Search

The chelating ion exchange resin Puromet MTS9600 was employed for the separation of platinum group metals (PGMs), specifically Pt(IV), Pd(II), and Rh(III) from acidic chloride media (0.1–9.0 M HCl). The study investigated the impact of hydrochloric acid, temperature, PGM concentrations, and contact time on the recovery of the PGM-chloro complexes from dilute mixed PGM solutions as could be expected from the leaching of spent automotive catalysts. PGM adsorption onto the resin and loading isotherms were examined. Kinetic and diffusion-based models studies revealed that adsorption of PGM-chloro complexes onto the resin obeys the Ho pseudo-second order model, and intraparticle diffusion is a predominant mechanism controlling the sorption process. PGM desorption from the loaded resins was performed using various eluants. The effective recovery of Pt(IV) and Pd(II) was achieved through the utilization of thiourea, while the elution of Rh(III) did not yield promising results within the applied desorption conditions. A separation flowsheet is proposed for the recovery of Pt(IV) and Pd(II) from chloride solution over Rh(III) using a short contact time. In this process, adsorbed Pd(II) can be completely recovered using a 5 M NH3 solution, while Pt(IV) is eluted with 1 M thiourea. Less than 4% of Rh(III) is recovered in the eluates and mostly remains in the initial PGM solution. [ABSTRACT FROM AUTHOR]

Because conventional inhibitors are nonbiodegradable and harmful, the development of ecofriendly corrosion inhibitors is gaining popularity. The anti-corrosive efficacy of 2-(2-Methyl-5-nitro-1H-imidazol-1-yl) ethanol on carbon steel in an chloride solution was evaluated in this study using a variety of approaches such as electrochemical measurements and computational studies. The results showed that increasing the concentration of 2-(2-Methyl-5-nitro-1H-imidazol-1-yl) ethanol from 0.1 to 3.0 g/L enhanced the inhibition efficiency (IE%) to 90.18-91.71 %. The high ΔE(eV) value of 0.239 and the interaction and binding energies of - 995.45 and 995.45 for 2-(2-Methyl-5-nitro-1H-imidazol-1-yl) ethanol molecules onto Fe (110) substrate were further supported by quantum chemical analytics, which also supported the empirical results. The results show that 2-(2-Methyl-5-nitro-1H-imidazol-1-yl) ethanol has a bright future as an effective and environmentally safe inhibitor for preventing carbon steel from corroding in corrosive media. [ABSTRACT FROM AUTHOR]

The inhibition effect of clove (or Dianthus fruit) extract (DFE):zinc (Zn) complexes against mild steel (MS) dissolution was surveyed with the help of electrochemical, surface analysis, and theoretical procedures. The microstructure of the samples has been studied by energy-dispersive X-ray spectroscopy (EDS), field emission-scanning electron microscope (FE-SEM), and grazing incidence X-ray diffraction (GIXRD) assessments, and the results were evidenced by the DFE:Zn complex inhibitive layer creation. In addition, the constructed complexes over the MS substrate were characterized by Fourier transform infrared spectroscopy (FT-IR). Besides via ultraviolet–visible spectroscopy (UV–Visible), the DFE:Zn complex formation in the saline solution was explored. The results illustrated successful interactions between DFE molecules, cations, and MS surfaces. Also, the Raman achievements have shown that after DFE:Zn (200–600 ppm) adsorption over MS substrate, the D and G bands appeared. Achievements from the conducted electrochemical test confirmed the impactful anticorrosion behavior of DFE:Zn (200–600 ppm) (Rt of about 7000 Ω cm2) via synergistic index value of 9 after 24-h immersion. Also, the high-resolution images from the surface of the inhibited samples illustrated uniform DFE:Zn film construction, and the atomic force microscopy (AFM) analysis evidenced that the surface roughness was lowered after adding optimum concentration of DFE:Zn mixture. Meanwhile, the outcome of the contact angle (CA) analysis illustrated the semi-hydrophilic behavior of the DFE:Zn protected samples. Additionally, the results acquired from detailed-level simulation (density-functional theory (DFT) connected with Monte Carlo/molecular dynamic (MC/MD)) strongly confirmed the surface adsorption capability of the DFE:Zn complexes. [ABSTRACT FROM AUTHOR]

High efficiency of corrosion inhibition of aluminum alloy in a 0.1% NaCl solution with a composition of guar gum and potassium sorbate was established. The formation of an organic adsorption film was found on the surface of the metal samples. The degree of metal protection against corrosion by this inhibitory composition was more than 90%. The results of the research can be used for the development of eco-friendly "green" corrosion inhibitors of aluminum alloys from renewable plant materials. [ABSTRACT FROM AUTHOR]

In response to the quality fluctuations of crude gold powder obtained by reducing gold chloride solutions with high impurity content, an experimental study was conducted on the direct reduction of crude gold powder from low-gold high-impurity chloride solutions using sulfur dioxide gas. The results showed that the gold grade of the obtained crude gold powder can reach more than 99. 95 %, which is high-quality crude gold powder. This method is simple in steps, widely applicable, and has a high recovery rate of valuable metals. It especially overcomes the challenges of cold regions or low-temperature winters, ensuring the stability of the process. [ABSTRACT FROM AUTHOR]

