Removal of 2-chlorophenol from aqueous solution by Mg/Al layered double hydroxide (LDH) and modified LDH

Sorption is a common treatment for removing pollutants from natural environments. Layered double hydroxides (LDHs), which consist of brucite-like positive layers and sodium dodecyl sulfate intercalated with LDH (SDS-LDH), are considered to be potential organic pollutant sorbents. The objectives of this study were (1) to evaluate the impact of removing 2-chlorophenol (2-CP) using Mg-3-Al-(NO3) LDH and SDS-LDH and (2) to investigate the removal efficiencies of these two compounds. All fitted sorption data reveal that the second-order model and the Langmuir model best describe the sorption kinetics and isotherms, respectively. By Visual MinteqA2 (2000) calculation, the dissociation pK(a) of 2-CP is 8.56. The experimental results indicate that a high concentration of 2-CP is sorbed by the hydrophilic-hydrophilic physical interaction of LDH when the pH is > 8.56; however, the hydrophobic-hydrophobic partition interaction of SDS-LDH is more vital when the pH is < 8.56. LDH and SDS-LDH can be removed,not only in the ionic form, but also in the molecular form of 2-CP. The efficiencies of LDH and SDS-LDH, in regard to enhancing 2-CP sorption, are strongly dependent on the pH, 2-CP speciation, ionic strength, and metal dissolution. These results are of practical interest, with respect to the selection of sorbents, to optimize aquatic environment remediation technologies.