Performance catalytic ozonation over the carbosieve in the removal of toluene from waste air stream

Toluene is a volatile organic compound, one of 189 hazardous air pollutants [HAP[s]] and the most important pollutant found in most industries and indoor environments; owing to its adverse health, toluene must be treated before being released into the environment. In this research study, a continuous-flow system [including an air compressor, silica gel filters and activated charcoal, impinger, an ozone generation and a fixed bed reactor packed with the carbosieve in size 1.8-2.3 mm, specific surface: 972 m[2]/g,] was used. This glass reactor was 0.7 m in height; at a distance of 0.2 m from its bottom, a mesh plane was installed so as to hold the adsorbent. Moreover, 3 l/min oxygen passed through this system, 0.43 g/h ozone was prepared. The flow rate of waste airstream was 300 ml/min. The efficiency of this system for removal of toluene was compared under the same experimental conditions. Under similar conditions, performance of catalytic ozonation was better in toluene removal than that of ozonation and carbosieve alone. On average, increasing the removal efficiency was 45% at all concentrations. When carbosieve and ozone come together, their synergistic effects increased on toluene degradation. Catalytic ozonation is a suitable, high-efficient and available method for removing toluene from various concentrations of waste air stream. This process due to the short contact time, low energy consuming and making use of cheap catalysts can be used as a novel process for removing various concentrations of volatile organic compounds

Microwave/h[2]o[2] efficiency in pentachlorophenol removal from aqueous solutions

Pentachlorophenol [PCP] is one of the most fungicides and pesticides. Acute and chronic poisoning from PCP may be occurred by dermal absorption, and respiration or ingestion. With respect to health and environmental effects of PCP, many methods were considered re-garding its removal. Microwave assisted other methods are environmental friendly, safety, and economical method, consequently, in this study; microwave assisted with hydrogen peroxide [MW/H[2]O[2]] was used for PCP removal from aquatic solutions. The possible of PCP removal was considered by application of a modified domestic microwave. PCP removal rate was considered under different factors such as H[2]O[2] dose [0.01, 0.02, 0.1, 0.2, 0.3 mol/L], PCP concentration [100,200, 300, 400, 500, 750, 1000 mg/L], pH [3, 7, 11], energy intensity [180,450, 600W], COD [344mg/L], and scavenger testes [0.02 mol/L from each of Tert- butyl alcohol [TBA], NaCl, NaHCO[3], and Na[2]CO[3]]. The concentration changes of PCP were determined using spectrophotometer and HPLC spectra, respectively. The best PCP removal was obtained in condition of pH 11, 0.2 mol/L H[2]O[2], and 600 W energy intensity. Moreover, COD removal in this condition was 83%. Results obtained from radi-cal scavengers indicated that OH had only an initiator role, and had not a dominant role, and order reaction was in first order. The results of microwave/H[2]O[2] application showed that this process is suitable for removal of PCP and other chlorinated organic compounds in alkaline pH.

Heavy metals concentration in vegetables irrigated with contaminated and fresh water and estimation of their daily intakes in suburb areas of Hama-dan, Iran

This study was conducted to estimate the level of heavy metals accumulate in vegetables irrigated with contaminated water compared with those irrigated with fresh water in Hamadan, west of Iran in 2012. Sixty samples of different vegetables i.e., parsley, tarragon, sweat basil and leek irri-gated with contaminated water and thirty six samples from three different adjacent areas irrigat-ed with fresh water as control were analyzed to determine heavy metals. The concentration of heavy metals i.e., lead, cadmium and chromium were achieved using atomic adsorption spec-trophotometer. The mean concentration of lead, chromium and cadmium regardless of the kind of vegetables irrigated with contaminated water was 6.24, 1.57 and 0.15 mg/kg, respectively. Moreover, metals uptake differences by the vegetables were recognized to vegetable differences in tolerance to heavy metals. Based on the above concentrations the dietary intakes of metals through vegetables consumption were 0.004, 0.0008 and 6E-05 mg/day in infants for lead, chromium and cadmium, respectively. The high concentration of these heavy metals in some vegetables might be at-tributed due to the use of untreated sanitary and industrial wastewater by farmers for the irriga-tion of vegetable lands. Therefore, treating of these wastewater and bioremediation of excess metals from polluted vegetation land could be considered.

