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Browsing Research Articles by Subject "Adsorption mechanism"

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    Thermodynamic and adsorption evaluation of codiaeum variegatum brilliantissima - Zanzibar as inhibitor of mild steel corrosion in 1 M HCl
    (Rivers State University, 2020-12) Izionworu, Vincent Onuegbu; Oguzie, Emmanuel Emeka; Arukalam, Okechi Innocent
    This study evaluated the thermodynamic and adsorption properties of aqueous extract of Codiaeum Variegatum Brilliantissima - Zanzibar (Wire Croton) as an inhibitor of mild steel corrosion in 1 M HCl base stock solution using gravimetric measurement focused on the effect of immersion time, inhibitor concentration and temperature. The result showed that the adsorption of the cold aqueous extracts of Wire Croton on mild steel surface favored Langmuir adsorption isotherm as supported by an overall correlation coefficient (R2) close to unity. The equilibrium constant of adsorption process (Kads) for Wire Croton inhibitor evaluated mathematically is 0.0106, 0.0131, 0.1276, 0.1171 and 0.0269 (mg/L) with free energy of adsorption (∆Goads) values of 1.345, 0.821, -5.256, -5.182 and -1.445 kJ/mol for concentrations of 73.6, 147.2, 220.8, 294.4 and 368 mg/L exposed to 303, 313, 323, 333 and 343 K respectively. The small values of Kads suggest weak adsorption which is corroborated by the low negative values of the free energy of adsorption, ∆Goads, values obtained from thermodynamic measurements. The adsorption of Wire Croton inhibiting particles on the mild steel surface was favorable from thermodynamic point of view since values of ∆Goads for more concentrations of the inhibitor were negative and provided proof that aqueous extract of the inhibitor is an efficient inhibitor. 1 Zanzibar as Inhibitor of Mild Steel Corrosion in M HCl. Journal of Newviews in Engineering and Technology. 2(4), 1 – 13. 1. INTRODUCTION: Corrosion continuous to pose serious challenge to infrastructure causing loss in revenue (Izionworu et al., 2021; NACE, 2016). The use of inorganic and organic inhibitors such as volatile inhibitors, Passivating inhibitors, Film inhibitors and Cathodic inhibitors has been welcomed in the past, particularly in the oil and gas field operations where they have yielded positive results in terms of reduced failure of installations and hence increased revenue. Although some level of successes has been recorded in the use of inorganic and organic inhibitors in corrosion control according to Chauhan et al. (2021), there are issues around their environmental suitability and health implications (Finsgar & Jackson, 2014; Umoren & Solomon, 2014).
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    Unraveling the sorption mechanisms of ciprofloxacin on the surface of zeolite 4A (001) in aqueous medium by DFT and MC approaches
    (Elsevier Ltd, 2024-02) Djioko, Fredy Harcel Kamgang; Fotsop, Cyrille Ghislain, Youbi; Youbi, Georges Kamgang; Nwanonenyi, Simeon, Chukwudozie; Madu, Chinyere Ada; Oguzie, Emeka Emmanuel
    The adsorption mechanism of ciprofloxacin (CIP) and its ionic form were investigated using density functional theory (DFT) and molecular dynamics (MD), with the goal of forecasting their adsorption behavior in terms of gap energy, global reactivity descriptors, Fukui functions, adsorption energies, and density of state on the surface of zeolite 4A (001). Quantum chemical parameters related to the adsorption process were calculated, as well as the overall reactivity. According to DFT calculations, the zwetterionic form CIP± are the most stable and reactive and have a greater power of electron transfer compared to the other species. Under aqueous conditions, zeolite can adsorb ciprofloxacin (CIP) and its ionic forms, as revealed by molecular dynamics simulation. Ciprofloxacin in the zwitterionic form (CIP±) were more efficiently adsorbed to the surface of zeolite 4A (001) than the cationic (CIP+), anionic (CIP−), and neutral(CIP) forms; through the evaluation of adsorption energy, probability distribution, interaction, and density of state. The results also demonstrated that the compounds studied were adsorbed via the process of chemical bonding, which was confirmed by the negative values of the interaction energy. Furthermore, the negative adsorption energy values suggest a significant adsorption of all compounds, with electrostatic interactions (physisorption), diffusion into the pores, and n-π bonds (chemisorption) on the zeolite surface. The increase in adsorption energies and the proximity of the molecules studied to the zeolite surface indicate the predominance of chemisorption, and the adsorption of ciprofloxacin was found to be an exothermic and spontaneous process. Molecular dynamics (MD) modeling was in agreement with the DFT results