四种材料对灌溉水中镉净化性能的比较

Performance of selected materials for the purification of cadmium contaminated irrigation water

基于前期筛选的4种材料——石灰石、沸石、赤泥粒和油菜秸秆,通过设计等温吸附实验和动态模拟实验,探讨了材料对灌溉水中Cd的快速吸附能力,应用Langmuir、Freundlich和Tempkin方程及BDST(Bed depth service time)模型分别对材料Cd等温吸附和动态吸附性能进行表征,旨在为材料进一步应用提供理论基础。结果显示,4种材料对Cd有不同吸附能力,平衡液Cd浓度10μg·L^(-1)时,材料Cd等温吸附量Qv(EC=0.79 m S·cm^(-1))依次为石灰石175.7 g·m^(-3)>沸石46.2 g·m^(-3)>赤泥粒20.7 g·m^(-3)>油菜秸秆3.7g·m^(-3);对Cd动态吸附量N0为赤泥粒1776 g·m^(-3)>石灰石1767 g·m^(-3)>沸石1704 g·m^(-3)>油菜秸秆837 g·m^(-3)。材料对Cd吸附过程中提升溶液pH的能力表现为赤泥粒>>石灰石和沸石>油菜秸秆。溶液离子强度对石灰石和沸石对Cd吸附有显著影响,并且随平衡液Cd浓度增加影响扩大,但是对油菜秸秆、赤泥粒对Cd吸附的影响较小。油菜秸秆对水中Cd吸附亲和力很强,但饱和吸附容量较低,吸附效率随净化时间延长衰减较明显。

Irrigation with Cd contaminated water is one of important sources to lead to high risk for safety of agricultural products and human health risk in paddy soil.The key to rapid purification of Cd contaminated irrigation water is the selection of cost effective large-size porous adsorbent.Anisothermal adsorption and dynamic simulation experiment was designed, three isothermal adsorptions equations（Langmuir, Freundlich and Tempkin）and the BDST（bed depth service time）model were applied to characterize the Cd adsorption performance of four materials that were red mud particles, limestone, zeolite and rape straw, aiming to provide theoretical basis for the practical applications of the materials.When the Cd concentration of equilibrium solution was 10 μg·L-1, the amount of adsorbed Cd in water with electric conductivity of0.79 m S·cm^（-1）was in the order as limestone 175.7 g·m-3 〉zeolite 46.2 g·m-3 〉red mud particle 20.7 g·m-3 〉rape straw 3.7 g·m-3; the amount of adsorbed Cd in the dynamic experiment was in the order as red mud particle 1776 g·m-3〉 limestone 1767 m-3 〉zeolite 1704 g·m-3〉rape straw 837 g·m-3. In purification process,all four materials are able to raise the pH of irrigation water and are in the order as red mudlimestone and zeolite〉 rape straw. The Cd adsorption by limestone and zeolite from irrigation water is affected by ionic strength which increases with the increase of Cd concentration in balance solution.Compared with limestone and zeolite, the ionic strength in simulated solution has little influence on the purification performance of rape straw and red mud particle. The Cd adsorption affinity of rape straw in irrigation water was significantly higher than that of other three materials.However, the Cd adsorption capacity of rape straw is relatively small.And, the Cd dynamic purification efficiency of rape straw on Cd contaminated irrigation watershowed obvious attenuation trend with the prolonging of the purification time.