The role of silver minerals on the cyanidation of gold particles embedded within multi‐sulphidic mineral matrices

The effect of silver minerals on the dissolution behaviour of gold particles embedded within multi‐sulphidic minerals was investigated. A multi‐layer packed‐bed reactor approach was used to study the leaching behaviour of free gold (within silica) and gold associated with a series of synthetic multi‐mineral systems consisting of pyrite, silica, and successively, X = chalcopyrite, sphalerite, and stibnite. The reactor was filled with sieved powders of sulphidic minerals (pyrite, X), gold and silica and arranged as electrically‐isolated three‐layer //Pyrite//X//Silica// and two‐layer //Pyrite + X//Silica// systems. Gold powder was introduced successively in each layer of the three‐ and two‐layer mineral systems and the gold leaching behaviour was studied. The highest gold recovery was achieved for the gold particles within the pyrite layer while the lowest was within the silica layer. In case of the //Pyrite//Stibnite//Silica// system, the surface passivation inhibited gold leaching strongly. Gold cyanidation experiments were also performed with the addition of silver minerals, with both Au and Ag minerals dispersed in a three‐layer //Pyrite//X//Silica// and two‐layer //Pyrite + X//Silica// systems. Silver minerals addition proved beneficial for the pyrite‐sphalerite‐silica system. Gold leaching was severely retarded for the pyrite‐chalcopyrite‐silica and pyrite‐stibnite‐silica systems. Passivating films were observed at the surface of gold particles in case of gold cyanidation with pyrite‐chalcopyrite‐silica and pyrite‐stibnite‐silica systems.

     

Effect of thermal history on high‐valence chromium ion dissolution in merwinite (3CaO·MgO·2SiO2)

Solubility and local structure of transmission elements in calcium silicate compounds has not been well understood. We investigate the local structure of chromium ions dissolved in merwinite (3CaO·MgO·2SiO₂) of a monoclinic crystal structure. The acceptance of doping elements into merwinite has not been reported before. We found that chromium ions are soluble in merwinite in air and that chemical valence of the dissolved Cr ions varies with annealing temperature. The absorption edge in the x‐ray absorption near edge structure (XANES) of Cr‐doped merwinite indicated that octahedrally coordinated Cr³⁺ ions were mainly formed when annealed at 1673 K in air. A pre‐edge peak was also detected, indicating the existence of tetrahedrally coordinated high‐valence Cr ions. Conversely, through annealing of merwinite at 1123 K in air, tetrahedrally coordinated Cr⁶⁺ ions were found to be the main form of chromium. XANES spectra simulated by first‐principle calculations were used to explain the structural features in the observed spectra. We propose the coexistence of Cr³⁺ ions in octahedral Mg²⁺ sites and high‐valence Cr ions in tetrahedral Si⁴⁺ sites. In addition, a change in the chromium ion oxidation state in tetrahedral coordination sites was suggested by XANES spectroscopy of Cr‐doped merwinite synthesized at 1673 K and reannealed at 1123 K.     

Aluminum-containing mesostructural materials

This article reviews syntheses of mesoporous aluminosilicates and aluminum oxides based on surfactant templating methods. The incorporation of aluminum in the silicate frameworks generates acid sites and ion-exchange sites. Both, tetrahedral framework aluminum and octahedral extraframework aluminum can be present, depending on the aluminum precursor used. The aluminum-containing structures tend to be less ordered than their purely siliccous analogs. Dealumination plays a significant role during template removal. Other methods for the synthesis of mesoporous aluminum-containing sieves are based on the structural transformation of kanemite, and on cluster precursors which may be connected by self-condensation or by condensation with silicate bridges. Purely aluminous mesostructures can be prepared with neutral templates or by condensing Keggin-like aluminum clusters in an ordered salt with an anionic surfactant.     

