In situ probing calcium carbonate formation by combining fast controlled precipitation method and small-angle X-ray scattering.

The initial stage of calcium carbonate nucleation and growth, found usually in "natural" precipitation conditions, is still not well understood. The calcium carbonate formation for moderate supersaturation level could be achieved by an original method called the fast controlled precipitation (FCP) method. FCP was coupled with SAXS (small-angle X-ray scattering) measurements to get insight into the nucleation and growth mechanisms of calcium carbonate particles in Ca(HCO3)2 aqueous solutions. Two size distributions of particles were observed. The particle size evolutions of these two distributions were obtained by analyzing the SAXS data. A nice agreement was obtained between the total volume fractions of CaCO3 obtained by SAXS analysis and by pH-resistivity curve modeling (from FCP tests).

Antimicrobial N-halamine polymers and coatings: a review of their synthesis, characterization, and applications.

Antimicrobial N-halamine polymers and coatings have been studied extensively over the past decade thanks to their numerous qualities such as effectiveness toward a broad spectrum of microorganisms, long-term stability, regenerability, safety to humans and environment and low cost. In this review, recent developments are described by emphasizing the synthesis of polymers and/or coatings having N-halamine moieties. Actually, three main approaches of preparation are given in detail: polymerization, generation by electrochemical route with proteins as monomers and grafting with precursor monomers. Identification and characterization of the formation of the N-halamine bonds (>N-X with X = Cl or Br or I) by physical techniques such as Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and by chemical reactions are described. In order to check the antimicrobial activity of the N-halamine compounds, bacterial tests are also described. Finally, some examples of application of these N-halamines in the water treatment, paints, healthcare equipment, and textile industries are presented and discussed.

Removal of algal blooms from freshwater by the coagulation-magnetic separation method.

This research investigated the feasibility of changing waste into useful materials for water treatment and proposed a coagulation-magnetic separation technique. This technique was rapid and highly effective for clearing up harmful algal blooms in freshwater and mitigating lake eutrophication. A magnetic coagulant was synthesized by compounding acid-modified fly ash with magnetite (Fe(3)O(4)). Its removal effects on algal cells and dissolved organics in water were studied. After mixing, coagulation, and magnetic separation, the flocs obtained from the magnet surface were examined by SEM. Treated samples were withdrawn for the content determination of chlorophyll-a, turbidity, chemical oxygen demand (COD), total nitrogen, and total phosphorus. More than 99 % of algal cells were removed within 5 min after the addition of magnetic coagulant at optimal loadings (200 mg L(-1)). The removal efficiencies of COD, total nitrogen, and phosphorus were 93, 91, and 94 %, respectively. The mechanism of algal removal explored preliminarily showed that the magnetic coagulant played multiple roles in mesoporous adsorption, netting and bridging, as well as high magnetic responsiveness to a magnetic field. The magnetic-coagulation separation method can rapidly and effectively remove algae from water bodies and greatly mitigate eutrophication of freshwater using a new magnetic coagulant. The method has good performance, is low cost, can turn waste into something valuable, and provides reference and directions for future pilot and production scale-ups.

Effectiveness of copper and zinc ions in preventing scaling of drinking water.

This paper investigates the effectiveness of copper and zinc ions an economical and environmentally friendly method for inhibiting the scaling of drinking water, using the method of rapid controlled precipitation (RCP). The results indicated that zinc ions and copper ions, at low concentrations, were highly efficient inhibitors in a 300 mL solution (calcium ion concentration of 126.5 mg/L). To produce an inhibition efficiency of 100% (in 70 min), the concentration of the copper ion was 0.9 mg/L and that of the zinc ion was 0.4 mg/L. The analysis by SEM and infrared absorption spectrometry showed that copper and zinc ions could affect the calcium carbonate germination and change the crystal morphology, which indicated that copper and zinc ions had participated in the composition of the crystal; however, the quantity of copper or zinc ion in the precipitate was so small that it was difficult to observe them.

Study of the scaling formation mechanism in recycling water.

To better understand the phenomenon of scaling of water that occurs in the cooling systems of nuclear power plants and thus to propose effective measures against scaling, the analysis of the scaling capacity of Salvetat mineral water and Seine river water was carried out in this study by the method of rapid controlled precipitation (RCP), which was used to estimate the scaling power of natural waters and to characterize the scaling formation mechanisms. The results showed that RCP allowed the establishment of thermodynamic conditions where the scaling was formed with a degree of oversaturation that much less than 40 in relation to a real-life scaling phenomenon. Some factors, such as the water composition, temperature, and initial presence or absence of calcium carbonate (CaCO3) nucleus, promoted or inhibited the precipitation of (CaCO3). In the water with a higher scaling potential, deposition on a copper surface did not occur or remained negligible because of the electrochemical reactions between the copper ions and water. The electrostatic treatment was quite good for delaying precipitation because it could affect the water's composition in an infinitesimal way.