Browsing by Author "Buchweishaija, Joseph"
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Item Cashew Nut Shell Liquid as an Alternative Corrosion Inhibitor for Carbon Steels.(College of Natural and Applied Sciences, 2001) Philip, Joseph Y. N.; Buchweishaija, Joseph; Mkayula, Lupituko L.Cashew Nut Shell Liquid (CNSL) has been tested as a corrosion inhibitor for carbon steel in 3% aqueous NaCl solution (pH 6) saturated with carbon dioxide gas at 30°C under static conditions using ac-impedance and potentiodynamic polarisation techniques. It was found that CNSL reduces the extent of the electrochemical processes taking place on carbon steel undergoing corrosion. The corrosion rate of the carbon steel was reduced by over 92 % when only 300 ppm of CNSL was applied. This indicates that CNSL is a potential corrosion inhibitor for carbon steels in CO2 environment.Item Cashew Nut Shell Liquid as an Alternative Corrosion Inhibitor for Carbon Steels.(2001) Philip, Joseph Y. N.; Buchweishaija, Joseph; Mkayula, Lupituko L.Cashew Nut Shell Liquid (CNSL) has been tested as a corrosion inhibitor for carbon steel in 3% aqueous NaCl solution (pH 6) saturated with carbon dioxide gas at 30°C under static conditions using ac-impedance and potentiodynamic polarisation techniques. It was found that CNSL reduces the extent of the electrochemical processes taking place on carbon steel undergoing corrosion. The corrosion rate of the carbon steel was reduced by over 92 % when only 300 ppm of CNSL was applied. This indicates that CNSL is a potential corrosion inhibitor for carbon steels in CO2 environment.Item Corrosion Inhibition of Amino Pentadecylphenols (APPs) Derived from Cashew Nut Shell Liquid on Mild Steel in Acidic Medium(Materials Sciences and Applications, 2016-08-05) Philip, Joseph Yoeza Naimani; Buchweishaija, Joseph; Mwakalesi, AlinanusweIn 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 corrosion inhibitor in mild steel in 0.10 M HCl. Corrosion inhibition efficiencies were observed to increase 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.Item Corrosion Inhibition of Amino Pentadecylphenols (APPs) Derived from Cashew Nut Shell Liquid on Mild Steel in Acidic Medium(Scientific Research Publishing, 2016) Philip, Joseph Y. N.; Buchweishaija, Joseph; Mwakalesi, AlinanusweIn 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 corrosion inhibitor in mild steel in 0.10 M HCl. Corrosion inhibition efficiencies were observed to increase 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.Item Corrosion Inhibition of Carbon Steel by an Amine-Fatty Acid in Acidic Solution(2004) Buchweishaija, JosephThe corrosion inhibition of carbon steel in 3% de-aerated NaCl acidic solution with amine–fatty acid corrosion inhibitor, KI384, was investigated at different temperatures using potentiodynamic polarization technique. The Corrosion rate was calculated in the presence and absence of inhibitor. The inhibition increased with an increase in inhibitor concentration and decreased with rise in temperature. The maximum percentage inhibitor efficiency was obtained at 35 oC. The percentage inhibition up to 99% was registered at a concentration of 10 ppm of KI384. The inhibitor acts as a mixed type at lower temperature and predominantly anodic at high temperature. The interrelationship between the surface coverage and concentration of the inhibitor was also studied. It was found that the inhibitor obeys Langmuir adsorption isotherm and adsorbs on the metal surface through physical adsorption.Item The Decomposition Kinetics of Caco 3: The Significance of The Kinetic Triple A, Ea And F(Alpha)(2001-12) Kyobe, J. W. P.; Buchweishaija, Joseph; Akwilapo, Leonard D.; Magufuli, John PombeItem The Influence of Aliphatic Side Chain of Anacardic Acid on Molecular Recognition Properties of Imprinted Polymers(2012) Philip, Joseph Y. N.; Buchweishaija, Joseph; Mkayula, Lupituko L.The objective of this work was to determine the influence of the aliphatic side chain of anacardic acid on molecular recognition properties of imprinted polymers made from anacardanyl methacrylate (AnMcr). Salicylic methacrylate (SaMcr), a structural analog of AnMcr, was synthesized and used as a functional monomer to prepare imprinted polymers for comparison with AnMcr-based polymers. Using divinylbenzene (DVB) as a cross linker and racemic propranolol as a model template, irregular monolithic particles of poly(SaMcr-co-DVB)m