Mg–Al–CO3 hydrotalcite removal of persistent organic disruptor — Nonylphenol from aqueous solutions

Abstract

The paper addresses study of adsorption of widely used and persistent ionic surfactant nonylphenol (NP) onto Mg–Al–CO3 hydrotalcite (HT) and its calcined form (cHT). A combination of experimental techniques (gas chromatography, X-ray diffraction, and FTIR spectroscopy) was used for the characterization of adsorption products and for determination of the residual concentration of NP in the aqueous solution. NP deprotonation at equilibrium pH (7.22 for HT and 9.43 for cHT) was negligible. Adsorption efficiency of HT and cHT in the range 88.3–92.9% was achieved. It was found that for HT and cHT, the same adsorption mechanisms is applied, and depends on the initial concentration of NP in the solution. For the initial concentration c0<3mgdm−3 the mono-layer adsorption occurs as a result of the polar interaction of the phenolic group of the NP — positively charged surface of HT or rehydratable cHT, whereas for c0≥3mgdm−3 multi-layered adsorption prevails. Intercalation of NP into the interlayer space of HT and cHT was not confirmed. The saturation capacity of HT and cHT in the event of the mono-layered adsorption was set at 1.80mgg−1. The physical nature of the adsorption suggests the possibility of easy regeneration of the adsorbent, and thus its reuse.