Slurry Electrolysis Research Articles

Intensified hydrogen production and desulfurization at elevated temperature and pressure during coal electrolysis

Elevation of temperature and pressure was used as an effective way to reduce the electrochemical resistance and improve the liquid mass transfer during the coal electrolysis without membrane, thus enhancing the desulfurization and hydrogen production. Results indicated that the high temperature and pressure have effectively reduced the electrochemical resistance (Rct) and solution resistance (Rs) for coal electrolysis. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) potentials for coal-water slurry electrolysis was obviously seen to increase with increasing temperature and pressure. What's more, the difference between the potential of OER and the equilibrium potential of OER (over-potential) also increased with the intensified condition, which was defined as the metastable zone width (MZW), indicating that HO formation was improved by the high temperature and pressure. As expected, the elevation in temperature and pressure has successfully resulted in the decrease in cell voltage and the increase in coal desulfurization during the electrolysis.

Completely separating metals and nonmetals from waste printed circuit boards by slurry electrolysis

Abstract Completely separating and recovering metals and nonmetals from waste printed circuit boards (WPCBs) is key to e-waste recycling. Here we proposed a novel approach, slurry or suspension electrolysis, to separate metals and nonmetals from WPCBs. The factors that impact the separation rate during the slurry electrolysis were discussed in detail. The results indicate that CuSO4·5H2O, NaCl, H2SO4, WPCBs dosage, current and time could impact metals separating from WPCBs. Increasing NaCl and H2SO4 concentration and extending electrolysis time could effectively increase the metal and nonmetal separation rate, while increasing WPCBs dosage and current have negative impacts on the metal and nonmetal separation rate. Slurry electrolysis could directly and completely separate and recover metals from WPCBs with a separation rate up to 97.79% under the conditions of 3 g WPCBs dosage in 100 mL electrolyte, 30 g/L CuSO4·5H2O, 40 g/L NaCl, 150 g/L H2SO4, 0.5 A and 9 h. The separated micro-metal powders are mainly Cu, about 86.6%, without any nonmetal powders. Copper recovered is dendritic, with a copper recovery rate up to nearly 99%. Thus, slurry electrolysis shows a prospective future in e-waste reutilization, providing a way to enrich metals for all kinds of urban mines.

Recovery of copper from WPCBs using slurry electrolysis with ionic liquid [BSO3HPy]∙HSO4

Due to rapid innovation in electronic industries, the average lifetime of electronic devices has been shortening drastically, leading to a massive electronic waste production (E-waste). As an essential part of E-waste, waste printed circuit boards (WPCBs) attract considerable concerns to seek a green and cost-effective recycling approach. In this study, a green chemical, [BSO3HPy]HSO4, was used to replace H2SO4 in a slurry electrolytic system in order to recover valuable metal copper from WPCBs in one-step. The results indicate that as more H2SO4 is replaced by [BSO3HPy]HSO4, copper recovery rate and current efficiency first increased and then decreased, while copper powders purity showed a reverse tendency: increases first and then decreases. The substitution of H2SO4 by [BSO3HPy]HSO4 could effectively reduce the particle size of the obtained powders. When 10% H2SO4 was replaced by [BSO3HPy]HSO4, the recovery rate, current efficiency, purity and particle size of copper powders were 90.94%, 70.68%, 81.69% and 2.30μm, respectively, thus reaching an optimal level. XRD results show that elemental Cu was the main mineral phase in the obtained powders. SEM and TEM results indicate that copper powders obtained in H2SO4-slurry-electrolysis system is dendritic and polycrystalline, whereas those obtained in an electrolytic solution with [BSO3HPy]HSO4 were in form of scattered monocrystalline particles.

