Adsorption Characteristics of Cd (II) and Pb (II) on Wood Charcoal

• Published in: RESOURCES PROCESSING Vol. 48; no. 1; pp. 9 - 18
• Main Authors: KAI, Tokio, YAMAMOTO, Shimpei, ISHIHARA, Shigehisa
• Format: Journal Article
• Language: English
• Published: The Resources Processing Society of Japan 2001
• ISSN: 0912-4764; 1883-9150
• DOI: 10.4144/rpsj1986.48.9

To make effective use of waste wood resources from thinning and other waste-producing processes, the possibility of using wood charcoal produced from sugi (Cryptomeria japonica D. Don) and hinoki (Chamaecyparis obtusa) as a heavy metal adsorbent has been studied. In an acidic solution, the cadmium (II) and lead (II) adsorbent characteristics of sugi and hinoki samples carbonized at the temperature range of 400 to 1100-C was found to increase as the carbonization temperature increased. The adsorption of sugi carbonized at 1100-C showed the greatest capability, exceeding that of commercial activated carbon. The adsorption of cadmium (II) or lead (II) by a sample of sugi carbonized above 800-C reached equilibrium within 30 minutes. The adsorption of cadmium (II) or lead (II) by charcoal in an acidic solution demonstrated no correlation to the specific surface area or surface oxide content of the charcoal. However, adsorption was dependent on the quantity of alkaline components eluted from the charcoal. It is assumed that the increase in the amount of adsorbed cadmium (II) or lead (II) with the higher carbonization temperature is caused by an increase in the alkaline eluted from the charcoal. As for the adsorption mechanism in these systems, we inferred that a high alkaline concentration on the charcoal surface causes hydroxides to form when cadmium (II) or lead (II) in an aqueous solution contacts the charcoal surface, and that the hydroxides are deposited and stabilized on the surfaces and micro pores of the charcoal. After being adsorbed by sugi charcoal carbonized at 1100°C, almost the entire quantity of cadmium (II) and lead (II) was recovered by processing in an aqueous nitric acid solution of pH 1.