Browsing by Author "Kasambala, Hildegard"

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Agro-Waste-Derived Hybrid Biochar Exhibits High-Efficiency Removal of Endocrine-Disrupting Compounds
(Springer International Publishing, 2025-04-11) Kasambala, Hildegard; Rwiza, Mwemezi; Mpumi, Nelson; Mwema, Mwema; Njau, Karoli
Poor waste management of the products and products used in water sources becomes a problem for living organisms’ health. Using biosorbent from agro-waste materials becomes the solution for waste management and wastewater treatment. This study investigated the removal of progesterone from aqueous solutions using a biochar adsorbent derived from mixed banana and mango peels. The biosorbent shows high progesterone removal of 97.8 ± 0.02% at 700℃ preparation temperature at an optimal biosorbent concentration of 0.50 g and pH of 8. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Isotherm analysis revealed that the adsorption data best fitted the Freundlich model (R2 = 0.96), with a maximum adsorption capacity (qmax) of 307 mg g−1, indicating multilayer adsorption with a heterogeneous surface. The Brunauer–Emmett–Teller (BET) surface area was 652 m2g−1 with abundant functional groups verified by Fourier Transform Infrared Spectroscopy (FTIR). The Scanning Electron Microscopy image (SEM) indicated that the biochar is porous, contributing to its effectiveness as an adsorbent. Thermodynamics results indicate that the spontaneous nature of adsorption reveals the process. The findings proved the potential of using agricultural mixed waste-derived biochar containing various chemical and physical characteristics as an effective and sustainable adsorbent to remove endocrine disruptors. This technique addresses environmental concerns about water hormone pollution and promotes sustainable waste management practices, but the gradual decrease in adsorption efficiency highlights the importance of optimizing the biochar's chemical composition and structural reliability to maximize its performance.
Assessment of levels and distribution of progesterone in receiving waters and wastewaters in the vicinity of Arusha city,Tanzania
(NM-AIST, 2020-12) Kasambala, Hildegard
This study aimed at investigating the levels and distribution of progesterone in receiving waters and wastewaters in Arusha, a fast-growing urban area and third largest city in Tanzania. Also, intend to assess the efficiency of waste stabilisation ponds (WSP) and constructed wetland (CW) in removing progesterone. The study was conducted along the Themi River, (WSPs) and CW. Progesterone was detected and quantified by using an Enzyme-Linked Immunosorbent Assay (ELISA) kit. For Themi River samples, the level of progesterone obtained ranged from ‘no detection’ to 439.00 ng/L with a mean value of 120.30 ng/L. The levels detected were significantly higher in the midstream three times and seven times than upstream and downstream, respectively (P ˂ 0.05). Progesterone was spatially distributed much at midstream than upstream and downstream. The elevated values at midstream were attributable to livestock, WSPs and household effluents; agricultural activities; and sewage infiltration. WSPs were observed to release 215 ng/L of progesterone at effluent with zero progesterone detected at the effluent from CW with a removal efficiency of 75% and 100% for WSP and CW, respectively. Although progesterone removal efficiency was high, the amount released was still high enough to cause harm to aquatic organisms. Progesterone levels in the present study, although not extremely high, correspond to those associated with harmful effects in other studies. Therefore, this study suggests that anthropogenic activities conducted nearby the rivers should be strictly avoided to reduce the amount of progesterone to be released to the river.
Biochars derived from banana and mango peels in isolated systems revealed high removal efficiency of endocrine-disrupting compounds from water.
