factors: (1) organic precursors from anthropogenic, biogenic, and other natural emission sources are abundant; multiple mechanisms in PM and soils form (2) EPFRs; and (3) EPFRs are stable and persist for a long time, thereby, accumulate in the environment and potentially transported long range. The hazards of EPFRs arise from their ability to induce oxidative stress and the formation of hazardous byproducts. EPFRs are ultimately deactivated by reactive processes, yielding molecular recombination byproducts that are structurally similar to those classified as POPs. It is plausible that EPFRs may form POPs in vivo in organisms; therefore, they are potential additional sources of exogenous POPs. Understanding the formation of EPFRs and extensive investigation of the pollutants generated from their recombination will add to the growing body of knowledge on their environmental and health hazards.

Removal of Direct Red 81 from Aqueous Solution Using an Acidic Soil Containing Iron (Case Study of Lahijan Soil)

Direct Red 81, a dye widely used in textile industries, is frequently detected dye in water resources. High costs, the formation of hazardous byproducts, and high energy costs restrict the use of some removal methods. Therefore, the main objectives of this research are the feasibility of using soil containing iron as a low-cost adsorbent to remove (Direct Red 81) from the aqueous phase and determining the optimum conditions for maximum removal efficiency. The present study was conducted at a bench scale. The influence of different parameters including the number of adsorbents; initial concentration of dye solution and pH at different time intervals on dye removal efficiency were investigated. The maximum removal rate of dye (84%) occurred in pH=7 in the presence of 1 g soil with the initial dye concentration of 50 mg/L at 30 min reaction time. Moreover, due to the effect of acidic pH and the iron content of used soil, a significant increase was observed in the rate of Direct Red 81dye removal. In conclusion, using soil containing iron is an appropriate method for the removal of Direct Red 81 from aqueous solutions.

Antibacterial properties of Ag and Ag/AgCl nanoparticles from radish and tea extracts for water treatment applications

Silver nanoparticles (AgNPs) have antibacterial properties and are widely used for water disinfection. This technology is commercially applied in point-of-use water treatment as a post-treatment for filtrate water. However, the current process of synthesizing AgNPs has several disadvantages including the use of hazardous chemicals, consumption of a large amount of energy and the formation of hazardous byproducts. Here, we report an alternative and green synthesis using plant extracts. In this work, the plant extracts came from radish (R) and tea (T), and the AgNPs were derived from a microwave irradiation method. The AgNPs synthesized by chemical-based microwave irradiation (Ag-C) were also used as a control material. The novel method produced a smaller size of nanostructures with good dispersion ability and less agglomeration than those from chemical synthesis. The antibacterial properties of AgNPs on Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus) were investigated. The results revealed that AgNPs from both green synthesis and chemical-based methods inactivated both types of bacteria. The green-synthesized AgNPs from radish juice provided a higher percentage of inhibition of E. coli than that of S. aureus. The inactivation rates of the AgNPs increased with increasing concentration of AgNPs. As the concentration of the Ag/AgCl-R and Ag-R increased from 150 μg/mL to 300 μg/mL, complete inactivation required a reduced time for the reaction from 300 minutes to only 30 minutes. Finally, the Ag/AgCl-R and Ag-R offered high antibacterial activity while the Ag-T provided the lowest antibacterial activity. This work provides an alternative method for the eco-synthesis of antibacterial nanomaterials for water treatment.

Evaluation of the formation of oxidants and by-products using Pt/Ti, RuO2/Ti, and IrO2/Ti electrodes in the electrochemical process

The aim of this study was to evaluate the formation of oxidants and by-products by using different electrode materials, such as Pt/Ti, RuO2/Ti, and IrO2/Ti, in the electrochemical process. The harmful by-products and were formed during the electrolysis of a Cl− electrolyte solution, as well as active chlorine, which is the most common water disinfectant. With regard to drinking water treatment, the most efficient electrode was defined as that leading to a higher formation of active chlorine and a lower formation of hazardous by-products. Overall, it was found that the Pt/Ti electrode should not be used for drinking water treatment applications, while the IrO2/Ti and RuO2/Ti electrodes are ideal for use.

Greener Techniques for the Synthesis of Silver Nanoparticles Using Plant Extracts, Enzymes, Bacteria, Biodegradable Polymers, and Microwaves

The use of silver nanoparticles (AgNPs) is gaining in popularity due to silver’s antibacterial properties. Conventional methods for AgNP synthesis require dangerous chemicals and large quantities of energy (heat) and can result in formation of hazardous byproducts. This article summarizes recent activity in this general area where environmentally friendly synthetic techniques are currently being explored for the synthesis of “greener” AgNPs including the use of plant extracts, biodegradable polymers, and enzymes/bacteria and alternative energy input systems, such as microwave irradiation. Microwave heating enables efficient formation of nanostructures of uniform small sizes in shorter reaction times with reduced energy consumption; preventing agglomeration of ensuing nanoparticles is an additional attribute.

Molecular Cloning and Characterization of the Gene Coding for Azoreductase from Bacillus sp. OY1-2 Isolated from Soil

Azo dyes are regarded as pollutants because they are not readily reduced under aerobic conditions. Bacillus sp. OY1-2 transforms azo dyes into colorless compounds, and this reduction is mediated by a reductase activity for the azo group in the presence of NADPH. A 1.2-kbp EcoRI fragment containing the gene that encodes azoreductase was cloned by screening the genomic library of Bacillus sp. OY1-2 with digoxigenin-labeled probe designed from the N-terminal amino acid sequence of the purified enzyme. An open reading frame encoding the azoreductase, consisting of 178 amino acids, was predicted from the nucleotide sequence. In addition, because only a Bacillus subtillis hypothetical protein was discovered in the public databases (with an amino acid identity of 52.8%), the gene encoding the azoreductase cloned in this study was predicted to be a member of a novel family of reductases. Southern blot analysis revealed that the azoreductase gene exists as a single copy gene on a chromosome. Escherichia coli-expressing recombinant azoreductase gave a ten times greater reducing activity toward azo dyes than the original Bacillus sp. OY1-2. In addition, the expressed azoreductase purified from the recombinant E. coli lysate by Red-Sepharose affinity chromatography showed a similar activity and specificity as the native enzyme. This is the first report describing the sequencing and characterization of a gene encoding the azo dye-reducing enzyme, azoreductase, from aerobic bacteria and its expression in E. coli.

The Impact of Turbulent Mixing on the Oxidation of a Chlorinated Hydrocarbon

Combustion of chlorinated wastes can lead to the formation of hazardous byproducts. Rates of mixing of fuel and air in combustion systems can have an impact on the composition of the byproducts. Methyl chloride and methane were burned in a turbulent diffusion flame in a combustion wind tunnel with a coflow of air. Reynolds numbers were varied from 3500 to 7200. A water-cooled sampling probe was used to obtain gas samples from within the flame at a number of locations and at various Reynolds numbers. The postflame gases and particulate matter were trapped above the flames with sorbent tubes and filters. The samples were desorbed and analyzed for aromatic species and other trace products of incomplete combustion. Destruction of the methyl chloride was essentially complete for all the Reynolds numbers that were studied. Small amounts of low molecular weight chlorinated compounds were found within the flame and in the postflame gases. The major chlorinated species in the postflame gases was chloronaphthalene. Low Reynolds number flames were found to yield larger amounts of aromatic and chlorinated aromatic species than the high Reynolds number flames. Fluoranthene was present in greater amounts on the soot particles at lower Reynolds numbers, suggesting that the rate of mixing of reactants could have an impact on the toxicity of the combustion byproducts.