Inhibitive and adsorption properties of ethanol extract of Lasianthera africana for inhibition of corrosion of mild steel in H 2 SO 4 were studied using gravimetric, thermometric, gasometric, and infrared (IR) methods. The extract was found to be a good inhibitor of corrosion of mild steel in H 2 SO 4 . Inhibitive properties of the extract were attributed to enhancement in adsorption of the inhibitor on mild-steel surface by saponin, alkaloid, tannin, flavanoid, cardiac glycoside, and anthraquinone (present in the extract). Also, adsorption of the inhibitor was found to be exothermic, spontaneous, and consistent with assumptions of Langmuir and Temkin adsorption isotherms. Synergistic study revealed that, of the investigated halides, only KCl may enhance adsorption of the inhibitor, whereas KBr and KI antagonized its adsorption. Based on the decrease in efficiency of the inhibitor with temperature, with values of activation energy and free energy of adsorption below the threshold values of -40 and 80 kJ mol -1 , respectively, a physical adsorption mechanism has been proposed for adsorption of ethanol extract of Lasianthera africana on the surface of mild steel.
Inhibitive and adsorption properties of ethanol extract of vernonia amygdalina for the corrosion of mild steel were studied using weight loss, thermometric, gasometric and IR methods of monitoring corrosion. The results revealed that ethanol extract of Vernonia amygdalina inhibited the corrosion of mild steel. The inhibition efficiency of the extract increased as the concentration of the extract increases. The inhibitor was found to function by being adsorbed on the surface of mild steel. The adsorption of the inhibitor followed the Langmuir adsorption isotherm. IR spectra of the corrosion product (without inhibitor), the extract and the corrosion product (with the inhibitor) confirmed that ethanol extract of vernonia amygdalina is an adsorption inhibitor. Phytochemical studies also revealed that ethanol vernonia amygdalina contains tannin, saponnins, flavanoid and anthraquinone, all of them contributing to the corrosion inhibition. Physical adsorption mechanism has been proposed from the values of some of the thermodynamic parameters obtained.
PurposeThe purpose of this paper is to study the effect of concentration of H2SO4 on the corrosion of mild steel and to investigate the inhibitive properties of Aloe vera for mild steel corrosion. The study also seeks to investigate the possibility of using Aloe vera as a green corrosion inhibitor for mild steel.Design/methodology/approachGasometric (Hydrogen evolution) and thermometric methods of corrosion monitoring have been adopted for the study. The study was conducted at 303 and 333 K and the concentrations of inhibitor used were 0.1, 0.2, 0.3 and 0.4 g/L. The inhibitor was prepared by using alcohol extract of moisture free samples of Aloe vera. The functional groups present in the extract have been determined using infra red spectrophotometer. Thermodynamic and adsorption theories have been used to interpret the data.FindingsEthanol extract of Aloe vera is a good inhibitor for mild steel corrosion at 303 and 333 K. The inhibitor acts by chemical adsorption isotherm. Functional groups identified in the extract are found to played dominant role in the adsorptive and inhibitive potentials of this extract. Values of inhibition efficiency obtained from gasometric and thermometric analysis were comparable.Research limitations/implicationsFurther study on synergism with the view of enhancing the inhibition efficiency of Aloe vera extract and the used of other analytical methods may reveals a wealth of information on the possibilities of transforming this research for field application.Originality/valueThe paper provides information on the use of Aloe vera as a green corrosion inhibitor. It has not been published elsewhere.
This paper presents an assessment of the aflatoxin B1contamination of some food grains (wheat, millet, Guinea corn, breadfruit and groundnut) from major markets in the Niger Delta region of Nigeria. The concentrations of aflatoxin B1obtained in the ranges from 17.01-20.53 µg kg–1for wheat, 34.00– 40.30 µg kg–1for millet, 27.22-36.13 µg kg–1for guinea corn, 40.06-48.59 µg kg–1for breadfruit and 74.03-82.12 µg kg–1for groundnut. Aflatoxin B1was detected in all the samples. There were significant differences (p<0.01) in the levels of aflatoxin B1determined in all the samples and the toxin contamination was not restricted to any particular section of the region. The presence of aflatoxins in grains constitutes a serious health hazard to both human beings and animals because of their toxic and carcinogenic property.
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