Separation of carcinogenic aromatic amines in the dyestuff plant wastewater treatment

A new method of separation of carcinogenic aromatic amines in wastewater is given. With the lower pH value (pH ≤ 2.0), it is effective to restrain the electroosmotic flow (EOF). At the same time, the migration time of the electroosmotic flow is more than 110 min, and the migration time of aromatic amines is less than 15 min. As a result, a capillary zone electrophoresis (CZE) system of lower electroosmotic flow was established. Seven aromatic amines were separated by the CZE with lower electroosmotic flow. In the system, the aromatic amines are combined with protons under condition, and they have positive charges. Therefore, the sample entered the capillary at the positive electrode and was detected at the negative electrode. The experiment revealed that the migration time of aromatic amines increased quickly with a slight increase in the pH value in CZE at lower electroosmotic flow. The retention order of peaks of aromatic amines is related to their pKb and the numbers of amino and acidic groups. When the number of amino groups gets larger, the pKb becomes smaller, and the peaks elute earlier. The acidic group of aromatic amines makes the peaks to elute later; the pH 1.7 was chosen. When the NaH2PO4 concentration was 20–60 mmol/L, the migration time of aromatic amines increased quickly. And then the 40 mmol/L concentration was chosen. The optimal conditions were 40 mmol/L NaH2PO4 (pH 1.7).