UC Riverside Undergraduate Research Journal

In order to enhance biochar’s adsorption efficiency for ammonia removal, it must first undergo acid activation, a process in which the surface chemistry of the biochar is altered.  Although acid activation is known to increase ammonia adsorption capacity, the effects of specific preparation parameters are not well understood. During activation, biochar is soaked in phosphoric acid and then rinsed to remove residual unbound acid, which could otherwise react with ammonia and interfere with future adsorption measurements. This study focuses on the acid activation step for woodchip biochar pyrolyzed at 500 °C for 15 minutes. Three parameters were investigated: particle size (ground vs. unground), phosphoric acid concentration (15%, 30%, and 45%), and rinsing method (two rinses, five rinses, or a one-hour soak using 20 mL of DI water). pH was measured before and after treatment and used as an indicator of potential ammonia adsorption. To increase readability, the experiment was repeated twice, and samples were prepared at 1 g per condition, resulting in 18 combinations. According to preliminary results, post-activation pH values ranged from 2.2–3.3, whereas initial values ranged from 7.87–9.78. Unground biochar strains consistently showed lower pH values than their ground counterparts, likely due to the difference in particle size. Samples treated with higher acid concentrations (45%) produced lower pH values than those treated with 15% acid, which is consistent with expected trends.