AbstractLow cost and locally available Moringa seed powder as a potential biosorbent was tested f... more AbstractLow cost and locally available Moringa seed powder as a potential biosorbent was tested for its effectiveness in the removal of nitrobenzene (NB) from aqueous solution. Biochared Moringa oleifera seed powder was also used to compare its performance in the uptake of NB from aqueous solution. Fourier transform infrared spectroscopy fingerprint region of the biochared M. oleifera seed powder was clearer as compared to the raw. Pores observed by the scanning electron microscopy analysis were found to be 0.84 and 1.23 cm3 g−1 (by BET analysis) for the raw and biochared M. oleifera seed powder, respectively. The carbon elemental analysis by energy-dispersive X-ray spectroscopy was 80 and 70% for the raw and biochared M. oleifera seed powder, respectively. The removal efficiencies of the two sorbents were evaluated using factors such as solution pH, biosorbent dosage, contact time and initial NB concentration. A basic pH of 11 was found to be optimum for the uptake of NB for both sorbents. The sorption e...
Abstract In Africa, ochre is ubiquitous in archaeological sites after 100 ka and likely served a ... more Abstract In Africa, ochre is ubiquitous in archaeological sites after 100 ka and likely served a symbolic role in the lives of prehistoric people. Archaeological excavation of the c. 100–72 ka Middle Stone Age (MSA) levels at Blombos Cave (BBC) located in the southern Cape, South Africa, have yielded significant amounts of ochre as artefacts or residues. Although recent archaeological evidence from BBC and elsewhere has provided remarkable insights into the ways that ochre was used, for example its use as a pigmented ‘paint’, the significance of ochre can be further understood by studying its procurement pattern. To this end, the geochemical characterisation of recovered ochre can tell us about the temporal and spatial variation present at a site. The analysis of BBC ochre was accomplished using FTIR, ED XRF, ICP OES and XRD with the aim of determining the mineral and elemental composition variability of ochre across layers and thereby gauging whether there were preferred or different ochre procurement patterns or sources over time. For example, it was found that ochre residues from the c. 100 ka CP layer had kaolinite and quartz as the principal minerals, while ochre residues from the c. 97 ka CJ layer consisted mainly of calcite and quartz. Thus, mineral composition can indicate procurement of different sources of ochre during the various stages of the cave occupation. Elemental analysis of ochre residues from the c. 77–72 ka Still Bay, CJ and CP layers also revealed differences in minor and trace elements. These findings seem to indicate some differences in the ochre from these levels and can also be taken as an indication of different ochre sourcing.
Mercury speciation was determined in areas impacted by gold mining. Both inorganic and methylmerc... more Mercury speciation was determined in areas impacted by gold mining. Both inorganic and methylmercury were detected at high concentrations in all watersheds where mining occurred. Migration of mercury from pollution sources due to seasonal influences was determined. Enhancement of mercury methylation occurred in deeper sediments at the lowest redox potential, higher pH, carbon and sulphur and enrichment of inorganic mercury.
Artisanal and Small-scale Gold Mining (ASGM) activities employing the mercury amal-gamationtechni... more Artisanal and Small-scale Gold Mining (ASGM) activities employing the mercury amal-gamationtechnique have resulted in a significant drop in the quality of water from Ngwabalozi River, Zimbabwe. Mercury levels as high as 0.31 mg L-1have been reported in its waters and the low river pH (pH 3) favors proliferation of microorganisms responsible for methylmercury (a potent neurotoxin) formation. Thus, removal of mercury from contaminated systems is a priority. Therefore, the aim of this study is to develop a low-cost batch reactor for the removal of mercury from mercury contaminated acidic waters tomeet the World Health Organization (WHO) standard of 0.006 mg L-1using Cladophorasp. algae. Optimum reactor parameters were deter-mined by studying the effect of contact time, pH, initial mercury concentration and the presence of competing cations on the adsorption of mercury by Cladophorasp. The mass of algae required in a 1000 Lbatch reactor was then determined at the optimum adsorption cond...
