Characteristics of a bioxalate chelating extraction process for removal of chromium, copper and arsenic from treated wood. 2009

Tomo Kakitani, and Toshimitsu Hata, and Takeshi Kajimoto, and Hideki Koyanaka, and Yuji Imamura
Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Uji, Kyoto, Japan.

The disposal of wood waste treated with chromated copper arsenate (CCA) is a problem in many countries. We have proposed a novel chelating extraction technique for CCA-treated wood using bioxalate, a solution of oxalic acid containing sufficient sodium hydroxide to adjust the pH to 3.2, which is an effective way to obtain an extraction efficiency of 90% for chromium, copper, and arsenic. The purpose of the present study was to investigate the characteristics of bioxalate extraction of CCA-treated wood. Extractions of CCA-treated western hemlock chips with solutions of bioxalate, oxalic acid, and sodium hydroxide were carried out. The use of bioxalate was confirmed as the most effective extraction technique for chromium, copper and arsenic, with an efficiency of 90%. Extraction with simple oxalic acid was ineffective for copper (less than 40% extraction efficiency), but effective for chromium and arsenic, with 90% efficiency. Sodium hydroxide showed a similar tendency, being ineffective for chromium and copper (less than 20% extraction efficiency), but relatively effective for arsenic (around 70-80% efficiency). We also discovered an interesting phenomenon whereby the addition of sodium hydroxide to a simple oxalic acid solution during the oxalic acid extraction progress resulted in dramatically increased extraction efficiency for copper, chromium and arsenic, up to 90%. Although oxalic acid was ineffective for copper extraction, the addition of sodium hydroxide during the oxalic acid extraction process rendered it effective.

UI MeSH Term Description Entries
D012037 Refuse Disposal The discarding or destroying of garbage, sewage, or other waste matter or its transformation into something useful or innocuous. Waste Disposal, Solid,Disposal, Refuse,Disposal, Solid Waste,Disposals, Refuse,Disposals, Solid Waste,Refuse Disposals,Solid Waste Disposal,Solid Waste Disposals,Waste Disposals, Solid
D002614 Chelating Agents Chemicals that bind to and remove ions from solutions. Many chelating agents function through the formation of COORDINATION COMPLEXES with METALS. Chelating Agent,Chelator,Complexons,Metal Antagonists,Chelators,Metal Chelating Agents,Agent, Chelating,Agents, Chelating,Agents, Metal Chelating,Antagonists, Metal,Chelating Agents, Metal
D001149 Arsenates Inorganic or organic salts and esters of arsenic acid.
D012972 Sodium Hydroxide A highly caustic substance that is used to neutralize acids and make sodium salts. (From Merck Index, 11th ed) Caustic Soda,Hydroxide, Sodium,Soda, Caustic
D014934 Wood A product of hard secondary xylem composed of CELLULOSE, hemicellulose, and LIGNANS, that is under the bark of trees and shrubs. It is used in construction and as a source of CHARCOAL and many other products. Woods
D052918 Environmental Restoration and Remediation Restoration of an environment, ecosystem, or habitat that was physically damaged during land development or by natural disaster, or contaminated by ENVIRONMENTAL POLLUTANTS. This is accomplished by various chemical, biological, and bulk movement methods, in conjunction with ENVIRONMENTAL MONITORING. Environmental Cleanup,Environmental Remediation,Environmental Restoration,Pollution Remediation,Site Remediation,Cleanup, Environmental,Cleanups, Environmental,Environmental Cleanups,Environmental Remediations,Remediation, Environmental,Remediation, Pollution,Remediation, Site,Remediations, Environmental,Remediations, Site,Restoration, Environmental,Site Remediations
D019216 Metals, Heavy Metals with high specific gravity, typically larger than 5. They have complex spectra, form colored salts and double salts, have a low electrode potential, are mainly amphoteric, yield weak bases and weak acids, and are oxidizing or reducing agents (From Grant & Hackh's Chemical Dictionary, 5th ed) Heavy Metal,Heavy Metals,Metal, Heavy
D019815 Oxalic Acid A strong dicarboxylic acid occurring in many plants and vegetables. It is produced in the body by metabolism of glyoxylic acid or ascorbic acid. It is not metabolized but excreted in the urine. It is used as an analytical reagent and general reducing agent. Aluminum Oxalate,Ammonium Oxalate,Chromium (2+) Oxalate,Chromium (3+) Oxalate (3:2),Chromium Oxalate,Diammonium Oxalate,Dilithium Oxalate,Dipotassium Oxalate,Disodium Oxalate,Ferric Oxalate,Iron (2+) Oxalate (1:1),Iron (3+) Oxalate,Iron Oxalate,Magnesium Oxalate,Magnesium Oxalate (1:1),Manganese (2+) Oxalate (1:1),Monoammonium Oxalate,Monohydrogen Monopotassium Oxalate,Monopotassium Oxalate,Monosodium Oxalate,Potassium Chromium Oxalate,Potassium Oxalate,Potassium Oxalate (2:1),Sodium Oxalate,Acid, Oxalic,Oxalate, Aluminum,Oxalate, Chromium,Oxalate, Diammonium,Oxalate, Dilithium,Oxalate, Dipotassium,Oxalate, Disodium,Oxalate, Ferric,Oxalate, Iron,Oxalate, Magnesium,Oxalate, Monoammonium,Oxalate, Monohydrogen Monopotassium,Oxalate, Monopotassium,Oxalate, Monosodium,Oxalate, Potassium,Oxalate, Potassium Chromium,Oxalate, Sodium
D028225 Tsuga A plant genus in the family PINACEAE, order Pinales, class Pinopsida, division Coniferophyta. They are coniferous evergreen trees and should not be confused with hemlock plants (CICUTA and CONIUM). Hemlock Tree,Hemlock Trees,Tree, Hemlock,Trees, Hemlock,Tsugas

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