Fixed-bed study for bone char adsorptive removal of refractory organics from electrodialysis concentrate produced by petroleum refinery.

Water reuse in industrial processes has been an increasing need encouraged in recent years. However, as the streams are recycled, solutes accumulate, thus requiring purification techniques. Membrane processes (reverse osmosis and electrodialysis) have been implemented and in order to increase the reuse of water at its highest level, crystallization has been evaluated to remove salts from the concentrate produced and get a feasible disposal. Nevertheless, contaminants affect the crystallization performance, thus making the removal of residual organics important for both the efficiency of crystallization and the increase of water reuse. In this context, aiming at establishing a sustainable virtuous circle, bone char (0.5-1.4 mm particle size, mesoporous structure) was used to remove refractory organics from an electrodialysis concentrate effluent (C-EDR) from a Brazilian petroleum refinery, at a lab-scale, in a fixed-bed adsorption column. Bone char selectively and partially removed the refractory organics, a complex mixture of long-chain hydrocarbons, aromatic compounds, carboxylic acids, amines and amides. The maximum adsorption capacity increased with the increase in bed depth and reduction in flow rate. A maximum removal of 35.60 mg g-1 was achieved for the highest bed depth evaluated (12.9 cm). The breakthrough curves indicated that bone char could adsorb part of the organic compounds from the C-EDR. The scaling up was possible for the C/C0 ratios of 0.55, 0.60 and 0.65, providing a service time at about 16 days for 45% removal efficiency for typical real operational conditions used in the refinery.