International Journal of Environmental Health Engineering
Volume:5 Issue: 2, Jun 2016

 The sonoelectrochemical mineralization of the synthetic aqueous solution of the perfluorooctanoic acid (PFOA) on Ti/PbO 2 anode was investigated using the response surface methodology based on a central composite design (CCD). 

 The CCD was performed using three different variables such as current density (CD) (mA/cm 2 ), pH, and supporting electrolyte (EL) concentration (mM). The total organic carbon (TOC) removal was determined as an indicator of PFOA mineralization. A Shimadzu TOC analyzer was used to measure the TOC of the samples. The Ti/PbO 2 electrode was prepared using the electrochemical deposition method. In order to enhance the electrochemical mineralization, ultrasonic (US) radiation was used. The US frequency was 20 kHz. 

 The optimum conditions for PFOA mineralization in synthetic solution were EL concentration of 94 mM, pH of 2, and CD of 83.64 mA/cm 2 , which resulted in complete TOC removal. The results indicated that the most effective factor for PFOA mineralization was CD. Besides, the TOC removal efficiency significantly increased with increasing CD. 

 Under optimum conditions, the mineralization of PFOA was almost completed after 90 min of sonoelectrolysis. Therefore, sonoelectrolysis was found to be a more effective technique for mineralization of an environmentally persistent compound.

 The purpose of the present work was to consider the effect of different samples thicknesses on the acoustic absorption coefficient. 

 An impedance tube was built with two microphones accordance to ISO-10534 and the American Society for Testing Materials-E1050 standards. For the measurement of absorption, the study was carried for 25 and 30 mm thicknesses of closed cell polyurethane foam, polystyrene, polyvinyl chloride (PVC), rubber, mineral wool, carpet, and glass samples. Measurements were performed by impedance tube and VA-lab4 software. 

 In carpet and mineral wool with more thickness, the absorption was increased but, the carpet with less thickness showed more sound absorption in the frequency range of 1500-3600 Hz. The peak of the absorption coefficient of 25 mm glass was 0.36 that the amount was reduced to 0.2 in the 30 mm thickness. Furthermore, the difference between the peak absorption of two thicknesses in polystyrene sample was equal to 0.29. In fact, polystyrene with less thickness had better sound absorption. The same situation was happened for glass in frequencies of below 4500 Hz with less thickness. 

 Incident sound energy, which is not absorbed, must be reflected, transmitted, or dissipated. The porous materials had a higher absorption coefficient. Carpet and mineral wool samples had the highest absorption coefficient, but the materials such as polyurethane foam, PVC, and rubber had lower sound absorption.

 In present study, the mass transfer-reaction kinetic parameters of nitric oxide (NO) removal by ultraviolet (UV)/H 2 O 2 process in a bubble column reactor in the presence of SO 2 are calculated. 

 The mass balance equation for NO through a layer thickness of δ, under the steady state condition is solved, and NO absorption rate is calculated. The value of rate constants and Ha numbers are obtained based on experimental data under different conditions. 

 The calculations indicate that the values of Ha number are >3. The values of rate constants (k obs) are fitted to some empirical equations for different operating conditions. It is observed that the value of k obs increases with an increase in H 2 O 2 concentration and UV radiation intensity while it decreases with an increase in NO and SO 2 inlet concentrations. The values of rate constants are in order of 10−5 , expect for SO 2 , which are in order of 10−7 . The results reveal that there is a good agreement between calculated and experimental values where the maximum absolute error is 16.18% related to UV light intensities between 0 and 0.012 W/m 3 . 

 The obtained values of Ha numbers under different condition confirm that the absorption process of gas in the liquid phase is a fast reaction. The maximum error values resulted from a comparison between the calculated NO absorption rates and the experimental ones are acceptable.

 This research was conducted to measure the concentration of asbestos fibers in the ambient air of high traffic areas of Isfahan and to evaluate their spatio-temporal variation during summer 2015. 

