Superior Mesoporosity of Lipid-Free Spent Coffee Ground Residues

As part of the biorefinery concept for spent coffee grounds (SCG), production of activated carbon (AC) was investigated from the degreased coffee grounds (DCG) left behind after oil extraction (primarily for biodiesel). The oils were extracted through conventional solvent extraction with GC/GC-MS confirming the oil was comparable to oils produced industrially. More significantly, analysis showed the DCG AC to have a four-fold increase in mesoporosity compared with the SCG AC with mesopore volumes of 0.6 and 0.15 cm³  g^-1 , respectively. Adsorption trials showed a ten-fold increase in capacity for Au^III from 8.7 to 88.6 mg g^-1 with subsequent experiments confirming that DCG AC displayed standard behavior for mesoporous materials of increasing adsorption capacity with decreasing pH. This raises the potential for valorization of SCG into a functional material for water remediation without the need for templating agents or expansion pretreatments with the added bonus of an additional material being produced simultaneously.