Loss Of Hydrophilicity Research Articles

A clean separation process using pretreatment-flotation for refractory mixed concentrates

• A new pretreatment-flotation separation method for galena and chalcopyrite was developed. • The modification mechanism of S 2- conversion to SO 4 2- on galena surface was revealed. • Separation test results of Cu-Pb sulfide mixed concentrate validates the theoretical analysis. In this paper, a clean separation technique of galena and chalcopyrite that innovatively combined a sulfuric acid pretreatment with collector-free flotation was proposed. X-ray diffraction (XRD) analysis, Scanning Electron Microscopy (SEM) determination, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) measurement, and flotation experiments were carried out to research on the surface differentiation of galena and chalcopyrite with sulfuric acid and the effect on their flotation performance. XRD analysis showed that significant characteristic peaks of a new species of lead sulfate (PbSO 4 ) were formed in galena after sulfuric acid pretreatment, while chalcopyrite was not affected at all. SEM analysis and floatability results confirmed the effect of sulfuric acid on selective oxidation of galena surface. ToF-SIMS results further provided strong evidence for the conversion of sulfur ions to sulfate ions on galena surface. Lead sulfate species formed on the pretreated galena were detected at a thickness of 0–80 nm, which led to its loss of hydrophilicity and floatability. The experimental results of pretreatment-flotation separation of galena-chalcopyrite mixture and copper-lead sulfide mixed concentrate were in good agreement with the theoretical analysis. The results showed that the new method could effectively and thoroughly separate lead sulfide from copper sulfide ore, and the sulfuric acid in this technology could be recycled in the periodic pretreatment process. This work can enrich the surface inhibition theory of galena by sulfuric acid and provide an effective way for the separation of lead-copper sulfide ore.

Hydrophobic recovery of femtosecond laser processed silicone rubber insulator surfaces

AbstractThis article demonstrates the loss and recovery in hydrophobicity of silicone rubber insulator surface processed by a femtosecond laser. The two stages of the wettability conversion were investigated. First, a rough micro/nano structure was formed on the original hydrophobic sample surface processed by the femtosecond laser, and the water contact angle on the surface was reduced from ~ 110° to a minimum of ~ 35°. This hydrophilicity loss was due to the increase in the hydrophilic OH groups and the reduction of the hydrophobic CH3 groups on the surfaces. Second, the roughened samples were stored in a natural ambient environment. Over a certain storage time, the surface hydrophobicity recovered gradually and evolved into a superhydrophobic state. It was found that the migration of low molecular weight cycle and/or linear siloxane oligomers resulted in the recovery of the hydrophobicity property. Coupled with the increase of surface roughness caused by laser irradiation, the further evolution of the hydrophobicity was promoted. Moreover, the higher temperature accelerates the recovery of the surface hydrophobicity. The research on the conversion mechanism of the wettability on the silicone rubber insulator surface processed by femtosecond laser is of great significance for improving its reliability in practical applications.

Novel Post-Treatment Approaches to Tailor the Pore Size of PS-b-PHEMA Isoporous Membranes.

Using the example of an integral-asymmetric isoporous membrane prepared from polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA), physical and chemical ways of post-treatment are introduced with the aim to tailor the pore size. These post-treatments are i) thermal annealing and ii) urethane chemistry of ethyl isocyanate (EI) in the presence of perfluoro(methyl cyclohexane). Via these approaches, the pore size of PS-b-PHEMA membranes is successfully tailored in the range of 10-20 nm with narrow pore size distribution by controlling the duration of thermal annealing and chemical reaction, respectively. The excellent hydrophilicity of the PS-b-PHEMA membrane is not changed by thermal annealing. The chemical postmodification using EI is associated with a loss of hydrophilicity with increasing conversion.

Application of Eh–pH Diagram for Activation of Depressed Chalcopyrite in Cyanidation Tailings

ABSTRACTPotential–pH diagrams for a chalcopyrite–xanthate–H2O and chalcopyrite–NaCN–H2O systems at 298 K were constructed to predict depressing components in the flotation of depressed chalcopyrite in cyanidation tailings using xanthate as a collector. Sodium hypochlorite, hydrogen peroxide, and copper sulfate were used as activators to reduce this depression effect, and the potential–pH diagram for the activator–H2O system was constructed to predict the thermodynamic activating ability. and were dominant in the acidic-to-alkaline region. In alkaline solution, the generation potentials of and were lower than that of CuX. Therefore, they are the main depressing components that influence the flotation of chalcopyrite in cyanidation tailings. In the alkaline region, the oxidative potentials of sodium hypochlorite, hydrogen peroxide, and copper sulfate were significantly higher than that of CN–, so CN– was easily oxidized. This resulted in activation through the loss of hydrophilicity.

