聚合硅酸解聚-硅钼蓝分光光度法测定矿石中二氧化硅

来源期刊：冶金分析2010年第9期

论文作者：张建珍 王锦荣 刘家齐

文章页码：65 - 69

关键词：解聚； 聚合硅酸(nH₄SiO₄)； 正硅酸(H₄SiO₄)； 分光光度法； 氟化铵-三氯化铝(NH₄F-AlCl₃·6H₂O)； 抗坏血酸-盐酸羟胺

Key words：deploymerization； polymerized silicic acid (nH₄SiO₄)； normal-silicic acid (H₄SiO₄)； spectrophotometry； ammonium fluoride-aluminium chloride(NH₄F-AlCl₃·6H₂O)； ascorbic acid-hydroxylamine hydrochloride

摘    要：针对矿石中的二氧化硅通常含量较高,制取母液时大量硅酸产生聚合的问题,建立了以氟化铵-氯化铝作为聚合硅酸(nH₄SiO₄)解聚剂、钼酸铵作为显色剂和抗坏血酸-盐酸羟胺作为还原剂测定高含量二氧化硅的的分光光度法。实验表明,室温25℃时,在HCl浓度为0.25～0.35 mol/L,氟化铵-氯化铝混合液体积为10 mL,反应时间为25 min时,聚合硅酸(nH₄SiO₄)可被完全解聚生成正硅酸(H₄SiO₄)。正硅酸和钼酸铵反应生成硅钼杂多酸(硅钼黄),而后被5 mL抗坏血酸-盐酸羟胺还原为硅钼蓝,于波长680 nm处进行吸光度测定。二氧化硅的质量浓度在0～12 mg/L范围内符合比尔定律,其表观摩尔吸光系数为5.65×10⁶ L·mol^-1·cm^-1。检出限为0.028 mg/L。使用本法对铁矿、铝土矿等标准样品中二氧化硅进行了多次测定,结果与认定值相符,相对标准偏差(RSD)在0.63%～2.1%(n=6)之间。

Abstract: The content of silicon dioxide in ores was generally high,so much silicic acid would have polymerized problem during the preparation of mother solution.In this study,a spectrophotometric determination method of high-content silicon dioxide was established using ammonium fluoride-aluminium chloride as the depolymerizing agent of polymerized silicic acid(nH₄SiO₄),ammonium molybdate as coloring agent,and ascorbic acid-hydroxylamine hydrochloride as reducing agent.The results showed that,the polymerized silicic acid(nH₄SiO₄) could be completely depolymerized to nomal-silicic acid(H₄SiO₄) at 25 ℃ under the following conditions: the concentration of HCl was 0.25-0.35 mol/L,while the volume of ammonium fluoride-aluminium chloride was 10 mL,and the reaction time was 25 min.The normal-silicic acid reacted with ammonium molybdate to form silicomolybdic acid (molybdenum yellow),which could be reduced to molybdenum blue by 5 mL of ascorbic acid-hydroxylamine hydrochloride.Absorbance of the solution was measured at 680 nm.Beer’s law was obeyed for silicon dioxide in the range of 0-1.2 mg/L.The apparent molar absorptivity was 5.65×10⁶ L·mol^-1·cm^-1,and the detection limit was 0.028 mg/L.The proposed method has been applied to the determination of silicon dioxide in the certified reference materials of iron ore and bauxite,and the results were consistent with the certified values with relative standard deviation(RSD,n=6) of 0.63%-2.1%.