Anna Marabini

New materials from industrial and mining wastes: glass-ceramics and glass- and rock-wool fibre

Abstract The need to find economically and environmentally more viable methods for the management of industrial wastes has opened the way to the research and development of processes which were still in the laboratory only a few years ago. The examples given concern two very common and acutely-felt problems: the inertization and recycling of hydrometallurgical red muds (RM) and of mine tailings. In the case of red mud, one potential process involves the extraction of metals (mainly Zn, but also Cd, Sn, Ph, Fe), and another involves mixing the RM with granite chippings and cullet to produce glass-ceramics materials via melting and crystallization. The paper also discusses a new flowsheet in which mine tailings are utilized to produce either glass-wool or very strong glass-ceramic products, with good resistance to chemical attack.

Drum leaching tests in iron removal from quartz using oxalic and sulphuric acids

Abstract A study has been made of a leaching process to remove iron from quartziferous industrial minerals using oxalic and sulphuric acid in a drum reactor. The experimental work was necessary because of the paucity of literature on the use of oxalic acid in the treatment of industrial minerals containing iron as an impurity. The positive effect of oxalic acid on the iron extraction yield is clearly observed during leaching in a drum reactor. Iron extraction yields of 35–45% are obtained on treating the quartz with 3 kg/t oxalic acid and 2 kg/t sulphuric acid at 90°C for 4–5 h. Under the same conditions but without oxalic acid the iron extraction yield ranges from 3 to 9%, depending on the sulphuric acid content. Chemical and mineralogical analyses were run on the ore to ascertain where the iron compounds occur on the different mineral components. These analyses were carried out on an as-is sample and on three other samples obtained by magnetic separation. The experimental results indicate that 52% of the iron is found in the mica fraction. These results explain why the maximum iron extraction yield is only 35–45%. A flow-sheet of the process is proposed together with a rough material balance in order to estimate oxalic acid, sulphuric acid and water consumption.

Flotation of oxidized minerals of copper using a new synthetic chelating reagent as collector

Abstract A new synthetic reagent containing a mixed aliphatic-aromatic structure, with a hydrocarbon chain and an aminothiophenol chelating group, has proven to be an effective collector for the flotation of chrysocolla minerals. The flotation is optimum in the narrow pH range of 5.5 to 6, falls sharply at pH 5, and is moderate in the pH range 7 to 11. Infrared spectra indicate that copper aminothiophenolate chelates are formed on the surface of the chrysocolla under the conditions of maximum flotation.

New reagents in sulphide mineral flotation

Abstract A review is presented of new reagents for sulphide flotation. These reagents are essentially of the chelating type. Compared with conventional reagents they have a marked selectivity for individual sulphide minerals. The review hinges around: collecting power towards various sulphides and comparison with conventional reagents; influence of molecular structure on collecting power and action mechanism; and criteria for designing and synthesizing chelate-type collectors with optimal structure for a given metallic mineral.

Flotation of oxidized lead minerals with derivatives of 2-mercaptobenzothiazole. Part 1: chemical equilibria in the system 6-methyl-2-mercaptobenzothiazole-lead salts

Abstract A new flotation collector 6-methyl-2-mercaptobenzothiazole (MMBT) was investigated. The dissociation constant for the acidic form was measured. Two insoluble lead complexes of MMBT with lead were synthesized and characterized for the first time and their solubility products were measured. On the basis of these data and literature data for the equilibria between lead salts and aqueous solutions, the chemical equilibria for the systems: solution of MMBT-insoluble lead salt were calculated. Lead salts which may form lead minerals or may appear as oxidation products on the surface of galena were taken into account. The domains of existence for different species and equilibrium concentrations for MMBT at different conditions have been presented in the form of distribution diagrams. The results of calculations were compared with the Fourier Transform Infrared Internal Reflection Spectrometric (FT-IR IRS) measurements of the interaction of MMBT solution with the oxidized galena surface.

