Recovery of trace Cu2+ using a process of nano-adsorption coupled with flotation: SNP as an adsorbing carrier

The effective recovery of trace heavy metals from their wastewaters is an important but challenging work. Here, a promising process of nano-adsorption coupled with flotation had been validated for the recovery of trace Cu 2+ from its aqueous solution. Firstly, silica nanoparticles (SNPs) acted as an adsorbing carrier to adsorb Cu 2+ (15   mg/L). Subsequently, cetyl trimethyl ammonium bromide (CTAB) was utilized as a collector to capture SNPs. This process made it possible to combine the advantages of both nano-adsorption and flotation. Finally, the recovery efficiencies of Cu 2+ and SNP ( R SNP and R Cu ) and the volume ratio ( φ ) reached 97.1   ±   4.9%, 94.5   ±   4.7% and 23.8   ±   1.2, respectively under the suitable conditions of pH 6.0, SNP concentration 90   mg/L, CTAB concentration 35   mg/L, the adding time of CTAB 5   min and flotation column height 750   mm. By using this process, a suitable foam stability could be achieved because SNPs, apart from being an adsorbing carrier, also served as a foam stabilizer to significantly enhance the foaming stability. Furthermore, Cu 2+ was easily isolated from the recovered SNPs. Overall, this present work was highly effective for the recovery of trace Cu 2+ from its aqueous solution.