The effect of a Cu addition on the corrosion behavior of 304 austenitic stainless steel in a solution was elaborately investigated through salt spray tests, FeCl3 immersion tests and characterization analyses. The corrosion behavior was further analyzed by optical microscopy, scanning electron microscopy, inductively coupled plasma mass spectrometry and an X-ray photoelectron spectroscopy analysis. 304Cu showed a higher corrosion resistance than 304 after the salt spray tests in a 5 wt.% NaCl solution for 168 h; the beneficial effect of Cu was not obvious after exposure for 480 h. Penetrating (stripped morphology in 304 and fishbone morphology in 304Cu) and non-penetrating dish-shaped pits were both observed on 304 and 304Cu after immersion in a 6 wt.% FeCl3 solution for 72 h; the corrosion rates of 304Cu were much higher than 304. Cu and Cu2+ were the main existing forms in the as-received 304Cu and Cu+ formed with the corrosion in chloride solutions. The results indicated a good corrosion resistance of 304Cu in service. The use of steel in an aggressive environment for a long exposure time should be cautiously considered. [ABSTRACT FROM AUTHOR]

A novel non-plasticized nano-porous hybrid inorganic-organic polymer inclusion membrane (PIM) was synthesized, characterized, and evaluated as an anion exchange membrane for application in electrogenerative processes to recover Pd2+ ions. Ionic liquids 1-ethyl-3-me­thyl­imidazolium chloride (EMIM-Cl) and 1-butyl-3-methylimidazolium chloride (BMIM-Cl) were used as the carrier molecules in the polymeric network of PIM to enhance anion exchange process. This hybrid anion exchange membrane also consists of a polymeric matrix of non-plasticized cellulose triacetate modified by incorporating an inorganic material (silane) prepared by the sol-gel route. Different parameters affecting the ion transport performance efficiency, i.e., the composition of the membrane, type of ionic liquid (carrier molecule) and ion–exchange capacity, were investigated and optimized. In the electrogenerative process, the results revealed that the prepared PIM yields better recovery results for recovering Pd2+ ions from its chloride solution compared to the commercial anion exchange membrane Neosepta® AM-01, with a full recovery of 100 mg/L Pd2+ ions in 30 min. This preliminary study shows that the prepared low-cost hybrid anion exchange membrane PIM can act as an inexpensive material suitable for the rapid and efficient recovery of Pd2+ ions from an aqueous solution.

CaCl2 is a low-toxic, inexpensive reagent that dissolves in large amounts in water to form highly concentrated aqueous solutions, or hydrate melts electrolyte. In this work, it was investigated that the concentrated CaCl2 aqueous solutions (aq) as novel lead (Pb) electrodeposition baths. While PbCl2 is poorly soluble in water at room temperature, PbCl2 dissolved up to 0.452 mol kg−1 ([Pb(II)] = 93.7 g kg−1) by the formation of PbCl42− complexes in the concentrated CaCl2 aq due to its high Cl− activity. Electrochemical measurements confirmed that the apparent exchange current density and the limiting current density of Pb electrodeposition decreased with increasing CaCl2 concentration. Since the diffusion of Pb(II) species was limited due to the high viscosity and ionic strength of the solution, agitation was effective in improving ion transport and electrodeposition rate. The presence of chloride ions in Pb electrolysis is usually detrimental due to the low solubility of PbCl2, however, the highly concentrated CaCl2 solution can be a potential candidate electrolyte for PbCl2-based electrolytic processes.

To study paste backfill corrosion mechanisms in chloride and sulfate environments, we studied the effect of chloride and sulfate on the strength of paste backfill after 7, 14, 28, and 40 days. The chloride solutions and sulfate solutions in concentrations are 0 g/L, 0.5 g/L, 1.5 g/L, 4.5 g/L, or 15 g/L. The obtained specimens were analyzed by performing uniaxial compressive strength tests, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that chloride and sulfate significantly increased the uniaxial compressive strength of the specimen at a very fast speed in the early stage of the test, and the original structure of the specimen was destroyed and its uniaxial compressive strength decreased with the gradual corrosion. The reason for this characteristic is because the chloride reacts with the paste backfill to form calcium chloroamine hydrate (Ca4Al2O6Cl2·10H2O), and the sulfate reacts with the paste backfill to form dihydrate gypsum (CaSO4·2H2O), mirabilite, and ettringite. In the early stage, these substances can fill the pores to improve the compressive strength, and then expand to damage the structure of the backfill and reduce its compressive strength. In addition, sulfate can enhance the decomposition of C-S-H, which results in a faster destruction of specimens than in chloride environments. [ABSTRACT FROM AUTHOR]

The article presents studies on the extraction of iron from chloride solutions with aliphatic alcohols, ketones, and their mixtures. Dilution of 1-octanol with an inert aromatic diluent to a concentration of 80 vol.% led to an increase in its extraction capacity, while the extraction capacity of 2-octanone has decreased with dilution. A synergistic effect was found for a 1-octanol/2-octanone mixture, the maximum of extraction was observed at a ketone concentration of 80 vol.%. The effect of a mixture composition and chloride ion concentration on the iron extraction degree was studied. McCabe-Thiele results indicated that at Fe(III) concentration in the aqueous phase 9.32 g∙dm−3, it is possible to extract iron(III) quantitatively using a mixture of alcohols C8+C10 (70 vol.%) and 2-undecanone (30 vol.%) after three extraction stages. Stripping of Fe(III) from the mixture was done with distilled water. After the stripping, the loaded Fe(III) concentration in the organic phase was reduced from 27 g∙dm−3 to <0.001 g∙dm−3 for 3 stages. The conditions were tested in continuous mode at a cascade of laboratory extractors. During the tests on the cascade, the low solubility of the mixture of ketone with alcohol was established, and the concentrated solution of ferric chloride was obtained. [ABSTRACT FROM AUTHOR]

