Thermal Plasma Treatment Research Articles

Dairy sludge characteristics and its degradation during thermal treatment and thermal plasma treatment

ABSTRACT Thermal treatment and thermal plasma treatment processes of dairy sludge were conducted. The thermal treatment was undertaken at temperatures from 200 °C to 1000 °C to establish the chemical composition and thermal degradation of the sludge. These results served as a foundation for interpreting the properties of the vitreous slag obtained from the sludge treated in the DC-transferred arc plasma reactor. The dairy sludge is characterised by a high volatile matter but also presents substantial ash content, with primary elements such as Al, P, Si, Ca, and Fe. The characterisations of the samples were made employing techniques like X-ray fluorescence, X-ray diffraction analysis (XRD), FT-IR spectrometry, Thermogravimetric analysis, and Differential Scanning Calorimetry. The results highlight the degradation of primary milk components like lactose, casein protein, and milk fat, with distinct differential thermogravimetric peaks at 230, 316, and 479 °C. As the temperature of thermal treatments approached 1000°C, silicon dioxide, calcium silicon, dicalcium silicate, and hydroxyapatite were identified in XRD spectra. Plasma-treated sludge features various oxide crystalline structures, including Al2O3, CaO(Al2O3)6, CaO(Al2O3)2, Ca2Al(AlSi)O7, KFeO2, and ZrO1.98. FTIR analysis of sludge identifies a complex organic composition presenting alkanes, amines, amides, hydroxyl groups, and metallic and semi-metallic oxide bond absorption. The FTIR results suggest the degradation of organic compounds and retention of phosphorous and aluminum bonds, especially after 600 °C. The vitreous slag from plasma treatment exhibits distinct composition characteristics without organic compound, presenting a vitreous and metallic/ceramic matrix. This research underscores the potential of thermal plasma treatments to neutralise dairy sludge.

Insights into the environmental risk variation of heavy metals from MSWI fly ash after thermal plasma vitrification

Thermal plasma vitrification of municipal solid waste incineration fly ash (MSWI FA) shows potential for effective dioxin degradation and heavy metal immobilization. However, the environmental risks posed by heavy metals released after vitrification remain understudied. This work investigates two types of MSWI FA—circulated fluidized bed fly ash (CFA) and mechanical grate furnace fly ash (GFA)—blended with waste glass and vitrified via thermal plasma treatment. The physical and chemical properties of the original FA and vitrified glasses (CFA-glass and GFA-glass) were analyzed. Environmental risks were assessed using the risk assessment code (RAC) and the overall pollution toxicity index (OPTI). Results showed that CFA, with higher Si and Al content, exhibited better vitrification than GFA. Plasma vitrification reduced chlorine content from 5.79 % and 10.59 % to 0.22 % and 0.16% due to Cl volatilization. Heavy metals with low boiling points, such as Cd and Pb, were significantly reduced, while high-boiling-point Cr, Ni remained and the acid resistance of vitrificated FA significantly deteriorated, which increased the potential leaching of heavy metals. In alkaline conditions, the OPTI value of CFA-glass dropped to 2, indicating a strong immobilization effect. This study provides critical insights for managing heavy metals in fly ash through thermal plasma vitrification.

Surface Treatment Strategies and Their Impact on the Material Behavior and Interfacial Adhesion Strength of Shape Memory Alloy NiTi Wire Integrated in Glass Fiber-Reinforced Polymer Laminate Structures.

Over the past few decades, there has been a growing trend in designing multifunctional materials and integrating various functions into a single component structure without defects. This research addresses the contemporary demand for integrating multiple functions seamlessly into thermoplastic laminate structures. Focusing on NiTi-based shape memory alloys (SMAs), renowned for their potential in introducing functionalities like strain measurement and shape change, this study explores diverse surface treatments for SMA wires. Techniques such as thermal oxidation, plasma treatment, chemical activation, silanization, and adhesion promoter coatings are investigated. The integration of NiTi SMA into Glass Fiber-Reinforced Polymer (GFRP) laminates is pursued to enable multifunctional properties. The primary objective is to evaluate the influence of these surface treatments on surface characteristics, including roughness, phase changes, and mechanical properties. Microstructural, analytical, and in situ mechanical characterizations are conducted on both raw and treated SMA wires. The subsequent incorporation of SMA wires after characterization into GFRP laminates, utilizing hot-press technology, allows for the determination of interfacial adhesion strength through pull-out tensile tests.