Infrared study of 2-mercaptobenzothiazole and two of its derivatives adsorbed on PbS

Abstract An infrared study has been carried out on 2-mercaptobenzothiazole and two of its derivatives (6-methyl-2-mercaptobenzothiazole and 6-methoxy-2-mercaptobenzothiazole) adsorbed on the PbS (galena) surface from aqueous solution. Different molecular structures were tested in order to observe the influence of the ring substituents on the surface interaction. The Pb bulk complexes of the studied molecules and the PbS surface treated in their aqueous solutions have been compared. The difference in adsorption on PbS was studied by varying the concentration of the reagents.

Interaction of glycine and a glycine-based polymer with xanthate in relation to the flotation of sulfide minerals

Abstract The interaction between the amino acid glycine, a polymer (BA/13) with a glycine functional group incorporated into its backbone structure, and three sulfide minerals (chalcocite, galena and pyrite) was investigated using settling tests, electrokinetic measurements, and dissolution studies. The resulting increase in pulp stability and changes in zeta potential are related to the adsorption of metal glycinate complexes that form in aqueous solutions of the sulfide minerals. Chalcocite exhibited the greatest interaction with glycine due to the high stability of the copper glycinate complexes as compared to those of lead and iron. In flotation with xanthate as collector, glycine increased the flotability while BA/13 completely depressed all three minerals. Again these results are attributed to the adsorption of glycine-metal complexes.

3,4-(Methylenedioxy)benzyl acrylate/acrylic acid copolymers as selective pH-controlled flocculants for finely divided titanium minerals

Abstract Fully synthetic tailor-made radical copolymers of 3,4-(methylenedioxy)benzyl acrylate with acrylic acid afforded excellent pH-controlled selective flocculation of aqueous ultrafine dispersions of the titanium minerals rutile and ilmenite. Sedimentation experiments proved that the copolymers, characterized by osmotic molecular weights in the range of 35 000–476 000 Da, produced stable, well separable flocs with rutile or ilmenite at acidic pH while they did not flocculate gangue minerals such as quartz. They showed the distinctive, very useful property of reversibly changing their effect from flocculation to dispersion or neutral by changing the pH. The formation of flocs is interpreted on the basis of a preliminary gathering process of the particles determined by the pH-dependent alteration of the particle surface solvation carried out with the copolymer.

SYNTHETIC COPOLYMERS CONTAINING FREE OR PROTECTED CATECHOL RESIDUES FOR THE pH-CONTROLLED SELECTIVE FLOCCULATION OF ULTRAFINE DISPERSIONS OF ILMENITE WITH RESPECT TO RUTILE

ABSTRACT Several multifunctional polymers for the pH controlled flocculation of titanium minerals active towards ilmenite and selective respect to rutile have been prepared. They are radical vinyl copolymers containing catechol functions either free or protected and acrylic acid units. They show the distinctive property of changing their effect from flocculating to dispersing or inert and vice versa by changing pH, with great advantages for the best fulfilment of the flocculating process. The tendency of the ilmenite particles to gather, as a result of the combined effect of the cathecholic and carboxylic functions at acidic pH, is considered an essential conditions and a preliminary process for the formation of floes

Synthetic Copolymers Tailor-Made for the pH Controlled Selective Flocculation of Extrafine Dispersions of Ilmenite with Respect to Rutile

Following a new Methodical approach to fully synthetic tailor-made polymeric flocculants for a given mineral dispersion, we prepared several multifunctional poolymers for the pH controlled selective respect to rutile. They had the structure of radical vinyl copolymers containing 1,2-catecholic functions either free or protected and acrylic acid units. They also had the distinctive property of changing their effect from fuocculating to dispersing or best fulfilment of the flocculation process. The tendency of the ilmenite particles to gather, as a result of the combined effect of the catec holic and carboxylic functions at acidic pH, is considered and essential condition and a preliminary process for the formation of flocs.