Competitive adsorption of benzoic acid and p-nitrophenol onto activated carbon: isotherm and breakthrough curves

Three series of batch tests at 25°C were performed to determine the benzoic acid and p-nitrophenol (PNP) binary adsorption isotherms onto GAC in the aqueous solutions and the experimental data were fitted to the extended Langmuir isotherm model successfully. The experimental data and the isotherm model parameters showed that the GAC used in this study had a higher affinity to PNP than benzoic acid. Three column tests were performed to determine the breakthrough curves and effluent solution pH with varying feed compositions. According to the experimental results, the weakly adsorbed BA exhibited an intermediate zone of effluent concentration higher than its feed one; the effluent solution pH could serve as a good indicator for breakthrough. The breakthrough curves with varying feed compositions could be predicted by the non-linear wave propagation theory satisfactorily. Only the adsorption isotherm models were required to construct the composition path diagram with which the breakthrough curves could be predicted.