POME is an excellent cultivation medium for the production of microalgae because it includes high macro and micronutrients. Nevertheless, microalga cultivation is laborious to maintain under outdoor condition. The aim of this reseasch was to evaluate the potency of co-cultivation strategy to improve growth and lipid production of mixed algae when growing on POME under dynamic outdoor condition. Cultivation was done in outdoor condition by comparing synthetic medium and POME medium, and optimizing the enviromental and nutritional conditions by using Box-behnken response surface methodology (RSM). Results showed that high growth rate (0.35/d) and lipid (40%) were achieved when 75% POME fraction, 30 PSU salinity, and 450 mg/L urea were used. The increasing POME fraction and urea addition enhanced SFA formation to MUFA and PUFA in the fatty acid profiles. We conclude that co-cultivation strategy on POME could promote growth rate and lipid production of mixed algae under outdoor condition.

In an ongoing effort towards a more sustainable rare-earth element market, there is a high potential for an efficient recycling of rare-earth elements from end-of-life compact fluorescent lamps by physical separation of the individual phosphors. In this study, we investigate the separation of five fluorescent lamp particles by high-gradient magnetic separation in a rotary permanent magnet separator. We thoroughly characterize the phosphors by ICP-MS, laser diffraction analysis, gas displacement pycnometry, surface area analysis, SQUID-VSM, and Time-Resolved Laser-Induced Fluorescence Spectroscopy. We present a fast and reliable quantification method for mixtures of the investigated phosphors, based on a combination of Time-Resolved Laser-Induced Fluorescence Spectroscopy and parallel factor analysis. With this method, we were able to monitor each phosphors’ removal dynamics in the high-gradient magnetic separator and we estimate that the particles’ removal efficiencies are proportional to (d²·χ)^1/3. Finally, we have found that the removed phosphors can readily be recovered easily from the separation cell by backwashing with an intermittent air–water flow. This work should contribute to a better understanding of the phosphors’ separability by high-gradient magnetic separation and can simultaneously be considered to be an important preparation for an upscalable separation process with (bio)functionalized superparamagnetic carriers.

Magnetic separation has wide-ranging applications in both mineral processing and recycling industries. Nevertheless, its conventional utilization often overlooks the interplay between mineral and particle characteristics and their impact on operational conditions, ultimately influencing the efficacy of the separation process. This work describes a methodology able to achieve the comprehensive characterization and classification of Waste Electrical and Electronic Equipment (WEEE) slag. The primary objective is to establish a meaningful connection between the distinct properties of slag phases and their influence on the separation process. Our methodology consists of several stages. Firstly, the WEEE slag is sieved into distinct size classes, followed by classification into magnetic susceptibility classes by using the Frantz Isodynamic separator. To quantify the magnetic susceptibility of each class, we used a magnetic susceptibility balance, and to identify paramagnetic and ferromagnetic fractions and phases within these magnetic susceptibility classes, we conducted vibrating-sample magnetometer measurements. Finally, to establish a meaningful link between the magnetic characterization, mineralogical, and particle-level details, Mineral Liberation Analysis was conducted for each magnetic susceptibility class. This in-depth analysis, encompassing both particle properties and magnetic susceptibility classes, provides a better understanding of the separation behavior of different phases and can help to enrich phases with a specific range of magnetic susceptibility values. This knowledge advances progress towards the development of predictive separation models that are capable of bridging the gap between theoretical understanding and practical application in the field of magnetic separation.

Due to their complex structure and high metal content, printed circuit boards (PCBs) represent both a major challenge and opportunity for recycling. By weight, copper represents the main metallic fraction of PCBs. Thus, the selective removal and recovery of high purity copper is crucial for efficient recycling, in addition to the extraction of minor, precious metal components, such as gold, silver and palladium. This paper presents an integrated study of detailed characterization, process development and the environmental impact of copper recycling from virgin PCBs using hydrometallurgical approaches – rather than the well-established pyrometallurgical route. Thorough mineral liberation analysis helped us to understand specific processing and metallurgy approaches depending on access possibilities of the target metals phases. Near quantitative copper leaching was achieved with H₂SO₄/H₂O₂ and HNO₃, whereas heterotrophic bioleaching with citric acid and polyglutamic acid resulted in 98% of the leached copper was selectively transferred to the organic phase by solvent extraction with a LIX 84-I-kerosene//CuSO₄-H₂SO₄ system. With the exception of Ni(II), co-extraction of further metal ions was not detected. Subsequently, up to 98% of copper was recovered from the organic phase via stripping with a model electrolyte of copper (II) sulfate in H₂SO₄. From the enriched electrolyte solutions, metallic copper with a purity of 99.64% - 99.84% was electrodeposited on stainless steel cathode with a current efficiency of 98.66% - 99.85% -. Residual copper obtained by washing the leaching residue was recovered by cementation with an iron powder according to a stoichiometric ratio of Fe/Cu²⁺ of 1.5:1. According to life cycle assessment, based on the energy and chemical consumption of the copper recycling process, the global warming potential of the tested approaches lies in the range 13.0 kg CO2 eq./(kg Cu) - 40.3 kg CO2 eq./(kg Cu). The highest contributions to environmental impact come from the leaching and solvent extraction processes, which can be substantially improved by working on a larger scale and by recycling of process ingredients. The proposed approach demonstrates end-to-end high purity metal recovery with direct application to different circuit boards and copper-rich electronic components.

Printed circuit boards represent an extraordinarily challenging fraction for the recycling of waste electric and electronic equipment. Due to the closely interlinked structure of the composing materials, the selective recycling of copper and closely associated precious metals from this composite material is compromised by losses during mechanical pre-processing. This problem could partially be overcome by a better understanding of the influence of particle size and shape on the recovery of finely comminuted and well-liberated metal particles during mechanical separation. Here, we propose a workflow to quantify the role of the size and shape of such particles in various separation processes. As a case study, we compare an analytical heavy liquid separation to a new type of eddy current separator. Using X-ray computed tomography, we were able to distinguish metallic and non-metallic phases and determine the size and 3D microstructure of individual particles. For both separation processes, we trained a particle-based separation model that predicts the probability of individual particles to end up in the processing products. In particular, elongated particles were found to display a negative correlation between particle size and sphericity of metallic particles. In line with this correlation, the predicted metal recoveries are positively correlated with particle size but negatively correlated with sphericity in both separation processes. The suggested workflow is easily transferred to other recycling material systems. It allows to quantify the role of 3D geometrical particle properties in separation processes and provide robust predictions for the recoverability of different raw materials in complex recycling streams.