尿素改性生物质炭吸附水中氨氮研究

摘要

Wheat straw biochar was modified by urea to adsorb ammonia nitrogen in water.The impact factors (urea dosage,pH,adsorbent dosage and competitive cations) and adsorption mechanisms were studied.Results showed that the modified biochar UBC-4 which was prepared by 1.00 unmodified biochar with 2.4 g urea had the best adsorption capaicity on ammonia nitrogen because UBC-4 had low zero-charge point.When treating 20 mL NH4 Cl solution of 60 mg/L,optimal pH was 8 and optimal adsorbent dosage was 0.20 g.Competitive cations like Na+ and Mg2+ should not be ignored especially when treating real wasterwater.Langmuir equation could effectively fit the isothermal adsorption data.The pseudo second order kinetic model could effectively describe its adsorption dynamic process.The adsorption on ammonia nitrogen by UBC-4 was an endothermic and spontaneous process.The adsorption mechanism was physical adsorption.%利用尿素对小麦秸秆生物质炭进行改性,用于吸附水中氨氮.研究了尿素添加量、pH、改性生物质炭投加量、共存阳离子等因素对改性生物质炭吸附氨氮的影响,并研究了吸附的热力学和动力学机制.结果表明,1.00 g未改性生物质炭中添加2.4g尿素时制备得到的改性生物质炭UBC-4对氨氮吸附能力最好,零电荷点相比改性前明显降低.处理20 mL 60 mg/L的氯化铵溶液,UBC-4最佳投加量为0.20 g,最适pH为8.实际废水处理中应考虑Na+、Mg2+等共存阳离子对UBC-4吸附氨氮的竞争吸附作用.Langmuir方程能较好地拟合UBC-4对氨氮的吸附等温过程,准二级动力学模型能较好地描述其动力学过程.吸附为自发的吸热过程,主要机制是物理吸附.