Corrosion protection of mild steel in hydrochloric acid up to 313 K using propyl benzimidazole: Electroanalytical,adsorption and quantum chemical studies

The inhibition efficiency of propyl benzimidazole for mild steel in hydrochloric acid in three different concentrations at 303, 308 & 313 K have been studied by polarization, electrochemical impedance spectroscopy, adsorption, surface studies and basic computational calculations. The inhibition efficiencies and the global chemical reactivity relate to total energy, E_HOMO, E_LUMO and gap energy (ΔE). Propyl benzimidazole interact with mild steel surface through adsorption and the process of adsorption follow Langmuir isotherm model. The inhibition efficiency increases with concentration and reaches maximum at 150 ppm. The increase in temperature have an inverse relationship with protection efficiency. The corrosion inhibition efficiencies and the global chemical reactivity relate to total energy, E_HOMO, E_LUMO and gap energy (ΔE).     

Olefin plant spent caustic wastewater treatment using electro-Fenton technique

The aim of this research was to reduce the chemical oxygen demand (COD) and sulfide from a spent caustic wastewater using electron-Fenton technique. The experiments were applied to evaluate the effect of several parameters such as pH, reaction time, current density mA/cm², H₂O₂/Spent Caustic Wastewater (SCW) (ml/l), H₂O₂/Fe²⁺ molar ratio on the performance of the process. The response surface methodology (RSM) was applied to minimize the number of runs and investigate the optimum operating conditions. Five independent variables were carefully considered and optimized in this paper. The optimum conditions were found at pH of 2.96, reaction time of 70.67 min, current density of 58.85 mA/cm², H₂O₂/SCW of 1.59 ml/l, H₂O₂/Fe²⁺ molar ratio of 3.47 for 81.20 COD removal while the optimum conditions were found at pH of 2.87, reaction time of 65.52 min, current density of 55.47 mA/cm², H₂O₂/SCW of 1.38 ml/l, H₂O₂/Fe²⁺ molar ratio of 3.21 for 99.9998 sulfide removal.     

Adsorption and inhibition behavior of a novel Schiff base on carbon steel corrosion in acid media

In this study, the inhibition effect of 2,2′-(heptane-1,7-diylbis(azanylylidene)bis-(methanylylidene))diphenol (HAMD) on carbon steel corrosion in 0.5 mol L⁻¹ H₂SO₄ solution was studied. Weight loss and electrochemical techniques such as open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to inspect the efficiency of HAMD as corrosion inhibitor. Scanning electron microscopy (SEM) and energy dispersion X-ray (EDAX) were used to characterize the steel surface. Polarization measurements indicated that, the studied inhibitor acts as mixed-type inhibitor. The adsorption of HAMD molecules on the carbon steel surface obeys Langmuir adsorption isotherm.     

Corrosion inhibition efficiency of water soluble ethoxylated trimethylol propane by gravimetric analysis

Polyoxyethylenated trimethylol propane monolaurate surfactants with varied ethylene oxide content were tested as corrosion inhibitors via the weight loss method. Weight loss measurements for carbon steel dissolution were performed in 1 N HCl containing different inhibitor concentrations at 30, 40 and 50 °C. These measurements were utilized for calculating corrosion rate, surface coverage area and percentage inhibition. The obtained data show that the adsorption of these inhibitors obeys Langmuir adsorption isotherm. Thermodynamic parameters (ΔG¹, ΔH¹ and ΔS¹) of the corrosion process are evaluated and correlated to inhibitors structures.     

Experimental and modeling studies of the effects of different nanoparticles on asphaltene adsorption

Adsorption experiments for three commercial metal oxide nanoparticles (SiO₂, Al₂O₃, and MgO) were carried out to examine the effect of each nanoparticle on asphaltene inhibition. The results are reported on the basis of adsorption per mass of adsorbent. The adsorption data were used in four isotherm adsorption models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models) for better understanding of adsorption mechanisms. Among the models, Dubinin-Radushkevich produced better prediction. According to the obtained data, the adsorption affinity toward asphaltene was in the following order: SiO₂ > MgO > Al₂O₃. Influence of the main factors such as surface chemistry and specific surface area shows significant effect on the amount of adsorption. It was found that the multilayer adsorption and physisorption mechanism plays an important role in asphaltene adsorption, which was confirmed by Freundlich, Temkin, and Dubinin-Radushkevich models.     

