RESUMEN
The adsorption of a cationic dye, Methylene blue (MB), and a zwitterionic dye, 8-Hydroxyquinoline (8-HQ), onto zeolites synthesized from different clays has been investigated. The presence of certain metals and the Si/Al ratio of the parent clay has an overall effect on the type of zeolites produced. Zeolites LTA and FAU Y were obtained using the hydrothermal method. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) spectral analysis was used to study the adsorption phenomena of the adsorbates on the adsorbents. The adsorption profile of MB (Topological Polar Surface Area (TPSA) 43.9 Å2 and 8-HQ (TPSA 33.1 Å2) compared favourably with a Freundlich isotherm with R2 > 0.9 for all the zeolitic materials synthesized. Adsorption capacities of zeolite FAU was significantly different from zeolite LTA for MB removal. The higher adsorption capacity of zeolite FAU was attributed to geometric effects resulting in greater shrinkage in the inter lattice spacing of zeolite LTA leading to a reduction in surface area. Adsorption of the relatively smaller 8-HQ however, did not show significant difference in the two zeolite types. Surface and structural characterization showed that adsorbates/adsorbents interactions were driven by both geometric (inter lattice spacing which imparts higher surface area of the adsorbent) and electronic (electrostatic repulsions through electron back donation from metals in the zeolitic structure) considerations.
RESUMEN
Development of sustainable technology to treat domestic wastewater with added advantages of cost reduction and improved handling efficiency is crucial in developing countries. This is because, domestic wastewater from households are stored in septic tanks and are poorly treated prior discharge. This study developed a macrophyte-assisted vermifiltration (MAV) system to treat domestic wastewater. The MAV system is an integrated approach of macrophytes and earthworms in a vermifiltration and complex physicochemical mechanism processes. The use of different macrophyte and earthworm species was hypothesized by the study to affect and vary the treatment performance of the developed MAV. The study therefore aimed to evaluate the treatment performance of the developed MAV when three varied macrophyte species (Eichhornia crassopes, Pistia stratiotes and Spirodela sp.) and two varied earthworm species (Eisenia fetida and Eudrilus eugeniae) were used to design the treatment system. Treated effluents were collected every 48hours within two weeks for physico-chemical, pathogen and helminth analysis. The contaminants (Ntot, NH3, NO3-N and Ptot) in the wastewater were high (>50 mgL-1, >5 mgL-1, >1 mgL-1 and >20 mgL-1 respectively). Results revealed that the developed MAV systems were effective in the removal of solids (>60%), nutrients (>60%) and pathogens (>90%). In most cases, there were no significant differences between the selected varied macrophytes and earthworms in the treatment performances. Results therefore demonstrated that the selected macrophytes combined with the earthworm species were suitable when used in the development of the MAV system. Developing the MAV with the selected varied macrophyte and earthworm species did not only contribute to the treatment of the wastewater, but also improved the vermiculture. Eudrilus eugeniae however demonstrated higher biomass gain (5-10% more) compared to Eisenia fetida.
