The Cu(II), Cd(II), Zn(II), and Pb(II) sorption kinetics and equilibrium on hybrid material, composed of pectin and titanium dioxide nanopowder, were examined. Parameters, such as pH and adsorbent dose, were also investigated. The experimental data were better described by the Langmuir model. The maximum adsorption capacities were 1.37, 0.68, 0.51, and 0.83 mmol/g for Cu(II), Cd(II), Zn(II), and Pb(II), respectively. The introduction of nano-TiO₂ improved the kinetics of the metal ion sorption. The titanium dioxide, despite its small content (6%), contributes to the removal of the examined metal ions and eventually to the adsorption capacity of hybrid beads.

The need to identify secondary sources of REEs and their recovery has led to the search for new methods and materials. In this study, a novel type of ion-imprinted adsorption membranes based on modified chitosan was synthesized. Their application for the recovery of chosen REEs from synthetic coal fly ash extracts was analyzed. The examined membranes were analyzed in terms of adsorption kinetics, isotherms, selectivity, reuse, and their separation abilities. The experimental data obtained were analyzed with two applications, namely, REE 2.0 and REE_isotherm. It was found that the adsorption of Nd³⁺ and Y³⁺ ions in the obtained membranes took place according to the chemisorption mechanism and was significantly controlled by film diffusion. The binding sites on the adsorbent surface were uniformly distributed; the examined ions showed the features of regular monolayer adsorption; and the adsorbents showed a strong affinity to the REE ions. The high values of K_d (900–1472.8 mL/g) demonstrate their high efficiency in the recovery of REEs. After five subsequent adsorption–desorption processes, approximately 85% of the value of one cycle was reached. The synthesized membranes showed a high rejection of the matrix components (Na, Mg, Ca, Al, Fe, and Si) in the extracts of the coal fly ashes, and the retention ratio for these Nd and Y ions was 90.11% and 80.95%, respectively.

Carbon nanotubes (CNTs), due to their unique combination of physicochemical properties, are continuously considered as one of the most interesting materials in contemporary science and industry. Their applicability depends on physical properties, such as number of walls, morphology, diameter and length (aspect ratio), but also on the content of carbonaceous and metallic contaminants (typically present as encapsulated catalyst nanoparticles from catalytic Chemical Vapor Deposition). Therefore, especially for medical and biomedical applications, the concentration of metallic impurities or modifiers should be monitored. In this paper, an inductively coupled plasma atomic emission spectrometry (ICP-AES) technique with slurry nebulization is proposed for direct determination of iron in multi-wall carbon nanotubes (MWCNTs). Slurries of MWCNTs are prepared in a 1% solution of Triton X-100, ultrasonicated to ensure their homogeneity and measured by the ICP-AES apparatus. The optimal range of MWCNTs slurry concentration and plasma radiofrequency (RF) power are established as 40–500 mg L⁻¹ and 1.0 kW, respectively. The precision of the method does not exceed 1.5% of the mean values. Validation of the method is based on the fact that Fe is partly leached from the slurry and the assumption that iron in the leachate gives the same response in ICP-AES as iron in the residual MWCNTs slurry. This behavior was proved by summing both results for Fe (determined in the leachate and in the slurry of post-leaching nanotubes), which always yielded the same total amount of Fe for different degrees of leaching and this value was in full agreement with the iron content in the original, tested sample, as determined by the proposed slurry method. Taking into account all the examinations and obtained results, it can be concluded that the proposed method is applicable for fast, versatile, direct, and simple quantitative analysis of iron in MWCNTs and potentially other nanoallotropes produced by c-CVD.

Pectin-guar gum biosorbent was tested for zinc(II) ions removal in column process. Sorption–desorption experiments were performed in laboratory and at larger scale. The breakthrough and elution curves were obtained for various conditions. The Bed Depth Service Time model was tested for utility in data estimation. Possibility of sorbent reuse and its lifetime was examined in 20 repeated sorption–desorption cycles. Finally, tests were repeated for real wastewater from galvanizing plant, giving satisfactory results. The effectiveness of Zn(II) sorption happened to be dependent on process parameters; tests have proved that it increased with increasing bed height and with decreasing flow rate or grain size. For an initial zinc concentration of 30 mg/L, even 2096 mL of zinc solution could be purified in small scale experiment (2 g of fine grain sorbent and flow rate 60 mL/h) or 5900 L in large-scale (16 kg of large grain sorbent and flow rate 45 L/h). This allowed for 40-fold or 49-fold zinc increases in concentration in one sorption–desorption cycle. The most successful results are meant that at least 20 sorption–desorption cycles could be performed on one portion of biosorbent without loss of its effectiveness, large-scale tests for real wastewater from galvanizing plant gave satisfactory results, and that the form and mechanical stability of our sorbent is suitable for column usage with flow rates applicable in industry.