Rice husk was obtained from local farmer near Changchun. The rice husk was mixed with phosphoric acid (50 wt%) in a mass ratio(rice husk to phosphoric acid) of 1:4, then the mixture was heated to 500◦C and maintained 1 h, the obtained product was treated in different ways: (1) it was washed with distilled water until neutral pH,the obtained solid product was denoted as P-AC; (2) it was washed with hot distilled water (95◦C) until neutral pH, the resulting solid product was named as P95-AC; (3) the solid product was washed with distilled water until neutral pH, then it was mixed with 3 wt%potassium hydroxide solution, the mixture was heated to boiling under reflux condition, and maintained 1 h, then the solid product was separated from liquid product by filtration, this solid prod-uct was labeled PK-AC. Another activated carbon was produced by KOH activation, the mass ratios of rice husk to KOH was 1:4, the reaction was conducted at 400◦C for 0.5 h, then 800◦C for 1 h, the corresponding activated carbon was named K-AC.