On free surfaces without crevice structures, micro pits of several micrometers in diameter that are repassivated immediately are called metastable pits. The role of the micro pit as an initiation site of crevice corrosion was examined by comparing the metastable pitting corrosion potential (VCMS) of SUS304 stainless steel measured on the free surface with the critical potential for crevice corrosion (VCREV). VCREV presented the similar value to VAcMS. It was also revealed that micro pits, as well as SUS304 stainless steel surface, were hard to be repassivated at pH#8804;2.0, meaning that micro pits can be initiation sites of crevice corrosions. Investigating Cl- concentration and pH dependencies on each potential, the influences of these factors were also examined in terms of the contribution to a crevice corrosion initiation. Cl- ions, which have VCMS and VCREV less noble, will directly contribute to a crevice corrosion initiation by facilitating micro pit initiations. pH decrease accelerating passive dissolution would promote a crevice corrosion initiation indirectly by increasing Cl- migration into a crevice structure. [ABSTRACT FROM AUTHOR]

This work evaluated a corrosion inhibitor that consists of a mixture of a long chain silanol and cerium(III) salt, to protect carbon steel in 0.1 mol L–1 NaCl solution. The inhibitor solution was obtained after hydrolysis of the silane in the presence of the cerium salt. The silane concentration was kept constant at 400 ppm, while the cerium ions variated in 25, 50, and 100 ppm. The electrochemical measurements showed inhibition efficiency (% I.E.) above 96% for carbon steel in NaCl 0.1 mol L–1, in the best condition of the mixture of silanol and Ce (III) ions. The Raman spectroscopy confirmed the presence of inhibitors in the carbon steel surface even out of the solution containing the inhibitors as a persistent adsorbed film. Contact angle measurements showed the surface hydrophobicity imparted by the adsorbed corrosion inhibitor layer. SVET measurements confirmed that the corrosion inhibitors mixture can block both anodic and cathodic reactions. The studied inhibitors showed to be more efficient and/or cheaper than traditional corrosion inhibitors for neutral media.

The effect of a Cu addition on the corrosion behavior of 304 austenitic stainless steel in a solution was elaborately investigated through salt spray tests, FeCl3 immersion tests and characterization analyses. The corrosion behavior was further analyzed by optical microscopy, scanning electron microscopy, inductively coupled plasma mass spectrometry and an X-ray photoelectron spectroscopy analysis. 304Cu showed a higher corrosion resistance than 304 after the salt spray tests in a 5 wt.% NaCl solution for 168 h; the beneficial effect of Cu was not obvious after exposure for 480 h. Penetrating (stripped morphology in 304 and fishbone morphology in 304Cu) and non-penetrating dish-shaped pits were both observed on 304 and 304Cu after immersion in a 6 wt.% FeCl3 solution for 72 h; the corrosion rates of 304Cu were much higher than 304. Cu and Cu2+ were the main existing forms in the as-received 304Cu and Cu+ formed with the corrosion in chloride solutions. The results indicated a good corrosion resistance of 304Cu in service. The use of steel in an aggressive environment for a long exposure time should be cautiously considered.

Base metal hydrometallurgy in a chloride medium has considerable advantages, as metals can be recovered by solvent extraction through a neutral complex mechanism without extra reagent addition, leading to ready lixiviant recycling and significantly reduced wastewater discharge. However, the recovery of Ni(II) using this hydrometallurgical method is challenging because of the unavailability of appropriate extraction reagents. In this study, a new reagent, N-2-ethylhexylpyridine-3-formamide (MEH3), was used to efficiently extract Ni(II) from weakly acidic (pH > 2.5) or neutral chloride solutions in the form of neutral complexes without pH adjustment. Some other metal ions can also be extracted; the selectivity of the reagent for each metal decreased in the following order: Cu(II) > Zn(II) > Ni(II) > Fe(III) > Co(II) > Mn(II). The reagent had weak ability to extract other metal ions such as Ca, Al, Cr(III), Mg, and Li. The extraction of Ni(II) was positively correlated with the Cl− concentration in the aqueous solution, indicating that Cl− is a driving force for Ni(II) extraction. The Ni(II) loaded organic phase was stripped with water, and approximately 50 g/L of Ni(II) in the loaded strip liquor was obtained at an O/A ratio of 15:1. The Ni(II) extraction mechanism was further studied using crystal structure analysis, FT-IR spectroscopy, and the maximum loading capacity. The results showed that a Ni(MEH3) 2 Cl 2 complex was formed via Ni(II) extraction. In conclusion, the MEH3 system can selectively extract Ni(II) from a chloride solution without consuming alkaline reagents, and no new substances are produced, which is beneficial for the realization of mother liquor recycling and has a positive impact on clean hydrometallurgy. • The reagent N-2-ethylhexylpyridine-3-formamide was prepared as a new extractant for metal ions. • Ni(II) can be extracted by MEH3 in the form of neutral complexes in weakly acidic (pH > 2.5) chloride solutions. • A complex of Ni(MEH3) 2 Cl 2 was formed via Ni(II) extraction. [ABSTRACT FROM AUTHOR]

