A CO2 extraction process for cannabis sativa that uses liquid CO2 in combination with co-solvent admixtures to purify cannabis botanicals in high yield and purity. The extraction process allows for multiple extractions, or washes, to be performed with the same solvent CO2, which may be seamlessly recycled and purified between subsequent extraction cycles. A variety of in-line filtration vessels, pumps, vacuums, and controllable valves are used to yield a pure product while allowing a high level of user control over the process.