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Abstract
Sodium cardanol sulfonate surfactant was synthesized from cardanol from cashew nut shell liquid. Surfactant properties of cardanol sulfonate were determined and compared with dodecylbenzene sulfonate. Surface tension values were determined to be 32.25 mN/m for cardanol sulfonate at 20% w/v and 28.00 mN/m for dodecylbenzene sulfonate at 15% w/v. Critical micelle concentrations of dodecylbenzene sulfonate and cardanol sulfonate were found to be 0.435 and 0.372 mol/L, respectively. In comparison with dodecylbenzene sulfonate, the relative detergency of cardanol sulfonate was calculated to be 93.7% compared to dodecylbenzene sulfonate. Results suggest that cardanol sulfonate can be used as alternative anionic surfactant.
Keywords Sodium cardanol sulfonate * Synthesis of surfactant * Cashew nut shell liquid
Introduction
Cashew nut shell liquid (CNSL), which is extracted from the nut shell of the cashew tree Anacardium occidentale, occurs as a reddish brown viscous liquid in the soft honeycomb structure of the shell of the cashew nut. The cashew nut is attached to the cashew apple and is grey colored, kidney shaped and 2.5-4.0 cm in length. The shell is about 0.3 cm thick, having a soft leathery outer skin and a thin hard inner skin. Between these skins is the honeycomb structure containing the phenolic material popularly called CNSL. Inside the shell is the kernel wrapped in a thin brown skin, known as the testa. The nut thus consists of the kernel (20-25%), the shell liquid (20-25%), and the testa (2%), the rest being the shell.
CNSL is classified into two types, solvent-extracted CNSL and technical CNSL. A typical solvent-extracted CNSL contains anacardic acid (60-65%), cardol (1520%), cardanol (10%) and traces of methyl cardol (Fig. 1). Technical CNSL is obtained by roasting shells and contains mainly cardanol (60-65%), cardol (15-20%), polymeric material (10%), and traces of methyl cardol [1].
Cardanol is a mixture of a four components: saturated (~5%), monoene (~49%), thene (16.8%) and triene (29.3%) [1, 2]. Typical applications of cardanol include brake linings, paints and varnishes, foundry core oil, and distilled cardanol for epoxy resins and laminates. The other minor uses of cardanol are, for example, in chemically resistant cements, oil tempered hardboard, and water-proofing compounds and resins [1, 3, 4].
Nowadays, in the chemical industries, anionic surfactants such as sodium dodecylbenzene sulfonate are used extensively. The...