Browsing by Author "Machunda, Revocatus"

Now showing 1 - 20 of 137

Adsorption of phenol and methylene blue contaminants onto high-performance catalytic activated carbon from biomass residues
(Cellpress, 2025-01-15) Bih, Numfor; Rwiza, Mwemezi; Ripanda, Asha; Mahamat, Assia; Machunda, Revocatus; Choi, Joon
Organic contaminants from wastewater toxicity to the environment has increased during the last few decades and, therefore, there is an urgent need to decontaminate wastewater prior to disposal. This study aimed to create a high surface area catalytic activated carbon (AC) under same carbonization conditions for phenol and methylene blue (organic wastewater) decontamination. Moringa oleifera husk (MH), sesame husk (SH), and baobab husk (BH) were used to prepare activated carbon for the removal of methylene blue (MB) and phenol (Ph). After characterization of the adsorbent, the BET surface areas of the M. oleifera husk activated carbon (MHC), sesame husk activated carbon (SHC), and baobab husk activated carbon (BHC) were 1902.30 m2/g, 1115.90 m2/g, and 1412.40 m2/g, respectively. Mono-adsorption and binary-adsorption systems were studied for Ph and MB adsorption. Furthermore, the effect of initial organic waste concentration, contact time, pH, temperature and AC dosage, on adsorption capacity were studied. The mono adsorption system isotherms and kinetics studies used to analyze Phenol and MB adsorption best fitted Langmuir and pseudo-second-order models. The Freundlich isotherm and pseudo-second-order model best fitted the experimental data for the binary-adsorption system. The high maximum adsorption capacities of organic waste for the single and binary systems were 352.25–855.96 mg/g and 348.90–456.39 mg/g, respectively. The results showed that the high surface activated carbon produced had the potential to adsorb high concentrations of MB and Phenol contaminants.
Adsorption-capacitive deionization hybrid system with activated carbon of modified potential of zero charge
(Elsevier, 2023-02-15) Sufiani, Omari; Elisadiki, Joyce; Tanaka, Hideki; Teshima, Katsuya; Sahini, Mtabazi; Machunda, Revocatus; Jande, Yusufu
In this study water solutions are desalinated with carbon electrodes of modified surface charges. The idea is to endow the electrodes with the ability to physically adsorb salt ions without applying potential so as to save energy. The modification enhanced to decrease the energy consumption of a newly invented adsorption-CDI hybrid system by 19%, since modified activated carbon cell consumed 0.620 (relative error 3.00%) kWh/m3 compared to pristine activated carbon cell which consumed 0.746 (relative error 1.20%) kWh/m3. Further analysis revealed high adsorption capacity of the modified activated carbon electrode cell which exhibited 9.0 (relative error 2.22%) compared to activated carbon cell with 5.3 (relative error 5.66%) mg g−1. These results show the potential of surface modification in adding value to low cost activated carbons for application in CDI.
Agrochemicals use in horticulture industry in Tanzania and their potential impact to water resources
(International Journal of Biological and Chemical Sciences, 2014-04) Lema, Emmy; Machunda, Revocatus; Njau, Karoli
The objective of this review was to analyze the existing information on the use of agrochemicals (Fertilizers and Pesticides) in the Tanzanian horticulture industry especially the Northern regions and their potential to impacting water resources. Agrochemicals play an important role in horticulture, and have been widely used in Tanzania for crop protection and increasing productivity. Apart from these benefits, agrochemicals have the potential to impair the quality of water resources for different end uses. Majority of communities in Tanzania depend on surface water from rivers and lakes for potable uses such as washing, drinking and domestic animals also drink from these sources. Reports from studies done in Northern Tanzania have indicated the presence of significant levels of pesticides, phosphates and nitrates in surface and groundwater. It is apparent that most of the horticultural farms in Northern Tanzania are located on gently sloping land adjacent to water bodies. Thus discharges of wastewaters from horticulture farms may affect the quality of water resources through run-off and groundwater through infiltration if proper management of the agrochemicals is not well adhered to. The agrochemicals that have been widely used and identified as potential environmental pollutants from their use as horticultural chemicals are reviewed. The potentially adverse impacts of these agrochemicals to water resources are discussed. The review concludes with a discussion of the directions for further investigation.
