Tannin Extraction of Rhizophora Bark from Residual Charcoal Production

Trairat Neimsuwan, Pornpun Siramon, Pongsak Hengniran, and Vittaya Punsuvon



Mangrove bark, (more than 200,000 m3 per year or 80,000-100,000 tonnes in oven dry weight) the residue from traditional charcoal production in Thailand, contains a large amount of tannin. The objectives of this research were to determine the chemical composition of mangrove bark, to investigate the tannin extraction conditions, and to investigate the chemical analysis of tannin from mangrove bark waste from the production of charcoal in Yeesan, Samut Songkram province, central Thailand. The chemical composition was analyzed using the TAPPI standard and the Browning method. Sodium sulfite (0, 2, or 4%) or sodium carbonate (0, 0.5, or 1%) were used as salt catalysts. Distilled water, 50% methanol, or 50% acetone were used as extraction solvents. The optimal conditions for obtaining additives for use in wood adhesive involved extraction under reflux conditions for 3 hr using a 100:500:4:1 by weight ratio of bark sample: acetone-water 50:50 volume/volume (v/v): sodium sulfite:sodium carbonate. These conditions produced the highest Stiasny number (87.69%). The extracts were characterized using Fourier-transformed infrared spectroscopy. Absorbance at 4000-600 cm-1 was detected for tannin extracts and revealed the presence of catechin as the main condensed tannin in the extracts.