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Bastnaesite is an important rare earth mineral and is usually beneficiated by flotation. Sodium silicate is commonly used to depress calcium-bearing gangue minerals, however it can also depress bastnaesite when Ca2+ ions exist in the pulp. In this study, the effect of Ca2+ ions and sodium silicate individually or in combination on bastnaesite flotation was studied through micro-flotation, zeta potential, fluorescence spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. Micro-flotation results show that the combination of Ca2+ ions and sodium silicate depresses bastnaesite more severely due to their synergistic effect. Zeta potential results show that the combination renders the surface potential of bastnaesite negatively shifted more significantly. Fluorescence spectroscopy shows that the combination decreases the surface hydrophobicity of bastnaesite more severely. XPS shows that the combination increases the adsorption of sodium silicate on bastnaesite by forming hydrophilic Ca-SiO3 precipitate, which causes more serious depression on bastnaesite flotation.

Monazite ((Ce, La)PO4) is one of the major types of light rare earth minerals from which the light rare earth elements cerium (Ce) and lanthanum (La) are economically extracted. Flotation is extensively used to recover fine-grained monazite. Sodium oleate (NaOL) is considered as the collector with the strong collecting ability for monazite flotation. However, this study shows that its collecting ability is still limited. In this paper, a phosphonic acid, nonane-1,1-bisphosphonic acid (C9-BPA), was employed as the novel collector in place of NaOL. Flotation experiments show that even when the C9-BPA dosage is less than one-fifth of the NaOL dosage, the monazite recovery using C9-BPA as the collector is approximately 22 wt% higher than that using NaOL. The mechanism by which C9-BPA adsorbs on monazite was investigated using zeta potential, infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements as well as first-principles calculations. Zeta potential measurements show a more significant decrease in the zeta potentials of monazite after the addition of C9-BPA compared to those after the addition of NaOL. For C9-BPA-treated monazite, the characteristic peaks of C9-BPA were observed in the IR and C 1s XPS spectrum, whereas for monazite treated by NaOL, no characteristic peak of NaOL was observed. Experimental results show that C9-BPA has a stronger affinity towards the monazite surface than NaOL as confirmed by the higher adsorption energy of CP-BPA on the monazite surface (‒204.22 kJ/mol) than NaOL (‒48.48 kJ/mol). This study demonstrates an extensive application value and prospect of C9-BPA in monazite flotation and helps design novel collectors with strong collecting ability for monazite flotation.

Bayan Obo ore contains mainly bastnaesite, monazite and associated iron, fluorite, calcite, dolomite, barite, and trace amount of columbite. Due to its complex mineral compositions and similar mineral properties, it is difficult to separate and obtain rare earth and fluorite concentrates with high purity by conventional magnetic separation and flotation. In this paper, a stepwise magnetic separation process comprised of wet permanent magnetic separation (PMS), wet electromagnetic separation (EMS), and superconducting magnetic separation (SCMS) was proposed to pre-concentrate iron, rare earth, and fluorite minerals from Bayan Obo ore. The results showed that iron, rare earth, and fluorite preconcentrates with high purity and low impurity content could be achieved, which might be helpful to shorten the technological process and improve the separation efficiency for the subsequent flotation of iron, rare earth, and fluorite minerals.

Alternatives to bisphenol A (BPA) are developed for food contact materials as a result of increasing evidence of exposure-correlated harmful effects of BPA. In vitro assays provide the fast, affordable, and mechanism insightful ways to screen endocrine disruption (ED), which is a major concern of new BPA alternatives. In this review, we summarize the safety and regulation information on the alternatives to BPA, review the state of the art of in vitro assays for ED evaluation, highlight their advantages and limitations, and discuss the challenges and future research needs. Our review shows that ligand binding, reporter gene, cell proliferation, and steroidogenesis are four commonly used in vitro assays to determine the ED at the response of receptor, gene transcription, and whole cell level. Major challenges are found from in vitro-in vivo translation and identification of ED chemicals in polymers. More studies on these areas are needed in the future.

