Authors: S. Arasaretnam, R. Joy Ebenezer
This study aims to find out the feasibility of using tannin extracted from the mature pods of Acacia farnesiana as a substitute for phenol in formaldehyde resins, and to investigate cation adsorption performance of this novel resoles for Na+ and Ca2+ ions. The polyphenolic extract of A. farnesiana pods were subjected to qualitative and quantitative the analysis to detect and determine the amount of tannin present. Qualitative tests revealed the presence of a hydrolysable tannin harboring galloyl ester moieties. The mature pod of A. farnesiana revealed that ≈24 % of tannin is making it one of the richest tannin sources in the plant kingdom. Formaldehyde based resins with varying tannin to phenol ratios were prepared. The resins synthesized were subjected to sulfonation to enhance their ion exchange capacities. A Fourier Transform Infrared Spectrophotometer equipped with an attenuated total reflection accessory was used to monitor the formation of ether and sulfonic acid group in the novel resins. The highest adsorption capacity for Na+ (0.70 meq g-1) was shown by the sulfonated resin with a tannin to phenol ratio of 3:1, while the sulfonated resin with a 0:1 tannin to phenol ratio displayed the highest adsorption for Ca2+ (0.24 meq g-1). Three novel sulfonated resins were found to be more efficient in adsorbing Ca2+ ions and have the potential to be utilized in hard water treatment and decalcifying processes.
Keywords: Tannin, Acacia farnesiana, phenol, formaldehyde resole resins, adsorption, polyphenolic, sulfonation, ion exchange capacities.