Controlled depolymerisation, as assessed by analytical ultracentrifugation, of low molecular weight chitosan for potential use in archaeological conservation

The heterogeneity and molecular weight of a chitosan of low molecular weight (molar mass) and low degree of acetylation (0.1), for potential use as a consolidant for decayed archaeological wood, has been examined by sedimentation velocity and sedimentation equilibriumin the analytical ultracentrifuge before and after depolymerisation. Sedimentation velocity before polymerisation revealed a uniform distribution of sedimentation coefficient with little concentration dependence. SEDFIT-MSTAR analysis revealed a weight average molecular weight Mw of (14.2 + 1.2) kDa, and polydispersity index of ~ 1.2. Further analysis using MULTISIG revealed a distribution of material between 2-20 kDa and consistent with the weight average Mw. Controlled depolymerisation using hydrogen peroxide and UV in an acetic acid medium reduced this to (4.9 + 0.7) kDa, with a similar polydispersity. The depolymerised material appears to be within the range that has been predicted to fully penetrate into archaeological wood. The consequences for this and the use of the analytical ultracentrifuge in wood conservation strategies is considered

Effect of bitumen addition on the long-term permeability of sabkha soil

This study investigates the effect of bitumen addition on the long-term permeability of bitumen mixed sabkha soil. Results will be used to evaluate the effectiveness of using the bitumen mixed sabkha soil as hydraulic barriers to leachate percolation. Eight percent bitumen (by dry weight of sabkha) was selected as a mixing percentage based on density results obtained from modified Proctor tests carried out on sabkha soil samples mixed with different bitumen contents. Long-term permeability studies using distilled water were carried out on undisturbed, natural compacted and 8% bitumen mixed sabkha soil samples. The results displayed significant reduction in the initial and long term permeability values of the 8% bitumen mixed sabkha, as compared to the natural compacted sabkha soil. The reduced permeability values of the 8% bitumen sabkha soil are still higher than the recommended value for soil liners. The results also clearly show that sabkha soil compaction, which is the general practice for liners preparation in Kuwait, is not an effective process

Effect of bitumen addition on the long-term permeability of sabkha soil

This study investigates the effect of bitumen addition on the long-term permeability of bitumen mixed sabkha soil. Results will be used to evaluate the effectiveness of using the bitumen mixed sabkha soil as hydraulic barriers to leachate percolation. Eight percent bitumen (by dry weight of sabkha) was selected as a mixing percentage based on density results obtained from modified Proctor tests carried out on sabkha soil samples mixed with different bitumen contents. Long-term permeability studies using distilled water were carried out on undisturbed, natural compacted and 8% bitumen mixed sabkha soil samples. The results displayed significant reduction in the initial and long term permeability values of the 8% bitumen mixed sabkha, as compared to the natural compacted sabkha soil. The reduced permeability values of the 8% bitumen sabkha soil are still higher than the recommended value for soil liners. The results also clearly show that sabkha soil compaction, which is the general practice for liners preparation in Kuwait, is not an effective process