Separation of different calcium minerals have long been an interesting and challenging problem. In this investigation calcium mineral separation is examined by: microflotation, zeta potential measurement and adsorption, using novel collectors having two functional groups instead of one. In theory, by varying the distance between the functional groups, it could be possible to preferentially target one calcium mineral by matching the spatial distance between the sites on the mineral surface. In this investigation two new surfactants have been tested to estimate their ability to float apatite and/or calcite.Preliminary findings show that an increase in distance between the functional groups favors one mineral over the other, and this might be due to differences in the mineral surface structure.

Almost all of the flotation reagents used today were discovered by continued application of empirical methods and/or trial and error experimentation. Moreover, with the metal-ion specific approach used so far, it is difficult to separate the minerals containing the same constituent metal ion. A critical assessment of molecular recognition processes involved in biomineralization suggested the possibility of using reagents which are surface specific. The concept that the molecules consisting of two or more functional groups having appropriate spacing between those so as to achieve structural/stereochemical compatibility during interaction with the mineral surface exhibit structure-specificity is thought to be extended to the design of specific collectors in flotation processes. In the present study, for the first time, a rational design of surface active molecules, and thereby the recognition of crystal faces (of minerals) by these molecules through structural and stereochemical matching is being utilized successfully to selectively float various minerals. For this purpose, carboxylate-based collectors (for mineral specific flotation of calcium minerals) as well as xanthate-based collectors (for mineral specific flotation of sulphide minerals) with a fixed alkyl chain length but having two functional groups with varying geometrical distances (separated by a spacer of one, two and three carbon atoms) between them have been synthesized. In this article, we have discussed the design, synthesis, purification of these novel mineral specific collectors as well as their important solution parameters in relation to flotation processes.

The present investigation aims to develop and distinguish mineral specific reagents with two functional groups for use in flotation of calcium containing minerals. For this purpose, a series of dicarboxylate-based surfactants with varying length between the carboxylate groups (one, two or three methylene groups) were synthesized. As reference, a surfactant with the same alkyl chain length but with only one carboxylate group in the polar part was synthesized. The adsorption behavior of these new reagents on pure apatite and calcite mineral surfaces was studied using Hallimond tube flotation, FTIR and ζ potential measurements. The relation between the adsorption behavior of a given surfactant on a specific mineral surface and its molecular structure over a range of concentration and pH values, as well as the region of maximum recovery were established. It was found that one of the reagents, with a specific distance between the carboxylate groups, was much more selective for a particular mineral surface than the other homologues synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in flotation studies is substantiated by ζ potential and infra-red spectroscopy data.

Rare Earth Elements are known to occur within apatite‐magnetite ores of the Kiruna type. Previously it was assumed that the REE was associated to the apatite part of the ore. It is now shown that the REE follows the apatite to a much less degree, and that the REE are contained in the minerals monazite, allanite and some unknown REE‐phase still to be identified. Monazite occurs as inclusions in the apatite as well as free particles. Allanite is to some degree in mixed grains with magnetite but also in free particles. Monazite mainly reports to the apatite concentrate while allanite largely goes to the tailings. Laboratory flotation also shows some preferential concentration of heavy REE over light REE to the apatite concentrate. A new EU project, REEcover, will characterise the REE phases in this type of iron ore and among the different process streams within the mineral beneficiation chain.

A lead sulphide film precipitated on a zinc sulphide layer of an ATR crystal has been used to study in situ surface reactions of heptyl xanthate adsorption. The lead sulphide film was made by the chemical bath deposition method and was analyzed by X-ray photoelectron spectroscopy. In turn deposited layers make it possible to study the PbS/aqueous solution interface in situ and open up interesting areas for attenuated total reflection spectroscopy. Monitoring the adsorption of heptyl xanthate from a 0.1 mM aqueous solution using the vibration band at 1200 cm-1 has shown the existence of adsorbed molecules on the lead sulphide surface as well as precipitated lead xanthate on the surface at bulk concentrations higher than 1 mM. At lower concentrations, the adsorbed species are dominant as is the precipitate at higher concentrations. The rate of adsorption is in accordance with pseudo first-order kinetics with a rate constant of 0.21 s-1. The Dichroic ratio for heptyl xanthate adsorbed on PbS indicates the hydrocarbon chain of the heptyl xanthate to be preferentially orientated perpendicular to the surface normal of the internal reflection element.

Dithiophosphates are used in many different industrial applications. To explain their functions and properties in these applications, a fundamental understanding on a molecular level is needed. Potassium O,O′-Dibutyldithiophosphate and its anion have been investigated by means of a combination of DFT and 31P CP/MAS NMR and infrared spectroscopy. Several low-energy conformations were studied by DFT. Three different conformations with significantly different torsion angles of the O-C bond relative to the O-P-O plane were selected for further studies of infrared frequencies and 31P NMR chemical-shift tensors. A good agreement between theoretical and experimental results was obtained, especially when the IR spectra or 31P chemical shift tensor parameters of all three conformations were added, indicating that, because of the low energy difference between the conformations, the molecules are rapidly fluctuating between them.

The in situ adsorption of n-heptyl xanthate on a germanium multiple internal reflection element was studied at constant ionic strength and X-ray photoelectron spectroscopy was used in the investigation of the germanium surface. The kinetics of heptyl xanthate adsorption was evaluated using the integrated absorbance of a sub-band under the vibration at 1200 cm−1. This vibration was assigned to the adsorbed xanthate molecule. It was shown that the adsorption of heptyl xanthate can be represented by a pseudo-first-order rate law and a monodentate binding of the xanthate to the germanium surface is proposed. During the adsorption of xanthate, the dimeric form of xanthate was simultaneously formed.

In this investigation, adsorbed heptyl xanthate on a Ge(111) surface was studied, as well as the free heptyl xanthate molecule, by means of first-principle density functional theory calculations. The modeled results were compared with the in situ total internal reflection vibrational spectroscopy spectra of heptyl xanthate adsorbed on a germanium internal reflection element and the transmission infrared spectrum of a heptyl xanthate ion in aqueous solution. The assignments of the vibrational frequencies were done for the adsorbed xanthate. The region between 1150 and 1000 cm(-1) seems suitable for discussing differences between an adsorbed xanthate and its corresponding ion. The modeled spectra for both the adsorbed xanthate and the xanthate ion are in good agreement with the experimentally retrieved spectra. This investigation shows the strength of using DFT calculations in the interpretation of absorption bands from molecules adsorbed at surfaces in situ.

Geometrical structure and vibrational modes of potassium and sodium ethyl/heptyl xanthates were studied, using both theoretical and experimental methods. Both Hartree-Fock and density functional theory were used. The experimental method used was infrared absorption spectroscopy (FTIR). Our work showed that vibrational frequencies calculated with density functional theory, using the local density approximation, are in very good agreement with experiments. The results were not improved by using the more sophisticated and computationally demanding B3LYP functional.