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Background: Fixed bed adsorber as a controlling method for volatile organic compounds is widely used. However, these adsorbers are facing some issues such as high pressure drop, non-uniformed distribution of fluid, channeling and blockage. Fluidized bed adsorber as a novel method solves lots of these limitations. Objectives: This research aimed at investigating factors affecting the adsorption of vapors of VOCs on fluidized bed adsorbers. Materials and Methods: To assess adsorption, an annular fluidized bed reactor was designed and charged with activated carbon particles with size of 50 -100 and 100 -140 American society for testing and materials(ASTM) standard mesh, respectively. To calculate the minimum fluidization velocity, Ergun equation was used. The effect of inlet concentration (400 -600 ppmv), fluidization velocity, particle size distribution and breakthrough time were investigated under a steady state. Results: Tests indicated that by increasing flow rate from 0.3 (L/min), bubbles formed in the bed and the bed's pressure drop suddenly declined. The adsorption test indicated that, when Q = 3 (L/min), the removal efficiency of activated carbon (AC) (100 -140 mesh ASTM), was nearly 100% up to 99 min and it reached zero after 260 min. For 50 -100 Mesh AC, the removal efficiency was close to 100% up to 95 min and it reached zero after 270 Minutes. The results also indicated that increasing initial concentration and flow rate reduces breakthrough time. However, two flow rates, 2 and 3 (L/min) Comparison, did not reveal significant differences in the removal efficiency of the bed before breakthrough time. Conclusions: Results indicated that annular fluidized bed reactor's adsorbers are useful techniques for VOCs adsorption. Comparison of two particle ranges indicates that in all concentrations and all flow rates of the experiments, smaller particle size adsorption are better. In superficial velocity above the minimum fluidization velocity, pressure drop of fluidized beds are less than the pressure drop of fixed beds. So fluidized bed systems are more applicable for smaller adsorber particles.

Background: Aromatic organic solvents are extensively used in various industries. Xylene is a colorless, transparent liquid, with the characteristic odor of the aromatic hydrocarbons family, which is widely used in industries. Adsorption is a conventional method of purifying polluted air containing volatile organic compounds (VOCs). Zeolite has many unique properties such as high capacity, molecular sieve characteristics, nonflammability, thermal stability, and strong acid sites. Moreover, it is reconstructed at low temperatures. Objectives: In this study, we investigated the effect of various parameters on the adsorption capacity of natural zeolite (clinoptilolite) for xylene adsorption. Materials and Methods: Physical and chemical properties of natural zeolites were tested by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and elemental analyses of natural zeolites were characterized by X-ray diffraction. Xylene concentration was measured at various times through concentrations-measured valve before and after the adsorbent bed reactor by the direct reading of Phocheck (Ion Science Ltd, UK). Results: Experimental results showed that clinoptilolite is a potential sorbent for xylene in the range of ppm, and the breakthrough time would be reduced by increasing the concentration. The optimal temperature of xylene adsorption on natural zeolite was 35℃ and by increasing the temperature, the absorption efficiency of clinoptilolite was declined. The results showed that the breakthrough time and the exhaustion point time at the optimal conditions are 65 and 95 minutes, respectively. Adsorption capacity of clinoptilolite was obtained as 1.69 mg xylene/g zeolite. Conclusions: Experimental results showed that clinoptilolite is a potential sorbent for xylene in the range of ppm and the breakthrough time was reduced by increasing the concentration. Adsorption rate were increased by increasing concentration of xylene. Presence of xylene molecules in high concentration enhances their transfer and contact with adsorbent; as a result, by increasing gas concentration, breakthrough time in zeolite will be shorter.

Methyl tert-butyl ether (MTBE) is added to reformulated gasoline to meet the 1990 Clean Air Act directives. Widespread use of MTBE in gasoline has resulted in groundwater contamination. Because of its undesirable effects on drinking water and ecologically harmful effects, MTBE removal has become a public health and environmental concern. In this study, we have isolated a mixed bacterial culture which is capable of degrading the MTBE as a sole carbon and energy source. This consortium was developed from mixed urban and petrochemical activated sludge after 4 month's enrichment. Enrichment was conducted in batch reactor, fitted with a screw cap and butyl rubber septum. MTBE concentration was measured in head space by gas chromatography. Degradation was determined by MTBE removal. MTBE biodegradation was depended to Dissolved Oxygen (DO) concentration and not affected by the changes in concentration of trace element solution or other stimulator Substances. Degradation rates were nearly 1.478 mg MTBE h^-1 g^-1 (wet biomass) and didn't change with MTBE concentration (up 500 mg L^-1)

AB STRACT:In this study acrylic water base color was removed from synthetic wastewater using coagulation process. Experiments were conducted on the sample containing 100 mg/L and 400 mg/L of acrylic water base color. Destruction of color by means of coagulation/flocculation techniques using ferrous sulfate, alum, lime and polyelectrolyte (cationic, anionic and non ionic).The study was performed in a systematic approach searching optimum values of alum and FeSO 4 concentration, pH and temperature. All the experiments were run in a laboratory scale .The obtained results show that treatment with alum and ferrous sulfate alone proved to be very effective in removing the color (> 99 %) and part of COD (60-70 %) from aqueous solution. Lime alone did not significant change on COD and color removal.