Biochar preparation
The pyrolysis of biomass was conducted in a fixed-bed quartz
reactor equipped with a temperature controller. In every run, biomass
sample was charged into an alumina boat which was then
placed in a quartz tube. The furnace was heated to desired temperature
(200–330 C) with a heating rate 15 C/min and kept at final
temperature 20 min under argon gas atmosphere. After cooled
down to room temperature, the biochar in alumina boat was
weighted and kept in a desiccator for the analysis. The biochars
derived from CF and PW were designated as ‘‘CF-xxx’’ and
‘‘PW-xxx’’, where ‘‘xxx’’ shows pyrolysis centigrade temperature.
Fig. 1 shows the images of several typical biochars prepared in
the present study.