Adsorption behaviour and mechanism of Bi(III) ions on rutile-water interface in the presence of nonyl hydroxamic acid.

Micro-flotation tests on purified rutile from Zaoyang, Hubei province, China showed that, in the presence of 400 mg/l of nonyl hydroxamic acid as collector, the flotation recovery of rutile at pH 4.5 in the presence of Bi(III) ions as activator (added as bismuth nitrate) was 91%, compared to a 62% recovery in the absence of activator. Adsorption experiments indicated that, in the pH range 2.3-9.7, the amount of nonyl hydroxamic acid adsorbed on the rutile surface was significantly increased after the addition of Bi(III) ions. Zeta potentials on the rutile surface were found to shift to more positive values after the addition of Bi(III) ions, which was conducive to the adsorption of nonyl hydroxamic acid anions. X-ray photoelectron spectra demonstrated that the adsorption of Bi(III) ions on to the rutile surface had no effect on the chemical environment of the titanium atom. A two-step sequential adsorption mechanism is proposed involving Bi(III) ions occupying the vacancies after Ca2+, Mg2+ and Fe2+ impurity ions on the rutile surface had dissolved in the acidic solution, and Bi(III) ions covering the surface as hydroxy compounds such as [Bi(OH)]2+ and [Bi(OH)2]+.
Micro-flotation tests on purified rutile from Zaoyang, Hubei province, China showed that, in the presence of 400 mg/l of nonyl hydroxamic acid as collector, the flotation recovery of rutile at pH 4.5 in the presence of Bi(III) ions as activator (added as bismuth nitrate) was 91%, compared to a 62% recovery in the absence of activator. Adsorption experiments indicated that, in the pH range 2.3-9.7, the amount of nonyl hydroxamic acid adsorbed on the rutile surface was significantly increased after the addition of Bi(III) ions. Zeta potentials on the rutile surface were found to shift to more positive values after the addition of Bi(III) ions, which was conducive to the adsorption of nonyl hydroxamic acid anions. X-ray photoelectron spectra demonstrated that the adsorption of Bi(III) ions on to the rutile surface had no effect on the chemical environment of the titanium atom. A two-step sequential adsorption mechanism is proposed involving Bi(III) ions occupying the vacancies after Ca2+, Mg2+ and Fe2+ impurity ions on the rutile surface had dissolved in the acidic solution, and Bi(III) ions covering the surface as hydroxy compounds such as [Bi(OH)]2+ and [Bi(OH)2]+.