Recycling of waste to chromium tanning through the recovery of chromium for sedimentation.

Chromium tanning is used for the production of an end product of better quality at lower costs. However of its high level of toxicity it may damage the environment. The treatment of chromium tanning requires special precautions. Therefore, the minimization of damages at the source is of great importance, providing an end effluent within the standards set by law. This work has as its main objective the study of a way of minimizing the risks at the very source. The alternative was chromium precipitation in hydroxide form, using for a precipitant the sodium hydroxide 12 M and commercial liquid caustic soda at 50%. Jar tests and clarified analysis with Atomic Absorption Spectrophotometer were made to measure chromium concentration. The results presented a chromium III average clarified of 40,67 mg L in pH 8 and rotation time of 2 hours, of 14.53 mg L in pH 8, and rotation time of 4 hours, 1.38 mg L in pH 10, and rotation time of 2 hours and 1.36 mg L in pH 10 and rotation time of 4 hours; this can be sent to the Sewage Treatment Station (STS) or can be used in the pickling bath, a stage preceding tanning.