Effect of zeolite types LTX and LTA on physicochemical parameters of drinking water sample in Ghana, assisted by light transmission experiment

In this study, the effect of zeolite types LTX and LTA, assisted by laser light transmission experiment on the physico-chemical parameters of drinking water samples have been investigated. Water samples were collected from rivers, streams, and wells from Central and Volta regions of Ghana, and zeolite masses of 0.2 and 0.5 g were added to 100 ml portions of the samples in turn. Laser light intensities transmitted through the samples before and after zeolite addition were measured and recorded. The results obtained showed raw water turbidity of 33.8 NTU and treated water turbidity of 3.0 NTU (WHO recommends the limit of 5 NTU for drinking water); transmitted light intensity for the raw and treated water samples of 0.3122 AU and 0.3345 AU, respectively. Our results also showed that water turbidity highly correlates the transmitted light intensity, and water conductivity depends on dissolved metal concentrations and temperature

Defluorination of drinking water using surfactant modified zeolites

The prevalence of high concentrations of fluoride (i.e. > 1.5 mg/l) in groundwater in the Northernpart of Ghana especially around the Bongo communities has been an issue of concern.Owingto the arid nature of these localities, the inhabitants (who are mainly peasant farmers), relymore on groundwater sources for their drinking water. With the strenuous nature of their joband the warm weather conditions, the farmers generally consume more water, thus becomingmore vulnerable to dental and skeletal fluorosis. This study focused on the removal of fluoridefrom groundwater by employing surfactant modified zeolites (SMZ) synthesized using locallyavailable kaolin material as precursor. The zeolite synthesis involved calcination of kaolin, alkaline fusion and hydrothermal treatment. The final product was modified with 5g/L Hexadecyltrimethylammonium bromide (HDTMABr). The zeolite was characterised by Xray Diffraction(XRD), Energy Dispersive Xray (EDX) and Scanning Electron Microscopy (SEM) and the modified form employed in batch fluoride removal studies. The fluoride adsorption kinetics was studiedusing model water with varying initial fluoride concentration. From the EDX analysis, the synthesized zeolite NaLSX was found to comprise predominantly Oxygen (60%), Silicon (15%), and Aluminium (13%). The SEM showed the zeolite NaLSX crystals to be octahedrally shaped. The unmodified zeolite NaLSX was incapable of adsorbing fluoride ions but the surfactant modified zeolite adsorbed fluoride. The fluoride adsorption capacity of the modified zeolite was pH dependent and peaked at pH 6.0 – 7.0. Keywords: characterization, defluoridation, groundwater, surfactant, zeolite

Effect of crystallization time on the hydrothermal synthesis of zeolites from kaolin and bauxite

Kaolin and bauxite were used as alumina and silica sources to synthesize zeolites hydrothermally. The source mate-rials as well as the synthesized zeolites were characterized by X-ray diffraction (XRD) scanning electron microscopy (SEM), en-ergy dispersive x-ray analysis (EDX) and Fourier transformed infrared spectroscopy (FTIR). XRD spectra of the bauxite showed Gibbsite phase whereas that of kaolin gave 32.4 % quartz and 67.6 %. The main phases of zeolites obtained after hydrothermal crystallizations were zeolite types LTA, analcime and zeolite X. Longer crystallization time resulted in phase change of the zeo-lites into sodalite. Hence, natural raw materials such as bauxite and kaolin have the attractive features of providing the staring reagents for the synthesis of ultrapure synthetic zeolites

Characterisation and In Vitro Antimicrobial Activity of Biosynthetic Silver-loaded Bacterial Cellulose Hydrogels

Wounds that remain in the inflammatory phase for a prolonged period of time are likely to be colonised and infected by a range of commensal and pathogenic microorganisms. Treatment associated with these types of wounds mainly focuses on controlling infection and providing an optimum environment capable of facilitating re-epithelialisation, thus promoting wound healing. Hydrogels have attracted vast interest as moist wound-responsive dressing materials. In the current study, biosynthetic bacterial cellulose hydrogels synthesised by Gluconacetobacter xylinus and subsequently loaded with silver were characterised and investigated for their antimicrobial activity against two representative wound infecting pathogens, namely S. aureus and P. aeruginosa. Silver nitrate and silver zeolite provided the source of silver and loading parameters were optimised based on experimental findings. The results indicate that both AgNO3 and AgZ loaded biosynthetic hydrogels possess antimicrobial activity (p < .05) against both S. aureus and P. aeruginosa and may therefore be suitable for wound management applications

Parametric, equilibrium, and kinetic study of the removal of salt ions from Ghanaian seawater by adsorption onto zeolite X

Benue State University, Markudi, Nigeria; KNUST, Kumasi, Ghana; University of Wolverhampton, UK, The Royal Society Leverhulme “Award for Africa” grant in collaboration with KNUST in Ghana

Photochemical destruction of H2O2 and HCHO in snow

Attempts have been made to analyse H2O2 and HCHO conserved insurface snow and shallow firn cores in both polar regions regarding theirconcentrations in ancient atmospheres. However, recent fieldmeasurements at several polar locations have demonstrated that anactive photochemistry takes place in the top layers of the surface snowinfluencing not only trace gas concentrations in the boundary layerabove the snow, but also concentrations of several compounds presentin the snow. Since H2O2 and HCHO undergo effective photochemicaldestruction in the gas phase, it can be assumed that both can also bedestroyed if they are present in the surface snow. Here we reportresults of laboratory experiments performed to quantify thephotochemical destruction of H2O2 and HCHO in snow. In closedchambers artificial snow samples containing H2O2 and HCHO wereexposed to high radiation intensities in the UV and visible range. Aneffective decay of H2O2 and HCHO has been observed in allexperiments. Attempts are made to calculate decay rates for bothcompounds in natural surface snow layers. The significance of theseprocesses for the interpretation of H2O2 and HCHO concentrations innatural snow regarding ancient atmospheric concentrations is discussed

Mercury exchange in zeolites Na-A and Na-Y studied by classical molecular dynamics simulations and ion exchange experiments

Classical molecular dynamics simulations have been employed to study the exchange of Na+ for Hg2+ in zeolite Na-A, with a Si/Al ratio of 1, and zeolite Na-Y, with Si/Al ratios of 2 and 5, in dry and hydrated conditions within the temperature range 330 – 360 K, to understand factors underpinning the performance of zeolites for water decontamination. A classical forcefield based on DFT energies has been developed for the interaction between the Hg2+ ions and the zeolite O atoms. In terms of water diffusion, zeolite Na-A shows the lowest calculated diffusivity, followed by zeolite Na-Y (Si/Al=2) and Na-Y (Si/Al=5), as a consequence of differing pore dimensions and extra-framework ion loadings. In the absence of speciation anions, the Hg2+ ions are consistently adsorbed at the pore windows in both the LTA and FAU framework types. The reduced pore size of zeolite A leads to an average hydration number per Hg2+ ion of <1.0, whilst the wider pore aperture of zeolite Y exerts less steric hindrance, and thus the Hg2+ hydration number reaches values between 1.0 and 2.0 in zeolite Y. These observations might indicate that Hg2+ ions are more strongly immobilized in zeolite A than in zeolite Y. Preliminary measurements of mercury removal using these zeolites, as synthesised from bauxite and kaolin, seem to support these findings