Preparation of an adsorbent from pumice stone and its adsorption potential for removal of toxic recalcitrant contaminants

In recent years, proficient treatment of wastewaters containing recalcitrant and toxic compounds such as phenol has been a challenge. This study introduced and evaluated an efficient option for treating such wastewater. This experimental study was performed on phenol removal as a recalcitrant and toxic compound in aqueous solutions in 2011. The pumice stone was collected from a local mine. Collected samples were crushed and granulated using standard sieves [mesh size of 20]. CuSO[4] was used to modify prepared samples. The chemical composition and the surface area of the modified pumice were evaluated using X-ray fluorescence and N2 gas via Brunauer-Emmett-Teller isotherm and Belsorb software. Different parameters including of pH [3-12], contact time [20-120 min], phenol concentration [25-400 mg/L] and adsorbent dosage [0.25-1 g/L] were examined in a batch reactor. 93.5% of the phenol was removed under optimum experimental conditions of pH 3 and a 0.5 g/L adsorbent dose after 60 min contact time. The experimental adsorption isotherm the best fit with Freundlich equation model. The maximum amount of phenol adsorption onto modified pumice [MP] was 15.8 mg/g. Modified pumice is effective adsorbent for the removal of phenol from aqueous solution. Accordingly, it is feasible and promise adsorbent for treating polluted phenol streams

[Application of bone char as an adsorbent for purification of water contaminated with hexavalent chromium]

Chromium is one of the most important heavy metals, which its high levels in drinking water lead to several health adverse effects. This study was performed aiming at determining the effects of primary concentration of six-valent chromium, adsorbent dosage, contact time, and pH on the adsorption of chromium from water on bone char. Bone char was prepared using electric furnace at 450°C for 2 h. Pulverizing of bone char was carried out by standard ASTM sieves with the range of 0.5-1 mm. The structural characteristics and specific surface area were determined through conventional methods. The samples' chromium concentration was measured at a wavelength of 450 nm. Adsorption isotherm of chromium was assessed by Freundlich, Langmuir, and Temkin adsorption equation models. The main component of Bone char is calcium hydroxylapatite with surface area of 100m[2]/g. In this study, adsorption reached the equilibrium at lapse of 120 min, and the increase of adsorbent dose up to 0.7g/100ml leaded to increase in the chromium adsorption. However, higher level had no effect on adsorption efficiency. The results showed optimum adsorption took place better in acidic range of pH [pH=3]. Adsorption isotherm of chromium on bone char follows the Langmuir and Temkin models, and the maximum adsorption capacity the dimensionless coefficient [RL] were 2.025 mg/g and 0.15, respectively which indicates that an appropriate adsorption of chromium on bone char. Bone char is an inexpensive adsorbent, which can be used for adsorption of chromium from water based on surface properties

Catalytic ozonation of phenol using copper coated pumice and zeolite as catalysts

Catalytic ozonation has recently been applied as a new method of contaminant removal from water and wastewater. In this study, copper coated pumice and zeolite were used to catalyze the ozonation of phenol as a target pollutant from aqueous solutions. The pumice and zeolite stone were modified by CuSO4 [1N]. Modified pumice and zeolite were characterized by Adsorption/Desorption Porosimetry [BET] and Scanning Electron Microscope analyses. Ozonation and catalytic ozonation experiments were performed in a 1 L semi-batch reactor containing a prepared phenol solution. The efficiency of catalytic ozonation was investigated by different variables: pH value, contact time, initial phenol concentration, catalyst dose, and radical scavenger. Experimental data indicated that as the pH solution increased, phenol removal increased. pH = 8 was measured as the optimum pH. The removal efficiency in single ozonation process [SOP] was 32% and in the catalytic ozonation process [COP] using modified zeolite and pumice was 51% and 63%, respectively. Moreover, these processes showed a great ability to mineralize phenol [up to 30%]. Using the radical scavenger determined the indirect oxidation as the main pathway of phenol removal in both catalytic processes. The copper modified zeolite and pumice had good performance to remove phenol through catalytic ozonation method.