TO HIGHLY PRODUCTIVE SYNTHESIS OF ALUMINUM NANOPARTICLES IN PLASMA FLOW AT ATMOSPHERIC PRESSURE

Purpose. To study the highly productive evaporation of aluminum micron powder in an atmospheric pressure plasma jet for the synthesis of nanoaluminum. Using special plasma technology, nanoparticles can be produced by rapid melting and evaporation of the initial micrometer particles and their subsequent re-nucleation. Research methods. Methods of mathematical and computer modeling of subsonic plasma turbulent jets at atmospheric pressure and experimental studies of two-phase processes during thermal plasma treatment using an arc plasma torch. Results. Based on computer modeling, a special reactor system was designed and developed, which includes a plasma-jet reactor with an electric arc plasma torch for the synthesis of aluminum nanoparticles. Numerical modeling makes it possible to determine the position of the melting point, evaporation and crushing of a molten particle, the evolution of the fractional composition of the dispersed phase, and find the speed and temperature of the particle in the area from its melting point to the crushing point. An experimental test of the operation of the reactor system was carried out using arc plasma torches with a power of 30 and 150 kW. It has been shown that intensifying the fragmentation of dispersed raw materials in a plasma jet can be useful in technologies for producing nanomaterials. The consequence of the fragmentation process is the redistribution of the fractional composition of the powder along the plasma jet and the accompanying changes in the dynamics of movement, heating and evaporation of particles. It has been determined that when the temperature of the largest aluminum particles reaches 2500 C, the total amount of evaporated mass is theoretically equal to 100%. The main parameters influencing the behavior of particles in a plasma jet are particle diameter, powder injection rate, flow rate, temperature and composition of the plasma gas. Taking these parameters into account will allow the process to operate at increased productivity. Scientific novelty. A mathematical description of the process of fragmentation a polydisperse powder, based on a continuum approach, has been obtained, which makes it possible to determine the position of the crushing point of a molten particle, the fractional composition of the dispersed phase, and find the speed and temperature of the particle in the area from its melting point to the point of crushing and evaporation. It was shown for the first time that it is possible to carry out a process in which complete evaporation of a molten drop is achieved due to the high enthalpy of the plasma before the end of mixing with steam. Practical value. A special reactor system has been designed and developed, which includes a plasma-jet reactor with an electric arc plasmatron for the synthesis of aluminum nanoparticles. The operating parameters of the reactor system have been determined, which will allow the synthesis of aluminum nanoparticles to be carried out with high productivity.

Antibiotic Chloramphenicol degradation using submerged thermal plasma synergized with LaMnO3 catalyst

The present study focused on the degradation of antibiotic Chloramphenicol (CAP), an emerging contaminant, using submerged thermal plasma (STP) technology. Almost 99 % degradation and 82 % mineralization were achieved within 20 min of treatment by Ar/CO2 plasma, generated at 6.2 kW discharge power using a customized thermal plasma torch inside the aqueous solution. Kinetic analysis revealed first-order reaction for CAP degradation with a rate constant of 0.257 min−1. Long-lived species, such as H2O2, O3, NO2–, NO3–, and Cl- formed during plasma treatment were quantified. LaMnO3 perovskite (LMO) nanopowder prepared through a novel thermal plasma route, was introduced as catalyst into the treatment system which enhanced the degradation and mineralization efficiency by 34 % and 17 %, respectively, showing a strong synergetic effect between STP and catalyst. The energy yield was elevated from 102 mg/kWh to 144 mg/kWh with the addition of catalyst into the STP treatment system. Liquid chromatography-mass spectroscopy was used to identify the various degradation intermediates produced during thermal plasma treatment and correspondingly possible degradation pathways were proposed. The antibacterial activity assessment results revealed a significant reduction in the antimicrobial activity of all treated solutions against Gram-positive Bacillus cereus and Gram-negative Pseudomonas aeruginosa bacteria. Additionally, seed germination and growth assessment revealed a reduction in phytotoxicity of the treated solutions. STP, combined with the LMO, proved highly effective in treating pharmaceutical contamination in aqueous medium.

