A lead-free flotation process for enriching wolframite with H 2 O 2 and dithiocarbamate-hydroxamic acid

The green and eco-friendly flotation process to enrich wolframite under lead-free pulp is an attractive issue, which is promising to be broken through an innovative oxidation flotation approach with H 2 O 2 and N -[(3-hydroxyamino)-propoxy]- N -hexyl dithiocarbamate (HAHD). The flotation results indicated that in comparison to the traditional technology with lead ion pre-activation and benzohydroxamic acid (BHA) collection, the new approach with H 2 O 2 oxidation and HAHD flotation dramatically promoted the floatability of wolframite. In situ AFM showed that H 2 O 2 eroded wolframite surface and effectively enhanced the adsorption of HAHD. XPS proved that H 2 O 2 treatment increased the proportion of Fe(Ⅲ) on/in wolframite interface. Interestingly, the dithiocarbamate group (-C(=S)S − ) of HAHD was confirmed to be oxidized to the thiuram structure of –C(=S)–S–S-(S=)C-, i.e., HAHD was oxidized to (HAHD) 2 on wolframite surface. Thus, the two hydroxamate groups of (HAHD) 2 combined with two Fe(Ⅲ) sites, leaving the thiuram structure and two hexyl groups outward for attaching air bubbles. The “H” configuration of (HAHD) 2 adsorption model intensified the hydrophobicity of wolframite, which returned the high flotation recovery. Therefore, the lead-free flotation of wolframite was achieved.