By Ali Khadem
Today, considering the large-scale manufacturing of chemicals, the environment is facing the problem of air pollution more than ever. Problems such as global warming which have appeared due to emission of greenhouse gases and volatile organic compounds from factories and industries, have had deadly impacts on the body of the environment. In addition, the direct impact of these gases on humans has been observed through diseases such as asthma, bronchitis, dyspnea, cancer, heart attacks and different sorts of allergies which devour thousands of lives annually. In order to prevent these pollutants from emitting, various methods with specific upsides and downsides have been used.
In this study, the use of dielectric barrier discharge plasma technology in destructing the pollutants Benzene, Toluene and Xylene has been investigated. Throughout the experiments, factors like destruction rate of the reactor, effect of the applied voltage, different types and amounts of the byproducts and also, the temperature of the reactor were investigated. In this experiment, vapors of the mentioned pollutants entered the air plasma region inside the reactor by the help help of the carrier gas and were destructed. In order to measure the above factors, a thermometer, gas sensors, OES and GC analysis were used.
The results show that by increasing the applied voltage and the passing of time, temperature rises up to a certain point and correspondingly, destruction rates increase; in addition, high-energy electrons and other active species cause the high destruction of the pollutant molecules. The highest destruction rates recorded for Benzene, Toluene and Xylene were 82.31%, 80.88% and 69.68%, respectively. The major byproducts were CO and H2 and also, other hydrocarbons were produced in small amounts.
By: Ms. Sheikhi
In this study, starch film and starch/chitosan composite film were modified by a low pressure air and O2 plasma at different durations. The effects of plasma on the topography, wettability, chemical surface composition, mechanical properties, optical properties, oxygen permeability and water vapor permeability of the films
were examined. The mechanical properties of the both films were significantly improved. It is shown that air plasma is more efficient in improving tensile strength of the films due to more crosslinking at the air plasma treated film surface. No significant change in the starch film ҆s elongation at break was observed although
starch/chitosan composite film ҆s elongation at break was increased due to polymer degradation. After plasma treatment the roughness of the treated film surface increased due to etching effects of plasma. A significant increase in the hydrophilicity of the films was observed due to formation of oxygen-containing groups after plasma treatment. FTIR analysis illustrated a decrease in C-H groups
that caused an increase in C-O and COC groups in air treated films and carbonyl groups in O2 –treated films. Although an increase was found in hydrophilic groups on the film surface after plasma treatment, no significant change was observed in WVP of films, however oxygen permeability of the films were decreased.
Degradation of 4-chlorophenol in a Dielectric Barrier Discharge Plasma System
Being produced by chemical industries both as precursor and direct chemical for synthesis and other processes, hazardous and persistent chemical pollutants are drained into water sources. What is more, perpetual growth of consumerism in developing countries has culminated in pollution and shortage of water resources across the globe, which is an alarming trend for future generations. Meanwhile, most of industries produce persistent organic pollutants which not only are they carcinogenic, but also they have detrimental effects for environment and groundwater and they remain in water cycle and are not degraded by common water purification processes. For them to be effectively and optimally purified and minerlazied, advanced oxidation processes have been proposed recently.
In this dissertation, chlorophenols and amongst them 4-chlorophenol have been investiged. Chlorophenols (CPs) are frequently found in industrial effluents that are generated by the manufacturing of plastics, resins, textile, steel and paper. These contaminents constitute an important category of organic pollutants and some of them are identified as carcinogens and environmental endocrine disruptors. Dielectric Barrier Discharge (DBD) plasma has been applied for degradion of this contaminant. Reactive oxidative agents having high oxidation potentials are formed in plasma reactor to degrade and convert the contaminant. In order to measure the potential effect of the plasma reactor for degradation of the contaminat, GC and HPLC analysis have been conducted. Also for investigation of by-products in reactor, GC-MS and COD analysis have been carried out, and for investigation reactive species produced during degradation process Optical Emission Spectroscopy analysis has been performed.
In order to optimize and enhance the reactor’s removal efficiency, Oxygen and Argon bubbles fed through the discharge zone inside the reactor. Also effect of increasing the applied voltage has been investigated. Plasma degradation process has been compared to Ozonation which is one of the common processes of water purification. At last, several pathways leading to removal and degradation of the contaminent has been proposed.
Treatment and Gasification of Spent Caustic wastewater using Thermal Arc Plasma with Transfer Method
With the increasing competition between oil-rich countries to extract this underground source of energy, the problem of disposing of wastes from its distillation has become one of the most important global issues. In the petrochemical and refining industries, a lot of processing occur on the crude oil to extract its valuable products. One of the things that uses to refine petroleum products is caustics. After using, caustics are converted to pollutants (spent caustics), which the amount of these wastes are so much, and the existing technologies can not completely eliminate them. Now, if we can dispose, process or recycle these wastes with plasma methods, we have been able to produce valuable products from such industrial wastes.
For this purpose, using a thermal Arc plasma reactor with transfer method, we treated and gasified one of these wastes that is called sulfidic spent caustic wastewater and by performing experiments and studying of effective parameters (such as the effect of energy density and feed rate) on the production of products and the primary gas used materials (such as hydrogen gas) and have been examined the rate of production of these useful products. Finally, by optimizing the system and the conditions, we were able to obtain very favorable results from this method compared to previous methods, such as chemical methods, marine depletion and biological methods. The results obtained from these experiments can be promising to use the plasma industry as a new alternative technology or an auxiliary technology in petrochemical plants.
Comparative investigation of argon and argon/oxygen plasma
performance for Perchloroethylene (PCE) removal from aqueous
solution: optimization and kinetic study
Journal of Environmental Health Science and Engineering
Mostafa Karimaei, Babak Shokri, Mohammad Reza Khani, Kamyar Yaghmaeian, Alireza Mesdaghinia, Ramin Nabizadeh, Amir Hossein Mahvi & Shahrokh Nazmara
Purpose: The aim of this study is evaluation of the perchloroethylene degradation from aqueous solutions by non-thermal plasma produced in dielectric barrier discharge reactor in two different scenarios: first plasma generated with 225 cc/min mixture of oxygen and argon flow (12% gas ratio of O2/Ar), and in the second scenario plasma generated with 225 cc/min of pure argon gas. Methods Design studies were performed using response surface methodology and central composite design. All experiments
with the selected levels of independent parameters including the initial concentration of perchloroethylene (5–100 mg/L), voltage
(20–5 kv) and contact time (15–180 s) was implemented, and 29 tests were proposed by using response surface methodology and
central composite design was performed in two experimental scenarios.
Results showed that the Pseudo first-order kinetics coefficient of perchloroethylene degradation in the mixture of oxygen
and argon and pure argon scenario under the optimum conditions were 0.024 and 0.016 S–1 respectively. Results conveyed that in
order to achieve the highest removal efficiency (100%), the values of contact time, perchloroethylene concentration and voltage
variables were predicted 169.55 s, 74.3 mg/l, 18.86 kv respectively in mixture of oxygen and argon scenario and also were
predicted 203 s, 85.22 mg/l, 20.39 kv respectively in pure argon scenario.
Conclusions In the recent study dielectric barrier discharge was an efficient method for perchloroethylene removal with both
oxygen an argon mixture and pure argon as input gas. Both input voltage and reaction time has positive effect on perchloroethylene removal; but initial perchloroethylene concentration has negative effect on perchloroethylene removal. Comparison of two
plasma scenarios with different input gas shown that plasma generated by mixture of oxygen and argon gas was more powerful
and had higher removal efficiency and degradation kinetics than the plasma generated by pure argon gas.
high speed corona system was produced and developed in Plasma Lab.