Assessment of Groundwater Quality in Areas Surrounding Thundulu Phosphate Mine, Phalombe District, Malawi

Water is one of the renewable resources essential for sustaining all forms of life and quality of drinking water is very fundamental for human health. Human activities such as mining act as sources of water contamination which consequently lead to ecological, environmental and health problems. To the best of our knowledge, no study has been conducted around the Thundulu Phosphate Mine to establish the quality of drinking water. In this regard, this study was carried out to evaluate the physico-chemical water quality parameters of areas surrounding the Thundulu Phosphate Mine in Phalombe District. Groundwater samples from the villages surrounding the Phosphate Mine were collected both during the wet and dry seasons for analysis of physico-chemical water quality parameters (pH, electrical conductivity, turbidity, nitrate, chloride, sulphate, fluoride, iron, calcium and magnesium). The study also investigated microbiological water characteristics mainly Escherichia coli and faecal coliforms. Results showed that pH, electrical conductivity, turbidity, nitrate, chloride, sulphate, phosphate, calcium and magnesium complied with the national and international standards set by Malawi Bureau of Standards (MBS) and World Health Organization (WHO). As regards to microbiological characteristics, it was revealed that water from three sources (B2, B3 and B4) was contaminated with Escherichia coli and faecal coliforms. Keywords:       Physico-chemical; Groundwater; Phalombe; Borehole; Electrical Conductivity; Turbidity; Phosphate

Groundwater quality assessment from Phalombe Plain, Malawi

In the present study, groundwater samples were collected from ten boreholes in the Phalombe plain, Southern Malawi. The main objective was to assess the suitability of the borehole water for human consumption. Physicochemical and bacteriological parameters of the groundwater samples were determined using standard methods. Results were compared to the World Health Organization (WHO) and Malawi Standard (MS) drinking water guidelines to assess suitability. All analyses for physicochemical parameters were within acceptable limits except for fluoride concentration levels which were above WHO recommended limit of 1.5 mg/L in twoboreholes (Lihaka Primary School, 2.9 mg/L and Phalombe T.C, 2.0 mg/L). Trace metal contamination was below detection limits with atomic absorption spectrometry. Feacal coliform units exceeding WHO tolerated limits of 0 cfu/100 mg/L were observed in five groundwater samples from Lihaka Primary School (11 cfu/100 mL), Migowi trading center (4 cfu/100 mL), Phalombe T.C (77 cfu/100 mL), Thetheleya Village (73 cfu/100 mL), and Mpasa T.D.C (102 cfu/100 mL) boreholes. It was concluded that not all the borehole water is safe for human consumption. The presence of feacal coliform in some boreholes is indicative of health risk to the inhabitants of the geographical location. The study recommends mobilization of onsite possible means of treatment of groundwater such as boiling and use of chlorination tablets so as to prevent possible adverse health effects.Keywords: Bacteriological, Borehole, Malawi, Phalombe Plain, Water quality, WHO/MS drinking water guideline

Proximate Composition, Mineral Composition and Phytic Acid in Three Common Malawian White Rice Grains

Rice is the second most important food crop in Malawi, after maize. Some studies have reported on losses of macro- and micronutrients in rice grains subjected to different polishing rates. In this study, the proximate composition, mineral contents and phytic acid profile of three white (i.e. polished) rice varieties in Malawi were investigated. Proximate composition was determined by adopting AOAC method. Mineral contents were determined using flame atomic absorption spectrophotometer and phytic acid determined using standard procedures. The results show that proximate composition for the three varieties were variable in the with ranges being 9.35-10.42%, 0.69-0.90%, 5.43-7.03%, 0.72-1.71%, 1.42-3.15%, 81.41-82.45% and 39.56-42.10%, for moisture, ash, crude protein, crude fat, crude fibre, carbohydrate and energy content, respectively. Significant amounts of minerals were present in all three rice varieties in the ranges: 5.19-7.81 mg/100g for calcium; 30.21-40.32 mg/100g for magnesium; 216-268 mg/100g for potassium; 0.33-0.58 mg/100g for manganese; 0.77-1.40 mg/100g for zinc; 0.26-0.47 mg/100g for copper; and .83-2.49 mg/100g for iron. Phytic acid ranged between 93.10 and 204.92 mg/100g in all the three rice varieties, whereas heavy metals such as lead, chromium and cadmium were not detected in all varieties. The results suggest that the white rice varieties could serve as an alternative source of food for humans and animals after quality processing. Keywords: Malawian White Rice Grains, Proximate Composition, Minerals, Nutrient Content, Phytic Acid

