Bleaching of Brazilian kaolins using organic acids and fermented medium

The use c f kaolin for both coating and filler applications in the paper industry requires a high brightness grade, so that treatment for the removal of iron, which adds color to the mineral decreasing its commercial value, is required. Bleaching of kaolin is usually carried out by reductive leaching of iron, producing effluents of considerable environmental concern. Despite little investigation, the use of organic acids seems to be a good alternative for the iron removal with the additional advantage of producing less-aggressive effluents. aper presents a study of bleaching treatments with different samples of Brazilian kaolins using organic acids and fermented medium from Aspergillus niger cultivation as the leaching agent. The studies showed more effectiveness when oxalic acid and fermented medium were used. The brightness of a kaolin sample reached the levels for filler clay (sample not submitted to magnetic separation) and coating clay (sample submitted to magnetic separation), when fermented medium and oxalic acid were used as a bleaching agent. These results could not be obtained by more conventional methods.