Hexadecyl-functionalized lamellar mesostructured silicates and aluminosilicates designed for polymer-clay nanocomposites. Part I. Clay synthesis and structure

Motivated by a need for synthetic clays that can be dispersed and exfoliated in polymer melts without added compatibilizers, lamellar mesostructured silicates and aluminosilicates with covalently attached hexadecyl functional groups (C₁₆-LMS and C₁₆-LMAS, respectively) were prepared by sol-gel syntheses and their structures were characterized. Based on XRD and TEM data, lamellar products with layer spacings of 4.8-4.9 nm were obtained between room temperature and 60 °C (C₁₆-LMS) or 70 °C (C₁₆-LMAS). The degree of condensation of the aluminosilicate layers increased at the higher synthesis temperatures. Attachment of organic groups to the inorganic sheets was confirmed by ²⁹Si solid state MAS NMR and IR spectroscopy. The sheets of C₁₆-LMS consisted of single or double layers of tetrahedral silicate groups, each attached to a hexadecyl chain. C₁₆-LMAS was composed of pyrophyllite-like layers (Si:Al=2) with an octahedral aluminum layer sandwiched between two tetrahedral silicate layers and hexadecyl surface groups. Tetrahedral aluminum sites were also present. The clay layer spacing could be increased to 5.2 nm by addition of tetraethoxysilanes during the synthesis (C₁₆-SiO₂-LMAS). C₁₆-SiO₂-LMAS was structurally similar to C₁₆-LMAS; however, the presence of additional silicate groups in this structure increased the inorganic layer thickness and introduced further structural disorder.     

Wettability of porous anodic aluminium oxide membranes with three-dimensional,layered nanostructures

The architecture-dependent wettability of three-dimensional (3D), porous anodic aluminium oxide (AAO) membranes with varying surface morphologies including hierarchical, mesh and honeycomb nanostructures is reported. The surface morphology and underlayer structure play different roles in regulating the wetting behaviour of the AAO membranes. For the mild AAO membranes, the wetting behaviour of the ultra-thin top layer is dominated by the surface morphology in which the water contact angles (WCAs) of the AAO membranes with hierarchical, mesh and honeycomb structures are approximately 113.7°?±?4.6°, 94.9°?±?0.7° and 98.8°?±?5.8°, respectively. The wetting behaviour of the 3D, layered AAO membranes is dominated by both the surface morphology and the underlayer structure. Notably, the WCA of the mild AAO membrane with a layered hierarchical structure increases in the second layer (increase in the hole density). The WCAs of the three kinds of layered hard AAO membranes decrease in the second layer (increase in the hole depth) and then decrease slowly or increase in the third transition layer (decrease in the hole density). The WCAs of all the AAO membranes decrease linearly at different rates with the formation of the ordered bottom layer. The above results can facilitate the engineering of nanostructures for controlling the surface wetting behaviour of materials and devices for applications in multiple fields.     

Spectroscopic Behavior of Iron(III) in Silicate Glass

The coordination of ferric iron was studied in lead silicate and lead-sodium silicate glasses by optical spectroscopy in the region 11000 to 28500 cm⁻¹.There is clear evidence from the spectra ofFe³⁺ octahedral and tetrahedral coordination, which is also supported by ligand field calculations.     

Structures and Phase Relations of Aluminum-Substituted Calcium Silicate Hydrate

The structures of aluminum-substituted calcium silicate hydrate (C-S-H) forming in a series of aqueous suspensions formulated with colloidal silica, reactive alumina, and lime and aged for 1 year have been studied using ²⁹Si and ²⁷Al magic angle spinning nuclear magnetic resonance spectroscopy (with and without cross polarization (CP)), solution pH, electron microscopy, and X–ray diffraction. As in earlier work dealing with the nature of C-S-H in the system CaO-SiO₂H₂O₂ two aluminum-substituted C-S-H phases, having distinctly different anionic structures on the atomic level (Q₂ versus Q₁Q₂), were found to extend into the system CaO-Al₂O₃-SiO₂-H₂O₂ X-ray diffraction patterns of the two aluminum-containing C-S-H phases are nearly identical, suggesting that their intermediate-range order is very similar, but MASNMR spectra show that these two phases have markedly different silicate structures on the atomic-level scale. Both C-S-H structures can accommodate approximately 5 mol% of Al₂O₃ in tetrahedral and possibly octahedral coordination as well.     

Relationship between the colloidal and rheological properties of mineral suspensions

The electrokinetic and rheological behaviour of lateritic aqueous suspensions has been analyzed as a function of samples chemical composition, pH of suspensions, and nature and concentration of electrolyte added to the aqueous suspensions. First, it was determined that the isoelectric point (IEP) of suspensions in the presence of non‐adsorbing electrolytes is a function of the ratio serpentine/ goethite present in samples. The flow properties of the suspensions are strongly dependent on pH, reaching the highest values of apparent viscosity at values around the isoelectric point. Specific adsorption of silicate and magnesium species on particles surface was revealed by a shift in the IEP. In particular, silicate anions shifted the IEP value to acidic pH whilst magnesium cations shifted the value to basic pH. A similar trend was displayed in the rheological behaviour of suspensions where the highest viscosity values were shifted to the same direction.     

