改性生物炭对沼液氨氮的吸附效果研究

Research on Adsorption Effect of Ammonia-nitrogen from Biogas Slurry by Modified Biochar

针对沼液中氮含量排放超标污染问题,为筛选出能使氮元素最大回收的有效吸附方法,以玉米秸秆、玉米芯和木屑为原料,分别于550℃、600℃、650℃下热解成生物炭,并采用NaOH+微波、FeCl_3、KOH和HNO_3对其进行改性处理,采用扫描电镜和压汞仪对生物炭进行表征,通过吸附动力学、吸附等温线和影响因素试验考察生物炭对NH_4^+-N的吸附效果。结果表明:NaOH+微波改性的550℃玉米秸秆炭(A-550-NaM)、KOH改性的550℃玉米秸秆炭(A-550-K)、NaOH+微波改性的600℃木屑炭(C-600-NaM)和FeCl_3改性的550℃玉米芯炭(B-550-Fe)对NH_4^+-N的吸附平衡时间在60～150 min之间,其平衡吸附量分别为8.58 mg/g、8.30 mg/g、7.95mg/g和8.01 mg/g; Langmuir模型较Freundlich模型更适合描述B-550-Fe、A-550-NaM和A-550-K对NH_4^+-N的吸附行为,3种改性生物炭对NH_4^+-N的最大吸附量分别为200.24 mg/g、101.86 mg/g和94.82 mg/g。

Aiming at the problem of excessive nitrogen pollution in biogas slurry,and in order to screen out the effective adsorption method for maximum recovery of nitrogen,this study took corn stalk,scorn cob and sawdust as raw material,and produced biochar by pyrolysis at 550℃,600℃,650℃ and modified them with NaOH＋microwave,FeCl3,KOH and HNO3,separately. The biochar was characterized by scanning electron microscopy and mercury injection. The adsorption effect of biochar on NH4^＋-N was investigated by adsorption kinetics,adsorption isotherm and influencing factor experiment. The results showed that the adsorption equilibrium time of corn stalk modified by NaOH＋microwave of 550℃（ A-550-NaM）,corn stalk modified by KOH of 550℃（ A-550-K）,sawdust modified by NaOH＋microwave of 600℃（ C-600-NaM） and scorn cob modified by FeCl3 of 550℃（ B-550-Fe） were between 60 ～ 150 min,and their equilibrium adsorption quantities were 8. 58 mg/g,8. 30 mg/g,7. 95 mg/g and 8. 01 mg/g,respectively.Langmuir model was more suitable for describing the adsorption behaviors of NH4^＋-N by B-550-Fe,A-550-NaM and A-550-K than Freundlich model. The maximum adsorption capacity of these 3 kinds of modified biochars on NH4^＋-N were 200.24 mg/g,101.86 mg/g and 94.82 mg/g,respectively.