沸石的载铁改性及除氟性能分析

Modification and fluoride-adsorption capacity of natural zeolite with Fe^(3+)

以天然沸石为基质材料,采用硫酸、氢氧化钠和氯化铁对其改性,对模拟含氟水进行静态吸附试验,研究改性沸石对水中氟离子的吸附性能,探讨并提出了最佳改性条件。对沸石进行比表面积和孔径分布测定,并利用X射线荧光分析沸石改性前后的元素组成及含量变化。结果表明采用氯化铁单独改性效果最好。吸附速率可用拟二级动力学方程描述。氯化铁改性沸石对F-的吸附符合Langmuir吸附等温模式,饱和吸附量为0.087 mg·g-1,较未改性沸石有很大提高,吸附平衡常数为0.28 L·mg-1。改性后沸石的比表面积减小,Fe元素含量增加,Ca2+、Mg2+等离子的含量降低,说明氯化铁改性沸石除氟主要基于化学吸附与复杂的离子交换作用。

Natural zeolite was modified with sulfuric acid, sodium hydroxide, and ferric chloride solution, respectively. Defluorination ability of modified zeolite was studied through adsorption experiments. The optimal condition for modification of the natural zeolite was determined. The specific surface area and pore size distribution of the zeolite before and after modification were compared. The composition and content of elements in the natural zeolite and ferric chloride modified zeolite were determined using XRF. The results showed that ferric chloride was the best for fluoride removal from the natural zeolite. The fluoride adsorption rate of ferric chloride from the zeolite can be expressed with pseudo-second-order kinetics. The equilibrium adsorption data fitted well to Langmuir adsorption isotherm with the maximum fluoride adsorption capacity of 0.087 mg·g^-1, which was greatly improved compared to the unmodified zeolite. The equilibrium constant was 0.28 L·mg^-1. The specific surface area of the modified zeolite decreased and the content of Fe element increased, while Ca^2 ＋, Mg^2 ＋ content reduced, indicating that the mechanism of fluorine removal is mainly resulted from chemical adsorption and complicated ion exchange.