Search

The Total Petroleum Hydrocarbon (TPH) is the total of different types of hydrocarbons in the crude oil mixture. It includes volatile petroleum hydrocarbons and extractable petroleum hydrocarbons. The TPH determination techniques are primarily grouped into spectroscopic (ultraviolet spectroscopy, raman spectroscopy, fluorescence spectroscopy, infrared spectroscopy) and non- spectroscopic (gravimetric, immunoassay, gas chromatography with mass spectrometric detection (GC/MSD), gas chromatography with flame ionization detection (GC-FID)) techniques. Solvent and the sample characteristics determine the efficiency of the techniques. This paper compares spectroscopic (fourier transform infrared spectroscopy and ultraviolet spectroscopy) and non-spectroscopic (gravimetric and gas chromatography) methods in the determination of TPH in soil. Spectroscopic and non-spectroscopic techniques are efficient, but the paper recommends spectroscopic techniques because the techniques are efficient with small operational time, and are safer in occupational health and safety issues. In addition their results are accurate and reliable.

Cetyltrimethylammonium bromide (CTAB) – modified and unmodified sodium bentonite were both used for the competitive adsorption of m-xylene and toluene from their aqueous solution. Infrared spectroscopy (IR) and expansion tests (adsorption capacity and Foster swelling) measurement were performed in order to evaluate the performance of the adsorbents. The FT-IR results indicated that the quaternary ammonium salts (CTAB) were intercalated between the layers of the sodium bentonite clay. The Foster swelling test results indicated that the affinity of CTAB was more in the treated clay for all other organic compounds tested. The result showed that modified sodium bentonite swelled more than the unmodified and the order of the swelling factor is; m- xylene > toluene > gasoline > diesel > kerosene > water. However, when the assay was performed under agitation, it yielded higher swelling capacity. The modified clay exhibited very high capacity of adsorption compare to unmodified samples. The m-xylene and toluene uptake follows a pseudo second order kinetics mechanism, suggesting that the rate determining step of adsorption involves the two adsorbates competitively adsorbed on the adsorbent sites. Therefore this organo-modified bentonite can be used for the removal of organics from polluted aqueous effluents.

The study focused on the investigation of the effectiveness of the pericarp of monkey kola (Cola lepidota) biomass (CLPB) in the removal of toluene from aqueous system. X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM) and phytochemical screening methods were used for characterizing the biosorbent. The effects of contact time, pH, and concentration on biosorption process were studied. The phytochemical screening showed the presence of alkaloids, flavonoids, tannins, carbohydrate, saponins and steroids. Carboxylic, alkene and alcohol groups were found to be the principal functional groups. The highest percentage removal was 99.63% at toluene initial concentration of 40 mg/L and 98.30% at pH 8. The contact time 30 minutes gave better removal efficiency of 99.89%. Among the biosorption isotherm models tested (Langmuir, Freundlich, Dubinin Radushkevich and Temkin, respectively), the Langmuir model equation gave a better fit of the equilibrium data with a correlation coefficient (R2) of 0.99. The equilibrium data was tested with pseudo-first order and pseudo-second order models and pseudo-second order model (R² = 0.99) fitted more than the pseudo-first order model (R² = 0.85). This study has revealed that Cola lepidota is a potential biosorbent for the removal of toluene from aqueous medium under the operating conditions of contact time of 30 minutes, pH of 8 and initial concentration of 40 mg/g.

The corrosion inhibition characteristics of Chrysophyllum cainto cotyledon aqueous extract was studied for the corrosion of pipeline steel in 0.5 M HCl using gravimetric technique. The corrosion surface morphology and corrosion surface film were studied using Scanning electron microscope and Fourier transform infrared spectroscopy respectively. The results obtained showed Chrysophyllum cainto aqueous extract as a good corrosion inhibitors of pipeline steel corrosion in acidic environment, recording an average corrosion inhibition efficiency above 90% at 303 K. The Scanning electron micrograph showed a smoother corrosion surface morphology in the presence of the extract while the Fourier transform infrared spectroscopic data showed the corrosion inhibition mechanism to be through adsorption.

The capacity of aqueous Tetracarpidium conophorum Shell (TCE) Extract to inhibit pipeline steel corrosion in 0.25 M H2SO4 acid was investigated using weight loss and Uv-visible spectroscopy techniques. The phytochemical components of Tetracarpidium conophorum were identified using GC-MS analysis. The results obtained shows that aqueous Tetracarpidium conophorum shell extract decreased the corrosion rate, while the corrosion inhibition efficiency increased with increase in exatract concentration. The Uv-visible spectra indicated a chemical interaction between the TCE molecules and atoms of Iron on the pipeline steel surface, while GC-MS analysis showed the presence of organic compounds with hetero-atoms for adsorption on the steel surface.

