An efficient separation for metal-ions from wastewater by ion precipitate flotation: Probing formation and growth evolution of metal-reagent flocs

Hazardous metal pollution became a severe environmental issue in China. An efficient precipitationflotation process was developed to achieve fast removal for metal-ions from wastewater. Structure and strength of precipitate particles/flocs significantly influence the flotation removal of metal-ions. Formation and growth-evolution of precipitate flocs in precipitate flotation were studied by stage analysis of precipitate particles-formation, flocs-regulation and flotation separation. The results demonstrate that early formed precipitates MHA(humics-metal complexing particles) have small particle size, high fractal dimension, low strength and recovery factor. The addition of Fe3+ and CTAB(cetyl trimethyl ammonium bromide) reagents make the precipitate particles aggregated to flocs(MHA-Fe, MHA-Fe-CTAB) much more large, loose, coarse, and small-density. The final generated MHA-Fe-CTAB flocs are hard to be broken up, easy to be recovered and efficient to be separated by flotation process. The flotation removal of MHA-FeCTAB flocs is clearly higher than that of MHA or MHA-Fe. The flotation results of MHA-Fe-CTAB are as follows: flotation removal of 98.7 +/- 0.40%-99.9 +/- 0.10%, residual TOC of 0.96 +/- 0.38-1.35 +/- 0.41 mg/L and turbidity of 0.44 +/- 0.09-0.63 +/- 0.16 NTU. Introducing Fe3+ and CTAB reagents into flotation solution contributes to the growth-evolution of precipitate flocs, which could intensify the metal-ions removal via precipitate flotation process and result in more ideal purification indexes for metal-containing wastewater. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The addition of Fe3+ and CTAB reagents into flotation solution contributes to the formation of MHA-Fe-CTAB flocs, which are easy to recover and have high flotation removal efficiency.