Search Results (14)

A novel cost-effective, rapid, and eco-friendly method was described for the removal of carbon dioxide (CO₂) from the gaseous emissions of gasoline engines. This involved the use of a sandwich filter (~10 cm diameter) made of a nonwoven poly (m-phenylene isophthalamide) (Nomex) fabric loaded with a thin layer of activated carbon. The optimized filter, with an activated carbon mass of 2.89 mg/cm², a thickness of 4.8 mm, and an air permeability of 0.5 cm³/cm²/s, was tested. A simple homemade sampling device equipped with solid-state electrochemical sensors to monitor the concentration levels of CO₂ before and after filtration of the emissions was utilized. The data were transmitted via a General Packet Radio Service (GPRS) link to an Internet of Things (IoT)-based gas monitoring system for remote management, and real-time data visualization. The proposed device achieved a 70 ± 3.4% CO₂-removal efficiency within 7 min of operation. Characterization of the filter was conducted using a high-resolution scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and Brunauer–Emmett–Teller (BET) analysis. The effects of loaded activated carbon mass, fabric type, filter porosity, gaseous removal time, and adsorption kinetics were also examined. The proposed filter displayed several advantages, including simplicity, compactness, dry design, ease of regeneration, scalability, durability, low cost, and good efficiency. Heat resistance, fire retardancy, mechanical stability, and the ability to remove other gasoline combustion products such as CO, SO_x, NO_x, VOCs, and particulates were also offered. The filtration system enabled both in situ and on-line CO₂ real-time continuous emission monitoring. Full article

Air pollution has become one of the biggest problems throughout the world. Smog has a severe effect on the pulmonary and circulatory systems, which causes a significant number of deaths globally. Therefore, the remediation of air pollutants to maintain ecosystem processes and functions and to improve human health is a crucial problem confronting mankind today. This review aims to discuss the health effects of smog on humans. This review will also focus on the bioremediation of air pollution (smog) using bacteria, fungi, phytoremediation, nanotechnology, and phylloremediation (using plants and microbes). Phylloremediation is the most effective technology for removing air pollution naturally. The future perspective presents a great need to produce an ecosystem where microbes, plants, and nanoparticles synergistically control smog. In addition, further advancements would be needed to modify the genetic makeup of microbes and plants. Biotechnological approaches like CRISPR-Cas9 can be applied to the editing and cutting of specific genes responsible for the bioremediation of VOCs, NOx, SOx, and harmful hydrocarbons. The extracted genes can then be expressed in biologically modified microorganisms and plants for the enhanced bioremediation of smog. Full article

Mercury (Hg) is a naturally occurring element and has been released through human activities over an extended period. The major source is the steel industry, especially sinter plants. During a sintering process, high amounts of dust and gaseous emission are produced. These gases contain high loads of SO_x and NO_X as well as toxic pollutants, such as heavy metals like Hg. These toxic pollutants are removed by adsorbing to solids, collected as by-products and deposited as hazardous waste. The by-products contain a high amount of salt, resulting in a high water solubility. In this study, to ultimately reduce the waste amount in landfills, leachates of the by-products have been produced. The dissolved Hg concentration and its distribution across different charges were determined. Hg concentrations between 3793 and 12,566 µg L⁻¹ were measured in the leachates. The objective was to lower the Hg concentration in leachates by chemical precipitation with sodium sulfide (Na₂S) or an organic sulfide followed by filtration. Both reagents precipitate Hg with removal rates of up to 99.6% for the organic sulfide and 99.9% for Na₂S, respectively. The dose of the precipitator as well as the initial Hg concentration affected the removal rate. In addition to Hg, other relevant heavy metals have to be included in the calculation of the amount of precipitator as well. Between relevant heavy metals including Hg and sulfide, the ratio should be more than 1.5. The novelty of this study is the measurement and treatment of Hg in wastewater with a high ionic strength. The high salt concentrations did not influence the efficiency of the removal methods. An adjustment of the precipitator dose for each sample is necessary, because an overdose potentially leads to the re-dissolving of Hg. It could be shown that the emission limit of 0.005 mg L⁻¹ could be reached especially by precipitation with Na₂S. Full article

