Experimental optimisation of waste-derived glycerol purification via electrodialysis under industrially relevant conditions

The purification of synthetic and pre-treated impure glycerol from 2^nd generation biodiesel refineries is addressed to reduce the ash content below 1 % wt. Electrodialysis purification has been selected for its ability to selectively remove salts from the glycerol. First, synthetic glycerol-rich samples are tested to optimise cell voltage, membrane type and time on stream to achieve the target of 1 % wt. ash. After that, industrial pre-treated glycerol is used as a feed stream and compared. The comprehensive testing campaign demonstrated a recovery greater than 60 % with a glycerol purity greater than 82.2 % (wet and 90.4 % wt. dry basis) and ash content below 1 % wt. for 130–280 min and specific energy consumption ranging from 4.5 to 8.9 MWh∙m⁻³ depending on the sample and conditions. to further decreases the ash content (below 0.5 % wt. corresponding to conductivity <2 mS∙cm⁻¹) the energy requirement increases by almost three times confirming that while electrodialysis is a suitable technology for deeper waste stream purification, but energy supply and costs may hamper the implementation at scale.