Irena Korus

In accordance with the Circular Economy, the metallurgical solid wastes are considered secondary resources of many heavy metals, such as lead, zinc, iron, cadmium, thallium, and others. To separate valuable and toxic metals, numerous processes, among them solid–liquid extraction, have been studied in recent years. In line with this trend, the objective of this study was to investigate the possibility of leaching selected heavy metals (Pb, Zn, Cu, and Fe) from slag generated by the zinc and lead metallurgical industry. The effect of the leaching agent type (HCl, NaOH, and Na₂NTA) and concentration, pH, solid-to-liquid (S/L) ratio, and interphase contact time on process efficiency was evaluated experimentally. The slag was comprehensively characterized using atomic absorption spectrometry (AAS), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and BCR (Community Bureau of Reference) sequential extraction to determine the total metal concentration, element and phase composition, as well as chemical speciation of the investigated metals. To determine the kinetic mechanisms the Weber–Morris and shrinking-core models were used. The efficiency of metal separation from slag strongly depended on the process parameters. HCl was highly effective for simultaneous metal leaching, particularly Pb, Zn, and Cu (up to over 80%), while NaOH and Na₂NTA allowed for the selective separation of Pb with leaching efficiencies of up to 80% and 90%, respectively. Sequential BCR analysis confirmed the different forms of metal occurrence, with predominating highly mobile Pb fractions and stable, residual Cu and Fe fractions. Comparative analyses using SEM and sequential BCR extraction revealed significant changes in slag morphology and metal speciation following leaching with the HCl solution. The Weber and Morris model indicated the kinetic contribution of the intraparticle diffusion within the slag’s porous structure, especially under HCl-based leaching. An analysis using shrinking-core models revealed different predominant mechanisms for specific metal–leaching agent systems.

Two types of magnetite nanoparticles: unmodified (Fe₃O₄ NPs), and modified with poly(sodium acrylate) (Fe₃O₄/PSA NPs) were synthesized by the co-precipitation method and characterized using different techniques: X-ray diffraction (XRD), transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), Brunauer–Emmett–Teller (BET) adsorption, Fourier-transform infrared spectroscopy (FTIR). Additionally, magnetic properties and the effect of pH on the zeta potential were analyzed for both types of nanoparticles. Magnetites were used as adsorbents for seven heavy metal ions (Zn(II), Cu(II), Ni(II), Cd(II), Pb(II), Cr(III), Cr(VI)) within the pH range of 3–7. Research revealed nanometric particle sizes, a specific surface area of 140–145 m²/g, and superparamagnetic properties of both tested materials. Moreover, the presence of PSA functional groups in modified magnetite was confirmed, which lowered the pH of the isoelectric point. Both types of magnetite were effective metal ion adsorbents, with metal cations more effectively removed on Fe₃O₄/PSA NPs and Cr(VI) anions on Fe₃O₄ NPs. The adsorption of most of the examined cations (performed at pH = 5) can be well described by the Langmuir isotherm model, whereas the adsorption of Cr(VI) ions on modified magnetite correlated better with the Freundlich model. The Dubinin–Radushkevich model confirmed that chemisorption is the predominant process. The adsorption of all metal ions was well-characterized by the pseudo-second-order kinetic model.

Colored industrial wastewater is a threat in many environmental aspects. As such, there is a need to find more effective methods for its purification. This article presents a brief overview of available methods for removing dyes from aqueous solutions, among them the adsorption process, which is the subject of this study. The course of preliminary tests on the process of cleaning dye solutions in the adsorption process is presented. Unmodified magnetite and magnetite modified with polymers were used as adsorbents. The synthesis of particular types of magnetite, the adsorption process, as well as the methods of further analyzes are described. As part of the work, the focus was put on a comparison of the effectiveness of the purification process for different types of adsorbents in relation to selected dyes. The varied conditions of the process were also analyzed. It has been shown that magnetite is an adsorbent that is easy to use, allowing effective separation of dyes of various chemical structures from aqueous solutions. The effectiveness of the process depends on the type of dye and on the pH value and can be increased in relation to some dyes by using magnetite modification with selected polymers.

Polymer-enhanced ultrafiltration is an effective separation technique which enables heavy metal ions removal from aqueous solutions. In this work, a water soluble polymer containing carboxylic groups and poly(sodium acrylate) (PSA), was used to enhance the separation of Cu(II) ions during ultrafiltration. The UV spectrophotometric analysis of the solutions containing PSA and Cu(II) ions revealed an absorption band with its maximum at a wavelength of 255 nm. The methods of continuous variations (Job’s method) and molar ratio were employed to assess the stoichiometry of PSA–Cu(II) complexes formed. The molar ratio of PSA repeat unit to Cu(II) ion was evaluated to be ca. 2.8–2.9. The effect of the polymer—metal concentration ratio, solution pH, and the presence of anions: , , , , as well as a complexing agent (EDTA) on copper ions separation was investigated. The study revealed a good compatibility of spectrophotometric analysis and the ultrafiltration results.