Superfine copper powders recycled from concentrated metal scraps of waste printed circuit boards by slurry electrolysis

Printed circuit board is an essential part of almost all electrical and electronic equipment (EEE). As the rapid increase of waste EEE (WEEE), caused by the shorter and shorter life span and the accelerated innovation of information communication technologies, waste printed circuit boards (WPCBs) is being a hot issue due to its characteristics of resource abundant but hazardous. In this research, the concentrated metal scraps, obtained by WPCBs mechanical separating, were directly recycled to superfine copper powders by slurry electrolysis. And the effect of polyvinyl pyrrolidone (PVP), oleic acid and H2SO4 concentration, current density and electrolysis time on the purity and particle size of copper powders were discussed in detail. Results showed that all these factors could intensively impact the obtained copper particle size, which became finer as the increase of current density and coarser with the extension of time. Copper powder purity first increased and then decreased as the increase of PVP, oleic acid and H2SO4 concentration. The purity of copper can reach to 99.3% with a particle size of 7.142 μm under the optimum conditions: 30 g/L CuSO4·5H2O, 60 g/L NaCl, 150 g/L H2SO4, 30 g/L PVP, 6 mL/L oleic acid, 80 mA/cm2 for 4 h. XRD analysis indicated that copper was the main phase; SEM and TEM analysis showed that the obtained copper powders were dendritic single crystal coated by a layer of PVP and oleic acid. Therefore, slurry electrolysis could be a perspective approach for WPCBs recycling.

ANODE GAS DYNAMICS IN HIGH-TEMPERATURE CRYOLITE MELT-ALUMINA SLURRY

The paper shows the results of simulating physical behavior of bubbles formed by oxygen electrowinning on an inert anode during hightemperature alumina slurry electrolysis in a fluoride melt. As part of the study, similarity criteria were calculated with experiments conducted on a water-based model of a cell with vertical electrodes, and the data on bubble behavior in slurry was obtained by video recording. The 20 % aqueous sulfuric acid solution with 30 vol.% alumina content was used as electrolyte for the model. Experiments were conducted in the electric current density range from 0,05 to 0,25 A/cm2. The video was recorded using the Nikon D3100 camera with 30 frames per second rate. The motion pattern of bubbles was obtained along with the quantitative data describing coalescence and bubble rise velocity. 125 bubbles with a thickness of 0,8 to 2,3 mm were analyzed to determine the average bubble rise velocity. Bubbles rose in a slug regime at 1,0–2,3 cm/s. The thickness of a bubble layer was about 5 mm. Further studies will be conducted to obtain new data on the bubble behavior at different solid contents, current densities, electrodes inclination angles, and particle size distributions.

Исследование поведения пузырей при электролизе суспензии криолитовый расплав – глинозем

Physical modeling of oxygen bubbles generated on the inert anode as a result of electrochemical evolution at cryolite melt – alumina slurry electrolysis movement, growth and evacuation results are presented in the paper. Similarity criteria are calculated, experiments are performed on two types of cell: for three phase flow at vertical electrode observation from front and side views. The behaviour of bubbles in slurry was recorded. For the model, an 20 % aqueous solution of sulfuric acid with 30 vol. % of alumina was used. Current density range was 0.05 to 0.25 A/cm2. Bubble behavior information allows estimating the ability of effective gas evacuation from the inter-electrode space during slurry electrolysis. The highest bubbles vertical speed (2.5 cm/s) was reached at 15 to 20 cm depth from the electrolyte – atmosphere border, after which the speed was reduced. Bubble layer thickness does not exceed 2.2 mm. Bubble’s average growth rate was 2.68 mm3/s.

Effects of electrolyte recycling on desulfurization from bauxite water slurry electrolysis

To lower the cost of bauxite electrolysis desulfurization using NaOH solution as the supporting electrolyte, effects of electrolyte recycling on bauxite electrolysis desulfurization were investigated. The results indicate that electrode corrosion, cell voltage, the desulfurization rate and the pH value of the electrolyte have no obvious changes with the increase of cycle times. Additionally, there were some transitive valence S-containing ions in electrolyte after the electrolysis, such as SO32−, S2O32−. However, most of the sulfur in bauxite was eventually oxidized into SO42− into the electrolyte, and these S-containing ions did not affect the recycling utilization for electrolyte.

