Boric acid is one of the most effective types of wood preservative in that it imparts flame retardancy and has antimicrobial properties. Douglas-fir, Yellow pine, Sapele, and Oak are some of the most common wood types used for lumber purposes. The adsorption of boric acid on the four selected wood types was tested. Standard methods were used to determine the moisture content (MC%), organic matter (OM%), ash content (AC %), density, and pH of each wood type, and the penetration of boric acid was detected using a visual inspection method. The analysis of the wood properties showed that Yellow pine
(a softwood) had the highest MC% (11.88 ± 0.36) and OMC % (97.5 ± 1.3). However, the results of the ash residue and wood density analyses indicated that Oak wood has the highest AC% (4.02 ± 0.01) and wood density (0.68 ± 0.06 g/cm³). From a gravimetric method, Yellow pine wood was shown to have the highest retention quantity of boric acid. Boric acid penetration results have been obtained for Yellow pine, Douglas-fir, and Sapele wood by a colorimetric method. The comparison of the1mal decomposition between untreated and treated samples in four wood type indicated that the highest boric acid concentration (0.4 M) has significant effect on the them1al behaviour of yellow pine and Douglas-Fir (softwood) compared to Sapele and Oak species as hardwood.
The residues of the fire accelerants (petrol, kerosene, and diesel) were analysed in fired and unfired debris for each of the four wood types, with wood types treated with different concentrations of boric acid (0.1, 0.2, 0.3, and 0.4 M). Solvent extraction and gas chromatography-mass spectrometry (GC/MS) methods were used to identify the residues.
Petrol, kerosene, and diesel components were most easily observed in Yellow pine wood, followed by Douglas-fir, Sapele, and Oak wood, for fired and unfired wood samples, across all levels of boric acid treatment. Diesel was more easily detected, followed by the kerosene and petrol, across all the wood types in both unfired and fired wood samples.
An adsorption experiment on the four wood species was performed using the batch technique at initial boric acid concentrations of 0.1, 0.2, 0.3, and 0.4 Mover a time period of 5 to 250 min. The results showed that Yellow pinewood has the highest ability for boric acid adsorption, followed by Douglas-fir, Sapele, and Oak. The adsorption isotherm studies indicated that the equilibrium data for adsorbed boric acid by all block wood samples fit better with the Freundlich isotherm compared with the Langmuir Equation. The results of the kinetic studies showed that the pseudo second-order kinetics model was more suitable than the first kinetics model for explaining the boron adsorption data.
To conclude, this thesis was shown that fire accelerants (when present) can be detected in wood samples by a GC/MS method and that wood pretreated with boric acid helps to enhance forensic detection of fire accelerants in criminal fires (arson).