Phenol adsorption using Aliquat 336 functionalized Zn-Al layered double hydroxide

Phenolic compounds, which are important substances in industry, are mainly derived from coal liquefaction oil, coal tar, and petroleum, and also from biomass via pyrolysis. Phenol is considered a pollutant in the environment due to its toxicity and carcinogenic effect, therefore the removal of phenols from waters before discharge is a necessary requirement. It was found that phenol compounds could be successfully separate from various samples using extraction with ionic liquids (ILs). Several studies were done on phenol removal using layered double hydroxides (LDH) due to their efficiency to adsorb and/or intercalate anionic compounds. The present paper reports the studies regarding the phenol removal using ionic liquid functionalized Zn4Al-LDH. In this way are combined the advantageous of the IL with the properties of the LDH. As IL was used Aliquat 336-methyl mixed tri-alkyl ammonium chloride. Two methods for the functionalization of the Zn4Al LDH with IL were studied: the impregnation of the IL onto the Zn-Al LDH using the ultrasonication method and the co-precipitation. From the extensive characterization of the obtained adsorbent through SEM and EDX, RX, FTIR, BET and TGA analysis was put in evidence that the functionalization of the Zn4Al-LDH with the Aliquat 336 was realized. Equilibrium, and kinetic studies were applied in order to determine the efficiency of the studied adsorbents in the removal process of phenol from aqueous solutions. Both, the LDH and the studied IL, contribute to the increasing of the adsorption capacity of the obtained adsorbent in the removal process of phenol from aqueous solutions due to their synergic effect. Comparing the maximum adsorption capacities develop by the studied adsorbent with the adsorption capacities developed by other similar adsorbent material, reported in literature, it can be conclude that Zn4Al layered double hydroxide functionalized with Aliquat 336 is an efficient adsorbent. The maximum adsorption capacities developed by the studied adsorbents are in the following order: IL-Zn4Al > Zn4Al-IL > Zn4Al.