S.T. Abrahami | TU Delft Repository

Electrochemically Driven Hydrometallurgical Purification of Li-ion Battery Waste

Master thesis (2025) - M.A. Anghel (author) , S. T. Abrahami (mentor) , J.J.M.M. van de Ven (mentor) , Y Gonzalez-Garcia (graduation committee member)

The increasing electrification of our world drives a demand for energy storage solutions, especially for electric vehicles. As they reach their end of life, recycling them becomes vital to recover the critical raw materials in these batteries. However, traditional recycling route ...

Additive Manufacturing of Recyclable Multiple-Materials

Master thesis (2025) - A.J. Naindraputra (author) , ST Abrahami (mentor) , Marcel Hermans (graduation committee member) , Mehrshad Mehrpouya (graduation committee member)

This study investigates the effect of repeated recycling processes on the properties of PLA matrix 3D printed filaments mixed with 20 wt.% Fe₃O₄ magnetic particles. The recycling process of the composite was simulated by using extrusion and manual cutting to achieve multiple clos ...

This study investigates the effect of repeated recycling processes on the properties of PLA matrix 3D printed filaments mixed with 20 wt.% Fe₃O₄ magnetic particles. The recycling process of the composite was simulated by using extrusion and manual cutting to achieve multiple closed-loop recycling processes. The research studied the 1st, 3rd, 5th, and 6th cycles, while the initial batch virgin materials (0 cycles) was used as a baseline.

Visual observations revealed that surface defects increase with each cycle, along with diameter inconsistencies and brittleness. The analysis showed that the 5th cycle had the highest diameter variation (range = 2.37 mm, standard deviation = 0.44 mm). The 6th cycle was unusable filament with a disoriented shape and chaotic flow behavior, which made it impossible to inject or print into the 3D printing machine. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis indicated significant morphological changes, agglomeration of magnetic particles, and content reduction along cycles. GPC analysis confirmed that the molecular weight of the PLA decreased and that the polydispersity increased, while NMR identified the absence of dichloromethane as a solvent, confirming that the degradation indicated by PLA molecular weight reduction was solely caused by thermomechanical reprocessing effects.

The findings suggest that PLA/Fe₃O₄ filaments can be processed up to five times, but the practical usability of the reprocessed filament is limited due to surface defects and poor filament diameter consistency. During the first cycle, the filament frequently stuck in the 3D printer feeder due to diameter inconsistencies, and by the third cycle, attempts to print resulted in improperly shaped parts, highlighting significant processing challenges. Additionally, repeated processing cycles lead to loss of magnetic particles, significantly affecting the filament’s functionality. Characterization using the Vibrating Sample Magnetometer (VSM) demonstrates a reduction in magnetic properties, with a 28.62% decrease in Cycle 3, a 51.41% decrease in Cycle 5, and a 73.91% decrease in Cycle 6 compared to Cycle 1. Moreover, the thermal stability of PLA is also compromised, as evidenced by the decrease in degradation temperature recorded in the Thermogravimetric Analysis (TGA), highlighting the declining performance of the filament after multiple recycling cycles. Further improvements in processing methods, material quality, and testing are recommended to enhance recyclability and ensure consistent print results in future applications.

Analysis of by-products and systematic variation of process parameters in the electrochemical recycling of CFRP composites

Master thesis (2025) - R. Baldacchino (author) , ST Abrahami (mentor) , E. Best (mentor) , P. Taheri (graduation committee member) , J. W. Haverkort (graduation committee member)

Carbon fibre reinforced polymer (CFRP) composites have become integral to modern day society, forming the backbone of lightweight, high performance structures in aerospace, renewable energy and automotive applications amongst other. Their exceptional strength-to-weight ratio, sti ...

Carbon fibre reinforced polymer (CFRP) composites have become integral to modern day society, forming the backbone of lightweight, high performance structures in aerospace, renewable energy and automotive applications amongst other. Their exceptional strength-to-weight ratio, stiffness and corrosion resistance in such applications make them indispensable for improving fuel efficiency, thereby contributing to lower greenhouse gas emissions. However, their end-of-life management and recycling remains a critical challenge. The thermoset polymer matrix used in most high-performance CFRP composites, makes fibre-matrix separation difficult leading to limited recyclability and continues reliance on energy- and cost- intensive virgin carbon fibre production.

