Inhibition of Corrosion of Mild Steel in Hydrochloric Acid Solution by two Schiff Bases Derived from Benheric and Linoleic Acids

Communication in Physical Sciences 2019, 4(2): 58-66 Author: S. A. Odoemelam, U. I. Ekanem & F. K. Ekuma  The inhibition efficiencies of the two Schiff bases 2[2-diethylamino) ethyl methyl amino)-4- methy1-5-3 (3-methyl sulfanyl propy1 amino) methyldiene cyclohexdien-1-one (DEMS) and [1- (azepan-1-yl)2-2-[4-(2-tert-butyl sulfanyl ethyl piperazin-1-yl] ethanone (ATSP), synthesized from linoleic and benheric acids on the corrosion of mild steel in 1 M HCl solutions were investigated usinggravimetric and potentiodynamic polarization techniques.. The results obtained from both methods indicated that inhibition efficiencies increased with increase in concentration of the Schiff bases and decreased as the temperature increased. Potentiometric polarization data indicated decrease in polarization resistance (and a corresponding decrease in corrosion current) with concentration, which indicated a progressive retardation of corrosion strength with increasing concentration.Displacement potential from the reference blank and equality of extension of cathodic and anodic polarization curves confirmed that DEMS and ATSP are mixed type inhibitor. Mechanism of adsorption of the inhibitors was confirmed to be physiosorptionbased on calculated values of activation energy and the changes in free energy of adsorption. The adsorption of the inhibitors is spontaneous, exothermic and followed the Langmuir adsorption model

Adsorptive studies of the inhibitive properties of ethanolic extracts of Parinari polyandra on Mild steel in acidic media

Communication in Physical Sciences 2019, 4(1): 39-47 Authors: F E Awe, M Abdulwahab & H A Otaru  Corrosion inhibition effectiveness of ethanol extracts of Parinari polyandra for mild steel was investigated using gravimetric and polarization methods. The influence of extract concentrations (0.1g/l to 0.5g/l) and temperatures (303K to 323K) on corrosion and corrosion inhibition were assessed. The results obtained showed that the plant extracts decreased the corrosion rate of mild steel in the acid medium. The corrosion rate decreased with increasing extract concentration for mild steel at 303 K. Inhibition efficiency in all the systems decreased with a rise in temperature, suggesting physical adsorption of the extract constituents on the metal surfaces. Linear polarization studies showed that the plant extract suppressed both the anodic and cathodic half reactions of the corrosion processes, thereby acting as mixed-type inhibitors. Langmuir isotherm was found to be the best isotherm that described the adsorption behaviour of the extract on the surfaces of mild steel at room temperature, whereas the adsorption property at elevated temperature was best described by the Freundlich and Temkin adsorption isotherms. Calculated values of free energy of adsorption, ∆????????????????????, on mild steel in the presence of the inhibitor was found to be within the range expected forphysical adsorption mechanism. Corrosion activation energy (Ea) values for mild steel in the acid solutions increased in the presence of the inhibitor and were found to be less than 80 kJmol-1

Studies on some speciality Cardo Polymers

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Advanced treatment of wastewater effluents by multi-functional carbon nanotube-TiO2 nanotube membranes

Recently, the coupling of TiO2-photocatalysis with a membrane separation process has been perceived as a powerful tool for the recycling of wastewater effluents. While the membrane has the simultaneous task of supporting the photocatalyst as well as acting as a selective barrier for the species to be degraded, the photocatalyst degrades the organic compounds with the added advantage of mitigating membrane fouling. The focus of this thesis is to combine the specific features of TiO2 nanotubes with the unique properties of CNTs to design a multi-functional membrane for the enhanced removal of effluent organic matters (EfOMs) in wastewater effluents. Firstly, the kinetics of photocatalytic degradation of model organic compounds by TiO2 NPs were studied, and the experimental conditions for the enhancement of photocatalytic degradation efficiency were optimised. The photocatalytic reactivity and stability of TiO2 NPs were affected in the presence of natural organic matter (NOM). Secondly, TiO2 nanotube arrays (TNAs) were successfully fabricated via anodic oxidation of Ti substrates and their geometrical characteristics were optimised by controlling the synthesis parameters for enhancement of the photocatalytic removal efficiency of model organic compounds. Finally, multi-functional CNT/TiO2 nanotube membranes were fabricated via chemical vapour deposition (CVD) and anodic growth of TNAs on a porous Ti sheet. The performance of the hybrid CNT/TiO2 nanotube membrane (CNT/TNM) for removal of 4CBA was experimentally evaluated in a continuous filtration system under UV-A irradiation. The surface properties and the performance of the TNM were notably influenced by incorporation of CNTs. The CNT/TNM showed enhanced performance in removal of model compound compared to the TNM, which was attributed to the higher adsorption capacity of well-incorporated CNT/TNM

