Comparison of the adsorption capacity of organic compounds present in produced water with commercially obtained walnut shell and residual biomass

The effectiveness of the adsorption of organic compounds in produced water with different residual biomass sources has been investigated. Adsorption capacities have been analyzed with palm shell, orange peel, banana peel, passion fruit peel, cocoa bean and sawdust; and compared to the commercial adsorbent walnut shell. All adsorbents undergo a pretreatment, prior to the adsorption, consisting of washing, drying and thermal conditioning. For the investigation of the adsorption capacity of the different adsorbents, synthetic produced water has been prepared with different organic compounds and expressed as the concentration of Chemical Oxygen Demand (COD). The adsorption capacities of the different adsorbents are expressed as the removal percentage of oxidizable contaminants, presented as COD concentration in the synthetic produced water. The adsorption analyses with the synthetic produced water in a batch experimental procedure show that only palm shell and sawdust actually adsorb the organic compounds in the synthetic water. Three isotherm models were considered: Langmuir, Freundlich and Temkin. Among these three models, the Langmuir model describes best the experimental data for walnut shell, palm shell and sawdust. The maximum adsorption capacity was determined and sawdust presented a maximum value of contaminant removal of 33 mg/g of dry adsorbent, while walnut shell and palm shell presented a contaminant removal of 4.9 and 5.6 mg/g of dry adsorbent, respectively. Kinetics results were best described by pseudo-first order potential law model for the experiments carried out with the walnut shell and palm shell. Breakthrough experiments show that palm shell will saturate earlier than walnut shell.