were synthesized in toluene, and spherical beads of poly(SaMcr-co-DVB)b and poly(AnMcr-co-DVB)b were synthesized in acetonitrile by precipitation polymerization. Although imprinted irregular monolithic particles, poly(SaMcr-co-DVB)m, tested in toluene containing 0.5% acetic acid, displayed relatively low specific propranolol binding, they showed high molecular selectivity. For the spherical beads tested in acetonitrile, both imprinted poly(AnMcr-co-DVB)b and poly(SaMcrco-DVB)b showed obvious specific propranolol binding despite the use of polar organic solvent during imprinting. Imprinted poly(AnMcr-co-DVB)b showed higher molecular selectivity than imprinted poly(SaMcr-co-DVB)b. Interestingly, the presence of the aliphatic side chain in AnMcr resulted in more uniform imprinted beads as compared to particle agglomerates obtained from SaMcr in the presence of propranolol template. Therefore, the aliphatic side chain of anacardic acid improves both molecular recognition of imprinted polymers as well as the formation of uniform imprinted spherical beads.Item Intra-Species Variation of the Properties of Gum Exudates from Two Acacia Species of the Series Gummiferae(Elsevier, 2008) Mhinzi, G. S.; Mghweno, L. A. R.; Buchweishaija, JosephGum exudates from Acacia drepanolobium and A. kirkii ssp. kirkii var. kirkii from Tanzania have been analyzed and the intra-species variation of their properties evaluated. The results show that inter-species variation of the properties of the gum exudates from the two species exist, whereas only some parameters show intra-species variation. The specific optical rotations of the gum exudates varied from +72.0° to +94.6° for A. drepanolobium and +29.2° to +38.0°, for A. kirkii ssp. kirkii var. kirkii. Likewise, the acid equivalent weights (AEWs) varied from 832 to 1659 for A. drepanolobium and 663 to 1199 for A. kirkii ssp. kirkii var. kirkii. Intra-species variation for the tannin content was also observed for the species studied, whereas no intra-species variation was observed for the nitrogen and methoxyl contents. The results in this study show that the variation of the properties among the batches of commercial Acacia gum may be due to admixture of gums from different Acacia species, as well as intra-species variation.Item Isolation of Anacardic Acid from Natural Cashew Nut Shell Liquid (CNSL) Using Supercritical Carbon Dioxide(American Chemical Society, 2008) Philip, Joseph Y. N.; Da Cruz Francisco, José; Dey, Estera S.; Buchweishaija, Joseph; Mkayula, Lupituko L.; Ye, LeiSolvent extracted cashew nut shell liquid (CNSL), conventionally known as natural CNSL, is a mixture of several alkenyl phenols. One of these alkenyl phenols is anacardic acid, which is present at the highest concentration. In view of anticipated industrial applications of anacardic acid, the objective of this work was to isolate anacardic acid from natural CNSL by supercritical carbon dioxide (scCO2). In this study, the solubility data for natural CNSL in scCO2 under a range of operating conditions of pressure (100, 200, and 300 bar), temperature (40 and 50 °C), and CO2 flow rate (5, 10, and 15 g min−1) were established. The best scCO2 working conditions were found to be 50 °C and 300 bar at a flow rate of 5 g min−1 CO2. Using 3 g of sample (CNSL/solid adsorbent = 1/2) under these scCO2 conditions, it was possible to quantitatively isolate high purity anacardic acid from crude natural CNSL (82% of total anacardic acid) within 150 min. The anacardic acid isolated by scCO2 was analyzed by different spectroscopic techniques (UV−vis, FT-IR, and 1H NMR) and HPLC analysis, indicating that the anacardic acid isolated by scCO2 has better quality than that obtained through a conventional method involving several chemical conversion steps.Item Isolation of Anacardic Acid from Natural Cashew Nut Shell Liquid (CNSL) Using Supercritical Carbon Dioxide(ACS, 2008) Philip, Joseph Y. N.; Da Cruz Francisco, José; Dey, Estera S.; Buchweishaija, Joseph; Mkayula, Lupituko L.; Ye, LeiSolvent extracted cashew nut shell liquid (CNSL), conventionally known as natural CNSL, is a mixture of several alkenyl phenols. One of these alkenyl phenols is anacardic acid, which is present at the highest concentration. In view of anticipated industrial applications of anacardic acid, the objective of this work was to isolate anacardic acid from natural CNSL by supercritical carbon dioxide (scCO2). In