The shipping industry is the most fuel-efficient means of transporting goods, carrying more than 90% of the global freight task. Ships generally use low quality fuel to reduce costs and, as a result, the sulfur content in the exhaust gas stream is high. Emissions of sulfur oxides (SO_x) and nitrogen oxides (NO_x) from ships represent about 13% and 12%, respectively, of the global anthropogenic SO_x and NO_x emissions. In total, 95% of the total maritime NOx emissions are NO (nitric oxide) and 5% are NO₂ (nitrogen dioxide). The present work focuses on the development and pilot operation of an advanced novel Selective Catalytic Reduction of NO_x with H₂ (H₂-SCR) technology for the elimination of Nitrogen Oxides (NO_x) emitted from ship exhaust gases. For the proper operation of the novel H₂-SCR de-NO_x unit, two additional conventional technologies were employed for the removal of SO₂ and Particulate Matter (PM). In particular, the proposed novel H₂-SCR de-NO_x technology was combined with a Sea Water Absorption (SWA) unit and an oxidative catalytic system. A pilot unit has been successfully designed, assembled and implemented on a cruise ship for the abovementioned purposes. This effort is considered to be pioneering and is here attempted for the first time worldwide. It was proven, for the first time ever, that the Selective Catalytic Reduction of NO_x with the use of H₂ as a reducing agent in combination with a suitable catalyst can be considered a suitable NO_x-pollution control technology for ships. In particular, it was found that more than 80% of NO_x (to N₂), 99.8% of SO₂ and 72% of PM can be reduced by using the present combined SWA and H₂-SCR technologies. Full article

Compared to diesel, liquefied natural gas (LNG), often used as an alternative fuel for marine engines, comes with significant advantages in reducing emissions of particulate matter (PM), SO_x, CO₂, and other pollutants. Promoting the use of LNG is of great significance for achieving carbon peaking and neutrality worldwide, as well as improving the energy structure. However, compared to diesel engines, medium- and high-speed marine LNG engines may produce higher methane (CH₄) emissions and also have nitrogen oxide (NO_x) emission issues. For the removal of CH₄ and NO_x from the exhaust of marine LNG engines, the traditional technical route of combining a methane oxidation catalyst (MOC) and an HN₃ selective catalytic reduction system (NH₃-SCR) will face problems, such as low conversion efficiency and high operation cost. In view of this, the technology of non-thermal plasma (NTP) combined with CH₄-SCR is proposed. However, the synergistic mechanism between NTP and catalysts is still unclear, which limits the optimization of an NTP-CH₄-SCR system. This article summarizes the synergistic mechanism of NTP and catalysts in the integrated treatment process of CH₄ and NO_x, including experimental analysis and numerical simulation. And the relevant impact parameters (such as electrode diameter, electrode shape, electrode material, and barrier material, etc.) of NTP reactor energy optimization are discussed. The work of this paper is of great significance for guiding the high-efficiency removal of CH₄ and NO_x for an NTP-CH₄-SCR system. Full article

Numerical analysis and experimental studies were conducted to evaluate the performance of a selective catalytic reduction (SCR) system according to the load of a 1.5-ton marine boiler. There are post-treatment methods for reducing the exhaust gas emitted from ships, such as low-sulfur oil, scrubber, a desulfurization device to remove sulfur oxides (SOx) and particulate matter, an exhaust gas recirculation system, and SCR agents to reduce nitrogen oxides (NOx). Furthermore, there are methods of using eco-friendly natural gas fuels, such as liquefied natural gas (LNG), methanol, liquefied petroleum gas, and ammonia. In the case of LNG, SOx and particulate matter are hardly emitted, and only a small amount of NOx is emitted compared to an internal combustion engine. Therefore, SCR system technology that can remove NOx needs to be applied. As a result of this study, the boiler load increased, and the flow velocity through the outlet decreased. In addition, the NOx emissions of diesel fuel and LNG fuel were reduced by 100% to 0 ppm when the boiler load ratio was 50%. When the load ratio was 75%, the NOx emissions of diesel fuel were reduced by 77.4% to 40 ppm, and those of LNG fuel were reduced by 64.1% to 24 ppm. When the load ratio was 100%, the NOx emissions of diesel fuel were reduced by 66.1% to 60 ppm, and those of LNG fuel were reduced by 47.8% to 24 ppm. In addition, the results of the numerical analysis according to boiler load were almost identical to the experimental results. Finally, this study could design an optimal SCR system through numerical analysis, according to the important parameters of the SCR system. Full article

To reuse waste glass fiber-reinforced plastics (GFRPs), porous ceramics (i.e., GFRP/clay ceramics) were produced by mixing crushed GFRP with clay followed by firing the resulting mixture under different conditions. The possibility of using ceramics fired under a reducing atmosphere as adsorbent materials to remove NO_x and SO_x from combustion gases of fossil fuels was investigated because of the high porosity, specific surface area, and contents of glass fibers and plastic carbides of the ceramics. NO₂ and SO₂ adsorption tests were conducted on several types of GFRP/clay ceramic samples, and the gas concentration reduction rates were compared to those of a clay ceramic and a volcanic pumice with high NO₂ adsorption. In addition, to clarify the primary factor affecting gas adsorption, adsorption tests were conducted on the glass fibers in the GFRP and GFRP carbides. The reductively fired GFRP/clay ceramics exhibited high adsorption performance for both NO₂ and SO₂. The primary factor affecting the NO₂ adsorption of the ceramics was the plastic carbide content in the clay structure, while that affecting the SO₂ adsorption of the ceramics was the glass fiber content. Full article

