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This work aimed to study the feasibility of using iron-contaminated graphite as an adsorbent for As(V) removal from water. The adsorbent was prepared by grinding graphite concentrate with steel ball. The study was performed through the measurements of adsorption capacity, BET surface area and XPS analysis. The experimental results showed that the iron-contaminated graphite exhibited significantly high adsorption capacity of As(V). The higher the iron contaminated on the graphite surface, the higher the adsorption capacity of As(V) on the material obtained. It was suggested that the ion-contaminated graphite was a good adsorbent for As(V) removal. [ABSTRACT FROM AUTHOR]

This study investigated the preparation of graphene oxide from mildly oxidized graphite through ultrasonic exfoliation. Both the original and produced materials were analyzed by ultraviolet-visible spectrophotometer, X-ray diffraction and atomic force microscopy. The results indicated that the exfoliation yield of graphene oxide was proportional to the input ultrasonic energy. In addition, a two-stage exfoliation phenomenon was observed in the exfoliation of mildly oxidized graphite with both ultrasonic homogenizer and cleaner. It also was found that increasing the content of [] in a C-H2SO4-[] reaction system was the most simple and direct method to increase the oxidation degree of graphite oxide. [ABSTRACT FROM AUTHOR]

Adsorption is widely applied to remove arsenic from water. This paper reviewed and compared the recent progresses on the arsenic removal by adsorption using two-dimensional and three-dimensional graphene-based materials as adsorbents. Functional graphene sheet achieved the largest As(III) adsorption capacity of 138.79mg/g, while Mg-Al LDH/GO2 showed the largest As(V) adsorption capacity of 183.11mg/g. Parameters including pH, temperature, co-existing ions and loaded metal or metal oxide affected the adsorption process. The adsorption mechanisms of graphene-based materials for As(III) and As(V) could be explained by surface complexation and the electrostatic attraction, respectively. Future works are suggested to focus on regenerating of two-dimensional graphene-based adsorbents and developing the three-dimensional with large specific surface area and better adsorption performance. [ABSTRACT FROM AUTHOR]

In this work, a novel method to determine the point of zero net proton charge (PZNPC) of colloidal kaolinite in aqueous solutions was presented through the measurement of zeta potential of the particles in various concentrations of NaCl solution and the mathematic regression of the zeta potential versus pH curves. This method is based on the observation that there are two common intersection points (CIP) in the two curves of zeta potential versus pH of colloidal kaolinite with a low and a high NaCl concentration. The observation might be attributed to that NaCl would compress the electric double layer of kaolinite particles and affect the efficiency of the protonation/deprotonation of the HD-faces. The experimental result showed that the PZNPC of kaolinite is 5.37. [ABSTRACT FROM AUTHOR]

The crystallization of calcium carbonate (3) in soil controlled by natural organic material was considered a very important reason to enhance the property of ancient Chinese organic Sanhetu (COS), but how the organic material affected the crystallization of 3 in COS is still unclear. In this paper, a natural organic material (sticky rice, SR) and a synthetic organic material (anionic polyacrylamide, APAM) were selected as additives to investigate their effect on the crystallization of 3. The experimental results showed that the morphology and size of 3 crystals could be affected by the concentration of additives and reaction time, while only the size of 3 crystals could be affected by the concentration of reactant. Although the morphology and size of 3 crystals varied greatly with the variation of additive concentration, reactant concentration and reaction time, the polymorph of 3 crystals were always calcite, according to SEM/EDX, XRD and FTIR analyses. This study may help us to better understand the mechanism of the influence of organic materials on 3 crystallization and properties of COS. [ABSTRACT FROM AUTHOR]

pillared interlayered clays (-PILCs) were synthesized through a novel method, in which nanoparticles were formed in montmorillonite interlayers. In this method, silver ions were first exchanged into montmorillonite interlayers, and then reduced into nanoparticles by trisodium citrate at 100°C in aqueous solutions. The synthesized @montmorillonite nanocomposite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its surface area was evaluated by using Brunauer-Emmet-Teller (BET) method. Compared to traditional PILCs synthesized through ion exchange method, the formed -PILCs had better thermal stability and stronger structure because their pillars are nanoparticles. Furthermore, this method introduces a possibility to control the size of the pillars and thus the pore size of the PILCs, due to that the nanoparticle pillars can be modified on their forms and diameters in the synthesizing process. Also, it was found that the intercalating nanoparticle pillars were formed at restricted pH values and silver ion concentrations. The TEM image of the Ag@montmorillonite composite synthesized in montmorillonite dispersions showed that there were many nanoparticles, identified as Ag nanoparticles by EDX, with the size of 2 to 20 nm, are observed on montmorillonite. These Ag nanoparticles had an analogous globular shape, which indicates the growth of the silver nanoparticles was on the montmorillonite surface, or was restricted by the montmorillonite interlayer space alone. [ABSTRACT FROM AUTHOR]

Hydrophobic agglomeration is originated from the hydrophobic attraction between particles, which is essentially different from electrolyte coagulation and polymer flocculation. It is applied to mineral processing in floc-flotation process to improve the recovery of mineral fines. In this paper, the applications of this phenomenon in mineral fines were summarized, including the origin of hydrophobic agglomeration, the main factors affect hydrophobic agglomeration (particle hydrophobicity, shear rate and duration, nonpolar oil and tank geometry), as well as hydrophobic agglomeration based separation processes (carrier flotation and floc-flotation). [ABSTRACT FROM AUTHOR]