Antibiotic Resistance Patterns of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa Isolated from Hospital Wastewater
(Applied Microbiology, 2023-07-08) Karungamy, Petro; Rugaika, Anita; Mte, Kelvin; Machunda, Revocatus
Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in treated hospital wastewater effluents constitute a major environmental and public health concern. The aim of this study was to investigate the antibiotic resistance patterns of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa isolated from wastewater effluent at the Benjamin Mkapa Hospital (BMH) in Dodoma, Tanzania. These bacteria were selected to represent the most prevalent gram-negative bacteria found in hospital wastewater, and they have the potential to generate resistance and spread resistance genes to antibiotics. The wastewater BMH is treated in a Constructed Wetland (CW) planted with Typha latifolia before being released into the environment. The bacteria were isolated from wastewater effluent collected at the outlet of the CW. Isolated bacteria were analyzed for antibiotic resistance by disc diffusion method. Molecular identification of bacterial species was performed by using 16S rRNA. The results show that Klebsiella ssp. was the most common isolate detected, with a prevalence of 39.3%, followed by E. coli (27.9%) and Pseudomonas ssp. (18.0%). Klebsiella ssp. were more resistant than Pseudomonas ssp. for Tetracycline, Gentamycin, Ciprofloxacin, and Sulfamethoxazole. Pseudomonas ssp. were more resistant than Klebsiella ssp. for Ceftriaxone and Azithromycin. Klebsiella ssp. harbored more resistance genes (40%), followed by Pseudomonas ssp. (35%) and E. coli (20%). The findings of this investigation indicate that the effluent from the CW requires additional treatment to reduce discharged ARB and ARGs in the receiving water bodies. As a result, the effluent quality of the CW should be continuously monitored and assessed, and further developments for treating the final effluent are necessary.
Antibiotic-resistant microbial populations in urban receiving waters and wastewaters from Tanzania
(Elsevier, 2023) Ripanda, Asha; Rwiza, Mwemezi; Nyanza, Elias; Miraji, Hossein; Bih, Numfor; Mzula, Alexanda; Mwega, Elisa; Njau, Karoli; Vuai, Said; Machunda, Revocatus
Antimicrobial resistance against certain medications in the pathogenic microbial community is globally increasing due to the continual discharge and disposal of pharmaceuticals in the environment. The phenomenon resulted in significant antibiotic resistance among several exposed Enterobacteriaceae species, with wastewater treatment plants (WWTPs) and rivers serving as significant reservoirs. Despite antibiotic resistance being a tragedy, particularly in treating diseases by using antibiotics, local and regional studies indicating the severity, resistant species and the molecular level insight into these pathogens are scarce, thus requiring immediate intervention. This study, therefore, investigated wastewater from wastewater treatment ponds and receiving waters for the presence of resistant pathogens through phenotypical and molecular approach screening of their genes. Among the 57 analyzed samples, 18 (67%, n = 27) isolates of Klebsiella spp.., 4 (80%, n = 5) isolates of Proteus spp., 1 (100%, n = 1) of isolated Pseudomonas aeruginosa and 6 (18%, n = 34) of E. coli found were resistant to at least 1 among the tested antibiotics. E. coli had an 83% higher proportion of multi-drug resistance (MDR) than Klebsiella spp.., which had 68.5%, and no MDR was shown by P. aeruginosa isolates. Among the 20 bacterial isolates of antibiotic-resistant genes, showed that E. coli harboured 39%, followed by 22% of Klebsiella spp. Eleven (11) isolates of these 20 (55%) contained sulphonamides resistant genes: Sul 1 (n = 4) and Sul 2 (n = 7). Ten (10) isolates (50%) contained the tetracycline-resistant genes in which 4 isolates showed the Tet A, Tet B – 1 and 5 isolates contained Tet D. β-lactamases (bla CTX-M and bla SHV) were found in 7 isolates (35%). The existence of these antibiotic-resistant species in the urban receiving and wastewater presents a threat of transmission of diseases to humans and animals that are not cured by the existing medications, jeopardizing public health safety.
