Browsing by Author "Aji, Arif T."
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- Extraction of Li and Co from industrially produced Li-ion battery waste – Using the reductive power of waste itself
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-07-15) Peng, Chao; Liu, Fupeng; Aji, Arif T.; Wilson, Benjamin P.; Lundström, MariIndustrially produced spent lithium-ion batteries (LIBs) waste contain not only strategic metals such as cobalt and lithium but also impurity elements like copper, aluminum and iron. The current work investigates the distribution of the metallic impurity elements in LIBs waste, and their influence on the acid dissolution of target active materials. The results demonstrate that the presence of these, naturally reductive, impurity elements (e.g. Cu, Al, and Fe) can substantially promote the dissolution of active materials. Through the addition of Cu and Al-rich larger size fractions, the extraction efficiencies of Co and Li increased up to over 99%, to leave a leach residue that is rich in graphite. By this method, the use of high cost reductants like hydrogen peroxide or ascorbic acid could be avoided. More importantly, additional Co and Li associated with the Cu and Al electrode materials could be also recovered. This novel approach contributes not only to improved reduction efficiency in LIBs waste leaching, but also to improved total recovery of Co and Li from LIBs waste, even from the larger particle size fractions, which are typically lost from circulation. - Industrial validation of conductivity and viscosity models for copper electrolysis processes
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-09-01) Kalliomäki, Taina; Aji, Arif T.; Jafari, Shila; Leskinen, Waltteri; Wilson, Benjamin P.; Aromaa, Jari; Lundström, MariIn copper electrorefining and electrowinning, the conductivity and viscosity of the electrolyte affect the energy consumption, and for electrorefining the purity of cathode copper. Consequently, accurate models for predicting these properties are highly important. Although the modeling of conductivity and viscosity of synthetic copper electrolytes has been previously studied, only a few models have been validated with actual industrial electrolytes. The conductivity and viscosity models outlined in this study were developed using conductivity and viscosity measurements from both synthetic and industrial solutions. The synthetic electrolytes were investigated over a temperature range between 50–70 °C and typical concentrations of Cu (40–90 g/dm3), Ni (0–30 g/dm3), Fe (0–10 g/dm3), Co (0–5 g/dm3), As (0–63.8 g/dm3), H2SO4 (50–223 g/dm3) as well as other solution impurities like Sb in some cases. Validation of the synthetic electrolyte models was performed through industrial measurements at three copper plants across Europe. Generally, the developed models predicted the conductivities and viscosities of industrial solutions with high accuracy. The viscosity models covered extended ranges of both [H2SO4] and [Cu] with percentage errors of only (2.08 ± 0.59) - (2.48 ± 0.61). For conductivity, two different models for low (<142 g/dm3) and high (>142 g/dm3) [H2SO4] electrolytes were utilized. Their error margins were (−1.96 ± 0.84) - (−1.44 ± 0.35) and (1.17 ± 0.27) - (2.52 ± 0.28), respectively. In the case of high [H2SO4] electrolytes, the validations focused on conductivity, and the highest level of accuracy was obtained when the effects of Sb and other minor impurities were considered. - Modelling the effect of temperature and free acid, silver, copper and lead concentrations on silver electrorefining electrolyte conductivity
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2016-12-01) Aji, Arif T.; Kalliomäki, Taina; Wilson, Benjamin P.; Aromaa, Jari; Lundström, MariConductivity is one of the key physico-chemical properties of electrolyte in silver electrorefining since it affects the energy consumption of the process. As electrorefining process development trends towards high current density operation, having electrolytes with high conductivities will greatly reduce the energy consumption of the process. This study outlines investigations into silver electrorefining electrolyte conductivity as a function of silver, free acid, copper and lead concentration at different temperatures via a full factorial design comprising of 246 individual measurements. Regression analysis of the model was used to determine the goodness of fit R2, goodness of prediction Q2, model validity and reproducibility. Conductivity was shown to be enhanced by increases in free acid, copper, silver and lead, with free acid having the highest impact on conductivity. Temperature also increased conductivity in two ways: both as a single factor and as a combined effect with free acid, silver and copper concentration. Overall, this work produced a model of high accuracy that allows conductivity of a range of industrial silver electrorefining conditions to be calculated. - Models for viscosity and density of copper electrorefining electrolytes
