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The corrosion inhibition behavior of sodium nitrite (NaNO2) towards pure copper (99.95%) in simulated cooling water (SCW) was investigated by means of electrochemical impedance spectroscopy (EIS) and dynamic electrochemical impedance spectroscopy (DEIS). NaNO2 interferes with metal dissolution and reduce the corrosion rate through the formation or maintenance of inhibitive film on the metal surface. Surface morphologies illustrated that the surface homogeneity increased on adding sodium nitrite. Sodium nitrite’s adsorption on copper surface followed the modified form of Langmuir, Freundlich and Frumkin isotherms. Physiosorption mode was involved in the corrosion protection. Electrochemical results revealed an corrosion resistance of copper increases on increasing the inhibitor concentration. The DEIS results indicated that copper corrosion mechanism could be hindered by 50% even after interval of 24 h by optimum concentration of sodium nitrite. The maximum inhibition was achieved with 2000 ppm of NaNO2. With this concentration, inhibition efficiency of up to 61.8% was achievable.

The quantitative structure–property relationship (QSPR) models of the inhibition efficiency of seventeen α-amino acids for copper in acidic medium to their calculated reactivity indicators were developed. DFT calculations and Monte Carlo simulations were employed to find out these indicators. Both multi-linear regression (MLR) and artificial neural network (ANN) methods were employed. The most relevant global descriptors were selected using the simulated annealing algorithm. The QSPR studies showed that the inhibiting performance of the investigated compounds was influenced by their electronegativity, LUMO energy, fraction of electron transferred and total negative charge. The results show that the ANN based model exhibits a great predictive performance compared with MLR model according to correlation coefficient and the root-mean-squared error. In addition, this indicates that the corrosion inhibition of copper by these α-amino acids is mainly a complex phenomenon. Moreover, by analysis of local reactivity indicators and using the ANN constructed model, ten new designed derivative compounds with their predicted inhibition efficiency were proposed. Keywords: Corrosion, Modeling, DFT, Monte Carlo, Simulated annealing, QSPR

The electrochemical oxidation of the Rhodamine B dye (Rh-B) was carried out using dimensionally stable type anode (DSA, Ti/Ru0.3Ti0.7O2). The work was performed using the electrochemical flow cell system. The effect of several operating factors, such as supporting electrolytes, current density, electrolysis time, temperature, and initial concentration of Rh-B dye, were investigated. The UV-visible spectroscopy and chemical oxygen demand (COD) measurements were conducted to monitor the removal and degradation of Rh-B. The best color removal achieved was found to be 98.3% after 10 min applying 3.9 mA·cm−2 as a current density using 0.07 mol·L−1 of NaCl. Meanwhile, the highest COD removal rate (93.0%) was obtained for an applied current density of 3.9 mA·cm−2 as the optimal operating condition after 180 min reaction time, with 2.98 kW h·m−3 as energy consumption. This shows that the best conditions for color removal are not certainly the same as those for the COD removal. The rises in the concentration of NaCl, and applied current increased the Rh-B color removal rate. The decline in Rh-B dye concentration followed pseudo-first-order kinetics. The obtained values of apparent rate constant were increased by increasing chloride ion concentration. It is concluded that the electro-oxidation on DSA electrode using a flow cell is a suitable process for the removal of Rh-B dye in aqueous solutions.

Biopolymers-based compounds were used by different manners for metal protection toward corrosion phenomena, namely via inhibiting additive and coating strategies. In the last decade, the application of these compounds or their chemically modified forms as effective replacements for toxic inorganic and organic inhibitors attracts more attention. Additionally to their intrinsic chemical stability, biodegradability, eco-friendly, low cost and renewability, biopolymers set were shown the remarkable effect to control the dissolution of several metallic materials in various corrosive environments. Among a large variety of available biopolymers, chitosan and its functionalized form, as well as its nanoparticle composites, have been reported and widely used as good anti-corrosion compounds for different metal/medium systems. In this context, the current chapter aims to shed more light on this subject.

