Application of microwave irradiation for the treatment of adsorbed volatile organic compounds on granular activated carbon

The purpose of this laboratory scale experimental research was to investigate the application of integrated microwave irradiation and granular activated carbon adsorption for removing volatile organic compounds [VOCs] from emissions released from industrial processes and considered major pollutants of the environment. A stream containing 300 ppm toluene was supplied and passed through the granular activated carbon [GAC]. The saturated adsorbent was placed in a quartz glass reactor and treated by microwave [MW] irradiation at heating frequency of 2450 MHz at different power levels. Adsorption capacity was evaluated through breakthrough curves and the residue analyzed by gas chromatography. Breakthrough results showed that the high relative humidity of the inlet gaseous stream could lead to decreased GAC adsorption capacity. We found that GAC could absorb microwave irradiation and dissipate heating energy increasing its temperature up to 600 Degree C in a short time mainly depending on the microwave power level. Our experimental results indicated that most of the toluene vapor passed over GAC was decomposed under 900 watt microwave irradiation after around 10 minutes. The addition of water vapor in the inlet stream slightly decreased pollutant removal rate over the GAC while the overall oxidation removal remain the same compared to stream with low content of water vapor. Adsorption isotherms showed that GAC surface area and porosity values increased slightly under microwave irradiation. We concluded that simultaneous application of GAC and microwave irradiation may be an effective approach for removing VOCs from gaseous stream

[Protective effect of N-acetylcysteine on blocking potentiation of noise induced hearing loss by carbon monoxide in rabbits]

Noise induced hearing loss [NIHL] is one of the most important occupational diseases worldwide. NIHL has been found to be potentiated by simultaneous carbon monoxide [CO] exposure. This study was performed to evaluate the protective effect of Nacetylcysteine [NAC] administration on potentiating effect of CO on NIHL in rabbits. In this experimental study forty-two male adult white rabbits were divided into seven groups [n=6 for each group]. Group 1, as control [no exposure to noise or CO and no injection]; Group 2, noise exposure [100 dB for 40 h]; Group 3, noise+CO exposure; Group 4, noise exposure+NAC administration [325 mg/kg]; Group 5, noise+CO exposure+NAC administration, Group 6, NAC administration alone and Group 7, CO exposure [700 ppm for 40h]. Audiometric test of rabbits was assessed by Auditory Brain stem Response [ABR] test in three stages: before exposure, 1 hour and 14 days post exposure at 1, 2, 4 and 8 kHz frequency. The administration of NAC attenuated temporary and permanent ABR threshold shift caused by noise exposure and simultaneous exposure to noise plus CO. NAC administration blocked the potentiating of temporary threshold shift by CO at 1, 2, and 4 KHz frequency and also blocked potentiating of permanent threshold shift by CO at all frequencies. NAC as an antioxidant agent can attenuate temporary and permanent noise induced ABR threshold shifts and provides protective effect against potentiating of NIHL by CO in rabbits