Fly ash as a pre-filter material for the retention of lead ions

Clay liners have been widely used to contain toxic and hazardous waste materials. Clays absorb contaminant cations due to their exchange capacity. To improve the performance of the clay liner, fly ash, a waste material arising from the combustion of coal has been studied as a pre-filter material. In particular, the retention of lead by two different fly ashes was studied. The influence of pH on retention as well as leaching characteristics are also examined. The results obtained from the retention experiments by the permeameter method indicate that fly ash retains the lead ions through precipitation in the pores as well as onto the surface when the ambient pH value is more than 5.5, and through adsorption when the pH value is less than 5.5. It has been observed that fly ash did not release the retained lead ions when the pH value is between 3.5 and 10.0. Hence, the retention of lead ions by fly ash is likely to be permanent since the pH of most of the municipal landfill leachates are within 3.7 to 8.8. However, for highly acidic or alkaline leachates, the retained ions can get released.

Influence of pH on the retention of heavy metal ions by fly ash

Clay liners have been widely used to contain toxic and hazardous wastes. Clays adsorb the contaminant cations due to their exchange capacity. To improve the performance of the clay liner, fly ash, a waste material arising out of combustion of coal has been studied as a pre-filter material. The results indicate that fly ash has the potential to retain heavy metal ions. This study concerns the retention of zinc by fly ash. The influence of pH on retention as well as leaching characteristics are examined. The results obtained from the retention experiments by permeameter method indicate that fly ash retains the zinc ions through precipitation in the pores as well as onto the surface when the ambient pH value is more than 6.9, and only through adsorption when the pH value is less than 6.9. It has been observed that fly ash did not release the retained zinc ions when the pH value is between 3.5 and 10.0. Hence, the retention of zinc ions by fly ash is likely to be permanent since the pH of most of the landfill leachates are between 3.7 to 8.8.

Estimate of N2O release from pit-toilets

The use of pit-toilets has severely contaminated the groundwater with nitrate ions in Mulbagal town, Karnataka, India. This paper examines the potential of nitrate ions in the pit-toilet effluents to transform to N2O and to escape to atmosphere from 16 wards of Mulbagal town. Anaerobic conditions prevailing in the pit-toilet convert 25 % of the available N to ammonium ions. Only 3-33 % of ammonium ions transform to nitrate ions in the pit-toilet and escape with the effluent. During migration to aquifer, only 4.5 % of available nitrate concentration in the effluent transforms to N-2 and N2O gases in the 1.5-m-thick saturated zone underlying the pit-toilet; 36-55 % of the gases comprise N2O and the remainder of N-2. Further only 18 % of N2O formed escapes to atmosphere, while the remainder is retained in soil solution. Calculations show that 9.88 x 10(13) molecules of N2O/cm(2) would be cumulatively released from 16 wards of Mulbagal town, over an area of 4.9 km(2).

Spectroscopic investigations of manganese ions in microwave-prepared NaPO3-PbO glasses

The EPR spectra of microwave-prepared 70NaPO(3):30PbO glasses containing different weight percentages of manganese ions have been studied. The EPR spectra exhibit a well-resolved hyperfine pattern at g(eff) approximate to 2.0. Optical absorption, fluorescent emission and excitation spectra of the glasses have been examined. The absorption spectrum exhibits a peak near 500 nm and this has been attributed to the spin-allowed E-5(g) --> T-5(2g) transition of Mn3+ ions. The emission spectrum shows a band at 595 nm which has been assigned to the T-4(1g)(G) --> (6)A(1g)(S) spin-forbidden transition of Mn2+ ions in octahedral coordination. Concentration quenching of fluorescence was found to occur above 0.75 wt% of Mn2+ ions. The excitation spectra exhibit four bands characteristic of Mn2+ ions in octahedral coordination. From the observed band positions of the excitation spectra, the crystal field parameter D-q and the Racah interelectronic repulsion parameters, B and C have been calculated. A structural model is proposed based on the IR, Raman and MASNMR studies according to which Mn2+ ions are likely to occupy sites similar to Na+ ions in these glasses.

