Kinetics and adsorption equilibrium of olive mill wastewater oxidizable organic pollution on activated carbon prepared from olive hulls
The objective of this study was to carry out a depollution of vegetable water by using adsorption on activated carbon made from the hulls of olive stones by chemical activation with ortho-phosphoric acid. After a preparatory treatment of the vegetable waters by acidification and centrifugation, the residual liquid phase is subjected to the adsorption treatment. The effectiveness of this treatment is evaluated by studying the influence of a few factors (adsorbate-adsorbate contact time, pH of the solution, adsorbent dose and initial concentration of adsorbate) in a batch system. Continuous system tests (fixed bed) were conducted in parallel, for comparison. The kinetics of adsorption in a batch system is pseudo-second order, limited by intraparticle diffusion. The adsorption equilibria generally conform to the Langmuir model. The final effluent is practically free of ortho-diphenols, depleted in total polyphenols (> 85% abatement), but quite rich in COD (42.5 g / l). Fixed bed treatment has been shown to be more efficient than the batch system and could totally eliminate PPTs, by a second fixed bed in series, offering the possibility of upgrading the final effluent by biological treatment, without risk of inhibition. The comparison of the chemical, textural and adsorption characteristics of the prepared activated carbon, CA-P2, with those of a commercial control active carbon, CAC1, is considered very satisfactory.
Keywords: Pollution control - Vegetables - Acidification - Kinetic - Adsorption isotherms - Activated carbon - Olive hull