Preparation, characterization of carboxylated bamboo fibers and their adsorption for lead(II) ions in aqueous solution

The present study was conducted to develop a simple and versatile method to prepare carboxylated bamboo fibers which can be applied as potential bio-adsorbent for metal ions removal due to the high content of carboxyl groups. The chemical modification of bamboo fibers with citric acid (CA) was carried out by friendly semi-dry oven method. The resulting products with carboxyl group content between 1.99 and 4.13 mmol/g were accessible by changing ultrasonic pretreatment time, reaction temperature, reaction time and the amounts of catalyst and citric acid in order to minimize cross-linking reaction and thereby maximize carboxyl groups content. The characterization of the resulting products confirmed that carboxyl groups were successfully grafted onto surface of bamboo fibers. Moreover, the carboxylated bamboo fibers could be applied as bio-adsorbent for the removal of lead(II) ions from aqueous solution. Results showed that the adsorption capacity of Pd²⁺ could reach 127.1 mg/g for carboxylated bamboo fibers with 4.13 mmol/g carboxyl group content prepared under the ultrasonic pretreatment for 20 min at the CA/bamboo fibers weight ratio of 4.0 in the catalyst amount of 30 wt% at 120 °C for 90 min and the carboxylated bamboo fibers exhibited highly efficient regeneration with no significant loss of adsorption capacity of lead ion after five repeated adsorption/desorption cycles.