PDADMAC改性蒙脱土制备硝酸根吸附剂

Modification of montmorillonite by PDADMAC to prepare nitrate adsorbent

硝酸根因其电负性强、水溶性大,难以形成沉淀,因而难以被快速吸附去除,通过化学改性增加吸附剂表面正电性可增强硝酸根吸附。用聚二甲基二烯丙基氯化铵(poly dimethyl diallyl ammonium chloride, PDADMAC)对蒙脱土进行改性,成功将PDADMAC负载在蒙脱土表面;通过对改性前后蒙脱土(Mt)进行表征,对比分析吸附机制。结果表明:改性后蒙脱土(PDM-Mt)的季胺氮含量增加,表面电势大幅提高;PDM-Mt对NO-3-N的吸附量在pH=7时为3.07 mg/g,相比改性前提升了86%;吸附过程符合准二级动力学模型以及Langmuir吸附等温模型,即主要是单分子层化学吸附;PDM-Mt对NO-3-N吸附过程在4 h内达到平衡,在pH值为5~7时有明显吸附效果;重复5次吸附后吸附量下降了21%,具有较高的可循环利用性。由此可见,PDADMAC具有作为改性剂促进硝酸根吸附的潜力。

To address the difficulties in n Nitrate removing by adsorption is difficult to form a precipitate due to its strong electronegativity,water solubility,and making it difficult to be removed by rapid adsorption.difficulty in precipitation formation,the Nitrate adsorption can be enhanced by increasing the positive charge of the adsorbent surface through chemical modification.The montmorillonite was modified with poly dimethyl diallyl ammonium chloride(PDADMAC),and PDADMAC was successfully loaded onto the surface of montmorillonite,and the adsorption mechanism was compared and analyzed by characterizing montmorillonite(Mt)before and after modification.The results show that:the content of quaternary amine nitrogen in modified montmorillonite(PDM-Mt)increases,and the surface potential increases significantly.The NO-3-N adsorption capacity of PDM-Mt is 3.07 mg/g at pH=7,which is 86%higher than that before modification.The adsorption process is in accordance with the quasi-second-order kinetic model as well as the Langmuir adsorption isothermal model,that means it is mainly single-molecule layer chemisorption.The NO-3-N adsorption process reaches equilibrium within 4 h,and the adsorption effect is obvious in the range of pH 5-7.After repeated 5 times,the adsorption capacity decreased by 21%,which showing high recyclability.PDADMAC has the potential as a modifier to promote nitrate adsorption.