Removal of sodium oleate from synthetic manganese leaching solution by coagulation-dissolved air flotation

The coagulation-dissolved air flotation for removal of sodium oleate (NaOL) from synthetic manganese leaching solution was focused in this study. It indicates that partially hydrolyzed polyacrylamide (HPAM), NaOL dosage and pH have a multiple effect on the removal efficiency of NaOL. The results represents a significant removal efficiency of 97.6% NaOL was achieved under the optimal conditions of coagulation-dissolved air flotation by dosage of 20 mg/L HPAM and 30 mg/L NaOL, pH 8.0. Solution pH has a significant effect on the distribution of oleate species and Mn2+ species. The addition of HPAM facilitates the formation of OL− micelle and the decrease of critical micelle concentration (CMC). Oleate species primarily exist, containing Mn(OL)2(s), OL− and HOL(aq). HPAM could cause the Zeta potential of NaOL to shift negatively. HPAM could decrease CMC of NaOL and lead to a transition from three dimensional network structure to lamellar structure. NaOL can be removed by coagulation-dissolved air flotation through the adsorption and bridge effect of HPAM chains on the floating bubble surface. [Display omitted] •NaOL is efficiently removed by coagulation-dissolved air flotation.•The addition of HPAM makes CMC of NaOL decrease.•HPAM results in Zeta potential of NaOL shifting negatively.•HPAM has the absorption and bridge effect for the NaOL removal.