Experimental and Modeling Comparisons of Ash-Treated Pine Biochar and Activated Carbon for the Adsorption of Dissolved Organic Matter and Organic Micropollutants

A novel powdered ash-treated pine biochar (PATB) was compared to powdered activated carbon (PAC) for the removal of dissolved organic matter (DOM) and organic micropollutants (OMPs) from deionized water (DI), raw surface water (SW), and treated wastewater (WW). PATB performance (capacity and kinetics) was the primary focus under realistic water treatment adsorbent doses ($<200\mathrm{mg}/\mathrm{L}$) and contact times ($<120\min$). For the removal of DOM, iohexol (IOH), sucralose (SUC), and sulfamethoxazole, PAC consistently outperformed PATB. For the more readily adsorbable OMPs carbamazepine, cotinine, DEET, and theobromine, removal by the two adsorbents was comparable. Dose-response and kinetic results for each adsorbent between SW and WW for DOM, IOH, and SUC were similar, as their initial dissolved organic carbon concentrations were diluted to the same range: 2.0–$2.2\mathrm{mg}/\mathrm{L}$. SUC was found to have a higher affinity for PATB in DI, but ultimate removal was still limited by its lower specific surface area compared to PAC ($\sim 500$ versus $\sim \mathrm{1,000}{\mathrm{m}}^2/\mathrm{g}$). Additional investigations included combined adsorbent treatment and projecting batch results to fixed-bed breakthrough curves for hypothetical full-scale granular activated carbon and granular ash-treated biochar adsorbers using both the homogeneous surface diffusion model and pore and surface diffusion model.