Effects of calcium competition on lead sorption by palm kernel fibre

The kinetics of sorption of a mono-solute of lead ions and of a bi-solute of lead and calcium ions onto palm kernel fibre was investigated in a batch system. The experimental data were analysed based on an intraparticle diffusion equation and a pseudo-second-order mechanism, in both the mono- and bi-solute sorption systems, in order to predict the rate constant of sorption, the equilibrium capacity, and the initial sorption rate. The results indicate that the sorption mechanism is described by a pseudo-second-order equation. Intraparticle diffusion was significant in the lower-concentration systems. In addition, a modified intraparticle diffusion equation was applied to the sorption systems.     

Phytostabilisation of arsenical gold mine tailings using four Eucalyptus species: growth, arsenic uptake and availability after five years

Arsenic (As) contamination is a worldwide problem. Where arsenic is highly concentrated and confined within a limited area, such as in many mine tailings facilities, phytostabilisation is an attractive technology for long-term remediation. Important characteristics of a plant to be useful for phytostabilisation include As tolerance and low levels of As accumulation, as well as the ability to limit As availability. Performance needs to be monitored over the long term to ensure an ongoing vegetation community, though this is rarely done. In this study, the suitability of four Eucalyptus species (E. cladocalyx, E. melliodora, E. polybractea, E. viridis) for the phytostabilisation of arsenical, sulphidic gold mine tailings was assessed after five years. All four species accumulated low As concentrations, the highest being recorded in mature leaves, ranging from 0.29 to 5.14 microg g(-1) As. E. polybractea had significantly higher foliar As than the other three species but there was also great variation within the species. Between 5-10 times lower concentrations were recorded in stem samples and no As was detected in young leaf tips. There was also significant variation in the growth of trees upon the site. Eucalyptus cladocalyx grew significantly taller than other species although greater variation was detected within the species than between. The variation in tree heights was not correlated with As concentrations in either stems or leaves. Arsenic availability was determined to depths of 2.2 m and found to be low when compared to total As in the tailings. Importantly, no effect of trees on As availability or soil pH was detected. We conclude that E. cladocalyx, in particular is an ideal candidate for the long-term phytostabilisation of As-contaminated land and mine tailings. The variation detected in both As accumulation and growth is also promising for the selection of desirable traits.     

Selective heterogeneously catalyzed hydrogenations

A number of catalytic hydrogenations have been discussed with emphasis on reaction selectivity. These reactions were examples of chemoselectivity, regioselectivity, stereoselectivity, diastereoselectivity and enantioselectivity. Factors such as catalyst selection, reaction conditions and the steric nature of the substrate were discussed in terms of their contribution to the selectivity of particular hydrogenations.     

Studies on the Light Stability of Flordipine Tablets in Amber Blister Packaging Material

Accelerated light conditions have been used in the evaluation of light stability of flordipine tablets. The tablets were subjected to exaggerated light exposure in a fadeometer and to 150 foot candles of fluorescent light in a light cabinet. A comparative study was conducted between tile tablets exposed directly to light and to those covered with amber vinyl sheeting. The color change was evaluated by a tristimulus colorimeter using the Hunter L, a, b scale. The b coordinate was selected for the final evaluation of light stability since it corresponded closely to the visual increase in yellowness with time. The data demonstrated that the amber colored vinyl sheeting had an excellent protective effect on the discoloration of flordipine tablets. Data obtained in the fadeometer in six hours as well as results from exposure in the light cabinet for twenty-nine days, facilitate the comparative evaluation of light stability of flordipine tablets. One hour's exposure to fade oneter was found to be equal to 480 hours in fluorescent light     

Some recent developments in the homogeneous catalyzed hydrogenation of olefins

It has been found that the amount of double bond isomerization accompanying homogeneous olefin hydrogenations over tris (triphenylphosphinechlororhodium is markedly influenced both by the duration of hydrogen presaturation of the catalyst and the presence of oxygen in the reaction mixture. These results are compared to those obtained over a heterogeneous catalyst, 5% rhodium on chareoal. One of 10 papers to be published from the Symposium “Hydrogenation”, presented at the AOCS Meeting, New Orleans, April 1970.     

Relationship Between Stress, Interaction and the Mechanical Properties of Some Pigmented Tablet Coating Films

The mechanical properties of pigmented free films of hydroxypropyl methylcellulose in combination with either polyvinyl alcohol or polyethylene glycol 1000 and cast from aqueous systems, were measured using a stress-strain method. The pigments incorporated were two types of talc (differing in average particle size) and two types of titanium dioxide (one of which was surface-treated). Specific surface area data for the pigments and the pH of the aqueous solution or suspension of the film components were determined in order to understand the factors affecting the mechanical properties of pigmented films.     

Organic Functional Group Hydrogenation

The utility of catalytic hydrogenation in the synthesis of organic compounds is evident from the number of monographs on the subject published in recent years [l-41. Unlike other synthetically useful reactions, however, the conditions used for a given hydrogenation are generally chosen on the basis of an empirical correlation and not on a knowledge of the mechanism of the reaction. One reason for this is that most of the mechanistic studies made on catalytic hydrogenation do not readily lend themselves to extrapolation to synthetic ally useful reactions.     

O2 and N2O activation by Bi-, Tri-, and tetranuclear Cu clusters in biology

Copper-cluster sites in biology exhibit unique spectroscopic features reflecting exchange coupling between oxidized Cu's and e (-) delocalization in mixed valent sites. These novel electronic structures play critical roles in O 2 binding and activation for electrophilic aromatic attack and H-atom abstraction, the 4e (-)/4H (+) reduction of O 2 to H 2O, and in the 2e (-)/2H (+) reduction of N 2O. These electronic structure/reactivity correlations are summarized below.     

Hydroxyl terminated PEEK-toughened epoxy–amino novolac phthalonitrile blends – Synthesis,cure studies and adhesive properties

Self cure promoting, amine-containing novolac–phthalonitrile (APN) resins of varying compositions were synthesized and characterized. APN possessing amine functionalities reduced the cure initiation temperature from 310 °C (typical of pure phthalonitrile systems) to 180 °C. It showed excellent thermal stability up to 420 °C and high char residue of 77–79 %. Co-reaction of APN with diglicydyl ether of bisphenol A (DGEBA) led to a decrement in their thermal stability though improved their adhesive properties. Evidences were obtained for epoxy–amine, epoxy–phthalonitrile and amine–phthalonitrile reactions. The latter reactions led to formation of oxazoline, triazine and phthalocyanine groups in the network. These were rationalized by density functional theory studies on model compounds. The extents of epoxy–amine and epoxy–phthaonitrile reactions were quantified. Introduction of hydroxyl terminated poly ether ether ketone (PEEK) reduced the brittleness of the blends and improved their lap shear strength. Toughening of epoxy–amino novolac phthalonitrile networks occurred through phase separation of PEEK segments in cured matrix.