Assessment of agrochemical residues in wastewater from selected horticultural farms in Arusha, Tanzania
(International Journal of Environmental Sciences, 2015-09-07) Emmy, Lema; Machunda, Revocatus; Njau, Karoli
Arusha region in Tanzania has been involved for quite some time on commercial horticulture. The use of agrochemicals results to increased crop productivity and consequently offers farmers major economic returns. However, the use of agrochemicals and the adjacency of horticultural farms to streams and rivers have the potential to contribute to water pollution if control measures are not effective. We analysed the physical and chemical parameters of wastewater discharged from selected horticultural farms in Arusha and detected nitrates (NO3-), phosphates (PO43-), sulphates (SO42-) and permethrins insecticide in the effluents discharged into the environment. The mean concentration levels ranged from (4.5 ppm - 64.08 ppm) for NO3-, (3.22 ppm - 47.64 ppm) for PO43-, (91.42 ppm - 139 ppm) for SO42- and permethrin was 0.63 ppm. Of all the farms monitored, eighty percent (80%) had high levels of PO43-, sixty percent (60 %) had high levels of NO3- and twenty percent (20 %) had high levels of permethrin above the allowable limits for discharge into receiving water resources. It may be concluded that the continued agrochemical use may lead to contamination of adjacent water resources which may in the long run cause adverse health effects to the downstream water users. Continual monitoring of agrochemical residues is recommended to inform and ensure compliance with the stipulated standards and regulations for wastewater discharg
Assessment of Fluoride Bioaccumulation Potential in African Catfish (Clarias gariepinus) Reared in Fluoride Rich Water
(University of Dar es Salaam, 2021-05) Bejumula, Jophillene; Machunda, Revocatus; Pasape, Liliane; Mtei, Kelvin
Fluoride bioaccumulation in fish poses a significant impact on their growth, survival and consequently to upper trophic levels. Few studies have reported the impacts of high fluoride concentrations and their accumulation potential to catfish in African settings. A 60-day catfish cultivation was conducted at Ngarenanyuki ward and the Nelson Mandela African Institution of Science and Technology (NM-AIST) in Arusha, Tanzania to determine fluoride bioaccumulation and its impacts to catfish growth and survival. Juvenile catfish were exposed to 36 mg F–/L pond water and synthetic water containing fluoride (NaF) concentrations of 5, 15, 36 and 45 mg/L in aquaria set at NM-AIST laboratory. Fluoride concentrations in fish tissues were analysed by ion- selective electrode. Fish survival rate was greater than 90% in ≤ 36 mg/L fluoride levels compared to 65.8% in 45 mg F–/L aquarium. Significant fluoride bioaccumulation was observed in fish bones (222.00 mg/kg, dry weight), gills (177.4 mg/kg), skin (9 mg/kg) and low amount in fillets (1.467 mg/kg). Fluoride bioaccumulation significantly rose with fluoride levels increase and exposure time (p = 0.000). The study concludes that high fluoride occurrence and its increased exposure time increases fluoride bioaccumulation in African catfish. Therefore, growing catfish in water containing ≥ 45 mg F–/L requires defluoridation process.
