BACKGROUND : Recently, biomass conversion from agricultural wastes to carbon-rich materials such as biochar has been recognized as a promising option to maintain or increase soil productivity, reduce nutrient losses, and mitigate greenhouse gas emissions from the agro-ecosystem. This experiment was conducted to select an optimum conditions for enhancing thd NH4-N adsorption capacity of rice hull activated biochar.
METHODS AND RESULTS : For deciding the proper molality of KOH for enhancing its porosity, biochars treated with different molality of KOH(0, 1, 2, 4, 6, 8) were carbonized at 600℃ for the reactor. The maximum adsorption capacity was 1.464 mg g-1, and an optimum molarity was selected to be 6M KOH. For the effect of adsorption capacity to different carbonized temperatures, 6M KOH treated biochar was carbonized at 600℃ and 800℃ under the pyrolysis system. The result has shown that the maximum adsorption capacity was 1.76 mg g-1 in the activated rice hull biochar treated with 6M KOH at 600℃ of pyrolysis temperature, while its non-treated biochar was 1.17 mg g-1. The adsorption rate in the activated rice hull biochar treated with 6M KOH at 600℃ was increased at 62.18% compared to that of the control. Adsorption of NH4-N in the rice hull activated biochar was well suited for the Langmuir model because it was observed that dimensionless constant (RL) was 0.97 and 0.66 at 600℃ and 800℃ of pyrolysis temperatures, respectively. The maximum adsorption amount(qm) and the bond strength constants(b) were 0.092 mg g-1, 0.001 mg L-1, respectively, for the rice hull activated biochar treated with 6M KOH at 600℃ of pyrolysis.
CONCLUSION : Optimum condition of rice hull activated biochar was 6M KOH at 600℃ of pyrolysis temperature.