Thioamide substitutions in peptides can be used as fluorescence quenchers in protease sensors and as stabilizing modifications of hormone analogs. To guide these applications in the context of serine proteases, we here examine the cleavage of several model substrates, scanning a thioamide between the P3 and P3’ positions, and identify perturbing positions for thioamide substitution. While all serine proteases tested were affected by P1 thioamidation, certain proteases were also significantly affected by other thioamide positions. We demonstrate how these findings can be applied by harnessing the combined P3/P1 effect of a single thioamide on kallikrein proteolysis to protect two key positions in a neuropeptide Y based imaging probe, increasing its serum half-life to >24 h while maintaining potency for binding to Y1 receptor expressing cells. Such stabilized peptide probes could find application in imaging cell populations in animal models or even in clinical applications such as fluorescence-guided surgery.

Parisite (CaCe2(CO3)3F2) and bastnaesite (CeCO3F), important rare earth minerals, have different elemental compositions and crystal structures. Their flotation behavioral differences under commonly used sodium silicate (SS) depressant and hydroxamate collector are important for rare earth ore beneficiation, which is still unknown. In this study, the effect of sodium silicate on bastnaesite and parisite flotation with octyl hydroxamic acid (OHA) as collector was comparatively investigated through microflotation, zeta potential measurements, X-ray photoelectron spectroscopy (XPS), and mineral crystal computational analysis. The results indicated that the inhibition effect of SS on parisite was significantly stronger than that on bastnaesite. SS had little effect on the adsorption of OHA on bastnaesite surface, rendering a slight inhibition on bastnaesite flotation. However, SS strongly hindered the adsorption of OHA on parisite surface, rendering the heavy inhibition on parisite flotation. The inhibition mechanism of SS on parisite was due to the reaction of the calcium species with silicate, thereby forming Ca-SiO3 hydrophilic complex on parisite surfaces. This hydrophilic complex hindered the adsorption of OHA and increased the hydrophilicity on parisite surface, thus, causing significant inhibition on parisite flotation.

To explore the influence of long-term water immersion on the spontaneous combustion characteristics of coal, temperature-programmed test system and In-situ Fourier transform infrared spectroscopy (In-situ FTIR) were used. Differences in gas production of soaked coal and raw coal showed that the process of long-term water immersion played a different role before and after critical temperature. In the stage of surface oxidation, moisture could inhibit the spontaneous combustion of coal, when the critical temperature point was exceeded, it played a promoting role instead. As an explanation in support of the above arguments, the relative contents of active functional groups in raw and soaked coal were compared, which indicated that the process of water immersion could affect relative contents of hydroxyl, aromatic hydrocarbon, aliphatic hydrocarbon and oxygen-containing functional groups, giving rise to an acceleration in the reaction process of coal oxygen and exhibiting higher tendencies toward spontaneous combustion. A practical consequence of this finding is the soaking mechanism should not be neglected in any precautionary or preventive measures to avoid potential spontaneous combustion in overlying goaf of shallowly buried and close distance coal seams.

Lipid nanoparticles are increasingly used for drug and gene delivery, including the delivery of small interfering RNA (siRNA). Pulmonary delivery of drug molecules carried by lipid nanoparticles directly into the lung may improve the treatment of certain lung diseases. The present study was designed to test the feasibility of engineering aerosolizable dry powder of lipid nanoparticles by thin-film freeze-drying (TFFD). Solid lipid nanoparticles (SLNs) comprised of lecithin, cholesterol, and a lipid-polyethylene glycol conjugate were prepared by solvent evaporation. Dry powders of the SLNs were prepared by TFFD, spray drying, or conventional shelf freeze-drying. The physical and aerosol properties of the dry powders as well as the physical properties of the SLNs reconstituted from the dry powders were evaluated. The particle size, polydispersity index, and the zeta potential of the SLNs were preserved after they were subjected to TFFD and reconstitution, but not after they were subjected to conventional shelf freeze-drying and reconstitution, and the dry powder prepared by TFFD showed better aerosol performance properties than that prepared by spray drying. SLNs encapsulated with siRNA can also be successfully transformed into aerosolizable dry powder by TFFD, and subjecting the siRNA-encapsulated SLNs to TFFD did not negatively affect the function of the siRNA. It is concluded that TFFD represents a promising method to prepare aerosolizable dry powder of lipid nanoparticles.

