稻秸吸附钾离子特性及其影响因素研究

Characteristics of potassium ion absorbed on rice straw and its affecting factors

以农业废弃物水稻秸秆为吸附材料,通过平衡吸附法研究了各影响因素下稻秸对K^+的吸附规律。结果表明:(1)在外源K^+浓度较低时(0~40 mg/L),增温可促进稻秸释钾作用来抑制两者间的吸附,相反,将其浓度增至40~1 000 mg/L的范围,增温才有利于稻秸对K^+的吸附。两者间存在多层吸附现象,该过程吸热,难以自发且固、液界面在吸附后混乱度有增加趋势;(2)稻秸表面携有较多含氧官能团,其负电荷随p H值升高而增大,在此过程中,稻秸静电吸附K^+的强度被大幅提升;(3)稻秸对K^+的吸附以化学键为主,Na^+在压缩双电层厚度、削弱吸附质与吸附剂之间静电作用的能力方面要大于NH_4^+;(4)稻秸与K^+间的最适质量比为5∶2;(5)298 K的温度条件下,稻秸与K^+间的接触时间必须超过420 min才有"净吸附",而较高温度(318 K)下接触时间需大于1 380 min。在描述两者间动力学吸附规律方面,分阶段拟合会取得较好的拟合效果。上述规律的阐明可为废弃稻秸与K^+的合理搭载提供科学配方,为下一步研发"富钾稻秸"有机肥提供技术支撑和理论参考。

As one of the agricultural wastes,the rice straw can be served as a raw material that adsorbed K^＋. The method of equilibrium adsorption was adopted to study the adsorbed rule of K^＋on the rice straw under the different influencing factors.The results showed that：（ 1） When the initial concentration of K^＋was low（ 0-40 mg / L）,the temperature raising promoted the effect of rice straw releasing K^＋to restrain the sorption,on the contrary,when the concentration of K^＋was increased to the range of 40-1 000 mg / L,the adsorption of K^＋on the rice straw was enhanced by the increased temperature. The phenomenon of multilayer adsorption occurred,the process was endothermic and spontaneous,and the disorder in the solid-liquid interface was also increased after the sorption;（ 2） The surface of rice straw carried a large number of O-contained functional groups,whose negative charges were enhanced with the increasing of p H value. The increased p H value enhanced the adsorbed amount of K^＋on the rice straw through strengthening the electrostatic adsorption;（ 3） The chemical bonding was dominated in the adsorption mechanism. In the aspect of compressing the thickness of double electrode layer and weakening the electrostatic interaction between adsorbate and adsorbent,the ability of Na^＋was more than NH4^＋;（ 4） The appropriate mass ratio of rice straw/ K^＋was 5∶2;（ 5） Under the temperature condition of 298 K,if the contact time from the both was more than 420 min,the net adsorption was possibly happened,however,at relatively higher temperature（ 318 K）,the contact time must be more than 1 380 min. In describing the dynamic adsorption between rice straw and K^＋,the best fitting results was obtained by a two-step fitting algorithm. The rule mentioned above not only provided a scientific formula based on a reasonable allocation of straw and K^＋,but also gave a technical support and theoretical reference for developing a new organic fertilizer,in which the straw and K^＋could serve as the main raw materials.