Evalde Mulindankaka | China University of Geosciences(Wuhan) (original) (raw)
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Papers by Evalde Mulindankaka
Journal of Earth Science, 2016
The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides (FM) was inv... more The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides (FM) was investigated. A novel method using potassium permanganate and ferric chloride as raw materials was used to synthesise FM. The molar ratio of Fe and Mn in the synthetic Fe-Mn binary oxides was 4: 3. The FM-1 and FM-2 (prepared at different activation temperatures) having high specific surface areas (358.87 and 128.58 m2/g, respectively) were amorphous and of nano particle types. The amount of arsenic adsorbed on FM-1 was higher than that adsorbed on FM-2 particles. After adsorption by FM-1, residual arsenic concentration decreased to less than 10 µg/L. The adsorption kinetics data were analyzed using different kinetic models including pseudo first-order model, pseudo second-order model, Elovich model and intraparticle diffusion model. Pseudo second-order kinetic model was the most appropriate model to describe the adsorption kinetics. The adsorption percentage of As(III) increased in the pH range of 2–3 while it decreased with the increase of pH (3<pH<10). The effects of coexisting anions on As(III) removal using FM-1 and FM-2 were also studied and the order of the effects is as follows: NO3-, Cl-, F-<SO42-, HCO3-<H2PO4-, indicating that H2PO4- is the major competitor with As(III) for adsorptive sites on the surface of the adsorbents. The higher adsorption capacity of FM-1 makes it potentially attractive adsorbent for the removal of As(III) from groundwater.
Science of The Total Environment, 2014
The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides (FM) was inv... more The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides (FM) was investigated. A novel method using potassium permanganate and ferric chloride as raw materials was used to synthesise FM. The molar ratio of Fe and Mn in the synthetic Fe-Mn binary oxides was 4 : 3. The FM-1 and FM-2 (prepared at different activation temperatures) having high specific surface areas (358.87 and 128.58 m 2 /g, respectively) were amorphous and of nano particle types. The amount of arsenic adsorbed on FM-1 was higher than that adsorbed on FM-2 particles. After adsorption by FM-1, residual arsenic concentration decreased to less than 10 μg/L. The adsorption kinetics data were analyzed using different kinetic models including pseudo first-order model, pseudo second-order model, Elovich model and in-traparticle diffusion model. Pseudo second-order kinetic model was the most appropriate model to describe the adsorption kinetics. The adsorption percentage of As(III) increased in the pH range of 2–3 while it decreased with the increase of pH (3<pH<10). The effects of coexisting anions on As(III) removal using FM-1 and FM-2 were also studied and the order of the effects is as follows:, indicating that H 2 PO 4-is the major competitor with As(III) for adsorptive sites on the surface of the ad-sorbents. The higher adsorption capacity of FM-1 makes it potentially attractive adsorbent for the removal of As(III) from groundwater. KEY WORDS: arsenite, adsorption, nano Fe-Mn binary oxide, kinetics, pH.
The reuse of wastewater for irrigation of agricultural land is a well established resources manag... more The reuse of wastewater for irrigation of agricultural land is a well established resources management practice but has the disadvantage of inputting various forms of contaminants into the terrestrial environment including nonylphenol (NP), a well known endocrine disrupting substance. To elucidate the environmental fate and transport of NP, the sorption behavior on sewage-irrigated soil was studied by batch experiment. It was found that sorption processes of NP on different sorbents (soil, humic acid (HA) and silica) could be expressed well using two compartment pseudo first-order model, where both surface and intra-particle diffusion were probable rate-controlling processes. Linear model could better express the sorption of NP on soil, black carbon (BC) and mineral (e.g., SiO2) except HA than Freundlich model. The large value of distribution coefficients of normalized organic carbon (Koc) on soils indicated that NP was limited to migrate to deep soil. The higher desorption partition coefficient of NP on soil showed enhanced hysteresis. According to the experimental data, the calculated thermodynamic parameters implied that the sorption reaction on sewage-irrigation was spontaneous, exothermic and entropy decreasing process. The amount of soil organic matter (SOM) dominated the sorption capacity, whereas the sorption behavior of NP on soil showed no significant correlation with ionic strength.
