•Peracetic acid (PAA): •OH and R-O• generated by electron gain at the cathode.•Synergistic reaction of PAA with electrogenerated HClO: boosted 1O2 production.•Fast degradation (10 min) of ...sulfamethoxazole in actual wastewater at pH 6.9.•Clear minimization of chlorinated DBPs accumulation in actual Cl−-rich wastewater.•A scenario-oriented paradigm for PAA−based electrochemical treatment is provided.
Electrochemical advanced oxidation processes (EAOPs) face challenging conditions in chloride media, owing to the co-generation of undesirable Cl−disinfection byproducts (Cl−DBPs). Herein, the synergistic activation between in-situ electrogenerated HClO and peracetic acid (PAA)-based reactive species in actual wastewater is discussed. A metal-free graphene−modified graphite felt (graphene/GF) cathode is used for the first time to achieve the electrochemically-mediated activation of PAA. The PAA/Cl− system allowed a near−complete sulfamethoxazole (SMX) degradation (kobs =0.49 min−1) in only 5 min in a model solution, inducing 32.7− and 8.2−fold rise in kobs as compared to single PAA and Cl− systems, respectively. Such enhancement is attributed to the occurrence of 1O2 (25.5 μmol L−1 after 5 min of electrolysis) from the thermodynamically favored reaction between HClO and PAA-based reactive species. The antibiotic degradation in a complex water matrix was further considered. The SMX removal is slightly susceptible to the coexisting natural organic matter, with both the acute cytotoxicity (ACT) and the yield of 12 DBPs decreasing by 29.4 % and 37.3 %, respectively. According to calculations, HClO accumulation and organic Cl−addition reactions are thermodynamically unfavored. This study provides a scenario-oriented paradigm for PAA−based electrochemical treatment technology, being particularly appealing for treating wastewater rich in Cl− ion, which may derive in toxic Cl−DBPs.
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It is essential to develop solvent extraction (SX), and electrodeposition (ED) processes for palladium to reduce the volume of acid and organic media. In this study, the extraction reaction of Pd(II) ...in chloride media using of N, N, N', N', N", N"-hexaoctyl-nitrilotriacetamide (NTAamide(C8)) as a novel extractant has been demonstrated. Three diluents with high dielectric constants (acetophenone (AP), 1,2-dichloroethane (DCE), and 1-octanol (OC)) were used for the solvent extraction reaction. The slope analysis indicated that the anion exchange extraction reaction of Pd(II) was consistent with an approximately 2:1 stoichiometry for the NTAamide(C8)/AP and NTAamide(C8)/DCE systems, and 1:1 for NTAamide(C8)/OC. Moreover, the ED behavior of the extracted Pd(II) complex was investigated using cyclic voltammetry (CV). Palladium reduction was found to be an irreversible process based on analysis of the standard rate constant. A semi-integral analysis of the voltammogram determined the diffusion coefficients of the extracted Pd(II) complex in the AP, DCE, and OC systems to be 3.7 ± 0.1 × 10
−10
, 2.8 ± 0.1 × 10
−10
and 1.5 ± 0.2 × 10
−10
m
2
s
−1
, respectively. Furthermore, consecutive extraction-electrodeposition processes using the NTAamide(C8)/AP system were carried out for five cycles. High extraction percentage (E > 91%) and current efficiency (ε > 83.1%) were attained in all cycles. The electrodeposits recovered from the extraction-electrodeposition process were identified as Pd metal through X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses.
•Multimodal assessment of the leaching variability at the micro- and macroscale.•Tracking of hundreds of thousands of grains over time.•Able to couple porosity network development and microcrack ...formation to leaching variability.•Leaching in chloride media is more selective for copper sulphides, evidencing virtually no pyrite dissolution.
Understanding the variability of leaching kinetics is extremely challenging due to the nature of leaching processes. Common experimental setups, such as column leaching experiments, only allow for quantification of apparent leach kinetics at the macroscale (e.g. at the particle or column level), failing to capture grain-scale variability. In this paper, we study variability in leaching kinetics at the micro- and macroscale using a combination of 4D imaging and standard chemical measurements.