Bitumen content estimation of Athabasca oil sand from broad band infrared reflectance spectra

Oil sand is a mixture of quartz grains, clay minerals, bitumen, water, and minor accessory minerals. There is a need in oil sands mining operations for a robust method to estimate total bitumen content in real time; and so modelling of the total bitumen content (TBC) in Athabasca oil sands of Western Canada was undertaken on the basis of hyperspectral reflectance spectra. A selection of different bitumen, water, and clay mineral spectral features (3.0–30.0 µm) was used to develop broad‐band TBC predictive models that have good accuracy, with less than 1.5% error with respect to laboratory methods of bitumen assay. These models are also robust, in that they are independent of mine location. Simple broad band models, based upon previously identified Gaussian features or wavelet features, provide an incremental improvement over the currently deployed industry two‐band ratio model. An improved two‐band model was also developed, which makes use of a combination of the same two bands but normalised to their mean. A wavelet‐based, broad‐band model comprised of indices and five bands, where the bands are normalised to the mean of the bands, adequately addresses the influence of water, clay, and textural variation on selected bitumen features. This five‐band model appears to produce the most robust estimator of TBC, with a dispersion of ∼1.1–1.5%, which can be applied to different sites within a mine and to different mines without additional tuning or calibration, as evidenced by regression slopes of 0.99–1.0 for modelling, validation, and blind data sets.     

粉煤灰研磨过程中铝氧多面体结构变化的核磁共拓研究

采用核磁共振（NMR）技术和SEM方法，对机械研磨的粉煤灰中铝氧多面体结构的变化进行了研究。研究发现：在粉煤灰研磨过程中，煤粉灰中的铝氧多面体结构发生明显的变化，原先的6配位网络不对称大分子结构在机械力的作用下发生键断裂，向6配位铝氧多面体对称小分子结构转变；4配位的铝氧多面体网络不对称大分子结构变化不明显，当经过长时间研磨后，所谓粉煤灰颗粒发生的变化，从NMR谱图得出的解释是：裂解的6配位铝氧多面体对称小分子结构重新向6配位铝氧多面体不对称网络结构再转变的过程，机械研磨导致这种可逆变化，粉煤灰研磨过程中，水介质的氢键作用强于机械力作用，强于机械热的作用。     

Fabrication of biomimetic gecko toe pads and their characterization

The mimicking and fabrication of gecko toe pads structures can lead to limitless applications. In this study, polypropylene (PP), polyethylene (PE) and polycaprolactone (PCL) nano‐fibers are fabricated using a porous membrane as template. The surface characteristics and physical properties of the samples yield different geometries, which determine the wetting and adhesive properties of the fabricated samples. Oriented and wave‐like shapes fibers present the Gecko effect, thanks to their ability to comply and hydrophobic asperities that uphold the water droplet when the wetting properties were tested. The samples are also found to be self‐cleaning due to their high contact angles and low contact angle hysteresis. Adhesion tests results prove that the samples are high reversible adhesion with the ability to stick to smooth surface in a dry and underwater environment. The adhesion on the samples can be enhanced with a double fibril layer or buckling property. They adhere better when the surface is not hydrophilic. By behaving in similar way as the real geckos, the results of this study show that the fabricated samples effectively present the Gecko effect. POLYM. ENG. SCI., 57:283–290, 2017. © 2016 Society of Plastics Engineers     

Infrared spectroscopy of NH4-bearing and saturated clay minerals: A review of the study of layer charge

Infrared (IR) spectroscopy study of the layer charge of clay minerals demonstrates that the υ₄ NH₄⁺ band, assigned to the deformation vibrations of the NH₄⁺ ion can be used to evaluate the charge characteristics of NH₄⁺-bearing clay minerals. Total accessible charge, equivalent to cation exchange capacity (CEC), as well as tetrahedral and octahedral charge distribution in both dioctahedral and trioctahedral smectites are determined by quantifying the υ₄ NH₄⁺ band before and after lithium treatment. When using the KBr pressed pellets technique, the position and the shape of the υ₄ NH₄⁺ bands can distinguish exchangeable and fixed NH₄⁺ in clay minerals.     

