Browsing by Author "Mwakalesi, Alinanuswe J."

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Contamination and health risk assessment of heavy metals in selected highly edible fish species from lake Nyasa, Tanzania
(Springer, 2023-04) Mwambene, Bupoki; Mwakalesi, Alinanuswe J.; Nehemia, Alex Nahnson
Heavy metal contamination emanating from increased industrial and anthropogenic activities poses considerable environmen- tal risks to water resources, aquatic biodiversity, and human health. These metals are major sources of various unfavorable environmental changes and human health hazards. This research investigated the potential contamination level and health risk assessment of heavy metals (Fe, Zn, Ni, Cu and Cr) in five highly edible fishes (O. microlepis, C. gariepinus, O.niloticus, R. moorii,B. meridionalis) from Lake Nyasa. The results indicated that gills contained higher amounts of heavy metals compared to muscles. The levels of Fe and Zn were higher in the gills of C. gariepinus and O.niloticus than O. microlepis, R. moorii, and B. meridionalis. Similarly, amounts of Cu and Cr were higher in the gills of C. gariepinus and O. microlepis. The general trend of heavy metal concentrations accumulated in selected fish species was Fe > Zn > Ni > Cu > Cr. The amounts of heavy metals found in the fish samples were within acceptable limits set by FAO and WHO. Furthermore, the risk assessments indicated that the current exposure levels are unlikely to cause serious health risks. However, the progressive monitoring of levels of heavy metals in various aquatic organisms from Lake Nyasa is important for the continued protection of human health against hazardous health effects.
Corrosion inhibition of Amino Pentadecylphenols (APPs) derived from Cashew Nut shell liquid on mild steel in Acidic medium
(Scientific Research Publishing Inc., 2016-08) Philip, Joseph Yoeza Naimani; Buchweshaija, Joseph; Mwakalesi, Alinanuswe J.
In this study, corrosion inhibiting properties of amino pentadecylphenols (APPs) derived from Cashew Nut Shell Liquid (CNSL) on mild steel in aerated 0.10 M HCl at 303 K were studied using Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization measurements. Both methods indicated the potential of a mixture of amino pentadecyphenols to serve as a corro- sion inhibitor in mild steel in 0.10 M HCl. Corrosion inhibition efficiencies were observed to in- crease with increase in the inhibitor concentration, with maximum corrosion inhibition of about 98% at inhibitor concentration of 600 ppm. The adsorption of the inhibitor on mild steel surface was found to obey Temkin adsorption isotherm, signifying physical adsorption of the inhibitor molecules on mild steel surface.
Corrosion inhibition of mild steel in sulphuric acid solution with tetradenia riparia leaves aqueous extract: kinetics and thermodynamics
(ResearchGate, 2022-01-23) Mwakalesi, Alinanuswe J.
One of the most successful ways for maximizing profit and lowering costs is to use mild steel over other corrosion-resistant alloys. As a result, mild steel is the most commonly used metallic material in many industries, and its corrosion resistance has received a lot of attention. The mild steel corrosion inhibition using compounds derived from plants is the most practicable and preferable technique because of their linked low cost and green chemistry credentials. This study reports on the kinetics and thermodynamics of mild steel corrosion inhibition in sulphuric acid media utilizing Tetradenia riparia leaves aqueous extract as a potential green inhibitor. The investigations were carried out using the gasometric technique. The findings indicated that the corrosion inhibition efficiency (IE) increased with increasing inhibitor concentration with an optimal value of 90.6% at 500-ppm. The increase in temperature 298 to 338 K lowered the corrosion inhibition efficiency by only 4%. The adsorption kinetics of the extract on the mild steel fit into Langmuir, Temkin, EL-awady, and Freundlich models, but the Langmuir was the best. The results of this investigation show that adsorption of the extracted chemicals on mild steel in a sulphuric acid solution is feasible and most likely involves a combination of physical and chemical adsorption.