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2017) Kalliomaki, Taina; Aji, Arif T.; Rintala, Lotta; Aromaa, Jari; Lundstrom, MariViscosity and density of copper electrorefining electrolytes affect energy consumption and purity of cathode copper. Decreasing the viscosity and density increases the rate of falling of the anode slimes to the bottom of an electrorefining cell and increases the diffusivity and mobility of ions. Increasing the falling rate of the anode slimes decreases a risk of anode slime impurities ending up on the cathode and being entrapped into the copper deposit. This work introduces two new models for both viscosity and density of copper electrorefining electrolytes with high accuracy and one reconstructed improved model for some electrorefining data of viscosity published previously. The experimental work to build up these new models was carried out as a function of temperature (50, 60, 70 °C), copper (40, 50, 60 g/dm3), nickel (0, 10, 20 g/dm3) and sulfuric acid (130, 145, 160 g/dm3) concentrations for all models, and additionally arsenic concentration (0, 15, 30, 32, 64 g/dm3) was included in the viscosity models. Increasing concentrations of Cu, Ni, As and H2SO4 were found to increase the viscosity and density, whereas increasing temperature decreased both viscosity and density. The viscosity models were validated with industrial electrolyte samples from the Boliden Harjavalta Pori tankhouse. The experimental and modeling work carried out in this study resulted in improved viscosity models, having the strongest agreement with the industrial electrorefining electrolytes. - The optimum electrolyte parameters in the application of high current density silver electrorefining
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2020-12) Aji, Arif T.; Aromaa, Jari; Lundström, MariIncreasing silver production rate has been a challenge for the existing refining facilities. The application of high current density (HCD) as one of the possible solutions to increase the process throughput is also expected to reduce both energy consumption and process inventory. From the recently-developed models of silver electrorefining, this study simulated the optimum electrolyte parameters to optimize the specific energy consumption (SEC) and the silver inventory in the electrolyte for an HCD application. It was found that by using [Cu2+] in electrolyte, both objectives can be achieved. The suggested optimum composition range from this study was [Ag+] 100–150 g/dm3, [HNO3] 5 g/dm3, and [Cu2+] 50–75 g/dm3. HCD application (1000 A/m2) in these electrolyte conditions result in cell voltage of 2.7–3.2 V and SEC of 0.60–1.01 kWh/kg, with silver inventory in electrolyte of 26–39 kg silver for 100 kg per day basis. The corresponding figures for the conventional process were 1.5–2.8 V, 0.44–0.76 kWh/kg, and 15.54–194.25 kg, in respective order. These results show that, while HCD increases SEC by app. 30%, the improvement provides a significant smaller footprint as a result of a more compact of process. Thus, applying HCD in silver electrorefining offers the best solution in increasing production capacity and process efficiency. - Viscosity and density models for copper electrorefining electrolytes
A4 Artikkeli konferenssijulkaisussa(2016) Kalliomäki, Taina; Aji, Arif T.; Aromaa, Jari; Lundström, MariViscosity and density are highly important physicochemical properties of copper electrolyte since they affect the purity of cathode copper and energy consumption [1, 2] affecting the mass and heat transfer conditions in the cell [3]. Increasing viscosity and density decreases the rate in which the anode slime falls to the bottom of the cell [4, 5] and lowers the diffusion coefficient of cupric ion (DCu2+) [6]. Decreasing the falling rate of anode slime increases movement of the slime to other directions than downward [4, 5]. If the anode slime ends up on the cathode, the impurities could entrap into coating [4]. Due to that the aim is to keep the viscosity and density sufficiently low [4]. According to the studies of Price and Davenport [3], Subbaiah and Das [2], Devochkin et al. [7] as well as Jarjoura et al. [8] increasing the concentration of copper, nickel and sulfuric acid increases both viscosity and density, while temperature decreases these properties. In addition, Price and Davenport [1] researched the effect of impurities arsenic and iron as well as Subbaiah and Das [2] the effect of iron, manganese and cobalt. All of these researchers found that those impurities increased both viscosity and density. The density and kinematic viscosity of copper electrorefming electrolytes have not been extensively researched under electrorefming conditions. The kinematic viscosity is also an important factor in the equation defining DCu2+ using a rotating disc electrode technique [6]. The errors in the viscosity values cause significant error to DCu2+. Thus, this work introduces mathematical models for the density and kinematic viscosity. The kinematic viscosity of the test electrolytes was measured with a Ubbelohde capillary viscometer from Schott-Gerate GmbH and the density with a glass tube oscillator DMA 40 Digital Density Meter from Anton Paar K. G. The temperature (50, 60, 70 degrees C) and electrolyte composition were used as variables. The composition variables investigated were copper (40, 50, 60 g/dm(3)), nickel (0, 10, 20 g/dm(3)) and sulfuric acid (130, 145, 160 g/dm(3)) in all models, and additionally the effect of arsenic acid for the viscosity was studied (0, 15, 30 g/dm(3)). The electrolytes used in these tests were prepared from CuSO4-5H(2)O (99-100 %), NiSO(4 center dot)7H(2)O (99-100 %), H2SO4 (95-97 %) and arsenic acid (containing As 151700 mg/dm(3), Bi 6.2 mg/dm(3), Se 0.07 mg/dm(3), Te 18.6 mg/dm(3), Ag 0.2 mg/dm(3), Cu 4794 mg/dm(3), Ni 1688 mg/dm(3), Pb 28.62 mg/dm(3) and Sb 3954 mg/dm(3)). The results were normalized using known water values for viscosity as well as water and air values for the density. Based on these results the models for density (rho, g/cm(3)) and kinematic viscosity (nu, mm(2)/s) were designed, refined and analyzed using modeling and design tool MODDE, Equation 1 for density and 2 for kinematic viscosity: rho = 1.03473 + 0.00216707 [Cu] + 0.000535362 [H2SO4] + 0.00234682 [Ni] - 0.000713461 T