Desulfurization from Bauxite Water Slurry (BWS) Electrolysis

Feasibility of high-sulfur bauxite electrolysis desulfurization was examined using the electrochemical characterization, XRD, DTA, and FTIR. The cyclic voltammetry curves indicated that bauxite water slurry (BWS) electrolysis in NaOH system was controlled by diffusion. Additionally, the desulfurization effect of NaCl as the electrolyte was significantly better than that of NaOH as an electrolyte. As the stirring rate increased, the desulfurization ratio in NaCl system was not increased obviously, while the desulfurization ratio in NaOH system increased significantly, indicating further that electrolysis desulfurization in NaOH solution was controlled by diffusion. According to XRD, DTA, and FTIR analysis, the characteristic peaks of sulfur-containing phase in bauxite after electrolysis weakened or disappeared, indicating that the pyrite in bauxite was removed from electrolysis. Finally, the electrolytic desulfurization technology of bauxite was proposed based on the characteristics of BWS electrolysis.

Desulfurization kinetics and mineral phase evolution of bauxite water slurry (BWS) electrolysis

The desulfurization kinetics and mineral phase evolution from bauxite water slurry (BWS) electrolysis were examined. The results showed that the desulfurization ratio in NaCl system increased with current density, and reached up to 96% at 0.22A/cm2. In contrast, the desulfurization ratio in NaOH system increased firstly, and then decreased with current density, which was relative to the lifetime of oxidizing media from electrolysis. It was noted that pH value of electrolyte had some crucial effects on oxidant species and surface of FeS2, and thus the desulfurization ratio increased with the decrease in pH value of electrolyte. According to desulfurization kinetics, electrolysis desulfurization in NaCl solution was controlled by internal diffusion, and the apparent activation energy was 18.68kJ/mol. However, electrolysis desulfurization process in NaOH solution was controlled by interface chemical reaction, and the apparent activation energy was 25.77kJ/mol.

Sulfur removal from bauxite water slurry (BWS) electrolysis intensified by ultrasonic

Effects of ultrasonic on desulfurization ratio from bauxite water slurry (BWS) electrolysis in NaOH solution were examined under constant current. The results indicated that ultrasonic improved the desulfurization ratio at high temperatures because of the diffusion and transfer of oxygen gas in electrolyte. However, due to the increase in oxygen gas emission, ultrasonic could not improve the desulfurization ratio obviously at low temperatures. Additionally, the particle size of bauxite became fine in the presence of ultrasonic, indicating that the mass transfer of FeS2 phase was improved. According to the polarization curves, the current density increased in the presence of ultrasonic, indicating that the mass transfer of liquid phase was improved. The apparent activation energy (AAE) of electrode reaction revealed that ultrasonic did not change the pathway of water electrolysis. However, ultrasonic changed the pathway of BWS electrolysis, converting indirect oxidation into direct oxidation. The AAE of BWS electrolysis in the presence of ultrasonic was higher than that in the absence of ultrasonic. And the low AAEs (less than 20kJ/mol) clearly indicated the diffusion control during BWS electrolysis reaction.

Summary of Progress in Extracting Vanadium

This paper mainly summarizes the vanadium leaching process from bone coal, steel slag containing vanadium, catalystcontaining vanadium, including their leaching condition , application circs and these materials’ respective merits and faults under production process. bone coal and steel slag containing vanadium are the usual raw materials and the extracting of vanadium are divided into full wet extraction method and roasting-wet extraction method.The later applied more widely. At the same time, give some short introduction of other new method such as selective precipitation ,slurry electrolysis ,microbial leaching and so on.

