Adsorption and co-adsorption of chlorophenols and Cr(VI) by functional organo-vermiculite: Experiment and theoretical calculation

Abstract

• An imidazole-ether-containing gemini surfactant is used for modifying Na-Vt. • Rapid and efficient removal of TCS/4-CP/Cr(VI) (220.1/74.6/18.4 mg/g) is achieved. • Antagonistic effect is clarified in TCS-Cr(VI)/4-CP-Cr(VI) co-adsorption system. • The more preference of BDIEP-Vt to TCS is based on its structural characteristics. • Experiment, calculation and characterization are combined for the mechanism. The functionalized organo-vermiculite (BDIEP-Vt) is prepared by combining the imidazole-ether-containing gemini surfactant into vermiculite, and serves as adsorbent for single and simultaneous removal of triclosan (TCS), p -chlorophenol (4-CP) as well as Cr(VI) from aqueous solution. The physicochemical properties of the resultant BDIEP-Vt are characterized via FT-IR, XRD, TG-DTG, SEM, TEM as well as BET analysises. In single system, the results of standard batch adsorption experiment represent that BDIEP-Vt could adsorb the three contaminants (220.4 mg/g for TCS, 74.6 mg/g for 4-CP, 18.4 mg/g for Cr(VI)) effectively as well as rapidly within 5–10 min. The adsorption process is in great pertinence with pseudo second-order model, and the equilibrium data are befitted Freundlich model greatly for TCS and Cr(VI), while Langmuir model suites for 4-CP. In TCS-Cr(VI)/4-CP-Cr(VI) binary system, the maximum adsorption capacity of BDIEP-Vt for TCS, 4-CP as well as Cr(VI) is 182.1, 44.1 and 12.7 mg/g, respectively. The trend variation of φ value indicates an antagonism effect is exerted by Cr(VI) ions on TCS/4-CP removal whereas Cr(VI) uptake is slightly affected. Interestingly, the impact sequence of Cr(VI) on the removal of TCS/4-CP follows as: TCS < 4-CP. The adsorption mechanism is clarified by means of the characterization of spent adsorbent together with theoretical calculations: (i) Expect for hydrophobic interaction, the adsorption of TCS/4-CP is mainly driven by π-π along with π-π stacking interactions; (ii) Both π-π (betwixt imidazole ring and orthogonally benzene) and π-π stacking interactions (among the orthogonally benzenes) are more stronger than imidazole-isolated benzene/isolated benzene-isolated benzene systems; (iii) The removal of Cr(VI) is controlled by electrostatic interaction. The study proves that BDIEP-Vt as an effective multifunctional adsorbent has a momentous application prospect in potential environmental remediation.