Effective corrosion inhibition of mild steel in an acidic environment using an aqueous extract of Macadamia Nut Green Peel biowaste
(MDPI, 2022-12) Mwakalesi, Alinanuswe J.; Nyangi, Magori
Improving the corrosion resistance of mild steel in an acidic aqueous environment is an important industrial consideration due to the use of acids for descaling and cleaning. The application of corrosion inhibitors is one of the most effective and economical means of protecting metals against corrosion. Plant-derived compounds have recently gained attention due to their low cost, non-toxic, and environmentally friendly properties. Biowastes are recognized as a potential cheap source of green corrosion inhibitors, and their use can help to lower the costs associated with corrosion inhibitors. Green peel biowaste (GPBW) generated from macadamia nut processing is typically dumped into the environment, posing a disposal concern. The use of the waste as a potential source of organic compounds with green chemistry attributes for mild steel corrosion inhibition in an acidic solution was proposed in this study. The gasometric and optical methods were used to carry out the investigations. Results showed that mild steel corrosion rates decreased as extract concentrations increased. As a result, mild steel corrosion inhibition increased with increasing inhibitor concentration and reached a peak value of 81% at 0.5 g/L extract concentration. The optical images showed that the inhibitor molecules adsorbed on the metal surface to form a protective film that isolated the mild steel from the corrosive solution. The adsorption of inhibitor molecules on the mild steel surface followed the Langmuir adsorption isotherm, indicating the formation of a monolayer film with a homogeneous distribution of adsorbed molecules. A Gibbs free energy (G◦ ads) of 24 kJ/mol indicated the inhibition process was mainly characterized by physical adsorption. The results of this study suggest that aqueous GPBW extract could serve as an inexpensive, non-toxic, and renewable corrosion inhibitor of mild steel in acidic solutions.
Exploiting Ion–Dipole and Ion‑Exchange interactions for the removal of Aminopyridines from aqueous environments using Polymer inclusion membranes
(Springer, 2023-07-12) Mwakalesi, Alinanuswe J.; Potter, Ian D.
Aminopyridines, such as 4-amino-2-chloropyridine (ACP), are not only starting materials for many useful chemicals but also decomposition by-products that are extremely stable in an aqueous environment. Aliquat 336 has proved useful as a car- rier in polymer inclusion membranes (PIMs) for the extraction and transport of small organic anions through ion-exchange processes. However, less attention has been paid to the use of the carrier for the extraction of neutral or cationic organic compounds like aminopyridines. The current study focuses on using PIMs containing Aliquat 336 to target ACP using ion–dipole interactions. The investigations were performed using both experimental methods and computational model- ling. The findings indicated that ACP was transported through a combination of both passive and facilitated diffusion in the rate-determining steps. Significant facilitated transport occurred when PIMs contained 10 wt% or more Aliquat 336. The transport of ACP was fundamentally driven by pH but also benefited from a chloride gradient that resulted in the concurrent transport of orthophosphate. An optimal membrane composition delivered a reasonable flux of 413 (± 9) × 10–8 mol m−2 s−1 and good transport efficiency of 98% for ACP. Our findings provide more incentive for the continued development of PIM chemistry to target troublesome organic pollutants and recover useful chemicals from water sources.
Green synthesis of silver nanoparticles using aqueous extract of vachellia xanthophloea and their potential use for antibacterial and sensing of mercury ions
(Springer, 2023-07-06) Mwakalesi, Alinanuswe J.
