Synthesis, Characterization, and Application of Zn-Al Layered Double Hydroxide as a Nano-Sorbent for the Removal of Direct Red 16 from Industrial Wastewater Effluents

In this research, nano-structured zinc-aluminum layered double hydroxide (Zn-Al LDH) was successfully synthesized by a co-precipitation method and followed by thermal treatment. The structure and morphology of the obtained material was characterized by X-ray diffraction, transmission electron microscopy, nitrogen-adsorption-desorption isotherms, and Fourier transform infrared spectroscopy. The as-prepared LDH was applied as a solid phase extraction (SPE) sorbent for the removal of direct red 16 (DR16) from aqueous solutions. A spectrophotometric method was used for monitoring of the extracted DR16 at lambda = 548 nm. The effect of several parameters such as pH, sample flow rate, amount of nano-sorbent, elution conditions, and sample volume on the removal percentage was investigated. The results showed that DR16 could be retained by Zn-Al(NO3-) LDH at pH 6 and stripped by 2.5 mL of 1.0 mol L-1 NaOH. In the optimum experimental conditions, the limit of detection and relative standard deviation were 0.003 mu g mL(-1) and 1.2%, respectively. The calibration graph using the presented SPE system was linear in the range of 0.01-2.00 mu g mL(-1) of DR16 with a correlation coefficient of 0.9994. The method was successfully applied for the removal of DR16 from several industrial wastewater effluents.