A smart sorbent consisting of benzo[k]fluoranthene-imprinted and indeno[1 2 3-cd]pyrene-imprinted... more A smart sorbent consisting of benzo[k]fluoranthene-imprinted and indeno[1 2 3-cd]pyrene-imprinted polymers mixed at 1:1 (w/w) was successfully screened from several cavity-tuning experiments and used in the isolation of polycyclic aromatic hydrocarbons from spiked solution. The polymer mixture showed high cross selectivity and affinity towards all the 16 US-EPA priority polycyclic aromatic hydrocarbons. The average extraction efficiency from a cyclohexane solution was 65 ± 13.3% (n = 16, SD). Batch adsorption and kinetic studies confirmed that the binding of polycyclic aromatic hydrocarbons onto the polymer particles resulted in formation of a monolayer and that the binding process was the rate limiting step. The imprinted polymer performance studies confirmed that the synthesized polymer had an imprinting efficiency of 103.9 ± 3.91% (n = 3, SD). A comparison of the theoretical number of cavities and the experimental binding capacity showed that the overall extent of occupation of the imprinted cavities in the presence of excess polycyclic aromatic hydrocarbons was 128 ± 6.45% (n = 3, SD). The loss of selectivity was estimated at 2.9% with every elution cycle indicating that the polymer can be re-used several times with limited loss of selectivity and sensitivity. The polymer combination has shown to be an effective adsorbent that can be used to isolate all the 16 US-EPA priority polycyclic aromatic hydrocarbons in solution.
Proceedings of the International Conference on Mine Closure, 2008
Mercury is present in the environment in different molecular forms with specific biogeochemical t... more Mercury is present in the environment in different molecular forms with specific biogeochemical transformations and ecotoxicities. Inorganic Hg2+ is the main form in water and sediment samples. Special attention is given to transformations which lead to the in situ production of methylmercury. The concentrations of organomercury species are very low (usually ng/L) in environmental aquatic environments but the toxic effect of these species can be significant due to their tendency for bioaccumulation and biomagnification in the food chain. The determination of total concentrations of mercury is therefore not sufficient to understand its fate in the environment. The objectives of this study are to assess mercury and tin speciation in regions exposed to potential environmental pollution due to the reprocessing of old gold sand and slimes tailings dumps. Water, sediments, soils, aquatic green algae, common reeds and spinach plants were sampled and analyzed. The study included collection of ancillary data (pH and redox potential) which are critically important for mercury-monitoring programmes. The data will be used for a development of predictive models based on thermodynamic solution equilibria including transformations, transport, fate and biological uptake.
AbstractLow cost and locally available Moringa seed powder as a potential biosorbent was tested f... more AbstractLow cost and locally available Moringa seed powder as a potential biosorbent was tested for its effectiveness in the removal of nitrobenzene (NB) from aqueous solution. Biochared Moringa oleifera seed powder was also used to compare its performance in the uptake of NB from aqueous solution. Fourier transform infrared spectroscopy fingerprint region of the biochared M. oleifera seed powder was clearer as compared to the raw. Pores observed by the scanning electron microscopy analysis were found to be 0.84 and 1.23 cm3 g−1 (by BET analysis) for the raw and biochared M. oleifera seed powder, respectively. The carbon elemental analysis by energy-dispersive X-ray spectroscopy was 80 and 70% for the raw and biochared M. oleifera seed powder, respectively. The removal efficiencies of the two sorbents were evaluated using factors such as solution pH, biosorbent dosage, contact time and initial NB concentration. A basic pH of 11 was found to be optimum for the uptake of NB for both sorbents. The sorption e...
Abstract In Africa, ochre is ubiquitous in archaeological sites after 100 ka and likely served a ... more Abstract In Africa, ochre is ubiquitous in archaeological sites after 100 ka and likely served a symbolic role in the lives of prehistoric people. Archaeological excavation of the c. 100–72 ka Middle Stone Age (MSA) levels at Blombos Cave (BBC) located in the southern Cape, South Africa, have yielded significant amounts of ochre as artefacts or residues. Although recent archaeological evidence from BBC and elsewhere has provided remarkable insights into the ways that ochre was used, for example its use as a pigmented ‘paint’, the significance of ochre can be further understood by studying its procurement pattern. To this end, the geochemical characterisation of recovered ochre can tell us about the temporal and spatial variation present at a site. The analysis of BBC ochre was accomplished using FTIR, ED XRF, ICP OES and XRD with the aim of determining the mineral and elemental composition variability of ochre across layers and thereby gauging whether there were preferred or different ochre procurement patterns or sources over time. For example, it was found that ochre residues from the c. 100 ka CP layer had kaolinite and quartz as the principal minerals, while ochre residues from the c. 97 ka CJ layer consisted mainly of calcite and quartz. Thus, mineral composition can indicate procurement of different sources of ochre during the various stages of the cave occupation. Elemental analysis of ochre residues from the c. 77–72 ka Still Bay, CJ and CP layers also revealed differences in minor and trace elements. These findings seem to indicate some differences in the ochre from these levels and can also be taken as an indication of different ochre sourcing.