The impact of chloride ions on leaching performance was evaluated using column leaching experiments. Micro-computed tomography (micro-CT) was combined with SEM/EDX to isolate chalcopyrite from pyrite dissolution. Using in-house algorithms, the leaching behaviour of hundreds of thousands of grains was quantified and tracked over time. Morphological changes at the agglomerate level were assessed, coupling porosity network development and microcrack formation to leaching variability.
It was concluded that a decrease in internal macro porosity does not significantly impact macro-scale leaching performance. Grain size had an impact, although grain location does not influence mass transport resistance. Another key finding was that leaching in chloride media is more selective for copper sulphides, evidencing virtually no pyrite dissolution. This study not only provides new understanding of the factors influencing the leach behaviour of chalcopyrite ore, but also generates data that represents the process more accurately and allows for better planning.
An experimental investigation was carried out to improve the zinc dissolution rate in the direct atmospheric leaching of marmatite by adding sodium chloride to the sulfuric acid-ferric sulfate‑oxygen ...media. The experiments were carried out by using mono-sized marmatite particles varying the concentrations of sulfuric acid from 0.1 to 1.3 M, ferric sulfate from 0 to 0.8 M, sodium chloride from 0 to 1.3 M, and temperature in the range of 60 to 95 °C. The results showed that the addition of 0.7 M of sodium chloride improved drastically the direct leaching kinetics of the zinc sulfide; therefore, this leaching media is an excellent alternative to produce zinc from marmatite concentrates at ambient pressure. The sulfuric acid concentration was also found to have a significant effect on the rate of dissolution, indicating that the non-oxidative dissolution of marmatite plays an important role in the reaction mechanism in this system. A shrinking core model with diffusion through a product layer control was found to fit the reaction rate. An apparent activation energy value of 81.8 kJ/mol was found for the temperature range of 60–95 °C. The direct atmospheric leaching of marmatite in H2SO4-Fe(SO4)1.5-NaCl-O2 is an excellent alternative method to extract zinc due to high dissolution rates obtained in the presence of chloride ions, reducing substantially the treatment times.
•Direct atmospheric marmatite leaching in ferric sulfate‑sulfuric acid‑sodium chloride ‑oxygen.•Chloride ions improve drastically the leaching kinetics of marmatite.•Ferric ion in solution is the main oxidant of marmatite.•A shrinking core model with diffusion through a product layer fits the reaction rate.
In this study, the Ni nanoparticles grafted TiO2 nanotubes electrode improved by surface reconstruction (s-Ni/TiO2/Ti) shows the facile hydrogen evolution reaction (HER) in the alkaline and chloride ...solutions. Nickel nanoparticles were electrochemically grafted on the anodic TiO2 nanotubes under different conditions. The heat treatment of TiO2 nanotubes contributes to the enhancement of electrical conductivity and template adherence. The surface reconstruction is indicated to create heterojunction intermediates, Ni(OH)2 and NiOOH, on the surface of Ni nanoparticles. An extremely low overpotential of 126 mV is required for HER on the s-Ni/TiO2/Ti electrode in 1.0 M KOH solution, showing higher activity than Pt/C. Besides, the developed electrode exhibits an overpotential of 127 mV for HER in 1.0 M KOH + 0.5 M NaCl solution. The long-term stability over 100 h suggests a highly active and inexpensive material choice for substituting the precious electrocatalysts in corrosive media such as seawater.
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•Surface reconstruction develops reactive intermediates on the electrode surface.•The s-Ni/TiO2/Ti reaches low overpotential in alkaline and chloride solutions.•The enhanced performance is due to the presence of heterojunction interfaces.•The long-term stability suggests that s-Ni/TiO2/Ti is a promising candidate.
The synergistic extraction of rare earths (REs) from chloride media by a mixture of two extractants 2-ethylhexylaminomethyl phosphonic acid mono-2-ethylhexyl ester (HEHAMP, HA) and sec-octylphenoxy ...acetic acid (CA12, HB) was investigated. A remarkable positive synergistic effect was observed at the molar ratio of HEHAMP to CA12 being of 2:3. The extraction of REs was found to be a cation exchange process and the extracted species of Yb3+ was determined as YbCl2HAB. The separation factors (SF) of adjacent heavy REs, i.e. SFYb/Tm and SFLu/Yb, for the mixtures were 2.50 and 1.63, which were much higher than those of the sole HEHAMP and the sole CA12 system. In additional, the values of SFYb/Y and SFLu/Y were 7.17 and 11.14, respectively, which were higher than those of other reported synergistic systems and those of the sole HEHAEP or CA12 system, suggesting that the mixture of HEHAMP and CA12 is a potential synergistic extraction system for the separation of heavy REs and/or Y(III) from other heavy REs. A cascade extraction process for the separation of Y(III) from yttrium-enriched REs feed using the synergistic extraction system was developed, which are superior to sole CA12 system. The Y2O3 product with a purity of 99.4% was obtained by 8 extraction stages and 5 scrubbing stages.
