改性沸石对猪场沼液氮磷吸附特性与机理分析

Mechanisms of Nitrogen and Phosphorus Adsorption from Biogas Slurry of Piggery by Modified Zeolite

针对猪场沼液氮磷含量高、有机污染严重、难以处理的问题,采用经氯化钠溶液改性沸石为载体对沼液中氮磷吸附特性和去除机理进行分析研究,考察了沸石投加量、吸附时间、沼液初始浓度等影响因素。结果表明:当沸石投加量为每100mL10g、吸附时间48 h时,最大氨氮去除率可达90.66%,氨氮饱和吸附量可达1.43 mg·g-1,最大总磷去除率可达85.97%,磷饱和吸附量可达0.16 mg·g-1。吸附后的沸石污泥含有大量氮磷元素,是一种优质缓释肥料。Freundlich、Langmuir方程均能较好地解析改性沸石的等温吸附过程,其吸附动力学符合准二级动力学模型,R2均达0.98以上。沸石对猪场沼液中有机态氮磷去除主要基于物理性吸附和沸石中的活性基团与有机官能团所产生的配位络合,无机态氮磷则主要以离子交换及吸附沉淀方式得以去除。

Biogas slurry is rich in nutrients, such as nitrogen, phosphorus and organic compounds. Removals of these nutrients will reduce biogas slurry risks to the environment. In this study, adsorption characteristics of nitrogen and phosphorus from biogas slurry were investigated using modified zeolite under different zeolite doses, adsorption times, and initial concentrations of biogas slurry. The removal mechanisms of nitrogen and phosphorus by the modified zeolite were also explored. At 10 g per100 mL of zeolite and 48 h of adsorption time, the removal rates of NH4^＋ and TP were up to 90.66% and 85.97%, with maximal adsorption capacity of 1.43 mg·g^-1 and 0.16 mg·g^-1, respectively. The zeolite after adsorption contained high nitrogen and phosphorus, and was a high quality slow-release fertilizer. Nitrogen and phosphorus adsorption could be better fitted by Freundlich and Langmuir isotherm models, with R^2 over 0.98. Their adsorption kinetics followed the pseudo second-order kinetic model. Organic nitrogen and phosphorus removals by the zeolite were mainly via physical adsorption and coordination reaction, while inorganic ones through ion exchange and precipitation.