Herein, the effect of a mediums' pH on the interfacial interactions between proline (Pro) amino acid and tin metal was studied. In this work, acidic and near-neutral pH values were considered. DFT-based calculations and Monte Carlo simulations were carried out in the aqueous phase to understand the role of pH in Pro/tin interactions. To confirm this role in terms of inhibition efficiency, the CC and AC electrochemical techniques were used. Based on the calculated parameters, it was outlined that the partially protonated Pro form exhibits significant affinity to interact with tin metal in near-neutral media. However, in acidic media, its affinity is decreased, whereas the full protonated form was found to be solvated in the solution and its interaction with the tin surface was not favorable. These findings indicated that the inhibition capability of Pro for tin could be better in near-neutral media than in acidic media. This expected behavior was confirmed experimentally, wherein an inhibition effectiveness of around 65% was obtained for Pro at pH 5, and 16% was observed at pH 2. Additionally, the results highlight the capability of employing computational studies to predict the prevention efficiency of anti-corrosion compounds by varying the solution pH.

Made available in DSpace on 2018-12-11T17:36:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-04-01 Surface water contamination by dyes released from a variety of industries is an environmental problem of great concern. However, electrochemical oxidation is a promising alternative for water treatment. In this paper, we studied the electrochemical oxidation of Rhodamine B (RhB) dye on the Ti/RuO2-IrO2 (DSA®) and SnO2 anodes comparing their efficiencies. The effect of some parameters, such as current density, initial pH (pH0), nature, concentration of electrolyte and temperature at the electrochemical oxidation was investigated evaluating the decolorization and the chemical oxygen demand (COD) removal at optimal conditions. Complete decolorization of RhB was achieved in the presence of chloride ions at different times using both electrodes. An optimum efficiency was obtained at pH 6.5, T°C. Also, the current density of 40cm-2 using the DSA electrode in NaCl 0.05L-1+ Na2SO4 0.1L-1 mixture solution as a supporting electrolyte, 100% color removal and 61.7% chemical oxygen demand removal after 90min of electrolysis were achieved. DSA showed better performance than SnO2 in wide operating conditions and was proved to be more cost-effective and more efficient. The effectiveness of the degradation is explained by indirect electrochemical oxidation, where in the presence of chlorides electrolyte leads to the electro-generation of strong oxidant species, such as Cl2 and ClO- ions, improving the efficiency of treatment at both electrodes. Applied Chemistry-Physic Team Faculty of Sciences IBN ZOHR University, B.P. 8106 Cité Dakhla Universidade Estadual Paulista (Unesp) Instituto de Química, Araraquara. Av. Prof. Francisco Degni 55 Universidade Estadual Paulista (Unesp) Instituto de Química, Araraquara. Av. Prof. Francisco Degni 55

Cysteine's action on 3003 aluminum alloy dissolution in a 2% NaCl solution, at different pH values, has been investigated. Weight-loss measurements, potentiodynamic polarization and electrochemical impedance at OCP were performed. The surface morphology was analyzed by SEM. The main results showed that the alloy underwent severe corrosion at 2 and 11 pH values, as compared to at 5 and 8 pH values. Furthermore, a duality effect of cysteine was noted, as it acted as a corrosion inhibitor or accelerator, depending on its concentration, and on the solution's pH value. This particular behavior can be related to the instability of the formed film adsorbed onto the metal surface. All these findings show the high complexity of cysteine action on 3003 aluminum alloy, under the investigated conditions.

The valorization of biomass and the use of plant extracts as new green inhibitors of scaling are among the most innovative research topics. In this light, this study aims to evaluate the effectiveness of two extracts of Crocus Sativus L (CSL) wastes towards the formation of calcareous scale, namely the Aqueous Extract of Leaf (ALE) and the Aqueous Extract of Petal and Stamen (AEPS). Folin-Ciocalteau and colorimetric methods are used to determine the total polyphenols and flavonoids contents, respectively. Then, the anti-scaling property of the investigated extracts is determined using a conductivity test and the Laboratory of Chemistry and Genie of the Environment (LCGE) technique at a temperature of 25 °C. After that, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses are employed to examine the formed scale during the LCGE tests. To support the experimental findings, Molecular Dynamic (MD) simulations and Density Functional Theory (DFT) calculations are carried out. The data obtained revealed that AEPS has a higher concentration of total polyphenol and flavonoids than ALE. Total inhibition occurs after the addition of 60 mg‧L-1 of AEPS to the calco-carbonic solution with a hardness of 40°F. Whereas an amount of 82 mg‧L-1 of ALE was the optimal concentration to completely inhibit CaCO3 formation. This allows us to conclude that the anti-scaling effectiveness is correlated with polyphenols and flavonoids contents in CSL extracts. SEM and FTIR analyses reveal that the crystallization of CaCO3 without inhibitor was a stable variety of calcite with a rhombohedral form. However, the presence of a low concentration of AEPS (20 mg‧L-1) resulted in a significant modification on the morphology of CaCO3 and a mixture of vaterite with calcite phases. The theoretical outcomes agree with the anti-scaling efficiencies reported experimentally. Based on these results, the CSL biomass could be an interesting renewable source of eco-friendly and inexpensive inhibitors of scaling.

