A hybrid flotation—microfiltration process for metal ions recovery

In the present study, the removal of two metal ions (copper or chromates) was investigated by employing a hybrid flotation-microfiltration process. Air bubbling, used to limit membranes fouling, could be meanwhile used (under appropriate conditions) as the transport means of flotation. Two flotation techniques were applied; precipitate and adsorbing colloid flotation. In the latter the bonding agent (ferric hydroxide) was in situ produced. The main parameters studied were surfactant, frother and ferric ion concentration. Under the studied conditions, the higher the surfactant or frother concentration the lower the transmembrane pressure was observed while backflush found to have a small effect on hybrid cell operation. Promising results were obtained: the concentration in the outlet was 0.5 mg L−1 for copper and 0.1 mg L−1 for chromium, from initially 50 mg L−1. Attention was also paid to the economics of this integrated process.