Efficient adsorption of Pb(II) by sodium dodecyl benzene sulfonate intercalated calcium aluminum hydrotalcites: kinetic, isotherm, and mechanisms.

Two novel adsorbents of CaAl-LDHs and sodium dodecyl benzene sulfonate (SDBS) intercalated CaAl-LDHs (SDBS-CaAl-LDHs) were successfully prepared by co-precipitation. The main composition and physical properties of two samples were characterized by XRD, XPS, FT-IR, TG, and SEM. Batch adsorption experiments were conducted to study the effect of pH, adsorption time, and initial concentration of Pb. The results showed that the prime adsorption conditions obtained were pH of 5.2 after 60 min with the initial concentration of 300 mg g for CaAl-LDHs and 350 mg g for SDBS-CaAl-LDHs. At 303 K, the adsorption capacities and removal rates of CaAl-LDHs and SDBS-CaAl-LDHs were found to be 456.05 mg g, 91.21% and 682.26 mg g, 97.47%, respectively. For CaAl-LDHs, the kinetic data for Pb was best fitted with pseudo-2nd-order model, and the adsorption isotherms followed Langmuir and Freundlich isotherm model. The adsorption data of SDBS-CaAl-LDHs can be best described by the pseudo-second-order kinetic and Langmuir model. The Pb adsorption mechanism on SDBS-CaAl-LDHs was explored by XRD, XPS, and SEM, and the important roles of the electrostatic attraction, precipitation, complexation, and ion exchange were demonstrated. The Langmuir adsorption capacities for SDBS-CaAl-LDHs were 797.63, 828.76, and 854.29 mg g at 293 k, 303 k, and 313 k, respectively. Thus, SDBS-CaAl-LDHs may be a highly economical adsorbent for the treatment of contaminated water.