Among the emerging approaches for CFRP recycling, electrochemical processes have gained attention as promising low-energy and environmentally friendly alternatives to traditional thermal or chemical processes. The electrochemical recycling of CFRP operates under mild conditions, without the need of hazardous solvents or external heating. Despite these advantages, current literature focuses predominantly on fibre recovery efficiency with limited understanding of the gaseous, liquid and solid by-products formed during such process. These by-products may significantly influence the true environmental footprint and industrial feasibility of this technique.

To address this gap, this study systematically investigated the influence of constant applied voltage (4, 6 and 8 V) on by-product generation and CFRP degradation behaviour in an alkaline saline electrolyte composed of 3wt.% NaCl and 0.01M KOH. The by-products were characterised using gas chromatography and proton nuclear magnetic resonance spectroscopy. Additionally, the pH of the electrolytes after electrolysis was monitored and surface analysis techniques were employed to evaluate the degradation mechanisms and fibre integrity.

Results revealed that higher voltages increase current density, gas evolution and epoxy degradation, but also produced greater quantities of CO2, hydrocarbons and liquid by-products, alongside visible fibre damage. Conversely, lower voltages achieved sufficient resin removal while maintaining fibre integrity and reducing emissions. Liquid-phase analysis identified ethanol, acetone and formate, whose decomposition correlated with increasing CO2 evolution at higher potentials.

Metal oxide materials for solid-state fluoride ion batteries

Master thesis (2024) - L. Peng (author) , P. Groszewicz (mentor) , S. T. Abrahami (mentor) , Amarante Bottger (graduation committee member)

This study explores the potential of metal oxide fluorides as cathode materials for solid-state fluoride-ion batteries (FIBs), aiming to combine the stability of intercalation-based electrode materials with the high energy density of conversion-based materials. Through comprehens ...

Electroleaching of NdFeB Matrix from Spent Permanent Magnets in Organic Acids

Student report (2023) - J. Li (author) , S.T. Abrahami (mentor)

Neodymium (Nd) recycling plays a significant role in rare earth elements (REEs) reproduction and spent neodymium-iron-boron (NdFeB) permanent magnets is a crucial resource for Nd. This study aims at investigating the anodic behaviour and dissolution properties of NdFeB magnets du ...

Neodymium (Nd) recycling plays a significant role in rare earth elements (REEs) reproduction and spent neodymium-iron-boron (NdFeB) permanent magnets is a crucial resource for Nd. This study aims at investigating the anodic behaviour and dissolution properties of NdFeB magnets during electroleaching in four biodegradable organic acids to indicate a suitable environmentally friendly and safe reagent that promotes electroleaching. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) characterization revealed that the metallic coating of the magnet was made of zinc. SEM-EDS analysis of polished sample surface showed the Nd-rich phases were surrounded by the matrix. Then open circuit potential (OCP) and linear scanning voltammetry (LSV) measurements were carried out to study the anodic behaviour of NdFeB. The comparison among the four organic acids at 1 M resulted in that citric acid and tartaric acid achieved the highest corrosion current with least negative OCP, as they have more carboxylic groups and higher acidities, while the lower OCP of formic acid compared to acetic acid which shows the lowest acidity revealed that the chemical leaching properties are not only dominated by acidity. But the higher corrosion current density of formic acid stated that the external potential reduced the influence of the factors other than acidity. Next, citric acid and formic acid were selected for studying the impact of concentration on anodic behaviours for their high corrosion current density and low price. Along the test that monitored the concentrations, 0.25 M citric acid was selected as the desired electrolyte for the higher corrosion current density compared to all groups of formic acid and low difference between citric acid at higher concentrations. The chronopotentiometry experiment for observing the influence of applied current density on the dissolved mass of NdFeB was failed to carry out due to the limited voltage range of the potentiostat. SEM-EDS characterization displayed that the NdFeB matrix formed a rough and porous surface after electroleaching, and the increase in test time and acid concentration promotes dissolution. The semi-quantitative composition analysis showed good dissolution properties of Nd-rich phases and praseodymium (Pr) when undergoing electroleaching in citric acid.

Thermal Actuation of Phase Change Tin Pump

Master thesis (2023) - N. RAMACHANDRAN (author) , Siddhant Kumar (graduation committee member) , Luis Cutz IJchajchal (coach) , ST Abrahami (coach) , Michiel de Rapper (mentor)

Pressurized liquid Tin finds application in the generation of Extreme Ultra-Violet light for semiconductor lithography. In order to improve the throughput of the lithography systems, tin must be pressurized to higher levels, and in turn, new pressurization methods are needed.

