The physicochemical properties of char and activated
carbon produced
from the co-pyrolysis of corn stover (CS) and plastics, polystyrene
(PS) and polyethylene terephthalate (PET), were studied. Non-isothermal
gas analysis of the volatiles was conducted using an online mass spectrometer
to correlate the thermal degradation of gaseous byproducts to the
formation of pores in the char materials. The findings determined
that the addition of PS or PET promotes the formation of the solid
char product with either higher than average pore sizes or surface
areas compared to control samples. The addition of PET to corn stover
increases the surface area of the char formed. The char formed from
a CS:PET mass ratio of 1:1 produced char with a surface area of 423.8
± 24.8 m2/g at 500 °C and a duration of 2 h.
The surface area of the chars formed from CS and PET decreased as
the amount of PET decreased, showing a tendency for PET to increase
the surface area of the char materials synergistically. The addition
of PS to corn stover promoted the formation of chars with, on average,
larger pore sizes than the control char samples. The chars were chemically
activated with potassium hydroxide, and the activated carbon that
formed had lower surface areas but comparable surface functional groups
to the control samples. Vanillin adsorption testing showed that activated
carbon from corn stover performed the best at removing 95% of the
vanillin after 2 h. In contrast, the activated carbon from the chars
produced from the co-pyrolysis of corn stover and polystyrene or corn
stover and polyethylene terephthalate removed 45% and 46% of vanillin
after 2 h, respectively. The findings suggest that plastics have a
synergistic relationship in producing char precursors with improved
porosity but antagonistically affect the activated carbon adsorbent
properties.