石英砂表面铁胶膜的合成--pH和铁摩尔比[Fe(Ⅱ)]/[Fe(Ⅲ)]的影响

Synthesis of Iron Cutan on the Surface of Quartz Sand——the Influence of pH and Iron Mole Ratio [Fe(Ⅱ)]/[Fe(Ⅲ)]

本研究以石英砂为载体,在其颗粒表面合成铁胶膜,并探讨合成体系不同初始pH(5,6,7)及铁摩尔比(R=[Fe(Ⅱ)]/[Fe(Ⅲ)])等条件对铁胶膜形成的影响。研究表明,在初始pH相同的情况下,当R为0时,铁胶膜的矿物成分为弱晶质的水铁矿;R为0.01时的矿物成分为赤铁矿;R分别为0.02、0.04、0.06和0.10时为针铁矿,且随着R增加,X射线衍射(XRD)图谱中针铁矿的峰强度逐渐增加,扫描电镜(SEM)可观察到针铁矿晶形逐渐变大,且在R为0.10时晶体形貌最大;当R为0.50和体系只加入Fe(Ⅱ)时合成的铁矿物主要为针铁矿与磁铁矿的混合物。当R一定时,随着合成体系初始pH的增加,胶膜中针铁矿的XRD峰强度逐渐增强,在初始pH为7时其峰最强,且晶形逐渐变大。

Iron cutans coated on the surface of quartz sand were synthetized to investigate the influence of initial pH（5,6,7） and iron mole ratio（R=[Fe（Ⅱ）]/[Fe（Ⅲ）]） of the synthesis systems on the formation of iron oxides in the cutans.Results were as follows：（1） At initial pH 7,mineral composition of iron cutan was ferrihydrite with weak crystallization when R was 0 and it was hematite when R was 0.01 in the synthesis system.Goethite was the only iron oxide in the cutans when R were 0.02,0.04,0.06 and 0.10 at initial pH 7,respectively.With the increase of R,the peak intensity of goethite in X-ray diffraction（XRD） patterns increased successively and the crystalline shape of iron oxide in the cutans analysed by scanning electronic microscope（SEM） became large.The crystal was the biggest when R was 0.10 at initial pH 7.The mineral composition was a mixture of goethite and magnetite when R was 0.50 and only Fe（Ⅱ） existed at initial pH 7 in the synthesis systems;and（2） When R remained constant in the goethite synthetized system,with the increase of the initial pH from 5 to 7,the peak intensity of goethite in XRD patterns increased successively and the crystal of iron oxides in the cutan became bigger compared with the condition with other initial pH,and it reached the maximum at initial pH 7.