Effect of Thermal and Non-thermal Plasma Treatment on Particle Size Distribution, Protein Secondary Structure, Fuzzy Logic Sensory Evaluation, Rheological, and Selected Quality Attributes of Pineapple Juice: A Comparative Analysis

Effect of Thermal and Non-thermal Plasma Treatment on Particle Size Distribution, Protein Secondary Structure, Fuzzy Logic Sensory Evaluation, Rheological, and Selected Quality Attributes of Pineapple Juice: A Comparative Analysis

Modification in Surface Properties of Bismuth after Thermal Plasma Treatment

Modification in Surface Properties of Bismuth after Thermal Plasma Treatment

Growth methodologies of boron nitride nanotubes and their neutron shielding applications: a review.

This review provides a comprehensive overview of the growth methodologies and neutron shielding applications of Boron Nitride Nanotubes (BNNTs). BNNTs have garnered significant attention because of their unique combination of high thermal stability, mechanical strength, and exceptional neutron absorption properties. Synthesis methods for BNNTs, including laser ablation, thermal plasma treatment, chemical vapour deposition (CVD), and ball milling have been thoroughly examined, highlighting their mechanisms, advantages, and challenges. Each method contributes uniquely to the quality and applicability of BNNTs in terms of scalability and production efficiency. This study focused on the applications of BNNTs in neutron absorption, particularly in aerospace engineering. BNNTs have shown promising potential in enhancing the safety and longevity of space missions by providing effective radiation protection. Furthermore, their potential in medical applications, particularly in Boron Neutron Capture Therapy (BNCT) for cancer treatment, has been explored. BNCT offers a targeted approach to cancer therapy by utilizing the high boron-10 content of BNNTs for precise and localized treatment. This review also provides an outlook on the future of BNNT research, emphasizing the need for more efficient growth methods to facilitate wider adoption and commercialization. The versatility of BNNTs across various fields, from space exploration to medical science, underscores their potential as materials of significant scientific and technological importance. As research progresses, BNNTs are expected to play a pivotal role in advancing materials science and offer innovative solutions to complex challenges.

Thermal plasma treatment of tin for the enhancement of field emission properties

Thermal plasma treatment of tin for the enhancement of field emission properties

Heavy metal migration regimes in the production of syngas from solid waste by thermal plasma treatment

In recent years, thermal plasma technology has been widely used in the harmless and resource-efficient treatment of solid waste (SW). This study investigates the migration behaviors of heavy metals during the thermal plasma treats SW to obtain the interphase structure change regimes of heavy metals. The transformation of SW under high-temperature environments was analyzed by Fluent simulation, and the composition of the crystalline phases and heavy metal content of the post-treatment slags were studied through a combination of XRD, SEM, and heavy metal leaching experiments. The results show that the thermal plasma provides a melting zone temperature of more than 4000 K, and the treated slag is mostly an amorphous solid composed of glassy Si-O mesh, which effectively encapsulates heavy metals and reduces their leaching rate. Additional analysis of the migration and transformation of heavy metals during thermal plasma treatment revealed that solid-phase heavy metals primarily took the form of sulphides and sulphates, while liquid- and gas-phase heavy metals were mostly oxides and chlorides. Simultaneously, Economic analysis results showed that the thermal plasma treats SW economically with an Energetic efficiency of up to 76.7%. The results of this study providing new insights into thermal plasma treatment SW research.

