Synthesis and characterization of surface modified montmorillonite for nano-adsorption of phenolic compounds from olive mill wastewater as a novel valorization strategy

In this study, to recover phenolics from olive mill wastewater (OMW), adsorption was performed by raw montmorillonite (Mt) and three modified-Mt forms. The Mt was modified with tetradecyl trimethylammonium bromide (TTB), cetyl trimethylammonium bromide (CTB), and didodecyl dimethylammonium bromide (DDB). The effect of adsorption time, pH and adsorbent dosage (AD) on the adsorption efficiency (AE) of phenolics from OMW were investigated. Experimental results revealed that the maximum AE (93.43%) was obtained by TTB-modified Mt at pH= 4.7, and AD = 0.66 g/L. The Mt and TTB-modified Mt were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy before and after adsorption in optimum situation in order to establish the adsorption behavior-properties relationship. The results showed there was successful adsorption of phenolics on TTB-modified Mt. The equilibrium data of adsorbed phenolics was fitted well to Langmuir models (R2= 0.9914) and the kinetic data indicated that the best fit of experimental data was pseudo-second order model (R2=0.9988). Finally, a continuous system for recovering the phenolics from OMW was designed; the maximum AE corresponded to an AD = 0.3 g, a flow rate = 1 mL/min and a total phenolics concentration = 15 mg/L which yielded an AE = 100%. In conclusion, we successfully modified Mt to create a promising nanoadsorbent capable of adsorbing valuable compounds, such as phenolic compounds, from wastewater and byproducts of the food industries.