Bio-sorption for tannery effluent treatment using eggshell wastes; kinetics,isotherm and thermodynamic study

Since, cobalt, zinc, mercury and lead ions are high toxic heavy metals; this work aims to investigate the efficiency of eggshell as a low cost sorbent for their ions from aqueous solution. Adsorption of heavy metals on surfaces of eggshell obeyed second order kinetics. Adsorption isotherm belonged to Freundlich model and displayed multilayer adsorption. The maximum adsorption capacity was estimated as 204, 153, 121 and 98 mg/g for Co³⁺, Zn²⁺, Hg²⁺ and Pb²⁺ respectively. The values of free energy of adsorption evidenced the physical adsorption occurrence. It is demonstrated that eggshell, as an industrial waste, was efficiently used as an adsorbent for wastewater treatment. Eggshells powder removed efficiently heavy metal ions from a tannery wastewater and removal efficiency reached up to 99%.     

Optimization,kinetics, physicochemical and ecotoxicity studies of Fenton oxidative remediation of hydrocarbons contaminated groundwater

Fenton oxidation remediation of hydrocarbons contaminated groundwater was investigated for efficiency and effectiveness. 10% pollution was simulated in the laboratory by contaminating groundwater samples with diesel and domestic purpose kerosene (DPK) in two different experimental set ups. Optimum conditions of concentrations of the treatment solutions and pH were established: 300 mg/L (FeSO₄), 150,000 mg/L (H₂O₂) and pH = 3 for the kerosene contaminant; 100 mg/L (FeSO₄), 300,000 mg/L (H₂O₂) and pH = 3 for the diesel contaminant. The results from kinetics study show that the remediation process is pseudo-first order reaction with a rate constant of 8.07 × 10⁴ mgL^?1hr^?1 and 3.13 × 10⁴ mgL^?1hr^?1 for the diesel and kerosene contaminants in that order with 95.32% and 79.25% reduction in chemical oxygen demand (COD) for diesel and kerosene contaminated samples at the end of the remediation process respectively indicated that remediation have occurred significantly. Percent reduction in Total Petroleum Hydrocarbon (TPH) as kerosene was 89.84% and that of the diesel contaminant as 91.87% after 6 hours of remediation. The general pollution index (GPI) for the hydrocarbons contaminated samples was in the range of 6.70–7.52 against the background value of 4.39 for the control groundwater sample. After treatment the GPI had dropped to 4.13–4.43 which depicts remarkable remediation although the samples remained impaired. Therefore there is the need of post-treatments to make the groundwater fit for domestic and agricultural uses. The application of the Fenton oxidative process is found to be very efficient, effective and rapid in reducing total petroleum hydrocarbon as kerosene and diesel as target contaminants.     

Kinetics of thermal degradation of a Japanese oil sand

Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, and 30 °C/min), and 30 ml/min air flow rate have been investigated. The kinetic parameters have been calculated based on three stages of weight loss and/or the conversion of the sample. These include, stage 1 (SI): volatilization of moisture content and the light hydrocarbon (20–227 °C), stage 2 (SII): combustion of heavy hydrocarbon (227–527 °C), and stage 3 (SIII): oxidative decomposition of carbonaceous organic matter (502–877 °C). The results showed that the rate of change of the oil sand conversion with time $\left(\frac{d\alpha }{\mathit{dt}}\right)$ was affected by the heating rate. The time taken by the system to reach 0.99 conversion was observed as 85, 50, and 35 min at the heating rates of 10, 20, and 30 °C/min, respectively. The frequency factor, A, at SI was between 0.09 and 0.54 min^?1, while the activation energy, E_a, was 11.2–12.5 KJmol^?1 (the percentage weight loss, W_t, was 0–3.6 %w/w; and the conversion, α, was 0–0.2.). At SII, the values of A and E_a were 2.1–5.5 min^?1 and 17.6–19 KJmol^?1, respectively (W_t = 3.1–15.88 %w/w; α = 0.17–0.86.). The value of A at SIII was 5.5E11–1.1E13 min^?1, while E_a was 160–200 KJmol^?1 (W_t = 15.33–17.99 %w/w; and α = 0.84–0.99).     

Evaluation of a novel cationic surfactant based on 2-(2 (dimethylamino)ethoxy)ethanol as a corrosion inhibitor for carbon steel 1018 in 1.0 M HCl solution

Corrosion inhibition of a novel cationic surfactant namely, N-(2-(2-hydroxyethoxy)ethyl)-N,N-dimethyldodecan-1-aminium bromide (HEDDB) was evaluated as a corrosion inhibitor for carbon steel in 1.0 M HCl by electrochemical frequency modulation (EFM), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. Results of Tafel polarization exhibit that the synthesized surfactant HEDDB behaves as mixed-type inhibitor. The effectiveness of temperature on the corrosion rate which evaluated by chemical technique (weight loss) was investigated and assessed. Langmuir’s adsorption isotherm was the preferable fitted isotherm. The results of weight loss clarified that the efficiency of the synthesized surfactant increases with raising both the concentration of the surfactant and the temperature. HEDDB effectiveness on the morphology of metal surface was monitored by Atomic Force Microscopy (AFM) and Scanning Electron Microscope (SEM) techniques. Quantum chemical technique has been employed to discuss the inhibition efficiency by effectiveness of molecular structure of the synthesized inhibitor. The various techniques which used in this research have inhibition efficiency (IE) with the same direction.     

