ABSTRACT
Plasticity is an essential property of clay that determines its suitability for water filtration. There are no published works on the plastic behavior of clays from the study locations. The plastic behavior of seven Nigerian clays was examined using plasticity indices and compressive stress parameters in relation to chemical compositions and moisture content. The objective is to determine plastic behavior of some Nigerian clays and their suitability in production of Expanded Clay Aggregates (ECA) for water filters. Compressive stresses and deformation parameters were determined experimentally and compared theoretically. Atterberg limits (D 4318) were used to determine the plasticity indices. Chemical compositions of the samples were examined with XRF and correlated with plasticity and mineral contents of the clays. The clays are aluminosilicates with SiO2/Al2O3 ratio of 1.61 to 3.03 and plastic indices of 8 to 49. Low plastic indices (8-11) and low compressive stresses parameters were observed for kaolinite clays (0.002 MPa) due to their low affinity for water while zeolite rich clays showed high plastic indices (46 and 49) for Obowo and Minna and sharp difference in their compressive stresses parameters (0.15 and 0.03 MPa) at optimum moisture contents of 57% and 53%, respectively. Despite varying moisture content, chemical and mineral compositions, all curves showed similar trends apart from kaolinites at 40% moisture content. Relationships exist among microstructural properties, chemical composition, moisture content, compressive strength, and plasticity indices of the clays. The plastic behaviors show they are suitable for development of ECA for water filters.
ABSTRACT
In this work, African maize cobs (AMC) were used as a rich biomass precursor to synthesize carbon material through a chemical activation process for application in electrochemical energy storage devices. The carbonization and activation were carried out with concentrated Sulphuric acid at three different temperatures of 600, 700 and 800 °C, respectively. The activated carbon exhibited excellent microporous and mesoporous structure with a specific surface area that ranges between 30 and 254 m2·g-1 as measured by BET analysis. The morphology and structure of the produced materials are analyzed through Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Boehm titration, X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. X-ray photoelectron spectroscopy indicates that a considerable amount of oxygen is present in the materials. The functional groups in the activated carbon enhanced the electrochemical performance and improved the material's double-layer capacitance. The carbonized composite activated at 700 °C exhibited excellent capacitance of 456 F g-1 at a specific current of 0.25 A g-1 in 6 M KOH electrolyte and showed excellent stability after 10,000 cycles. Besides being a low cost, the produced materials offer good stability and electrochemical properties, making them suitable for supercapacitor applications.
ABSTRACT
Seven Nigerian clays and clay minerals were characterized by multiple means with respect to their potential application in water purification and other industrial areas. The morphology was determined by means of SEM while chemical/mineral compositions were quantified using EDX, XPS and XRD. FT-IR and UV methods were employed to investigate the functional groups, inter alia the physical and chemical behaviours of adsorbed species. The stability in aqueous solution was determined by zeta potential measurements. The combined results revealed that the clays are mostly kaolin and illite, while clay minerals are predominantly gibbsite and quartz, although other clay-associated minerals and elements were also observed. Two out of the characterized samples will find suitable application in filter media production for water purification due to the possession of exchangeable cations and electrophoresis properties, while the others possess potential industrial applications for refractory linings, ceramics, medical, beauty and cosmetics products. This outcome implies a utilization increase in local content and a value addition to minerals in Nigeria. The results of the study are being used to design and facilitate expanded clay aggregate production to be used for the development of low-cost water filters to address the challenge of poor access to potable water in Africa and other developing continents.
