The thermogravimetric (TG) and first derivative thermogravimetric
(DTG) curves for pyrolysis of pretreated water hyacinth
samples (Sample 1, 5A, 6A, and 11B) are presented in Fig. 4a–d,
respectively. A slow heating rate (10 C/min) had provided clear
separation between stages in the thermal analysis as suggested
by Sricharoenchaikul and Atong (2009). Four major stages in thermal
degradation of water hyacinth samples were marked accordingly
in Fig. 4a, (1) moisture evaporation, (2) degradation of
hemicellulose and cellulose, (3) degradation of lignin and (4) formation
of pyrolytic char in. The first stage starts from 25 until
200 C, with two peaks detected at 50 and 165 C. Weight loss at
this stage is relevant to evaporation of volatile matters and moisture
residual from samples as the system heats up (Girisuta
et al., 2008).