The present study aims to assess the performance of Tannic acid (TA), a natural polyphenol, as a new eco-friendly inhibitor on the deposition scale of calcium carbonate. The conductivity test and the Laboratory of Chemistry and Genie of the Environment (LCGE) technique are used to evaluate the anti-scaling property of TA. The dispersion property of CaCO3 is also investigated using UV–visible method. To characterize the morphology and crystal structure of the formed scale during the LCGE tests, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses are utilized. Then, Molecular dynamic simulations are carried out to prove theoretically the ability of TA molecule to inhibit CaCO3 scaling. Results show that the addition of a low concentration of TA (7.8 mg L −1) inhibits completely the precipitation of calcium carbonate of calco-carbonic solution with a hardness of TH = 40 ° F (1 ° F = 4 mg L −1 of calcium ions) at 25 °C. We recorded also that TA has a good dispersion property of CaCO3. It was observed that the scales formed in the absence of TA are regular rhombohedral forms. However, in the presence of a low concentration of TA (2 mg L −1) the significant modification in the crystal morphology and the crystal sizes are noted. XRD diffractogram reveals that CaCO3-calcite is the main polymorph formed during the tests without inhibitor. Nevertheless, in the presence of inhibitor, a mixture of vaterite and calcite was obtained. The geometrical and energetic analyses of the interfacial interactions of TA inhibitor with calcite (1 1 0) and (1 0 4) surfaces proved its enhanced capacity to interact with calcite crystals. These findings explain the good obtained scale inhibition efficiency of TA. Consequently, we suggest the use of TA as a new eco-friendly inhibitor for calcareous scaling.

Elevated concentrations of nutrient in wastewater discharge can lead to severe imbalance water-ecosystems due to eutrophication, therefore, efficient and cost-effectiveness remediation strategies are urgently required. This work reports the feasibility of using zirconium-modified Merlinoite (Zr@Merl) obtained from Mexican coal fly ash (CFA) for the removal of phosphate ions from aqueous solutions. Direct method and soft reaction conditions were employed to synthesis Merlinoite (Merl) in more than 100% yield related to CFA. Further, the Merl surface was modified by ZrO2+ through the microwave-assisted process at 130 °C for 5 min. Inductively coupled plasma confirmed the increase of Zr(IV) content up to 7.07 wt% while the potassium concentration decreased from 11.53 to 5.66 wt%, indicating the successful exchange in the Merl surface. The pristine Merl and its Zr@Merl were physicochemically characterized. X-ray photoelectron spectroscopy analysis before and after phosphate ions adsorption was done to elucidate the involved adsorption mechanism. The adsorption behavior was explained by pseudo-second-order and Freundlich models. The maximum adsorbed amount was 67.72 mg g−1. The results proved that the involved mechanisms for the phosphate sorption onto Zr@Merl were electrostatic attractions followed by coordination reactions. Further, a theoretical study using Monte Carlo/SA simulations was applied to get insight into the interaction between Merl and Zr@Merl surface groups and H2PO4− ions. The simulation results demonstrate the favorable adsorption, more stable and spontaneous, onto Zr@Merl than Merl. Overall, Zr@Merl could serve as a cost-effective and reusable adsorbent material for the phosphate recovery from aqueous effluents.