The mechanisms for magnetizing roasting of Fe2O3 into Fe3O4 under microwave heating and electrical heating have been studied through thermogravimetric analyses, x-ray diffraction (XRD) measurements, and reaction kinetic calculations. In the reduction process, activated carbon was used as a reducing agent and argon as the protective gas. The results of heating tests indicated that the temperature heating speed during microwave heating is 50 times faster than that of electrical heating. The maximum conversion ratio of Fe2O3 by microwave heating is 24.5% higher than that by electrical heating. XRD results showed that the required temperature for Fe2O3 to completely convert into Fe3O4 by microwave heating is 200°C lower than that by electrical heating. Reaction kinetics parameters calculation results showed that the controlling step of microwave magnetizing is a phase boundary reaction of the contracted ball at 250–450°C with an apparent activation energy of 45 kJ/mol, whereas the controlling step of electrical magnetizing is a chemical reaction of stochastic coring at 450–650°C with an apparent activation energy of 225 kJ/mol.

Styrene–butadiene rubber (SBR) was reinforced with silica (SiO2) by co-coagulating process. This study investigated the SiO2 amount, stirring time and pH value affecting the SiO2 content, curing characteristics and mechanical properties of SBR. Results showed that SiO2 content and reinforcing behavior were greatly influenced by the amount of SiO2 and pH value. The torque, tensile strength and elongation at break were optimal when the mass fraction of SiO2 was 21.5 wt%, stirring time was 6 h and pH value was 6.57. The utilized efficiency of SiO2 decreased with the increasing amount of SiO2 but increased with the increasing stirring time. The optimum cure time decreased with the increasing amount of SiO2. Both tensile strength and elongation at break decreased with the increasing pH value. Scanning electron microscopy observations showed that the SiO2 nanoparticles were distributed evenly in the SBR.

The curing behavior of a difunctional epoxy resin/octa(aminopropyl)silsesquioxanes hybrid resin system using 4,4′′-diaminodiphenyl sulfone as curing agent was studied. Fourier transform infrared (FTIR) spectroscopy was used to evidence the formation of the hybrid resin and to monitor the curing process. Results showed that the reactivity of the hybrid resin system was slightly lower than that of the pristine epoxy resin. Differential scanning calorimetry was used to study the curing kinetics of the hybrid resin. The curing kinetics of the pristine and hybrid resins was analyzed by two methods: Kissinger and Flynn-Wall-Ozawa methods. The FTIR analysis accorded well with the results of the kinetics study. POLYM. COMPOS., 29:77–83, 2008. © 2007 Society of Plastics Engineers

The surfaces of poly-p-phenylene-2,6-benzobisthiazole (PBO) fibres have been modified by enzymatic treatment. The enzyme used was a peroxidase, present in the horseradish. The surface modification was performed using a peroxidase and hydrogen peroxide as catalyst and oxidizing agent. Catalytic mechanism of peroxidase was suggested. To evaluate the surface hydrophilicity, contact angle between fibres and glycol was determined. The results show that, the contact angle of the PBO fibre with glycol decreased. X-ray photoelectron spectroscopy (XPS) was also employed to show the binding of carbon atom on the surface of fibres, and results showed that a new type of carbon (carbon in the ester binding) appeared after the enzyme-catalyzed reaction taking place on the surface of PBO fibres. The chemical composition and morphology of PBO fibre surfaces were characterized by FTIR and scanning electron microscopy (SEM), respectively. Results show that this method has great potential in the surface modification of PBO fibre.

