Comparison and characterization of chemical surfactants and bio-surfactants intercalated with layered double hydroxides (LDHs) for removing naphthalene from contaminated aqueous solutions

Abstract

Chemical surfactants or bio-surfactants intercalated into layered double hydroxides (LDHs) are considered as potential organic pollutant sorbents. This study evaluates the effects of (1) using either calcined or uncalcined LDH, and various solid/solution ratios, (2) the concentrations of the chemical surfactant sodium dodecyl sulfate (SDS) or the bio-surfactant rhamnolipid (RL), and (3) reaction temperatures and times on the synthesis of SDS-LDH and RL-LDH. Small angle X-ray diffraction (SAXRD) and X-ray diffraction (XRD) patterns reveal that using 1000 mg L −1 RL intercalated 2:1 uncalcined LDH with 3 days reaction time, 0.5 g L −1 solid/solution ratio, and temperature of 65 °C to synthesize the RL-LDH, containing more organic carbon content, showing larger interlayer distance than SDS-LDH. RL-LDH shows subsequent higher efficiency of naphthalene sorption than SDS-LDH, depending on higher organic carbon contents and larger interlayer distance of RL-LDH. Since RL-LDH is environmentally friendly chemical, these results are of practical interesting in RL-LDH could be potentially employed as a sorbent for removal organic contaminants from aqueous solutions, and particularly in optimizing aquatic environment remediation technologies.