Levels and spatial distribution of heavy metals in Lake Chilwa Catchment, Southern Malawi

The aim of this study was to assess the levels and distribution of heavy metals in Lake Chilwa and its catchment, and to understand the associated level of pollution. Water and sediment samples were collected from the lake and main inflowing rivers. A total of 23 surface water samples were sampled and analysed for pH, EC, Cu, Cr, Zn, Cd, Pb, As and Hg. Conductivity and pH were measured on-site with a Hanna portable multi meter, while metals were analysed by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The pH was found within the alkaline range (7.87-10.13), while conductivity ranged from 97-390μS/cm. The following metals were detected in the water samples; Zn (6.24–1168.70 μg/L), Cu (BDL–47.83 μg/L), Pb (BDL–49.94 μg/L), Cr (0.22–33.05 μg/L), Ni (0.40–8.20 μg/L) and Cd (BDL–0.53 μg/L). Hg and As were not detected in all sampling locations. Strong positive correlations were observed between Cd and Pb (r = 0.70), Cu and Zn (r = 0.70), while Cd and Ni (r = 0.50), Pb and Ni (r = 0.41) showed mild correlations, suggesting similar sources of input. Sediments were sampled from 2 locations in the lake and the following metals were detected; Zn (66.13 mg/Kg), Pb (7.74 mg/Kg), Ni (35.39 mg/Kg), Cu (20.02 mg/Kg), Cr (54.81 mg/Kg) and As (1.0 mg/Kg). Mercury and arsenic were not detected from both sampling locations. The heavy metal pollution index ranged from 2.24 to 114.45. All points except Kachulu harbour had values far below the critical pollution index value of 100. The values observed were well below the tolerable limits recommended by the World Health Organisation (WHO) standard for potable water, except for Pb at Kachulu Bay (P19) which was above the limit. Concentrations of the metals in the rivers were low upstream and increased downstream. Highest values for most of the elements were observed from the lake. Though levels are low now, the persistent and cumulative properties of these elements would render them unsafe in the near future if proper controls are not enforced.Keywords: Heavy metals, Lake Chilwa, Water pollution, Water qualit

Nano-space confinement of pre-selective catalysts for hydroformylation of 1-octene

Ph.D. (Chemistry)Rhodium-catalyzed hydroformylation is one of the most important industrial processes for the production of linear and branch aldehydes. Aldehydes serve as intermediates in the production of various fine chemicals. Rh-based homogeneous catalysts for aldehydes production have demonstrated high yields and selectivity. Catalyst separation and recovery of expensive Rh-metal from reaction mixtures is a challenge to this process. With increasing industrial demand for highly selective processes, homogeneous catalysis could well be extensively employed if catalyst recovery from products and recyclability could be accomplished more efficiently and economically. The above problems justify the investigation of immobilized (heterogenized) catalysts by both academia and industry. This would solve the separation problem by making it possible to separate the catalyst from the reaction medium with simple filtration techniques and to regenerate the catalyst for reuse. Moreover, the ease of recovery of catalyst from products and reusability can minimize the impact of the process on the environment. Immobilization of metal complexes on solid supports is an effective approach to overcome the limitations of homogeneous catalysis. Support materials such as Mobil Composite Material (MCM-41) and Santa Barbara Amorphous type material (SBA-15) are attractive candidates for immobilizing metal complexes because of their high surface area, adjustable pore sizes, large pore volumes and high surface silanol groups. In the present work, mesoporous silica supports, MCM-41 and SBA-15 were synthesized. Rhodium(I) complex species, trans-aquacarbonyl bis(triphenylphosphine) [Rh(CO)(OH2)(PPh3)2]OTf and trans-aquacarbonyl bis{tris-(m-sulfonphenyl)-phosphine} [Rh(CO)(OH2)(TPPTS)2]OTf were synthesized as catalyst precursors and anchored onto the mesoporous MCM-41 and SBA-15 framework structure via an electrostatic method to form immobilized (heterogenized) catalysts. The support and catalyst were characterized using a range of solid-state techniques. Results showed that the structural integrity of the catalyst supports was maintained after immobilization. Results also revealed a strong interaction between rhodium complex species and the inner walls of the ordered mesoporous materials, thus leading to the formation of stable heterogenized catalysts. In addition, immobilized catalysts constrained the pores, thus leading to a confinement effect, which enhanced activity and regioselectivity in the hydroformylation process. Selected immobilized catalysts were..

