جستجوی مقالات مرتبط با کلیدواژه « ازن زنی » در نشریات گروه « عمران »

Industrial progress has ushered in the production of a diverse array of pollutants, encompassing both organic and non-biodegradable substances, such as hydrocarbon compounds derived from petroleum. As the discernible environmental ramifications of these pollutants continue to escalate, the quest for efficacious methodologies for wastewater remediation assumes paramount importance. Among the emergent technologies, plasma technology has garnered considerable acclaim due to its capacity to obliterate a myriad of pollutants. Plasma, which ensues from the application of high voltage to either a gaseous or liquid medium, engenders profoundly reactive species capable of dismantling intricate organic compounds. Similarly, ozone, an exceedingly potent oxidizing agent, has long commanded recognition for its aptitude in the degradation of pollutants. Its robust oxidative attributes render it an invaluable instrument in the realm of wastewater treatment. Ozone treatment entails the infusion of ozone gas into the contaminated aqueous medium, whereupon it engages pollutants in a transformative reaction, rendering them into less deleterious byproducts. By amalgamating the ozonation process with plasma technology, we can harness the merits of both modalities and achieve synergistic effects. This hybridized approach proffers several advantages vis-à-vis individual treatment methodologies, including augmented pollutant removal efficiency, diminished treatment duration, and amplified energy efficiency. The plasma-ozonation process exploits plasma's propensity for the generation of reactive species, capable of reacting with the organic constituents in wastewater. The ensuing ozonation phase augments the degradation of these constituents, engendering a more efficacious and comprehensive removal process. Prior investigations have scrutinized the efficacy of ozone and plasma in isolation for the eradication of p-nitrophenol, a ubiquitous organic pollutant encountered in industrial wastewater. These inquiries have methodically examined various parameters to ascertain their influence on pollutant removal efficiency. Factors such as applied voltage, ozone dosage, initial pH, reaction duration, and initial solution concentration have been subjected to meticulous scrutiny to optimize the treatment regimen. In the present study, we have devised an innovative mathematical model to probe the interplay between these two independent variables: plasma technology and ozonation. The model incorporates a quadratic equation and employs analysis of variance (ANOVA) to gauge the significance of each variable and discern the optimal conditions for pollutant removal. Through scrutiny of the model, we have ascertained that the pinnacle of removal efficiency, surpassing 95%, materializes under specific parameters. These parameters encompass an applied voltage of 14 kV, an oxygen flow rate of 6 L/min, an initial pH of 10, a reaction duration of 6 minutes, and an initial concentration of 200 mg/L. These revelations offer valuable insights into the operational parameters that yield superlative results for pollutant removal within the context of the plasma-ozonation process. The efficacious integration of ozone and plasma technologies in wastewater treatment proffers a promising panacea for the elimination of p-nitrophenol pollutants and sundry other organic constituents. By fine-tuning the process parameters in alignment with the model's recommendations, we can attain exceptional levels of pollutant elimination whilst concurrently minimizing energy consumption and treatment duration. This research significantly contributes to the perennial endeavors aimed at fashioning sustainable and efficient remedies for industrial wastewater treatment, endowing valuable perspectives for their future deployment and widescale application in industrial settings.