Advanced treatment of wastewater effluents by multi-functional carbon nanotube-TiO2 nanotube membranes

Recently, the coupling of TiO2-photocatalysis with a membrane separation process has been perceived as a powerful tool for the recycling of wastewater effluents. While the membrane has the simultaneous task of supporting the photocatalyst as well as acting as a selective barrier for the species to be degraded, the photocatalyst degrades the organic compounds with the added advantage of mitigating membrane fouling. The focus of this thesis is to combine the specific features of TiO2 nanotubes with the unique properties of CNTs to design a multi-functional membrane for the enhanced removal of effluent organic matters (EfOMs) in wastewater effluents. Firstly, the kinetics of photocatalytic degradation of model organic compounds by TiO2 NPs were studied, and the experimental conditions for the enhancement of photocatalytic degradation efficiency were optimised. The photocatalytic reactivity and stability of TiO2 NPs were affected in the presence of natural organic matter (NOM). Secondly, TiO2 nanotube arrays (TNAs) were successfully fabricated via anodic oxidation of Ti substrates and their geometrical characteristics were optimised by controlling the synthesis parameters for enhancement of the photocatalytic removal efficiency of model organic compounds. Finally, multi-functional CNT/TiO2 nanotube membranes were fabricated via chemical vapour deposition (CVD) and anodic growth of TNAs on a porous Ti sheet. The performance of the hybrid CNT/TiO2 nanotube membrane (CNT/TNM) for removal of 4CBA was experimentally evaluated in a continuous filtration system under UV-A irradiation. The surface properties and the performance of the TNM were notably influenced by incorporation of CNTs. The CNT/TNM showed enhanced performance in removal of model compound compared to the TNM, which was attributed to the higher adsorption capacity of well-incorporated CNT/TNM

Development of electroactive polymers for application in anti-corrosion formulations.

Corrosion is a major environmental and economic problem with many modern manmade structures heavily relying on the utilisation of metals and alloys due to their extraordinary strength, mechanical and physical properties. Applications such as those seen in the construction industry, aerospace and marine industries, all of which need a constant protection and barriers against the harsh environmental conditions. Current methods of protection employ the use of chromates in paint formulations for the active anti-corrosive paints or the uses of non-active polymeric paints acting solely as a physical barrier preventing the diffusion of ions through to the metal surface. However ideas have recently come forward regarding the use of conductive and electro-active polymers. Theorised to not only prevent the diffusions of ions on a physical level but to also act as an electrochemical barrier by passivating the surface of the metal so that it can protect itself from further degradation caused by corrosive agents, one such polymer that has been put forward is Polyaniline (PANI). Through the process of doping, PANI can be made to conduct an electrical current through the formation of charge carriers by oxidising the PANI with a protonic acid which can be functionalised. Further investigation has found that the functionalisation of these acids can dramatically change the once insoluble material in common solvents soluble, increasing the processability and possible increase the applications of this materials. This thesis reports the synthetic routes used to obtain functionalised Sulphonic acids based on the precursor 5-Sulphoisophthalic acid by acid catalysed esterification’s are described. With the synthesis phosphoric acid diester carried out by several named reported methods and both series were progressed forward to dope PANI (polyaniline). The optical properties were analysed for all doped PANI in DCM showing that branched side chains produced the highest optical absorption at around 944 nm and some as thin films (21) and (25), showing optical band gaps of 1.21 eV. This thesis also reports the anti-corrosions properties for the doped PANI systems. Films were cast coating mild carbon steel and copper plates, along with a range of acrylic resin/doped PANI composite films, PVC/doped PANI composite films and a set of films for an epoxide resin/doped PANI (17) composite. Samples were subjected to accelerated corrosion tests and showed that the application of PANI to the metal surfaces was beneficial and displayed efficacious anti-corrosion properties, not only in the doped state (emeraldine salt) but also in its native undoped state (emeraldine base) where the polymer undergoes redox reactions at the metal interface passivating the surface and creating an electrochemical barrier system which the polymer itself is a component however corrosion inhibition is only truly effective when a physical barrier is used in combination. The results of the dopant synthesis, doped PANI systems and their composites in resins and the data from NMR spectroscopy, IR, elemental analysis, LC-Mass spectroscopy, mass spectroscopy, UV-Vis spectroscopy are presented in this thesis. The accelerated corrosion tests and the data from scanning electron microscopy (SEM) are also presented within this thesis

