Preparation of spherical activated phenol-formaldehyde beads from bamboo tar for adsorption of toluene

Abstract

Bamboo tar is a waste by-product from the process of bamboo charcoal production. After distillation under reduced pressure, bamboo tar becomes a highly viscous liquid containing phenolic compounds at more than 70 wt%. Therefore, bamboo tar could be an excellent replacement for the phenolic compounds produced by the decomposition of petroleum. In this study, bamboo tar was mixed with formalin under a weak alkaline condition to form cured phenol-formaldehyde (PF) beads through suspension polymerization. In total, 35% of the obtained PF resin produced spherical beads with a particle size ranging from 9 to 16 mesh. The char yield after 500°C carbonization was 60.4 wt%, according to thermogravimetric analysis. This high char yield is advantageous for the subsequent activation process. After physical activation using CO2 at 900°C for 2 hr, the carbide yield was up to 73.0 wt%. The specific surface area of activated PF beads was dependent on the activation time and temperature. Toluene adsorption results suggest that the activated PF beads are applicable to the adsorption and recovery of VOC gases. Monolayer adsorption may limit the VOC adsorption with activated PF beads because the adsorption isotherms were better fitted with the Langmuir model. Implications: Bamboo tar is shown to be a good replacement for the phenolic compounds from decomposition of petroleum to form activated phenol-formaldehyde (PF) beads. Toluene adsorption tests suggest that the activated PF beads have potential to adsorb and recover VOC gases. Nevertheless, due to the low specific surface area of the activated PF beads from bamboo tar, a further enhancement in both meso- and microporosity is needed in the future experiments. The experimental data provide a contribution to better understanding the possibility of resource recovery of waste agricultural by-products and their potential application in environment protection.