Studies regarding the benzene, toluene and o-xylene removal from waste water [articol]

Abstract

The consequences of pollution are more and more present, and are reflected especially in the public health, in the bio-diversity and balance of the ecosystems, by putting them in danger. Volatile organic compound (VOC) is defined as any organic compound of artificial origin, other than methane, able to generate photochemical oxidants in reaction with nitrogen oxides and in the presence of solar radiation. In the present paper, were studied the possibilities of benzene, toluene and xylene (BTX) removal from waste waters by air-stripping and adsorption on active charcoal. It was also investigated the possibility of using UV-VIS spectrophotometry as analysis method for BTX. We found that benzene, toluene and o-xylene dissolved in aqueous solutions can be analyzed by UV-VIS spectrophotometry; they present a very good absorbance in the wave length range 200-220 nm (benzene 190-212 nm). The BTX removal by air-stripping was studied for various air flow rates (20, 40 and 100 L/h). BTX removal degree increases with the increase of air flow rate; for all flow rates the removal degrees were higher than 96%. The removal of BTX from waste water by adsorption on active charcoal was studied using a column containing 4 g of granular active charcoal. The efficiency of the adsorption process was studied for three various water flow rates: 1 L at a flow rate of 0.26 L/h, 5 L at 1.66 L/h and 5 L at 3.65 L/h. BTX removal degree decreases as the waste water flow rate increases, and they are smaller than the removal degrees reached by air-stripping, due to the quantity, the sort of the used charcoal (granular), and the design of the adsorption column, which allowed the formation of preferential flow channels, especially at higher flow rates.