Recovery of volatile aroma components from aqueous waste streams using an activated carbon column

The solid phase adsorption of aroma components depleted from essential oils and drained with the condensed water water during the distillation of aromatic plants onto granular activated carbon (GAC) is reported. A mini-column packed with laboratory-prepared activated carbon, derived from pistachio shells, which were previously treated with H3PO4 and pyrolysed at 500 °C, was used. Three aromatic waste waters (peppermint, lemongrass, and spearmint) discharged from a distillation plant, were chosen and allowed to pass through the column. GC and GC–MS techniques were employed to detect and quantify the selected key aroma components in the waste waters, and in the effluent waste water after passing through the carbon column. The high surface area GAC (≈1300 m2/g) proved highly efficient in retaining most of the selected aroma components of the waste waters up to 90 bed volumes of treatment without reaching exhaustion. The uptake of the aroma components by activated carbon was demonstrated to be dependent on their chemical structure and oxygen-functional groups. Hydrophilic aroma components were retained more selectively than hydrophobic ones, due to the acidic nature of the carbon surface, which had good affinity for water. Recovery of the aroma from the loaded carbon column, with diethyl ether, resulted in general quantitative recovery of the adsorped components and the degree of recovery (70–98%) depended on the chemical structure. Open chain components were partially entrapped within the internal porosity, which inhibited their complete recovery. The reported process of solid-phase separation appears useful for the recovery of water-soluble aroma components without affecting their physical or chemical characteristics and without need to raise the temperature.