A novel surfactant N-(6-(hydroxyamino)-6-oxohexyl)octanamide: Synthesis and flotation mechanisms to wolframite

In this paper, a novel surfactant N-(6-(hydroxyamino)-6-oxohexyl)octanamide (NHOO) was prepared and its flotation performances and adsorption mechanism for wolframite were first investigated by FTIR spectra, flotation tests, zeta potential and adsorption quantity measurements. The flotation results showed that NHOO was a stronger collector than the conventional hydroxamic acid collectors such as benzoyl hydroxamic acid (BHA) and octyl hydroxamic acid (OHA). The adsorption data demonstrated that the adsorption affinity of NHOO to wolframite was far stronger than that of BHA or OHA, and the preferable pH ranges for NHOO adsorption on wolframite surfaces were below 6.69 or above 9.35. The results of FTIR spectra and zeta potential illustrated that NHOO might adsorb on wolframite mainly through hydrogen bonding and electrostatic attraction by its amide-C(=O)H2N+-group at pH < 6.69 or coordination bonding by its hydroxamic-C(=O)NHO- group at pH > 9.35. In the pH range between 6.69 and 9.35, NHOO might exist in zwitterion species which was formed through intramolecular electrostatic attraction between its positive amide and negative hydroxamic groups, resulting in mildly weakening interaction force and collecting power to wolframite. NHOO's unique properties, such as double reactive centers to mineral surfaces, double hydrophobic groups, and self-adapting adsorption manner and hydrophobic geometry to pulp pH values, made it a superior collector for wolframite flotation. (C) 2015 Elsevier B.V. All rights reserved.