Papers by Karl C Vrancken
Hydrometallurgy, 2015
Abstract Selective chromium (Cr) leaching from stainless steel slag (SS slag) by alkali roasting ... more Abstract Selective chromium (Cr) leaching from stainless steel slag (SS slag) by alkali roasting followed by water leaching was investigated. The efficiency of the alkali roasting process for Cr leaching was increased by optimizing the mass ratio of alkaline agents (NaOH, and NaOH–NaNO 3 ) to the slag, roasting temperature and time. At the optimum condition (0.67 mass ratio of NaOH to SS slag, 400 °C, 2 h) of NaOH roasting, chromium leaching was around 83%, while the matrix material was dissolved only to a limited extent (Si 8.0%). Mechanical activation of the SS slag prior to roasting reduced the optimum NaOH to SS slag mass ratio to 0.4. The addition of NaNO 3 as an oxidant to the NaOH salt increased Cr leaching to 89% after roasting at 400 °C for 2 h. The remaining Cr phases in the residue were almost exclusively FeCr alloys. Further chromium dissolution from these alloys is prevented by a passivation layer of Fe oxides as shown by SEM/EDS images. Based on these results, a SS slag recycling process is suggested in which roasting–water leaching followed by water washing to remove Cr yields a residue which has potential for application as a construction material.
Proceedings of Entropy 2021: The Scientific Tool of the 21st Century, 2021
Resources, Conservation and Recycling
The COVID-19 pandemic had large repercussions for our economy and organizations. Improved resilie... more The COVID-19 pandemic had large repercussions for our economy and organizations. Improved resilience can give organizations the ability to withstand crises and build back better and faster. This article assesses resilience of organizations and sole proprietorships in the context of the COVID-19 pandemic with eight circular strategies as explanatory variables. Furthermore, these eight circular strategies are also used to assess the organizations' and sole proprietorships' resilience outside of the COVID-19 pandemic. This analysis is conducted to explain how circular strategies can help companies and sole proprietorships maintain stability. The analysis was performed by means of a survey conducted between May and June 2020 in Flanders (Belgium), using a sample of 542 respondents. After performing a regression analysis combined with expert opinions collected through interviews, we find that companies and sole proprietorships with a higher circularity score have a significantly higher resilience score during crises and during normal times, compared to less circular companies. Furthermore, we find that the size of the company does not matter during a crisis to adapt and react flexibly, while it is important when there is no crisis. Finally, we argue that it is the combination of different circular strategies which yields to the highest results for the organizations' resilience and we provide policy recommendations based on the most asked support measures.
Proceedings of Entropy 2021: The Scientific Tool of the 21st Century, 2021
Chemical Engineering Journal, 2016
Hydrometallurgy, 2017
Two routes were investigated to selectively recover lead and minor metals (Cu, Ni, Zn) from a sul... more Two routes were investigated to selectively recover lead and minor metals (Cu, Ni, Zn) from a sulfide-rich lead smelter residue, matte. The first route comprises a two-step leaching process that combines Fe(III)-HNO 3 leaching with roasting, followed by water leaching. In the first step, the efficiency of Pb leaching was 90% at the optimum condition (L/S ratio 8, 0.5 mol⋅ L − 1 HNO 3 , 0.15 mol ⋅ L − 1 Fe(III), 25°C). In the second step, roasting at 600°C followed by water leaching at 50°C selectively leached Ni, Cu, and Zn while fully converting iron sulfides to oxides. One-step oxidative pressure leaching in HNO 3 was investigated as an alternative to simultaneously leach Pb, Cu, Ni and Zn. At the optimal conditions (130°C, 60 min, 0.3 mol ⋅L − 1 HNO 3 , 0.07 mol⋅ L − 1 Fe(III), L/ S ratio 20), Pb, Cu, Zn and Ni leaching were 92, 60, 70 and 66%, respectively, while Fe leaching remained low (2%). The leachates obtained from both leaching routes were treated by ion-exchange adsorption with diethylenetriaminepentaacetic acid (DTPA) functionalized chitosan-silica hybrid materials to investigate the selective recovery of Cu, Zn and Ni. The adsorption order appeared to be in the same order as the corresponding stability constants for complexes between the respective metal ions and free DTPA: Ca(II) < Zn(II) < Pb (II) ≈ Ni(II) < Cu(II). This allows not only to selectively recover Cu, Zn and Ni from the leachates, but also to mutually separate them by using the functionalized resin as a stationary phase in column chromatography. To avoid adsorbent contamination, Fe(III) and Pb(II) may be removed from the leachates in a pre-treatment step. Based on these results, the investigated methods can be combined as process steps of two possible routes for the selective recovery of valuable metals from the studied secondary lead smelting residue. The two-step leaching process seems to be superior since a more concentrated solution of Cu, Ni, and Zn is produced in the 2nd leaching step with low capital cost.