•The mixtures of HEHAMP and CA12 exhibit a remarkable synergistic effect toward the extraction of rare earths.•Maximum synergistic effect was obtained with the HEHAMP and CA12 molar ratio being 2:3.•The separation performance for heavy REs and Y was better than that of the sole HEHAMP systems.•The synergistic complex was determined to be YbCl2HAB.
It is well known that the leaching of chalcopyrite has very slow kinetics. The generally higher reactivity of chalcopyrite in chloride as opposed to sulfate solutions has resulted in many studies of ...chloride systems for the hydrometallurgical treatment of chalcopyrite. Despite much progress on the chloride leaching process, agglomeration and curing has received less attention over the past years. This paper reports a study on the effect of addition of chloride ion in the agglomeration and the effect of curing time on the overall leaching process of chalcopyrite ore. The work involved leaching tests carried out in columns containing 3.0 kg of agglomerated ore irrigated with raffinate solution under ambient conditions. Experiments with agglomerates produced at different concentration of chloride (20, 50 and 70 kg/t) leach at approximately the same rate. It has been demonstrated that chloride ions presence is necessary to improve the leaching kinetics, but high concentrations of chloride are not essential under ambient conditions. The rate of dissolution of chalcopyrite ore agglomerated with high concentrations of acid and chloride ions increases as the curing period increases from 15 to 80 days observing extraction of copper up to 60% in 20 days of leaching. In all experiments, the shape of the leach curves indicate that the copper that has been solubilized during the curing period is rapidly leached followed by continuous slow leaching thereafter. This study supports the addition of chloride at the agglomeration stage as a viable route for the treatment of low-grade copper sulfide ore.
•Ore agglomerated in extreme condition with high concentrations of acid and chloride increases the dissolution of chalcopyrite.
Phosphonium ionic liquid: trihexyl(tetradecyl)phosphonium chloride (Cyphos
®IL 101) has been used as a novel reagent in the presence of toluene to extract palladium(II) from hydrochloric acid ...solutions of various concentrations. Extraction data indicate that Cyphos
®IL 101 is a very efficient and fast extractant. The increase in HCl concentration has negative influence on the extraction and about 97 and 54% of palladium(II) can be effectively extracted with Cyphos
®IL 101 from 0.1 and 3
M HCl, respectively. The equilibrium of palladium(II) extraction from aqueous 0.1 and 3
M HCl with this phosphonium ionic liquid is achieved after 5
min. Successful stripping of palladium(II) from the loaded organic phase is achieved with 0.5
M ammonia solution. Cyphos
®IL 101 can be reused at least in 5 cycles of extraction-stripping process.
Citrus paradisi and Cymbopogon distillates were admixed in ratio 1:1 and assessed for their inhibition effect on Cu-Ni cupronickel alloy in 0.25 M H2SO4–3.5% NaCl electrolyte. Results revealed the ...distillates effectively inhibited the Cu-Ni alloy at 2–5% CPC concentrations. The degradation rate of Cu-Ni alloy without distillate is 0.373 mm/y whereas at 1% concentration, the degradation rate decreased to 0.140 mm/y (1.37 × 10−5 A/cm2) corresponding to inhibition efficiency of 62.46%. At 2–5% concentration, inhibition efficiency ranged between 80.47 and 95.58%. The distillate displayed mixed-type inhibition performance coupled with significant suppression of cathodic reduction reactions. Thermodynamic calculations showed the distillates adsorbed unto the Cu-Ni alloy by chemisorption according to Langmuir and Freundlich adsorption isotherms (correlation coefficients above 0.8). Gibbs free energy indicate increase lateral attraction effect among the distillate molecules with respect to #concentration. Open circuit potential curves showed the distillates increased the thermodynamic instability of Cu despite effective inhibition performance.
