Adsorption of contaminants found in hydraulic fracking produced water utilizing cost-effective biochar treatment
Hydraulic fracturing wastewater is difficult to treat due to high concentrations of dissolved inorganic solids and organic hydrocarbons. Current technologies are expensive in the treatment of these contaminants. Utilizing low cost biochar, an adsorbent, produced from forestry and agricultural wastes can significantly reduce the cost for treating hydraulic fracturing wastewater. This study focuses on the removal of Na, Ca, Mg, Sr, K, and hydrocarbons from solutions of known concentrations and how effective the biochars are in the removal of these inorganic salts commonly found in shale gas produced water. Commercial activated carbon, coconut char and biochars produced from pine and oak wood at three different pyrolysis temperatures, 350°C, 450°C, and 550°C, were used as the adsorbents. Two types of batch studies, stagnant and mixing, and one continuous flow study in a packed column were performed to investigate adsorption capabilities. The batch mode results from the stagnant and mixing studies indicate that diffusion is the primary mechanism for adsorption process. The results from the continuous column experiments shows that biochar produced from pyrolysis removed 46% of K2CO3 for oak char produced at 350°C, 14% of Sr(NO3)2 with coconut char, 16% of MgCl2 with pine char produced at 550°C, 19% of NaCl with coconut char, 25% of CaCl2 with pine char produced at 550°C. Results suggest that the feed type, pyrolysis temperature, adsorbate properties and ionic radius are factors affecting adsorption. Pine and oak wood biochar produced at 350°C and 450°C are effective in removing up to 95% of hydrocarbons at different concentrations.