Assessment of fluoride removal in a batch electrocoagulation process: A case study in the Mount Meru Enclave
(Elsevier B.V., 2021-03-04) Mureth, Risala; Machunda, Revocatus; Njau, Karoli; Dodoo-Arhin, David
The presence of excessive amounts of fluoride than prescribed standards has been reported in various sources of domestic water supply around the slopes of Mount Meru and other parts in Tanzania. Efforts to remove the excessive fluoride have been carried out using various technologies. In this study, electrocoagulation experiments were carried out to assess its efficiency on fluoride removal. The fluoride concentration tested ranged from 1.37 to 48 mg/L in both synthetic and natural waters. The voltage applied in the electrocoagulation (EC) process ranged from 0 to 50 V while maintaining pH values of 4 to 9. The representative experimental results for the Ngarenanyuki river water with initial fluoride concentration of 29.5 mg/L accomplished a removal efficiency of 90% at an optimal electrolysis time of 30 min, an applied voltage of 30 V and an optimal pH of 6. The method showed efficient fluoride removal in water to allowable limits by World Health Organization (WHO) and Tanzania Bureau of Standards (TBS) (1.5 mg/L). Despite the voltage applied (30 V), the pH at neutrality remained unchanged thus making the process more efficient. At this voltage (30 V) the process has been reported previously also to have the capability of disinfecting the water and hence rendering such water safe for use
Assessment of fluoride removal in a batch electrocoagulation process: A case study in the Mount Meru Enclave.
(Elseiver, 2021-03-01) Mureth, Risala; Machunda, Revocatus; Njau, Karoli; Arhin, David
The presence of excessive amounts of fluoride than prescribed standards has been reported in various sources of domestic water supply around the slopes of Mount Meru and other parts in Tanzania. Efforts to remove the excessive fluoride have been carried out using various technologies. In this study, electrocoagulation experiments were carried out to as- sess its efficiency on fluoride removal. The fluoride concentration tested ranged from 1.37 to 48 mg/L in both synthetic and natural waters. The voltage applied in the electrocoag- ulation (EC) process ranged from 0 to 50 V while maintaining pH values of 4 to 9. The representative experimental results for the Ngarenanyuki river water with initial fluoride concentration of 29.5 mg/L accomplished a removal efficiency of 90% at an optimal elec- trolysis time of 30 min, an applied voltage of 30 V and an optimal pH of 6. The method showed efficient fluoride removal in water to allowable limits by World Health Organiza- tion (WHO) and Tanzania Bureau of Standards (TBS) (1.5 mg/L). Despite the voltage applied (30 V), the pH at neutrality remained unchanged thus making the process more efficient. At this voltage (30 V) the process has been reported previously also to have the capability of disinfecting the water and hence rendering such water safe for use.
The Assessment of Heavy Metals and Natural Radioactivity in the Phosphate Tailings at Minjingu Mines in Tanzania
(Journal of Ecological Engineering, 2024-04-12) Mdach, Daniel; Rugaika, Anita; Machunda, Revocatus
Extraction and processing of the phosphate rocks has produced a massive amount of waste and posed a significant environmental concern. The majority of wastes generated in the fertiliser industry are overburden or waste rocks from mining, and phosphate tailings (PTs) or phosphogyp-sum from the beneficiation process. Phosphate rock mining and beneficiation expose heavy metals and radionuclides into the environment, which are harmful to living things. The purpose of this study was to determine the concentration levels of heavy metals and radionuclides ac- tivity in the phosphate tailings at Minjingu mines in northen of Tanzania. Heavy metals content and radionu-clide activity concentration were determined using energy dispersive X-ray fluoresence spectroscopy (ED-XRF) and high pure garmin energy detector (HPGe), respectively. The concentra-tion of heavy metals investigated ranges: Cu – 12.9–27.3 mg·kg-1, Fe – 7944.2–19052.2) mg·kg-1, Mn – 410.9–474) mg·kg-1, Ni – 1.9–13.2) mg·kg-1, Al – 3597–13129.2) mg·kg-1, Zn – 195.2–281.7) mg·kg-1, Pb – 0.7–4.5) mg·kg-1 and As – 2.7–11.3) mg·kg-1. The result revealed that, the concentration level of heavy metals (Cu, Fe, Ni, As, and Pb) are below the permissible level while concentration level for Zn has high concentration compared to permissible level limit. However, the activ- ity concentration of radionuclides 226Ra, 232Th and 40K were ranging from 311 to 7,606 Bqkg-1, 207 to 654 Bqkg-1 and 131 to 762 Bqkg-1, respectively. The reported results of activity concentration of radionuclides are found to be higher compared to the recommended world value. The study results will be used as a guide for decision making in addressing problems observed in phosphate tailings, including radiation safety standards for workers and envi- ronmental systems in phosphate mines
Assessment of water quality variation in rivers through comparative index technique and its reliability for decision making