Corrosion inhibition efficiency of linear alkyl benzene derivatives for carbon steel pipelines in 1M HCl

Linear alkyl benzene sulfonic acid (L) and three of its ester derivatives (L1, L2, L3) were prepared, followed by quaternization of these esters (L1Q, L2Q, L3Q). The corrosion inhibition effect on carbon steel in 1 M HCl was studied using weight loss and potentiodynamic polarization measurements. The adsorption of the inhibitors on carbon steel surface obeyed the Langmuir’s adsorption isotherm. The associated activation energy of corrosion and other thermodynamic parameters such as enthalpy (ΔH¹), entropy (ΔS¹) of activation, adsorption–desorption equilibrium constant (K_ads), standard free energy of adsorption (ΔG^o_ads), heat (ΔH^o_ads), and entropy of adsorption (ΔS^o_ads) were calculated to elaborate the corrosion inhibition mechanism.     

Adsorption separation of condensate oil from produced water using ACTF prepared of oil palm leaves by batch and fixed bed techniques

A novel method is applied to produce amorphous carbon thin film (ACTF) from oil palm leaves. The novel prepared ACTF is in the form of thin films like graphene sheets having winding surface. ACTF was characterized by different methods of characterization: FTIR, BET, SEM, EDX, TEM, and Raman. ACTF employed as an adsorbent to separate emulsified condensate oil from synthetic produced water as a treatment process before reinjection in oil reservoirs. The adsorption performance of batch and fixed bed adsorption systems were investigated. Contact time, initial concentration of condensate oil ($C_o$ = 100–2500 mg/l) and temperature were studied by batch experiments. The obtained results indicated that the adsorption capacity and the removal efficiency increased with time up to 132.77 mg condensate/g adsorbent and 66.38% respectively, within 6 h equilibrium time at 308 K. The thermodynamic adsorption experiments conducted at 288, 308 and 318 K, referring exothermic nature of the adsorption process.The performance study of fixed bed adsorption described through the breakthrough curves concept with two parameters: column bed heights (5, 10 and 15 mm) and flow rate (2.2, 5 and 8.4 ml/min). Two models (Thomas and Yoon-Nelson models) were applied to expect different parameters of fixed bed as adsorption capacity and time need for 50% breakthrough. The results exhibited that 2.2 ml /min feed flowrate and 5 mm bed height at 1000 mg/l initial oil condensate concentration were the optimum conditions for the ACTF column. The experimental breakthrough curves showed acceptable fit with the calculated breakthrough profiles obtained by Thomas model.     

Surface protection of mild steel in acidic chloride solution by 5-Nitro-8-Hydroxy Quinoline

The effect of commercially available quinoline nucleus based pharmaceutically active compound 5-Nitro-8-Hydroxy Quinoline (NHQ) against the corrosion of mild steel (MS) in 1 M acidic chloride (HCl) solution was investigated by chemical (weight loss – WL) and electrochemical (Tafel polarization, Linear polarization and Electrochemical impedance spectroscopy) techniques. From all the four methods, it is inferred that the percentage of inhibition efficiency increases with increasing the inhibitor concentration from 50 to 300 ppm. The adsorption behavior of inhibitor obeyed through Langmuir isotherm model. Thermodynamic parameters were also calculated and predict that the process of inhibition is a spontaneous reaction. EIS technique exhibits one capacitive loop indicating that, the corrosion reaction is controlled by charge transfer process. Tafel polarization studies revealed that the investigated inhibitor is mixed type and the mode of adsorption is physical in nature. The surface morphologies were examined by FT-IR, SEM and EDX techniques. Theoretical quantum chemical calculations were performed to confirm the ability of NHQ to adsorb onto mild steel surface.     