• Iodide-assisted chalcopyrite leaching in chloride media was studied. • Synergies between chloride, iodide, ferric iron, and cupric ions was evaluated. • At a temperature of 60° C almost 100% of copper extraction was extracted after 400 h of stirring. • The leached ore analysis showed as main species sulfur, in addition to intermediate copper sulfides of chalcocite/covellite. • Effects of solution potential, temperature, and particle size were also evaluated. Chalcopyrite leaching has slow kinetics in sulfate media compared to other copper minerals. Studies have shown that these slow kinetics are caused by a passivation layer generated during the mineral's dissolution and/or by its semiconductor properties. In the continuous search for regents to improve kinetics, the use of iodide in sulfate media has led to a significant improvement in the leaching rate of copper from chalcopyrite. However, no detailed information on the effect of the chloride concentration in this system has been informed so far. In this present work, the leaching of a chalcopyrite concentrate using iodide in chloride solution was evaluated, varying parameters such as temperature, particle size, the initial potential of the solution, chloride, iodide, and cupric ion concentrations. The results indicated a copper extraction of 75.8 % in 30 days in the presence of 50 g/L chloride, a 43.1 % more than in the absence of chloride (32.7 % extraction) obtained under the same conditions (100 mg/L I-, 0.5 g/L Cu2+, 9 g/L Fe3+, 1 g/L Fe2+, pH = 1.5, 35 °C and an initial potential solution of 700 mV vs SHE). Additionally, the most statistically significant factors on copper extraction in order of influence were temperature, iodide concentration, and chloride concentration. QEMSCAN-PMA analysis of the leached solids showed a significant amount of elemental sulfur and possible intermediate copper species of chalcocite and covellite, which are not observed for the leaching of chalcopyrite concentrate in the presence of iodide in sulfate media. The measurements of the chalcopyrite potential and the solution potential indicate that they are similar for high concentrations of Fe2+ and for iodide concentrations higher than 200 mg/L in the presence of Fe3+. The chalcopyrite potential obtained for the central condition of this study indicates that the predominant iodine species was triiodide, which suggests that this was the main oxidant in this system. [ABSTRACT FROM AUTHOR]

Considering the material balances of the constituents including solid phases, replacement reaction of the sphalerite‐galena pair in chloride solution is examined quantitatively under equilibrium conditions of 250°C, water saturation vapor pressure, and initial Cl concentration of 1 mol/L. NaCl+PbCl2 solution with solid sphalerite, dissolves and releases both total Zn and total S of 1.26 × 10−5 mol/L into the solution under without or lower PbCl2 concentration. If the PbCl2 concentration is higher than 1.32 × 10−6 mol/L, precipitation of galena as replacement occurs, suggesting that sphalerite has an ability to trap a lower concentration of Pb. If PbCl2 concentration of the solution is higher than 1.32 × 10−6 mol/L, the majority of Pb deposited as galena with using sulfur originated from solid sphalerite dissolved, and the amount of Zn from sphalerite equivalent to the amount of galena deposited releases into the solution. On the other hand, NaCl+ZnCl2 solution with solid galena under the same environmental conditions, dissolves and releases both total Pb and total S of 6.43 × 10−6 mol/L into the solution under without or lower ZnCl2 concentration. Over the ZnCl2 concentration of 6.40 × 10−5 mol/L in the solution, precipitation of sphalerite occurs, indicating that galena cannot trap a low concentration of Zn. Zinc would drain away from the hydrothermal depositional environment under the presence of only galena. These relationships are controlled mainly by the reaction of predominant metal chloride or metal hydroxide species in the solution. Sphalerite is a good scavenger for Pb, but galena is not for Zn. [ABSTRACT FROM AUTHOR]

It is shown that xanthan gum inhibits corrosion processes in carbon steel placed in chloride-containing media by the mechanism of adsorption. Potassium-sodium tartrate improves the protective efficiency of xanthan gum. The results of electrochemical impedance spectroscopy confirm the formation of protective barrier layer on steel in a medium inhibited by the composition of gum with tartrate. The Langmuir adsorption isotherm corresponds to the most studied inhibitory system. The degree of protection of carbon steel by the inhibitory composition based on gum and tartrate exceeds 90%. The elevation of corrosion resistance of the metal in the medium inhibited by this composition is confirmed by the results of optical microscopy. [ABSTRACT FROM AUTHOR]

Chloride is one of the effective medium in which platinum group metals (PGMs) can be brought into a solution, thus chlorocomplexes are particularly important in the process chemistry of PGMs separations. Rh (III) chlorocomplexes are poorly extracted into organic solvents, which is due to the charge of the complex as well as those inert character in a solution, that is, formation of RhCl6-n(H2O)n(3-n) - (n=1-6) . The problem of solvent extraction of Rh from chloride solutions has not yet been solved and there is no effective industrial extractant for Rh. PGMs are traditionally separated from one another and the other metals by a complex series of selective precipitation techniques. These are generally inefficient in terms of the degree of separation achieved. Solvent extraction applied to refining process for PGMs offers several advantages over the traditional precipitation methods. Adding Sn (II) to a Rh (III) feed is a good procedure which can be used to make Rh react more easily to extraction, however, stripping of Rh from the loaded organic pahse is very difficult. In the present study, the extraction of Rh from hydrochloric acid solutions with tri-n-octylamine (TOA) and tri-octyl methyl ammonium chloride (TOMAC) were tested to clarify the effect of addition of Sn (II) on the extraction of Rh and stripping of Rh.

