氢氧化钠碱熔-电感耦合等离子体发射光谱法测定海域砂矿中钛锆铝铁锰硅磷

Determination of Ti, Zr, Al, Fe, Mg, Si and P in Offshore Placer Deposits by Inductively Coupled Plasma-Optical Emission Spectrometry with Sodium Hydroxide Fusion

  • 摘要: 近海海砂资源蕴藏着丰富的重矿物砂矿资源,包括锆石(ZrSiO4)、钛铁矿(FeTiO3)、金红石(TiO2)、锐钛矿(TiO2)、独居石[(Ce,La,Nd,Th)PO4]、石榴子石族矿物等,开发潜力大。本文建立了一种基于氢氧化钠碱熔-盐酸复溶联合振荡器振荡脱埚-电感耦合等离子体发射光谱法,用于同时测定海域砂矿中钛、锆、铝、铁、锰、硅、磷元素含量。样品采用低熔点的1.0g氢氧化钠作为熔剂,在650℃下熔融30min,冷却后将坩埚连同熔融物一并放入20%的盐酸溶液中复溶,在恒温振荡仪中进行振荡溶解。通过对熔剂用量、熔样时间、脱埚振荡时间进行优化,解决了传统碱熔法在处理难溶硅酸盐海域砂矿时引起的高温爆沸、腐蚀坩埚、脱埚不彻底、前处理繁琐问题。样品处理方法操作简单,通过控制盐酸浓度,既中和了过量碱性熔剂,又避免了高浓度酸液对镍坩埚的剧烈腐蚀,延长了坩埚使用寿命,通过机械振荡促进了熔融产物均匀溶解,确保目标元素完全释放至溶液中。在最佳条件下,测定海域砂矿中SiO2、Al2O3、Fe2O3(总铁)的检出限在0.01%~0.06%,Mn、P、Ti、Zr的检出限为2.67~14.30µg/g,RSD在0.56%~4.67%。经过多种一级国家标准物质验证,各元素相对误差均≤4.57%,满足《地质矿产实验室测试质量管理规范》要求。

     

    Abstract: Offshore sand deposits contain abundant heavy mineral resources, such as zircon (ZrSiO4), ilmenite (FeTiO3), rutile (TiO2), anatase (TiO2), monazite (Ce,La,Nd,Th)PO4, garnet and so on, and therefore exhibit substantial development potential This study establishes a method that integrates NaOH alkali fusion, oscillator-assisted crucible release via HCl redissolution, and inductively coupled plasma optical emission spectrometry, in order to simultaneously determine the contents of titanium, zirconium, aluminum, iron, manganese, silicon, and phosphorus in marine placer deposits. A 1.0g of low-melting NaOH is used as flux to fuse the sample at 650˚C for 30 min. After cooling, the crucible together with the melt are transferred into a 20% HCl solution, and dissolution is completed by shaking in a constant temperature oscillator. Systematic optimization of flux mass, fusion duration, and oscillator-assisted crucible release time eliminates the high-temperature bumping, crucible corrosion, incomplete crucible-releasing, and cumbersome sample pretreatment. The procedure is streamlined yet analytically robust. Careful manipulation of the HCl concentration, not only neutralizes the residual alkaline flux, but also suppresses aggressive acid attack on the nickel crucible, substantially prolonging its service lifetime. Coupled with controlled mechanical agitation, the protocol ensures homogeneous dispersion and rapid solubilization of the molten residue, facilitating quantitative liberation of the target analytes into the solution phase. Under optimal conditions, the detection limits of this method for SiO2, Al2O3, and Fe2O3 (total iron) in offshore placer deposits are between 0.01% and 0.06%, while the detection limits for Mn, P, Ti, and Zr range from 2.67µg/g to 14.30µg/g, with a precision not exceeding 4.67%. After verification with various primary national standard reference materials, the relative error of each element is ≤4.57%, meeting the requirements of “The Specification of Testing Quality Management for Geological Laboratories”.

     

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