A global freshwater pollution catastrophe is looming due to pollutants of emerging concern (PECs)... more A global freshwater pollution catastrophe is looming due to pollutants of emerging concern (PECs). Conventional water treatment methods are limited in removing PECs such as pharmaceuticals and dye house effluent from aquatic systems. This study provides an effective potential solution by developing an innovative wastewater treatment method based on solar-light-responsive semiconductor-based photocatalysts. A sol-gel synthesis technique was used to produce Fluorine-Sm3+ co-doped TiO2 (0.6% Sm3+) (FST3) photocatalysts. This was followed by loading multi-walled carbon nanotubes (MWCNTs) in the range of 0.25 to 1 wt% into the FST3 matrix. Solid state UV-visible spectroscopy measurements showed a bathochromic shift into the visible light region after the co-doping of TiO2, whereas XRD analysis confirmed the presence of predominantly anatase polymorphs of TiO2. The FT-IR and EDX results confirmed the presence of the F and Sm3+ dopants in the synthesised photocatalysts. XRD and TEM measure...
Carbon quantum dots (CDs) are a fascinating class of carbon nanomaterials (less than 10 nm in siz... more Carbon quantum dots (CDs) are a fascinating class of carbon nanomaterials (less than 10 nm in size) with unique optical, electrical, and physicochemical properties. In addition to these properties, CQDs exhibit the desired advantages of aqueous stability, low toxicity, high surface area, economic feasibility, chemical inertness, and highly tunable photoluminescence behaviour. Recently, graphitic carbon nitride (g-C3N4) has appeared as one of the required stable carbon-based polymers due to its varied applications in several fields. In this regard, modification strategies have been made in the g-C3N4 semiconductor using CQDs to enhance the adsorptive and photocatalytic activity. In comparison to other semiconductor quantum dots, g-C3N4 shows strong fluorescent properties, such as wide excitation spectra, photostability, and tunable photo-luminescent emission spectra. The interaction inside this multicomponent photocatalyst further promotes the photocatalytic activity by improving cha...
A large population worldwide, especially among poor communities, consumes polluted drinking water... more A large population worldwide, especially among poor communities, consumes polluted drinking water. Commonly used water treatment methods are ineffective for contaminants removal, while advanced treatment technologies are complicated and expensive. Although some column studies have been reported, most studies use batch experiments, and do not provide design parameters for up-scaling the treatment process. The objectives of this study were to: (1) synthesize and characterize biochars derived from Brachystegia spiciformis hardwood, (2) evaluate the adsorption performance in batch experiments, and (3) use column studies to determine the design parameters for a point-of-use (POU) water treatment device. Pristine biochar was the most effective compared to steam activated-biochar, and iron oxide activated biochar. Adsorption data showed that fluoride adsorption was described by the Freundlich model (r = 0.939), while chromium (r = 0.933), and BBD (r = 0.55) data followed the Langmuir model. Column data were described by the Logit (r = 0.99) and Thomas (r = 0.99) models. Layered adsorbents showed more superior fluoride adsorption and required the lowest mass of adsorbent compared to mixed adsorbent columns. While further studies are required to fully optimize this treatment system, the results suggest that biochar based adsorbents can be effectively used in POU water treatment.
Bio- and Nanosorbents from Natural Resources, 2017
In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause f... more In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause for concern. The increase in industrial activity around the world results in the emission of dyes and toxic metals into the aquatic environment and exerts pressure on water treatment plants. The removal of these contaminants is problematic because they can be available in very low concentrations, and water treatment plants are not designed to remove them effectively. A number of approaches including coagulation, precipitation, membrane filtration, and activated carbon adsorption, have been used for the remediation of contaminated water, but these methods are generally limited by high cost and poor selectivity. Lignin- and chitosan-based nanocomposites are potentially useful for these applications because they have minimal environmental footprints, are cost effective, and are compatible with a wide range of materials in composites. Laboratory scale experiments carried out to evaluate these materials have shown that the composites of these materials have remarkable dye and heavy metal (HM) removal capacities, thus making the technology accessible and potentially manageable at a large scale. Using Web of Science, Scopus, Sciencedirect, Springer, and Google Scholar, we evaluated literature on (1) the prevalence and environmental and health impact of pollution due to dye- and metal-laden effluents, (2) available remediation technologies, (3) the synthetic pathways for different chitosan-based nanocomposites, and (4) the potential of chitosan-based nanocomposites for dye and HM removal. There has been a gradual increase in the research of the use of lignin/chitosan-based adsorbent, showing the rapid interest and potential in the materials.
