TGA and DTA curves for both precursors show four different
stages of weight loss For both precursors, the
first stage appears by 40–163 C, with a weight loss about of 12% of the initial
weight. This stage is associated with the loss of water physisorbed
on the precursors. The second stage for the aguaje stones extends
by 163–307 C with a weight loss of about 47%, due mainly to
hemicelluloses degradation (Fig. 1 – left). The olive stones (Fig. 1 –
right) showed consecutive weight losses by 155–257 C and
257–333 C of about 11 and 22%, respectively, attributed to
hemicelluloses and lignin degradation. In DTA curves for olive
stones, the inflexion point at 257 C shows a sharp exothermic peak
due to volatile evolution (CO2, CH4 and some hydrocarbon) from
biopolymer degradation of hemicelluloses and lignin. These values
are significantly higher compared to aguaje stones, which indicates
that there is a high content of these biopolymers in the o
lives stones.