Publications by authors named "Fredrick Kengara"

The project aimed to develop porous materials for sustainable energy applications, namely, hydrogen storage, and valorization of biomass to renewable fuels. At the core of the project was a training programme for Africa-based researchers in (i) the exploitation of renewable locally available raw materials; (ii) the use of advanced state-of-the-art techniques for the design and synthesis of porous materials (zeolites and metal-organic frameworks (MOFs)) for energy storage; and (iii) the valorization of sustainable low-value feedstock to renewable fuels. We found that compaction of the UiO-66 MOF at high pressure improves volumetric hydrogen storage capacity without any loss in gravimetric uptake, and experimentally demonstrated the temperature-dependent dynamic behaviour of UiO-66, which allowed us to propose an activation temperature of ≤ 150°C for UiO-66.

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Fast and real-time detection of trace Hg(Ⅱ) by fluorescent probes under acidic conditions is urgently required due to the high toxicity and accessibility to creatures and human being. However, fluorescent probes for Hg(Ⅱ) detection in environmental samples are rarely reported due to the protonation potential of acidic mercury sources. In this study, the SD probe was developed by 5-(p-dimethylaminobenzylidene) rhodanine (DMABR) loaded on sepiolite by hydrothermal treatment, and showed excellent Hg(Ⅱ) detection performances for mercury sources at pH 4-10 due to buffering ability of the hyperconjugated lactam rings.

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Article Synopsis
  • - The study investigated how human activities and seasonal changes affect the water quality and heavy metal concentrations in River Yala (RY) in the Lake Victoria basin by analyzing various physico-chemical parameters and ecological risks across different agricultural sites during both dry and wet seasons.
  • - Sample analysis revealed significant variability in parameters like electrical conductivity, turbidity, and heavy metal levels, with water and sediment data differing between pristine upstream areas and various agricultural farms, indicating a potential pollution impact from farming activities.
  • - The results showed that the wet season generally had a more pronounced effect on the levels of contaminants compared to the dry season, and specific heavy metals exhibited distinct correlations based on seasonal conditions, highlighting the importance of monitoring these factors for ecological health.
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Article Synopsis
  • * It identifies that soil properties such as pH and dissolved organic carbon play a more crucial role in shaping microbial diversity than OCs themselves, although both factors are important.
  • * Significant differences in microbial composition between top and subsoils were found, with heavily contaminated subsoils showing closer and more complex bacterial interactions, illustrating the environmental influences on microbial community structures.
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The continued frequent detection of pharmaceuticals in the environment is of major concern due to potential human and ecological risks. This study evaluated 30 antibiotics from 8 classes: sulphonamides (SAs), penicillins (PNs), fluoroquinolones (FQs), macrolides (MLs), lincosamides (LINs), nitroimidazoles (NIs), diaminopyrimidines (DAPs), salfones and 4 anthelmintics benzimidazoles (BZs) in surface water and sediments from River Sosiani in Eldoret, Kenya. Samples were collected during the wet and dry seasons and subjected to solid phase extraction using HLB cartridges.

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Microplastics (MPs) can enter plants through the foliar pathway and are potential hazards to ecosystems and human health. However, studies related to the molecular mechanisms underlying the impact of foliar exposure to differently charged MPs to leafy vegetables are limited. Because the surfaces of MPs in the environment are often charged, we explored the uptake pathways, accumulation concentration of MPs, physiological responses, and molecular mechanisms of lettuce foliarly exposed to MPs carrying positive (MP) and negative charges (MP).

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Biodiesel is an alternative renewable green fuel obtainable from the reaction of plant or animal oil with a low molecular weight alcohol in the presence of a catalyst. However, the cost of its production remains high due to costly feedstock, the majority of which is competitively also used as food, and the use of homogeneous catalysts, which pose difficulties in product purification and resulting environmental pollution. The aim of this study was to explore the production of biodiesel through transesterification of non-edible and cheap (JC) oil using a zeolite Na-X catalyst obtained from naturally occurring kaolin clay.

