Degradation of mixed typical odour gases via non-thermal plasma catalysis

Enhanced plasma-driven H2S removal from natural gas via TiO2-coated dielectric surface modification

The efficient removal of H2S impurities from natural gas is critical for improving gas quality and reducing maintenance costs. This study explores the integration of dielectric barrier discharge (DBD) plasma with TiO2 to decompose H2S effectively. Results show that the presence of TiO2 significantly improve H2S removal and energy efficiency compared with the plasma-only condition. However, the TiO2-coated system achieves a much higher H2S removal rate (5.4 mmol/h/gTiO2), which was 27 times that of TiO2-packed system, minimizing TiO2 usage. Moreover, coated TiO2 inhibits methane conversion, preserving the primary components of natural gas. Discharge analysis reveals that packing TiO2 increases the reduced electric field and enhances mean electron energy, while coating further promotes filamentary discharge. Density functional theory (DFT) calculations confirm that defect-rich TiO2, formed under plasma conditions, plays a crucial role in facilitating H2S decomposition. A plausible reaction pathway for plasma-driven H2S decomposition with coated TiO2 is proposed. This study demonstrates the potential of DBD-coupled coated catalyst technology for efficient H2S removal, offering a scalable solution for industrial gas purification.

A review of enhanced adsorption removal of odor contaminants with low ppm concentration levels: the key to technological breakthrough as well as challenges

The industrial production processes often produce different concentrations and types of odorous pollutants. Most odors have a low odor threshold, and the human sense of smell can still have a strong, unpleasant odor even at low ppb concentrations. The main challenges in low ppm concentration odor purification are short contact time, high air volume, low equilibrium adsorption capacity, and easy physical desorption. For the first time, this work reviews the technical paths how to purify four typical types of low concentrations of odors such as H2S, NH3, CH3SH, and CH3SCH3 from low ppm concentration levels to low ppb, with the view of the odor sources, the development of treatment technology, international permissible emission standards, and the recent status of adsorbent materials. To begin, Citespace software is employed to analyze the progress, hotspots, and technology trends in the field of odor pollutant research over the past 28 years and the factors that affect removal efficiency of low-concentration odorous pollutants are discussed in detail. Then, taking activated carbon, molecular sieve, and metal-organic frameworks as target adsorbents, how to strengthen the integrated ways of physical adsorption and chemical adsorption of these adsorbents are suggested starting from the synergistic effects of modifications for pore structure, surface chemical functional groups, and complexation and redox reactions of metal ions. As a practice, the application cases of purifying low-concentration odorous pollutants by the adsorption are briefly introduced. Finally, the challenges of developing novel adsorption materials and technologies to purify low-concentration odorous pollutants toward lower than odor threshold are presented.

Progress on hydrogen sulfide removal: From catalytic oxidation to plasma-assisted treatment

Air pollution is a long-standing environmental challenge as well an important economic subject. Hydrogen sulfide is one the major pollutants in the industrial releases. This review focuses on the thermochemical treatment of hydrogen sulfide based on the most recent works to date regarding its removal. By analyzing fundamental steps in chemical reaction engineering, some useful factors are emphasized since they are often neglected in scientific studies, catalysts design and process scale-up. From processing side, the fluid flow conditions including velocity, H2S concentration, relative humidity, temperature and pressure strongly influence the kinetic behavior and so the catalytic performance of the H2S removal reactor. From material side, the catalyst properties including nature, porosity, pore types, size, sites distribution and layer structuration largely influence the removal performance via among others the accessibility to catalytic sites, pores connection and mass transfer resistance. Plasma-assisted catalytic removal of H2S combines many novelties in comparison with a classical thermo-catalytic process. From patents review, we can see that main concerns are about electrodes mounting, reactor lifetime and modular design to solve the problems in the industrial practice. We attempt to provide for scientists, engineers and industrialists a guidance on the design of catalysts and processes for H2S removal which could be applied in laboratorial studies and industrial processes as well.