Background: Complete rectal prolapse (CRP) commonly affects the daily life of older people and ha... more Background: Complete rectal prolapse (CRP) commonly affects the daily life of older people and has no established operative treatment approach. We describe our simple method of laparoscopic, sutureless rectopexy, involving rectal mobilization (along with its peritoneum bilaterally) and fixation to the sacral promontory using a fixation device. We also present an analysis of short-term outcomes in patients treated using this procedure. Materials and Methods: We retrospectively evaluated 62 patients with CRP, who underwent a laparoscopic rectopexy via tack fixation, between 2004 and 2017. The peritoneum was widely attached near the site of peritoneal reflection, as in rectal cancer surgery. The hypogastric nerve was carefully detached from the front of the sacrum. Keeping the nerve intact, we lifted and mobilized the dissected rectum cranially towards the promontory, and the rectal peritoneum was affixed to the sacrum by applying 2 to 3 fixed tacks bilaterally, using a fixation device. Results: The median age of the study group was 80 (10 to 91) years. All procedures were successful without serious intraoperative complications; only 1 patient required conversion to open surgery. Median values for operative duration, intraoperative blood loss, and postoperative period of hospitalization were 177 (125 to 441) minutes, 5 (0 to 275) mL, and 7 (3 to 17) days, respectively. Only 6 (9.7%) patients experienced recurrence during the follow-up period. Conclusion: Laparoscopic tacking rectopexy performed using a fixation device for repairing CRP is a simple, safe, and sutureless procedure with no severe complications or mortality.
In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause f... more In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause for concern. The increase in industrial activity around the world results in the emission of dyes and toxic metals into the aquatic environment and exerts pressure on water treatment plants. The removal of these contaminants is problematic because they can be available in very low concentrations, and water treatment plants are not designed to remove them effectively. A number of approaches including coagulation, precipitation, membrane filtration, and activated carbon adsorption, have been used for the remediation of contaminated water, but these methods are generally limited by high cost and poor selectivity. Lignin- and chitosan-based nanocomposites are potentially useful for these applications because they have minimal environmental footprints, are cost effective, and are compatible with a wide range of materials in composites. Laboratory scale experiments carried out to evaluate these...
Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmen... more Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmental pollution and lack of access to energy. Biochar has gained international research attention, but few studies have investigated the potential of biochar to address the challenges in SSA. This paper seeks to identify and evaluate generic potential opportunities and constraints associated with biochar application in sub-Saharan Africa using Zimbabwe as *Manuscript Without Track Changes Click here to download Manuscript: JEMA-D-14-01197R1 Biochar manuscript [Gwenzi et al.,]-[REVISION]-Without Track Ch Click here to view linked References case study. Specific objectives were to; (1) identify and quantify feedstocks for biochar production; (2) review literature on the biochar properties, and evaluate its potential applications in agriculture, environmental remediation and energy provision, and (3) identify research gaps, risks and constraints associated with biochar technology. Biochar feedstocks in Zimbabwe were estimated to be 9.9 Mt yr-1 , predominantly derived from manure (88%) and firewood (10%). This will yield 3.5, 1.7 and 3.1 Mt yr-1 of biochar, bio-oil and synthetic gas, respectively. Land application of the 3.5 Mt yr-1 of biochar (≈ 63% C) would sequester approximately 2.2 Mt yr-1 of soil carbon in Zimbabwe alone, while simultaneously minimizing the environmental and public health risks, and greenhouse gas emissions associated with solid organic wastes. Biochar potentially enhances soil and crop productivity through enhanced nutrient and soil moisture availability, amelioration of acidic soils and stimulation of microbial diversity and activity. Due to its excellent adsorption properties, biochar has potential applications in industrial and environmental applications including water and wastewater treatment, remediation and revegetation of contaminated soils and water. Biochar products have energy values comparable or higher than those of traditional biomass fuels; thereby making them ideal alternative sources of energy especially for poor households without access to electricity. Before the benefits of biochar can be realised in SSA, there is need to overcome multiple risks and constraints such as lack of finance, socioeconomic constraints including negative perceptions and attitudes among both researchers and consumers, and environmental and public health risks. Therefore, there is need to conduct fundamental research to demonstrate the benefits of biochar applications, and develop policy framework and criteria for its production and subsequent adoption.
Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmen... more Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmental pollution and lack of access to energy. Biochar has gained international research attention, but few studies have investigated the potential of biochar to address the challenges in SSA. This paper seeks to identify and evaluate generic potential opportunities and constraints associated with biochar application in sub-Saharan Africa using Zimbabwe as *Manuscript Without Track Changes Click here to download Manuscript: JEMA-D-14-01197R1 Biochar manuscript [Gwenzi et al.,]-[REVISION]-Without Track Ch Click here to view linked References case study. Specific objectives were to; (1) identify and quantify feedstocks for biochar production; (2) review literature on the biochar properties, and evaluate its potential applications in agriculture, environmental remediation and energy provision, and (3) identify research gaps, risks and constraints associated with biochar technology. Biochar feedstocks in Zimbabwe were estimated to be 9.9 Mt yr-1 , predominantly derived from manure (88%) and firewood (10%). This will yield 3.5, 1.7 and 3.1 Mt yr-1 of biochar, bio-oil and synthetic gas, respectively. Land application of the 3.5 Mt yr-1 of biochar (≈ 63% C) would sequester approximately 2.2 Mt yr-1 of soil carbon in Zimbabwe alone, while simultaneously minimizing the environmental and public health risks, and greenhouse gas emissions associated with solid organic wastes. Biochar potentially enhances soil and crop productivity through enhanced nutrient and soil moisture availability, amelioration of acidic soils and stimulation of microbial diversity and activity. Due to its excellent adsorption properties, biochar has potential applications in industrial and environmental applications including water and wastewater treatment, remediation and revegetation of contaminated soils and water. Biochar products have energy values comparable or higher than those of traditional biomass fuels; thereby making them ideal alternative sources of energy especially for poor households without access to electricity. Before the benefits of biochar can be realised in SSA, there is need to overcome multiple risks and constraints such as lack of finance, socioeconomic constraints including negative perceptions and attitudes among both researchers and consumers, and environmental and public health risks. Therefore, there is need to conduct fundamental research to demonstrate the benefits of biochar applications, and develop policy framework and criteria for its production and subsequent adoption.
Water pollution due to dyes and pathogens is problematic worldwide, and the disease burden is hig... more Water pollution due to dyes and pathogens is problematic worldwide, and the disease burden is higher in low-income countries where water treatment facilities are usually inadequate. Thus the development of low-cost techniques for the removal of dyes and pathogens in aquatic systems is critical for safeguarding human and ecological health. In this work, we report the fabrication and use of a photocatalyst derived from waste from coal combustion in removing dyes and pathogens from wastewater. Higher TiO2 loading of the photocatalyst increased the removal efficiency for methyl orange (95.5%), and fluorine-doping improved the disinfection efficacy from 76% to 95% relative to unmodified material. Overall, the work effectively converted hazardous waste into a value-added product that has potential in point-of-use water treatment. Future research should focus on upscaling the technique, investigating the fate of the potential of the photocatalysts for multiple reuse, and the recovery of Ti...