(Tanzania Journal of Science, 2018) Kitalika, Aldo; Machunda, Revocatus; Komakech, Hans; Njau, Karoli
The National Sanitation Foundation (NSF) and Weighed Arithmetic Index (WAI) methods for water quality index (WQI) have been studied to evaluate their reliability in water quality assessment in rivers. Water samples were collected in various GPS predetermined points in Temi, Nduruma, Tengeru and Maji ya Chai rivers-Tanzania during wet and dry seasons and were analyzed for several water quality parameters using standard methods as per APHA. Medium to excellent water qualities were observed for pristine environment in three rivers except Maji ya Chai under NSF and WIA methods, respectively. Excellent water quality was observed in the pristine environment of Temi and Tengeru rivers during wet season. Maji ya Chai water was identified unsuitable for drinking throughout the year. Fecal Coliforms (FC), Nutrients content, BOD and Fluorides (F- ) were the major contributors to the poor water quality in Maji ya Chai whereas FC and Nutrients were a serious problem in flood-plain for other rivers. The two methods showed different overall Water Quality Indices using the same data thus, making them unreliable tools for water quality assessment when used simultaneously for the same purpose. Therefore selection of the method for water quality assessment and decision making may depend on the water use.
Biomass-based carbon electrode materials for capacitive deionization: a review
(Springer Nature Switzerland AG., 2019-06-27) Elisadiki, Joyce; Kibona, Talam; Machunda, Revocatus; Saleem, Muhammad; Kim, Woo-Seung; Jande, Yusufu
Capacitive deionization (CDI) is a promising water purification technology which works by removing salt ions or charged species from aqueous solutions. Currently, most of the research on CDI focuses on the desalination of water with low or moderate salt concentration due to the low salt adsorption capacity of the electrodes. The electrosorption capacity of CDI relies on the structural and textural characteristics of the electrode materials. The cost of electrode materials, the complicated synthesis methods, and the environmental concerns arising from material synthesis steps hinder the development of large-scale CDI units. By considering the good electrical conductivity, high specific surface area (SSA), porous structure, availability, mass production, and cost, porous carbon derived from biomass materials may be a promising CDI electrode material. This review presents an update on carbon nanomaterials derived from various biomasses for CDI electrodes. It covers different synthesis methods and the electrosorption performance of each material and discusses the impact of the SSA and porous structure of the materials on desalination. This review shows that a variety of biomass materials can be used to synthesize cost-effective CDI electrode materials with different structures and good desalination performance. It also shows that diverse precursors and synthesis routes have significant influences on the properties and performance of the resulting carbon electrodes. Additionally, the performance of CDI does not depend only on BET surface area and pore structure but also on the applied voltage, initial concentration of the feed solution, and mass, as well as the capacitance of the electrodes.
Building partnership for participatory sanitation and hygiene planning: lessons and experience from Tanzania
(WEDC International Conference, 2018-10-29) Beale, Jaanne; Banzi, Joseph; Machunda, Revocatus; Shana, Edward; Kisaka, A
Capacitive deionization for water desalination using Na3Fe2(PO4)3/activated carbon composite electrodes
(Elsevier, 2025-05-28) Sufiani, Omari; Alfredy, Tusekile; Tanaka, Hideki; Teshima, Katsuya; Machunda, Revocatus; Jande, Yusufu
Water desalination technologies are attracting growing global attention as critical solutions to address water scarcity torturing mankind worldwide. Capacitive deionization (CDI) is an emerging desalination technology that offers multiple advantages, including low voltage operation and diverse material options for electrode synthesis. In this work the Na3Fe2(PO4)3 (NFP) is composited with the activated carbon (AC) to synthesize AC/NFP composites and tested in water desalination. The characterization results from several techniques reveal the successful composite synthesis. When tested in CDI experiments for brackish water desalination much higher salt removal capacity of around 22.0 was attained by AC/NFP 1:2 compared with 18.65 mg/g of AC electrode. Also, the synthesized AC/NFP 1:2 retain satisfactorily performance efficiency when cycled for twenty runs. However, owing to low resistance at the electrode-electrolyte interface the AC is more energy efficient as it exhibits much low energy consumption of about 0.056 kWh/m3 compared with the AC/NFP 1:2 cell attained 0.15 kWh/m3. This study reveals a trade-off between performance and efficiency: while the AC/NFP 1:2 cell exhibits higher salt removal capacity, it consumes significantly more energy than the AC electrode, which demonstrate superior energy efficiency.
