重铬酸钾滴定法测定铝酸钠溶液中有机碳的预处理方法

摘要

探讨了贵州高硫高铝铝土矿溶出液即铝酸钠溶液中有机碳的重铬酸钾滴定测定方法,重点考察了干扰离子即氯离子和硫离子的预处理方法.其中,氯离子采用H2SO4大量除去,然后进一步用HgSO4除去剩余的少量氯离子；低硫离子则在稀H2SO4溶液中通过一系列的反应最终生成为SO2除去.实验表明,预处理后氯离子和硫离子的干扰基本消除.通过预处理方法消除干扰离子后,用过量K2Cr2O7-H2SO4(浓)将有机物氧化成二氧化碳,剩余的K2Cr2O7用Fe2+标准溶液回滴,由此计算出铝酸钠溶液中的有机碳含量.方法测定铝酸钠溶液中有机碳,其结果与国标方法一致,回收率为97％～100％,RSD为0.93％.%The determination method of organic carbon in leaching solution of Guizhou high-sulfur and high-aluminum bauxite, i. e. , the solution of sodium aluminate, by potassium dichromate titration was studied. The pretreatment method of interference ions (chlorine and sulfur) was investigated. Most of chlorine ions were removed by H2SO4 , and the little residual chlorine ions were further removed by HgSO4. The low-sulfur ions were removed in form of SO2 by a series of reactions in diluted H2SO4 solution. The results showed that, the interference of chlorine and sulfur ions could be eliminated after pretreatment. Then, the organic matters were oxidized to carbon dioxide using excessive K2Cr2O7-H2SO4 (concentrated). The residual K2Cr207 was back titrated with Fe2+ standard solution. The content of organic carbon in sodium aluminate solution could be calculated. This method was applied to the determination of organic carbon in sodium aluminate solution, and the results were consistent with those obtained by the national standard method. The recoveries were 97%-100%, and the relative standard deviation (RSD) was 0. 93%.