Steam pretreatment of bone char for adsorption of refractory organics from electrodialysis concentrate produced by petroleum refinery

Water reuse has been gaining strength with a focus on sustainability issues and the water crisis. However, as water recirculates in the processes, the demand for the removal of refractory compounds comes up, some toxics even at small concentrations. To maximize the possibilities of water reuse, a steam pretreatment at 98 ± 2 °C for bone char used as adsorbent is proposed to improve refractory organic compounds removal from refinery wastewater. In this study, raw and steam-pretreated bone char (0.5–1.4 mm) were used to remove refractory organics from a petroleum refinery reverse electrodialysis (EDR) effluent (COD: 60 mg L⁻¹) and phenol from a synthetic solution (COD: 47 mg L⁻¹). In addition to solid characterization analysis, bench-scale tests in batch and semi-continuous systems were carried out, using an orbital shaker and fixed-bed column, respectively. The pretreatment provided a greater surface area, porosity, and adsorptive capacity to the bone char, in comparison to the raw one. In batch tests, the adsorptive capacity of the pretreated bone char was 15 and 19% higher than raw bone char, applying EDR effluent and phenol synthetic solution, respectively. The semi-continuous test for phenol removal using pretreated bone char provided a breakthrough curve with the expected sigmoidal format and was best described by the models of Yoon and Nelson (R² = 0.9836), Yan (R² = 0.96705), and Thomas (R² = 0.9836). The adsorptive capacity values of 2.99 mg g⁻¹ and 2.88 mg g⁻¹ from batch and semi-continuous tests, respectively, were close for phenol removal using pretreated bone char.