Performance of alcoholic solvents in the continuous countercurrent spent coffee grounds oil extraction

Ethanol and isopropanol, absolute (ET0, IPA0) and hydrated with 6 and 12 water mass% (ET6, IPA12), were evaluated as solvents in the oil extraction from spent coffee grounds (SCGO). Alcohols' performance evaluation was based on the SCGO partitioning between extract and raffinate phases and the extractor design. An SCGO concentration limit in systems containing ET indicates extract phase saturation. In this case, a Langmuir-type equation provided a satisfactory SCGO partitioning data mathematical description, while the IPA data presented a linear behavior. The increase in temperature from 60 to 80 degrees C did not affect SCGO partitioning when IPA0 was used as a solvent. ET6 required higher solvent proportions concerning SCG, leading to extractors with a higher number of theoretical stages. The minimum flow rates of ET6 were 1.9 times higher than those required by ET0 and IPA12 and up to 3.2 times higher than the IPA0 flow rate at 60 degrees C. At 80 degrees C, the SCGO extraction performance with ET0 and IPA0 was similar. A solvent-to-feed ratio of at least five must be used when an extractor with five theoretical stages operating at 80 degrees C is considered. In this case, extracts with about 5 mass% of SCGO are obtained.(c) 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

This study evaluated the effectiveness of ethanol and isopropanol as solvents for oil extraction from spent coffee grounds. The partitioning of ethanol and SCGO can be described by the Langmuir equation, while the partitioning of isopropanol and SCGO showed a linear relationship. The temperature did not affect the partitioning when isopropanol was used as the solvent. Ethanol hydrate required more solvent for SCGO extraction, while isopropanol hydrate required less solvent. A solvent-to-feed ratio of at least five is needed when considering an extractor with five theoretical stages operating at 80 degrees Celsius.