Fabrication of polymer composites and their application towards removal of arsenic from water

M.Sc.Millions of inhabitants worldwide are exposed to arsenic contaminated drinking water as a result of natural and man-made processes. Arsenic especially its inorganic forms, arsenic (III) and arsenic (V) have negative effects on human health especially in developing countries. Therefore fabricating low cost and efficient adsorbents for arsenic (III) removal is of great importance. The aim of this study is to use magnetite (Fe3O4) as filler, incorporated into a polymer blend forming composites as adsorbents for arsenic (III) removal. This work presents the fabrication, characterization and application of Fe3O4-EVA/PCL composites for arsenic (III) removal from water. Fe3O4/Ethylene-vinyl acetate copolymer (EVA)/polyaniline (PANI) and Fe3O4/Ethylene-vinyl acetate copolymer (EVA)/polycaprolactone (PCL) nanocomposites have been successfully synthesized by melt blending technique using a laboratory mixer (Thermo Scientific Haake Rheomex OS). The composites were characterized using scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. Thermal analysis was done by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and mechanical properties using INSTRON 4443 mechanical Tester. Ability of [EVA (70%) PCL (15%) Fe3O4 (15%)] composites to adsorbed As(III) from water has been investigated through batch experiments. The maximum adsorption was 2.83 mg/g of As(III) ions at 26 ±1°C and pH 8.6. Adsorption data were fitted to Langmuir, Freundlich and Dubinin-Radushkevich isotherms. The process fits well with the Langmuir isotherm. As(III) obeyed pseudo-second order kinetics. The nanocomposites investigated in this study showed good potential for As(III) removal from contaminated water may be due to the dispersion of the magnetite nanoparticles into the polymer blend composites which increases the surface area for the adsorption

Synthesis and characterization of low-cost activated carbon prepared from Malawian baobab fruit shells by H3PO4 activation for removal of Cu(II) ions: equilibrium and kinetics studies

Abstract In this study, low-cost activated carbon (AC) prepared from baobab fruit shells by chemical activation using phosphoric acid was evaluated for the removal of Cu(II) ions from aqueous solution. The prepared activated carbon samples were characterized using N2-adsorption–desorption isotherms, SEM, FTIR, EDX and XRD analysis. The sample activated at 700 °C was chosen as our optimized sample because its physicochemical properties and BET results were similar to those of a commercial sample. The N2-adsorption–desorption results of the optimized sample revealed a BET surface area of 1089 m2/g, micropore volume of 0.3764 cm3/g, total pore volume of 0.4330 cm3/g and pore size of 1.45 nm. Operational parameters such as pH, initial copper concentration, contact time, adsorbent dosage and temperature were studied in a batch mode. Equilibrium data were obtained by testing the adsorption data using three different isotherm models: Langmuir, Freundlich and Dubinin–Radushkevish (D–R) models. It was found that the adsorption of copper correlated well with the Langmuir isotherm model with a maximum monolayer adsorption capacity of 3.0833 mg/g. The kinetics of the adsorption process was tested through pseudo-first-order and pseudo-second-order models. The pseudo-second-order kinetic model provided the best correlation for the experimental data studied. The adsorption followed chemisorption process. The study provided an effective use of baobab fruit shells as a valuable source of adsorbents for the removal of copper ions from aqueous solution. This study could add economic value to baobab fruit shells in Malawi, reduce disposal problems, and offer an economic source of AC to the AC users

