29种湿地填料对氨氮的吸附解吸性能比较

为筛选出性能更好的人工湿地填料,采用等温吸附-解吸试验,测定了29种天然和非天然人工湿地填料的孔隙率、渗透系数及其对NH₃-N的吸附-解吸特性. 结果表明:锯末、瓷砖、鸡蛋壳、瓷砂陶粒、火山岩等材料的孔隙率较大,瓷砂陶粒、海绵铁、石灰石、页岩陶粒、砾石等材料的渗透系数较大；Freundlich和Langmuir等温吸附方程能较好地拟合各填料对NH₃-N的吸附特征,通过Langmuir等温吸附方程计算,对NH₃-N的理论饱和吸附量居前5位的填料依次是火山岩(1.700 0 mg/g)、瓷砂陶粒(1.620 0 mg/g)、生物炭(1.353 0 mg/g)、沸石(1.350 0 mg/g)、石榴石(1.190 0 mg/g). 吸附速率的变化与填料吸附NH₃-N的途径密切相关. 吸附饱和的生物炭、焦炭、大理黏土、沸石、磁铁矿、石英砂主要通过离子交换作用吸附NH₃-N,稳定性好,解吸率均小于20%；瓷砂陶粒和火山岩对NH₃-N的解吸率分别为24.50%和35.51%,既有物理吸附也有离子交换作用. 火山岩、瓷砂陶粒、生物炭、沸石对较高浓度NH₃-N的吸附效果较好. 研究显示,火山岩、生物炭、瓷砂陶粒、沸石等适合作为人工湿地中吸附NH₃-N的填料. 

Ammonia Nitrogen Adsorption and Desorption Characteristics of Twenty-Nine Kinds of Constructed Wetland Substrates

Abstract: The porosity, hydraulic conductivity and adsorption and desorption characteristics of ammonia-nitrogen (NH₃-N) in twenty-nine kinds of materials were analyzed to determine more effective constructed wetland substrates for adsorbing NH₃-N.The results showed that the porosity of sawdust,vitrolite, egg shell,porcelain ceramist and volcanic rock were larger, while the permeability of ceramsite, sponge iron, limestone, shale ceramsite, and gravel were higher. Freundlich and Langmuir isotherms could adequately predict the adsorption process. According to the estimates from the Langmuir isotherm, the maximum theoretical saturated capacities decreased in the following order:volcanic rock (1.7000 mg/g)>porcelain ceramist (1.6200 mg/g)>biochar (1.3530 mg/g)>zeolite (1.3500 mg/g)>garnet (1.1900 mg/g). In general, there were three kinds of trends of NH₃-N adsorption rates in substrates:one was first increase, then decreaseand finally tended to balance; second was first increase, then tended to balance; and third was first increase, then decrease, and finally increase. The variation of adsorption rate was closely related to each substrate''s adsorption mechanism. Adsorption saturated substrates such as biochar, coke, dali clay, maifan stone, anthracite, zeolite, magnetite and quartz adsorbed NH₃-N mainly through ion exchange, which is more stable with smaller desorption rates(<20%).Clay ceramsite and volcanic rock adsorbed NH₃-N through combined physical adsorption and ion exchange, with desorption rates of 24.5% and 35.1% respectively. Volcanic rock, porcelain ceramist, biochar and zeolite showed higher adsorption efficiency when treating wastewater with high concentration of NH₃-N.Consequently, volcanic rock, porcelain ceramist, biochar, zeolite are appropriate substrates for constructed wetlands.