Valorization of tannery wastes: Lipoamino acid surfactant mixtures from the protein fraction of process wastewater

Abstract

Abstract The first stages of the transformation process of hides into leather (beamhouse process) generate an important waste in the tanning industry, since a considerable fraction of solubilized proteins ends up in waste water with the corresponding increase in contamination parameters, especially when the process is carried out without hair recovery (hair-pulping process). The objective of this work was the valorisation of this waste (the separated protein fraction) which conveniently hydrolyzed to amino acid level constituted the starting material for the production of biodegradable surfactants. The lipoamino acid surfactants were obtained by acylation of the amino acids from the protein hydrolysate. These surfactants were characterized and their physico-chemical and biological properties evaluated. They exhibit very low cmc values (about 40 mg/L). These surfactants are readily biodegradable and present an aquatic toxicity significantly lower than many common commercial surfactants derived whether from renewable or petrochemical feedstock. The mixtures of surfactants obtained are able to form oil/water emulsions that remain stable for at least 1 year. The results obtained in this work confirmed that it is possible the production of biodegradable and efficient lipoamino acid surfactant mixtures from the protein fraction present in beamhouse process wastewaters. This study constitutes a promising approach for the reduction of the pollution load from industrial tannery wastes and its valorisation as raw material for the production of surfactants with excellent environmental properties and good technical properties.