Variation with time of cell voltage for coal slurry electrolysis in sulfuric acid

To explain the time dependence of cell voltage in CWS (coal water slurry) electrolysis, the effects of three coal types along with graphite, CWS concentration and catalysts on cell voltage are examined. Results show that the overall cell voltage for CWS electrolysis is lowered as coal rank decreases. The four overall types carbonaceous material show successive reductions in Uθ + η for CWS electrolysis which are greater than those of iR, where Uθ is the theoretical reversible potential for water electrolysis, and η is the sum of the anodic and cathodic over-potentials. The cell voltage for DLWS(demineralized lignite water slurry ) electrolysis is lowered by addition of Fe2+ or Fe3+ ions, the former being more effective. The cell voltage for DBWS (demineralized bituminous water slurry) electrolysis decreases with the addition of transition metal ions in the order Fe2+<Ni2+<Co2+. Additionally, it is found that the DLWS electrolysis cell voltage is lowered with increasing DLWS concentration. Results suggest that cell voltage reduction may be attributed to the decrease in Uθ + η for CWS electrolysis.

Changes of total organic carbon and kinetics of ultrasonic-assisted coal water slurry electrolysis in NaOH system

Coal water slurry (CWS) electrolysis not only improved efficiency of water electrolysis for hydrogen, but also removed sulfur and mineral matters in coal. Fortunately, it may be a potential method which obtained directly organic compounds from coal. However, both the stability and mass transfer of coal particle were very poor during CWS electrolysis. As we known, ultrasonic wave can improve the stability for CWS and mass transfer strength of coal particle. In this paper, ultrasonic-assisted CWS electrolysis was carried out in NaOH solution. Results showed that the total organic carbon (TOC) concentration for CWS electrolysis increased. According to the results from kinetics study, it was not difficult to find that the chemical reaction is the controlling-step for CWS electrolysis. And the apparent activation energy (AAE) changed from 28.37 to 27.61kJmol−1 with ultrasonic addition. The slight change in the AAE suggested that the ultrasonic improved the mass transfer of coal particle only in electrolyte, and did not change reaction path. Additionally, TOC concentration decreased with the increase in mineral matter content, indicating that the mineral matters inhibited the organic structure electrolysis.

Sulfur removal from ionic liquid-assisted coal water slurry electrolysis in KNO3 system

Ionic liquid-assisted coal water slurry (CWS) electrolysis was carried out in KNO3 system with constant current. The effects of ionic liquids including structure, concentration, temperature and time on the removal of sulfur were investigated to intensify desulfurization ratio from CWS electrolysis. Given the organic structure of imidazole, the influence of anions on the desulfurization was in the following order: Br− >BF4− >Cl−. Given the same anion of Br−, imidazole showed better performance than pyridine in terms of sulfur elimination. With increasing N-butylpyridinium bromide ([BPy]Br) concentration, the desulfurization ratio increased at the initial stage, and then decreased after 0.30 mol/L. Additionally, the desulfurization ratio continuously increased with time and temperature. Finally, the organic sulfur occurrences in coal before and after experiments were characterized by XPS technique. Results showed that the removal of thiophene was improved due to the extraction-oxidation effects and others (i.e. thioethers and sulfoxide) were removed mainly via enhanced oxidation and hydrolysis reactions.

Roles of inherent mineral matters for lignite water slurry electrolysis in H2SO4 system

To understand roles of inherent mineral matters in lignite water slurry (LWS) electrolysis, lignite and demineralized lignite electrolyses were carried out in H2SO4 system. The results showed that cell voltage for LWS electrolysis was lower than that for demineralized lignite water slurry (DLWS) under constant current condition. Some inherent mineral matters changed into the corresponding metal ions which entered into electrolyte, and thus improved the electrolysis oxidation reactions for coal organic structure. Meanwhile, the relative amount of O-containing functional groups in demineralized lignite increased with electrolysis time, improving its pyrolysis reactivity. However, the pyrolysis reactivity of raw lignite decreased due to the removal of the inherent mineral matters from electrolysis.