Study of water‐mist behaviour in hot air induced by a room fire: Model development,validation and verification

Water‐mists are emerging as an effective agent for the suppression of fires. However, the mechanisms of suppression are complex and the behaviour of individual water droplets in a smoke layer generated by fires must be quantified. This study investigates the behaviour of individual droplets injected from a nozzle into a hot air environment induced by a room fire. A semi‐empirical model has been developed based on the conservation of mass, momentum and energy to evaluate the heat and mass transfer phenomena in an air‐water droplet system. The model has considered the effect of change of momentum of an evaporating droplet. A forward finite difference approach is applied to solve the governing time dependent ordinary differential equations. The droplets are considered to be ‘lumped mass’ and variable thermo‐physical properties of water and air and the change of Reynolds number of the droplets, due to the change of their diameter and velocity are considered. The effect of high evaporation rate on the mass and heat transfer coefficient and the contribution of radiation emanating by a flame and the surrounding boundary walls are also considered in the model which were not taken into account in the previous studies. Experimental data on terminal velocity and adiabatic saturation temperature are used to validate and verify the model. The validation and verification indicate that the proposed model predicted the terminal velocity within 4% of the experimental data and predicted the saturation temperature within 5% of the adiabatic saturation temperature. This semi‐empirical model is also used as a tool to validate a more comprehensive computational fluid dynamics (CFD) based tool, Fire Dynamics Simulator (FDS). It is found that FDS results agree well with the results of the proposed model. Furthermore, the proposed model can be used to evaluate the temperature, velocity, diameter and other physical properties of a droplet travelling through a layer of hot air. Copyright © 2014 John Wiley & Sons, Ltd.     

Ligand-Field Spectra and Structure of Nickel in Silicate Glasses

The spectra of nickel dissolved in silicate and aluminosilicate glasses with alkali and alkaline-earth modifiers were studied systematically as functions of composition, annealing and temperature, concentration of Ni²⁺, and redox conditions during melting. Although reducing conditions produced a gray scattering phase, only Ni²⁺ was observed as a dissolved species. Several glasses contained one of two Ni²⁺ species which corresponded to previously proposed 4- and 6-coordinated species. Therefore, both octahedral and tetrahedral calculations could be made from directly observed bands free of overlapping. The results of these calculations suggest that the postulated tetrahedral species may instead be cubic (8-coordinated). In addition, mixing of the Ni²⁺³ T _{1 g} ( P ) level with Ni²⁺ 4 p and/or ligand electron transfer bands was observed. Examination of the conditions that could produce the 8-fold site on the basis of stereochemical and crystal-chemical principles indicated that the packing requirements of the alkali-oxygen, alkaline-earth-oxygen, and silicate polyhedra may preclude sites other than a large 6-fold site or an even larger cubic (8) site. Thus, silicate glasses can be considered to consist of highly structured but disordered atomic arrangements.     

Heavy metal-adsorption on micas and clay minerals studied by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) was used to study the adsorption of Cs-, Ba-, Cu-, Zn-, and Pb-ions on the external surfaces of various, well characterized 2:1 layer silicates (micas and illites).Before studying metal adsorption, it was necessary to determine the charge magnitude of the adsorption surface. This was done for chemically well-characterized micas (margarite, muscovite, sericite). The XPS analyses showed that the depth of analysis is about 15 Å. As a result it was possible to measure the surface- and interlayer ions on both sides of the outermost 2:1 layer. In determining the layer charges, the following strategy was used. The outer surface cations were replaced by Ba²⁺, giving, for ideal margarite an interlayer cation (Ca²⁺)/surface cation (Ba²⁺) ratio of 2:1 and in the case of muscovite a K⁺/Ba²⁺ ratio of 4:1. Deviations from these ratios indicate an asymmetry of layer charge in the outer sheet. Using the margarite, muscovite and sericite as standards, surface charge determination of a number of micas, illites, and I/S clays could be carried out by XPS.The properties of the metal-ions (charge, ionic radius, ionic potential), as well as layer charge characteristics of the clay, including surface charge magnitude and point of origin from tetrahedral or octahedral substitution, are factors which influence adsorption selectivity [Sposito, G., 1989. Surface reactions in natural aqueous colloidal solutions, G. Chimia, 43, 169–176]. The selection of previously well-characterized minerals, margarite, muscovite, celadonite, illite, montmorillonite, and beidellite for XPS study made it possible to relate these factors to heavy metal adsorption by the clay minerals.The results show that Cu²⁺ and Zn²⁺ are adsorbed as monovalent ions, presumably as (CuOH)¹⁺ and (ZnOH)¹⁺ hydroxy surface-complexes, due to their high ionic potential. Saturating the mica series with equimolar pairs of Cu–Zn and Cu–Pb, the ratios of Cu/Zn and Cu/Pb increase systematically with external surface charge. The higher the surface charge, the more selective is the exchange process for Cu with respect to Zn or Pb. Increasing external surface charge parallels increasing tetrahedral charge, which indicates that selectivity takes place at points of tetrahedral negativity on the crystallite surface, whereas octrahedral charge plays little role in the selective adsorption process.     

