Valorization of cashew nut processing by-product: development of a cardol/starch biopolymer composite with electrochemical properties and technological potential

Abstract

The problem of food agro-industry residues represents a growing concern in our society, therefore its use as a raw material to obtain biopolymers of technological interest is an attractive alternative. The objective of this work was to assess the viability of utilizing cardol, derived from cashew nut shell liquid, in the production of a biopolymer composite by combining it with cassava starch. The biopolymer composite was prepared by thermochemical method using different cardol concentrations and varying the synthesis pH. The results allowed us to demonstrate the formation of cardol/starch biopolymeric films. The infrared spectra showed possible interactions by hydrogen bonds between the cardol and the glucose units of the starch. The impedance behavior showed a similar conduction mechanism in all cases, allowing the establishment of a single equivalent circuit. The electrochemical parameters showed that the presence of cardol and the lower pH increased the values of the electrical resistance and the double layer capacitance in the biopolymers. In addition, the values of the CPE/Rre system, related to the electractivity, were not affected by the pH, but by the presence of cardol. The biodegradability tests showed a complete decomposition of the biopolymer composite films in three stages in a period of 17 to 19 days. It could be concluded that it is possible to use the cardol extracted from the cashew nut shell liquid to elaborate a biopolymer composite with electrochemical properties when combined with cassava starch. The electrical properties of the biopolymer can be modulated by varying the synthesis pH and the amount of cardol used. The composite cardol/starch biopolymer could be used as a biopolymeric solid electrolyte in the manufacture of batteries, capacitors, etc