The in hibitory efficiencies of methanolic leaf extract of Irvingia gabonensis and the role of a halide ion as an enhancement on the inhibition of aluminium corrosion in HCl medium were studied at varying acid concentrations of 0.01M , 0.05M, 0.1M und er the influence of 3% NaCl. Result of the studies carried out by weight loss techni que showed that I. gabonensis is highly an efficient inhibitor for the corrosion of al umimium in HCl acid environment and its inhibitory efficiencies increases with respect to the time of exposure.. It was observed from the study that in the absence o f the plant extracts, the weight loss increases rapidly indicating an increase in corrosi on rate from 0.003g to 0.026g as acid concentration was increased from 0.01M to 0.1M . Conversely, when the plant extract was introduced, there were remarkable decrease in weight loss from 0.001g at 0.01M of HCl to 0.021g at 0.1M , showing a decrea se in corrosion of the metal. Experimental data proved that the highest corrosion rates w ere observed at the highest acid strength pointing that at a concentration of 0.1M H Cl, 19% efficiency was attained and a maximum efficiency of 67% was obtained at 0.01MHCl showing a correlation between concentration and inhibition of metal. It was also revealed that the inhibitory efficiency of I. gabonensis in HCl medium was magnif icently increased when a salt of halide ion was introduced showing a weight loss of 0.01g through 0.003g as acid strength increased from 0.01M to 0.1M. This could be attributed to that the fact that halide ion facilitates the adsorption of organic cat ions during metal corrosion by forming intermediate bridges between the metal surface and the positive end of the organic inhibitor and this forms a protective hydrophi lic film on the metal surface which provided a barrier to the dissolution of the metal into the acid medium.

The challenge of heavy metal contaminations have been remediated to a certain level by the application of several methods of their extractions from aqueous media. Solvent extraction of zinc (II) ions from buffered aqueous solutions into acetylacetone solution of sulphamethoxazole as a function of pH and concentration of anionic substances and certain mineral acids were investigated in this work. The aqueous medium was prepared by dissolving 1.0995g of ZnSO4.7H2O in 250 ml volumetric flask to form 1000mg/L solution. 50mg/L working concentration was prepared from the 1000mg/L by dilution method. The organic phase is 0.5 M Sulfamethoxazole solution prepared by dissolving 12.664g of the salt in 100 ml acetylacetone. 2 ml each of aqueous and organic phases were taken with micro pipette and transferred into a set of 20 ml extraction bottle and the mixture was agitated mechanically for about 30 minutes. The mixture was allowed to settle and separate into two layers. 1 ml of the aqueous phase was taken, diluted and analysed for Zn (II) ions using atomic absorption spectrophotometer at a wavelength of 213.9. The results obtained on studying the effect of pH showed that Zn (II) ion was quantitatively extracted between pH of 7.0 to pH 8.0. The highest percentage extraction 85.37% was observed at pH 8.0 in acetylacetone solution of sulphamethoxazole. Increase in pH above 8.0 resulted in a steady decrease in the extraction of Zn (II). Studies on the effect of anions showed significant extractions which changes as the anions concentrations increased. All studies on mineral acids also showed significant extractions and increase in the concentrations of the acids affected the percentage extraction. Generally Zinc (II) ions can be extracted quantitatively in mild acids and anions concentrations when buffered from slightly acidic pH ranges of 6.0 to slightly alkaline pH values of 8.5.

The methanolic leaf extracts of Chromoleana odorata and Hevea brasiliensis were tested for corrosion inhibitory effects towards aluminum by varying the concentration of hydrochloric acid as 0.01M, 0.05M and 0.1M HCl. The anti corrosion efficiency of the plant extract was studied by means of weight loss method. It was observed from the experiment, that in the absence of the plant extracts, the weight loss increases indicating an increase in corrosion. Conversely when the plant extracts were introduced, there were remarkable decrease in weight loss leading to reduction in corrosion and an increase in inhibitory efficiency. Upon comparative analysis on the inhibitory efficiency of the two extracts, it was discovered that Chromoleana odorata gave the higher inhibition efficiency of 62% than the Hevea brasiliensis which gave 57% inhibition efficiency. This study shows that Chromoleana odorata gave better inhibition against corrosion to aluminium than Hevea brasiliensis. FT-IR spectra of the plant extracts were also examined to elucidate the possible functional groups that may be responsible for the anti-corrosion activity of these biodegradable extracts in methanolic solution.