Capacitive deionization: Capacitor and battery materials, applications and future prospects
(Elsevier, 2024-09-15) Sufiani, Omari; Tanaka, Hideki; Teshima, Katsuya; Machunda, Revocatus; Jande, Yusufu
Water scarcity all over the world attracts alternative methods to purify saline water and supplement the available dwindling freshwater resources. Capacitive deionization (CDI) is hopeful to supply water to the population due to operation at low potential along with low energy expenditure when low salinity (5 mM NaCl) feed water solutions are desalinated. Electrode material is the main controlling factor in CDI system and a lot of efforts are devoted to develop excellent materials for better CDI performance. So far, carbon materials are widely used as the electrode for CDI, though limitations such as co-ion expulsion and faradaic reactions hinder their full utilization. Alternatively, battery materials are used since their performance is great due to mitigation of co-ions ejection as well as faradaic reactions. In 2019 our group reviewed factors affecting the performance of activated carbon electrode materials and revealed lack of selectivity, co-ion expulsion, low electrical conductivity and inappropriate pore size distribution to largely contribute to its low salt removal capacity [1]. Therefore, herein, we extend the discussion beyond AC to include other carbons such as aerogels, nanotubes, graphenes etc., and battery materials such as MXenes, sodium super ionic conductors, and BiOCl to mention the few. This article also discusses the extent CDI is applied in the laboratory scale as well as in the field for desalination of real water, wastewater remediation and removal of harmful contaminants to substantiate what it can offer beyond the laboratory experiments. The work is expected to save as a complete reference for the progress of CDI electrode materials and its applications in water purification.
Cattle dung production, management and utilization practices in the smallholding dairy farming systems of East Africa: A situational analysis in Lushoto District, Tanzania
(Journal of Biodiversity and Environmental Sciences, 2018-04-30) Rukiko, Patrick; Machunda, Revocatus; Mtei, Kelvin
This focus review aims to update the dung and manure production, management and utilization in the East African countries and its associated challenges particularly in the case of Lushoto district, in northern Tanzania. Attention and efforts are continuously being made to promote the use of cattle dung though the challenges still exist. Majority of smallholder farmers in the East Africa poorly manage cattle dung such that its quality is impaired. Such practices include exposing the dung uncovered in a heap and applying directly to the crops. A survey conducted at Lushoto district in the smallholder dairy farmers observed poor management from collection of dung, processing or storage to utilization causing losses of potential nutrients when it’s used as manure. Additionally, the knowledge on other uses of cow dung such as for biogas production is not adequately known. This review, therefore, revealed the need for training farmers on issues related to dung management and utilization such as the nutrient recycling at the farm scale. Cattle dung has been for a long time used as manure in agricultural production and recommendations especially on the applications and users have been generalized to a wide range of areas. There is a need to establish area specific recommendation on dung management from production to the final use. For sustainability of the knowledge, readable materials, an appropriate intervention of biogas plant, manure storage (shade structure) and decomposition process that will create awareness from production to farm application are required.
