Competitive adsorption behaviors, characteristics, and dynamics of phenol, cresols, and dihydric phenols onto granular activated carbon

Abstract

Although activated carbon is an effective tool for adsorbing phenolic compounds, it has not been systematically studied in the adsorption of phenolic compounds in the multi-component solutions. Adsorption characteristics and kinetics of phenol, o-, m-, p-cresol, catechol, hydroquinone, and resorcinol onto granular activated carbon were examined in single- and multi-component solutions. Results indicated that the adsorption rate constants decreased in the order of p-cresol >o-cresol > catechol > resorcinol >m-cresol > hydroquinone > phenol in single-component solutions. The pseudo-second-order model was better than the pseudo-first-order model for fitting the experimental data in the multi-component solutions. The adsorption rate constants of dihydric phenols isomers decreased dramatically when the solutions contained phenol and cresol isomers. Resorcinol exhibited a significant promoting effect on adsorption capacities of cresol isomers. The adsorption capacities almost obeyed the following sequence of (catechol, hydroquinone) > cresol isomers > (resorcinol, phenol) in the multi-component solutions. The distribution constants (bi) of phenol were 3.169, 3.175, and 3.249, respectively, in the ternary solutions, which were significantly higher than the values of other two components (No. 1, o-cresol 2.951, catechol 2.893; No. 2, o-cresol 2.864, resorcinol 2.977; No. 3, o-cresol 2.918, hydroquinone 2.861). Results also demonstrated the solubility and functional groups of phenolic compounds might play a key role in their competitive adsorption capabilities in multi-component solutions.