In the present work, the corrosion protection of aluminum alloy AA2024‐T3 has been studied in NaCl solution, with and without the addition of cerium (III) chloride heptahydrate. The corrosion inhibitor efficiency after immersion into 10 mM NaCl, with or without 3 mM of CeCl3·7H2O at 20°C, 40°C, and 60°C was investigated. The performed quantitative tests include electrochemical techniques, such as the method of quasipotentiostatic polarization (Tafel extrapolation), cyclic polarization, and electrochemical impedance spectroscopy to determine corrosion rate (vcorr), inhibition efficiency (η %), protective ability (γ), degree of coverage (ϑ), and pitting nucleation resistance. The samples were analyzed with scanning electron microscopy and energy dispersive X‐ray analysis to evaluate and characterize the precipitates formed on the surface of aluminum samples and to determine dominant type of corrosion. The formation of Ce3+ precipitates occurred on cathodic intermetallic sites and the surface, in general, resulting in improved corrosion resistance. Tested cerium (III) chloride heptahydrate proved to be an effective inorganic corrosion inhibitor for AA2024‐T3 in chloride solution, which, by the action of cerium ions, reduced corrosion on the surface of the studied aluminum alloy. [ABSTRACT FROM AUTHOR]

In this review we summarize the research work reported in the last two decades on the use of organic corrosion inhibitors for aluminum and its alloys in different alkaline (mainly NaOH and KOH) and chloride solutions. The focus is on the corrosion inhibitor type and its inhibition effectiveness and mechanism. Moreover, the testing conditions and the methodology used for corrosion inhibition performance evaluation are presented. As seen herein, the most frequently used corrosion inhibitors are the mercapto compounds, azole derivatives, organic dyes, and different polymers. Weight loss and electrochemical techniques were among the most frequently used techniques to evaluate the corrosion inhibition effectiveness of the studied compounds. [ABSTRACT FROM AUTHOR]

This study investigates the corrosion behavior of AlSi10Mg alloy produced by additive manufacturing and gravity casting before and after T6 heat treatment. Electrochemical tests showed that the additive manufactured material in as‐produced condition exhibits high corrosion resistance, due to the very fine microstructure, while immersion test allowed to identify an exfoliation‐like corrosion phenomenon, which caused a significant mass loss. In this case, T6 heat treatment was beneficial for corrosion resistance since the related change in microstructure led to a less detrimental corrosion mechanism. Therefore, the T6 heat treatment resulted necessary to use additive manufactured AlSi10Mg components in aggressive chloride‐bearing environments. [ABSTRACT FROM AUTHOR]

The solvent extraction ability of 1,1′-dialkyl-2,2′-bibenzimidazoles (L) for the recovery of copper(II) ions from aqueous chloride solutions has been investigated. It was found that 1,1′-didecyl- 2,2′-bibenzimidazole is a useful extractant for the separation of copper(II) ions from both weakly and strongly acidic solutions. Copper(II) can be effectively stripped of organic solutions by a water or ammonia solution in a one-stage process. In low acidity media (pHfeed > 1), the extraction percentage of Cu(II) increases with an increase in metal ions and chloride concentrations. Copper(II) ions are extracted as binuclear complexes (CuCl2)2L2 (L = extractant). The constructed McCabe−Thiele diagram shows that the reduction of copper(II) ions concentration from 25 to approximately 5 g/dm³ in an aqueous feed is possible in two extraction stages. When [HCl]feed ≥ 1 M, (LH+)2(CuCl42-)L complex is formed. From the strongly acidic solutions ([HCl] = [LiCl] = 4 M), almost 100% of copper(II) ions can be removed by 1,1′-didecyl-2,2′-bibenzimidazole. Benzyl alcohol, used as an organic phase modifier, enables the selective extraction of copper(II) over zinc(II) ions from a weakly acidic chloride solution. [ABSTRACT FROM AUTHOR]

Research into the solvent extraction of iron(III) from a chloride solution after bauxite HCl leaching by neutral oxygen-containing extractants and their mixtures were studied and the iron(III) extraction degree from chloride solutions using alcohols is presented. The effect of dilution of alcohol with a ketone by an extraction mixture in relation to its effectiveness was investigated. The iron(III) was efficiently extracted by the mixture of 1-octanol and 1-decanol (70%) with 2-undecanone (30%) from hydrochloric bauxite leach liquor at an O:A ratio = 2-4:1 at an iron(III) concentration of 7.4 g/L and 6 M HCl. For the removal of iron-containing organic phase from impurities (Al, Ca, Cr) that are co-extracted with iron(III), we used two step scrubbing at O:A = 5:1 by 7 M HCl as a scrub solution. The iron(III) stripping at the O:A ratio is shown. Using counter-current cascade of extractors, it was possible to obtain an FeCl3 solution with the iron(III) content of 90.5 g/L and total impurities less than 50 mg/L.

