Browsing by Author "Mwakabona, Hezron"

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The influence of stereochemistry of the active compounds on fluoride adsorption efficiency of the plant biomass
(Science Publishing Group, 2014-08-20) Mwakabona, Hezron; Machunda, Revocatus; Njau, Karoli
Several studies have reported various defluoridation capabilities of plant biomasses. The resultant variations in fluoride removal capacities are associated with the presence of different types of active functional groups in the respective biomasses. This study reports of the fluoride removal efficiencies of sisal leaf biomass in comparison. Comparison with other plant biomasses were made and hence the fluoride removal efficiencies of maize leaf (ML), goose grass (GG), banana false stem (BFS), Aloe vera (AV), untreated sisal fibre (USF) and sisal pith (SP) with similar active functional groups but different stereochemistry and solubility of the active compounds are reported. A portion of 0.5 g of each biomass was mixed with a 10 mg/l fluoride solution in a 10 ml portions under the same experimental conditions. The maximum fluoride removal capacity of sisal fibre biomass was found to be 26.6 %. By comparison, the fluoride removal efficiencies of ML, GG, BFS, AV, USF and SP were found to be, 4.1, 4.6, 7.1, 26.6, 29.4 and 47.3 % respectively. This suggests that, stereochemistry and solubility of the active compounds have a significant role to play in water defluoridation by plant biomasses, and thus, knowledge of the stereochemistry and solubility of the active compounds in plant biomass is very important to fully unlock biomass’ defluoridation potentials.
Making Fe0-Based Filters a Universal Solution for Safe Drinking Water Provision
(MDPI, 2017-07-12) Naseri, Elham; Ndé-Tchoupé, Arnaud; Mwakabona, Hezron; Nanseu-Njiki, Charles; Noubactep, Péguy; Njau, Karoli; Wydra, Kerstin
Metallic iron (Fe0)-based filtration systems have the potential to significantly contribute to the achievement of the United Nations (UN) Sustainable Development Goals (SDGs) of substantially improving the human condition by 2030 through the provision of clean water. Recent knowledge on Fe0-based safe drinking water filters is addressed herein. They are categorized into two types: Household and community filters. Design criteria are recalled and operational details are given. Scientists are invited to co-develop knowledge enabling the exploitation of the great potential of Fe0 filters for sustainable safe drinking water provision (and sanitation).
Metallic iron for safe drinking water provision: Considering a lost knowledge
(Pergamon, 2017-06-15) Mwakabona, Hezron; Ndé-Tchoupé, Arnaud; Njau, Karoli; Noubactep, Chicgoua; Wydra, Kerstin
Around year 1890, the technology of using metallic iron (Fe0) for safe drinking water provision was already established in Europe. The science and technology to manufacture suitable Fe0 materials were known and further developed in this period. Scientists had then developed skills to (i) explore the suitability of individual Fe0 materials (e.g. iron filling, sponge iron) for selected applications, and (ii) establish treatment processes for households and water treatment plants. The recent (1990) discovery of Fe0 as reactive agent for environmental remediation and water treatment has not yet considered this ancient knowledge. In the present work, some key aspects of the ancient knowledge are presented together with some contemporised interpretations, in an attempt to demonstrate the scientific truth contained therein. It appears that the ancient knowledge is an independent validation of the scientific concept that in water treatment (Fe0/H2O system) Fe0 materials are generators of contaminant collectors.
Metallic iron for water treatment: leaving the valley of confusion
(Springer, 2017-07-31) Makota, Susanne; Nde-Tchoupe, Arnaud; Mwakabona, Hezron; Noubactep, Chicgoua; Nassi, Achille; Njau, Karoli; Mwakabona, Hezron
Researchers on metallic iron (Fe0) for environmental remediation and water treatment are walking in a valley of confusion for 25 years. This valley is characterized by the propagation of different beliefs that have resulted from a partial analysis of the Fe0/H2O system as (1) a reductive chemical reaction was considered an electrochemical one and (2) the mass balance of iron has not been really addressed. The partial analysis in turn has been undermining the scientific method while discouraging any real critical argumentation. This communication re-establishes the complex nature of the Fe0/H2O system while recalling that, finally, proper system analysis and chemical thermodynamics are the most confident ways to solve any conflicting situation in Fe0 environmental remediation.
Plant biomasses for defluoridation appropriateness : unlocking their potentials
(Research Journal in Engineering and Applied Sciences, 2014) Mwakabona, Hezron; Said, Mateso; Machunda, Revocatus; Njau, Karoli
Fluoride and fluorosis are endemic to many countries including Tanzania. Performances of different materials for use in water defluoridation systems have been reported. Some of these materials are; alum, oxides and hydroxide of metals, activated carbon, bone char and plant biomasses. This paper reviews and discusses the performances of selected defluoridation materials such as alum in Nalgonda technique, the oxides and hydroxides of metals (inorganic adsorbents) in ion exchange/adsorption, activated carbon, bone char and plant biomasses in ion exchange/adsorption. More discussion is on the strengths and limitations of these materials in removing fluoride from water. Furthermore, it describes a new approach that will likely enhance the fluoride removal capacity when plant biomasses are used, which involves special arrangement of different plant biomasses in a column. This promises to be of low cost and high performance and thus suitable for both urban and rural communities in developing countries.
Water defluoridation by Fe (III)-loaded sisal fibre: Understanding the influence of the preparation pathways on biosorbents’ defluoridation properties
(Elsevier, 2019-01-15) Mwakabona, Hezron; Mlay, Hilda; Van der Bruggen, Bart; Njau, Karoli
Defluoridation properties of two Fe(III)-loaded plant biomass (Fe(III)-activated sisal fibre (Fe(III)-ASF) and post-alkalized Fe(III)-ASF (PA-Fe(III)-ASF)) distinguished by preparation pathways through exclusion/inclusion of post-alkalization are presented, with the aim of understanding the influence of post-alkalization in the preparation pathway to their fluoride removal properties. Findings reveal that PA-Fe(III)-ASF shows higher chemical stability with removal efficiency increasing towards acidic conditions, whereas Fe(III)-ASF manifests a lower chemical stability with removal efficiency increasing (in a wider pH range) with the increase in pH. This is attributable to the nature of the interactions between Fe(III) and the biomass surface functional groups. The removal efficiency by PA-Fe(III)-ASF has a strong positive correlation (0.98) to the surface charge/speciation induced by pH and the reverse is true for the Fe(III)-ASF. These findings therefore suggest that the principal fluoride removal mechanism is electrostatic interactions and ligand exchange for PA-Fe(III)-ASF and Fe(III)-ASF, respectively. Therefore, inclusion/exclusion of post-alkalization in preparation steps is an important aspect to consider in the production of Fe(III)-loaded biosorbents for water defluoridation for acquisition of specific defluoridation properties.