Abatement of gas-phase VOCs via dielectric barrier discharge plasmas

Analysis and identification of degradation products in gas, particle, and liquid phases of polypropylene and polyethyleneterephthalate microplastics aging through non-thermal plasma simulation

Plastic aging can cause alterations in the physical and chemical characteristics of plastics, as well as their behavior in the environment. Due to the extremely slow natural aging process, laboratory simulated aging methods have to be used. In this study, non-thermal plasma (NTP) was adopted to investigate the aging process of polypropylene (PP) and polyethylene terephthalate (PET) microplastics. Various analytical instruments, including proton transfer reaction mass spectrometry and single-particle aerosol mass spectrometry, were employed to examine and identify the organic constituents of the gas, liquid, and particle phase degradation products, as well as to monitor the degradation process. The results showed that after 90 min of aging, both PP and PET surfaces showed yellowing, and the carbonyl index of PP increased while that of PET decreased, with an increase in crystallinity. The organic components of reaction products, such as ketones, esters, acids, and alcohols, increased with longer aging times. Gas products mainly contain aromatic hydrocarbons, while particles from aged PET contain compounds with benzene rings and metal elements. Liquid products from aged PP show a significant presence of branched alkanes. Based on this analysis, degradation mechanisms of PP and PET by NTP were proposed. This investigation represents the initial systematically exploration of the release of organic substances during the degradation of microplastics mediated by NTP. It provides significant insights into the detrimental organic compounds emitted during this process, thereby offering valuable information for understanding the environmental and human health implications of natural microplastic degradation. Furthermore, it addressed the requirements for increased attention to the potential environmental risks associated with these harmful components.

Removal of toluene via non-thermal plasma generated by applying rare-earth tungsten electrode and nanosecond pulsed power supply

The objective of this investigation is to evaluate the characteristics associated with degradation of toluene through the utilization of non-thermal plasma (NTP) generated via application of a low-work-function electrode and nanosecond pulsed power supply. Initially, a comparative analysis is made between toluene removal efficiency utilizing the low-work-function electrode and that achieved with the conventional stainless-steel electrode. The outcomes demonstrate that NTP generated by the low-work-function electrode exhibits markedly superior removal efficiency for toluene in comparison to the stainless-steel electrode operating at the same voltage. Subsequently, the impacts of voltage, pulse frequency, and initial concentration of toluene on the removal efficiency and production of by-products are investigated. It is found that as the voltage and frequency increase, the removal efficiency also increases, and a maximum toluene removal efficiency of 87.2% is achieved at a voltage of 12,000 V and pulse frequency of 2000 Hz. The removal efficiency first increases and then decreases with increasing toluene initial concentration. The investigation also finds that energy yield is negatively correlated with voltage and pulse frequency and positively correlated with the initial concentration. Finally, the reaction products were subjected to quantitative analysis using GC-MS. Based on the analysis results, potential reaction pathways are inferred.

Comparing removal of synthetic anthraquinone dye wastewater in an electrical discharge and UV-LED/WO3 reactors: using statistical Taguchi optimization approach

Advanced oxidation processes (AOPs) are an available solution for the rapid growth of the water pollution problem. In the present study, the process of UV-LED/WO3 and plasma was comparatively studied to remove reactive blue 19. The photocatalyst process efficiency was analyzed by statistical Taguchi model. The effect of experimental variables of contact time, pH, catalyst dosage, and pollutant dosage was investigated and found that the model is able to explain the process due to the high value of R > 95%, and the optimum condition was at 10 mg/L of dye concentration, 1g/L of catalyst, and 180 min of detention time in which over 75% of degradation was achieved. Based on the model, the more reaction time would increase the reactor performance, while further excessive increase of catalyst dosage over 1 g/L would deteriorate the performance. Obviously, the least amount of pollutant is the most favorable for the treatment reactor. Using plasma process for dye degradation was the next step of the research. Accordingly, the removal rate achieved over 90% of 10 mg/L of initial industrial dye in durational time of 4 min, input voltage 13.5 kV, and pH = 2. The results showed the higher oxidizing capacity of plasma than the conventional photocatalyst process.