جستجوی مقالات مرتبط با کلیدواژه « Aromatic compounds » در نشریات گروه « فنی و مهندسی »

Pollution of aquatic ecosystems with petroleum hydrocarbons is one of the most important issues that have become challenging in recent years. Bushehr port located in Bushehr province in the south of Iran due to its connection with the Persian Gulf and having long beaches is one of the places prone to pollution related to hydrocarbon compounds. In order to investigate the concentration of aromatic compounds in the surface sediments of Bandar Bushehr beach, 27 sediment samples were collected and subjected to GC analysis. The total amount of aromatic compounds in the coastal sediments of Bushehr port fluctuates between 206 and 1463 ng/g. The largest volume of aromatic compounds is concentrated in the northern strip of the Sahel and the middle of the Sahel, and the concentration of the compounds is low in the southern strip of the Sahel. These compounds have pyrogenic and petrogenic origin, although the contribution of petrogenic origin is more. The origin of combustion compounds is the result of sea and land transportation, municipal and domestic sewage and offshore currents carrying petroleum compounds originating from the oil fields of the Persian Gulf. Based on pollution standards, the northern and middle parts of the coastal strip of the Persian Gulf in the area of Bushehr port have a medium pollution load in relation to aromatic compounds, and in the southern parts, the pollution load is low.

In this research, the application of adsorption isotherm, kinetic and thermodynamic models in a rotating disk reactor covered with graphene nanoparticles designed to remove aromatic compounds from the wastewater of the refinery located in Sari oil facilities and as a result reducing the chemical oxygen demand (COD) of the wastewater was investigated. Langmuir-Freundlich thermocouple was used to investigate the removal process. Also, adsorption kinetics were investigated by pseudo-first-order, pseudo-second-order and intermolecular diffusion models. The thermodynamics of adsorption was studied by Vant Hoff relation and its results were analyzed. Also, the effect of change in effluent concentration (70,100,150 mg/L) and temperature (20, 30 and 40˚C) and the number of discs containing graphene on the COD removal rate of the effluent was investigated. The results of the experiments showed that the rate of absorption and reduction of effluent COD increased with the increase of initial concentration and the temperature of the process and under optimal conditions was equal to 66%. From the examination of the equations, the applicability of two isothermal equations in the form of Freundlich Langmuir and models Kinetics were determined as pseudo-second order > intermolecular diffusion > pseudo-first order. From the analysis of the data, it was found that increasing the concentration and efficiency of the adsorbent has a positive effect and improves COD removal. At high concentrations, the ratio of effluent to graphene active surfaces and concentration gradients were the leading factors of absorption. The COD reduction percentages for concentrations of 70, 100, and 150 mg/L were 48%, 62%, and 73%, respectively.

In this research, it was tried to use a reactor containing plates covered with Graphene nanoparticles and placing it after the anaerobic biological treatment unit of dyeing treatment plant will reduce the pollution load for the next stages of treatment by absorbing aromatic substances resulting from the anaerobic biological destruction stage. The results of the field emission electron microscope (FE-SEM) analysis showed that the Graphene layers on the reactor plates were multi-layered. Then the effect of three parameters of effluent concentration (COD: 70, 100, 150 mg/L), pH (5, 7, 9) and temperature (20, 30 and 40 ˚C) on the amount of removal of aromatic compounds, COD and effluent turbidity were investigated. The results showed that high concentration of COD had faster and better absorption by Graphene than its low concentration. Among the three tested temperatures, a higher absorption rate was observed at the higher temperature. Also, with the increase of pH from 5 to 9, the amount of absorption increased. This system showed relatively good performance in absorbing aromatic substances and reducing COD. Optimum conditions of reactor performance were determined as COD: 150 mg/L, pH = 9 and temperature 40 ˚C.