Pressurized liquid Tin finds application in the generation of Extreme Ultra-Violet light for semiconductor lithography. In order to improve the throughput of the lithography systems, tin must be pressurized to higher levels, and in turn, new pressurization methods are needed.

A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.

Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.

Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.

Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat.

Compatibilization of polyethylene (waste) mixtures through reactive extrusion

Master thesis (2023) - A.R.N. Bussemakers (author) , S.T. Abrahami (mentor)

The production of plastic materials has experienced incredible growth over the past decades. Polyethylene constitutes the largest part (25%) of plastic production, finding its application mostly as film in industrial and food packaging and agricultural use. However, since packagi ...

The production of plastic materials has experienced incredible growth over the past decades. Polyethylene constitutes the largest part (25%) of plastic production, finding its application mostly as film in industrial and food packaging and agricultural use. However, since packaging materials are getting increasingly complex, polyethylene waste is nearly always mixed with other polymers, making direct recycling impossible. Compatibilization of polymer blends can be used to convert an immiscible polymer blend into a homogeneous material with synergistic properties. When this compatibilization is carried out inside an extruder, one less reaction step is needed and the material can directly be processed according to its application.

This study addresses the reactive compatibilization of recycled LDPE (rLDPE) originating from industrial film waste with its polymer impurities, as well as virgin low-density polyethylene (LDPE)/polyamide 6 (PA6) blends of various compositions through reactive extrusion with PE grafted with MA (PE-g-MA). A literature review was carried out, summarising the current state-of-the-art of reactive compatibilization and reactive extrusion. The composition of the recycled stream was identified through various characterisation methods. Through a wide variety of characterisation techniques, the mechanical properties of the extruded sample pellets were investigated, as well as the mechanical and optical properties of the blown film.

The compatibilizing effect on the virgin LDPE/PA6 blends was found to grow in importance with increasing PA6 content. For 1 wt%, the samples did not exhibit any improvement upon compatibilization. The samples containing 5 wt% showed their improvements predominantly in the optical properties. The 10 wt% samples showed large enhancements overall, after being treated with the compatibilizer. Both the optical and mechanical properties of rLDPE saw a significant amelioration as a result of compatibilization. This study thus achieved compatibilization through reactive extrusion for an extensive variety of polymer samples.

Recycling permanent magnets from offshore wind turbines

An e-waste approach

Master thesis (2022) - F.F. de Waal (author) , ST Abrahami (mentor) , Marin van Regteren (mentor) , Jonas P. Jensen (mentor)

OWTs and WEEEs have both been found to contain NdFeB permanent magnets, which are both valuable sources for the recovery of REEs. At the same time, OWTs have been found to contain many electrical components that may not officially fall under the WEEE direct but share many similar ...

OWTs and WEEEs have both been found to contain NdFeB permanent magnets, which are both valuable sources for the recovery of REEs. At the same time, OWTs have been found to contain many electrical components that may not officially fall under the WEEE direct but share many similarities with WEEE. While there is little known about the recycling of OWTs and their electrical components due to their recent introduction, the recycling of WEEE has been studied more extensively and is a more mature industry.

To determine the preferred recycling route for permanent magnets from OWTs, a comparison was made with the characteristics and the recycling routes of permanent magnets from WEEE. The disassembly was found to be the most critical part to enable an efficient recycling process, leading to the objective of how can permanent magnets be disassembled from OWT generators. It was found that the disassembly of magnetised magnets at the scale of OWTs is challenging due to the forces required to move them and the brittleness of the materials. For efficient disassembly, the permanent magnets need to be locally and thermally demagnetised. Through a series of interviews, desk research, a lab visit and a site visit to Cuxhaven a concept for the disassembly of permanent magnets from OWTs was developed.

It was found that induction heating a copper coil wrapped around U shaped core to transfer heat to the permanent magnet via conduction is a potential scalable, automatable and time-efficient solution for demagnetisation. The power required to heat the coil depended predominantly on the time taken to heat the core as well as the contact surface area of the core with the permanent magnet, the mass of the conductor and the material chosen for the conductor. After thermal demagnetisation, the magnet can be removed while the magnetic is still hot or after cooling, dependent on the thermal expansion coefficient, effect of re-magnetisation and remanence of the magnet. Depending on the acceptable remanence to be able to handle the magnet, it may not be necessary to heat the magnet up all the way to the Curie temperature. The solution proposed in this study is just one of many options towards the recycling of permanent magnets, thus alternative solutions such as direct induction of complete thermal demagnetisation should also be considered.