Studies on Novel Polyester Polyols and Their Biocomposite

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Study of titanium, tantalum and chromium catalysts for use in industrial transformations

PART A The syntheses, spectroscopic and electrochemical characterisation of a series of titanium and tantalum phthalocyanine complexes are reported. The complexes are unsubstituted and substituted at either the peripheral or non-peripheral positions with sulphonates, aryloxy, arylthio or amino groups. The complexes mostly exhibit Qbands in the near-infrared region as well as interesting properties in different solvents. The interaction of differently sulphonated titanium and tantalum phthalocyanine complexes with methyl viologen (MV[superscript 2+]), and hence the stoichiometry and association constants are evaluated. Detailed photophysicochemical properties of the complexes were investigated and are for the first time presented with fluorescence lifetimes easily obtained from fluorescence quenching studies. The transformation of 1-hexene photocatalysed by aryloxy- and arylthio-appended complexes is also presented for the first time. The electrochemical properties of the complexes are unknown and are thus presented. Cyclic (CV) and square wave (SWV) voltammetries, chronocoulometry and spectroelectrochemistry are employed in the study of the complexes. Two oneelectron reductions and a simultaneous 4-electron reduction are observed for the unsubstituted Cl[subscript 3]TaPc. Reduction occurs first at the metal followed by ring-based processes. The tetra- and octa-substituted derivatives however exhibit peculiar electrochemical behaviour where a multi-electron transfer process occurs for complexes bearing certain substituents. For all complexes, the first two reductions are metal-based followed by ring-based processes. A comparative study of the electrocatalytic activities of the complexes towards the oxidation of nitrite is also investigated. The complexes are immobilised onto a glassy carbon electrode either by drop-dry or electropolymerisation methods. All the modified electrodes exhibit improved electrocatalytic oxidation of nitrite than the unmodified electrodes by a twoelectron mechanism producing nitrate ions. Catalytic currents are enhanced and nitrite overpotential reduced to ~ 0.60 V. Kinetic parameters are determined for all complexes and a mechanism is proposed. PART B: The syntheses and electrochemical characterisation of chromium and titanium complexes for the selective trimerisation of ethylene to 1-hexene are presented. The synthesis of the chromium complex requires simple steps while tedious steps are used for the air-sensitive titanium complex. The spectroscopic interaction of the chromium complex with the co-catalyst methylaluminoxane is investigated. The complexes are characterised by electrochemical methods such as cyclic voltammetry and spectroelectrochemistry

Graphene-Polymer Composites II

Graphene-polymer nanocomposites continue to gain interest in diverse scientific and technological fields. Graphene-based nanomaterials present the advantages of other carbon nanofillers, like electrical and thermal conductivity, while having significantly lower production costs when compared to materials such as carbon nanotubes, for instance. In addition, in the oxidized forms of graphene, the large specific area combined with a large quantity of functionalizable chemical groups available for physical or chemical interaction with polymers, allow for good dispersion and tunable binding with the surrounding matrix. Other features are noteworthy in graphene-based nanomaterials, like their generally good biocompatibility and the ability to absorb near-infrared radiation, allowing for the use in biomedical applications, such as drug delivery and photothermal therapy.This Special Issue provides an encompassing view on the state of the art of graphene-polymer composites, showing how current research is dealing with new and exciting challenges. The published papers cover topics ranging from novel production methods and insights on mechanisms of mechanical reinforcement of composites, to applications as diverse as automotive and aeronautics, cancer treatment, anticorrosive coatings, thermally conductive fabrics and foams, and oil-adsorbent aerogels