Adsorption of NH3-N onto rice straw-derived biochar

Abstract

In this study, potential of rice straw-derived biochar as an NH3-N was evaluated. The aims of this study are to evaluate the NH3-N adsorption kinetics, examine NH3-N adsorption capacity, suggest the optimal pyrolysis temperature for NH3-N removal, and investigate the effect of solution pH on the NH3-N removal by rice straw-derived biochar. In order to achieve these goals, series of experiments on NH3-N adsorption by rice straw-derived biochar specimens obtained at four different temperatures (300, 400, 500, and 600 °C) were conducted. The results show that more than half of mass transfer was finished in 2 h, and this ensures feasibility for in-situ operation. According to the adsorption isotherm experiments, NH3-N adsorption capacity by rice straw-derived biochar increased with initial NH3-N concentration and it seems to result from multilayer adsorption behaviors. The optimal pyrolysis temperature for NH3-N removal was around 400 °C. It seems that enlargement of surface area compensated the dissipation of functional groups associated with NH3-N removal. The influence of pH on NH3-N removal was distinguished depending on the pyrolysis temperature. Adsorption envelopes of NH3-N by BC300 and BC400 resembled those of common cationic species, however those of BC500 and BC600 showed different patterns. Solution pH should be carefully managed for NH3-N adsorption process by rice straw-derived biochar.