Particleboard made from remediated CCA-treated wood: Evaluation of panel properties

Abstract

CCA-treated southern yellow pine (SYP) chips were remediated utilizing acid extraction alone, and using acid extraction followed by bioleaching with the metal-tolerant bacterium Bacillus licheniformis CC01. "Cleaned" chips were used to make particleboard (PB) with 10 percent urea-formaldehyde (UF) resin, and the PB samples were evaluated for internal bond (IB), modulus of elasticity (MOE), modulus of rapture (MOR), thickness swell (TS), water absorption, and decay resistance. PB panels prepared from just acid-extracted chips and two-step remediated chips showed an average 22 and 28 percent reduction, respectively, in IB and 41 and 13 percent reduction, respectively, in MOR compared to values for PB prepared with untreated SYP chips. An 8 to 10 percent increase in MOE in the acid-extracted-chip PB and remediated-chip PB compared to the untreated-chip PB suggested densification of the fiber surface had occurred. Water absorption and TS after 24-hour submersion increased in PB prepared from acid-extracted and remediated chips (14% to 15%). Water absorption and TS were less (28% and 39%, respectively) for the acid-extracted-chip PB compared to the untreated-chip PB. Decay resistance was variable, with low weight losses (less than or equal to 5%) for all PB samples exposed to Postia placenta and weight losses ranging from 11 to 25 percent for untreated and remediated PB exposed to Gloeophyllum trabeum. We conclude that reduced MOR and IB seen in remediated PB are the result of residual oxalic acid either embrittling the fiber or interfering with UF resin adhesion. Results of this study indicate that properties of remediated PB are diminished when CCA-treated chips are exposed to oxalic acid even at low acid concentrations for limited amounts of time.