Stripping Step Research Articles

Application of Double Deposition and Stripping Steps System for Minimization of Interferences of Peaks’ Overlapping in Anodic Stripping Voltammetry

AbstractAn anodic stripping voltammetric procedure for the determination of bismuth in the presence of excess of Cu2+ ions at two ex situ plated gold film electrodes was described. The procedure is based on utilization of two deposition and two stripping steps system. The presented procedure ensures increasing the sensitivity of Bi3+ determination and minimization of interferences related to peaks’ overlapping. The calibration graph for bismuth determination was linear from 2.5×10−9 to 2×10−8 mol L−1 for deposition time of 300 s at both working electrodes while detection limit was 7.7×10−10 mol L−1.

Study on the Determination Method of Cast Blasting Stockpile Forms in an Open-Pit Mine

Cast blasting–dragline stripping technology is the most advanced mining technology used in open-pit mines. For a long time, however, its precision has been hindered. In this paper, we aim to improve the precision of cast blasting–dragline stripping technology and promote its intelligent design. We present a method to determine cast blasting stockpile forms. First, the 3D point cloud data for the Heidaigou open-pit mine from recent years were collected and counted, and a 3D mathematical model of overcasting stripping steps was constructed. Then, data classification and multivariate statistical analysis were used to establish a cast blasting stockpile characteristic parameter database. Next, locally weighted linear regression was used as the fitting method to achieve shape fitting under different cast blasting step heights. Finally, interval estimation was used as the fitting result test method to verify the morphology of the acquired cast blasting stockpile form. The research results show that the cast blasting stockpile form obtained by fitting can truly reflect the cast blasting effect of the Heidaigou open-pit mine and ensure the reliability and accuracy of the subsequent design of cast blasting–dragline stripping technology.

An Efficient Method for Brain Image Preprocessing with Anisotropic Diffusion Filter & Tumor Segmentation

The brain is central controlling system in human body. The internal structure and functioning of brain change due to any kind of enlargement of the brain cells which is diagnosed as a brain tumor. Early detection of tumor is critical for better treatment options. In this paper, brain magnetic resonance (MR) image is preprocessed and watershed algorithm is applied to separate the image objects and to segment the tumor. Image preprocessing includes anisotropic diffusion filter (ADF), skull stripping and contrast enhancement steps. ADF eliminates noise content from MR images and preserves the edges of existing objects, followed by skull stripping to remove the nonbrain tissues and contrast enhancement to improve visual quality. A morphological opening operation is performed to sharpen the tumor region. In the segmented images, the statistical features and textural features are extracted. A set of performance measure is used to evaluate the system performance and comparison is made with the existing literature. The proposed system performs efficiently with high PSNR value of 17.0195 and lesser computation time of 2.04 s.

Biocatalytic Production of 2-α-d-Glucosyl-glycerol for Functional Ingredient Use: Integrated Process Design and Techno-Economic Assessment.

Advanced biomanufacturing builds on production processes that are both profitable and sustainable. Integrated design of process unit operations, geared to output efficiency and waste minimization and guided by a rigorous techno-economic assessment, is essential for development aligned to these central aims. Here, we demonstrate such a development for the biocatalytic production of the biological extremolyte 2-O-α-d-glucosyl-glycerol (2-GG) for functional ingredient application. The process was aligned in scale over all steps (∼180 g product; ∼2.5 L reaction mixture) and involved continuous enzymatic synthesis from sucrose and glycerol interlinked with reactive extraction and nanofiltration for product isolation (purity of ∼80 wt %) and side stream recovery. Glycerol used in ∼6-fold excess over sucrose was recycled, and hydrothermal conversion into 5-(hydroxymethyl)furfural was evaluated for the fructose by-product released from sucrose. Based on a process mass intensity (total mass input/mass product) of 146, ∼80% of the total mass input was utilized and an E-factor (mass waste/mass product) of 28 was obtained. EcoScale analysis revealed a penalty point score of 44, suggesting an acceptable process from a sustainability point of view. Process simulation for an annual production of 10 tons 2-GG was used for the techno-economic assessment with discounted cash flow analysis. The calculated operating costs involved 35 and 47% contributions from materials and labor, respectively. About 91% of the material costs were due to chemicals for the reactive extraction-acidic stripping step, emphasizing the importance of material reuse at this step. Glycerol recycling involved a trade-off between waste reduction and energy use for the removal of water. Collectively, the study identifies options and boundaries of a profitable 2-GG process. The minimum selling price for 2-GG was calculated as ∼240 € kg–1 or smaller. The framework of the methodology presented can be generally important in applied bio-catalysis: it facilitates closing of the gap between process design and implementation for accelerated development.

