Pretreatment method for the determination of total organic carbon in sodium aluminate solution by potassium dichromate titrimetry

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 K2Cr2O7 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%.