Governments and co-operations are aware of the fact that more sustainable consumption and product... more Governments and co-operations are aware of the fact that more sustainable consumption and production practices are required. Efforts are being made to produce less waste while increasing the recycling ratio. Concurrently, it is of importance to place landfilling in a sustainable context. The present paper discusses a novel concept where a landfill is no longer considered as a final solution but rather as a ‘temporary storage place, awaiting future valorisation’. Enhanced Landfill Mining (ELFM) offers the opportunity to select the most suitable moment to recycle certain waste streams, depending for instance on the state of the technology. Recently, a transdisciplinary consortium was established. The first, embryonic elements of this new vision are presented in this paper. To make matters more tangible, the ‘Closing the Circle’ case-study is used to illustrate the ELFM concept. The economics are influenced by technical and society driven parameters. In order to successfully transitionise this novel view on waste management, a multi-actor approach is of paramount importance.
Resources, Conservation and Recycling, 2021
looped back in the economy and seem less apt for assessing the circularity of biological cycles. ... more looped back in the economy and seem less apt for assessing the circularity of biological cycles. 2. Characteristics of biological cycles, that distinguish them from technical cycles, are their renewability, potential use in cascading, closing the biological nutrient loop, and the environmental impact of biotic resources depletion, land-use and biogenic carbon flows. 3. These characteristics need to be added to CE monitoring criteria, to ensure the sustainable and circular use of natural resources.
Resources, Conservation and Recycling, 2019
The increasing focus on circular economy at the level of governments and policy requires the deve... more The increasing focus on circular economy at the level of governments and policy requires the development of appropriate indicators to effectively monitor the progress towards the circular economy. Currently two very different types of indicator areas are under development: (i) monitoring frameworks based on macro indicators that summarize the progress at (supra)national level, and (ii) micro indicators tailored towards assessing circularity at the level of products. It is not possible to obtain sufficiently direct feedback about the impact of policy interventions by either macro or micro indicators alone. In this paper, a conceptual approach is developed that aims to bridge the gap between the micro and macro level with meso level indicators, and thus ultimately deliver more direct feedback for policymakers, via the insertion of an extra level of meso indicators in between the macro and the micro level. These indicators have been extracted from a dedicated workshop that involved policy, sector and societal stakeholders. The aim of these indicators is to report on progress towards circular economy objectives based on the fulfillment of societal needs. In this way the consumption perspective is given a central position, and the role of circular business models is acknowledged. Following the development of the concept, the next steps towards tailored, flexible and agile monitoring frameworks for circular economy at (supra)national and regional level are outlined. The paper concludes with an illustrative example of the framework applied to the mobility system.
Journal of Cleaner Production, 2016
This study focuses on the recycling of stainless steel (SS) slags containing about 1.2 wt% of chr... more This study focuses on the recycling of stainless steel (SS) slags containing about 1.2 wt% of chromium (Cr). The selective recovery of Cr from SS slag by a hydrometallurgical method (alkaline pressure leaching) was investigated. Leaching experiments were carried out based on 2 4-1 factorial design of experiment (DOE) with the following parameters: NaOH concentration, temperature, leaching time, and mechanical activation (MA). Results show that temperature and MA are the most influencing factors for an enhanced Cr leaching. The maximum Cr leaching was 46% at 1 M NaOH, 240 o C, 6 h, MA 30 min, while the matrix material was dissolved only to a limited extent (Al 2.88%, Si 0.12%, Ca 0.05%). After Cr leaching followed by alkali washing, a carbonation treatment is proposed to stabilise the remaining Cr in the matrix material and make the subsequent recycling of the matrix material as a construction material possible. 10 Chromium can be recovered from the leachate and alkali/water washing solution by ion exchange or precipitation.
Theories, Concepts and Industrial Examples for Achieving Sustainable Chemical Products and Processes from a Non-Technological Viewpoint, 2013
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Papers by Karl C Vrancken