Co-absorption of NO₂ and SO₂ from flue gases, in combination with the enhanced oxidation of NO by ClO₂(g), is studied for three different flue gas sources: a medium sized waste-to-heat plant; the kraft recovery boiler of a pulp and paper mill; and a cruise ship. Process modeling results are used to present the technical potential for each site together with cost estimation and optimization using a bottom-up approach. A process set-up is proposed for each site together with equipment sizing and resulting flows of process fluids. The simulation results, supported by experimental results, show that removal rates equal to or greater than current best available technologies are achievable with more than 90% of NO_x and 99% of SO₂ removed from the flue gas. The resulting cost of removing both NO_x and SO₂ from the flue gases is 2100 €/ton for the waste-to-heat plant, 800 €/ton for the cruise ship and 3900 €/ton for the recovery boiler. The cost estimation show that the consumption and cost of chemical additives will play a decisive role in the economic feasibility of the investigated concept, between 50% and 90% of the total cost per ton acid gas removed. Full article

Nitrogen and sulpher oxides (NO_x, SO_x) have become a global issue in recent years due to the fastest industrialization and urbanization. Numerous techniques are used to treat the harmful exhaust emissions, including dry, traditional wet and hybrid wet-scrubbing techniques. However, several difficulties, including high-energy requirement, limited scrubbing-liquid regeneration, formation of secondary pollutants and low efficiency, limit their industrial utilization. Regardless, the hybrid wet-scrubbing technology is gaining popularity due to low-costs, less-energy consumption and high-efficiency removal of air pollutants. The removal/reduction of NO_x and SO_x from the atmosphere has been the subject of several reviews in recent years. The goal of this review article is to help scientists grasp the fundamental ideas and requirements before using it commercially. This review paper emphasizes the use of green and electron-rich donors, new breakthroughs, reducing GHG emissions, and improved NO_x and SO_x removal catalytic systems, including selective/non-catalytic reduction (SCR/SNCR) and other techniques (functionalization by magnetic nanoparticles; NP, etc.,). It also explains that various wet-scrubbing techniques, synthesis of solid iron-oxide such as magnetic (Fe₃O₄) NP are receiving more interest from researchers due to the wide range of its application in numerous fields. In addition, EDTA coating on Fe₃O₄ NP is widely used due to its high stability over a wide pH range and solid catalytic systems. As a result, the Fe₃O₄@EDTA-Fe catalyst is projected to be an optimal catalyst in terms of stability, synergistic efficiency, and reusability. Finally, this review paper discusses the current of a heterogeneous catalytic system for environmental remedies and sustainable approaches. Full article

Although replacing biomass, (e.g., wood chips and pellets), with thinning wood and herbaceous biomass is eco-friendly and economically advantageous, their direct utilization in plant boilers is associated with ash-related challenges, including slagging and fouling. The aim of this study is to determine the effects of ash removal treatment (ashless biomass (ALB)) in the context of solid fuel power plant boilers. Ash was removed via neutralization of metal ions and carboxylic acids contained in the biomass ash. The ash removal rate of K, Na, Cl was indicated by assessing the total biomass before and after ash removal treatment, via XRF analysis. Co-combustion with sub-bituminous coal and ALB-treated biomass was analyzed using a drop tube furnace and revealed that NOx and SOx values converged converge toward an approximate 10 ppm error, whereas the Unburned Carbon (UBC) data did not exhibit a specific trend. Factors associated with slagging and fouling, (capture efficiency (CE), and energy based growth rate (GRE)) were calculated. All biomass samples without pretreatment exhibited V-shaped variation. Conversely, for ashless biomass (ALB) samples, CE and GRE gradually decreased. Thus, the ALB technique may minimize slagging and fouling in a boiler, thus, reducing internal corrosion associated with ash deposition and enhancing the economic operation of boilers. Full article