The thermodegradation kinetics of a hybrid inorganic–organic epoxy system formed by diglycidyl ether of bisphenol A, DGEBA/DDS, modified with octahedral oligomeric silsesquioxane, octa(aminopropylsilsesquioxane) was studied. The average activation energy of thermodegradation of this system was calculated by the integral method developed by Flynn–Wall–Ozawa (E = 105.01 kJ mol−1) and by Coats and Redfern method (E = 113.07 kJ mol−1). Lifetime and half-life time of the materials system were predicted using the kinetic parameters. The results obtained from the two methods accorded well with each other. POLYM. COMPOS., 28:755–761, 2007. © 2007 Society of Plastics Engineers

In this research, the surface of ultra high molecular weight polyethylene (UHMWPE) fiber was modified by high energy ultraviolet (UV) initiated grafting reactions and acrylamide groups were grafted onto UHMWPE chains. The initiating and grafting mechanism of the reactions was studied. Some important factors influencing the grafting effect, e.g. crystallinity of UHMWPE fiber, concentration of the initiating reagent, grafting time and the concentration of grafting monomer (acrylamide) were discussed. Fourier transform infrared (FTIR) was used to manifest the mechanism of the grafting reaction. Scanning electron microscopy (SEM) was used to show the morphology changing of the fiber surface. Single fiber pull-out strength and ILSS tests of the composite showed that acrylamide grafted onto the surface of the fiber could improve the interfacial adhesion between treated fibers and matrices.

Dicyanate ester containing dicyclopentadiene cycles and epoxy co-polymers were prepared by copolymerization between epoxy and dicyclopentadiene bisphenol cyanate esters (DCPDCE). Viscoelastic properties of the co-polymers were characterized by the technique of dynamic mechanical analysis (DMA), which indicated that the introduction of E51 in the co-polymers would effectively improve the toughness of DCPDCE, while the thermal dimensional stability would be weakened. Results from thermogravimetric analysis (TGA) are in good accordance with the Tg values from DMA curves. Mechanical testing of the cured co-polymers shows that E51 can improve the mechanical properties of the co-polymers while its usage is controlled among 5% to 15%.

Cyanate esters with excellent high-temperature properties and easy processing are well known as good resin materials used in aerospace and electrical industries, but the drawback of brittleness limits their usage. In this study, carboxyl-terminated liquid butadiene-acrylonitrile (CTBN) was introduced to improve the toughness of bisphenol A dicyanate resin (BADCy), a typical kind of the cyanate esters. Fourier transform infrared spectroscopy and differential scanning calorimetry were employed to investigate the effects of CTBN on the curing behavior of BADCy; the results indicate that the addition of CTBN has a great influence on the curing behavior of BADCy at lower temperatures, but little at higher temperatures. Data from the thermogravimetric analysis and heat deflection temperature analysis showed that the thermal properties of the modified systems were poorer than that of pristine BADCy resin. On the basis of the scanning electron micrographs of the modified systems, toughening mechanism of the systems was discussed. Mechanical and dielectric properties of the cured resins and glass fiber-reinforced composites were also studied. Modified systems exhibit attractive properties for the future applications in aerospace industries. POLYM. ENG. SCI. 46:581–587, 2006. © 2006 Society of Plastics Engineers.

The water-based polyacrylate microemulsion for ultrahigh molecular weight polyethylene (UHMWPE) fibers adhesive coating was synthesized by the emulsion polymerization of methyl methacrylate (MMA), butyl acrylate (BA), acrylic acid (AA), and hydroxyethyl acrylate (HEA) in the presence of a composite of sodium lauryl sulfate (SLS), OP-10, and n-octyl alcohol (NOA) as the emulsifier. The effects of the mass fraction of emulsifier and the reaction time on the properties of emulsion and its membrane were investigated. When m(BA) : m(MMA) : m(AA) : m(HEA) was 50 : 50 : 3 : 10 (wt ratio) and the mass fraction of emulsifier was 13 wt % and the reaction time was 3 h at 80°C, the latex particle diameter was 30 nm tested by transmission electron microscope (TEM). The Fourier transform infrared (FTIR) spectrometer and differential scanning calorimeter (DSC) were used to characterize the chemical structure and the glass transition temperature (Tg) of microemulsion membrane. The application results showed that this microemulsion was an ideal adhesive coating for UHMWPE fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006