The bi-heterocyclic system, namely 2-[(5-methylpyrazol-3-yl) methyl] benzimidazole (MPMB) has been synthesized and characterized by 1H and 13C NMR methods. Its inhibitory property for carbon steel (C38) in 1 M HCl solution has been investigated using electrochemical impedance spectroscopy, potentiodynamic polarization, and weight loss measurements at 293 K. Besides, DFT/B3LYP-based calculations and Monte Carlo simulations are used under the solvation condition. The inhibition efficiency increases with the inhibitor concentration and attains a maximum value of 97.0% at 5 mM. The polarization curves show that the examined compound act as a mixed type inhibitor. The increase of temperature induces a decrease in the inhibition efficiency of the studied compound. Also, the adsorption of this compound obeyed the Langmuir adsorption isotherm. The carbon steel surface examination confirmed the presence of a protective adsorbed film of MPMB on the surface. According to the computational results, MPMB in its neutral and protonated forms exhibited an accurate affinity to adsorb onto the metal surface, which leads to the formation of a protective film.

Herein, the inhibition behavior of alginate biopolymer with different chain length (fragments) on corrosion of Fe (110), Cu (111), Al (111) and Sn (001) surfaces in acidic medium was investigated using quantum chemical calculations and molecular mechanic methods. Based on HSAB's theory, local and global reactivity indicators of different alginate fragments were calculated using DFT/B3LYP/3-21G method. Molecular mechanic simulations were employed to describe quantitatively and qualitatively the adsorption behavior of the bio-inhibitor on the metal surfaces. As a result, the chain length of alginate and metal nature were considerably affected magnitude and trend of alginate/metal interactions. Gradually as the chain length of the alginate molecule was increased, the binding energy increased. On the other hand, it found that the binding of alginate onto metal surfaces followed this order: Sn (001)

In the aim to understand the inhibition action of three 1,5-benzodiazepin-2-one derivatives (i.e. DMBD: 4,7-dimethyl-1,5-benzodiazepin-2-one, PBD: 3-phenyl-1,5-benzodiazepin-2-one, MPBD: 4-methyl-7-phenyl-1,5-benzodiazepin-2-one) against the dissolution of iron in acidic medium, both DFT-based calculations and Monte Carlo-SAA simulations were carried out. As a result, the protonation process was unfavorably affected the reactivity of investigated inhibitors. Further, the solvation free energy (∆GSolv) can be used as a parameter to inspect the inhibition performance of organic inhibitors. According to Monte Carlo-SAA simulations, the investigated inhibitors exhibited a great tendency to replace pre-adsorbed corrosive entities onto the iron surface and then forming a protective film via a parallel adsorption orientation. Finally, a predicting study pointed out that the MPBD compound is expected to act as a moderate inhibitor for aluminum and copper metals, while lower inhibition efficiency is anticipated in the case of tin in acidic environments.

Nowadays, theoretical calculation tools have become powerful in predicting the behavior of corrosion inhibitors on the surface of metals and, therefore, avoiding energy consumption and the cost of experimental tests. This work aims to predict the inhibitory power of some furan derivatives on Cu (111), Fe (110), Al (111) and Sn (111) surfaces in acidic media. For this purpose, three furan derivatives&mdash, furan-2-carbaldehyde (FF1), 5-(hydroxymethyl)furfural (FF2) and 5-(hydroxymethyl)furoic acid (FF3)&mdash, have been selected to compare their intrinsic properties against corrosion as well as their behavior on iron (Fe), copper (Cu), aluminum (Al) and tin (Sn) surfaces in acid medium. Typically, the anti-corrosive properties of FF1, FF2 and FF3 were studied by using quantum chemical calculations and Monte Carlo simulations. Density Functional Theory (DFT), lowest unoccupied (ELUMO) and highest occupied (EHOMO) molecular orbital energies, energy gap (∆E), chemical hardness (&eta, ), softness (&sigma, ), electronegativity (&chi, ), electrophilicity (&omega, ) and nucleophilicity (&epsilon, ) have been calculated and discussed. Theoretical vibrational spectra were also calculated to exhibit the functional groups in the selected chemicals. On the other hand, the adsorption behaviors of FF1, FF2 and FF3 were studied on the Fe(110), Cu(111), Al(111) and Sn(111) surfaces. As a result, the adsorption energies of all molecules are ordered as Fe(110) &lt, Cu(111) &lt, Al(111) &lt, Sn(111) and FF3 seems to be more effective as a corrosion inhibitor due to the existence of both carboxylic acid and hydroxyl groups, which consist of favorable sites of adsorption into the metal surface.