Ultrathin dodecyl-sulfate-intercalated Mg-Al layered double hydroxide nanosheets with high adsorption capability for dye pollution

Abstract

A high-performance dye adsorbent of ultrathin dodecyl-sulfate (DS^-) intercalated Mg-Al layered double hydroxide nanosheets (DI-LDH Ns) were controllably synthesized by a simple one-step surfactant-assisted hydrothermal method. The unique intercalated structure with week interlayer interaction and high accessible surface of DI-LDH Ns provide efficient adsorption of methyl orange (MO), leading to its superior performance with much higher uptake capability (846.6 mg/g at 298 K) and less adsorbing equilibrium time (5 min) than those of ultrathin DS^--surface-modified Mg-Al-LDH nanosheets (DM-LDH Ns, 327.4 mg/g at 298 K, 120 min) and original Mg-Al-LDH (O-LDH, 208.2 mg/g at 298 K, 120 min). The composition and structure of these LDHs were investigated by systematic physicochemical characterization, such as XRD, TEM, FT-IR, BET and TGA. The adsorption behavior of DI-LDH Ns follows the Langmuir isotherm equation. A plausible mechanism is proposed to explain the adsorption process of such DI-LDH Ns, in which the synergistic contributions of surface and interlayer adsorption between DI-LDH Ns and MO play an important role. This study puts forward a new thought for the development of high-performance LDH adsorbents with an ultrathin intercalated structure for the efficient and rapid removal of dyes.

Keywords: Adsorption; Adsorption mechanism; Intercalation; Layered double hydroxide; Methyl orange; One-step synthesis; Ultrathin.