In the present study, the copper anode slime was leached in chloride media. Then, pregnant leach solution (PLS) was purified using solvent extraction method and Octanol-kerosene solution. HAuCl4.2L was determined as the extracted macromolecule, and separation of impurities, such as copper, iron and selenium was done in the presence of gold. McCabe-Thiele diagram of Au–HCl (3 M)– Octanol (40% v/v) in O/A=3/4 showed that Au concentration in aqueous phase decreased from the initial value of 200 to 7 mg/L, after 5 stages. Ammonia solution was proposed as the stripper and McCabe-Thiele diagram was presented to obtain the number of gold stripping steps by ammonia solution

In this paper, adsorption of gold from chloride media using commercial sorbent (Lewatit TP 214 (L-214)) and biomass residue (rice hull (RH)) were investigated. The different adsorption parameters, sorbent dosage, contact time, temperature and pH of solution on adsorption (%) were studied in detail on a batch sorption. Before the RH was activated, adsorption (%) was poor compared with L-214. However, after the RH was activated at 1000 °C under an argon atmosphere, the gold adsorption (%) increased four-fold. X-ray fluorescence (XRF) was used to explore the feasibility this material as an adsorbent for the removal of gold from aqueous solutions. The adsorption equilibrium data were best fitted with the Langmuir isotherm model. The maximum adsorption capacities, Qmax, at 25 °C were found to be 93.46 and 108.70 mg/g for the activated rice hull (ARH) and L-214, respectively. Thermodynamic calculations using ΔH°, ΔS°, ΔG° and Ea values indicate that the adsorption process was spontaneous and endothermic.

Abstract Four new 1,1′-dialkyl-2,2′-bibenzimidazoles were used to extract zinc(II) from acid chloride solutions at various concentrations of chloride and hydrogen ions. In low acidity media (pH > 2), the maximum zinc(II) extraction with the compounds is observed at chloride concentrations in the range 0.7–1.8 M. Zinc(II) ions are extracted as neutral (ZnCl 2) m L n complexes (L = extractant) in which the m:n ratio varies from 1:2 to 3:3, depending on the metal-to-extractant molar ratio in the extraction media. In strongly acidic systems, anionic zinc(II) chloro-complexes may be extracted from aqueous solutions by protonated bibenzimidazoles as (LH+) 2 (ZnCl 4 2−) or/and (LH+)(ZnCl 3 −) ion pairs. In weakly acidic media, at [Cl−] < 2 M, Zn(II) can be separated from Cd(II), Cu(II), and Ni(II) by 1,1′-didecyl-2,2′-bibenzimidazole, the best extractant from the tested dialkyl derivatives of 2,2′-bibenzimidazole. From the feed containing 26 g/L Zn(II), over 80% of zinc(II) ions is selectively separated after four extraction stages. 1,1′-Didecyl-2,2′-bibenzimidazole can be used for the selective separation of pure Fe(III) and Zn(II) from acidic chloride solutions. At a high chloride concentration (6 M) and at 0.5–0.8 M HCl in the aqueous feed, Fe(III) is efficiently transferred into the organic phase in the presence of Zn(II) and is then easily stripped off with water. Zn(II) can be completely removed from the iron-free raffinate after this aqueous solution is acidified to 1.5 M HCl. Highlights • 1,1′-Dialkyl-2,2′-bibenzimidazoles extract zinc(II) from acid chloride solutions. • Zn(II) extraction depends upon the acid, chloride, salt, and metal concentration. • In weakly acidic media, Zn(II) can be separated from Cd(II), Cu(II), and Ni(II). • Fe(III) and Zn(II) can be selectively extracted from acid chloride solutions. [ABSTRACT FROM AUTHOR]

Galvanic corrosion behaviour of copper and copper alloys in chloride solution (0.6 M NaCl) under different temperature conditions (35°C, 55°C and 80°C) was investigated by the wire beam electrode (WBE) method. It was found that the average galvanic current of the Cu and Cu-Sn alloy, which shifted from the cathode at 35°C to the anode at 80°C, increased as temperature increased during the immersion time. In contrast, the average galvanic current of Cu-Zn alloy can be ranked as 35°C > 55°C > 80°C. A sudden conversion was that the anode average current of Cu-Zn alloy at 35, 55°C changed into the cathode when the immersion time lasted untill 3 h at 80°C. The results indicate that it is feasible to study the corrosion behaviour under the different temperature environment with the WBE method. [ABSTRACT FROM AUTHOR]