Cattle dung production, management and utilization practices in the smallholding dairy farming systems of East Africa: A situational analysis in Lushoto District, Tanzani
(INNSPUB, 2018-04-30) Rukiko, Patrick; Machunda, Revocatus; Mtei, Kelvin
This focus review aims to update the dung and manure production, management and utilization in the East African countries and its associated challenges particularly in the case of Lushoto district, in northern Tanzania. Attention and efforts are continuously being made to promote the use of cattle dung though the challenges still exist. Majority of smallholder farmers in the East Africa poorly manage cattle dung such that its quality is impaired. Such practices include exposing the dung uncovered in a heap and applying directly to the crops. A survey conducted at Lushoto district in the smallholder dairy farmers observed poor management from collection of dung, processing or storage to utilization causing losses of potential nutrients when it’s used as manure. Additionally, the knowledge on other uses of cow dung such as for biogas production is not adequately known. This review, therefore, revealed the need for training farmers on issues related to dung management and utilization such as the nutrient recycling at the farm scale. Cattle dung has been for a long time used as manure in agricultural production and recommendations especially on the applications and users have been generalized to a wide range of areas. There is a need to establish area specific recommendation on dung management from production to the final use. For sustainability of the knowledge, readable materials, an appropriate intervention of biogas plant, manure storage (shade structure) and decomposition process that will create awareness from production to farm application are required.
Cockle (Anadara granosa) shells-based hydroxyapatite and its potential for defluoridation of drinking water
(Elsevier, 2022-03-03) Mtavangu, Stanslaus; Mahene, Wilson; Machunda, Revocatus; Bruggen, Bart; Njau, Karoli
The present study describes the synthesis and characterization of a hydroxyapatite (HAp)-based adsorbent derived from biogenic cockle (Anadara granosa) shells for the defluoridation of drinking water. The raw cockle shells and synthesized HAp were characterized by X-ray fluorescence spectroscopy (XRF), attenuated total reflection-Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopes-energy dispersive X-ray (FESEM-EDX) and Brunauer-Emmett-Teller (BET) surface area analysis. As demonstrated by FTIR, cockle shells were found to be composed of calcium carbonate (97.4%), an aragonite polymorphous type of carbonate mineral. XRD and SEM analysis supported the formation of a nanocrystalline HAp with an average crystal size of 19.08 nm and 57.1 nm, respectively, with a surface area of 105.8 m2/g and a pore size of 5.6 nm, as depicted by BET. Batch adsorption experiments were conducted using the Box-Behnken design (BBD) with five input parameters: adsorbent dose (2–10 g/L), initial fluoride concentration (10–80 mg/L), contact time (0.5–24 h), reaction temperature (303–333 K), and pH. (3–11). BBD revealed the following optimum conditions: adsorbent dose (6 g/L), initial fluoride concentration (45 mg/L), contact period 12.25 h, reaction temperature (303 K), and pH 3. Experimentally, the adsorption of fluoride on HAp fitted well with the non-linear Langmuir isotherm and linear pseudo-second order kinetics, signifying the chemisorption process. A maximum adsorption capacity (qm) of 15.374 mg/g, which is closer to the experimental value of 14.053 mg/g, was presented by the Langmuir isotherm. Thermodynamically, the adsorption process was spontaneous, endothermic, and stable in nature. The defluoridation mechanism was through electrostatic attraction, ion exchange, hydrogen bonding, and precipitation. Furthermore, the synthesized HAp and bone char were used to examine their efficacy in defluoridating field water: HAp performed better at natural pH, where the treated water met WHO and TBS standards, whereas bone char had insufficient fluoride removal, especially at high fluoride levels. As a result, this study suggests that HAp derived from Anadara granosa shells could be a viable adsorbent for the defluoridation of drinking water.