蒙脱石制备插层复合材料的研究进展

蒙脱石是一种具有离子交换性的层状硅酸盐粘土矿物,利用其结构特性可以制备插层复合材料。这种通过插层反应得到的复合材料兼有无机主体和客体分子的性质,从而表现出不同于单一组分所具有的催化、吸附以及光、电、磁等性能,在构筑下一代的光学、光电纳米器件,化学或生物传感器,分子识别以及催化等领域存在潜在应用的价值。     

The cracking behaviour of allophane- and ferrihydrite-rich materials; Effect of pretreatment and material amendments

The cracking behaviour of an allophanic material has been investigated by sedimenting an aqueous suspension of the material onto a filter paper in a Buchner funnel, and allowing the filter pad to dry out at ambient humidity and temperature. Cracking was assessed in terms of the area occupied by cracks, maximum crack width, and number of integral (polygonal) pieces. Using a standard size funnel, the extent of cracking was influenced by the thickness of the sedimented material. For a given pad thickness, however, the initial moisture content (IMC) of allophane was the major factor determining cracking behaviour. Prior air-drying (IMC ∼25% w/w) reduced the amount of cracking by more than half while prior oven-drying (IMC ∼0%) inhibited cracking altogether. These observations have been interpreted in terms of the particulate structure of allophane and its drying-wetting characteristics.Addition of polyacrylamide or calcium hydroxide to allophane reduced crack formation. This effect has been ascribed to inter-aggregate bonding by the polymer and to a chemical reaction between allophane and hydrated lime.Ferrihydrite-rich natural material showed a similar cracking pattern to the allophanic sample but the cracks formed were not as wide. On the other hand, soils rich in crystalline layer silicate minerals cracked much less than their allophanic counterpart unless the latter had previously been air-dried. Unlike allophane, the platy crystallites of these minerals could presumable associate in a face-to-face configuration, giving rise to a relatively high cohesive structure. The observed order of cracking propensity: montmorillonite > kaolinite ⪢ vermiculite > illite probably reflected the extent to which face-to-face interactions could occur. These in turn, appeared to depend on the crystallite size and the surface properties of the respective layer silicate.Addition of polyacrylamide to allophane- and ferrihydrite-rich materials enhanced their permeability by strengthening the inter-aggregate pore surfaces. As a result, the hydraulic conductivity of plugs of these materials was increased.     

Comparison of methods for the determination of the layer charge density (LCD) of montmorillonites

Two wide spread methods exist for the determination of the layer charge density (LCD) of montmorillonites.

• 1)Structural formula method (SFM): calculation of the structural formula based on the chemical composition (Ross, C.S., Hendricks, S.B. (1945): Minerals of the montmorillonite group. — U. S Geol Surv Profess Paper 205-B, p. 23–79.; Stevens, R.E. (1946): A system for calculating analyses of micas and related minerals to end members. — Contributions to geochemistry, 1942–45, Geological survey bulletin, 950, p. 101 – 119.; Grim, R.E., Güven, N. (1978): Bentonites – geology, mineralogy, properties and uses. – Developments in sedimentology 46, Elsevier, New York, pp. 254.; Newman, A.C.D., Brown, G. (1987): The chemical constitution of clays. In: Chemistry of clays and clay minerals, Mineralogical Society Monograph No. 6, Newman, A.C.D. (ed.), John Wiley and sons, New York, p. 1 – 128.; Laird, D.A. (1994): Evaluation of the structural formula and alkylammonium methods of determnining layer charge. — In: Mermut, A.R., editor: Layer charge characteristics of 2:1 silicate clay minerals, CMS Workshop Lectures Vol. 6, Boulder, CO, Clay Miner. Soc., p. 79 – 104).
• 2)Alkylammoniummethod (AAM): calculation of the LCD from measuring the d-spacing after intercalation of a set of n-Alkylammoniumions (Lagaly, G. (1994): Layer charge determination by alkylammonium ions.—In: Mermut, A.R., editor: Layer charge characteristics of 2:1 silicate clay minerals, CMS Workshop Lectures Vol. 6, Boulder, CO, Clay Miner. Soc., p. 1 – 46).

