对天然斜发沸石进行碱液预处理、盐热复合改性,并进行挤压制粒,研究了改性及制粒对斜发沸石氨氮吸附性能的影响。结果表明:天然斜发沸石经1.0 mol/L NaOH溶液预处理2 h,再经2.0 mol/L NaCl溶液处理2 h及400℃焙烧热处理0.5 h后,氨氮去除率从54.4%提高到98.3%。在复合改性后的沸石中添加6%硅酸钠黏结剂,经400℃热处理,制成粒径为φ1.5 mm×2.5 mm的短柱状改性沸石颗粒,其氨氮去除率为83.3%,散失率为1.1%。采用NaCl+NaOH溶液作为再生剂,1次再生后氨氮去除率为75.2%,5次再生后,氨氮去除率为67.8%。改性沸石及其颗粒对氨氮吸附过程符合准二级反应动力学公式,属于化学吸附(离子交换)。沸石粉体及其颗粒对氨氮的吸附是以膜扩散和内扩散为共同控制步骤,为自发和吸热过程,温度升高,吸附量增加。另外,熵效应是吸附反应过程的主要驱动力。
Natural clinoptilolite was pretreated by NaOH solution and compound modified by NaCl solution and roasting, as well as squeezed into granules after modification. Effects of modification and granulation on the properties of ammonia-nitrogen removal were investigated. The results show that ammonia-nitrogen removal rate of clinoptilolite (after pretreated by 1.0 mol/L NaOH solution and modified by 2.0 mol/L NaC1 and roasting at 400 ℃ for 0.5 h) increases from 54.4% to 98.3%, and the ammonia-nitrogen removal rate of the zeolite granules with the size of φ1.5 mm×2.5 mm prepared at 6% sodium silicate content and 400 ℃ is 83.3% and the loss rate is 1.1%. The ammonia-nitrogen removal rate is 75.2% after regeneration for 1 time with NaC1 and NaOH solutions, and 67.8% after regeneration for 5 times. The adsorption kinetics of ammonia-nitrogen of zeolite and granules follows a pseudo-second order adsorption dynamic model, which describes the adsorption of ammonia-nitrogen in aqueous solution mainly as a chemical adsorption. The ammonia-nitrogen adsorption process is mainly controlled by membrane diffusion and internal diffusion process. Besides, the process is a spontaneous and endothermic process, the adsorption capacity increases with increasing the temperature, and the entropy is the main effect of the adsorption process.