Surface chemical studies on mica and galena using dextrin

The interactions of dextrin with biotite mica and galena have been investigated through adsorption, flotation, and electrokinetic measurements. The adsorption densities of dextrin onto mica continuously increase with increase of pH, while those onto galena show a maximum at pH 11.5. It is observed that the adsorption density of dextrin onto galena is quite high compared to that on mica. Both the adsorption isotherms exhibit Langmuirian behavior. Electrokinetic measurements portray conformational rearrangements of macromolecules with the loading, resulting in a shift of the shear plane, further away from the interface. Dissolution experiments indicate release of the lattice metal ions from mica and galena. Coprecipitation tests confirm polymer-metal ion interaction in the bulk solution. Dextrin does not exhibit any depressant action toward mica, whereas, with galena, the flotation recovery is decreased with an increase in pH beyond 9, in the presence of dextrin, complementing the adsorption results. Differential flotation results on a synthetic mixture of mica and galena show that mica can be selectively separated from galena using dextrin as a depressant for galena above pH 10. Possible mechanisms of interaction between dextrin and mica/galena are discussed.

Soft-particle model analysis of effect of LPS on electrophoretic softness of Acidithiobacillus ferrooxidans grown in presence of different metal ions

The effect of Surface lipopolysaccharides (LPS) on the electrophoretic softness and fixed charge density in the ion-penetrable layer of Acidithiobacillus ferrooxidans cells grown in presence of copper or arsenic ions have been discussed, The electrophoretic mobility data were analyzed using the soft-particle electrophoresis theory. Cell surface potentials of all the strains based on soft-particle theory were lower than those estimated using the conventional Smoluchowski theory, Exposure to metal ions increased the Surface electrophoretic softness with decrease in the fixed charge density. Effect of cell surface lipopolysaccharides on the model parameters are investigated and discussed.

Co-2-Ions In A Low-Pressure Glow-Discharge Of Carbon-Dioxide

$CO_2^{-}$ ions have been detected in the gas phase and measured by a mass spectrometer with a flight time of 30 µs in the positive column of carbondioxide glow discharge.

EPR observation of phase transitions in calcium cadmium acetate hexahydrate: Using Mn2+ and Cu2+ ions as probe

Results of temperature dependence of EPR spectra of Mn2+ and Cu2+ ions doped calcium cadmium acetate hexahydrate (CaCd(CH3COO)4•6H2O) have been reported. The investigation has been carried out in the temperature range between room temperature ( 300 K) and liquid nitrogen temperature. A I-order phase transition at 146 ± 0.5 K has been confirmed. In addition a new II-order phase transition at 128 ± 1 K has been detected for the first time. There is evidence of large amplitude hindered rotations of CH3 groups which become frozen at 128 K. The incorporation of Cu2+ and Mn2+ probes at Ca2+ and Cd2+ sites respectively provide evidence that the phase transitions are caused by the molecular rearrangements of the common coordinating acetate groups between Ca2+ and Cd2+ sites. In contradiction to the previous reports of a change of symmetry from tetragonal to orthorhombic below 140 K, the symmetry of the host is concluded to remain tetragonal in all the three observed phases between room temperature and liquid nitrogen temperature.

Ions And Barriers in Electric Discharge

It is a well know that electrons and positive ions are responsible in the case of electric spark. Investigation have been undertaken in the high voltage laboratory to study the effect of injecting ions (both possitive and negative)into the spark gap.Also the effect of paper screens in blocking the ions being invetsigated.

05-ions in a low pressure glow discharge of oxygen

0:- ions have been detected and measured in a positive column of glow discharge in oxygen between 0.04 and 0.17 Torr. A suitable ion-molecule reaction has been proposed, which appears to be supported by the mass spectrometer measurements.

Ammonium ions prevent methylation of uridine to ribothymidine in Azotobacter vinelandii tRNA

It was shown that tRNA from Azotobacter vinelandii grown in the presence of ammonium chloride lacks ribothymidine while that grown in the absence of the ammonium salt contains this modified nucleoside. [32P]-Labelled tRNA from this organism grown in a medium containing the ammonium salt was digested with RNase T1 and the pseudouridinecontaining tetranucleotide, common to all tRNAs was isolated and analysed for the nucleoside replacing the ribothymidine. It was found to be uridine. Cells previously labelled with [32P]- phosphate in the ammonium salt medium were washed and incubated in the ammonium saltfree medium to test whether ribothymidine would be formed upon removal of the ammoniumions. Methylation of the uridine did not take place.

