Preparation of Laundry Soap from Used Cooking Oils: Getting value out of waste

Abstract

Palm oil is commonly used to prepare laundry soap by treating it with alkaline solutions. However, using it for this purpose is becoming expensive as palm oil is imported from few major exerting countries. Moreover, it is used for biodiesel production. Therefore, looking for alternative raw material that substitutes palm oil for soap production is imperative. Used cooking oils (UCOs) are good candidates in this regard. In the present study, laundry soaps were prepared using UCOs and sodium hydroxide solution. The cleaning actions and physicochemical properties were evaluated and compared with that commercial soaps purchased from local market. The pH, moisture content, free caustic alkali, % chloride and total alkali content values of the prepared soap materials were found to be in range of 9.31 to 10.56, 6.67 to 14.47%, 0.19 to 0.22%, 0.12 to 0.21%, 0.78 to 1.09%, 75.42 to 88.53%, 70.35 to 84.68%, 0.98 to 1.52%, and 0.28 to 0.67%, respectively. The results obtained in this study were comparable with the physicochemical properties of the commercial soap products used in the study. Moreover, the observed data were comparable with similar data reported in literature and East African Standards (EAS) suggesting that UCOs can be used as raw materials to prepare good quality laundry soap by replacing imported palm oil. Key words: Laundry soap, used cooking oil, saponification, physicochemical properties, saponification.