Copyright of Hydrometallurgy of China is the property of Hydrometallurgy of China Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The extraction of zinc in the presence of manganese and cadmium from chloride solution with di 2 ethyl hexyl phosphoric acid (D2EHPA) in kerosene diluent were comprehensively investigated. The extraction experiments were carried out in order to determine the influential parameters in the conditions of A:O ratio of 1:1, pH range of 1–6, temperatures of 30 °C, 40 °C and 50 °C in an aqueous solution with concentrations of 5 g/L of zinc, manganese and cadmium. The variety of influential parameters in the process such as equilibrium pH, concentration of D2EHPA, temperature, contact time, initial concentration of ions and also thermodynamic parameters of zinc extraction in chloride solution were precisely evaluated. The results showed that in the optimal condition of pH = 2.5–3, temperature 40 °C and [D2EHPA] = 10 v/v, the extraction of Zn, Mn and Cd were 97%, 14% and 3% respectively. ΔpH 0.5 Zn-Mn and ΔpH 0.5 Zn-Cd in this condition respectively equal to 2.5 and more than 5.25. Also, the study indicated that the predominant zinc species extracted by D2EHPA was ZnCl + . Based on thermodynamic studies, the values of ΔH o , ΔS o and ΔG o for zinc extraction in condition of temperature 40 °C and [D2EHPA] = 10 v/v are 25.65 kJ.mol −1 , 79.20 J·K −1 ·mol −1 and 0.86 kJ·mol −1 respectively. Furthermore, the results showed that under constant concentration of D2EHPA, changes in the initial concentrations of Zn, Mn and Cd in the chloride solution were most effective in their separation. [ABSTRACT FROM AUTHOR]

Selection of a proper inhibitor should be based on the evaluation of its mechanism and effective concentrations. Mechanism of inhibition usually has dynamic character due to changing physicochemical conditions of the environment and corroding metal surface. Most of actually used methods are stationary or contain assumptions which highly influences obtained values. Development of new dynamic method, based on modified EIS, allows excitation of the system by signal composed of galvanodynamic perturbation and AC signal as a set of 20 sinusoids. Such an approach allowed comparison of the obtained results by two simultaneous methods and verification of the selected electric equivalent circuit. Instant value of charge transfer resistance of mild steel exposed to industrial water with changing concentration of 8-Hydroxyquinoline in the system was determined. [ABSTRACT FROM PUBLISHER]

We used chemical analysis method for ordinary concrete (OPC), high strength concrete (HSC), high performance concrete (HPC), steel fiber reinforced high performance concrete (SFRHPC), high strength high elastic modulus polyethylene fiber reinforced high performance concrete (PFRHPC), which are immersed in Qinghai salt lake for 1 425 d, and quantitatively analyzed the chloride ion content. The results show that the structure of ordinary concrete is loose, the chloride ion is easy to enter, and the content of chloride ion is high, the structure of high strength and high performance concrete is dense, the chloride ion is not easy to enter, and the content of chloride ion is low. High strength and high performance concrete have better resistance to chloride ion erosion. [ABSTRACT FROM AUTHOR]

Chloride salts can prevent roads from freezing in cold regions, together with severe corrosion on steel constructions. To develop an ecological and low-corrosive antifreeze, di-sodium hydrogenphosphate (Na2HPO4) was chosen as the additive into chloride salts. The addition of Na2HPO4 into either of the antifreezes of natural salt (N/S), NaCl, CaCl2 or MgCl2 can suppress the corrosion reaction of mild steel in the 3.0% antifreeze solution. Moreover, the addition of CaCl2 or MgCl2 into the antifreeze containing NaCl and 2.0% Na2HPO4 significantly decreased the corrosion rate. According to polarisation and XPS analyses, it is evident that the obtained low corrosion rates on mild steel are related to the suppressed cathodic and anodic reactions and the formation of a protective film containing Fe, P, O, Ca or Mg. This paper is part of a supplementary issue from the 17th Asia-Pacific Corrosion Control Conference (APCCC-17). [ABSTRACT FROM AUTHOR]

The corrosion and kinetics of partial electrode reactions on St3 carbon steel with a superhydrophobic coating based on methoxy fluorobutylsilane derivatives in 0.5 M NaCl solution were studied. This influence of in situ duration τ of the medium's corrosive action (0.5-144 h) on its protective effect is considered. This allows reduction of overall corrosion rate by 23 ± 3 times, when the stationary state is reached. The kinetics of cathodic reduction of dissolved oxygen and steel anodic ionization is also considered. In the initial stages of corrosive action of neutral aerated chloride medium (until steady-state characteristics are reached), steel at potential E near Ecor corrodes in the active state, whereas, when τ is ≤0.5 h, it corrodes under anodic control conditions, and then the control is replaced with a cathodic one. [ABSTRACT FROM AUTHOR]

Novel extractants, hydrophobic N ′-alkyloxypyridine-2-, -3- and -4-carboximidamides, were proposed as the efficient zinc(II) extractants from acidic chloride solutions. In this study various factors affecting zinc(II) extraction, such as concentration of chloride ions, mineral acid and zinc in the aqueous feed solution, structure and concentration of the extractant and type of the organic diluent were studied. It was found that the extraction of Zn(II) was observed for the pyridine-3- and 4-carboximidamides with 2-ethylhexyl group and the extraction abilities increased with the increase of chloride ions concentration. N ′-(2-ethylhexyloxy)pyridine-4-carboximidamide appeared to be the most efficient extractant, as well as, it was the most suitable in terms of loading capacity. It was also found that 4-EH enabled a complete transfer of Zn(II) from the concentrated aqueous solution by using a two-stage counter-current extraction at an O/A ratio of 7.5 or at O/A = 8 by using a one-stage cross-flow extraction. [ABSTRACT FROM AUTHOR]