In this study, at first, by using the experimental vapor pressure and saturated liquid volume of N-formyl morpholine, the parameters of cubic plus association (CPA) equation of state for NFM are evaluated. In this work, five association schemes (1A, 2A, 3B, 4B, and 4C) are used for NFM and the parameters of CPA equation of state are evaluated for these association schemes. Then, bubble point calculation is used for vapor-liquid equilibrium calculation in these mixtures. For this purpose, aromatics were considered as two types; in the first type, aromatics cannot cross associate with NFM and in the second type aromatics can cross association with NFM. Binary interaction parameters between aromatics and NFM were obtained and the modeling results were compared to experimental data and the best association scheme for NFM was obtained. The results show that 4C and 4B association schemes give the best results for correlating vapor-liquid equilibrium of mixtures containing aromatics and NFM.

In the past decade, the municipal and industrial solid waste production has become one of the main environmental challenges. Municipal Solid Waste (MSW) generation continues to grow both in per capita and overall terms [1]. Overall, the liquid generated due to the agglomeration, pressured and chemically interacted intosolid waste is called leachate [2]. The characteristics of landfill leachates depend on a number of complex factors, including the nature of the deposited wastes, soil characteristics, the “age” of the landfill, weather conditions such as rainfall patterns, the design and the means of operation of the landfill [3-5]. By considering the leachate characteristics, operation and capital costs as well as regulations, various site-specific treatment techniques can be used to treat these hazardous wastewaters (e.g. coagulation/ flocculation, biological, oxidation, membrane, leachate recirculation through the landfill, grassland spray irrigation, etc.) [6]. Therefore, treatment of hazardous liquidwastes by oxidation processes such as ozonation (due to high oxidative power of the ozone) has gained popularity. It has been shown that ozone is capable of destroying recalcitrant compounds in effluents and bringing about alterations to biodegradability. Mainly, Biodegradability of high molecular weight of organic compound is low, so that they cannot be removed simply through biological treatment [7]. In this study, the leachate was sampled from landfill in Anakhatoon region situated in Tabriz city. This landfill mainly is used for the disposal of municipal solid wastes. Samples were transported to the laboratory for Analyzing. Before any processing, samples were exposed to ambient temperature for 3 to 5 days to settle mud and coarse particles. The COD and BOD5 analyses were performed according to the standard methodology [8]. Absorbance of samples at wavelength of 254 nm was determined by means of UV–visible spectrophotometry (Spectroquant Pharo 300 (Merck, Germany)). Also, the absorbance value at 455 nm was measured by Spectroquant Pharo 300 using visible spectrophotometry. Some of the characteristics of the two samples of landfill leachate used in this work are presented in Table 1. 3.1. COD removal, color removal and aromatic compounds removal The reduction of COD content, the percentage of color removal and the percentage of aromatic compounds removal is shown as a function of reaction time in Fig. 2. It is clear that the maximum removal for leachates with COD0 =22000 mg/L and COD0 =1900 mg/L obtained 57.99% and 59.27%, respectively. On the other hand, in this work, ozonation effect on color change was determined by measuring absorption of samples at wavelength of 455 nm as an index. It is clear that a major part of decolonization occurred during ozonation [9]. During the current study, the initial dark brown color of the leachate sample, which can be attributed to the presence of humicsubstances, became light yellow as the oxidation reaction by ozone was preceded. Discoloration of landfill leachates is evidence of the transformation of recalcitrant organic matter by ozone [10]. Also, the absorbance of samples at wavelength of 254 nm can be directly related to the presence of aromatic and unsaturated structures of organicsubstances and it is considered as an additional quality parameter of most wastewaters. Similarly to the decolorization reactions, the reduction of UV absorbance took place by a high rate during the initial stages of ozone treatment. In this paper, by using a new reactor system contained a centrifuge pump and a venture tube, the capability of ozonation in treatment of the leachate generated in the landfill was indicated. The influences of initial COD value was studied on the COD, color and aromatic compounds removal. For leachates with COD0 =22000 mg/L and COD0 =1900 mg/L, 57.99% and 59.27% percent of COD removal, 85.15% and 94.94% percent of color removal and 39.65% and 82.71% percent of aromatic compounds removal was obtained, respectively. The changes of pH during the ozonation process were minimal because of buffering effect of bicarbonates present in the system.