Extraction and recovery of sulphides from tanneries wastewater

Abstract

The wastewater of tanneries contains high concentrations of sulphides generated in the process of peeling skins that generate emissions of hydrogen sulphide of high toxicity.

In order to encourage the implementation of cleaner technologies in these industries, the extraction and recovery of sulfides were evaluated from tannery discharges, which can be reused in the peeling skins process.

The mixed wastewater from the washing, peeling, untangling, tanning and dyeing processes of cattle skins from a tanning industry in the San Benito sector in Bogotá were treated. Acid pH was adjusted from 2 to 6 and by means of agitation in a closed tank the extraction of gases generated from hydrogen sulfide was carried out, which reacted with sodium hydroxide solution, producing sodium sulphide. The sulphide concentration was determined by iodometry.

Total sulphide extraction was achieved for all pH values tested, treatment time between 45 and 90 minutes and stirring speed 120 rpm with the recovery of the same in caustic soda solution producing sodium sulfide which is the raw material used for the peeling skins, allowing their reuse in this process.