Electrolysis of coal slurries to produce hydrogen gas: Effects of different factors on hydrogen yield

The study was aimed to investigate the effects of different factors (such as acid concentration, cell potential, temperature, coal types, and geometric area of the membrane) on the coal slurry electrolysis and hydrogen evolution. It was observed that all of the above factors affected hydrogen production upon completion of the electrolysis. The results revealed that an increase in the initial acid concentration up to 5.0 M brought about an increase in the current density and hydrogen evolution. However, the higher the acid concentration was taken (>7.0 M) then the lower the current density and hydrogen evolution were, which resulted in significant change due to the agglomeration of coal samples and stuck on the electrode surface. Furthermore, the CO 2 evolution (14 ml) was observed only at high temperature (100 °C) and high (2.0 V) cell potential when the H 2 amount was 776 ml. The coal type was observed to have influenced the electrolysis.

Use Copper Slag to Prepare Copper Matrix Composites

Copper slag was used to prepare copper powder by way of slurry electrolysis, and the copper powder was used to fabricate copper matrix composite materials reinforced with chemical plating surface modified alumina particulates. Alumina particulates were pretreated in ultrasonic field by chemical copper plating in order to make alumina particulates covered with a layer of copper film and form Al2O3/Cu composite powders. Copper matrix composite materials strengthened with alumina particulates were synthesized by means of pressure molding and sintering. Microstructure of copper matrix composites was researched by means of SEM. SEM analysis shows that alumina particulates distribute in the copper-based body evenly, and combine with copper closely. The effects of sintering temperature, pressure and alumina content on the compactness and hardness of copper matrix composites were studied by orthogonal tests. The compactness of composites increases with the sintering temperature and pressure increasing, and decreases with the alumina content increasing. The hardness of composite materials increases with the sintering temperature, pressure and alumina particulates increasing.

Slurry electrolysis of ocean polymetallic nodule

The ocean poly-metallic nodule was leached by using slurry electrolysis process in HCl-NaCl medium. The leaching rates of Mn, Co, Cu and Ni in the ocean poly-metallic nodule are all above 97%. Meanwhile, the high purity of electrolytic MnO 2 is also obtained as an anode product. The effects of electrolysis electric quantity, acidity, temperature, slurry density, grain size and iron ions concentration were studied. The results show that the ocean poly-metallic nodule can be treated economically in the slurry electrolysis process.

Detoxification of tributyltin contaminated sediments by an electrochemical process

Preliminary experiments have shown that dibutyl and tributyltin can be decomposed by the electrochemical treatment of sediment. Two different process pathways have been described and compared. A slurry electrolysis of the suspended sediment seemed to be more efficient than column leaching followed by electrolysis. Tributyltin was destroyed under oxidising as well as under reducing process conditions. The detoxification mechanism seemed to be stepwise removal of the butyl groups. A partial debutylation of tri- and dibutyltin could be achieved, although monobutyltin was not affected. This technique is promising, but further investigation is necessary to improve the experimental conditions and to characterise the real potential of these process pathways.

Oxidation of arsenopyrite (FeAsS) in acid Part I: Reactivity of arsenopyrite

The oxidation reactivity of arsenopyrite FeAsS in dilute acid determines the recovery of gold from arsenopyritic gold ores by slurry electrolysis. Stoichiometric,sulfur- and arsenic- deficient arsenopyrite have practically the same oxidation rate. Arsenopyrite is covered with a metal deficient sulfide layer which appears to determine the restpotential of the electrode. This layer can be separately oxidized and reduced during bulk-oxidation of arsenopyrite. Arsenopyrite oxidation is accelerated by dissolved Na2SO4 and by high electrode potentials and solution acidity. The rate is controlled by a surface reaction with an apparent activation energy of 33kJmol−1.