Mercury speciation was determined in areas impacted by gold mining. Both inorganic and methylmerc... more Mercury speciation was determined in areas impacted by gold mining. Both inorganic and methylmercury were detected at high concentrations in all watersheds where mining occurred. Migration of mercury from pollution sources due to seasonal influences was determined. Enhancement of mercury methylation occurred in deeper sediments at the lowest redox potential, higher pH, carbon and sulphur and enrichment of inorganic mercury.
Artisanal and Small-scale Gold Mining (ASGM) activities employing the mercury amal-gamationtechni... more Artisanal and Small-scale Gold Mining (ASGM) activities employing the mercury amal-gamationtechnique have resulted in a significant drop in the quality of water from Ngwabalozi River, Zimbabwe. Mercury levels as high as 0.31 mg L-1have been reported in its waters and the low river pH (pH 3) favors proliferation of microorganisms responsible for methylmercury (a potent neurotoxin) formation. Thus, removal of mercury from contaminated systems is a priority. Therefore, the aim of this study is to develop a low-cost batch reactor for the removal of mercury from mercury contaminated acidic waters tomeet the World Health Organization (WHO) standard of 0.006 mg L-1using Cladophorasp. algae. Optimum reactor parameters were deter-mined by studying the effect of contact time, pH, initial mercury concentration and the presence of competing cations on the adsorption of mercury by Cladophorasp. The mass of algae required in a 1000 Lbatch reactor was then determined at the optimum adsorption cond...
A smart sorbent consisting of benzo[k]fluoranthene-imprinted and indeno[1 2 3-cd]pyrene-imprinted... more A smart sorbent consisting of benzo[k]fluoranthene-imprinted and indeno[1 2 3-cd]pyrene-imprinted polymers mixed at 1:1 (w/w) was successfully screened from several cavity-tuning experiments and used in the isolation of polycyclic aromatic hydrocarbons from spiked solution. The polymer mixture showed high cross selectivity and affinity towards all the 16 US-EPA priority polycyclic aromatic hydrocarbons. The average extraction efficiency from a cyclohexane solution was 65 ± 13.3% (n = 16, SD). Batch adsorption and kinetic studies confirmed that the binding of polycyclic aromatic hydrocarbons onto the polymer particles resulted in formation of a monolayer and that the binding process was the rate limiting step. The imprinted polymer performance studies confirmed that the synthesized polymer had an imprinting efficiency of 103.9 ± 3.91% (n = 3, SD). A comparison of the theoretical number of cavities and the experimental binding capacity showed that the overall extent of occupation of the imprinted cavities in the presence of excess polycyclic aromatic hydrocarbons was 128 ± 6.45% (n = 3, SD). The loss of selectivity was estimated at 2.9% with every elution cycle indicating that the polymer can be re-used several times with limited loss of selectivity and sensitivity. The polymer combination has shown to be an effective adsorbent that can be used to isolate all the 16 US-EPA priority polycyclic aromatic hydrocarbons in solution.
Proceedings of the International Conference on Mine Closure, 2008
Mercury is present in the environment in different molecular forms with specific biogeochemical t... more Mercury is present in the environment in different molecular forms with specific biogeochemical transformations and ecotoxicities. Inorganic Hg2+ is the main form in water and sediment samples. Special attention is given to transformations which lead to the in situ production of methylmercury. The concentrations of organomercury species are very low (usually ng/L) in environmental aquatic environments but the toxic effect of these species can be significant due to their tendency for bioaccumulation and biomagnification in the food chain. The determination of total concentrations of mercury is therefore not sufficient to understand its fate in the environment. The objectives of this study are to assess mercury and tin speciation in regions exposed to potential environmental pollution due to the reprocessing of old gold sand and slimes tailings dumps. Water, sediments, soils, aquatic green algae, common reeds and spinach plants were sampled and analyzed. The study included collection of ancillary data (pH and redox potential) which are critically important for mercury-monitoring programmes. The data will be used for a development of predictive models based on thermodynamic solution equilibria including transformations, transport, fate and biological uptake.
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Papers by Ewa Cukrowska