Comparison of batch and fixed bed adsorption process of 1,4-cyclohexanedicarboxylic naphthenic acid on bovine bone activated charcoal

ABSTRACT

The 1,4-cyclohexanedicarboxylic naphthenic acid is one of the main contaminants of petroleum and petrochemical wastewater. It can cause considerable damage to industrial operations as well as to the environment, due to its corrosive character and toxicity. An operation that can be performed to separate this contaminant is adsorption. Hence, the present paper aimed to evaluate the adsorptive capacity and efficiency of bovine bone activated charcoal in batch and fixed bed systems for the 1,4-cyclohexanedicarboxylic acid removal. Initially, crude and NaOH-treated activated charcoal was used in a batch system (pH = 3.2; m = 50 mg). The kinetic and equilibrium data indicated the treated charcoal as a better adsorbent for naphthenic acid, with experimental amounts retained in the equilibrium of 380 mg.g⁻¹. Treated activated charcoal was chosen for the fixed bed assays and, at first, the optimum flow of operation was obtained. Mass transfer parameters indicated that the diffusional effects on the bed were minimized by 2 mL.min⁻¹. The dynamic isotherm was obtained from the mass balances in the rupture curves and was evaluated as irreversible, with high values of retained acid (316.6 mg.g⁻¹). Different mass transfer mechanisms were observed in batch and continuous systems. However, the values of adsorption capacities in the equilibrium were similar. Thus, the bovine bone activated charcoal was favorable for the 1,4-cyclohexanedicarboxylic acid removal.

Keywords:
residual water; petrochemical industry; removal through adsorption; equilibrium data