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In this study, a hydrometallurgical treatment involving the solvent extraction and recovery of some heavy metals from a sulphuric acid leach solution of galvanic sludge, using di-(2-ethylhexyl)-phosphoric acid (D2EHPA) and bis-(2,4,4-trimethylpentyl)-phosphinic acid (Cyanex 272), both diluted in kerosene, has been investigated. The preliminary tests revealed the necessity to remove other metal species than zinc and nickel, contained in the leach solution, and therefore, processes to cement copper and precipitate chromium were then applied to finally obtain a Zn and Ni pregnant solution prior to solvent extraction. For the experimental conditions studied, Cyanex 272 showed a good recovery of Zn after the stripping stage using H2SO4, but D2EHPA effectively promoted a higher Zn extraction than Cyanex 272 did. The dependence of the solvent extraction method on variables such as pH, contact time and concentration of extractant, as well as the effect of different concentrations of sulphuric acid on stripping, are discussed. The discussion also includes the previous conditions developed to separate the main interfering metallic species from the leach solution in order to improve the extraction and recovery of zinc by solvent extraction. The final objective has been to achieve a solution as pure as possible to recover nickel sulphate.

Pure and copper-modified photocatalytic TiO 2 nanopowders were prepared via a green sol−gel route and heated to 450°C. Copper does not enter the TiO 2 lattice but forms as smaller ∼2 nm Cu-based nanocrystals, decorating the surface of ∼10 nm TiO 2 nanoparticles. The surface of the larger TiO 2 nanoparticles (NPs) is partially covered by much smaller Cu NPs, attached to the surface of the larger NPs but not completely covering them due to the small quantity present (1−10 mol % Cu). This retards the anatase-to-rutile phase transition and titania domain growth through a grain-boundary pinning mechanism. These hybrid nanoparticles show tunable photochromic behavior under both UVA and visible light. Under UVA, Cu 2+ nanoparticles reduce to Cu + , and then to Cu 0. Under visible-light, Cu 2+ reduces to Cu + , although to a lesser extent. The induced photochromism can be tuned by varying the light source or exposure time. One mol % Cu causes a reduction of Cu 2+ , and lowers the d−d absorption band, to 50% after only 12 s, and 95% after 10 min, under UVA-light, and has a reduction of 25% in 1 min, 50% in 4 min, and 80% in 1 h under visible-light. This is the first report of inorganic compounds, in this case Cu-TiO 2 hybrid nanoparticles, to exhibit tunable photochromism under both UVA and visible-light exposure. This rapid and sensitive effect can potentially be used to modify, tune, or monitor the progress of photoactivated behavior in a new generation of smart/active multifunctional materials and photoactive devices or sensors.

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