Optimization of a chemical leaching process for decontamination of CCA-treated wood

摘要

Increasing volumes of discarded Chromated Copper Arsenate (CCA)-treated wood require the development of new treatment and recycling options to avoid the accumulation of wood wastes in landfill sites, resulting in dispersion of contaminants in the environment. The aim of this study is to design an economic chemical leaching process for the extraction of arsenic, chromium and copper from CCA-treated wood. Choice of chemical reagent, reagent concentration, solid-to-liquid ratio, temperature, reaction time and wood particle size are parameters which have been optimized. Sulphuric acid was found to be the cheapest and most effective reagent. Optimum operation conditions are 75 ℃ with 0.2N H_2SO_4 and 150g wood L~(-1). Under these conditions, three leaching steps lasting 2 h each allowed for 99% extraction of arsenic and copper, and 91 % extraction of chromium. Furthermore, arsenic concentration in TCLP leachate is reduced by 86% so the environmental hazard is reduced. Decontamination process cost is estimated to 115 US$ per ton of treated wood. These results demonstrate the feasibility of chemical remediation and that sulphuric acid leaching is a promising option for CCA-treated wood waste management.