The SFM generally provides higher values (up to 40%, Laird, D.A. (1994): Evaluation of the structural formula and alkylammonium methods of determnining layer charge. — In: Mermut, A.R., editor: Layer charge characteristics of 2:1 silicate clay minerals, CMS Workshop Lectures Vol. 6, Boulder, CO, Clay Miner. Soc., p. 79 – 104.). Currently, most clay mineralogists from all over the world use either SFM or AAM which leads to incomparable results. In order to unambiguously prove which method provides correct values for the LCD and to be able to calculate correct montmorillonite contents two alternative methods (method A1 and A2) are tested in this paper. These procedures are independent from the well accepted SFM and AAM. Method A1, based on the determination of CEC and inner surface area by water adsorption, failed because water adsorption depends to a higher degree on the amount of exchangeable cations than on the surface area. Method A2 is based on measuring the variable charge, the total charge (CEC) of a pure smectite fraction, and the molar mass of a formula unit. This method (A2) is applicable if fine grained impurities do not interfere with the production of the pure smectite fraction. In conclusion, by applying a fully independent method for determining the LCD the results obtained by the AAM were confirmed. This data strongly indicates that the AAM as proposed by Lagaly (1994)[Lagaly, G. (1994): Layer charge determination by alkylammonium ions.—In: Mermut, A.R., editor: Layer charge characteristics of 2:1 silicate clay minerals, CMS Workshop Lectures Vol. 6, Boulder, CO, Clay Miner. Soc., p. 1 – 46.] provides reasonable values for the LCD. Additionally, it is shown that high LCD values as commonly determined by SFM for medium to high charged smectites cannot lead to the calculation of correct montmorillonite contents. However, there is no doubt, that high charged and hence non-swellable 2:1 layer silicates cannot be investigated by the AAM (as discussed by Mermut, A.R. (1994): Problems associated with layer charge characterisation of 2:1 phyllosilicates. — In: Mermut, A.R., editor: Layer charge characteristics of 2:1 silicate clay minerals, CMS Workshop Lectures Vol. 6, Boulder, CO, Clay Miner. Soc., 79 – 104).     

One-dimensional structure of exfoliated polymer-layered silicate nanocomposites: A polyvinylpyrrolidone (PVP) case study

Classical modeling of powdered lamellar structures by X-ray diffraction (XRD) only applies to periodic or quasi-periodic structures and another approach is needed for non-periodic structures. XRD patterns of the non-periodic structures contain a relatively small amount of information and therefore certain initial assumptions are necessary. In case of exfoliated polymer–clay mineral nanocomposites it is possible to assume the chemical composition and the structure of the clay mineral layer while the actual structure of the polymer remains unknown. This paper offers an approach which can be used to provide an approximate solution for the structure of the polymer. This new approach is based on modeling of the LpG² factors, recorded from oriented samples in order to obtain the one-dimensional structure of the polymer.Although LpG² factors for various smectites are quite different, in the case of polyvinylpyrrolidone (PVP) adsorbed on smectite it was found that the structure of the polymer was insignificantly affected by charge in the tetrahedral or octahedral positions of the smectite. The electron density distribution models of PVP directly adsorbed on the smectite layer suggest that PVP chains directly bound to the surface are more rigid and organized than the molecules occurring farther away. The approximate thickness and distribution of PVP layer adsorbed on the surface was calculated to be equal ca. 5–6 Å.     

矿物表面金属离子组分与糊精的相互作用（Ⅰ）──糊精在矿物表面的吸附

通过矿物表面糊精吸附量的测定、电动电位测定及在不同ｐＨ值下矿物表面羟基浓度的测定，系统探索了糊精在赤铁矿、金红石、方解石、萤石、重晶石、磷灰石及硅灰石等氧化矿和盐类矿物表面附吸的规律，发现糊精的吸附主要是由于与矿物表面金属羟基化合物发生了程度不同的化学作用。