Research paper, Mar 2015
Prospecting studies indicate that Rwanda has a potential capacity to generate geothermal energy i... more Prospecting studies indicate that Rwanda has a potential capacity to generate geothermal energy in the volcano-tectonically active zones of the East African Rift System (EARS). Two typical regions, Gisenyi and Mashyuza, were reevaluated
for the geothermal potential in Rwanda, where the hot springs were of Na-HCO3 type waters. Geothermometers were applied to estimate subsurface temperatures of Gisenyi and Mashyuza springs and their suitability were discussed using Na-K-Mg diagram. In contradiction to previous studies, the results showed that only K-Mg geothermometer provided reliable estimations for Gisenyi and Mashyuza prospects for which reservoir temperatures are too low for energy production.
Heavy metals are some of environmental pollutants and are toxic even at very low concentrations. ... more Heavy metals are some of environmental pollutants and are toxic even at very low concentrations. Domestic and industrial discharges are probably the two most important sources for heavy metals in the water environment. World is still facing problems of heavy metal discharges into natural ecosystems by factories and household without any prior treatment. The toxic heavy metals are entering the food chain through drinking water, agriculture and fisheries activities and therefore endangering human life.
The general objective of this study is to investigate on the major mechanisms responsible for heavy metal removal from the water phase by macrophyte plants.
Results, obtained by different authors on the accumulation of heavy metals in plants and the screening of effective metal-accumulating plants under laboratory and field conditions, have been analysed and generalized with the intention of assessing the potential of phytoremediation as an emerging technology for the purification of wastewater contaminated by heavy metals.
Water hyacinth (Eichhornia crassipes) has been used in the remediation process of chromium ions in the present work because this plant has elaborated much roots system providing more binding sites for Cr6+. The mechanisms for fixation of Cr6+ by macrophytes plants had been reported. The investigation had been conducted using different literatures about heavy metals commonly found in polluted industrial wastewater. Measurements have been carried out using spectrophotometric method. Trace metal remaining in water sample was studied. It has been found that the Eichhornia crassipes had phytoextracted 1.8mg/L (about 40%) from an initial concentration of 3mg/L within a period of one week, which indicated its potential in heavy metal removal from wastewater. Naturally wastewater contaminated with heavy metals may be treated at large scale using macrophytes especially in industrial regions.
Journal of Earth Science, 2016
The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides (FM) was inv... more The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides (FM) was investigated. A novel method using potassium permanganate and ferric chloride as raw materials was used to synthesise FM. The molar ratio of Fe and Mn in the synthetic Fe-Mn binary oxides was 4: 3. The FM-1 and FM-2 (prepared at different activation temperatures) having high specific surface areas (358.87 and 128.58 m2/g, respectively) were amorphous and of nano particle types. The amount of arsenic adsorbed on FM-1 was higher than that adsorbed on FM-2 particles. After adsorption by FM-1, residual arsenic concentration decreased to less than 10 µg/L. The adsorption kinetics data were analyzed using different kinetic models including pseudo first-order model, pseudo second-order model, Elovich model and intraparticle diffusion model. Pseudo second-order kinetic model was the most appropriate model to describe the adsorption kinetics. The adsorption percentage of As(III) increased in the pH range of 2–3 while it decreased with the increase of pH (3<pH<10). The effects of coexisting anions on As(III) removal using FM-1 and FM-2 were also studied and the order of the effects is as follows: NO3-, Cl-, F-<SO42-, HCO3-<H2PO4-, indicating that H2PO4- is the major competitor with As(III) for adsorptive sites on the surface of the adsorbents. The higher adsorption capacity of FM-1 makes it potentially attractive adsorbent for the removal of As(III) from groundwater.
