不同基质组合对氮磷吸附能力的研究

就地利用菜地改建小型湿地系统可能是实现农村生活污水消纳和资源化利用的一种有效途径，其中菜园土与吸附基质的组合直接关系水体污染物中氮磷的净化效果. 选取沸石、谷壳、活性炭、陶粒和菜园土作为试验基质，使用BET比表面积孔径分析仪、扫描电子显微镜和Ｘ射线衍射仪(EDX)对其进行表征，通过等温吸附试验分别筛选出对氮磷吸附效果较好的沸石和陶粒，设置菜园土∶陶粒∶沸石质量占比基质组合:F1(10∶0∶0)、F2(6∶2∶2)、F3(8∶1∶1)、F4(8∶2∶0)、F5(8∶0∶2)、F6(6∶1∶3)和F7(6∶3∶1). 在低、中、高3种氮磷浓度下，通过吸附动力学试验筛选出去除效果最好的基质组合. 结果表明:①5种单一基质中，活性炭、陶粒的比表面积(35.72、33.23 m2/g)和微孔体积(2.20×10?1、8.25×10?2 cm2/g)均较大；沸石和陶粒表面呈粗糙多孔结构. ②Freundlich和Langmuir等温吸附模型均能较好地拟合5种单一基质对氮磷的吸附，各基质对氮的饱和吸附量表现为沸石(2.00 mg/g)>陶粒(1.47 mg/g)>菜园土(1.17 mg/g)>活性炭(0.99 mg/g)>谷壳(0.21 mg/g)，对磷的饱和吸附量表现为陶粒(1.28 mg/g)>活性炭(1.25 mg/g)>沸石(1.16 mg/g)>谷壳(0.80 mg/g)>菜园土(0.50 mg/g). ③7种基质组合对氮磷吸附具有相似的动力学特征，Elovich模型、双常数速率模型和一级反应动力学模型均能较好地模拟基质组合对不同污染负荷条件下氮磷的吸附规律. ④7种基质组合对氮磷的吸附速率均呈现先快后慢的趋势，最终于12~48 h趋于稳定. 研究显示，F2、F4和F7基质组合对氮磷的去除效果均较好，但考虑菜地改造的简易性和可操作性，F4为最佳基质组合，其在3种不同氮磷浓度下对氮、磷的吸附量分别为0.36~0.68和0.10~0.39 mg/g. 

Nitrogen and Phosphorus Adsorption Capacity of Different Substrate Combinations

The reconstruction of small wetland systems through on-site utilization of vegetable land may be an effective way to realize on-site absorption and resource utilization of domestic sewage. The combination of vegetable garden soil and adsorption materials is directly related to the removal of nitrogen and phosphorus in water. In this study, zeolite, grain husk, activated carbon, ceramsite and local vegetable garden soil were selected as test materials, and were characterized by the BET specific surface area aperture analyzer, scanning electron microscope and X-ray diffraction (EDX), and adsorption tests. Zeolite and ceramsite with better adsorption effect on nitrogen and phosphorus were screened out, Setting up a vegetable garden soil: ceramsite: zeolite mass proportional combination: F1 (10:0:0), F2 (6:2:2), F3 (8:1:1), F4 (8:2:0), (8:0:2) F5, F6 (dry cattle excrement) and F7 (6:3:1). Finally, under low, medium and high concentrations of nitrogen and phosphorus, the matrix combination with the best removal effect was selected through adsorption kinetic test. The results showed that: (1) The specific surface area (35.72, 33.23 m2/g) and micropore volume (2.20×10?1, 8.25×10?2 cm2/g) of activated carbon and ceramsite were larger in the five single substrates. The surface of zeolite and ceramsite has rough porous structure. (2) The adsorption of nitrogen and phosphorus by the substrates conformed to the Freundlich and Langmuir models. The nitrogen adsorption capacity of the five substrates was in the order of zeolite (2.00 mg/L) > ceramsite (1.47 mg/L) > vegetable garden soil (1.17 mg/L) > activated carbon (0.99 mg/L) > grain hull (0.21 mg/L), and the phosphorus adsorption capacity of substrates followed the order of ceramsite (1.28 mg/L)> activated carbon (1.25 mg/L)> zeolite (1.16 mg/L)> grain hull (0.80 mg/L)> vegetable garden soil (0.50 mg/L). (3) The adsorption kinetics of the seven substrate combinations for nitrogen and phosphorus were similar, and could be well fitted by the Elovich equation, double constant equation and first order kinetic equation under three different pollution loads. (4) The adsorption rates of nitrogen and phosphorus by substrate combinations increased at first and then slowed down, and finally stabilized at 12-48 h. The study shows that F2, F4 and F7 matrix combinations have good removal effects on nitrogen and phosphorus, but considering the simplicity and operability of vegetable field transformation, F4 was the best matrix combination, and its adsorption capacity of nitrogen and phosphorus was 0.36-0.68 mg/L and 0.10-0.39 mg/L, respectively under 3 different nitrogen and phosphorus concentrations.