Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium

In terms of environmental impacts and cost considerations, the use of green additives particularly from plant origin have been found as a viable alternative approach to synthetic organic inhibitors in combatting the menace of corrosion. However, owing to the composition matrix complexity of plant ex...

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Main Author:	Ajeigbe, Sunday Osinkolu
Format:	Thesis
Language:	English
Published:	2017
Subjects:	QD Chemistry
Online Access:	http://eprints.utm.my/id/eprint/79539/1/SundayOsinkoluAjeigbePFS2017.pdf
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spelling	my-utm-ep.795392018-10-31T12:58:10Z Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium 2017 Ajeigbe, Sunday Osinkolu QD Chemistry In terms of environmental impacts and cost considerations, the use of green additives particularly from plant origin have been found as a viable alternative approach to synthetic organic inhibitors in combatting the menace of corrosion. However, owing to the composition matrix complexity of plant extracts, efforts are seldom made to engage their isolated constituents for corrosion inhibition; hence their optimal utilization is hindered. In this research, corrosion inhibition properties of the rhizomes of Alpinia galanga and its constituents were investigated experimentally and theoretically on mild steel in hydrochloric acid solution using weight loss and electrochemical methods, and surface characterization techniques namely attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). Explorations using response surface methodology (RSM) as the optimization tool and quantitative structure-activity relationship (QSAR) modelling of the plant’s major phenylpropanoids were carried out. At room temperature, efficiencies were highest at the uppermost concentrations of all the inhibitors in the following order: hexane extract (90.2%), essential oils (87.9%), and methanol extract (74.2%) while for the phenylpropanoid constituents; 1'-acetoxychavicol acetate (84.6%), methyl eugenol (83.6%), eugenol acetate (82.1%), eugenol (76.3%) and p-hydroxycinnamic acid (30.4%). Optimal efficiencies of 90.3% and 91.17% were attained for hexane extract and essential oil components, respectively, at optimized concentration, temperature, and time. Investigations revealed that mixed mode interactions for all the inhibitors and their effectiveness were supported by the surface characterization techniques. Inhibition efficiencies decreased with increasing temperature for all inhibitors except for the essential oil fraction which increased steadily. The Langmuir isotherm model showed the best fit, giving negative values of adsorption energies with thermodynamics and kinetics parameters supporting the principles of electrostatic interaction. The structural requirements of the phenylpropanoids for effective inhibition were clarified while electrostatic interaction-related descriptors were selected by penalization methods in the constructed QSAR models. 2017 Thesis http://eprints.utm.my/id/eprint/79539/ http://eprints.utm.my/id/eprint/79539/1/SundayOsinkoluAjeigbePFS2017.pdf application/pdf en public phd doctoral Universiti Teknologi Malaysia, Faculty of Science Faculty of Science
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	QD Chemistry
spellingShingle	QD Chemistry Ajeigbe, Sunday Osinkolu Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium
description	In terms of environmental impacts and cost considerations, the use of green additives particularly from plant origin have been found as a viable alternative approach to synthetic organic inhibitors in combatting the menace of corrosion. However, owing to the composition matrix complexity of plant extracts, efforts are seldom made to engage their isolated constituents for corrosion inhibition; hence their optimal utilization is hindered. In this research, corrosion inhibition properties of the rhizomes of Alpinia galanga and its constituents were investigated experimentally and theoretically on mild steel in hydrochloric acid solution using weight loss and electrochemical methods, and surface characterization techniques namely attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). Explorations using response surface methodology (RSM) as the optimization tool and quantitative structure-activity relationship (QSAR) modelling of the plant’s major phenylpropanoids were carried out. At room temperature, efficiencies were highest at the uppermost concentrations of all the inhibitors in the following order: hexane extract (90.2%), essential oils (87.9%), and methanol extract (74.2%) while for the phenylpropanoid constituents; 1'-acetoxychavicol acetate (84.6%), methyl eugenol (83.6%), eugenol acetate (82.1%), eugenol (76.3%) and p-hydroxycinnamic acid (30.4%). Optimal efficiencies of 90.3% and 91.17% were attained for hexane extract and essential oil components, respectively, at optimized concentration, temperature, and time. Investigations revealed that mixed mode interactions for all the inhibitors and their effectiveness were supported by the surface characterization techniques. Inhibition efficiencies decreased with increasing temperature for all inhibitors except for the essential oil fraction which increased steadily. The Langmuir isotherm model showed the best fit, giving negative values of adsorption energies with thermodynamics and kinetics parameters supporting the principles of electrostatic interaction. The structural requirements of the phenylpropanoids for effective inhibition were clarified while electrostatic interaction-related descriptors were selected by penalization methods in the constructed QSAR models.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Ajeigbe, Sunday Osinkolu
author_facet	Ajeigbe, Sunday Osinkolu
author_sort	Ajeigbe, Sunday Osinkolu
title	Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium
title_short	Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium
title_full	Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium
title_fullStr	Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium
title_full_unstemmed	Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium
title_sort	optimization of extracts and constituents from alpinia galanga as corrosion inhibitor for mild steel in acidic medium
granting_institution	Universiti Teknologi Malaysia, Faculty of Science
granting_department	Faculty of Science
publishDate	2017
url	http://eprints.utm.my/id/eprint/79539/1/SundayOsinkoluAjeigbePFS2017.pdf
_version_	1747818251018043392

Optimization of extracts and constituents from Alpinia galanga as corrosion inhibitor for mild steel in acidic medium

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