Many water districts have recently shifted from free chlorine (in the form of HOCl/OCl-) to monochloramine (NH2-Cl) as a disinfectant for drinking water to lower the concentration of chlorinated hydrocarbon byproducts in the water. There is concern that the use of NH2Cl disinfectant may lead to higher Pb levels in drinking water. In this study, the electrochemical quartz crystal microbalance is used to compare the effects of these two disinfectants on the dissolution of Pb films. A 0.5 microm thick Pb film nearly completely dissolves in a NH2Cl solution, but it is passivated in a HOCl/OCl- solution. X-ray diffraction analysis shows that the NH2Cl oxidizes Pb to Pb(II) species such as Pb3-(OH)2(CO3)2, whereas the stronger oxidant, HOCl/OCl-, oxidizes Pb to Pb(IV) as an insoluble PbO2 conversion coating. Although NH2Cl may produce less halogenated organic byproducts than HOCl/OCl- when used as a disinfectant, it may lead to increased Pb levels in drinking water.

Chiral films of CuO were electrochemically deposited onto achiral Au(001) using chiral precursors such as tartaric acid and the amino acids alanine and valine to complex the Cu(II). The chirality of the electrodeposited films was dictated by the chiral solution precursor. X-ray diffraction pole figures and azimuthal scans, in conjunction with stereographic projections, were used to determine the absolute configuration and enantiomeric excess of the chiral CuO films. CuO films grown from l-tartaric acid have a (11̄1̄) orientation with an enantiomeric excess of 95%, while the films grown from d-tartaric acid have a (1̄11) orientation with an enantiomeric excess of 93%. CuO films grown from chiral amino acids have two types of chiral orientations, each showing lower enantiomeric excess compared with the films deposited from tartaric acid. The films grown from l-alanine and l-valine solution have an excess of the (1̄11) and (1̄1̄1̄) orientations, while the films grown from d-alanine and d-valine have an excess of (11̄1̄) and (111). Films of CuO deposited from a solution of achiral glycine consist of a racemic mixture of the (1̄11) and (11̄1̄) orientations. Chiral CuO films deposited on both single-crystal Au(001) and polycrystalline Au films were shown to exhibit chiral recognition for the electrochemical oxidation of tartaric acid.

The commonly used disinfectants in drinking water are free chlorine (in the form of HOCl/OCl-) and monochloramine (NH2Cl). While free chlorine reacts with natural organic matter in water to produce chlorinated hydrocarbon byproducts, there is also concern that NH2Cl may react with Pbto produce soluble Pb(II) products--leading to elevated Pb levels in drinking water. In this study, electrochemical methods are used to compare the thermodynamics and kinetics of the reduction of these two disinfectants. The standard reduction potential for NH2Cl/Cl- was estimated to be +1.45 V in acidic media and +0.74 V in alkaline media versus NHE using thermodynamic cycles. The kinetics of electroreduction of the two disinfectants was studied using an Au rotating disk electrode. The exchange current densities estimated from Koutecky-Levich plots were 8.2 x 10(-5) and 4.1 x 10(-5) A/cm2, and by low overpotential experiments were 7.5 +/- 0.3 x 10(-5) and 3.7 +/- 0.4 x 10(-5) A/cm2 for free chlorine and NH2Cl, respectively. The rate constantforthe electrochemical reduction of free chlorine at equilibrium is approximately twice as large as that for the reduction of NH2Cl. Equilibrium potential measurements show that free chlorine will oxidize Pb to PbO2 above pH 1.7, whereas NH2Cl will oxidize Pb to PbO2 only above about pH 9.5, if the total dissolved inorganic carbon (DIC) is 18 ppm. Hence, NH2Cl is not capable of producing a passivating PbO2 layer on Pb, and could lead to elevated levels of dissolved Pb in drinking water.

Epitaxial nanodisks of tin(II) sulfide (SnS) are deposited electrochemically on a [100]-oriented singlecrystal Au substrate from an acidic solution at 70 °C. The SnS grows with two different out-of-plane orientations of [100] and [301], which each have four equivalent in-plane orientations. X-ray pole figures reveal the following epitaxial relationships: SnS(100)[010]//Au(100)[010], SnS(100)[010]//Au(100)[01 j 0], SnS(100)[010]//Au(100)[001], SnS(100)[010]//Au(100)[001 j ], SnS(301)[010]//Au(100)[010], SnS(301)[010]// Au(100)[01 j 0], SnS(301)[010]//Au(100)[001], and SnS(301)[010]//Au(100)[001 j ]. For the SnS[100]orientation, the in-plane mismatch is -2.4% in the [010] direction and 6.1% in the [001] direction. For the [301] orientation, the in-plane mismatch is -2.4% in the [010] direction and alternates between 3.4% and 6.7% in the [103 j ] direction. The SnS deposits with a disklike morphology with a diameter of 300 nm and a thickness of 50 nm.

Geopolymer has been developed as an alternative material to Portland cement. Geopolymer is based on the polymerization of alkaline activation and oxide of silicon and aluminium. These oxides can be found in many pozzolanic materials such as metakaolin and the wastes from industries and agricultures in Thailand, e.g., fly ash, bagasse ash and rice husk ash.Pozzolanic materials were selected as source materials for making geopolymers into 4 different types. Sodium hydroxide concentration of 10 Molar (10MNaOH) and sodium silicate (Na 2 SiO 3 ) solutions were used as alkaline activators by the mass ratio of Na 2 SiO 3 /NaOH at 1.5. The mixtures were cast in 25×25×25 mm. cubes. After casting, the geopolymers were cured at 80 ๐ C for 24 hrs. in an oven and then at room temperature for 7 days. The pozzolanic materials effects, the Si/Al molar ratio and the Na/Al molar ratio were studied and characterized.An X-ray fluorescence (XRF) was chosen to determine the percentages of silica and alumina in order to verify the proper ratio of the fly ash, Rice husk ash, Bagasse ash and Metakaolin.The study also included the impact on mechanical and physical properties such as compressive strength, water absorption, density and porosity. 1.IntroductionGeopolmer was first originated by Davidovits (1979) to designate a new class of three dimensional silico-aluminate materials [1]. The geopolymer is produced by totally replacing the ordinary Portland cement. Hence, the use of geopolymer concrete to replace the cement is to reduce the CO 2 emissions by the cement industries [2]. Geopolymerization can be applied to utilize solid wastes and by-products containing silica and alumina which are called 'Pozzolans'. A geopolymer is environmentally friendly [3] which is attractive to increase attention in various research fields as a construction material [4]. Pozzolans from industrial and agricultural by-products such as fly ash, bagasse ash and rice husk ash were used to produce geopolymers in this research.An industrial by-product, from power plants, which is now being used quite extensively as a pozzolan for replacing cement is fly ash. Bagasse ash is a by-product from sugar refinery whereas rice husk is a by-product from rice mill. When they are burnt both bagasse ash and rice husk ash contain around 80% of silica, silica in amorphous form suitable for use as a pozzolan [5]. Furthermore, the geopolymerization can be reacted with metakaolin, obtained by burning kaolin from Ranong province in Thailand, normally, at temperature higher than 600°C [6].The main alkali solutions activated with pozzolans were sodium silicate and sodium hydroxide. In this research, the fly ash, bagasse ash, rice husk ash and metakaolin were used as the starting materials. They were studied the effects of pozzolanic materials, the Si/Al molar ratio, the Na/Al molar ratio and Na/Si molar ratio for mechanical and physical properties such as compressive strength, water absorption, density and porosity.