Adsorption/ion‐exchange behavior between a water‐insoluble cationic starch and 2‐chlorophenol in aqueous solutions

An investigation was undertaken regarding the removal of 2-chlorophenol from solutions using highly crosslinked cationic starch containing a tertiary amine group. The mechanism of removed 2-chlorophenol is affected by the pH of the aqueous phase. The nonionized and ionized species are removed by the adsorption and ion-exchange process, respectively. It has been found that the adsorption process predominated over the initial pH ranging from 2 to 6, the ion-exchange process predominated at initial pH 12, and both processes coexist over the initial pH ranging from 8 to 10. A method is suggested to determine the contribution of the nonionized and ionized species to remove 2-chlorophenol over the test pH range. The adsorption process is initially pH-independent, and the ion-exchange process is initially pH-dependent. The adsorption and ion-exchange processes are concentration-dependent, endothermic, and follow the Langumir isothermal adsorption. The ΔH is 2.504 kcal/mol for the adsorption process and 3.580 kcal/mol for the ion-exchange process. The ion-exchange capacity is larger than the adsorption capacity.