Adsorption Behavior of Thiophene from Aqueous Solution on Carbonate- and Dodecylsulfate-Intercalated ZnAl Layered Double Hydroxides

Enhancing the capacity and selectivity of adsorbent materials was critical for removing the sulfur-containing pollutants from industrial effluents and fuels. CO32- and dodecylsulfate intercalated ZnAl layered double hydroxides (denoted as CO3-LDH and DDS-LDH, respectively) were used as functional adsorbents for thiophene removal, and they show better absorption properties. The adsorption behavior of thiophene on them was significantly different. The first difference focused on pH dependence. The adsorption behavior onto CO3-LDH was obviously influenced by initial pH; the removal percentage of thiophene reached a maximum value at pH similar to 7. However, the adsorption capacity of DDS-LDH was influenced indistinctively by initial pH and the removal percentage of thiophene was practically constant at various pH. The second difference was the effect of initial thiophene concentration. As the thiophene concentration increased, the curve of adsorption capacity became S-type onto CO3-LDH but linear onto DDS-LDH, indicating two different adsorption processes. The adsorption behavior for DDS-LDH was proposed by the dissolution of thiophene in a three-dimensional hydrophobic interlayer region (i.e., adsolubilization), induced by the intercalated DDS, rather than a simple surface adsorption. The results suggested that DDS-LDH could be applied as a potential adsorbent for thiophene removal in a wide range of pH.