Enos W. Wambu

Fluoride adsorption onto an acid treated lateritic mineral from Kenya: Equilibrium studies

Adsorption of fluoride (F) ions from water using acid treated lateritic mineral (LM-1) from Kenya was studied by batch experiments. The effect of acid-treatment of adsorbent and change in temperature, mass of LM-1, pH and selected competing ions was evaluated. The adsorption process was strongly influenced by temperature, pH and adsorbent dosage. The percentage F removal increased the presence of the nitrate and the chlorate ions but decreased the presence of sulphates, chloride and phosphate ions. Adsorption isotherms were classified according to Giles’ classification and the adsorption data validated using Langmuir and Freundlich isotherms. The data correlated to both the Langmuir and Freundlich isotherms although the data fit to the Freundlich model was somehow better. This showed that F adsorption onto LM-1 followed a mixed adsorption mechanism in which physisorption reactions involving intra-particle diffusion of F into mesoporous sites in LM-1 became increasingly important at higher concentrations and temperatures whereas ion-exchange mechanism involving surface OH- appear to dominate at low surface coverage in more alkaline conditions. With maximum adsorption capacity of 10.5 mg/g, LM-1 could be used to remove F water. Key words: Equilibrium analysis, fluoride adsorption, Langmuir and Freundlich isotherms, Lateritic mineral adsorbent, low-cost adsorbents.

Removal of Cr(III) from aqueous solutions using a micaceous poly–mineral from Kenya

Adsorption of Cr(III) ions from aqueous solutions using a micaceous polymineral (MPM) from Kenya was studied using batch experiments as function of contact time, adsorbent dosage, Cr(III) concentration, pH and temperature. Chromium adsorption was found to be a fast process taking place in less than 20 min to reach equilibrium. Near complete removal of the metal was realized at Cr(III) concentrations of 200 mg/L, using 0.15 g/ml adsorbent doses at pH range of 4 to 6 and 25 to 40°C. Equilibrium and kinetics analysis indicated that Cr(III) adsorption onto MPM progresses through an inner-sphere surface complexation of the hydrolysis products of Cr(III) with surface sites in the adsorbent mineral. The adsorption process could be described by the Lagergren pseudo-second order kinetics model and the adsorption equilibrium was found to conform to H–type according to Giles classification of adsorption isotherms. The adsorption data could therefore be validated by Langmuir model. The adsorption capacity of 7.9 mg/g showed that this low-cost material could be used for the scavenging Cr(III) from aqueous streams.

Socio-economic factors influencing the spread of drinking water diseases in rural Africa: case study of Bondo sub-county, Kenya

Socio-economic and medical information on Bondo sub-county community was studied to help establish the relationship between the water quality challenges, community health and water rights conditions. Health challenges have been linked to water quality and household income. A total of 1,510 households/respondents were studied by means of a questionnaire. About 69% of the households have no access to treated water. Although 92% of the respondents appear to be aware that treatment of water prevents waterborne diseases, the lowest income group and children share a high burden of waterborne diseases requiring hospitalization and causing mortality. Open defecation (12.3%) in these study areas contributes to a high incidence of waterborne diseases. The communitys constitutional rights to quality water in adequate quantities are greatly infringed. The source of low-quality water is not a significant determinant of waterborne disease. The differences in poverty level in the sub-county are statistically insignificant and contribute less than other factors. Increased investment in water provision across regions, improved sanitation and availability of affordable point-of-use water purification systems will have major positive impacts on the health and economic well-being of the community.