Packed-bed adsorption of phenol and 2,4-dichlorophenoxyacetic acid on the macroreticular resin XAD-7.

摘要

The objective of this research is the study of the adsorption of phenol and 2,4-dichlorophenoxyacetic acid on the macroreticular resin XAD-7. The research was divided into the following parts: experimental work including batch and continuous flow adsorption to determine both the equilibrium isotherms and the adsorption rate-controlling mechanisms in the packed bed system. Experimental breakthrough curves were measured for both adsorption and regeneration and various kinetic models examined.; The parameters studied were: adsorbate initial concentration, temperature, bed height and flow rate. Equilibrium isotherms for each component at 25, 40, and 50 degrees centigrade was obtained and modelled. Experimental data were also obtained for equilibrium adsorption of a mixture of the acid and phenol on the resin. Analysis of the data revealed that the adsorption of the individual components was unaffected by the presence of the other one at the loadings studied.; A differential approach was used for the calculation of the mass transfer coefficients and the rates of adsorption. The data were tested for external, internal and second-order surface kinetic resistances. The reversible second order kinetics model gives the best fit in the case of the DPCA acid, and external diffusion appears to be the rate controlling step in the adsorption of the phenol.; The heat of adsorption was calculated from the data. It was found to be of the same order of magnitude as the latent heat of condensation of each adsorbate.