Development of a gamma irradiation loop to evaluate the performance of a EURO-GANEX process

A new irradiation loop design has been developed, which provides the ability to carry out radiolytic resistance studies of extraction systems simulating process relevant conditions in an easy and simple way. The step-by-step loop configuration permits an easy modification of settings and has a relative low volume requirement. This irradiation loop has been initially set up to test the main EURO-GANEX process steps: the lanthanide (Ln) and actinide (An) co-extraction followed by the transuranic (TRU) stripping. The performance and changes in the composition have been analyzed during the irradiation experiment by different techniques: gamma spectroscopy and ICP-MS for the extraction and corrosion behavior of the full system, and HPLC-MS and Raman spectroscopy to determine the degradation of the organic and aqueous solvents, respectively. The Ln and An co-extraction step and the corrosion that occurred during the first irradiation step revealed the favorable expected results according to literature. The effects of acidity changes occurred during the irradiation process, the presence of stainless corrosion products in solution as well as the new possible degradation compounds have been explored in the An stripping step. The results obtained demonstrate the importance of developing realistic irradiation experiments where different factors affecting the performance can be easily studied and isolated.

Closed-loop process for recovery of metals from NdFeB magnets using a trichloride ionic liquid

A solvometallurgical process was developed to recover rare-earth elements and cobalt from end-of-life NdFeB magnets, using the ionic liquid (IL) trihexyltetradecylphosphonium trichloride ([P666,14][Cl3]), or a mixture of [P666,14][Cl3] and the corresponding chloride IL [P666,14]Cl. The process comprises dissolution, stripping and regeneration of the ionic liquid. Pure [P666,14][Cl3] or its mixture with [P666,14]Cl could quantitatively dissolve NdFeB magnets when the solid-to-liquid ratio was less than a certain threshold value that depended on the volume percentage of [P666,14][Cl3] in the lixiviant. Increasing the temperature from 25 to 50 °C enhanced the dissolution rate significantly, but the dissolution efficiency increased only marginally. The volume percentage of [P666,14][Cl3] in [P666,14]Cl had a positive effect on the dissolution efficiency. The rare-earth and transition metals could be removed selectively by two sequential stripping steps, using 3 mol∙L−1 of NaCl aqueous solution and >2 mol∙L−1 of aqueous ammonia solutions, respectively. The regenerated IL [P666,14][Cl3] showed a similar dissolution efficiency to the fresh ionic liquid.

Insights into non-aqueous solvent extraction of gadolinium and neodymium from ethylene glycol solution using Cyanex 572

Comparison of the separation factors for Gd(III) over Nd(III) extraction from aqueous and non-aqueous ethylene glycol solutions using Cyanex 572 in kerosene. • Addition of water bridges the gap between hydrometallurgy and solvometallurgy. • Extraction of Gd(III) and Nd(III) from non-aqueous solution was compared with aqueous solution. • Gd and Nd extraction increases with increasing Cyanex 572 extractant concentrations. • Temperature had almost no effect on the extraction of both metal ions. • Under certain conditions, maximum separation factor was obtained and reached 22.09. The reprocessing of rare earth elements (REEs) by conventional hydrometallurgical processes remains a challenge because of the difficulties of separation. Solvometallurgy is a new non-aqueous solvent extraction approach including two immiscible organic phases which has been advanced for the extraction of rare earths. The less polar organic phase (LP) was a solution of Cyanex 572 (Cy-572) as an acidic extractant dissolved in kerosene. Whereas, the more polar organic phase (MP) was ethylene glycol with a limited amount of water dissolved in metal nitrate salts and lithium nitrate as a salting-out agent. The extraction of Gd(III) and Nd(III) from ethylene glycol solution was compared with extraction from an aqueous solution. The solvent extraction equilibrium was estimated by slope analysis method, and the composition of the Gd(III) extracted species in the less polar phase was proposed to be Gd(OH) L 2 . 2 HL ¯ . The non-aqueous system performs better separation of rare earths than the corresponding conventional extraction system. Subsequently, 0.1 mol/L HCl is the best stripping agent for both metal ions after two steps from the less polar phase, while a solution composed of 10% HF + 0.05 mol/L HCl is superior for nearly complete separation between the two elements. Eventually, the separation of binary mixtures of Gd(III) and Nd(III) is possible by this new non-aqueous solvent extraction system. A complete flow sheet process including extraction, scrubbing and stripping steps for the separation of Gd(III) and Nd(III) was proposed.