A global freshwater pollution catastrophe is looming due to pollutants of emerging concern (PECs)... more A global freshwater pollution catastrophe is looming due to pollutants of emerging concern (PECs). Conventional water treatment methods are limited in removing PECs such as pharmaceuticals and dye house effluent from aquatic systems. This study provides an effective potential solution by developing an innovative wastewater treatment method based on solar-light-responsive semiconductor-based photocatalysts. A sol-gel synthesis technique was used to produce Fluorine-Sm3+ co-doped TiO2 (0.6% Sm3+) (FST3) photocatalysts. This was followed by loading multi-walled carbon nanotubes (MWCNTs) in the range of 0.25 to 1 wt% into the FST3 matrix. Solid state UV-visible spectroscopy measurements showed a bathochromic shift into the visible light region after the co-doping of TiO2, whereas XRD analysis confirmed the presence of predominantly anatase polymorphs of TiO2. The FT-IR and EDX results confirmed the presence of the F and Sm3+ dopants in the synthesised photocatalysts. XRD and TEM measure...
Carbon quantum dots (CDs) are a fascinating class of carbon nanomaterials (less than 10 nm in siz... more Carbon quantum dots (CDs) are a fascinating class of carbon nanomaterials (less than 10 nm in size) with unique optical, electrical, and physicochemical properties. In addition to these properties, CQDs exhibit the desired advantages of aqueous stability, low toxicity, high surface area, economic feasibility, chemical inertness, and highly tunable photoluminescence behaviour. Recently, graphitic carbon nitride (g-C3N4) has appeared as one of the required stable carbon-based polymers due to its varied applications in several fields. In this regard, modification strategies have been made in the g-C3N4 semiconductor using CQDs to enhance the adsorptive and photocatalytic activity. In comparison to other semiconductor quantum dots, g-C3N4 shows strong fluorescent properties, such as wide excitation spectra, photostability, and tunable photo-luminescent emission spectra. The interaction inside this multicomponent photocatalyst further promotes the photocatalytic activity by improving cha...
A large population worldwide, especially among poor communities, consumes polluted drinking water... more A large population worldwide, especially among poor communities, consumes polluted drinking water. Commonly used water treatment methods are ineffective for contaminants removal, while advanced treatment technologies are complicated and expensive. Although some column studies have been reported, most studies use batch experiments, and do not provide design parameters for up-scaling the treatment process. The objectives of this study were to: (1) synthesize and characterize biochars derived from Brachystegia spiciformis hardwood, (2) evaluate the adsorption performance in batch experiments, and (3) use column studies to determine the design parameters for a point-of-use (POU) water treatment device. Pristine biochar was the most effective compared to steam activated-biochar, and iron oxide activated biochar. Adsorption data showed that fluoride adsorption was described by the Freundlich model (r = 0.939), while chromium (r = 0.933), and BBD (r = 0.55) data followed the Langmuir model. Column data were described by the Logit (r = 0.99) and Thomas (r = 0.99) models. Layered adsorbents showed more superior fluoride adsorption and required the lowest mass of adsorbent compared to mixed adsorbent columns. While further studies are required to fully optimize this treatment system, the results suggest that biochar based adsorbents can be effectively used in POU water treatment.
Bio- and Nanosorbents from Natural Resources, 2017
In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause f... more In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause for concern. The increase in industrial activity around the world results in the emission of dyes and toxic metals into the aquatic environment and exerts pressure on water treatment plants. The removal of these contaminants is problematic because they can be available in very low concentrations, and water treatment plants are not designed to remove them effectively. A number of approaches including coagulation, precipitation, membrane filtration, and activated carbon adsorption, have been used for the remediation of contaminated water, but these methods are generally limited by high cost and poor selectivity. Lignin- and chitosan-based nanocomposites are potentially useful for these applications because they have minimal environmental footprints, are cost effective, and are compatible with a wide range of materials in composites. Laboratory scale experiments carried out to evaluate these materials have shown that the composites of these materials have remarkable dye and heavy metal (HM) removal capacities, thus making the technology accessible and potentially manageable at a large scale. Using Web of Science, Scopus, Sciencedirect, Springer, and Google Scholar, we evaluated literature on (1) the prevalence and environmental and health impact of pollution due to dye- and metal-laden effluents, (2) available remediation technologies, (3) the synthetic pathways for different chitosan-based nanocomposites, and (4) the potential of chitosan-based nanocomposites for dye and HM removal. There has been a gradual increase in the research of the use of lignin/chitosan-based adsorbent, showing the rapid interest and potential in the materials.
