Application of Mg–Al and Zn–Al layered double hydroxides modified with sodium dodecyl benzene sulfonate as a solid sorbent for removal of diazinon from water samples

Abstract

Modified sodium dodecyl benzene sulfonate Mg–Al and Zn–Al layered double hydroxides (abbreviated as Mg–Al–SDBS and Zn–Al–SDBS LDHs) were synthesized and characterized by FT-IR, TGA, XRD, BET and SEM. SEM images confirmed the platelike morphology for the synthesized LDHs, with a thickness of < 100 nm for the Mg–Al and Zn–Al LDHs modified by sodium dodecyl benzene sulfonate. This modification enhanced the abilities of Mg–Al and Zn–Al layered double hydroxides to uptake efficaciously nonionic pollutant diazinon from contaminated water solutions. The parameters affecting the extraction procedure including pH of the aqueous solution, amount of the adsorbent and adsorption time were optimized by applying the statistical technique response surface methodology. Desorption of the loaded diazinon was performed by applying acetonitrile as diluent. HPLC was used for measuring the concentration of diazinon. Under optimal conditions, the uptake capacity of diazinon and its removal percentage with Mg–Al–SDBS (26.5 mg g−1, ~ 75%) were found to be higher than Zn–Al–SDBS (22.4 mg g−1, ~ 57%). The former LDH allowed also achieving to a higher concentration factor with respect to that provided by Zn–Al–SDBS (8 vs. 3.2). It was demonstrated that the adsorption isotherms of diazinon onto both of the studied modified LDHs obeyed from Langmuir model. Intra-particle diffusion model was suitable for interpretation of the adsorption kinetics. The proposed adsorption procedures by the investigated modified LDHs were used successfully for decontamination of water samples from diazinon. The inter- and intra-day relative standard deviations for the samples (n = 3) were found to be 5.2% and 6.7%, respectively.