ABSTRACT
Ceramic water filters (CWFs) are globally employed as a point-of-use water treatment technology. Although, there are no standards to regulate the use of these CWFs in developing countries, they are gaining acceptability for domestic water treatment. This study sought to assess and compare the efficiency of commercially available types of CWFs and to propose a consumer selection guide for the purchase and use of CWFs. The CWFs selected for the study were, Ball filter with activated carbon (BF + AC), Candle filter (CF), and Pot filter (PFcs) coated with colloidal silver. The elemental and mineral oxide composition of the selected CWFs were analysed with x-ray fluorescence method. Furthermore, the raw unfiltered water (from three different common sources), and the filtrates obtained with the CWFs were analysed for their physicochemical, metal ion removability, and microbial correction. The x-ray fluorescence analysis indicated that Al2O3 and SiO2 were the major mineral oxide compositions of the selected CWFs. These metal oxides were present in varying concentrations. The CWFs showed turbidity reduction of 74.28-99.40%, Mn and Fe reduction of 54.04-98.48% and 48.82-97.50% respectively. In addition, the total coliform reduction by the selected CWFs ranged from 2.31 to 76.97%. It was therefore observed from the results that, the efficiency of commercially available CWFs varied in the order BF + AC > CF > PFcs. BF + AC was the most efficient in both physicochemical and microbial correction of all water sources. CWF selection guide for consumers based on different sources of water which considered the physicochemical parameters, biological parameters and Water Quality Index was discussed. This has an implication for regulation and standardization of CWFs.
ABSTRACT
The removal of malachite green (MG) from aqueous solution using teak leaf litter powder (TLLP) was investigated. The process was influenced by initial concentration, pH and temperature of dye solution as well as TLLP dosage. Optimum removal of MG per gram of TLLP occurred at 2 g/L and at pH 6-8. Dubinin-Radushkevich and Freundlich isotherm models fit the batch adsorption data better than Langmuir isotherm. The monolayer capacity of TLLP was 333.33 mg/g at 293-313 K. The mean free energy of 7.07 kJ/mol implied physical adsorption. The pseudo-second order model fit the kinetic data better than the pseudo-first order model. Both intraparticle diffusion and film diffusion mechanisms jointly influenced the adsorption process but the latter was the rate-controlling step. Thermodynamic data indicated that the process was endothermic, spontaneous and feasible. Therefore, TLLP could be an important low-cost adsorbent for removal of MG from aqueous solution.
ABSTRACT
Low-cost teak leaf litter powder (TLLP) was prepared as possible substitute for activated carbon. The feasibility of using the adsorbent to remove eosin yellow (EY) dye from aqueous solution was investigated through equilibrium adsorption, kinetic and thermodynamic studies. The removal of dye from aqueous solution was feasible but influenced by temperature, pH, adsorbent dosage and contact time. Variation in the initial concentration of dye did not influence the equilibrium contact time. Optimum adsorption of dye occurred at low adsorbent dosages, alkaline pH and high temperatures. Langmuir isotherm model best fit the equilibrium adsorption data and the maximum monolayer capacity of the adsorbent was 31.64 mg g-1 at 303 K. The adsorption process was best described by pseudo-second order kinetic model at 303 K. Boundary layer diffusion played a key role in the adsorption process. The mechanism of uptake of EY by TLLP was controlled by both liquid film diffusion and intraparticle diffusion. The values of mean adsorption free energy, E (7.91 kJ mol-1), and standard enthalpy, ΔH° (+13.34 kJ mol-1), suggest physical adsorption. The adsorption process was endothermic and spontaneous. Teak leaf litter powder is a promising low-cost adsorbent for treating wastewaters containing eosin yellow.