Preparation and characterization of sulfonated polystyrene/magnetite nanocomposites for organic dye adsorption

Magnetite nanoparticles (MNPs) were prepared by co-precipitation method and were found to have average size of 5 nm with spherical shape crystalline structure with super-magnetic properties. Commercial polystyrene (PS) was sulfonated through the reaction with freshly prepared acetyl sulfate. Three different degrees of sulfonation, based on the ratio of the acetyl sulfate to polystyrene, were prepared (1:1, 1:3 and 1:5). Nanocomposites of the prepared magnetite nanoparticles 1:3 sulfonated polystyrene were prepared at different magnetite content (1, 5 and 10%). The produced materials were characterized by dynamic light scattering (DLS), transmittance electron microscope (TEM) X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). PS, MNPs and the prepared nanocomposites were investigated as adsorbents for Congo Red (CR). The variables influencing the adsorption capacity, such as solution pH, contact time and the initial dye concentration were systematically investigated. The adsorption for CR by the previous adsorbents show maximum experimental uptake capacity of 26.78, 33.15, 53.35, 64.73, and 76.29 mg/g for PS, MNPs, SPS/MNPs 1%, SPS/MNPs 5% and SPS/MNPs 10%, respectively. The adsorption process was found to follow the pseudo second order kinetic model and fit quite well with Langmuir adsorption isotherm.     

Novel naphthenate surfactants based on petroleum acids and nitrogenous bases as corrosion inhibitors for C1018-type mild steel in CO2-saturated brine

The efficiency of two natural naphthenate surfactants (Naphthenic-dimethylamine and Naphthenic-diethylamine complexes), as corrosion inhibitors for mild steel in CO₂-saturated 1% NaCl solution, has been determined by linear polarization resistance corrosion rate and potentiodynamic polarization measurements. These compounds inhibit corrosion even at very low concentrations (25 ppm), and Naphthenic-diethylamine complex is the best inhibitor giving maximum inhibition efficiency (99.76) at 100 ppm. Polarization curves indicate that, the two investigated compounds are mixed inhibitors, affecting both cathodic and anodic corrosion currents. Adsorption of naphthenate surfactants on the mild steel surface is in good agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy values confirm the chemical nature of the adsorption. Energy dispersive X-ray fluorescence microscopy (EDRF) and scanning electron microscope (SEM) observations confirmed the existence of such an adsorbed film on the mild steel surface.     

Physicochemical studies on the inhibitive properties of a 1,2,4-triazole Schiff’s base,HMATD, on the corrosion of mild steel in hydrochloric acid

The efficiency of 4-(4-hydroxy-3-methoxy benzyledene amino)-4-H-1,2,4-triazole-3, 5-dimethanol, HMATD, as corrosion inhibitor for mild steel in 0.5 M HCl has been determined by weight loss measurements and electro analytical methods. The influence of various parameters such as temperature, inhibitor concentration on the efficiency has been studied. The electrochemical impedance spectroscopic measurements revealed the inhibition action of HMATD by reducing the charge transfer through metal solution interface. Polarization curves indicate the mixed type behaviour of HMATD. The inhibitor molecule functions by blocking the active sites on metal surface by adsorption and which obeys the Langmuir adsorption isotherm. Various kinetic and thermodynamic parameters have also been calculated.     

Characterization of biosurfactants produced by novel strains of Ochrobactrum anthropi HM-1 and Citrobacter freundii HM-2 from used engine oil-contaminated soil

Microbial surfactants are widely used for industrial, agricultural, food, cosmetics, pharmaceutical, and medical applications. In this study, two bacterial strains namely, Ochrobactrum anthropi HM-1 and Citrobacter freundii HM-2, previously isolated from used engine oil contaminated soil, and capable of producing biosurfactants, were used. Their cell-free culture broth showed positive results toward five screening tests (hemolysis in blood agar, drop collapse, oil displacement, emulsification activity (E₂₄), and surface tension (ST) reduction). They reduced the ST of growth medium (70 ± 0.9) to 30.8 ± 0.6 and 32.5 ± 1.3 mN/m, respectively. The biosurfactants were classified as anionic biomolecules. Based on TLC pattern and FT-IR analysis, they were designated as glycolipids (rhamnolipid). Waste frying oil was feasibly used as a cheap and dominant carbon source for biosurfactants production; 4.9 and 4.1 g/l were obtained after 96 h of incubation, respectively. Compared with non-irradiated cells, gamma-irradiated cells (1.5 kGy) revealed enhanced biosurfactant production by 56 and 49% for HM-1 and HM-2, respectively. The biosurfactants showed good stability after exposure to extreme conditions [temperatures (50–100 °C for 30 min), pH (2–12) and salinity (2–10% NaCl)], they retained 83 and 79.3% of their E₂₄, respectively, after incubation for a month, under extreme conditions. Biosurfactants effectively recovered up to 70 and 67% of the residual oil, respectively, from oil-saturated sand pack columns. These biosurfactants are an interesting biotechnological product for many environmental and industrial applications.