this study, the solubility data for natural CNSL in scCO2 under a range of operating conditions of pressure (100, 200, and 300 bar), temperature (40 and 50 °C), and CO2 flow rate (5, 10, and 15 g min−1) were established. The best scCO2 working conditions were found to be 50 °C and 300 bar at a flow rate of 5 g min−1 CO2. Using 3 g of sample (CNSL/solid adsorbent = 1/2) under these scCO2 conditions, it was possible to quantitatively isolate high purity anacardic acid from crude natural CNSL (82% of total anacardic acid) within 150 min. The anacardic acid isolated by scCO2 was analyzed by different spectroscopic techniques (UV−vis, FT-IR, and 1H NMR) and HPLC analysis, indicating that the anacardic acid isolated by scCO2 has better quality than that obtained through a conventional method involving several chemical conversion steps.Item Mechanistic Studies of Carbon Steel Corrosion Inhibition by Cashew Nut Shell Liquid(2002) Philip, Joseph Y. N.; Buchweishaija, Joseph; Mkayula, Lupituko L.The inhibition mechanism of the Cashew Nut Shell Liquid (CNSL) on SAE 1008 carbon steel corrosion in CO 2 saturated 3% NaCl solutions has been studied by weight loss, UV/VIS and electrochemical techniques. The phenoxide, R-Ar-O-ions from the CNSL inhibitor were found to be responsible for the reduction of the corrosion rate of the carbon steel. Also, it was observed that the surface charge of the carbon steel electrodes was positive with respect to the solutions containing CNSL inhibitor. It is likely that the electrostatic attraction between the mechanism of the CNSL inhibitor adsorption involved the positively charged metal surface and the phenoxide ions via their negative ends.Item Mechanistic Studies of Carbon Steel Corrosion Inhibition by Cashew Nut Shell Liquid(2002) Philip, Joseph Y. N.; Buchweishaija, Joseph; Mkayula, Lupituko L.The inhibition mechanism of the Cashew Nut Shell Liquid (CNSL) on SAE 1008 carbon steel corrosion in CO2 saturated 3% NaCl solutions has been studied by weight loss, UV/VIS and electrochemical techniques. The phenoxide, R-Ar-O- ions from the CNSL inhibitor were found to be responsible for the reduction of the corrosion rate of the carbon steel. Also, it was observed that the surface charge of the carbon steel electrodes was positive with respect to the solutions containing CNSL inhibitor. It is likely that the mechanism of the CNSL inhibitor adsorption involved the electrostatic attraction between the positively charged metal surface and the phenoxide ions via their negative ends.Item Natural Products as a Source of Environmentally Friendly Corrosion Inhibitors: The Case of Gum Exudate from Acacia seyal var. seyal(2008) Buchweishaija, Joseph; Mhinzi, G. S.The inhibitive effect of the gum exudate from Acacia seyal var. seyal on the corrosion of mild steel in drinking water was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results obtained show that gum exudates could serve as effective inhibitors for the corrosion of steel in drinking water network. The percentage inhibition increases with increasing the concentration of the gum at 30 oC. The percentage inhibitor efficiency above 95 % was attained at gum concentration ≥400 ppm. The corrosion rates of steel and inhibition efficiencies of the gum exudates obtained from impedance and polarization measurements were in good agreement. Potentiodynamic polarization studies clearly reveal that the gum behaves predominantly as an anodic inhibitor. The study also shows that the inhibition efficiency was insignificantly affected by the temperature rise of the medium.Item Phytochemicals as Green Corrosion Inhibitors in Various Corrosive Media: A Review(2009) Buchweishaija, JosephThere is an intensive effort underway to develop new plant origin corrosion inhibitors for metal subjected to various environmental conditions. These efforts have been motivated by the desire to replace toxic inhibitors used for mitigation of corrosion of various metals and alloys in aqueous solutions. Plants represent a class of interesting source of compounds currently being explored for use in metal corrosion protection in most systems, as possible replacement of toxic synthetic inhibitors. In this review article, research results on the use of eco-friendly phytochemicals as corrosion inhibitors have been summarized. A general introduction to the topic of corrosion mitigation by inhibitors is presented followed by extensive literature