Leaching Retention of CCA Metals from High- Temperature Reaction with Alkaline Earth and Iron Based Sorbents
Year: 2015
Type: article
Abstract: Chromated copper arsenate (CCA) was the dominant wood preservative used for outdoor wood products to prevent structural decay prior to its phase down starting from 2004. Incineration is one key disposal alternative for CCA-treated wood; however, it results in volatilization of metals at high temperature and accumulation of metals in ash. The objective of this study was to assess alkaline earth and iron based sorbents for their capability to minimize leaching of metals from the incinerator ash. Experiments were carried out by heating CCA metal spikes combined with sorbents to temperatures of 700, 900 and 1100 oC. The residual ash was analyzed for leaching retention using the toxicity characteristic leaching procedure (TCLP) and speciation by X-ray diffraction (XRD). Results show that alkaline earth sorbents (cement, calcium hydroxide and magnesium hydroxide) were the most promising for reducing the leaching of arsenic from the ash below the 5 mg/L TCLP limit and retaining copper at concentrations below detection limits. For chromium, iron and magnesium based sorbents resulted the highest retention with low leachate concentrations (<5 mg/L) at temperatures of 1100 oC. Leaching appeared to be highly pH dependent with As and Cu leaching more at low pH values and Cr leaching more at high pH values. Results also indicate that the formation of compounds like Ca3As2O7, FeCr2O4 and CuCr2O4 during the reaction reduced the volatilization of metals. The results suggest that a combination of sorbents at different stages of high-temperature processes may offer effective control of the leaching of CCA metals.
Language: English
Subfield: Building and Construction
Field: Engineering
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W2993716223