Science of The Total Environment, 2014
The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides (FM) was inv... more The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides (FM) was investigated. A novel method using potassium permanganate and ferric chloride as raw materials was used to synthesise FM. The molar ratio of Fe and Mn in the synthetic Fe-Mn binary oxides was 4 : 3. The FM-1 and FM-2 (prepared at different activation temperatures) having high specific surface areas (358.87 and 128.58 m 2 /g, respectively) were amorphous and of nano particle types. The amount of arsenic adsorbed on FM-1 was higher than that adsorbed on FM-2 particles. After adsorption by FM-1, residual arsenic concentration decreased to less than 10 μg/L. The adsorption kinetics data were analyzed using different kinetic models including pseudo first-order model, pseudo second-order model, Elovich model and in-traparticle diffusion model. Pseudo second-order kinetic model was the most appropriate model to describe the adsorption kinetics. The adsorption percentage of As(III) increased in the pH range of 2–3 while it decreased with the increase of pH (3<pH<10). The effects of coexisting anions on As(III) removal using FM-1 and FM-2 were also studied and the order of the effects is as follows:, indicating that H 2 PO 4-is the major competitor with As(III) for adsorptive sites on the surface of the ad-sorbents. The higher adsorption capacity of FM-1 makes it potentially attractive adsorbent for the removal of As(III) from groundwater. KEY WORDS: arsenite, adsorption, nano Fe-Mn binary oxide, kinetics, pH.
The reuse of wastewater for irrigation of agricultural land is a well established resources manag... more The reuse of wastewater for irrigation of agricultural land is a well established resources management practice but has the disadvantage of inputting various forms of contaminants into the terrestrial environment including nonylphenol (NP), a well known endocrine disrupting substance. To elucidate the environmental fate and transport of NP, the sorption behavior on sewage-irrigated soil was studied by batch experiment. It was found that sorption processes of NP on different sorbents (soil, humic acid (HA) and silica) could be expressed well using two compartment pseudo first-order model, where both surface and intra-particle diffusion were probable rate-controlling processes. Linear model could better express the sorption of NP on soil, black carbon (BC) and mineral (e.g., SiO2) except HA than Freundlich model. The large value of distribution coefficients of normalized organic carbon (Koc) on soils indicated that NP was limited to migrate to deep soil. The higher desorption partition coefficient of NP on soil showed enhanced hysteresis. According to the experimental data, the calculated thermodynamic parameters implied that the sorption reaction on sewage-irrigation was spontaneous, exothermic and entropy decreasing process. The amount of soil organic matter (SOM) dominated the sorption capacity, whereas the sorption behavior of NP on soil showed no significant correlation with ionic strength.
Research paper, Mar 2015
Prospecting studies indicate that Rwanda has a potential capacity to generate geothermal energy i... more Prospecting studies indicate that Rwanda has a potential capacity to generate geothermal energy in the volcano-tectonically active zones of the East African Rift System (EARS). Two typical regions, Gisenyi and Mashyuza, were reevaluated
for the geothermal potential in Rwanda, where the hot springs were of Na-HCO3 type waters. Geothermometers were applied to estimate subsurface temperatures of Gisenyi and Mashyuza springs and their suitability were discussed using Na-K-Mg diagram. In contradiction to previous studies, the results showed that only K-Mg geothermometer provided reliable estimations for Gisenyi and Mashyuza prospects for which reservoir temperatures are too low for energy production.
Heavy metals are some of environmental pollutants and are toxic even at very low concentrations. ... more Heavy metals are some of environmental pollutants and are toxic even at very low concentrations. Domestic and industrial discharges are probably the two most important sources for heavy metals in the water environment. World is still facing problems of heavy metal discharges into natural ecosystems by factories and household without any prior treatment. The toxic heavy metals are entering the food chain through drinking water, agriculture and fisheries activities and therefore endangering human life.
The general objective of this study is to investigate on the major mechanisms responsible for heavy metal removal from the water phase by macrophyte plants.
Results, obtained by different authors on the accumulation of heavy metals in plants and the screening of effective metal-accumulating plants under laboratory and field conditions, have been analysed and generalized with the intention of assessing the potential of phytoremediation as an emerging technology for the purification of wastewater contaminated by heavy metals.
Water hyacinth (Eichhornia crassipes) has been used in the remediation process of chromium ions in the present work because this plant has elaborated much roots system providing more binding sites for Cr6+. The mechanisms for fixation of Cr6+ by macrophytes plants had been reported. The investigation had been conducted using different literatures about heavy metals commonly found in polluted industrial wastewater. Measurements have been carried out using spectrophotometric method. Trace metal remaining in water sample was studied. It has been found that the Eichhornia crassipes had phytoextracted 1.8mg/L (about 40%) from an initial concentration of 3mg/L within a period of one week, which indicated its potential in heavy metal removal from wastewater. Naturally wastewater contaminated with heavy metals may be treated at large scale using macrophytes especially in industrial regions.