The Removal of Trace Organic Impurities from Water using Activated Charcol Cloth

Abstract

In order to study the removal of trace organic compounds from water using activated charcoal cloth, phenol and 2 chlorophenol were chosen as typical organics, due to their widespread dissemination in the environment as toxic pollutants and the availability of relevant detailed information about them. The adsorption capacity of the cloth was found, using the Freundlich isotherm, to be between three and four times greater than for granular charcoal, under normal conditions. In order effectively to model a system using charcoal cloth, it was necessary to establish the kinetics of adsorption on the cloth. Film diffusion could be neglected in a sufficiently turbulent, well-stirred reactor. Electron micrographs of the cloth surface had indicated that most of the porous structure of the cloth consists of micropores. Hence, phenol could only adsorb onto the surface, or into longitudinal surface corrugations. Therefore, pore transport was assumed to be negligible and adsorption to be surface-reaction-controlled. The experimental apparatus constructed for this study consisted of three well-stirred reactors, through which a continuous length of charcoal cloth was transported, countercurrent to the flow of polluted water. The cloth was then passed through a regenerator containing two 1 KW heaters, where it was reactivated and then returned to the adsorption section. It was discovered that the regeneration process was more efficient with only one heater operating; this was thought to be due to the lack of formation of surface carbon and the presence of steam formed from water on the cloth surface. Experimental results indicated that it was possible, using the continuous apparatus, to remove 90% phenol and 98% 2-chlorophenol from water, at steady state. The adsorption of phenol, at steady state, was successfully modelled using surface-reaction-controlled kinetics.