Browsing by Author "Badenhorst, Wouter"

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Bipolar Membrane Electrodialysis for Sulfate Recycling in the Metallurgical Industries
(2021-09-18) Kuldeep, Kuldeep; Badenhorst, Wouter; Kauranen, Pertti; Pajari, Heikki; Ruismäki, Ronja; Mannela, Petri; Murtomäki, Lasse
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Demand for nickel and cobalt sulfate is expected to increase due to the rapidly growing Li-battery industry needed for the electrification of automobiles. This has led to an increase in the production of sodium sulfate as a waste effluent that needs to be processed to meet discharge guidelines. Using bipolar membrane electrodialysis (BPED), acids and bases can be effectively produced from corresponding salts found in these waste effluents. However, the efficiency and environmental sustainability of the overall BPED process depends upon several factors, including the properties of the ion exchange membranes employed, effluent type, and temperature which affects the viscosity and conductivity of feed effluent, and the overpotentials. This work focuses on the recycling of Na2SO4 rich waste effluent, through a feed and bleed BPED process. A high ion-exchange capacity and ionic conductivity with excellent stability up to 41 degrees C is observed during the proposed BPED process, with this temperature increase also leading to improved current efficiency. Five and ten repeating units were tested to determine the effect on BPED stack performance, as well as the effect of temperature and current density on the stack voltage and current efficiency. Furthermore, the concentration and maximum purity (>96.5%) of the products were determined. Using the experimental data, both the capital expense (CAPEX) and operating expense (OPEX) for a theoretical plant capacity of 100 m(3) h(-1) of Na2SO4 at 110 g L-1 was calculated, yielding CAPEX values of 20 M EUR, and OPEX at 14.2 M EUR/year with a payback time of 11 years, however, the payback time is sensitive to chemical and electricity prices.
Control-Oriented Electrochemical Model and Parameter Estimation for an All-Copper Redox Flow Battery
(2023-05-15) Badenhorst, Wouter; Jensen, Christian M.; Jacobsen, Uffe; Estafani, Zahra; Murtomäki, Lasse
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Redox flow batteries are an emergent technology in the field of energy storage for power grids with high renewable generator penetration. The copper redox flow battery (CuRFB) could play a significant role in the future of electrochemical energy storage systems due to the numerous advantages of its all-copper chemistry. Furthermore, like the more mature vanadium RFB technology, CuRFBs have the ability to independently scale power and capacity while displaying very fast response times that make the technology attractive for a variety of grid-supporting applications. As with most batteries, the efficient operation of a CuRFB is dependent on high-quality control of both the charging and discharging process. In RFBs, this is typically complicated by highly nonlinear behaviour, particularly at either extreme of the state of charge. Therefore, the focus of this paper is the development and validation of a first-principle, control-appropriate model of the CuRFBs electrochemistry that includes the impact of the flow,charging current, and capacity fading due to diffusion and subsequent comproportionation. Parameters for the proposed model are identified using a genetic algorithm, and the proposed model is validated along with its identified parameters using data obtained from a single-cell CuRFB flow battery as well as a simpler diffusion cell design. The proposed model yields good qualitative fits to experimental data and physically plausible concentration estimates and appears able to quantify the long-term state of health due to changes in the diffusion coefficient.
Evaluating the fabrication and performance of sulfonated biochar composite membranes for copper redox flow battery
(2024-03-12) Syväniemi, Sakari
Kemian tekniikan korkeakoulu | Master's thesis
The combined doubling of global energy requirements and pressure of climate emergency requires the large scale adoption and integration of energy storage with renewable energy sources. Redox flow batteries (RFBs) are increasingly considered a key technology in enabling the energy transition due to its scalability, competitive long-term cost, and installation flexibility. Furthermore, recent developments in alternative RFB chemistries, such as with the hybrid all-copper system, have allowed for further sustainable opportunities in electrolyte sourcing, and materials development. However, both the significant cost of high performance membranes and the EU's planned restriction of per-polyfluoroalkyl substances including Nafion membranes currently hinder RFB adoption. Thus, biochar, was investigated as a sustainable membrane additive for application in copper redox flow battery (CuRFB). Derived from D(-)-fructose by pyrolysis, biochar samples were sulfonated for a range of hours before addition to sulfonated poly (ether ether ketone) (SPEEK) casting solutions and drop cast on SF601 porous separators. The resulting sBiochar composite membranes were characterised by IR, IEC, TEM, SEM and EIS. All sBiochar membranes showed increased current efficiency during 25 mAcm-2 single cell cycling by approximately 5 and 10% from sPEEK and SF601 respectively. Furthermore, selected sBiochar membranes showed an average increase in maximum discharge power by 8\% and significant improvements in self-discharge time and capacity decay. It is suggested that these increases are due to the high ion conducting surface area and additional hindrance of copper species by sulfate groups provided by the sbiochar. Considering these improvements the novel sBiochar membranes fabricated in this work are proposed as a viable inexpensive candidate for electrochemical reactors requiring high selectivity and superior ion exchange capacity.
Short thermal treatment of carbon felts for copper-based redox flow batteries
(2022-02-01) Faggiano, Luigi; Lacarbonara, Gianluca; Badenhorst, Wouter; Murtomäki, Lasse; Sanz Rubio, Laura; Arbizzani, Catia
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Carbon felts are often used as electrode materials for various redox flow batteries (RFBs), and for optimal performance it is often required for them to be subjected to extended thermal treatment processes (25–30 h). However, the Cu(II)/Cu(I) redox couple employed in the copper RFB, at the positive electrode is significantly different when compared to the vanadium alternative. For this reason, the effect and duration of thermal treatment of the carbon felt on the performance of the copper-based RFB has to be determined. Both polyacrylonitrile and rayon carbon felts were subjected to thermal treatment for 6 and 25 h at 400 °C. The treated carbon felts were subsequently analysed using thermogravimetric analysis, resistivity determination, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Additionally, the effect of the thermal treatment was also determined using electrochemical testing and in a redox flow cell.
Unexpected Behavior of Streaming Potential in Ion-Exchange Membranes
(2024-04-09) Badenhorst, Wouter; Kuldeep; Manzanares, Jose Antonio; Murtomäki, Lasse
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Streaming potential is one of the numerous electrokinetic phenomena created when an electrolyte flows along a charged surface. In membranes, applying the charged cylindrical pore model, streaming potential can be used to estimate, e.g., the pore size and the charge density of such pores. In this study, we are extending streaming potential experiments to ion-exchange membranes (IEMs) and trying to verify the existing models with the measurements. According to the Donnan equilibrium between an electrolyte solution and an IEM, the solution concentration should not affect the streaming potential if the membrane charge is even moderately low. Yet, the streaming potential varied substantially with the solution concentration, as in the case of nearly neutral porous membranes. In addition, the existing theory does not include the membrane thickness, but we found that thinner membranes showed larger streaming potentials. These dilemmas are discussed in this paper.