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The present paper describes a novel extractant for chromated copper arsenate (CCA)-treated western hemlock ( Tsuga heterophylla). Because the disposal of CCA-treated waste wood is becoming a serious problem in many countries, it is necessary to develop proper remediation technique. Extraction of CCA-treated wood with bioxalate (BO) solvent was evaluated at various solvent pH levels, BO concentrations, extraction temperatures, and liquid-to-solid ratios, as well as with different alkaline metal hydroxides as pH-adjusting reagents. It was clarified that approximately 90% of the chromium, copper or arsenic could be extracted effectively under particular pH conditions (2.2–3.2). Extraction efficiency was also improved by increasing solvent concentration from 0.0125 M to 0.125 M. In addition, increasing BO solution temperature from 25 to 75°C promoted the extraction of chromium and arsenic; however, that of copper was higher than these metals, irrespective of temperature. The optimum conditions for extraction of chromium, copper, and arsenic from treated wood using BO solution were determined to be as follows: pH of 2.2–3.2, solvent concentration of 0.065–0.125 M, solvent temperature of 75°C, and solvent to CCA-treated wood mixture ratio of 20:1 (mL:g). Under these conditions, the extraction efficiencies for chromium, copper, and arsenic were maximized at 89.4, 88.2, and 94.1%, respectively, thus demonstrating the applicability of BO chelation for the remediation of metal contaminated solid waste. [ABSTRACT FROM AUTHOR]

The objective of this research was to evaluate the potential of electrokinetic metal extraction for removing Cu, Cr, and As from CCA-treated wood. Wood chips produced from new, unweathered, CCA-treated lumber were tested in a bench-scale electrokinetic system with two separate electrode compartments and a treatment compartment. Also investigated was the selection of metal extracting reagents for enhancing electrokinetic extraction efficiency. Extraction reagents tested in this study included oxalic acid, citric acid, EDTA, and ascorbic acid. Oxalic acid appeared to be most effective for extracting chromium and arsenic, while EDTA is the most effective reagent for copper extraction. Further testing using acid mixtures showed that EDTA mixed with oxalic acid achieved excellent extraction efficiencies for copper and arsenic. An electrokinetic extraction test, enhanced with the use of EDTA/oxalic acid mixture, removed 74% of Cr, 97% of Cu, and 88% of As from CCA-treated wood chips. [ABSTRACT FROM AUTHOR]