The goal of this design was to prevent backflow and fluid mixing between the process lines and the stack. The previous configuration allowed significant mixing, which could dilute the lithium rich fluid leaving the stack.

The redesigned assembly uses check valves oriented in opposite directions to control flow. Three inlet lines carry different fluids into the system, while a separate line connects directly to the stack for fluid entering and exiting after lithium extraction. Because the fluids have different densities, the densest fluid was positioned at the bottom and the least dense at the top to help maintain separation and reduce gravity-driven mixing.

The assembly went through four iterations. The first used soft tubing as a proof of concept, while the second introduced threaded, transparent rigid tubing. The third and fourth iterations tested different assembly orientations, check valve types and flow rates to determine how turbulence affected mixing and how much flow and pressure the valves could withstand. Testing also showed that laying the system flat allowed the fluids to fill the lines more efficiently, minimized trapped air and further reduced mixing.

Each fluid was dyed a different color so mixing could be observed during testing. The results confirmed that the design effectively limited backflow and mixing, with diaphragm check valves producing the best performance. This assembly is intended for potential use in the final industrial lithium extraction plant.