Preliminary Study On CCA-treated And ACQ-treated Wood Liquefaction In Phenol

In order to find a suitable method for recycle-treatment of the preservative-treated waste for increasing the integrated utilization of this available material, the research focus on the liquefaction of CCA-treated and ACQ-treated wood in phenol and the effects of liquefaction time, temperature, concentration of sulfuric acid and phosphoric acid on the phenolation extents were determined. The removal regularities of Cu, Cr and As in CCA-treated wood and Cu in ACQ-treated wood were investigated. At the mean time, the influences of reaction time, temperature, concentration of sulfuric acid and phosphoric acid on the removal of metals from the treated wood were analyzed. The following results are obtained.1 , Liquefaction time is one of the most important factors of the treated wood. Increasing liquefaction time can accelerate the phenolation of CCA-treated and ACQ-treated wood. The residue contents of liquefied treated wood don't decreased all the time, but has some trends of increasing probably in relate to the contribution of metal precipitates.2, Liquefaction temperature has a smaller effect in the phenolation compared with the time. Raising temperature can accelerate the phenolation to treated wood, and the variation of residue contents is not stable with the elevation of temperature.3, The presence of sulfuric acid has an obvious effect on the liquefaction of ACQ-treated wood. The residue contents of liquefied ACQ-treated wood decrease with the increasing of sulfuric acid and become consistent when concentration of sulfuric acid arrives at a reasonable level. It is not the same as the liquefaction of CCA-treated wood which has a rising trend of residue contents with the change of sulfuric acid.4, The presence of phosphoric acid has great effects both on CCA and ACQ treated wood liquefaction. With the increasing of concentration of phosphoric acid, residue contents of liquefied treated wood decrease at a low addition of acid slightly then increase at a high addition. It arrives at a relatively maximum value when the concentration of phosphoric acid is added to 3%.5, Residue content and metal removing rate should be considered as the parameters to estimate the liquefaction efficiencies of the treated wood.6, After the liquefaction in phenol, most of copper in CCA-treated wood is removed into the residue. With the change of liquefaction time and temperature, the removing rates of copper are very instable and have wide fluctuation ranges between 70%～95%. Concentration of sulfuric acid has little influence on removal of copper, and 80% of copper is removed from CCA-treated wood on an average. Increasing concentration of phosphoric acid has a great effect on removal of copper, all of the copper is removed when it is added to 3%. But the rates may decrease if there are too much sulfuric or phosphoric acids added.7, After the liquefaction in phenol, nearly all of chromium in CCA-treated wood is removed into the residue. Liquefaction time and temperature have little effect on removing rates of chromium. Withthe change of concentration sulfuric, the removing rates of chromium are very instable and have a ranges between 88%～99%. Increasing concentration of phosphoric acid has a great effect on removal of chromium, which can raise the removing rates, and 99.49% of the copper is removed when it is added to 3%. But, the same as removal of copper, the rates may decrease if there are too much sulfuric or phosphoric acids added.8, After the liquefaction of CCA-treated wood in phenol, the removing rates of arsenic are in an average of low levels. Most of the arsenic still exist in the complex liquefied wood in various forms.9, During the liquefaction of ACQ-treated wood in phenol, all of the factors have great effect on removal of copper. The removing rates are instable with the change of the time and temperature, and it's similar with the liquefaction of CCA-tread wood. When the time is 2h or temperature is too high, it is unfavorable to removing copper. Increase sulfuric acid may cause reduction of the removing rates. With the increasing of phosphoric acid, the removing rates of copper decrease slightly at a certain addition of acid then increase at a high addition.