Deep understanding the formation of hollow ZnO@ZnS core-sheath heterojunction towards efficient CO2 photoreduction

The utilization of solar energy to convert CO2 into small energy molecules is a potential “carbon neutral” technology for CO2 emission reduction. However, the industrial application is significantly constrained due to the low reduction efficiency, complexity of the synthesis methods, and limitations in scaling up the catalyst materials. In this work, we have successfully designed and synthesized a series of hollow tubular ZnO@ZnS core-sheath heterostructured materials, by combining radio-frequency thermal plasma and hydrothermal treatment technologies. The S:Zn molar ratio, reaction time, and temperature were systematically investigated, and the morphology of intermediate products was successfully captured, which provided conclusive evidence for the proposed formation mechanism. Notably, the photocatalytic CO yield of the ZS0.5O hollow nanotube core-sheath composite is not only 3.20 or 4.03 times higher than that of the pure ZnO or ZnS, respectively, but also possesses excellent stability. By in-depth characterization, we found that the hollow core-sheath heterostructure enhances light capture and absorption, exposes more effective active sites, and builds a type-II heterojunction between ZnO and ZnS to enhance the separation efficiency of charge carriers. The synergy of these factors significantly improves the catalytic performance, offering new insights for photocatalytic, electrocatalytic, and photoelectrocatalytic CO2 reduction.

Selective Surface Treatment Using Atmospheric Ar Plasma Jet for Aluminum‐doped Zinc Oxide Based Transparent and Flexible Electronics

AbstractTransparent and flexible electronics are emerging technologies with the potential to enable new applications. However, to ensure high‐performance transparent electronics, post‐processing such as thermal annealing and vacuum plasma treatment is necessary, which are difficult to apply to polymer‐based flexible substrates. This study analyzed the feasibility of applying selective Ar plasma jet treatment at atmospheric pressure to transparent flexible electronics. When atmospheric Ar plasma treatment is applied to transparent flexible aluminum‐doped zinc oxide (AZO), it showed a maximum 83.1% improvement in sheet resistance while maintaining a high transmittance performance, of over 70%. To verify the mechanism behind the surface treatment effect using atmospheric Ar plasma, comprehensive analyses are performed using atomic force microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy, which confirmed that the effect is due to oxygen vacancy formation caused by ion bombardment and thermal diffusion. The application of atmospheric plasma treatment to a patterned transparent flexible AZO device resulted in a reduction in contact resistance, and it is confirmed that the performance improvement effects can be retained for >500 h by applying additional passivation.

Nth order kinetic modelling of peroxidase and polyphenol oxidase inactivation in kiwifruit juice during cold plasma and thermal treatment

The current study examines the effect of thermal and cold plasma (CP) treatment on the inactivation of polyphenol oxidase (PPO) and peroxidase (POD) in kiwifruit juice. The residual activity of POD and PPO were fit to nth-order kinetics at a voltage, juice depth, and treatment time range of 18–30 kV, 2–10 mm, and 2–10 min, respectively. During thermal treatment, the inactivation order (n) value for POD and PPO were 1.07 and 1.06, whereas, for the cold plasma treatment, it was 2.07 and 2, respectively. The higher D-value of POD than PPO makes the former enzyme more resistant to plasma treatment. The Fourier-transform infrared spectroscopy (FTIR) revealed an increase in the proportion of β-sheet structure from 23 to 28% and a decrease in α-helix from 28 to 20% compared to the control sample. In comparison to thermal treatment, CP treatment effectively retained the biochemical attributes of juice. Industrial relevanceThe PPO and POD inactivation is necessary for preparing stable kiwifruit juice. A detailed kinetic study is mandatory for designing and optimizing the process, as both enzymes react in their way depending on the origin and experimental range. The generated kinetic model can be used to establish the optimum conditions for inactivating enzymes during CP treatment.

