2.3 Analytical methods
The surface morphology was studied by scanning electron microscopy. Char imaging was carried out
using a JEOL JSM-6335F Field Emission Scanning Electron Microscope. During the SEM analysis, char
samples were selected and imaged randomly to minimize bias. Magnifications between 500X and
1,000X were typically used. Additionally, the heating value of the dried bamboo, and the resulting char
were determined using a Parr bomb calorimeter. It is reported as gross heat of combustion at constant
volume.
Atomic absorption analysis was used to determine the nutrient content of the process water. The target
elements in this study were N, P, and K. Exactly 25 mL of each sample were used for analysis. Each
sample was directly heated in crucible until all carbonaceous matter was removed. The ash was then
allowed to cool down, and later transferred to a flask. The ash was treated with 10 mL of concentrated
HNO3 and 30 mL of concentrated HCl. All the reagents used were of analytical grade. The mixture was
digested at 60o
C for at least 2-3 hours or until the mixture appeared to have no residue. Digested samples
were filtered and their volume adjusted to 100 mL by adding solution of 1.0% HNO3 in deionized double
distilled water. High purity of standard stock solutions of 1000 ppm (mg/L) were prepared for different
metals. The atomic absorption determinations were measured with a Perkin-Elmer Corporation AA
analyst 100 instrument and all data were sampled and processed automatically via a personal computer
using AA Win/Lab software. The spectrometer was operated in the absorption mode (absorbance
readings), using standard solutions for calibration. For each element determination, the recommended