The segmented micro-flow extraction and separation of the adjacent elements of Co from Ni sulphate
solution with Cyanex 272 is developed using a micro-scale coiled flow inverter (CFI). This is compared
with the conventional batch extraction in parallel. Continuous operation of a process involving liquidliquid
extraction and then two-phase separation is achieved instantly. For the latter a micro-scale separator
is used. Compared with batch extraction, the segmented micro-flow extraction process shows
order-of-magnitude faster extraction times, higher extraction ability for Co, lower extraction for Ni,
and then a better selectivity between Co and Ni at industrial-matching concentration. Regular columnar
slugs are observed at low flow rates and found to be a Gaussian function of the flow rates. Matched inand
outlet flows indicates that extraction in micro-flow is dependent on mass transfer by molecular diffusion.
Extraction efficiency is enhanced by the internal circulation flow generated within slugs.
Additionally, the characteristic parameters, overall volumetric mass transfer coefficient kLa and overall
mass transfer coefficient kL, are measured to determine the mass transfer performance. Compared with
batch, much higher kLa of Co (0.26–0.017 s1) and smaller of Ni (0.053–0.013 s1) are investigated in CFI.
Meanwhile, 4.5 times increasement of the kL value of Co to Ni is observed in CFI indicating the asynchronous
extraction between Co and Ni.