Gamma ray treatment enhances bioactivity and osseointegration capability of titanium

The time-dependent degradation of titanium bioactivity (i.e., the biological aging of titanium) has been reported in previous studies. This phenomenon is caused by the loss of hydrophilicity and the inevitable occurrence of progressive contamination of titanium surfaces by hydrocarbons. In this study, we tested the hypothesis that gamma ray treatment, owing to its high energy to decompose and remove organic contaminants, enhances the bioactivity and osteoconductivity of titanium. Titanium disks were acid-etched and stored for 4 weeks. Rat bone marrow-derived osteoblasts (BMOs) were cultured on titanium disks with or without gamma ray treatment (30 kGy) immediately before experiments. The cell density at day 2 increased by 50% on gamma-treated surfaces, which reflected the 25% higher rate of cell proliferation. Osteoblasts on gamma-treated surfaces showed 30% higher alkaline phosphatase activity at day 5 and 60% higher calcium deposition at day 20. The strength of in vivo bone-implant integration increased by 40% at the early healing stage of week 2 for gamma-treated implants. Gamma ray-treated surfaces regained hydrophilicity and showed a lower percentage of carbon (35%) as opposed to 48% on untreated aged surfaces. The data indicated that gamma ray pretreatment of titanium substantially enhances its bioactivity and osteoconductivity, in association with the significant reduction in surface carbon and the recovery of hydrophilicity. The results suggest that gamma ray treatment could be an effective surface enhancement technology to overcome biological aging of titanium and improve the biological properties of titanium implants.

Amphiphilic Properties of Hydrotropes Derived from Isosorbide: Endo/Exo Isomeric Effects and Temperature Dependence

The hydrotropic properties of short-chain monoalkyl ethers of isosorbide have been studied with emphasis on the difference between the two regioisomers (2-O- and 5-O-monoalkylisosorbide, C(i)Iso-exo and C(i)Iso-endo, respectively). On the one hand, the partitioning in a water/cyclohexane system has been measured, and on the other hand, the "optimal formulation" of C(i)Iso/oil/water systems has been determined by changing the oil polarity. In both cases, whatever the alkyl chain length (four or five carbons), C(i)Iso-exo appears to be less hydrophilic due to an intramolecular hydrogen bond that makes the free hydroxyl group less available. With one substituted position, the hydrophilicity contribution of isosorbide is slightly higher than the one of two ethylene glycols when the exo hydroxyl remains free, whereas it is closer to one ethylene glycol when this hydroxyl is substituted. With regard to the sensitivity to temperature, the hydrophilicity loss on heating seems to be similar for both isomers and close to what is obtained for poly(ethylene glycol) derivatives if we consider the evolution of the partition coefficients. In C(i)Iso-endo/oil/water systems, however, the variation of the optimal oil with temperature tends to show that the isosorbide derivatives are approximately 2 times less sensitive than their poly(ethylene glycol) counterparts to temperature changes.

Angle‐Resolved XPS Study of Plasma‐Deposited Polystyrene Films after Oxygen Plasma Treatment

AbstractPlasma oxidation of plasma deposited polystyrene (pPS) films was performed in an inductively coupled plasma reactor. Reconstruction of the oxygen concentration depth profiles based on angle‐resolved XPS data showed that two competitive mechanisms (functionalization and etching) happened during the oxygen plasma treatment. Static water contact angle measurements confirmed this result. Oxidized pPS films were also not stable with time; a loss of hydrophilicity was observed and reorganization of the topmost functionalized surface occurred involving diffusion of oxygen groups from the surface towards the bulk and re‐contamination by reaction of trapped radicals with hydrocarbon molecules present in ambient air.magnified image

Reason for the loss of hydrophilicity of TiO2 film and its photocatalytic regeneration

Reason for the loss of hydrophilicity of TiO2 film and its photocatalytic regeneration