 Air samples were collected from eleven points covering traffic areas of the Isfahan city including Enghelab square, Azadi square, Bozorgmehr bridge, Ghods square, Ahmedabad square, Artesh square, Emam Hossein square, Nazar junction, Vafaei junction, Felezzi bridge, and Tayyeb fork during 3 months of summer 2015. Scanning electron microscope (SEM) coupled to an energy dispersive X-ray system was utilized to count and identify the asbestos fibers. 

 Seasonal average concentration of airborne asbestos fibers in the studied region was 10.04 ± 4.90 SEM f/l. The results of this study showed that the highest concentration of asbestos fibers was measured in Azadi square (18.08 ± 3.863 SEM f/l) and that the lowest was found in Nazar junction(3.92 ± 1.749 SEM f/l). There was a significant correlation between the concentration of asbestos fibers and atmospheric temperature and humidity (P < 0.05). The mean concentration in September was higher than August and July (11.08 ± 4.66). 

 Heavy traffic in the dense areas of the city, and topographical and meteorological features of the city have a major contribution in asbestos fiber emission which resulted in its exceeded levels from the WHO guideline (2.2 SEM f/l). Therefore, effective strategies such as traffic management, industrial movement, and products replacement can be effective in reducing airborne asbestoses fibers concentrations.

 Levels of asbestos fibers in ambient air of dense areas of Shiraz, Iran, were monitored in winter 2014. 

 Sampling was carried out by directing air flow to a mixed cellulose ester membrane filter mounted on an open-faced filter holder using a low flow sampling pump. Fiber counting on the filters was conducted using both phase contrast microscopy (PCM) method to determine total fibers and scanning electron microscopy (SEM) method to identify nonasbestos from asbestos fibers. 

 The average concentration of asbestos fibers in the ambient air of the study in different areas of Shiraz were 1.18 ± 0.28 PCM f/L and 13.64 ± 2.87 SEM f/L, in which a maximum level was measured in Valiasr square (1.89 ± 0.54 PCM f/L [20.37 ± 5.55 SEM f/L]), and that of in Moallem square was in minimum (1.05 ± 0.47 PCM f/L [12.24 ± 3.04 SEM f/L]). 

 The averages of asbestos fibers in all sampling points were higher than the WHO suggested standards for ambient air (0.05 PCM f/L, 2.2 SEM f/L). This may be attributed to the frequent occurrence of heavy traffic, the existence of relevant industries in and around the city, and the topographic characteristics of the city. Therefore, immediate courses of action such as product substitution, traffic smoothing, and industrial sites relocating should be taken to eliminate asbestos fibers emission.

 In this study, the adsorption capacity of dried anaerobic digested sludge (DADS) and dried activated sludge (DAS) for the removal of 4-chlorophenol (4-CP) from aqueous solutions was evaluated. 

 Both anaerobic digested sludge and activated sludge were collected from a south municipal wastewater treatment plant in Isfahan. Batch biosorption experiments were carried out to investigate the effects of solution pH, contact time, biosorbent dosage and initial concentration of 4-CP. The residual concentration of 4-CP was analyzed by colorimetry method. Isotherms and kinetic equations were applied to study kinetic and equilibrium of adsorption. 

 Results indicated that, DAS have higher removal potential in comparison with DADS. The optimum pH was detected to be 3 for DADS and 4 for DAS. By increasing contact time and biosorbent dosage, removal efficiency of 4-CP increased for both biosorbents. Furthermore, a decreasing trend was observed when initial concentrations were increased. The equilibrium time for DAS was 2.5 h and for DADS was 4 h. The maximum adsorption capacity were found 1.67 mg/g for DAS and 0.93 mg/g for DADS. The 4-CP removal equilibrium isotherm was modeled by Freundlich equation. Kinetic studies suggested that pseudo-first-order model for DADS and second order for DAS were the best choices to describe biosorption behavior. 

 According to the present study, DAS, have better efficiency for the removal of 4-CP in comparisons with DADS.