Microelectrocehmical Sensors for Water Quality Monitoring

The aim of this work is to micro-fabricate lead sensors that they will be low powered, cheap to make and easily mass-produced for distribution as hand-held portable devices1 or as long-term deployable devices. Lead is a toxic heavy metal that is linked to several adverse health effects. A report by the WHO identified lead as being responsible for 143,000 deaths annually. As of 2013, the WHO reduced the maximum allowable level of lead in drinking water from 50 ppb to 10 ppb. Microelectrodes fabricated by lithographic techniques on silicon are of great interest as they typically have a higher sensitivity than macroelectrodes of conventional size. This work will specifically focus on interdigitated microelectrodes. Interdigitated electrodes (IDEs) consist of two interlocking combs of electrodes and are typically used as generator-collector electrodes. Generator-collector (GC) electrodes are electrodes in which one side of the array is the generator and the other side of the array is the collector, the analyte of interest reacts at the generator and is converted into a new species which is then collected by the collector electrode and converted back to its original form where it is available again for reaction at the generator. This is known as a redox loop and can help boost the signal and decrease the limit of detection of the analyte. The arrangement of GC electrodes can also be exploited to electrochemically control the local pH of the electrodes. In this instance, the collector is held at a potential where it generates protons that locally change the pH of the solution of surrounding the IDE.2-5 The optimised IDE geometry, GC performance and pH control were all established using simulations carried out in COMSOL Multiphysics® software.The optimised fabricated IDEs were used to carry out analysis for the detection of lead. Unlike most electrochemical reactions where a potential is applied and the reaction of interest occurs, the detection of lead requires a two-step process. The first is a pre-concentration or deposition step where lead is deposited onto the electrode at a constant potential for a certain amount of time, and the second is the stripping step. In the stripping step a graph is obtained plotting current against the potential, the peak current obtained in this graph is proportional to the amount of lead in the sample being analysed. In this work, square wave voltammetry is being used for the stripping step. The detection of lead was further enhanced with nanoporous material,6-8 resulting in a 1.5-fold increase in current for the detection of lead at microelectrodes with nanoporous material compared to planar gold. Analysis of lead in both pH-controlled acetate buffer and tap water indicate the benefit of pH control for the detection of lead. The use of IDEs for pH control are also investigated for further enhanced detection of lead in tap water. Murphy, A; Seymour, I; Rohan, J. F; O’Riordan, A; O’Connell, I; Portable Data Acquisition System for Nano and Ultra-Micro Scale Electrochemical Sensors, IEEE Sensors Journal, 21(3), 2021, 3210-3215, 9186668.Seymour, I; O’Sullivan, B; Lovera, P; Rohan, J. F.; O’Riordan, A; Electrochemical detection of free-chlorine in Water samples facilitated by in-situ pH control using interdigitated microelectrodes, Sensors & Actuators B: Chemical, 2020.O’Sullivan, B; Patella, B; Daly, R; Seymour, I; Lovera, P; Rohan, J. F.; Inguanta, R; O’Riordan, A; A Simulation and Experimental Study of Electrochemical pH Control at Gold Interdigitated Microband Arrays, Electrochmica Acta, 395, 2021, 139113.Seymour, I; Narayan, T; Creedon, N; Kennedy, K; Murphy, A; Sayers, R; Kennedy, E; O’Connell, I; Rohan, J. F.; O’Riordan, A; Advanced Solid State Nano-electrochemical Sensors and Systems for Agri 4.0 Application, Sensors, 21, 2021, 3149.Seymour, I; O’Sullivan, B; Lovera, P; Rohan, J. F.; O’Riordan, A; Elimination of Oxygen Interference in the Electrochemical Detection of Monochloramine, using in-situ pH Control at Interdigitated Electrodes, ACS Sensors, 6, 2021, 1030.Nagle, L. C.; Rohan, J. F., Nanoporous Gold Catalyst for Direct Ammonia Borane Fuel Cells, Journal of the Electrochemical Society, 2011.Nagle, L.C.; Wahl, A; Ogurstov, V; Seymour, I; Barry, F; Rohan, J. F.; Mac Loughlin, R. Electrochemical Discrimination of Salbultamol from its Excipients in VentolinTM at Nanoporous Gold Microdisc Arrays, Sensors, 21, 2021, 3975.Twomey, K; Nagle, L. C.; Said, A; Barry, F, Ogurstov, V. I.; Characterisation of Nanaoporous Gold for Use in a Dissolved Oxygen Sensing Application, BioNanoSiences, 2015, 5:55-63. Figure 1