(Springer Nature, 2024-10-01) Kasambala, Hildegard; Rwiza, Mwemezi; Mpumi, Nelson; Mwema, Mwema Felix; Njau, Karoli
This study investigated the effectiveness of biochar derived from banana and disrupting endocrine-disrupting compounds (EDCs) from water in isolated systems. The study aimed to provide an eco-friendly solution for water purification using agricultural waste products. Banana and mango peels were dried, ground, and calcinated at 300, 550, and 700 °C temperatures. The biochar was tested through a batch adsorption experiment for the removal of progesterone, and the remaining progesterone was analyzed using high-performance liquid chromatography (HPLC). Results indicated that the banana peel biochar (BPB) and mango peel biochar (MPB) achieved the highest adsorption capacities of 92.8 and 87.9%, respectively, when subjected to pyrolysis at 700 °C. The effect of other factors on adsorbent efficiency and its characteristics were subsequently analyzed by biochar calcinated at 700 °C. Results indicate that as the concentration of adsorbent increases, the adsorption efficiency increases while the adsorption capacity decreases. The Langmuir model fits better in BPB, while the Freundlich model fits better in MPB. The maximum adsorption capacities of the Langmuir model were 43.42 and 37.80 mg of progesterone per g of BPB and MPB, respectively. The scanning electron microscopy image (SEM) showed that biochar from 700 °C presents higher porosities than biochar. The Brunauer–Emmett–Teller (BET) showed that both biochars had high surface area and equal pore volume. Therefore, the study suggests that BPB and MPB are the best eco-friendly agricultural waste materials for development of sustainable water treatment technologies for removal of EDCs from water.
A comprehensive review on the distribution of per- and poly-fluoroalkyl substances in the environment across Sub-Saharan Africa revealed significant variation in their concentrations
(Elsevier, 2024-08) Kasambala, Hildegard; Rwiza, Mwemezi; Mpumi, Nelson; Mwema, Mwema; Machunda, Revocatus; Mtei, Kelvin; Njau, Karoli
Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals known for their widespread use in various industrial and consumer products. They enter the food chain via contaminated water, air, and soil, resulting in bioaccumulation in plants, fishes, foods, human milk, and blood serum. Here, we critically reviewed the literature published from 2005 to 2021 on the occurrence and distribution of Perfluorooctanoic acid (PFOA) and perfluoro-octane sulfonate (PFOS) as the most occurring PFAS in the aquatic environment in sub-Saharan Africa (SSA). To our knowledge, this is the first paper to review the status of PFAS in the SSA environment. This review found that almost all matrices studied in SSA regions have been polluted by PFAS with varying concentrations. This information suggests that the levels of PFAS in the environment deserve immediate attention. Furthermore, SSA faces unique challenges in understanding and managing PFAS contamination due to the scarcity of data in specific regions and the need for more administrative guidelines for monitoring PFAS in water. This review provides vital baseline information on the occurrences, distribution and contributing factors for their distribution in the SSA environment for better understanding to protect the environment and public health, and to develop sustainable solutions for the PFAS growing concern.
Dust exposure and its health implications to miners in Mererani artisanal and small-scale mining industry
(Taylor & Francis, 2025-01) Mumba, Edward; Selemani, Juma; Kasambala, Hildegard; Bidu, Jerome; Ripanda, Asha; Rwiza, Mwemezi
This study aimed to identify and quantify the total dust exposure to underground miners in Mererani, Tanzania, and its composition to generate evidence for informed decision- and policy-making. The Analytical Air Monitoring System (AMS) was used for dust collection, and analysis was conducted gravimetrically. The dust composition was analysed using Inductively Coupled Plasma Optical Emission Spectroscopy. The results showed significant variation in dust exposure levels across different mining zones, with miners inhaling up to 1859 mg of dust over an 8-hour period in drilling zones (DZ), 797 mg in loading zones (LZ), and 382 mg in resting zones (RZ). The mean value of dust exposure was significantly different, with a p-value of <0.05. Miners had higher levels of heavy metal and silica than those from unmined sites, with chromium being the most dominant element across all samples. Cumulative exposure to dust over time is linked to long-term respiratory impairment and serious health conditions such as lung cancer. These findings highlight the need for intervention, including education on dust hazards, provision of personal protective equipment (PPE), and enforcement of safety standards to safeguard miners’ health. Addressing these issues is critical to promoting policy reforms and sustainable mining practices in Mererani and similar communities.