Environmental Engineering Reference
In-Depth Information
FIGURE 2.1
Scanning electron micrograph of the surface of carbon produced by carbonization of a resorcinol/formaldehyde
(R/F: 0.5) resin. The polymerization is catalyzed by CO
3
Na
2
(catalyst/R: 0.005) in water (water/R: 10) using a
stabilizer ([CTAB] = 0.077 M). The resin is carbonized at 800°C in an Ar atmosphere.
The resin could be dried in air and then carbonized to produce porous carbon (
S
sp
=
670 m
2
/g) (Figure 2.1). The surface does not show the large pores expected by a cylindrical
micelle mechanism but individual carbon nanoparticles with interstitial nanopores.
2.2.1.2 Use of Cationic Polyelectrolyte (PDAMAC) as Nanoparticle Stabilizer
The mechanism described in Scheme 2.2 implies nanoparticle stabilization through
adsorption of the cationic micelles. We thought that a cationic polymer could achieve the
same effect. Tests with poly(diallyldimethylammonium chloride) (PDAMAC) reveal that
large porosities could be achieved by using PDAMAC as a stabilizer (Scheme 2.3) [96].
Additionally, the pore size could be controlled by the ratio of monomer to stabilizers [97].
A fracture surface of the carbon shows the pores and the nanoparticle aggregate nature of
the carbon (Figure 2.2).
2.2.1.3 Use of Fibers to Produce Hierarchical Porous Carbon
Besides molecules, larger structures can also be used to produce or maintain porosity
in resins. RF monomer solution could be adsorbed onto cellulosic iber cloths and cured
into a resin. The presence of the iber not only creates macropores (several micrometers
Drying
Pyrolysis
Cationic polyelectrolyte
(PDAMAC)
Nanoporous RF resin
Nanoporous carbon
(nPC-PDAMAC)
SCHEME 2.3
Formation of a nanoporous carbon by stabilization of the RF resin using a cationic polyelectrolyte (PDAMAC).
