pDADMAC改性活性炭对水中硝酸盐的吸附特性

Adsorption characteristics of nitrate in water by pDADMAC modified activated carbon

相对于生化反硝化,吸附法对NO_(3)^(-)的去除速率更快.自然胶体对NO_(3)^(-)的吸附能力有限,研发高效、低成本、制备流程简便的NO_(3)^(-)吸附剂具有重要价值.用聚二烯丙基二甲基氯化铵(pDADMAC)改性活性炭(GAC),提升其Zeta电位,实现对NO_(3)^(-)的高效吸附,并通过改性前后材料的形貌表征,探究其对水中NO_(3)^(-)的吸附机制.结果表明,pDADMAC负载到了活性炭表面,pDADMAC-GAC表面Zeta电位在pH=4—12范围内都得到了提升,因此在较宽的pH范围内对NO_(3)^(-)都有良好的吸附效果.pDADMAC改性后的活性炭(pDADMAC-GAC)对NO_(3)^(-)的吸附量明显提高,约为改性前的3.36—5.06倍.pDADMAC-GAC对NO_(3)^(-)的吸附动力学过程符合准二级动力学,吸附过程以化学吸附为主;在25℃、pH=6、初始NO_(3)^(-)浓度为15 mg∙L^(-1)条件下,准二级动力学模型计算得到的pDADMAC-GAC对硝酸盐的最大吸附量为3.26 mg∙g^(-1).Langmuir吸附等温线拟合效果最好,表明其主要是单分子层吸附.重复性和干扰性实验表明,pDADMAC-GAC具有可重复利用性,水中共存的SO_(4)^(2−)、H_(2)PO_(4)^(-)和Cl−阴离子对NO_(3)^(-)吸附有一定干扰.综上,pDADMAC-GAC具有作为优良的NO_(3)^(-)阴离子吸附剂的潜力.

Compared with biochemical denitrification,the adsorption process is more faster to the removal of NO_(3)^(-)from water.As natural colloids,their adsorption capacity of NO_(3)^(-)was limited,so,it is of great value to develop adsorbents with high efficiency,low cost and simple preparation process.In this study,activated carbon(GAC)was modified with polydiallyl dimethyl ammonium chloride(pDADMAC)to improve its Zeta potential and achieve the efficient adsorption capacity for NO_(3)^(-).The adsorption mechanism was investigated by the morphological characterization of the materials before and after modification.The results showed that pDADMAC was loaded on the surface of activated carbon,and the Zeta potential of pDADMAC-GAC surface increased in the range of pH 4—12,so it had a good adsorption performance on NO_(3)^(-)in a wide range of pH.The adsorption capacity of pDADMAC-GAC to NO_(3)^(-)was significantly increased,which was about 3.36—5.06 times of that before modification.The adsorption process of pDADMAC-GAC on NO_(3)^(-)was corresponding with quasi-second-order kinetics model,which indicates the chemical adsorption is main.Under the conditions of 25℃,pH=6 and initial NO_(3)^(-)concentration of 15 mg∙L−1,the maximum adsorption capacity of pDADMAC-GAC on nitrate calculated by quasi-second-order kinetics model was 3.26 mg∙g−1.Langmuir model are better to correspond the adsorption isotherms,indicating that it is a monolayer adsorption.Repeatability and interference experiments showed that pDADMAC-GAC was reusable,and the coexistence of SO_(4)^(2−),H_(2)PO_(4)^(-)and Cl−anions in water interfered with NO_(3)^(-)adsorption to a certain extent.In conclusion,pDADMAC-GAC has the potential to be an excellent NO_(3)^(-)anionic adsorbent.