Charles O. Onindo

Oxime analogs of amino acids and peptides are efficient ligands for NiII ions

Abstract Oxime derivatives of amino acids, amides, and peptides are very efficient ligands for NiII ions forming very stable water-soluble complexes. Oxime of amino acids amides forms octahedral and square-planar complexes with the same 4N coordination mode. The spectroscopic and X-ray diffraction studies indicate an unusual role for the hydrogen bond in NiH−1L2 species, which stabilizes the cis coordination of two ligands in a planar complex. Oxime analogs of natural amino acid can be much more efficient ligands than the parent molecules.

Fluoride adsorption onto an acid treated lateritic mineral from Kenya: Equilibrium studies

Adsorption of fluoride (F) ions from water using acid treated lateritic mineral (LM-1) from Kenya was studied by batch experiments. The effect of acid-treatment of adsorbent and change in temperature, mass of LM-1, pH and selected competing ions was evaluated. The adsorption process was strongly influenced by temperature, pH and adsorbent dosage. The percentage F removal increased the presence of the nitrate and the chlorate ions but decreased the presence of sulphates, chloride and phosphate ions. Adsorption isotherms were classified according to Giles’ classification and the adsorption data validated using Langmuir and Freundlich isotherms. The data correlated to both the Langmuir and Freundlich isotherms although the data fit to the Freundlich model was somehow better. This showed that F adsorption onto LM-1 followed a mixed adsorption mechanism in which physisorption reactions involving intra-particle diffusion of F into mesoporous sites in LM-1 became increasingly important at higher concentrations and temperatures whereas ion-exchange mechanism involving surface OH- appear to dominate at low surface coverage in more alkaline conditions. With maximum adsorption capacity of 10.5 mg/g, LM-1 could be used to remove F water. Key words: Equilibrium analysis, fluoride adsorption, Langmuir and Freundlich isotherms, Lateritic mineral adsorbent, low-cost adsorbents.

Alum treated grey water for toilet flushing, mopping and laundry work

The paper presents the study carried out in a peri urban settlement of Nairobi Kenya and involved treatment of raw grey water generated from bathroom, kitchen and laundry for flushing toilet and laundry work. The study utilized both chemical and physical treatment. The chemical treatment involved alum addition in the raw grey water and pH adjustment using bicarbonate salts. The physical treatment involved filtration using Quartz sand and filtration of pH adjusted treated grey water using filter paper. The major ions studied were ions which could interfere with lathering of soaps or could cause stains on clothes and toilet fixtures or could be potentially health hazardous. These ions were Fe, Mn, Ca, Mg, Pb and Hg. The levels of these ions in raw grey water and in treated grey water were determined using atomic absorption spectroscopy. The results for the levels of these ions before treatment were compared to the set standards for potable water by Kenya Bureau of Standards [1]. The levels of these ions in the treated grey water after adjusting the pH were found to be within the Maximum Contaminant Limits (MCL) set by KEBS [1]. Thus the overall treatment of the raw grey water produced water of good quality which complied with the set standards for potable water by KEBS [1]. The results of this treatment could contribute immensely in the fulfillment of the millennium development goals.

Preparation and Characterization of Pd Modified TiO2 Nanofiber Catalyst for Carbon–Carbon Coupling Heck Reaction

TiO2 fibers were prepared through electrospinning of poly methyl methacrylate (PMMA) and titanium isopropoxide (TIP) solution followed by calcination of fibers in air at 500°C. Cetyltrimethylammonium bromide (CTAB) protected palladium nanoparticles (Pd NPs) prepared through reduction method were successfully adsorbed on the TiO2 nanofibers (NF). Combined studies of X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) indicated that the synthesized Pd/TiO2 had anatase. BET indicated that the synthesized TiO2 and Pd/TiO2 had a surface area of 53.4 and 43.4 m2/g, respectively. The activity and selectivity of 1 mol% Pd/TiO2 in the Heck reaction have been investigated towards the Mizoroki-Heck carbon–carbon cross-coupling of bromobenzene (ArBr) and styrene. Temperature, time, solvent, and base were optimized and catalyst was recycled thrice. 1H NMR and 13C NMR indicated that stilbene, a known compound from literature, was obtained in various Heck reactions at temperatures between 100°C and 140°C but the recyclability was limited due to some palladium leaching and catalyst poisoning which probably arose from some residual carbon from the polymer. The catalyst was found to be highly active under air atmosphere with reaction temperatures up to 140°C. Optimized reaction condition resulted in 89.7% conversions with a TON of 1993.4 and TOF value of 332.2 hr−1.