ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Response surface methodology for heavy metals removal by tioglycolic-modified Zn–Fe layer double hydroxide as a magnetic recyclable adsorbent

Farnaz Movahhedi, Akram Maghsodi, and Laleh Adlnasab

Department of Cellulosic Materials and Packaging, Chemistry and Petrochemistry Research Center, Standard Research Institute (SRI), Karaj, Iran

E-mail: laleh_adlnasab@yahoo.com

Received: 26 December 2019  Accepted: 30 March 2020

Abstract:

A new nanoadsorbent was synthesized through intercalation of thioglycolic acid (TGA) in the magnetic layered double hydroxide nanocomposite (Fe₃O₄/Zn–Fe LDH/TGA) and used for the removal of heavy metal ions such as Hg²⁺ and Pb²⁺ from aqueous solutions. The morphology and structure of the synthesized nanoadsorbent were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. Also, the quantitative measurements of metal ions were determined using atomic fluorescence spectroscopy. The simultaneous impact of important parameters on the Hg²⁺ removal including pH, adsorbent dosage and removal time were investigated using response surface methodology. Based on the obtained results, pH 5.5 was achieved, and also 9 mg as adsorbent dosage and 30 min for removal time were selected as optimum conditions in Hg²⁺ removal experiments. The adsorption kinetic results fitted well with the pseudo-second-order model, and the R² value = 0.991 while the estimated q_e was matched well with the experimental data. Thermodynamic results showed that the adsorption process of Hg²⁺ was endothermic, feasible and spontaneous. Also, the efficiency of the magnetic nanocomposite was investigated for adsorption of the metal ions. The selectivity experiments showed the following order: Hg²⁺ ⋙ Pb²⁺ > Fe²⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺. Finally, the obtained results verified the excellent ability of the magnetic nanoadsorbent for Hg²⁺ removal from the aqueous media for at least three times recycle with 90% recovery.

Keywords: Heavy metals; Magnetic layered double hydroxide; Central composite design (CCD); Thioglicolic acid (TGA)

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01149-7

Chemical Papers 74 (9) 3169–3182 (2020)