Pomegranate peel and orange juice by-product as new biosorbents of phenolic compounds from olive mill wastewaters

Several wastes and residues have been studied for the adsorption of phenolic compounds with varying success. However, new economical, easily available, and highly effective adsorbents are still needed. The purpose of this work is to consider the potential of two food wastes derived from agricultural activities, the non-modified pomegranate peel and orange juice by-product, after the removal of their own phenolic content, for phenolics sorption from olive mill wastewater. This procedure is the second step of an integrated approach for complete utilization of these wastes in recovering valuable ingredients, while succeeding total depollution. Initially, the equilibrium time was investigated and afterwards, the effects of sorbent mass concentration (0.01-0.02 g/mL), temperature (20-60 degrees C), solution's pH (4-7), initial sorbate concentration (50-500 mg/L), and sorbent particle size on total phenols uptake were studied. The highest adsorption efficiencies obtained were 93.13 and 89.59% using pomegranate peel and orange juice by-product, respectively. Total phenols removal efficiency was maximum at pH 4.75 and was improved by decreasing adsorbents dosage, initial sorbate concentration, temperature, and sorbents particle size. The sorption followed the intra-particle diffusion model and was described better by the Freundlich sorption isotherm. The results indicated that the studied materials could be employed as alternative low-cost biosorbents.