Adsorption Characteristics and Kinetic Models of Ammonium Nitrogen using Biochar from Rice Hull in Sandy Loam Soil

Abstract

Objective of this study was to investigate adsorption characteristics and kinetic models of NH₄-N to biochar produced from rice hull in respective to mitigation of greenhouse gases. NH₄-N concentration was analyzed by UV Spectrophotometer. For the experiment, the soil texture used in this study was sandy loam soil, and application rates of chemical fertilizer and pig compost were 420-200-370 kg ha -1 (N-P-K) and 5,500 kg ha -1 as recommended amount after soil test for corn cultivation. Biochar treatments were 0.2-5% to soil weight. Its adsorption characteristic was investigated with application of Langmuir isotherm, and pseudo-first order kinetic model and pseudo-second order kinetic model were used as kinetic models. Adsorption amount and removal rates of NH₄-N were 39.3 mg g -1 and 28.0% in 0.2% biochar treatment, respectively. The sorption of NH₄-N to biochar was fitted well by Langmiur model because it was observed that dimensionless constant (RL) was 0.48. The maximum adsorption amount (q m ) and binding strength constant (b) were calculated as 4.1 mg g -1 and 0.01 L mg -1 in Langmuir isotherm, respectively. The pseudo-second order kinetic model was more appropriate than pseudo-first order kinetic model for high correlation coefficient (r 2 ) of pseudo-second order kinetic model. Therefore, biochar produced from rice hull could reduce N₂O by adsorbing NH₄-N to biochar cooperated in sandy loam soil.