The corrosion inhibition characteristics of Sulfadoxine plus Pyrimethamine (S&P) was evaluated and compared with the inhibition performance of an industrial corrosion inhibitor (S-Ind) under anaerobic condition. Modified gravimetric and electrochemical techniques were used. The corrosion inhibition efficiencies of both S&P and S-Ind were comparable for all the techniques applied. S&P gave slightly higher inhibition efficiency, while S-Ind gave a more steady corrosion protection. The corrosion inhibition efficiencies increased with increased concentration of both substances. The polarization curves showed mixed inhibition behavior for both S&P and S-Ind. A mechanism of chemisorption was proposed for the adsorption of S&P and S-Ind on pipeline steel surface, while the negative Gibbs free energy of adsorption values indicates a spontaneous adsorption process. The adsorption characteristics of the inhibitors were fitted into Langmuir adsorption isotherm. Keywords: Adsorption, Anaerobic, Corrosion, Inhibitor, Modified gravimetric, Pipeline steel

The corrosion inhibition characteristics of Vernonia Amygdalina stem extracts was carried out using gravimetric technique on mild steel in 1.0 M HCl acid solution at temperature ranges of 303 to 333 K. While the mechanism of corrosion inhibition through suspected adsorption was determined by fitting the corrosion inhibition data into the Langmuir and Temkins isotherms. The thermodynamic parameters were also mathematically determined. The results obtained exhibited good corrosion inhibition properties. The weight loss and corrosion rate of mild steel in the presence of the extract inhibitor decreased with increased extract concentration. Temperature increase, increased weight loss and consequent corrosion rate. Comparatively, the extract directly improved corrosion inhibition efficiency with extract concentration and time. The recorded low corrosion inhibition efficiency values of 52.55 percent of 5.0 g/L extract at 303 K was attributed to short measurement time interval. The isotherms data attributed the corrosion inhibition mechanism to adsorption. Furthermore, the Langmuir isotherm reveals that the surface of the mild steel was not uniform, whereas the Temkins isotherm reveals that repulsion on the adsorbent surface. Thermodynamically, the negative ∆Gads signifies that the Vernonia amygdalina stem extract adsorption on mild steel was a spontaneous process while lower negative ∆Gads values indicates physiosorptive process. Interestingly, the Vernonia amygdalina stem extract increased the activation energy Ea confirming its ability slow down corrosion.

The electrochemical corrosion behaviour of pipeline steel in a sulphuric acid environment, in the absence and presence of commercial Rutin (CR), was studied using electrochemical techniques. The polarization and impedance curves showed an excellent corrosion inhibition characteristic of Rutin, which was more cathodically controlled. Temperature increase slightly improved CR corrosion inhibition capacity. CR was able to increase the charge transfer resistance up to four days, and showed a smoother corrosion surface morphology in the study environment. Analysis of the corrosion surface film showed that Rutin was chemically adsorbed onto the pipeline steel surface.

The inhibitive action of Piper guineense (uziza leaf) extract on the corrosion of mild steel in a 2 M H2SO4 medium has been studied using weight loss method. The collected leaf samples were rigorously grounded and squeezed, with the resultant gel extract used for the weight loss determination at 1.0%, 2.0%, 3.0%, 4.0% and 5.0% v/v concentrations, respectively. Therefore, rectangular mild steel coupons in a 2 M H2SO4 solution were also employed to determine the amount of weight loss in the absence and presence of Piper guineense extract at temperatures of 303 K, 313 K and 323 K. The results show that mild steel corrosion inhibition increases with increasing concentrations of Piper guineense extract, showing greater efficiency at higher temperatures of 313 K and 323 K. Moreover, Piper guineense extract can effectively perform as a green and non-toxic inhibitor for mild steel corrosion in acidic environments.

The inhibition capacity ofBrassica oleracea(BO) extract on the corrosion of pipeline steel in 0.5 M H2SO4was evaluated using electrochemical techniques. The results showed an excellent inhibition efficiency which increased with initial increase in extract concentration and temperature to a point and decreased with further increase in BO extract concentration and temperature. Mixed inhibition behaviour was proposed for the action of BO. The unique behaviour of BO was attributed to the organic entities present in the extract.

The corrosion inhibition characteristics of two medicinal molecules phenylalanine and rutin on mild steel in 1.0M Hydrochloric acid were evaluated using gravimetric method. Corrosion inhibition efficiency of 83.78 and 90.40 % was obtained respectively after seven days. However, phenylalanine showed weak accumulative higher corrosion inhibition efficiency. The presence of both molecules in the corrosive environment reduced the corrosion rate constant and increased the material half-life. Thermodynamic data calculated suggests a spontaneous adsorption of the molecules on the mild steel’s surface.

Cetyltrimethylammonium bromide (CTAB) – modified and unmodified magnesium exchanged bentonite were used for the competitive adsorption of m-xylene and toluene from their aqueous solution. Infrared spectroscopy (IR, adsorption capacity and Foster swelling measurements were performed using Fourier Transform Infrared Spectrophotometer to evaluate the performance of the adsorbents. The FT-IR results indicated that the quaternary ammonium salts (Cetyltrimethylammonium bromide) were intercalated between the layers of the bentonite clay. The Foster swelling test results indicated that the affinity of CTAB occurred in the treated clay as tested in all organic solvents (diesel, kerosene, gasoline, toluene and m-xylene), with and without agitation. The result showed that modified magnesium bentonite swelled more than the unmodified and the order of the swelling factor is; m- xylene > toluene > gasoline > diesel > DPK > water. However, when the assay was performed under agitation, it yielded higher swelling capacity and all the organic solvents used in this investigation showed good compatibility after organophilization. The modified clay exhibited very high capacity of adsorption compared to unmodified samples. The m-xylene and toluene uptake follows a pseudo second order kinetics mechanism, suggesting that the rate determining step of adsorption involves the two adsorbates competitively adsorbed on the adsorbent sites. Modified magnesium bentonite has a higher percentage removal and higher adsorption capacity than raw or unmodified magnesium bentonite. These adsorbents (modified magnesium bentonite) are therefore recommended for use by water treatment and petrochemical industries for removal of hydrocarbons (m- xylene and toluene) from their waste water and effluents.