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Objectives: Despite the quantum of research findings on tobacco epidemic, a review on the formation characteristics of nicotine, aldehydes and phenols, and their associated etiological risks is still limited in literature. Accordingly, knowledge on the chemical properties and free radical formation during tobacco burning is an important subject towards unravelling the relationship between smoking behaviour and disease. This review investigates how scientific efforts have been advanced towards understanding the release of molecular products from the thermal degradation of tobacco, and harm reduction strategies among cigarette smokers in general.

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Artificial intelligence (AI) coupled with promising machine learning (ML) techniques well known from computer science is broadly affecting many aspects of various fields including science and technology, industry, and even our day-to-day life. The ML techniques have been developed to analyze high-throughput data with a view to obtaining useful insights, categorizing, predicting, and making evidence-based decisions in novel ways, which will promote the growth of novel applications and fuel the sustainable booming of AI. This paper undertakes a comprehensive survey on the development and application of AI in different aspects of fundamental sciences, including information science, mathematics, medical science, materials science, geoscience, life science, physics, and chemistry.

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The polycyclic aromatic hydrocarbons (PAHs) that enter the aqueous phase usually coexist with fulvic acid (FA). Therefore, we initiated this investigation to explore the influences of FA on bacterial biofilm formation and its potential to biodegrade pyrene (PYR), using electron microscopic techniques and isobaric tags for relative and absolute quantification (iTRAQ). Our results revealed that FA stimulated biofilm formation and enhanced the biodegradation of PYR.

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Fe content and distribution on montmorillonite would probably enhance its sorption capacity for hydrophobic organic pollutants. Thus, Fe modified montmorillonites with different ratios of FeSO·7HO and Ca-montmorillonite were prepared. The results indicated that γ-FeO nanoparticles were not only generated at the montmorillonite surfaces, but that the γ-FeO also extended the edges of montmorillonite surfaces.

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Aim: The economic burden caused by death and disease in the world is credited mainly to tobacco use-currently linked to approximately 8,000,000 deaths per year with approximately 80% of these faralities reported in low and middle income economies. The World Health Organization (WHO) estimates that nearly 7,000,000 deaths are attributed to direct tobacco use, while approximately 1,200,000 non-smokers exposed to second hand cigarette smoke die every year. Accordingly, tobacco use is a major threat to the public health infrastructure; therefore, proper cessation interventions must be put in place to curb tobacco abuse and ease economic and social burdens caused by the tobacco epidemic.

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DDT and its main metabolites (DDTs) are still the residual contaminants in soil. Sequential anaerobic-aerobic cycling has long been approved for enhancing the degradation of DDTs in soil. However, there is a lack of study investigating whether anaerobic-aerobic cycling would enhance the mineralization of DDT, and what a kind of anaerobic-aerobic management regimes would be optimal.

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DDT transformation to DDD in soil is the most commonly reported pathway under anaerobic conditions. A few instances of DDT conversion to products other than DDD/DDE have been reported under aerobic conditions and hardly any under anaerobic conditions. In particular, few reports exist on the anaerobic degradation of DDT in African tropical soils, despite DDT contamination arising from obsolete pesticide stockpiles in the continent as well as new contamination from DDT use for mosquito and tsetse fly control.

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It has recently been demonstrated that the addition of nanoscale zero-valent iron (nZVI) to oxygen-containing water or soil aquifers results in the oxidation of organic compounds. However, there has been little insight about the generation of the reactive oxygen species (ROS) that play a vital role in the transformation of contaminants in the presence of nZVI. This study investigated (i) the degradation of 2-chlorobiphenyl (2-CB) by nZVI; (ii) the generation and role of ROS in this process.

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Mau Forest in the upper reaches of the Mara River basin has recently undergone increased forest destruction followed by human settlement and agricultural activities. These anthropogenic activities may be contributing nutrients and heavy metals, ultimately polluting the river water and eventually Lake Victoria water hence damaging these aquatic ecosystems. This study sought to establish the effect of anthropogenic activities and season on the water quality of the Amala and Nyangores tributaries of the River Mara in Kenya.

