Selective recovery of cannabidiol from biomass and inflorescences of Cannabis sativa L. using hydrofluorocarbons and hydrofluoroolefins as extracting solvents

In recent years, the potential for producing cannabinoid-rich extracts from cannabis waste using innovative extraction methods has gained the interest of the scientific community and industrial realities. This study proposes a high-efficiency extraction system to recover cannabidiol from cannabis inflorescences and biomass using the refrigerants HFC-R134a and HFO-R1234ze as extracting solvents. During inflorescence extraction, both refrigerants yielded extraction results (17.6 % and 18.5 % after 325 min and 170 min, with R134a and R1234ze, respectively) comparable to those achieved by more established extraction technologies that use organic solvents or supercritical fluids. R1234ze provided a significant kinetic improvement, also ensuring milder operating temperatures and pressures (31°C, 6 bar) and a lower environmental impact than the process conducted with R134a (43°C, 11 bar). R134a exhibited greater selectivity for neutral cannabidiol over its corresponding acid form (CBD/CBDA = 3.2) compared to that observed with R1234ze (CBD/CBDA = 1.98); however, the overall cannabinol recovery achieved with the hydrofluoroolefin fluid was slightly higher than that obtained with the hydrofluorocarbon solvent. During the biomass extraction, maximum efficiencies of approximately 13 % and 16.85 % were reached after 195 min and 180 min, using R134a and R1234ze, respectively. Additionally, a total cannabidiol yield of 4 % on a dry basis was obtained using both refrigerants and the same operating conditions adopted for inflorescences. Moreover, in both cases, higher concentrations of neutral cannabidiol were primarily recorded in the extracts collected during the initial stages of the process, suggesting a selective affinity of these solvents for the apolar components. These results were further enhanced when R1234ze was utilized as an extracting solvent and appropriate decarboxylation treatment was applied to the biomass, thereby achieving a total yield of 13.4 % after 120 min and a more concentrated cannabidiol amount in the resulting extracts.