Abstract 2780: Development of automated multiplex immunofluorescence protocols for tumor microenvironment evaluation

Abstract Introduction: In recent years, the ability to detect several proteins on a single slide in Multiplex Immunofluorescence (mIF) experiments has become common place. This is possible thanks to factors such as development of antibodies of high quality, improvements in fluorescent technology, and automation of IHC staining. One of the advantages of multiplexing protein detection is to gain maximal data per tissue section, which is critical when samples are limited. Understanding co-expression and spatial organization of multiple targets within preserved tissue architecture is also important, especially in tumor microenvironment (TME) analysis. mIF plays a key role in research fields like tumor immunology where it is needed to catalog subsets of immune and cancer cells within the TME. Ultimately, this will enable the development of personalized, combinatorial therapeutic interventions. Materials and Methods: Selected antibody panels: Tonsil Panel 1: p40, CD3, CD8, CD20 & CD68 Tonsil Panel 2: LAG3 [BC40], LAG3 [CAL26], CD57, CD19, FOXP3, T-bet, PD-L1, PD-1 & GATA-3 Colon Cancer Panel: Granzyme B, CD8, CDX2, CD3 & Pan Cytokeratin Plus Melanoma Panel: Melan A, CD3, SOX10, CD8 & Granzyme B Detection was performed with Biocare MACH 2 Universal HRP Polymer. Fluorochromes: Opal 480, Opal 520, Opal 570, Opal 620, Opal 650 VALENT (Biocare Medical) fully automated staining platform was utilized to stain slides. Image acquisition and analysis was performed on an Olympus BX61 microscope coupled with the ASI FISH imaging system. In the workflow, a proprietary room temperature (RT) stripping reagent was utilized instead of the heat stripping step commonly used between antibody detection incubations. Results and Discussion: The antibodies used have been previously optimized for standard IHC protocols on VALENT using DAB. However, the sensitivity of tyramide detection is very high and for most of the antibodies, the incubation times had to be drastically reduced to minimize non-specific staining and the potential bleed-through to other filters for neighboring fluors. Additionally, Opal fluorochromes were diluted between 1:200 and 1:300. The RT stripping reagent helps in the preservation of tissue integrity even after the sequential detection of 5 antibodies. Additionally, by using this reagent, a rigorous order of primary antibody application is no longer needed. Finally, this reagent dimmed some autofluorescence coming from red blood cells. Following some brief optimization steps, we obtained strong and specific staining patterns similar to ones obtained with individual IHC experiments visualized with DAB. Conclusion: We have demonstrated the use on an automated platform of a RT stripping solution. Additionally, this reagent can be used with different antibodies in order to effectively characterize the TME in many cancers. Citation Format: Julio S. Masabanda, Sherry Wang, Joseph Vargas, Jason Ramos. Development of automated multiplex immunofluorescence protocols for tumor microenvironment evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2780.