Cockle (Anadara granosa) shells-based hydroxyapatite and its potential for defluoridation of drinking water
(Elsevier, 2022-02-27) Mtavangu, Stanslaus; Mahene, Wilson; Machunda, Revocatus; Bruggen, Bart; Njau, Karoli
The present study describes the synthesis and characterization of a hydroxyapatite (HAp)-based adsorbent derived from biogenic cockle (Anadara granosa) shells for the defluoridation of drinking water. The raw cockle shells and synthesized HAp were characterized by X-ray fluorescence spectroscopy (XRF), attenuated total reflection-Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopes-energy dispersive X-ray (FESEM-EDX) and Brunauer-Emmett-Teller (BET) surface area analysis. As demonstrated by FTIR, cockle shells were found to be composed of calcium carbonate (97.4%), an aragonite polymorphous type of carbonate mineral. XRD and SEM analysis supported the formation of a nanocrystalline HAp with an average crystal size of 19.08 nm and 57.1 nm, respectively, with a surface area of 105.8 m2/g and a pore size of 5.6 nm, as depicted by BET. Batch adsorption experiments were conducted using the Box-Behnken design (BBD) with five input parameters: adsorbent dose (2–10 g/L), initial fluoride concentration (10–80 mg/L), contact time (0.5–24 h), reaction temperature (303–333 K), and pH. (3–11). BBD revealed the following opti- mum conditions: adsorbent dose (6 g/L), initial fluoride concentration (45 mg/L), contact period 12.25 h, re- action temperature (303 K), and pH 3. Experimentally, the adsorption of fluoride on HAp fitted well with the non-linear Langmuir isotherm and linear pseudo-second order kinetics, signifying the chemisorption process. A maximum adsorption capacity (qm) of 15.374 mg/g, which is closer to the experimental value of 14.053 mg/g, was presented by the Langmuir isotherm. Thermodynamically, the adsorption process was spontaneous, endo- thermic, and stable in nature. The defluoridation mechanism was through electrostatic attraction, ion exchange, hydrogen bonding, and precipitation. Furthermore, the synthesized HAp and bone char were used to examine their efficacy in defluoridating field water: HAp performed better at natural pH, where the treated water met WHO and TBS standards, whereas bone char had insufficient fluoride removal, especially at high fluoride levels. As a result, this study suggests that HAp derived from Anadara granosa shells could be a viable adsorbent for the defluoridation of drinking water.
Combatting toxic chemical elements pollution for Sub-Saharan Africa's ecological health
(Elsevier, 2025-02-08) Ripanda, Asha; Hossein, Miraji; Rwiza, Mwemezi; Nyanza, Elias; Selemani, Juma; Nkrumah, Salma; Bakari, Ramadhani; Alfred, Mateso; Machunda, Revocatus; Vuai, Said
With its booming mining, processing industries, agriculture, and increasing urbanization, sub-Saharan Africa experiences an alarming rise in accumulation of toxic chemical elements in all environmental matrices threatening entire ecology. Most toxic chemical elements are mercury, lead, cadmium, chromium, and arsenic. These toxic chemical elements are known human carcinogens, systemic toxicants and can induce multiple organ damage. The occurrences of toxic chemical elements in Sub-Saharan Africa are amplified by anthropogenic activities such as mining, industrial discharges, and agricultural practices. This study examined the extent of exposure to toxic chemical elements in surface and underground waters, sediments, soils, effluents, food crops, vegetables, aquatic organisms, industrial products, humans, and other animals in Sub-Saharan Africa. Results indicate occurrences of toxic chemical elements in surface and underground waters, sediments, soils, effluents, food crops, vegetables, aquatic organisms, industrial products, humans, and other animals above the recommended threshold. These findings highlight the persistent pollution of water, soil, sediments, food crops, aquatic organisms, and even industrial products, emphasizing the potential for bioaccumulation and exposure through the food chain. This requires interdisciplinary approaches, including updating and enforcing stricter regulations tailored to regional industrial and agricultural practices. Advanced remediation technologies, such as phytoremediation, and bioremediation, should be prioritized to remove toxic chemical elements from affected environments. Additionally, promoting sustainable practices, such as waste recycling programs, can help reduce anthropogenic contributions, strengthen environmental monitoring systems, nurture community awareness, and essentially encourage regional and international collaboration to protect ecosystems and safeguard human health in Sub-Saharan Africa.