Adsorption of heavy metal ions onto chemically oxidized Ceiba pentandra (L.) Gaertn. (Kapok) fibers

The physico-chemical properties of kapok fibers were altered via the combination processes of chlorite-periodate oxidation, in order to assess their efficacy as a heavy metal adsorbent. The chemically-oxidized kapok fibers were found to harbor a certain amount of polysaccharides, together with lowered lignin content. This alteration in lignin characteristics was clearly confirmed via FTIR and NBO yield. Moreover, chemically oxidized kapok fibers retained their hollow tube shape, although some changes were noted. The chemically oxidized kapok fibers evidenced elevated ability to adsorb heavy metal ions with the best fit for the Langmuir adsorption isotherm model. Three cycles of adsorption-desorption were conducted with in-between regeneration steps. Our experimental results indicated that chemically oxidized kapok fibers possessed excellent adsorption characteristics, and the modified kapok fibers could be completely regenerated with almost equimolar diluted sodium hydroxide. Pb, Cu, Cd and Zn ions evidenced adsorption rates of 93.55%, 91.83%, 89.75%, and 92.85% on the chemically oxidized kapok fibers. The regeneration efficiency showed 73.58% of Pb, 71.55% of Cu, 66.87% of Cd, and 75.00% of Zn for 3rd cycle with 0.0125N NaOH.