Preferential Recovery of Rare-Earth Elements from Coal Fly Ash Using a Recyclable Ionic Liquid.

Recent global geopolitical tensions have exacerbated the scarcity of rare-earth elements (REEs), which are critical across many industries. REE-rich coal fly ash (CFA), a coal combustion residual, has been proposed as a potential source. Conventional REE-CFA recovery methods are energy- and material-intensive and leach elements indiscriminately. This study has developed a new valorization process based on the ionic liquid (IL) betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]) for preferential extraction of REEs from different CFAs. Efficient extraction relies on [Hbet][Tf2N]'s thermomorphic behavior with water: upon heating, water and the IL form a single liquid phase, and REEs are leached from CFA via a proton-exchange mechanism. Upon cooling, the water and IL separate, and leached elements partition between the two phases. REEs were preferentially extracted over bulk elements from CFAs into the IL phase and then recovered in a subsequent mild-acid stripping step, regenerating the IL. Alkaline pretreatment significantly improved REE leaching efficiency from recalcitrant Class-F CFAs, and additional betaine improved REE and bulk element separation. Weathered CFA showed slightly higher REE leaching efficiency than unweathered CFA, and Class-C CFA demonstrated higher leaching efficiency but less selective partitioning than Class-F CFAs. Significantly, this method consistently exhibits a particularly high extraction efficiency for scandium across different CFAs.

An integrated process of calcium hydroxide precipitation and air stripping for pretreatment of flue gas desulfurization wastewater towards zero liquid discharge

Flue gas desulfurization wastewater (FGDWW) is produced during flue gas desulfurization process in coal-fired power plants. It has a complex composition and high pollutant concentration and is harmful to the environment. The Chinese government has regulated the zero liquid discharge (ZLD) of FGDWW. To achieve this, an integrated process of calcium hydroxide precipitation and air stripping for the pretreatment of FGDWW was developed in this study. Ca2+ and OH− were added in the calcium hydroxide precipitation step and reacted with SO42−, F− and Mg2+ in the real FGDWW to form precipitates for removal. The SO42− concentration was lower than the detection limit at pH 4, and the F− and Mg2+ concentrations were reduced to 4 and 46 mg/L at pH 11, respectively. The NH4+ concentration decreased to 7.86 mg/L after air stripping for 120 min at pH 11. The excess Ca2+ was removed by further stripping, and the pH value decreased to about 8.0. The F− and NH4+ removal rates were significantly higher in the real than the simulated FGDWW. After the pretreatment, the concentrations of SO42−, F−, Mg2+, NH4+, Ca2+, total dissolved solids (TDS), and chemical oxygen demand (CODCr) in the real FGDWW decreased to 0.00, 1.5, 20.35, 8.26, 8.61, 8260 and 86 mg/L, and the corresponding removal rates were 100.00%, 97.50%, 99.59%, 96.43%, 98.97%, 78.48% and 94.29%, respectively. The molar concentration ratio of Cl− and Na+ changed from 3.14:1 in the raw FGDWW to 1.02:1 in the pretreated FGDWW by adding Na2CO3 in the air stripping step to reduce membrane fouling in the reverse osmosis (RO) process. The treated FGDWW could be recycled, and the by-products (gypsum, (NH4)2SO4, CaCO3 and NaCl) could be utilized. This technology achieved ZLD of FGDWW, representing a clean pathway and promoting the sustainable development of the power industry. The added chemicals did not remain in the pretreated FGDWW, adhering to with the principle of cleaner production. The pretreatment technology exhibited not only high removal efficiency for the main pollutants, but also low operational cost and convenient automatic control.

Optimising Adsorptive Stripping Voltammetry: Strategies and Limitations

AbstractThe widely employed electroanalytical technique of adsorptive stripping voltammetry (AdsSV) is critically assessed and evaluated at a wide and diverse range of unmodified and nano‐particle modified carbon electrodes using the analyte fipronil as a paradigmatic case. The generic electroanalytical performances of the nano‐particle modified electrodes are investigated and compared with the unmodified electrodes revealing similar LOD values and pointing to intrinsic limitations of AdsSV arising from the non‐independence of the Faradaic and capacitive signals during the stripping step. Methods for facilitating the adsorption or using different waveforms that may offer a more favourable limit of detection (LOD) at the nano‐particle modified electrodes are suggested and assessed, specifically the use of adsorption onto particles prior to their use for modifying electrodes and also the recently introduced method of semi‐circular voltammetry.

