Journal Articles

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Defluoridation of water supplies using coconut shells activated carbon: batch studies
(International Journal Of Science And Research (IJSR), 2014) Said, Mateso; Machunda, Revocatus L.
Drinking water with elevated fluoride levels results in serious irreparable health problem that has attained an alarming dimension all over the world, Tanzania being one of the affected countries; techniques have been under study for years. Batch experiments were carried out to determine the effect of various adsorbent factors such as adsorbent dose, initial pH, particle size and contact time on adsorption process. Adsorption efficiency was observed to increase with decrease in particle size, the highest efficiency recorded was 68.2 and 65.9% for field and synthetic water respectively when particle size less than 150µ of coconut shells activated carbon were used. Adsorption was observed to be favoured by pH in acidic range and the maximum efficiency of 58.4% was recorded at pH of 2.0 and particle sizes between 4.18-2.36mm. The pH of the effluent was lowered to acidic range which necessitates further treatment of the effluent or coupling with other materials for pH elevation before use. Adsorption increases with adsorbent dose hence at a smaller influent concentration; the required standard of 1.5mg-F- /l can be met. Equilibrium isotherms have been analysed using Langmuir and Freundlich isotherm models, and both of the models fit to explain the adsorption behaviour of fluoride ions onto Coconut shell activated carbons, during this study it was established that when properly activated; coconut shells can be appropriate for use household filters that could be cost effective in rural areas of Tanzania due its local availability and its colour adsorption property
Effectiveness of activated groundnut shells to remove chromium from tannery wastewater
(Science Publishing Group, 2016) Mwegoha, W. J. S.; Lema, M. W. J.
This paper presents results of the investigation of Chromium III removal from tannery wastewater using groundnut shells under laboratory scale batch experiments. The effects of pH, contact time, particle size and dosage of the adsorbent on the adsorption of Cr (III) were studied. Determination of Chromium ion concentration in the wastewater was done using Atomic Absorption Spectrophotometer (AAS). Results show that removal mechanism is dominantly adsorption, which is dependent of the physical and chemical characteristics of the material. The main constituent of groundnut shell is carbon, potentially making it suitable for making activated carbon for adsorption experiments. From the initial concentration of 6.643 ppm, optimum Cr (III) removal was obtained at pH of 4, particle size of 0.25mm, contact time of 180 minutes and adsorbent dosage of 20g, with highest efficiency of 98.013%, corresponding to final concentration of 0.132ppm. The adsorption process was found to obey the Freundlich adsorption isotherm with R2 being 0.9613. Overall, the adsorption capacity of the activated groundnut shell was found to be 2.6172mg/g which ensures that they can be used for the removal of Chromium III from tannery wastewater.
Enhancement of agrosoil cd2+ immobilization efficiency through incubation with bamboo sawdust/rice husk biochar blends: the effect of carbonization temperature and blending ratio
(2023) Kwikima, Muhajir Mussa; Chebude, Yonas; Meshesha, Beteley Tekola
Thermal modification of blended feedstocks has recently gained popularity, due to its importance in improving biochar yield and features, such as pore structure and adding extra functional groups than pristine ones and thus improving adsorption effectiveness against a range of pollutants. In this study, the biochar made up of blended bamboo sawdust and rice husk has been investigated on its effectiveness on Cd2+ sorption processes controlling the accessibility and mobility of this metal in agro-soil. In a set of batch experiments, the effect of a 10% w/w biochar (carbonized at 400°C and 700°C) to soil ratio at various blending ratios (1:1, 1:3, and 3:1) on the adsorption and desorption characteristics of Cd2+ in agricultural clay soil incubated for 60 days was investigated. The adsorption kinetics and isotherms were also studied to examine adsorption mechanism at pH of 8, initial solute concentration 200 mg/L, ionic strength of 0.01 M (NaNO3), Contact time of 180 min, and adsorbent dosage of 0.1 g. For adsorption kinetics, pseudo-first order, pseudo-second order, elovich, and intra-particle diffusion models were fitted, while Langmuir, Freundlich, Temkin, and Dubinin Radushkevich models were fitted in isotherm study. According to the findings, increasing the carbonization temperature (400–700°C) boosted the effectiveness of cadmium removal substantially (70–96%), the best adsorption capacity of 130 mg/g was obtained at 700°C. Meanwhile, the removal efficiency of biochar blending ratios was not significantly different. Similarly, as the carbonization temperature was increased, the rate of Cd2+ adsorption increased dramatically, whereas the rate of Cd2+ desorption dropped. Langmuir isotherm adsorption model and Pseudo-second order kinetic model were found to fit best (R2 = 0.99) on isotherm and kinetics studies, respectively. It can be concluded that employing blended feedstock biochar could improve soil immobilization efficiency for Cd2+ in agricultural fields.
Sorption characteristics of hexavalent chromium in the soil based on batch experiment and their implications to the environment
(Scientific Research Publishing, 2017) Lema, Meserecordias W.; Kwikima, Muhajir M.
The objective of this experimental study was to determine the kinetics and equilibrium sorption of Cr (VI) in soils collected from Hengshui City of Hebei Province, China, based on batch experiments. The main concentration for this paper is on the effect of soil pH, solute concentration and ionic strength as the variable factors in the sorption of Cr (VI) in soils and the assessment of their implications to the environment. Atomic Absorption Spectrophotometer (AAS) was used for Cr (III) analysis; UV-VIS Spectrophotometer for quantification of Cr (VI) in soil samples and determination of electrical conductivity and temperature of the soil samples; and Automatic Laser Particle Size Analyzer LS230 for the determination of soil physical characteristics. Results from this study show that adsorption and reduction are major reactions accounting for removal of Cr (VI) from soil solution. It is concluded that chemical reactions such as reduction, strongly influence Cr (VI) mobility in soil. Adsorption kinetics experiments indicated that Cr (VI) removal from soil solution increases with increasing solute concentration, with decreasing pH and with decreasing ionic strength. Adsorption reactions reached equilibrium within 12 hours in batch reactors. Increasing background electrolyte concentration (KCI) decreases Cr (VI) adsorption on soil. The Cr (VI) adsorption isotherm for this soils conforms well to the Langmuir isotherm at constant pH. Two Cr (VI) adsorption parameters: the maximum sorption capacity (Qo) and Langmuir adsorption constant (KL), were determined as 1.0135 × 10−4 mol/g and 0.0622 mg/L, respectively. The reduction of Cr (VI) into less toxic Cr (III), means reduction of significant environmental problems. Finally, this study advises relevant environmental governing authorities to observe periodic monitoring of the status of Cr (VI) in soils.

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