Background: Complete rectal prolapse (CRP) commonly affects the daily life of older people and ha... more Background: Complete rectal prolapse (CRP) commonly affects the daily life of older people and has no established operative treatment approach. We describe our simple method of laparoscopic, sutureless rectopexy, involving rectal mobilization (along with its peritoneum bilaterally) and fixation to the sacral promontory using a fixation device. We also present an analysis of short-term outcomes in patients treated using this procedure. Materials and Methods: We retrospectively evaluated 62 patients with CRP, who underwent a laparoscopic rectopexy via tack fixation, between 2004 and 2017. The peritoneum was widely attached near the site of peritoneal reflection, as in rectal cancer surgery. The hypogastric nerve was carefully detached from the front of the sacrum. Keeping the nerve intact, we lifted and mobilized the dissected rectum cranially towards the promontory, and the rectal peritoneum was affixed to the sacrum by applying 2 to 3 fixed tacks bilaterally, using a fixation device. Results: The median age of the study group was 80 (10 to 91) years. All procedures were successful without serious intraoperative complications; only 1 patient required conversion to open surgery. Median values for operative duration, intraoperative blood loss, and postoperative period of hospitalization were 177 (125 to 441) minutes, 5 (0 to 275) mL, and 7 (3 to 17) days, respectively. Only 6 (9.7%) patients experienced recurrence during the follow-up period. Conclusion: Laparoscopic tacking rectopexy performed using a fixation device for repairing CRP is a simple, safe, and sutureless procedure with no severe complications or mortality.
In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause f... more In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause for concern. The increase in industrial activity around the world results in the emission of dyes and toxic metals into the aquatic environment and exerts pressure on water treatment plants. The removal of these contaminants is problematic because they can be available in very low concentrations, and water treatment plants are not designed to remove them effectively. A number of approaches including coagulation, precipitation, membrane filtration, and activated carbon adsorption, have been used for the remediation of contaminated water, but these methods are generally limited by high cost and poor selectivity. Lignin- and chitosan-based nanocomposites are potentially useful for these applications because they have minimal environmental footprints, are cost effective, and are compatible with a wide range of materials in composites. Laboratory scale experiments carried out to evaluate these...
Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmen... more Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmental pollution and lack of access to energy. Biochar has gained international research attention, but few studies have investigated the potential of biochar to address the challenges in SSA. This paper seeks to identify and evaluate generic potential opportunities and constraints associated with biochar application in sub-Saharan Africa using Zimbabwe as *Manuscript Without Track Changes Click here to download Manuscript: JEMA-D-14-01197R1 Biochar manuscript [Gwenzi et al.,]-[REVISION]-Without Track Ch Click here to view linked References case study. Specific objectives were to; (1) identify and quantify feedstocks for biochar production; (2) review literature on the biochar properties, and evaluate its potential applications in agriculture, environmental remediation and energy provision, and (3) identify research gaps, risks and constraints associated with biochar technology. Biochar feedstocks in Zimbabwe were estimated to be 9.9 Mt yr-1 , predominantly derived from manure (88%) and firewood (10%). This will yield 3.5, 1.7 and 3.1 Mt yr-1 of biochar, bio-oil and synthetic gas, respectively. Land application of the 3.5 Mt yr-1 of biochar (≈ 63% C) would sequester approximately 2.2 Mt yr-1 of soil carbon in Zimbabwe alone, while simultaneously minimizing the environmental and public health risks, and greenhouse gas emissions associated with solid organic wastes. Biochar potentially enhances soil and crop productivity through enhanced nutrient and soil moisture availability, amelioration of acidic soils and stimulation of microbial diversity and activity. Due to its excellent adsorption properties, biochar has potential applications in industrial and environmental applications including water and wastewater treatment, remediation and revegetation of contaminated soils and water. Biochar products have energy values comparable or higher than those of traditional biomass fuels; thereby making them ideal alternative sources of energy especially for poor households without access to electricity. Before the benefits of biochar can be realised in SSA, there is need to overcome multiple risks and constraints such as lack of finance, socioeconomic constraints including negative perceptions and attitudes among both researchers and consumers, and environmental and public health risks. Therefore, there is need to conduct fundamental research to demonstrate the benefits of biochar applications, and develop policy framework and criteria for its production and subsequent adoption.
Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmen... more Sub-Saharan Africa (SSA) experiences soil degradation, food and livelihood insecurity, environmental pollution and lack of access to energy. Biochar has gained international research attention, but few studies have investigated the potential of biochar to address the challenges in SSA. This paper seeks to identify and evaluate generic potential opportunities and constraints associated with biochar application in sub-Saharan Africa using Zimbabwe as *Manuscript Without Track Changes Click here to download Manuscript: JEMA-D-14-01197R1 Biochar manuscript [Gwenzi et al.,]-[REVISION]-Without Track Ch Click here to view linked References case study. Specific objectives were to; (1) identify and quantify feedstocks for biochar production; (2) review literature on the biochar properties, and evaluate its potential applications in agriculture, environmental remediation and energy provision, and (3) identify research gaps, risks and constraints associated with biochar technology. Biochar feedstocks in Zimbabwe were estimated to be 9.9 Mt yr-1 , predominantly derived from manure (88%) and firewood (10%). This will yield 3.5, 1.7 and 3.1 Mt yr-1 of biochar, bio-oil and synthetic gas, respectively. Land application of the 3.5 Mt yr-1 of biochar (≈ 63% C) would sequester approximately 2.2 Mt yr-1 of soil carbon in Zimbabwe alone, while simultaneously minimizing the environmental and public health risks, and greenhouse gas emissions associated with solid organic wastes. Biochar potentially enhances soil and crop productivity through enhanced nutrient and soil moisture availability, amelioration of acidic soils and stimulation of microbial diversity and activity. Due to its excellent adsorption properties, biochar has potential applications in industrial and environmental applications including water and wastewater treatment, remediation and revegetation of contaminated soils and water. Biochar products have energy values comparable or higher than those of traditional biomass fuels; thereby making them ideal alternative sources of energy especially for poor households without access to electricity. Before the benefits of biochar can be realised in SSA, there is need to overcome multiple risks and constraints such as lack of finance, socioeconomic constraints including negative perceptions and attitudes among both researchers and consumers, and environmental and public health risks. Therefore, there is need to conduct fundamental research to demonstrate the benefits of biochar applications, and develop policy framework and criteria for its production and subsequent adoption.
Water pollution due to dyes and pathogens is problematic worldwide, and the disease burden is hig... more Water pollution due to dyes and pathogens is problematic worldwide, and the disease burden is higher in low-income countries where water treatment facilities are usually inadequate. Thus the development of low-cost techniques for the removal of dyes and pathogens in aquatic systems is critical for safeguarding human and ecological health. In this work, we report the fabrication and use of a photocatalyst derived from waste from coal combustion in removing dyes and pathogens from wastewater. Higher TiO2 loading of the photocatalyst increased the removal efficiency for methyl orange (95.5%), and fluorine-doping improved the disinfection efficacy from 76% to 95% relative to unmodified material. Overall, the work effectively converted hazardous waste into a value-added product that has potential in point-of-use water treatment. Future research should focus on upscaling the technique, investigating the fate of the potential of the photocatalysts for multiple reuse, and the recovery of Ti...
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Papers by Nhamo Chaukura