Surface Structuring of Zirconium by Thermal Plasma Treatment

Surface Structuring of Zirconium by Thermal Plasma Treatment

Thermal plasma vitrification treatment of oil-based drill cuttings: Product characterization and harmless transformation

Oil-based drill cuttings (OBDCs) are hazardous wastes associated with the process of oil and gas extraction. In this paper, OBDCs were treated using a self-designed plasma vitrification system. The basic physicochemical properties of the OBDCs were analyzed, followed by a plasma vitrification mechanism investigation of the OBDCs. The environmental pollution risk of the vitreous slags obtained from thermal plasma treatment was also evaluated with the heavy metal extraction toxicity procedure. The batch of vitreous slags with an average glass phase content of 98.60% had a dense and smooth surface and an oxygen-to-silicon (O/Si) ratio ranging from 3.68 to 4.32, according to the findings. The melting temperature and treatment duration have a great effect on the loss ratio on acid dissolution. The leaching concentrations of Pb and Zn were 0.0004 mg/L and 0.068 mg/L, respectively, consistent with the chlorination reaction promoted by thermal plasma. Fourier transform infrared spectroscopy analysis showed that there was no organic matter in the vitreous slag, achieving the goal of harmless transition. The specific energy consumption of vitreous slags was predicted and verified by response surface methodology (RSM). This study describes the vitrification process and harmless treatment of OBDCs by thermal plasma technology, and vitreous slags have great potential for resource utilization.

A Review of Current and Novel Methods of Medical Waste Management

According to the World Health Organization (WHO), high-income and low-income countries generate on average up to 0.5 kg and 0.2kg of hazardous waste per hospital bed per day, respectively. However, hazardous waste only accounts for 15% of total medical waste. The amount of total medical waste has increased over time, especially with medical supplies ordered during the COVID-19 pandemic. The purpose of the paper is to increase awareness of the problem regarding the difficulties of medical waste management and discuss possible solutions to these challenges. This review will inquire into the various methods of medical waste management, their current statuses, and their environmental, economic, and social impacts. Types of medical waste include pharmaceuticals, blood/blood-related products, sharps, body parts/tissues/organs, contaminated equipment, and COVID-19 products. The author describes in detail the environmental, economic, and social implications of the use of landfills, incineration, steam sterilization, sewage, and common forms of improper disposal, during which the author discusses impacts such as leaching and social disparities faced by developing countries. The author also considers economic and environmentally friendly medical waste management such as redistribution of medical supplies to vet clinics as well as innovative medical waste management technologies including thermal plasma treatment and plasma pyrolysis. The author suggests that medical waste management focuses on economical methods that have small environmental impacts and large social benefits such as methods of redistribution.

Characteristics and resource availability of Zinc-rich fly ash generated from medical waste through rotary and plasma thermal treatment

Fly ash from medical waste (MW) thermochemical treatment is disposed of in concrete landfills due to its well-known pollution property, while its recycling potential is ignored. This study is the first to explore the environmental characteristics, resource availability, and recovery method of medical waste incineration fly ash (MW-IFA) and medical waste plasma vitrification fly ash (MW-PFA) in China. Features of high chloride levels (28.27–42.89%) and richness in Zn (3.15–7.53%) were observed in all fly ash samples. Notably, low-calcium MW-IFA and MW-PFA may posed higher environmental risks due to much higher zinc leaching concentrations (1621.83–5163.97 mg/L) than high-calcium MW-IFA (2.58–5.02 mg/L). Moreover, the resource availability of Zn measured by water washing, acid leaching and thermal treatment was similar, with the range of 20.69–96.84%, 60.89–90.57%, 60.17–96.82%. Hence, considering avoiding excessive energy consumption, the MW fly ash dissolution and recovery (MWFADR) technology, combining water washing and acid leaching processes, was proposed for ZnO and crystal salt production. The results of this work highlight the recovery potential of Zn and Cl in MW fly ash and propose an environmentally and economically sound solution.

