Comparative Characterization of Soaps Prepared from Plant-sourced Alkali Solutions and Caustic Soda

Abstract One of the basic ingredients of modern soap making is synthetic alkali such as caustic soda or lye (NaOH). The utilization of plant-based alkalis to make soap has been compared to the use of synthetic caustic alkalis (sodium hydroxide). Synthetic alkalis cause significant adverse effects on the environment which may be drastically reduced by using plant-based alkalis. Nigeria is an agrarian economy ranked among the first five largest producers of both plantain (Musa paradisiaca) and oil palm (Elaeis guineensis) in the world, thus generating large amounts of wastes from both plants. Hence, to reduce these wastes and effluents from synthetic alkali, improve environmental aesthetics, and create a new economy, plant-based alkalis were produced from the ashes of unripe plantain peels (UPP) and oil palm bunches (OPB) and used for soap making and the as-prepared soap were compared to soap from synthetic caustic soda. Alkali and soap properties such as alkali strength, mineral contents, soap solubility, soap pH and conductivity, lathering, moisture contents, and bulk density of the soaps were compared. Results showed that UPP had higher ash content than the OPB, though both ashes contained high mineral contents especially for Na and K. The UPP had slightly higher soap pH and conductivity than the OPB. Soap from the synthetic caustic soda (SCS) lathered more than both the biomass-based soaps in both distilled and hard water, though the biomass-based soaps have better solubility compared to the SCS soap. The textures of the biomass-based soaps were slightly softer than the SCS soap, and the bulk density of the UPP was far higher than those of the OPB and the SCS. The pH values of both plant-based soaps were higher than the SCS pH as well as the usual pH values of soaps to be used for skin wash (pH 8 to 10) and thus should not be used as skin wash as it is likely to irritate the human skin. The soaps may be used for laundry, dish washing, and other cleaning purposes.