Exfoliated silicate minerals have attracted great attentions because of the dramatic improvement in properties. This paper highlights the preparation of exfoliated silicate minerals, including physical, chemical, mixed physical and chemical methods. The mechanisms by which silicates are exfoliated and the important influential factors are also summarized. Finally, the instrumental techniques to characterize the exfoliated structure and exfoliation degree are presented. [ABSTRACT FROM AUTHOR]

The decomposition of goethite and goethite/siderite concentrates into hematite with thermal modification was studied through the measurements of X-ray diffraction (XRD), scanning electronic microscope (SEM) and thermal gravimetric analysis (TGA). The experimental results showed that goethite decomposed into hematite directly at around 300°C without any intermediate phase and the decomposition of siderite completed at 500°C. Nanoscale granular structures were observed in the thermally treated products. It deserves highlighting that the decomposition processes proceeded from surfaces into bulks. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a recently developed electrosorption technology for deionization using porous electrodes. The electrode materials play an important role in the efficiency. This paper highlights the current research status of carbon-based materials as the electrode and the adsorption models in the CDI. It includes the types and performances of carbon-based materials and the main influencing factors of the desalination characteristics. Also, operating parameters such as charging voltage, flow rate, concentration of feed solution, treating time and temperature are summarized. [ABSTRACT FROM AUTHOR]

Electrokinetic property of various minerals in aqueous solutions has been studied through electroacoustic measurement in the present work. This study was carried out on the particles of calcite (CaCO3), magnetite (Fe3O4), quartz (SiO2), and galena (PbS) in an aqueous NaCl solution. Electrophoretic measurement was also applied to magnetite and quartz particles for the comparison of the two methods. The experimental results have shown that the point of zero charges (PZCs) of calcite, magnetite, and galena were at pH 12.5, 3.8 and 2.8, respectively, while no PZC for quartz appeared in the pH range of 1.5–11. The electroacoustic and electrophoretic measurements have obtained the same PZC and similar curves of zeta potential vs pH for magnetite and quartz particles in aqueous solutions. In addition, it has been found that a specific adsorption of Na+ cation was applied to magnetite surfaces in aqueous solutions if the electrolyte (NaCl) concentration in the solution is high enough, leading the isoelectric point to shift rightward. This observation might be more remarkable in electroacoustic measurement than electrophoretic measurement. [ABSTRACT FROM AUTHOR]

The formation of a minimum ice unit (MIU) and ice crystal is simulated. The simulation indicates that an MIU is made up of 10 H2O molecules, and the MIU shows a four-hexagon cage structure. On the basis of simulation, we can calculate that 1 mol ice crystal contains 2 mol hydrogen bonds, and 16.67% hydrogen bonds should be broken during water fusion at 0°C. A total of 12.5% hydrogen bonds should be broken when 1 mol water is heated from 0°C to 100°C, and 70.83% hydrogen bonds should be broken when 1 mol water is vaporized into steam at 100°C. A total of 8.33% volume contract during water fusion at 0°C can also be calculated according to the MIU simulation in this paper. [ABSTRACT FROM AUTHOR]

In this work, a Ti-pillared montmorillonite with high thermal stability has been prepared by using a Na-montmorillonite as the host clay and polyhydroxy-titania ions as the pillaring precursor. The formation of Ti-pillared montmorillonite has been confirmed from the characterizations through X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric–differential scanning calorimeter, and specific surface area analyses. In the preparation of Ti-pillared montmorillonite several parameters, such as the type of solvent in which the synthesis is realized, the ratio of polyhydroxy-titania ions and montmorillonite, the intercalation time, the calcining temperature, and calcining time, were tested to understand their effects on the basal spacing. It was shown that this method could produce a Ti-pillared montmorillonite with the basal spacing of 3.74 nm, specific surface area of 409 m2/g, and mean pore size of 2.94 nm, as well as a high thermal stability up to 900°C. [ABSTRACT FROM AUTHOR]

We present an experimental technique to determine the thickness of hydration layers on solid surfaces in aqueous solutions by using an atomic force microscope (AFM). This technique is based on the phenomenon where a small line bending in the AFM force–distance plot of hydrated solid surface in aqueous solutions, may be due to the existence of hydration layers on the tip and the solid surface. The thickness of hydration layers on mica plate immersed in water and NaCl solutions were determined with this technique. [ABSTRACT FROM AUTHOR]

The regeneration mechanism of ion-exchange resins in the electrodeionization process has been studied with theoretical and experimental investigation. Theoretically, contact forms of resins and membranes can be divided into 4 types, and the possible places of water-splitting are located at the contact faces of different types resins and membranes, for example, cation ion-exchange resins contact with anion ion-exchange resins or membranes, anion ion-exchange resins contact with cation ion-exchange resins and membranes, according to the theoretical calculation. And the exhausted ion-exchange resins can be regenerated by the electrodeionization process with the regeneration efficiency at 70–80% in this work. [ABSTRACT FROM AUTHOR]