survey on the use of natural inhibitors for corrosion control of metals and alloys in different corrosive media.Item Plants as a Source of Green Corrosion Inhibitors: The Case of Gum Exudates from Acacia Species (A. Drepanolobium and A. Senegal)(2009) Buchweishaija, JosephThe inhibitive performance of gum exudates from Acacia drepanolobium and Acacia senegal from Tanzania, towards the corrosion of mild steel in fresh water has been investigated. The experimental methods include potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies. The results indicate that gum exudates (Acacia drepanolobium and Acacia senegal) exhibit good inhibition characteristics to corrosion on mild steel under fresh water medium and the inhibition efficiency of up to 90.7% and 99.7% respectively was attained at 30 oC. Furthermore, the studies have shown that the inhibition performance remained above 90% on both Acacia exudates independent of the raise in temperature. Polarization measurements revealed that the investigated inhibitors are mixed type for mild steel corrosion in fresh water with significant reduction of anodic current densities (this sentence is not clear). The results obtained in this work show that these gum exudates of Acacia senegal and Acacia drepanolobium can serve as effective green inhibitors for the corrosion of mild steel in fresh water systems.Item Port Electrochim(2008) Buchweishaija, Joseph; Mhinzi, G. S.Item Preparation of Molecularly Imprinted Polymers Using Anacardic Acid Monomers Derived from Cashew Nut Shell Liquid(ACS, 2007) Philip, Joseph Y. N.; Buchweishaija, Joseph; Mkayula, Lupituko L.; Ye, LeiThe objective of this work was to use monomers from cashew (Anacardium occidentale L.) nut shells to develop molecularly imprinted polymers. Cashew nut shell liquid (CNSL) is a cheap and renewable agro byproduct consisting of versatile monomers. Solvent-extracted CNSL contains over 80% anacardic acid (AnAc) with more than 90% degree of unsaturation in its C15 side chain. From AnAc monomer, anacardanyl acrylate (AnAcr) and anacardanyl methacrylate (AnMcr) monomers were synthesized and their chemical structures were characterized by Fourier transform IR and NMR. Different imprinted bulk polymers based on AnAc, AnAcr, and AnMcr functional monomers have been prepared. In the present study, each functional monomer was separately copolymerized in toluene with ethylene glycol dimethacrylate and divinylbenzene as cross-linkers, using racemic propranolol as a model template. While the AnAc based polymer revealed a meager rebinding ability, the imprinted polymers made from AnAcr and AnMcr displayed highly specific propranolol binding. At a polymer concentration of 2 mg/mL, AnAcr and AnMcr based imprinted polymers were able to bind over 50% of trace propranolol (initial concentration 1.2 nM). Under the same condition propranolol uptake by the two nonimprinted control polymers was less than 20%. Chiral recognition properties of these polymers were further confirmed using tritium-labeled (S)-propranolol as a tracer in displacement experiments, suggesting that the apparent affinity of the imprinted chiral sites for the correct enantiomer is at least 10 times that of the mismatched (R)-propranolol. Moreover, cross reactivity studies of these polymers showed that the (S)-imprinted sites have higher cross-reactivity toward (R,S)-metoprolol than (R)-propranolol and (R)-timolol.Item The Synthesis, Spectroscopy and X-ray Single Crystal Structure of Catena-[(μ-anacardato)-copper(II)bipyridine][Cu2{(μ-O2CC6H3(o-OH)(o-C15H31)}4(NC5H5)2](2013-08) Malik, Azad; O'Brien, Paul; Tuna, Floriana; Pritchard, Robin G.; Buchweishaija, Joseph; Kimambo, Elianaso; Mubofu, Egid B.Hydrogenation of crude anacardic acid gave a transparent crystalline product on recrystallization. When reacted with copper nitrate in the presence of pyridine it produced green crystals of a pyridine adduct of a dimeric copper(ii) anacardate with the copper acetate structure. The X-ray single crystal structures of both anacardic acid and the copper complex were determined. Magnetic studies have confirmed strong antiferromagnetic coupling between copper(ii) centre in the dimer. The exchange coupling constant was determined to be J = -324 cm(-1). The EPR spectra of the polycrystalline product are consistent with spin S = 1. The zero-field splitting parameter and g tensor values are |D| = 0.36 cm(-1), g|| = 2.36 and g⊥ = 2.06.