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Co-contaminated soils by organic pollutants (OPs), antibiotics and antibiotic resistance genes (ARGs) have been becoming an emerging problem. However, it is unclear if an interaction exists between mixed pollutants and ARG abundance. Therefore, the potential relationship between OP contents and ARG and class 1 integron-integrase gene (intI1) abundance was investigated from seven dairy farms in Nanjing, Eastern China.

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Soils are exposed to various types of chemical contaminants due to anthropogenic activities; however, research on persistent organic pollutants and the existence of antibiotic resistance genes (ARGs) is limited. To our knowledge, the present work for the first time focused on the bioremediation of soil co-contaminated with pyrene and tetracycline/sulfonamide-resistance genes. After 90 days of incubation, the pyrene concentration and the abundance of the four ARGs (tetW, tetM, sulI, and sulII) significantly decreased in different treatment conditions (p<0.

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The objective of the study was to elucidate the biotic and abiotic processes under dissimilatory iron reducing conditions involved in reductive dechlorination and iron reduction. DDT transformation was investigated in cultures of Shewanella putrefaciens 200 with/without α-FeOOH. A modified first-order kinetics model was developed and described DDT transformation well.

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The objective of this study is to compare the efficacies of powder activated carbon (PAC) and granular activated carbon (GAC) as amendments for the immobilization of volatile compounds in soil. Soil artificially-spiked with chlorobenzenes (CBs) was amended with either PAC or GAC to obtain an application rate of 1%. The results showed that the dissipation and volatilization of CBs from the amended soil significantly decreased compared to the unamended soil.

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An innovative ex situ soil washing technology was developed to remediate polybrominated diphenyl ethers (PBDEs) and heavy metals in an electronic waste site. Elevated temperature (50 °C) in combination with ultrasonication (40 kHz, 20 min) at 5.0 mL L(-1) sunflower oil and 2.

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Polycyclic aromatic hydrocarbons (PAHs)/heavy metals/fluorine (F) mixed-contaminated sites caused by abandoned metallurgic plants are receiving wide attention. To address the associated environmental problems, this study was initiated to investigate the feasibility of using carboxymethyl-β-cyclodextrin (CMCD) and carboxymethyl chitosan (CMC) solution to enhance ex situ soil washing for extracting mixed contaminants. Further, Tenax extraction method was combined with a first-three-compartment model to evaluate the environmental risk of residual PAHs in washed soil.

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An innovative ex situ soil washing technology was developed in this study to remediate organochlorine pesticides (OCPs) and heavy metals in a mixed contaminated site. Elevated temperature (60 °C) combined with ultrasonication (40 kHz, 20 min) at 50 mL L(-1) maize oil and 45 g L(-1) carboxylmethyl-β-cyclodextrin were effective in extracting pollutants from the soil. After two successive washing cycles, the removal efficiency rates for total OCPs, mirex, endosulfans, chlordanes, Cd, and Pb were approximately 94.

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The present study was conducted to investigate the anaerobic biodegradation potential of biostimulation by nitrate (KNO3) and methyl-β-cyclodextrin (MCD) addition on an aged organochlorine pesticide (OCP)-contaminated paddy soil. After 180 days of incubation, total OCP biodegradation was highest in soil receiving the addition of nitrate and MCD simultaneously and then followed by nitrate addition, MCD addition, and control. The highest biodegradation of chlordanes, hexachlorocyclohexanes, endosulfans, and total OCPs was 74.

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An innovative ex situ soil washing technology was developed in this study to remediate organochlorine pesticides (OCPs)-contaminated site. Elevated temperature (50 °C) combined with ultrasonication (35 kHz, 30 min) at 25 g L(-1) methyl-β-cyclodextrin and 100 mL L(-1) sunflower oil were effective in extracting OCPs from the soil. After four successive washing cycles, the removal efficiency for total OCPs, DDTs, endosulfans, 1,2,3,4,5,6-hexachlorocyclohexanes, heptachlors, and chlordanes were all about 99%.

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