Plasma-catalyzed combined dynamic wave scrubbing: A novel method for highly efficient removal of multiple pollutants from flue gas at low temperatures

In this study, we developed a novel approach combining a non-thermal plasma system with M(Ce, Cu)-Mn/13X oxidation and post-dynamic wave wet scrubbing technologies, for effectively removing multiple pollutants from flue gases. Experimental results demonstrated that the plasma coupled with post-dynamic wave wet scrubbing achieved impressive synergistic removal efficiencies of 98% for SO2, 50.9% for NO, and 51.3% for Hg0 in flue gas. Through the use of M(Ce, Cu)-Mn/13X catalysts synthesized via the co-precipitation, the oxidation efficiency of the system is significantly enhanced, with synergistic removal efficiencies reaching up to 100% for SO2, 98.7% for NO, and 96% for Hg0. Notably, (Ce-Mn)/13X exhibited superior catalytic activity, the results are supported by comprehensive sample characterization, DFT mechanistic analysis, and experimental validation. Additionally, we elucidated the plasma oxidation mechanism and the working principles of the M(Ce, Cu)-Mn/13X loaded catalysts. This innovative technology not only facilitates pollutant oxidation but also ensures their complete removal from flue gas, providing a high-efficiency, cost-effective, and environmentally friendly solution for the treatment of multi-pollutants in flue gases.

Optimizing Winter Air Quality in Pig-Fattening Houses: A Plasma Deodorization Approach

This study aimed to evaluate the effect of two circulation modes of a plasma deodorization unit on the air environment of pig-fattening houses in winter. Two pig-fattening houses were selected, one of which was installed with a plasma deodorizing device with two modes of operation, alternating internal and external circulation on a day-by-day basis. The other house did not have any form of treatment and was used as the control house. Upon installing the system, this study revealed that in the internal circulation mode, indoor temperature and humidity were sustained at elevated levels, with the NH3 and H2S concentrations decreasing by 63.87% and 100%, respectively, in comparison to the control house. Conversely, in the external circulation mode, the indoor temperature and humidity remained subdued, accompanied by a 16.43% reduction in CO2 concentration. The adept interchange between these two operational modes facilitates the regulation of indoor air quality within a secure environment. This not only effectively diminishes deleterious gases in the pig-fattening house but also achieves the remote automation of environmental monitoring and hazardous gas management; thereby, it mitigates the likelihood of diseases and minimizes breeding risks.

1Non-thermal plasma coupled with a wet scrubber for removing odorous VOC

Odorous volatile organic compounds (VOCs) deteriorate the quality of life and affect human health. In this study, a process was developed to remove an odorous VOC using a combined non-thermal plasma (NTP) and wet scrubber (WS) system. The low removal efficiency of WSs and the large amount of ozone generated by NTP were resolved. Compared to the decomposition effects when using a WS and NTP separately, the NTP + WS system improved the removal efficiency of ethyl acrylate (EA) and significantly reduced ozone emissions. The maximum EA removal efficiency was 99.9%. Additionally, an EA removal efficiency of over 53.4% and a 100% ozone removal efficiency were achieved even at discharge voltages lower than 4.5 kV. Ozone catalysis was confirmed to occur in the NTP + WS system. Furthermore, we verified the removal of by-products such as residual ozone and formaldehyde, which is a representative organic intermediate of EA. This study demonstrates that the NTP + WS system is a green technology for removing odorous VOCs.

The Comparison of Biotreatment and Chemical Treatment for Odor Control during Kitchen Waste Aerobic Composting

Odor ΨΩγemission has become mathvariant="normal" mathvariant="sans-serif-bold-italic" an important issue in kitchen waste management. Ammonia and hydrogen sulfide are the two most important odor sources as they contribute malodor and can cause health problems. As biotreatment and chemical treatment are two majorly applied technologies for odor control, in this study, they were used to remove ammonia and hydrogen sulfide and the performance of each process was compared. It was found that chemical absorption could efficiently eliminate both ammonia and hydrogenmathvariant="script" sulfide, and the removal efficiencies of ammonia and hydrogen sulfide highly depended on the pH of the adsorbent, contacting time, and gas and solution ratio (G/S). The ammonia-removal efficiency reached 100% within less than 2 s at G/S 600 and pH 0.1. The complete removal of hydrogen sulfide was achieved within 2 s at G/S 4000 and pH 13. Biotrickling filter showed better ability for hydrogen sulfide removal and the removal efficiency was 91.9%; however, the ammonia removal was only 73.5%. It suggests that chemical adsorption is more efficient compared to biotreatment for removing ammonia and hydrogen sulfide. In the combination of the two processes, biotrickling filter followed by chemical adsorption, the final concentrations of ammonia and hydrogen sulfide could meet the Level 1 standard of Emission Standards for Odor Pollution (China). The study provides a potential approach for odor control during kitchen waste aerobic composting.