Wastewater Clarification and Microbial Load Reduction Using Agro-Forestry and Agricultural Wastes

Five agro-wastes, namely: cassava peels, Irish potato peels, Jatropha curcas seeds, Moringa oleifera seeds and rice husks were investigated as plant-based coagulants for turbidity and microbial load removal from sewage wastewater. Moringa oleifera and Jatropha curcas seeds before usage were defatted with 95% ethanol and the active coagulating component was extracted with 1.0 M NaCl. For the other three agro-wastes, their ashes were evaluated for turbidity and microbial load removal. The ash was prepared through pyrolysis of the raw biomass at a temperature of 800 °C for 3 h. The effect of pH, coagulant dose, settling time on turbidity reduction was investigated using sewage wastewater with an initial turbidity of 464.11 ± 0.13 NTU. The microbial load removal of the coagulants was investigated using three media onto which 1 mL of treated wastewater was poured and streaks were made using sterile swabs and then incubated at 37 °C for 24 h. Jatropha curcas and rice husks ashes exhibited the maximum turbidity reduction of 97.0% and 95.0%, respectively at pH 2, whereas for Moringa oleifera, the highest turbidity removal (96.0%) was achieved between pH 6 and 10. Additionally, it was observed that the electrical conductivity and total dissolved solids of the clarified wastewater increased as the doses were increased for all coagulants due to inorganic salts contained in seeds. The microbial load understudy was successfully reduced in wastewater clarified with Jatropha curcas and rice husks ashes, contrary to Moringa oleifera that increased microbial load content. The raw biomass and ashes for cassava and Irish potato peels could not clarify sewage wastewater. The results from this study have demonstrated that plant-based materials used performed effectively in turbidity and bacteria removal from sewage wastewater. Keywords: Domestic Wastewater; Clarification; Agro-Wastes; Turbidity; Microbial Loa

Biodiesel production over ZnO/TiO₂ catalyst : effect of co-solvent, temperature and reaction time

The aim of this work was to produce biodiesel from waste vegetable oil over ZnO/TiO2 catalysts as well as investigating the effect of co-solvent (hexane), reaction temperature and time on waste vegetable oil conversion to biodiesel. Production of biodiesel from virgin oil is still a downfall in commercial processes due to high cost. Thus, the process of producing biodiesel from waste vegetable oil over a TiO2-supported ZnO catalyst was studied in the absence and the presence of hexane as co-solvent respectively. The conversion of waste vegetable oil was found to increase with temperature and reaction time. The highest conversion that has been achieved was 99.1% at a temperature of 200 °C after 15 min of reaction for the reaction using hexane as co-solvent. The use of hexane as co-solvent was found to increase the oil conversion at lower reaction temperature and no effect was observed at higher temperatures

Waste vegetable oils to biodiesel over Al₂O₃ –supported SnO₂ catalyst : effect of support pore size

The main aim of this study was to investigate the catalytic properties of Al₂O₃-supported SnO₂ for the conversion of waste vegetable oil into biodiesel. The effect of support pore size on waste oil conversion was investigated at 100 and 200 °C by using α-alumina (with larger pore size) and γ-alumina (with smaller pore size) respectively as support for SnO₂. The effect of pore-size on conversion was found to depend on the operating temperature. At low temperature, i.e. 100 °C, higher conversion for waste vegetable oil was measured on SnO₂ catalyst supported on α-Al₂O₃ than the catalyst supported by γ-Al₂O₃. This effect became less significant at 200 °C. It was also observed that the oil conversion increased with an increase in reaction temperature and reaction time