Effect of composition and process variables on colloidal stability of Pinus radiata wood extractives

The effects of the interaction between process variables of pH, temperature, soluble calcium and dissolved organics (DOM) on the colloidal stability of Pinus radiata wood extractives at two different compositions representing the maximum and minimum in ester to acid ratio (EAR) were investigated. The EAR of the extracts was found to significantly affect the wood extract colloidal properties. Low EAR (EAR=0.31) extracts were found to be more unstable and more susceptible to deposition and destabilisation by soluble Ca than higher EAR (EAR=0.67) extracts. Complex interactions between the various process variables were found. In particular, the DOM level was found to cause both stabilisation and destabilisation depending on the DOM concentration and the pH. This was more apparent in the higher EAR extract. Predictive modelling of the effect of process variables on pitch deposition and colloidal stability was undertaken. Modelling of the individual wood extracts was found to be more reliable that the total extract and demonstrated that competing interactions between the process variables and their effect on the components was occurring