Currently tons of dye produced per year, about the one sixth tons are converted into wastewater in various industries such as textiles and dyeing, which are among the toxic, carcinogenic and mutagenic wastes due to the presence of aromatic rings in their structure. This issue has attracted a lot of attention to the purification of such compounds. Ozone is one of the strong oxidizers which produces non-toxic compounds due to its decomposition. Ozone can convert many organic materials into simpler compounds through both direct and indirect oxidation mechanisms, including degradation of wastewater that contains double bonds components such as aromatic compounds and dyes. The purpose of this study was to investigate modeling, optimization and the interactions between parameters affecting the ozonation process in removal of Acid Orange 7 in order to achieve the highest removal efficiency for the highest possible initial dye concentration under the lowest ozone injection rate, no change in initial wastewater pH and the shortest reaction time by the use of response surface method. The RSM was performed using 4 parameters pH, initial dye concentration, ozone injection rate and time with 5 levels which ends up in 30 experimental tests. The results showed that correlation coefficients and adjusted correlation coefficients were 96.85 and 94.92, respectively, and p-value for model (less than 0.0001) and lack of fit (0.0507) were obtained as significant and non-significant, respectively. These results indicate the consistency and high reliability of the modeling results. Normal error, error independence and variance stability control were also checked which showed that the closeness between the actual and predicted values and the uniform distribution of the results obtained on the normal line indicates the uniform distribution of the error. The results and predictions of the software, the random distribution and distribution of the results indicate the suitability of the assumption considered by the software regarding the stability of the variance. Based on variance stability control, the effect of the experiments on the responses provided by the software. If one of the experiments is outside the range, this experiment will have a negative impact on the overall results of the software. In the case of experiments performed, this control was also well performed. Based on model equation the most important parameters are the injection rate of ozone (Q(O3)), pH, reaction time (T) and initial dye concentration [Dye], respectively, in which all parameters except the initial dye concentration have a positive effect on dye removal efficiency. After the related tests the optimum condition were the initial dye concentration of 480 mg/L, pH of 7.7, ozonation rate of 0.6 L/min and ozonation duration of 60 min which resulted in 90% dye removal efficiency. It was also found that the most effective factors were injectable ozone rate, time, pH, and dye concentration, respectively. The results showed that determining the appropriate domains can be of great importance in achieving the desired results from the response surface method. Also, the ozonation process is able to purify the dye from high initial concentrations to high removal efficiency, indicating the high strength of this applied process in the decomposition of complex organic compounds. Ozonation kinetic rate is based on pseudo first order which was increased from 0.3 to 0.6 by enhancing injected ozone rate from 0.2 to 0.6 L/min respectively and further increase of ozone injection rate didn’t had any effect on its kinetic rate.

Toluene is one of the volatile organic compounds and used extensively in industrial processes. Because of toluene effects on human health and environment, it is necessary to implement methods for toluene removal from contaminated air stream. Catalytic ozonation process (COP) is one of the emergent technologies for removal of volatile compounds from air streams. Catalytic ozonation process is an efficient, cost-effective and easy to operate for elimination of organic compounds. One of the main factors directly affecting the VOC removal efficiency and ozone destruction rate is the type of catalyst. In this study the potential of MnO/GAC and MgO/GAC catalysts was investigated for toluene elimination from air stream in the presence of ozone in a lab scale.
The MnO/GAC and MgO/GAC catalysts were prepared by Sol-gel method and then characterized by BET, XRD and SEM analysis. Specific concentrations of toluene in the air were produced by using an air pump and a syringe pump. Phocheck was used to measure the concentration of toluene in gas phase. The effect of retention time (0.5-4 Sec), inlet toluene concentration (100-400 ppmv) and air temperature (25-100˚C) were investigated on catalysts efficiency in the presence of ozone. Ozone dosage (0.1 g/h) kept constant in all experiments. The efficiency of MnO/GAC and MgO/GAC were determined from the breakthrough time and removal capacity and the results were compared statistically.
The BET surface area derived from N2 adsorption- desorption isotherms. From the results the BET surface area of MnO/GAC (1103 m2/g) was greater than that of MgO/GAC catalyst (1082 m2/g). XRD patterns clearly illustrate formation of MgO and MnO crystals on GAC surface. From XRD patterns the peaks at 2θ degrees of 50.3° and 73.8° were related to the MgO crystals. The peaks at 2θ degrees of 42.1°, 51.8° and 70.9° reveal the formation of Mn3O4. The crystallite phase of MgO and MnO was hexagonal and tetragonal respectively. The average size of MgO and MnO crystals was 10 and 12 nm, respectively, calculated using Debby-Scherrer equation. Results of experiments in different retention times showed that breakthrough time of MnO/GAC and MgO/GAC catalysts increased 11.3 and 13.9 times, respectively, by increasing retention time from 0.5 to 4 Sec. When inlet toluene concentration increased from 100 to 400 ppmv, the breakthrough time of MgO/GAC and MnO/GAC columns decreased 65% and 62.2%, respectively. In contrast, removal capacity of MgO/GAC and MnO/GAC was increased 39.1% and 50.4% by increasing inlet toluene concentration from 100 to 400 ppmv, respectively. The efficiency of MgO/GAC and MnO/GAC catalysts was increased 78.3% and 31.5% by increasing air temperature from 25 to 100 ˚C, respectively. These results demonstrates that increase of retention time and bed temperature could positively effect on the performance of MgO/GAC and MnO/GAC catalysts in toluene removal from waste air stream in the presence of ozone.