New process consisting of oxidative stripping of vanadium from loaded D2EHPA organic solution with H2O2 and direct precipitation with sulfuric acid

The traditional process of extracting V(IV) with di(2-ethylhexyl) phosphoric acid (D2EHPA) uses H2SO4 for V stripping and ammonium salt for V precipitation, leading to excessive consumption of H2SO4 and NH3·H2O, which results in a large volume of ammonia‑nitrogen wastewater. To solve this issue, a novel stripping reagent, H2O2, with the multifunction of oxidation and stripping, and a new method of precipitating vanadium from a solution of vanadium peroxy compounds were introduced to replace the traditional stripping reagent and ammonium salt precipitation, which requires separate stripping, oxidation, neutralisation and precipitation steps. The oxidative stripping of V from the loaded organic system consisting of 10% D2EHPA and 5% tri-butyl phosphate (TBP) in sulfonated kerosene using H2O2 was systematically investigated. The results indicated that 98.7% of the vanadium was stripped by three-stage cross-flow stripping under mild optimal conditions. Moreover, it was found that VO(O2)2–in the strip solution decomposed into VO(O2)+under oscillating conditions and the cation was synergistically re-extracted by D2EHPA and TBP, which resulted in a significant decrease in the stripping of vanadium and poisoning of the organic phase. The use of D2EHPA alone as the extractant can effectively prevent the problems encountered when H2O2 is used as the stripping reagent. The strip liquor could be used for direct precipitation of vanadium. A precipitation efficiency of 87% was obtained by adding a small amount of H2SO4. This new process combines oxidation, stripping and direct precipitation and exhibits the advantages of a short process flowsheet, with reagent savings (~95% decrease in H2SO4 consumption and no NH3·H2O consumption compared with traditional processes), and wastewater that is free of ammonia /nitrogen.

Selective recovery of zinc from mining sulfuric liquor employing aqueous two-phase systems

Zinc recovery is extremely important due to the chemical and physical properties of this metal. Liquid-liquid extraction technique allows the selective recovery of zinc, leading to a high purity product. For the first time, a concentrated mining sulfuric liquor as a stock solution for in situ preparation of an Aqueous Two-Phase System (ATPS) in a hydrometallurgical process. This liquor is an overly complex solution with a high content of metal ions, especially Zn2+ and Mg2+. ATPS technique has already shown good results when compared to traditional solvent extraction techniques and can be considered a greener technique. The proposed method was optimized to obtain selective Zn2+ extraction by studying the parameters: the nature of the ATPS-forming polymer and their concentration in the stock solution; the effect of the salt added to the system; the concentration of extractant agent and the mass ratio between both phases. The optimized methodology made it possible to extract (91.5 ± 0.1)% of Zn2+ and (18.2 ± 0.1)% of Mg2+ from the liquor in three extraction steps. In the stripping step which used NaOH as the precipitating agent, about 65 % of Zn2+ was selectively recovered at pH = 6.00 and at pH = 9.00 the recovery of Zn2+was close to 80 %. Furthermore, for the first time it was proven that the polymer and the extracting agent (following the stripping step) are reusable components of the ATPS. A high extraction efficiency (%EZn ∼ 45 %) was achieved in one extraction step using the recycled extraction phase without any adjustment.

