Physicochemical properties of Na-soap and metal soaps (Ca and Al) from candlenut oil

Metal soaps are metal salts with fatty acids. The substances can be produced by the saponification reaction of fatty acids and inorganic salts. An alternative for synthesizing metal soaps is from triglycerides, particularly vegetable oils with their inorganic salts. The synthesis alternative is more economically advantageous because it does not require single fatty acids. The purpose of this research is to synthesize metal soap from candlenut oil. This oil is used because its availability is quite abundant in Indonesia. The research was carried out through the following stages (1) synthesis of Na-soap through saponification reaction, (2) synthesis of Ca-and Al-soaps through trans-saponification reaction, (3) characterization of the synthesized metal soap including shape, color, melting point, solubility in water, methanol, ethanol, chloroform, n-hexane, and (4) structure identification using FT-IR, XRF, SEM, and XRD. The results of XRF analysis showed that the conversion of Na-soap to Ca-soap and Al-soap was 99.35% and 87.20%, respectively. The results of FT-IR analysis showed that stretching vibration of characteristic group for metal soap, i.e., CO as COO-(carboxylate ion). Synthesized metal soaps are solid powders. Na-soap is yellowish in color, melting point 205-214°C, Ca-soap is yellowish white, melting point 118-133ᵒC; and Al-soap is bone white in color, melting point 212-222°C. Na-soap is soluble in water, methanol, ethanol, slightly soluble in chloroform and insoluble in n-hexane. Ca-and Al-soaps are soluble in chloroform and insoluble in water, methanol, ethanol, n-hexane. The results of SEM analysis show that Na-soap has a spherical shape while the Ca and -Al soaps have a random plate shape. XRD analysis of synthesized metal soaps obtained a value of 2θ = 14-30° which indicates the presence of long-chain fatty acids with an amount of C18 or more.