Selective catalytic reduction (SCR) is the most efficient NO_X removal technology, and the vanadium-based catalyst is mainly used in SCR technology. The vanadium-based catalyst showed higher NO_X removal performance in the high-temperature range but catalytic efficiency decreased at lower temperatures, following exposure to SO_X because of the generation of ammonium sulfate on the catalyst surface. To overcome these limitations, we coated an NH₄⁺ layer on a vanadium-based catalyst. After silane coating the V₂O₅-WO₃/TiO₂ catalyst by vapor evaporation, the silanized catalyst was heat treated under NH₃ gas. By decomposing the silane on the surface, an NH₄⁺ layer was formed on the catalyst surface through a substitution reaction. We observed high NO_X removal efficiency over a wide temperature range by coating an NH₄⁺ layer on a vanadium-based catalyst. This layer shows high proton conductivity, which leads to the reduction of vanadium oxides and tungsten oxide; additionally, the NO_X removal performance was improved over a wide temperature range. These findings provide a new mothed to develop SCR catalyst with high efficiency at a wide temperature range. Full article

The development of efficient materials and processes is a long-term goal for the integrated flue gas purification in industry. In this study, a large-size V-based catalytic filter (L3000 mm × Φ150 mm) was prepared by loading the catalyst emulsion into a blank filter, which demonstrated excellent performance for simultaneously removing NO_x, SO_x and dust. The laboratory investigation found that the small catalytic particles, high catalyst loading and low face velocity could improve the DeNO_x efficiency, and above 80% NO conversion could be achieved in the temperature range of 250–400 °C on the condition of <300 nm catalytic particle size, >7.41 wt % catalyst loading and <1.00 Nm/min face velocity. The negative effect of SO₂/H₂O was only observed below 300 °C, and the dust had little negative effects on DeNO_x efficiency except for the increase of pressure drop. Moreover, a 90-day industrial test of 2380 catalytic filters over 100,000 Nm³/h of flue gas (0.50 Nm/min) from a glass kiln demonstrated that the removal efficiency of both NO_x and SO_x could be maintained above 95% with great stability at 320–350 °C, and 99% dust could be removed with a pressure drop of less than 1.40 KPa. The results reported herein indicate the promising application prospect of large-size V-based catalytic filters for integrated flue gas purification in industry. Full article

An effective dipping method for coating of textile fabrics with porous materials is proposed on the basis of the use of epoxy solution consisted of resins, crosslinkers, and dilution solutions. The removal rates of nitrogen oxides (NO_x), sulfur oxides (SO_x), and fine dust particles in the coated textile fabrics are accessed. The textile fabrics made of polyester are used to effectively reduce fine dust particles through static electricity. Zeolite and coconut shell activated carbon are used as porous material to reduce SO_x and NO_x, respectively. The effects of the epoxy content and dilution solution types on the SO_x removal rate of textile fabrics coated with zeolite are evaluated to determine the optimum coating conditions. In addition, the effects of external environmental conditions, such as washing and freeze thawing, on the SO_x and NO_x removal rates of the textile fabrics coated with porous materials using the optimum coating conditions are examined. The test results show that the SO_x removal rate of textile fabrics coated with zeolite decreases with the increase in the epoxy content. The decrease is 2.9 times larger for textile fabrics coated using deionized water than those coated using isopropyl alcohol. After one wash, the SO_x removal rate decreases dramatically. However, the decrease is reduced by 16% when the epoxy content ratio is increased by 0.5%. The effects of washing and freeze thawing on the SO_x and NO_x removal rates of textile fabrics coated using the deionized water diluted with the epoxy content ratio of 2% are minimal. Consequently, to maintain stable SO_x and NO_x removal rates under external environmental conditions such as washing and freeze thawing, 98% deionized water dilution and 2% epoxy content ratio are required for the optimum coating of textile fabrics with zeolite and coconut shell activated carbon. Full article

In the present work, a series of different materials was investigated in order to enhance the understanding of the role of modern lean NO_x trap (LNT) components on the sulfur poisoning and regeneration characteristics. Nine different types of model catalysts were prepared, which mainly consisted of three compounds: (i) Al₂O₃, (ii) Mg/Al₂O₃, and (iii) Mg/Ce/Al₂O₃ mixed with Pt, Pd, and Pt-Pd. A micro flow reactor and a diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) were employed in order to investigate the evolution and stability of the species formed during SO₂ poisoning. The results showed that the addition of palladium and magnesium into the LNT formulation can be beneficial for the catalyst desulfation due mainly to the ability to release the sulfur trapped at relatively low temperatures. This was especially evident for Pd/Mg/Al₂O₃ model catalyst, which demonstrated an efficient LNT desulfation with low H₂ consumption. In contrast, the addition of ceria was found to increase the formation of bulk sulfate species during SO₂ poisoning, which requires higher temperatures for the sulfur removal. The noble metal nature was also observed to play an important role on the SO_x storage and release properties. Monometallic Pd-based catalysts exhibited the formation of surface palladium sulfate species during SO₂ exposure, whereas Pt-Pd bimetallic formulations presented higher stability of the sulfur species formed compared to the corresponding Pt- and Pd-monometallic samples. Full article