Finding a suitable treatment solution for a leachate from a non-hazardous industrial solid waste landfill

The current study aimed at tackling the lack of effective treatment solutions for leachates from industrial solid waste landfills (ISWLs) through the development of a treatment train for a non-hazardous ISWL (NHISWL) leachate with low/moderate content of organics and salts and low biodegradability. The following technologies were tested: (i) coagulation using ferric chloride (FeCl3) or aluminium sulphate (Al2(SO4)3), (ii) biological oxidation, and (iii) chemical and electrochemical advanced oxidation processes (AOPs/EAOPs), including photo-Fenton oxidation using ultraviolet C (UVC) or ultraviolet A (UVA) radiation (PF-UVC or PF-UVA), anodic oxidation (AO), ozonation process and ozone (O3)-based processes. The best multistage treatment strategy included: (i) coagulation with FeCl3 for partial removal of organics (with direct impact on colour, odour and turbidity removal and biodegradability enhancement) and phosphorous, (ii) PF-UVC process for recalcitrant organics oxidation (with direct impact on colour and odour removal and biodegradability enhancement) coupled to a clarification step for removal of suspended solids, turbidity, iron and phosphorous, and (iii) biological process for removal of the generated biodegradable organics and of nitrogen compounds. Upon treatment, the NHISWL leachate fulfilled European and Portuguese requirements for discharge into aquatic systems, except for ammonium (and consequently for total nitrogen), pointing to the need to change the biological process conditions or add an air stripping step. The application of coagulation before the PF-UVC process has proved to be crucial for the fulfilment of the legislation requirements.

Observation of lithium stripping in super-concentrated electrolyte at potentials lower than regular Li stripping.

Lithium plating/stripping was investigated under constant current mode using a copper powder electrode in a super-concentrated electrolyte of lithium bis(fluorosulfonyl)amide (LiFSA) with methylphenylamino-di(trifluoroethyl) phosphate (PNMePh) and vinylene carbonate (VC) as additives. Typical Li plating/stripping for Cu electrodes in organic electrolytes of conventional lithium batteries proceeds at potentials of several millivolts versus a Li counter electrode. In contrast, a large overpotential of hundreds of millivolts was observed for Li plating/stripping with the super-concentrated electrolyte. When Li stripping started immediately after Li plating and with no rest time between plating and stripping, two potential plateaus, i.e., two-step Li stripping, was observed. The potential plateau for the 1st stripping step appeared at −0.2 V versus a Li metal counter electrode. The electrical capacity for the 1st stripping step was 0.04 mA h cm−2, which indicates irregular Li stripping. Two-step Li stripping was also recorded using cyclic voltammetry. The electrochemical impedance spectroscopy (EIS) studies indicated that the two-step Li stripping behaviour reflected two different solid electrolyte interphases (SEIs) on electrodeposited Li in a Cu electrode. The SEI for the 1st-step stripping was in a transition period of the SEI formation. The open circuit voltage (OCV) relaxation with an order of tens of hours was detected after Li plating and before Li stripping. The in operando EIS study suggested a decrease of the charge transfer resistance in the Cu powder electrode during the OCV relaxation. Since the capacitance for the voltage relaxation was a dozen microfarads, it had a slight contribution to the 1st-step Li stripping behaviour. The voltage relaxation indicated the possibility that it is difficult for Li ions to be electrodeposited or that the Li plating is in a quasi-stable state.

Extraction of uranium from sulfuric acid media using amino-diamide extractants

Two extractants, N,N′-((octylazanediyl)bis(ethane-2,1-diyl))dioctanamide (LI) and N,N′-((octylazanediyl)bis(ethane-2,1-diyl))di-2-methylheptanamide (LII), have been synthesised in two steps starting from diethylenetriamine and involving a peptide coupling step. The efficiency and selectivity of the extractants in dodecane/octanol (95/5 v/v) toward the extraction of uranium from sulfate media have been investigated showing that the uranium extraction from sulfuric acid is more efficient at a low H2SO4 concentrations. Slope analysis method revealed 2:1 extractant/metal ratio, which is in accordance with NMR titration as well as DFT calculations. The extractants are found to be selective toward uranium over competitive cations present in a simulated leach solution. Finally, a stripping step has been performed and given rise to a successful quantitative recovery of uranium.

Enhanced Separation of Neodymium and Dysprosium by Nonaqueous Solvent Extraction from a Polyethylene Glycol 200 Phase Using the Neutral Extractant Cyanex 923.

