Hydroxamic Acid Collector Research Articles

Activation Mechanism of Lead Ions in Perovskite Flotation with Octyl Hydroxamic Acid Collector

The activation mechanism of lead ions (Pb2+) in perovskite flotation with an octyl hydroxamic acid collector was systematically investigated using microflotation experiments, zeta-potential measurements, adsorption tests, Fourier transform infrared (FT-IR) analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The results of microflotation experiments and adsorption tests indicate that the presence of Pb2+ can promote the adsorption of octyl hydroxamic acid (OHA) on the perovskite surface and enhance the flotability of perovskite under weakly acidic conditions. The maximum recovery of 79.62% was obtained at pH 6.5 in the presence of Pb2+, and the maximum recovery of 57.93% was obtained at pH 5.7 without Pb2+. At pHs below 7, lead species are mainly present as Pb2+ and PbOH+ in the solution; besides this, the relative content of titanium increases on the perovskite surface. The adsorption of Pb2+ and PbOH+ on the perovskite surface makes the zeta-potential of perovskite shift positively, and increases the number of activated sites on the perovskite surface. FT-IR and XPS analyses confirm that OHA chemisorbs on the surface of Pb2+-activated perovskite and forms hydrophobic Pb-OHA complexes, which improve the flotability of perovskite.

Surface interactions and flotation behavior of calcite, dolomite and ankerite with alkyl hydroxamic acid bearing collector and sodium silicate

The surface interactions and adsorption mechanism of alkyl hydroxamic acid bearing collectors and sodium silicate depressant on common carbonatite gangue minerals, including calcite, dolomite and ankerite in flotation were investigated. For this purpose, firstly the flotation behaviors of these minerals in the presence of the collector and depressant were investigated via micro-flotation tests at pH 7–9.5. Meanwhile, the interaction nature of this collector and depressant with minerals was disclosed through FTIR and zeta potential measurements over the studied pH range. It was found that either floatability of minerals in the presence of collector or the affinity of minerals towards collector and depressant adsorption are in the order of ankerite >> calcite dolomite. The nature of collector-minerals’ interactions and also the collector’s adsorption mechanism were further studied via density functional theory (DFT) simulations to identify the likeliest collector configurations and adsorption pathways of collector and depressant on the mineral surfaces. It was concluded that ankerite has higher affinity towards alkyl hydroxamic acid collector and also sodium silicate as compared with calcite and dolomite. It was revealed that collector is going to interact with metal atoms on the minerals surfaces via covalent bonding through which bridged and monodentate binding configuration are more favorable. It was found that Fe atoms on the mineral surfaces are more involved in bond formation as compared with Ca and Mg. The DFT simulations also indicated that sodium silicate has more affinity towards ankerite which was confirmed via experimental observations. Besides, the surface interaction pathway of both SiO(OH)3− and Si(OH)4 as dominated silicate monomers in aqueous phase on the mineral surfaces were demonstrated. It was found SiO(OH)3− species enable either covalent or hydrogen bonding on the mineral surfaces, while Si(OH)4 species are likely to interact with minerals only through hydrogen bonding. Therefore, SiO(OH)3− species are corroborated to prompt more important depressant effects on froth flotation of carbonatite gangue minerals.

An evaluation of hydroxamate collectors for malachite flotation

Abstract Copper oxide minerals, such as malachite, do not often respond well to traditional copper sulphide collectors, and require alternative flotation schemes. Hydroxamic acid collectors have been suggested as a means to directly float malachite; however, there is limited information on the effect of reagent structure on the performance of these collectors. This paper investigated the effect of five alkyl hydroxamates and two aromatic hydroxamates on the flotation of a synthetic ore composed of pure, fully liberated, malachite and quartz. Zeta potential measurements were used to aid in understanding reagent adsorption onto the surface of the two minerals. The collectors were then evaluated using bench scale flotation results. While zeta potential measurements suggested that all the collectors investigated selectively adsorb onto the surface of malachite, only benzohydroxamic acid and C8 alkyl hydroxamates were effective collectors in the flotation of malachite. Benzohydroxamic acid was the most selective; however, significantly lower dosages of C8 alkyl hydroxamates were required to obtain similar malachite recoveries, with minimal increases in quartz recovery. Benzo- and octylhydroxamic acid were further examined for the flotation of fine (−38 μm) particles. For fine particle flotation experiments the effect of temperature was also investigated as a means to improve the flotation performance.

Synthesis of 3-hydroxy-2-naphthyl hydroxamic acid collector: flotation performance and adsorption mechanism on bastnaesite

Synthesis of 3-hydroxy-2-naphthyl hydroxamic acid collector: flotation performance and adsorption mechanism on bastnaesite

Hydroxamic acid interactions with solvated cerium hydroxides in the flotation of monazite and bastnäsite—Experiments and DFT study

Density functional theory (DFT) simulations and experiments were performed to clarify the interaction mechanisms between hydroxamic acid collectors and cerium hydroxides during the flotation of bastnäsite and monazite minerals. These minerals showed considerable floatability at moderately alkaline pH which was related to the adsorption of hydroxamic acids on their surfaces as confirmed by vibrational spectroscopic and zeta potential measurements. DFT simulations showed that at moderately alkaline pH, the interactions between solvated Ce(OH)2+ and Ce(OH)2+ and heptyl-hydroxamic acid (HHA) anions resulted in the formation of, respectively, [Ce(OH)(HHA)x(H2O)y]2−x (x[y=]=1[6],2[3],3[1]) and [Ce(OH)2(HHA)x(H2O)y]1−x (x[y=]=1[5],2[1],3[0]) complexes. The collector anions were found to interact directly through formation of two covalent bonds between their two polar-head oxygen atoms and cerium in the hydroxide complexes. However, formation of such new bonds resulted in breakage of a few covalent/electrostatic bonds between cerium and water molecules initially present in the first hydration shell of the rare-earth metal cation. Building up in the electric double layer of the semi-soluble minerals, these complexes, and by extension, those from other rare-earth elements belonging to monazite and bastnäsite, are speculated to play a role in the interactions between rare-earth minerals and hydroxamic acid collectors.

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.

Solution chemistry and utilization of alkyl hydroxamic acid in flotation of fine cassiterite

Solution chemistry and ?otation of cassiterite in the presence of alkyl hydroxamic acid collector were investigated. Results show that the alkyl hydroxamic acid is able to float fine cassiterite very well at relatively alkaline conditions, and the pH range of better flotability broadens with the increase of chain length of the collector. Moreover, the metal cations influence the flotation mostly depending on the pH of the medium and to some extent on the concentration of metal cations. Theoretical calculation on the group electronegativity indicates that the alkyl chain length of about seven is of great superiority in the synthetization of hydroxamic acid collector for cassiterite flotation. A co-adsorption between molecules and ions onto cassiterite surface is considered according to the lg c—pH diagram analysis. In terms of zeta potential and infrared spectra, the main interaction involves electric charge interaction, hydrogen bonding interaction and complexation, with the proposed formation of an O, O-five membered rings chelate compound .