Adsorption of phenol from aqueous solution by four types of modified attapulgites

To study the adsorption of phenol by various modifications of attapulgite, four modifiers (hydrochloric acid, octadecyl trimethyl ammonium chloride, nitrilotriacetic acid and ethanediamine) were chosen and the phenol removal properties of the aqueous solution were explored. All modified attapulgite samples were characterized by SEM and FTIR, which revealed that the modified attapulgites had different surface structures and that the modifier groups successfully grafted onto the surface of the attapulgite. Effects of dosage, pH, the concentration of sodium ions and temperature on the adsorption capacity were evaluated. In this experiment, phenol removal was maximized at an adsorbent's dosing concentration of 200 g L⁻¹. The sorption kinetic data could be well represented by a pseudo-second-order model. The Langmuir equation agrees very well with the equilibrium isotherm. The findings herein suggest that octadecyl trimethyl ammonium chloride modified attapulgite may be a cost-effective and highly efficient material for phenol removal, with removal rates of more than 90% in aqueous solutions with low concentrations of sodium ions, at room temperature and a pH of 3. In conclusion, octadecyl trimethyl ammonium chloride modified attapulgite was superior to other forms of attapulgite as a phenol absorbent.