Neodymium and dysprosium can be efficiently separated by solvent extraction, using the neutral extractant Cyanex 923, if the conventional aqueous feed phase is largely replaced by the green polar organic solvent polyethylene glycol 200 (PEG 200). While pure aqueous and pure PEG 200 solutions in the presence of LiCl or HCl were not able to separate the two rare earth elements, high separation factors were observed when extraction was performed from PEG 200 chloride solutions with addition of small amounts of water. This addition of water bridges the gap between traditional hydrometallurgy and novel solvometallurgy and overcomes the challenges faced in both methods. The effect of different variables was investigated: water content, chloride concentration, type of chloride salt, Cyanex 923 concentration, scrubbing agent. A Job plot revealed the extraction stoichiometry is DyCl3·4L, where L is Cyanex 923. The McCabe-Thiele diagram for dysprosium extraction showed that complete extraction of this metal can be achieved by a 3-stage counter-current solvent extraction process, leaving neodymium behind in the raffinate. Finally, a conceptual flow sheet for the separation of neodymium and dysprosium including extraction, scrubbing, stripping, and regeneration steps was presented. The nonaqueous solvent extraction process presented in this paper can contribute to efficient recycling of rare earths from end-of-life neodymium-iron-boron (NdFeB) magnets.

Functionalized Dipicolinic Acid Derivatives as TALSPEAK-MME Stripping Agents

ABSTRACT This work describes the results of an assessment of two derivatives of dipicolinic acid (DPA) as the actinide-selective stripping reagents in the combined HEH[EHP]/Cyanex-923 system, TALSPEAK-MME (mixed monofunctional extractants). One purpose of this investigation is to demonstrate probable advantages derived in phase-transfer kinetics by deploying dipicolinates as preorganized aminopolycarboxylate complexants in TALSPEAK-derived separation systems. The investigation is focused on the behavior of the lanthanides, Am, and selected transition metals (Zr, Mo, Pd, Ru, and Rh) in the extraction, solvent conditioning, and stripping steps. Solvent conditioning with glycine buffer solutions is shown to be effective for the removal of entrained HNO3 while also managing Pd concentration prior to actinide stripping. The efficacy of the DPA derivative during the actinide-selective strip was assessed, focusing explicitly on the effects of pH and ligand concentration and evaluating the stripping kinetics. These ligands were shown to be highly selective for americium, producing in the TALSPEAK-MME platform separation factors comparable to commonly used actinide selective stripping agents for radiotracer Eu, Am, a trans-lanthanide series and selected transition metals. The stripping kinetics study revealed very rapid phase-transfer reactions, reaching equilibrium in less than 10 s on vigorous agitation. Further work will be required to address the possible contamination of the product by selected transition metals (such as Zr) during the stripping step.

Evaluation of novel imino-phenol ligands in divalent metal ion extraction/recovery processes from leaching solutions

A set of imino-phenol ligands L1–L8 were synthesized and fully characterized by spectroscopic methods (NMR, FTIR, UV/Vis and MS) with good yields (≥60%). Ligands L1–L8 were used for the preparation of copper complexes C1–C8 from their reactions with Cu(OAc)2·H2O in a ligand/Cu(II) molar ratio of 2:1. Then, a set of solvent-extraction (SX) experiments for Cu(II) were performed at room temperature for 60 min at pH 4.5, and L8 exhibited the highest value (75%) for Cu(II) extraction. Cu(II) stripping studies were then performed at 50 °C for 60 min with L1 and L5–L7 at pH 3.0 and L8 at pH since these ligands decompose at lower pH values. Notably, L1 and L6 achieved the best results for the stripping step, yielding 46% and 47% extraction, respectively. On the other hand a set of competitive extraction studies were performed with different divalent metal ions (Cu(II), Co(II), Ni(II) and Mn(II)) using L8 and good extraction values (57–75%) were obtained for all of the metal ions at pH 4.5. Finally, extraction/stripping selectivity experiments were performed with the aforementioned metal ions using L8 and L1. L8 exhibited good selectivity for Cu(II) (75%) in the extraction process at pH 4.5, whereas L1 produced moderate values of selectivity (approximately 60%) for all of the divalent metal ions at pH 3.0 in the stripping process.