FeOOH改性玄武岩纤维整体式材料对磷的去除性能及机理

Performance and mechanism of the monolithic material of FeOOH-modified basalt fiber on phosphate removal

尽管微纳米材料具有优异的环境净化功能,但直接应用微纳米材料具有潜在的生态环境威胁。本研究以惰性玄武岩纤维为基底材料,通过表面活化-Fe3+原位水解方法制备功能性整体式材料(FeOOH@BF)并研究其对水中磷的去除性能。X-射线衍射(X-ray diffraction, XRD)测试显示,在玄武岩纤维表面原位生长的羟基氧化铁(FeOOH)具有α、β两种晶体相结构。FeOOH的附着导致惰性玄武岩纤维表面具有丰富的活性铁羟基吸附位点。吸附结果表明,FeOOH改性的玄武岩纤维整体式材料可有效去除水中的磷酸根。当水中磷含量超过V类地表水质量标准10倍时,5 g·L^(-1)的FeOOH@BF对水中磷的去除率高于80%。FeOOH@BF对水中磷的去除率随着磷初始质量浓度和pH的增大而降低。动力学吸附结果表明,FeOOH@BF对水中磷的吸附过程在达到饱和吸附以前适合用准一级动力学吸附方程描述。吸附饱和后的FeOOH@BF在0.05 mol·L^(-1)的HNO_(3)溶液中经过浸泡12 h再生后,其对磷的吸附容量出现明显的降低,但仍能有效去除水中的磷酸根;当饱和吸附后的FeOOH@BF在HNO_(3)溶液中浸泡24 h再生后,FeOOH@BF仍可有效去除水中的磷且吸附性能趋于稳定。FeOOH@BF材料表面的铁羟基发生去质子化释放H+离子,导致磷酸根质子化形成HPO_(4)^(2-),并进一步与材料表面的铁羟基发生配体交换、离子交换和氢键等作用,进而被玄武岩纤维表面包覆的FeOOH所吸附。

Although the micro/nano-materials have good performance on environment purification,but their direct use will cause potential risk on safety of ecosystem.In this work,the inert basalt fiber was taken as the base material,its surface was activated by NaOH solution and was hydrolyed in Fe3+solution,then the monolithic material(FeOOH@BF)was prepared for phosphate removal from water.The crystal covered on the surface of basalt fiber was goethite and lepidocrocite,α-andβ-FeOOH identified by XRD,these FeOOH could endow the inert basalt fiber with active sites of hydroxyl(Fe-OH)for adsorption.The adsorption experiments demonstrated that FeOOH@BF could effectively remove the phosphate in water.When the concentrate of phosphate was over 10 times that of the allowable value of phosphate in the V standard of surface water,the removing ratio of phosphate by FeOOH@BF was higher than 80%at 5 g∙L^(-1) of FeOOH@BF dosage.And the removing ratio of phosphate on FeOOH@BF decreased along with the increase of initial concentration of phosphate and pH.The kinetic adsorption showed that the process of P adsorption on FeOOH@BF before saturation adsorption could well fitted the pseudo first-order reaction.Moreover,the FeOOH@BF could still effectively adsorb phosphate from water after regeneration by soaking in 0.05 mol∙L^(-1) HNO_(3) for 12 h though its P adsorption capactiy decreased obviously.FeOOH@BF still effectively adsorb phosphate from water with a tendency of stable P adsorption performance after regeneration for 24 h in the HNO_(3).Further,the adsorption mechanism was investigated by FT-IR spectrum and fitting technology over Guassian function.It was found that the Fe-OH could deprotonate in solution and release H+from the FeOOH@BF to solution,then phosphate in solution would combine with H+and form HPO_(4)^(2-)species,following by the adsorption by FeOOH@BF through ligand exchange,ion exchange and hydrogen interaction with hydroxyl(Fe-OH)on its surface.