Noble Metal Ionic Catalysts

Because of growing environmental concerns and increasingly stringent regulations governing auto emissions, new more efficient exhaust catalysts are needed to reduce the amount of pollutants released from internal combustion engines. To accomplish this goal, the major pollutants in exhaust-CO, NOx, and unburned hydrocarbons-need to be fully converted to CO2, N-2, and H2O. Most exhaust catalysts contain nanocrystalline noble metals (Pt, Pd, Rh) dispersed on oxide supports such as Al2O3 or SiO2 promoted by CeO2. However, in conventional catalysts, only the surface atoms of the noble metal particles serve as adsorption sites, and even in 4-6 nm metal particles, only 1/4 to 1/5 of the total noble metal atoms are utilized for catalytic conversion. The complete dispersion of noble metals can be achieved only as ions within an oxide support. In this Account, we describe a novel solution to this dispersion problem: a new solution combustion method for synthesizing dispersed noble metal ionic catalysts. We have synthesized nanocrystalline, single-phase Ce1-xMxO2-delta and Ce1-x-yTiyMxO2-delta (M = Pt, Pd, Rh; x = 0,01-0.02, delta approximate to x, y = 0.15-0.25) oxides in fluorite structure, In these oxide catalysts, pt(2+), Pd2+, or Rh3+ ions are substituted only to the extent of 1-2% of Ce4+ ion. Lower-valent noble metal ion substitution in CeO2 creates oxygen vacancies. Reducing molecules (CO, H-2, NH3) are adsorbed onto electron-deficient noble metal ions, while oxidizing (02, NO) molecules are absorbed onto electron-rich oxide ion vacancy sites. The rates of CO and hydrocarbon oxidation and NOx reduction (with >80% N-2 selectivity) are 15-30 times higher in the presence of these ionic catalysts than when the same amount of noble metal loaded on an oxide support is used. Catalysts with palladium ion dispersed in CeO2 or Ce1-xTixO2 were far superior to Pt or Rh ionic catalysts. Therefore, we have demonstrated that the more expensive Pt and Rh metals are not necessary in exhaust catalysts. We have also grown these nanocrystalline ionic catalysts on ceramic cordierite and have reproduced the results we observed in powder material on the honeycomb catalytic converter. Oxygen in a CeO2 lattice is activated by the substitution of Ti ion, as well as noble metal ions. Because this substitution creates longer Ti-O and M-O bonds relative to the average Ce-O bond within the lattice, the materials facilitate high oxygen storage and release. The interaction among M-0/Mn+, Ce4+/Ce3+, and Ti4+/Ti3+ redox couples leads to the promoting action of CeO2, activation of lattice oxygen and high oxygen storage capacity, metal support interaction, and high rates of catalytic activity in exhaust catalysis.

Facile conversion of electron rich benzylic hydrocarbons to carbonyl compounds by peroxydisulphate and copper ions

A convenient method for the conversion of electron rich benzylic hydrocarbons to carbonyl compounds is reported.

A novel conformation of valinomycin in its barium complex

Knowledge of the molecular mechanisms involved in ionophore-mediated cation transport would be valuable for under-standing many essential functions of biological membranes1−3. Cations are transported in several stages, such as formation of the ionophore−cation complex, diffusion across the cell membrane and subsequent release of the cation. Several conformational rearrangements are involved in this process, and so a detailed understanding of all the conformational possibilities of the ionophore seems to be essential for elucidating the molecular mechanism of ion transport. We are carrying out spectroscopic and crystallographic studies to explore the possible conformational stages of ionophores by complexing them, in different solvents, with cations of various sizes and charges. We report here a novel conformation of the ionophore valinomycin in its barium complex. It can be described as an extended depsipeptide chain, without internal hydrogen bonds, wound in the form of an ellipse with the two barium ions located at the foci.