Effects of Environmental Conditions on Rice-straw Biochar Adsorption of Nitrate

The overall aim of this study was to determine adsorption characteristics of nitrate on biochars in different environmental conditions. Biochars were produced from rice straws at 400℃, 600℃ and 800℃, respectively. They were then divided into two particle sizes (1.91mm and 0.38mm). Laboratory batch sorption experiments were conducted to access the overall aqueous nitrate sorption ability of the biochars in different environmental conditions. Results showed that biochar produced at 400℃ had the largest adsorption capacity for NO3 --N, its removal rate of nitrate could be up to 88%. Particle size showed no significant effect on NO3 --N adsorption. Biochars showed large variances on adsorption characteristics in different environmental conditions, such as contact time, initial NO3 --N concentration and adsorbent dose. We concluded that 400℃ rice-straw biochar can be used for NO3 --N adsorption and recommended the contact time, initial NO3 --N concentration, initial pH value and adsorbent dose for 12 h, 15 mg L-1, 7 and 3g per 50ml, respectively.