The use of silver nanoparticles (Ag-NPs) in different fields such as agriculture, medicine, and environment has recently increased. As a result, studies on their synthesis and applications have gained attention. In the present study, the synthesis of Ag-NPs using cheap, renewable, and environmentally friendly phytochemicals extracted from Vachellia xanthophloea leaves is reported. Additionally, potential uses of the nanoparticles against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria and for sensing of mercury ions from aqueous solutions were investigated. The findings showed that the formation of nanoparticles was associated with a color change from green to brown with a UV–Vis maximal absorbance peak at 420 nm due to surface plasmon resonance on Ag-NPs. The synthesized Ag-NPs showed effec- tive antibacterial effects against both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. The antibacterial effectiveness as indicated by the minimum inhibitory concentration (MIC) was higher for Staphylococcus aureus (0.04 mg/mL) compared to E. coli (0.33 mg/mL). Similarly, the minimum bactericidal concentration (MBC) values were 0.04 and 0.66 mg/mL for S. aureus and E. coli, respectively. The nanoparticles were also sensitive to metal ions ( Hg2+, Ba2+, Mg2+, Zn2+, Cu2+, Ni2+, Co2+, and Fe2+) and showed a remarkable selectivity to mercury. The potential use of the nanoparticles for sensing of mercury ions from real water samples of ground and tap waters produced satisfactory results. The limit of detection (LOD) and limit of quantification (LQD) for sensing of Hg2+ were determined to be 22.2 µM and 73.9 µM, respectively. The findings from the current study indicate that Ag-NPs prepared using Vachellia xanthophloea leaves aqueous extract could serve as effective an antibacterial agent and a sensor of mercury ions for aqueous samples.
Removal of picloram herbicide from an aqueous environment using polymer inclusion membranes
(Elsevier Ltd, 2020-04-06) Mwakalesi, Alinanuswe J.; Potter, Ian D.
The picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) herbicide is widely applied to control the growth of woody plants and it has been frequently detected in aqueous environments due to its poor adsorption by soils and high leaching potential. Consequently, the removal of picloram from contaminated environmental waters is of major concern due to its adverse impacts on aquatic organisms, soils and animals. The development of a method for the extraction and transport of picloram from aqueous solutions using a polymer inclusion membrane (PIM) composed of cellulose triacetate, trioctylmethylammonium chloride (Aliquat 336) and 2–ni- trophenyl octyl ether (NPOE) is reported. The experimental method was optimized for the PIM composition, and the type and concentration of stripping reagent. The optimized method demonstrated good performance in- dicators of flux and transport efficiency for picloram during non-competitive and competitive transport ex- periments. The PIM was also successfully applied in a passive sampling device to recover picloram at the maximum permissable concentration of 500 μg/L from a complex matrix of natural water. Findings from this study demonstrate that PIMs can serve as a potential alternative method for the removal and recovery of pi- cloram and related herbicides from contaminated aqueous solutions.
Targeting of cationic organic pesticide residues using polymer inclusion membranes containing anacardic acid from cashew nut shell liquid as a green carrier
(Elsevier Ltd, 2021-07-21) Mwakalesi, Alinanuswe J.; Potter, Ian D.
Many emerging organic pollutants exist as cationic residues at environmentally relevant pH. This indicates a need to develop economically viable and robust methods to remove such residues from environmental waters. In this paper, we report using polymer inclusion membranes (PIMs) containing anacardic acid (AA), sourced from cashew nut shells, as an acidic carrier for the extraction and transport of 4-amino-2-chloropyridine (ACP), paraquat and diquat as representative target solutes of organic pesticide residues in aqueous solutions. Amounts of cellulose triacetate (CTA) as polymer, 2–nitrophenyl octyl ether (NPOE) as plasticiser, AA as carrier, and 1- dodecanol as modifier were used to prepare membranes. An optimal composition of 30 wt% CTA, 40 wt% NPOE, 10 wt% AA and 20 wt% dodecanol produced an initial flux of 364 (± 16) × 10 − 8 mol m − 2 s − 1 for transport of ACP. The extraction performance of AA was comparable to bis-(2-ethylhexyl) phosphoric acid, a widely used acidic carrier, in PIMs of similar composition. PIMs utilizing AA were also successfully applied to a sample of environmental water for the competitive recovery of ACP, paraquat and diquat, each at 500 μ g/L. Using chemicals from plants as active reagents was shown to be an effective strategy to enhance the green chemistry credentials associated with methods for water remediation.