Li Zhaohui, Hong Hanlie
Faculty of Earth Science, China University of Geosciences, Wuhan 430074, China.
J Hazard Mater. 2009 Mar 15;162(2-3):1487-93. doi: 10.1016/j.jhazmat.2008.06.061. Epub 2008 Jun 24.
In this study, zeolite aggregates with particle size < 0.4, 1.4-2.4, and 3.6-4.8 mm were modified by the cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide to a surfactant loading level of 80, 130, and 250 mmol kg(-1), respectively. The modified and unmodified zeolites were subjected to column tests to study the chromate transport and retardation as affected by particle size. At an input concentration of 11-15 mg L(-1), unmodified zeolite did not retard chromate transport for all three particle size ranges. In contrast, the observed retardation factor for chromate, defined as the number of pore volumes passed when the output concentration equals to half of the input concentration, was 55, 50, and 500 for the columns packed with 3.6-4.8, 1.4-2.4, and < 0.4 mm modified zeolite, respectively. Prolonged tailing of chromate desorption from the modified zeolite was the most striking feature after the feeding solution was switched from chromate to water at full breakthrough. Monitoring of HDTMA and counterion bromide concentration in the effluent revealed that slow but persistent desorption of HDTMA and bromide occurred throughout the transport experiment, which resulted in stripping off of the upper layer of the surfactant bilayer formation on zeolite. The change of HDTMA surfactant surface configuration from bilayer to monolayer resulted in a loss of functionality to absorb and immobilize chromate on the modified zeolite surfaces.
在本研究中，将粒径小于0.4、1.4 - 2.4和3.6 - 4.8毫米的沸石聚集体分别用阳离子表面活性剂十六烷基三甲基溴化铵（HDTMA）改性至表面活性剂负载水平分别为80、130和250 mmol kg⁻¹。对改性和未改性的沸石进行柱试验，以研究粒径对铬酸盐迁移和阻滞的影响。在输入浓度为11 - 15 mg L⁻¹时，未改性沸石在所有三个粒径范围内均未阻滞铬酸盐迁移。相比之下，对于填充有3.6 - 4.8、1.4 - 2.4和小于0.4毫米改性沸石的柱体，定义为输出浓度等于输入浓度一半时所通过的孔隙体积数的铬酸盐阻滞因子分别为55、50和500。在完全穿透时将进料溶液从铬酸盐切换为水后，改性沸石中铬酸盐解吸的长时间拖尾是最显著的特征。对流出物中HDTMA和抗衡离子溴化物浓度的监测表明，在整个传输实验过程中，HDTMA和溴化物缓慢但持续地解吸，这导致沸石上表面活性剂双层结构的上层被剥离。HDTMA表面活性剂表面构型从双层变为单层导致改性沸石表面吸收和固定铬酸盐的功能丧失。