It can be concluded that MgO/GAC and MnO/GAC catalysts had high potential in VOCs removal from air stream in the presence of ozone. The difference between the efficiency of MgO/GAC and MnO/GAC catalysts was significant (P ≤ 0.05) and MgO/GAC catalyst had higher efficiency than MnO/GAC for toluene removal from waste air in the presence of ozone.

There are different methods for treatment of composting leachate. Parameters dictating whichmethod to be chosen include quantity and quality of the leachate, required amount of treatment and economical issues. Integration of ozonation and GAC adsorption into a singleprocess is one of the attractive methods for post treatment of wastewater. Therefore, post treatment of composting leachate by means of ozonation and granular activated carbon (GAC) adsorption was considered as the main objective of this study. This study was conducted in laboratory scale and in batch mode. The set-up of batch system consisted of a Plexiglas column with 20 mm inner diameter and 800 mm height. The tall height of the column provides the required contact time between ozone and pollutants. Ozone was supplied to the column through a diffuser sited at its bottom. The outlet gas of the reactor may contain some residual ozone and can cause air pollution. Therefore, it is dangerous for the people working nearby the reactor. Thus, the ozone in the gas phase leaving the column was removed by KI solution. All experiments were conducted at room temperature (24 ±2°C). The leachate used in this study was obtained from the effluent of the Leachate Treatment Plant of Rasht Composting Facility (Guilan, Iran). All the chemicals employed for analysis were analytical grade and obtained from the reliable companies. In order to conduct the experiments, after complete determination of the specifications of GAC as an adsorbent, different dosages of GAC were added to 800 mL of leachate with the given initial concentration and pH in the column. The pH value of the solution was adjusted by Sulfuric Acid or Sodium Hydroxide as needed. Then the ozone gas was introduced into the olumn and the samples were taken in different intervals of time. After that required parameters of the samples were measured. Ozone generator (ARDA-COG 5S) with 5 gr/hr nominal capacity was used to produce ozone gas from pure and dry oxygen. Before starting each step of the experiment, the ozone generator was calibrated for ozone concentration. Pressure and flow rate of ozone gas produced was equal to 2 bara and 1 liter per minute, respectively. The results showed that integrated treatment of the leachate with ozonation and activated carbon adsorption, namely catalytic ozonation, was more effective than each process solely. In this study, COD removal rate of 44% in adsorption process, 57% in ozonation process and 80% in integrated process was achieved after 60 minutes. According to the results, in the integrated process, addition of the adsorbent (as long as it floats in the leachate) has positiveeffect on the removal of organic load. The pH value is another important parameter that affects the removal rate in the integrated process. It was found that removal of organic load is ore evident at basic condition than at acidic condition. In this study, the maximum COD removal was achieved in the pH values between 8 and 9. Furthermore, in this process,ozonation along with adsorption process resulted in reactivation of activated carbon andavoided frequent GAC regeneration. After 5 times of the reuse of virgin GAC through a consecutive experiment, only 7% loss in COD removal was observed in the integrated process, while it reached to 95% for single adsorption process at the same condition. This can be explained either by the predominance of catalytic reactions rather than adsorptionoxidation reaction in the process or to the in situ regeneration of GAC.