Investigation of clay minerals (Kaolinite and halloysite) as a green leather tanning agent

Abstract

Tanning involves the stabilization of hides and skins with the use of organic or inorganic chemicals. Inorganic tannings include chromium tannage, alum tannage, zirconium tannage, etc. Among these, chrome tannage is the most preferred tanning method due to the superior properties it impacts on leather. Despite its popularity, there has been a rising concern about the environmental impact brought about by chromium tanning and as a result, researchers have embarked on a search for a more suitable alternative to chromium tanning. This study explored the use of clay as an economical and eco-friendly tanning agent. XRD and XRF analysis was done to identify the type of clay obtained from Murang’a quarry, Kabuta region in Kenya, and determine its physical and chemical composition. The finding indicated that the two clays were kaolinite and halloysite. Their XRD peaks were observed at a basal spacing of 7.14o and 7.2o respectively with SiO2 and Al2O3 being the major elements with percentages ranging between 50%-40% and 40%-25% respectively. The clay samples were then modified using concentrated formic acid and used to tan goat skin. The physical properties of leathers obtained were analysed using IUP standard method which included the tensile strength and elongation at break, shrinkage temperature, tear strength, grain crack, and grain burst tests. From the results, both leathers tanned with kaolinite and halloysite had attained the minimum recommended values for all the tests. Moreover, leather tanned using halloysite had better physical properties compared to that tanned using kaolinite. From this study, clay can be used as an alternative tanning agent to chromium.