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The float with high non-ionic surfactant content coming from aqueous degreasing of sheepskins is one of the main COD sources for the wastewater stream to be treated in the tannery.
The system developed for recycling the surfactant of the aqueous degreasing of sheepskins, consists in a thermal emulsion breaking of the supernatant of the bath, and the selective separation of surfactant and fat in two liquid phases and further the evaporation of the solvents used in the extraction.
This system allows the reduction of the pollutant load in the waste water and the valorisation of the solid waste generated in the separation of fat and surfactant, by means of recovering the surfactant to the process and obtaining purified fat that can find use in lubrication industry.
Emulsion breaking is carried out by heating into a decantation tank operating during few hours, with discontinuous shaking. Then, it rests during some hours for the following decantation of the two-formed phases:
Surfactant and fat are recovered by extraction process with heptane and ethanol. Later, through a conventional distillation the solvents are recovered and fat and surfactant are separated.
One of the main advantages of the process is that 75% of the surfactant used for sheepskins degreasing can be recovered, and the wastewater pollution is reduced in COD values around 90%. Solid waste generation is reduced and the energy linked with its incineration process is also reduced.
The main innovations that this technology shows are:
The advantages of the technology with regard to the existing systems on the market are:
The technology is available for tanneries and tanners consortium working with sheepskins from raw or pickle stage that use aqueous degreasing processes with non-ionic surfactants.
AIICA offers Pilot Plant to carry out different trials, design, the equipment and technical assistance, as well as the recycling of surfactant produced in the process