Plasma induced rich oxygen vacancies fiber-like ZnO for efficient photocatalytic CO2 reduction

Photoreduction CO2 to value-added fuels (CO, CH4, etc.) driven by solar energy gives a green way for managing the global carbon balance. Through the radio-frequency thermal plasma treatment, fiber-like structured ZnO with rich oxygen defects were successfully designed and synthesized. The rich oxygen vacancies, created new energy level, could not only hinder the recombination of photo-generated electron/hole pairs, but also broaden the light absorption range. Besides, combined the natural advantages of one-dimensional (1D) structure, which could enable itself avoid aggregation during performance evolution within the humid environment and shorten the transfer path length of the photo-induced carriers and promote more electron/hole to migration to the surface of the photocatalyst. Therefore, when applied in CO2 photoreduction, the optimal fiber-like ZnO with rich oxygen defects catalyst behaved outstanding photocatalytic performance with a CO2-to-CO rate of 15.76 μmol g-1 h−1.

Determination of cytotoxicity following oxidative treatment of pharmaceutical residues in wastewater

Pharmaceutical residues are released in the aquatic environment due to incomplete removal from wastewater. With the presence of multiple chemicals in sewage waters, contaminants may adversely affect the effectiveness of a wastewater treatment plant (WWTP). In certain cases, discharged metabolites are transformed back into their pristine structure and become bioactive again. Other compounds are persistent and can withstand conventional wastewater treatment. When WWTP effluents are released in surface waters, pristine and persistent chemicals can affect the aquatic environment. To complement WWTPs and circumvent incomplete removal of unwanted chemicals or pharmaceuticals, on-site wastewater treatment can contribute to their removal. Advanced oxidation processes (AOPs) are very powerful techniques for the abatement of pharmaceuticals, however, under certain circumstances reactive toxic by-products can be produced. We studied the application of on-site AOPs in a laboratory setting. It is expected that treatment at the contamination source can eliminate the worst polluters. Thermal plasma and UV/H2O2 oxidation were applied on simulation matrices, Milli-Q and synthetic sewage water spiked with 10 different pharmaceuticals in a range of 0.1 up to 2400μg/L. In addition, untreated end-of-pipe hospital effluent was also subjected to oxidative treatment. The matrices were activated for 180min and added to cultured HeLa cells. The cells were 24h and 48h exposed at 37°C and subsequently markers for oxidative stress and viability were measured. During the UV/H2O2 treatment periods no toxicity was observed. After thermal plasma activation of Milli-Q water (150 and 180min) toxicity was observed. Direct application of thermal plasma treatment in hospital sewage water caused elimination of toxic substances. The low cytotoxicity of treated pharmaceutical residues is likely to become negligible if plasma pre-treated on-site wastewater is further diluted with other sewage water streams, before reaching the WWTP. Our study suggests that AOPs may be promising technologies to remove a substantial portion of pharmaceutical components by degradation at the source. Further studies will have to be performed to verify the feasibility of upscaling this technology from the benchtop to practice.

Continuous-Flow Synthesis of Perfluoroalkyl Ketones via Perfluoroalkylation of Esters Using HFC-23 and HFC-125 under a KHMDS–Triglyme System

Abstract Hydrofluorocarbons (HFCs) are widely used as cooling agents in refrigerators and air conditioners and as solvents in industrial processes. However, their application has been restricted by their high global warming potential. Thus, strategies for HFC decomposition and effective utilization are urgently required. Herein, we describe a method for the chemical transformation of two HFCs, viz. HFC-23 and HFC-125, based on the continuous-flow perfluoroalkylation of esters to synthesize the pharmaceutically and agrochemically vital trifluoromethyl and pentafluoroethyl ketones. The combination of a potassium base and a glyme solvent system is found to be the most effective. The proposed method is attractive for industrial use because it allows the consumption of a large volume of HFCs, promotes the synthesis of high-value medicinal compounds, and serves as an ideal alternative to the current HFC decomposition processes like thermal plasma treatment.