Effect of pyrolysis temperature and thermal oxidation on the adsorption properties of carbon cryogels

• Higher pyrolysis temperature can improved adsorption properties of carbon cryogels.
• Low-temperature oxidation can improved adsorption properties of carbon cryogels.
• Presence of graphene in carbon cryogels does not improve the adsorption properties.

The effect of pyrolysis temperature (500 °C and 930 °C) and partial oxidation by oxygen (250 °C–450 °C) of resorcinol–formaldehyde cryogels (RF) and their graphene derivatives (RFGO) on adsorption capacity for Pb(II) and methylene blue were investigated. Increasing temperature of partial oxidation causes increase in adsorption capacity for Pb(II) from 0.09 to 0.20 (RF) and 0.10 to 0.29 mmol g−1 (RFGO) for samples pyrolysed at 500 °C resp. from 0.20 to 0.23 (RF) and 0.16 to 0.27 mmol g−1 (RFGO) for samples pyrolysed at 930 °C. Partial oxidation does not affect adsorption capacity for methylene blue. The adsorption capacity of carbon cryogels for both adsorbates increased with higher pyrolysis temperature about 90% for RF and 60% for RFGO. The presence of graphene in the structure does not improve the adsorption properties of prepared carbon cryogels.