The leaching behavior of copper sulfides in concentrated cupric chloride solution at 95 °C and at ambient pressure was studied in order to scrutinize the leaching behavior of a single bornite and four different chalcopyrite concentrates obtained from various mines around the world. The highest chalcopyrite oxidation was achieved with the highest pyrite content in the concentrate, suggesting galvanic effect on chalcopyrite dissolution. It was found that iron and copper from chalcopyrite did not dissolve into the solution in an equal ratio, as expected. A significant amount of copper precipitated at pH ≤ 1.4. This study showed that chalcopyrite chloride leaching, in the absence of oxygen purging, leads to covellite precipitation. The mineralogical studies on a leach residue established that the precipitated copper was a secondary covellite (CuS). Leaching of bornite rich concentrate did not increase acidity and no equally strong copper precipitation was observed at pH = 2.1. [ABSTRACT FROM AUTHOR]

Present paper reports the systematic scientific studies for extraction of lanthanum (La) and neodymium (Nd) from chloride solution containing rare earth metals (REMs). The chloride leach liquor was generated by dissolving rare earth mineral and found to contain 0.53 g/L La and 1.01 g/L Nd along with other REMs. Initial extraction studies were carried out from a model solution containing La and Nd using 10% Cyanex 272 diluted in kerosene along with 2% isodecanol (ID) as phase modifier. Various process parameters viz. effect of pH, time, O/A ratio, loading capacity, etc. were optimized for maximum extraction. More than 97% La and Nd were extracted at an equilibrium pH of 3.3 and 2.7, respectively at phase ratio (O/A) 1:1 and mixing time of 5 min in two stages. 10% HCl was used to strip La as well as Nd from the loaded extractant. Moreover, 99.99% separation of La and Nd could also be achieved by stripping the loaded organic phase with pure Nd scrub solution. The optimum condition for extraction was validated with the actual solution. The result revealed that 99.49% La and 95.04% Nd can be extracted in 5 min at an equilibrium pH of 3.3 and 2.7, respectively at phase ratio 1:1. [ABSTRACT FROM AUTHOR]

The recovery of platinum group metals (PGMs) from chloride solution using magnetite was investigated. The adsorption of platinum, palladium, and rhodium in chloride medium onto synthetic magnetite powders were studied at different pH conditions, contact time, sodium chloride concentrations, and initial Pt, Rh, and Pd concentrations. Platinum and palladium uptake by magnetite was at a maximum at pH 6–7, and pH 3–4 for rhodium after 24 h with 0.1 mol/dm3sodium chloride at an initial PGM concentration of 0.05 mol/m3. A sorption mechanism for PGMs was discussed based on the results. [ABSTRACT FROM AUTHOR]

The effects of chloride concentration, creviced scaling factor and immersion time on the percentage area and maximum depth of attack for Type 304 stainless steel (SS304) in chloride solutions were investigated. The crevice assembly comprised of coupon (SS-304), polytetrafluoroethylene (crevice former) and fasteners (titanium bolt, nut and washers). The full immersion tests were based on ASTM G-78 using full factorial design to study the effects of chloride concentration (1.5, 3.0 and 4.5 w/w%), crevice scaling factor (8, 16 and 24) and immersion time (15, 30 and 45 days) on the percentage area of attack (Y1) and maximum depth of attack (Y2) of SS-304. Data obtained was used to develop and optimize the models of Y1 and Y2 in terms of the three factors using Response Surface Methodology (RSM). The R2 of Y1 and Y2 were 0.98 and 0.91, respectively. The minimum Y1 (5.63%) and Y2 (3.32×10−7 mm) were obtained at 4.5% chloride concentration, 20 scaling factor and 15 days immersion time. The predicted optimal conditions agreed with the experimental results for validation with a maximum absolute relative error of 5.75%. [ABSTRACT FROM AUTHOR]

The corrosion behavior of carbon steel in chloride aqueous solutions at a low dose rate was investigated by corrosion testing using chloride aqueous solutions with different chloride concentrations at a dose rate of 500 Gy/h. The corrosion rate of carbon steel increased with the irradiation, and the corrosion rate had a maximum value at a certain concentration. The oxidants produced by radiolysis of chloride aqueous solution enhanced the corrosion of carbon steel. The main oxidants were oxygen and hydrogen peroxide, and the diffusion process of oxidants controlled the corrosion of carbon steel under the gamma-ray irradiation. There was a positive correlation between the dependence of the corrosion rate and chloride concentration and the dependence of the oxidant and chloride concentrations. [ABSTRACT FROM AUTHOR]

The inhibition effect of dimethylethanolamine (DMEA) and its composite with carboxylic acid was studied with the electrochemical tests. The experimental results indicate that DMEA is not a good inhibitor but the composite of DMEA with caprylic acid exhibits excellent inhibiting efficiency. The synergic mechanism of the organic corrosion inhibitors (OCIs) was studied with quantum chemical calculations. It is found that the DMEA forms a quaternary ammonium salt with the proton in carboxylic acid, and a cyclic complex formed between the salt and Fe may be responsible for the enhancement of inhibiting efficiency. The possible hydrogen bond formed between DMEA and carboxylic acid is not enough for the inhibiting effect. This work is helpful to proposing theoretical interpretation as well as developing a functional organic inhibitor to improve the durability of reinforced concrete contaminated with chloride. [ABSTRACT FROM AUTHOR]