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- ItemThe Influence of Salt Anions on Heavy Metal Ion Adsorption on the Example of Nickel(Basel : MDPI, 2018) Mende, Mandy; Schwarz, Dana; Steinbach, Christine; Boldt, Regine; Schwarz, SimonaThe biodegradable polysaccharide chitosan possesses protonated and natural amino groups at medium pH values and has therefore been used as an adsorbing material for nickel salts in water treatment. Nickel is a problematic heavy metal ion which can cause various diseases and disorders in living organisms. Here, we show the influence of oxyanions (e.g., nitrate and sulfate) to the adsorption of nickel ions. Hence, simultaneously we are addressing the increasing global problem of nitrate and sulfate ion pollution in groundwater and surface water. A series of adsorption experiments was carried out in order to determine (i) the adsorption equilibrium, (ii) the adsorption capacity in dependence on the initial nickel ion concentration, and (iii) the influence of the anion presented in solution for the adsorption capacity. Surface morphology of chitosan flakes before and after the adsorption process has been studied with SEM-EDX analysis. The chitosan flakes exhibited promising adsorption capacities of 81.9 mg·g−1 and 21.2 mg·g−1 for nickel (sulfate) and nickel (nitrate), respectively. The calculated values of Gibbs free energy change ΔG0 confirm the higher adsorption of nickel ions in presence of sulfate ions. Hence, higher anion valence leads to a higher adsorption capacity.
- ItemSolubility and selectivity effects of the anion on the adsorption of different heavy metal ions onto chitosan(Basel : MDPI, 2020) Weißpflog, Janek; Gündel, Alexander; Vehlow, David; Steinbach, Christine; Müller, Martin; Boldt, Regine; Schwarz, Simona; Schwarz, DanaThe biopolymer chitosan is a very efficient adsorber material for the removal of heavy metal ions from aqueous solutions. Due to the solubility properties of chitosan it can be used as both a liquid adsorber and a solid flocculant for water treatment reaching outstanding adsorption capacities for a number of heavy metal ions. However, the type of anion corresponding to the investigated heavy metal ions has a strong influence on the adsorption capacity and sorption mechanism on chitosan. In this work, the adsorption capacity of the heavy metal ions manganese, iron, cobalt, nickel, copper, and zinc were investigated in dependence on their corresponding anions sulfate, chloride, and nitrate by batch experiments. The selectivity of the different heavy metal ions was analyzed by column experiments. © 2020 by the authors.
- ItemA Complementary and Revised View on the N-Acylation of Chitosan with Hexanoyl Chloride(Basel : MDPI, 2021) Reis, Berthold; Gerlach, Niklas; Steinbach, Christine; Haro Carrasco, Karina; Oelmann, Marina; Schwarz, Simona; Müller, Martin; Schwarz, DanaThe modification of the biobased polymer chitosan is a broad and widely studied field. Herein, an insight into the hydrophobization of low-molecular-weight chitosan by substitution of amino functionalities with hexanoyl chloride is reported. Thereby, the influence of the pH of the reaction media was investigated. Further, methods for the determination of the degree of substitution based on 1H-NMR, FTIR, and potentiometric titration were compared and discussed regarding their accuracy and precision. 1H-NMR was the most accurate method, while FTIR and the potentiometric titration, though precise and reproducible, underlie the influence of complete protonation and solubility issues. Additionally, the impact of the pH variation during the synthesis on the properties of the samples was investigated by Cd2+ sorption experiments. The adjusted pH values during the synthesis and, therefore, the obtained degrees of substitution possessed a strong impact on the adsorption properties of the final material.
- ItemWaterborne phenolic, triazine-based porous polymer particles for the removal of toxic metal ions(Amsterdam : Elsevier, 2022) Borchert, Konstantin B.L.; Frenzel, Robert; Gerlach, Niklas; Reis, Berthold; Steinbach, Christine; Kohn, Benjamin; Scheler, Ulrich; Schwarz, Simona; Schwarz, DanaHighly functional and also highly porous materials are presenting great advantages for applications in energy storage, catalysis and separation processes, which is why a continuous development of new materials can be seen. To create a material combining the promising potential interactions of triazine groups with the electrostatic or hydrogen bonding interactions of phenolic groups, a completely new polymeric resin was synthesized. From an eco-friendly dispersion polymerization in water, a copolymer network was obtained, which includes nine hydroxyl groups and one s-triazine ring per repetition unit. The polymer forms highly porous particles with specific surface areas up to 531 ​m2/g and a negative streaming potential over a great pH range. The adsorption isotherms of Ni2+, Cd2+, and Pb2+ were studied in more detail achieving very good adsorption capacities (16 mg Ni2+/g, 24 mg Cd2+/g, and 90 mg Pb2+/g). Demonstrating excellent properties for adsorption applications. The adsorbent exhibited selectivity for the adsorption of Pb2+ over more commonly occurring but non-toxic metal ions such as Fe2+, Ca2+, Mg2+, and K+. Furthermore, reusability of the material was demonstrated by facile, quantitative desorption of adsorbed Pb2+ with a small amount of diluted HCl, circumventing organic chelators. Subsequently, adsorption was carried out without decrease in adsorption performance.
- ItemComplex calcium carbonate/polymer microparticles as carriers for aminoglycoside antibiotics(London : RSC Publishing, 2018) Racovita, Stefania; Vasiliu, Ana-Lavinia; Bele, Adrian; Schwarz, Dana; Steinbach, Christine; Boldt, Regine; Schwarz, Simona; Mihai, MarcelaComposite microparticles of CaCO3 and two pectin samples (which differ by the functional group ratio) or corresponding nonstoichiometric polyelectrolyte complexes with different molar ratios (0.5, 0.9 and 1.2) are obtained, characterized and tested for loading and release of streptomycin and kanamycin sulphate. The synthesized carriers were characterized before and after drug loading in terms of morphology (by SEM using secondary electron and energy selective backscattered electron detectors), porosity (by water sorption isotherms) and elemental composition (by elemental mapping using energy dispersive X-ray and FTIR spectroscopy). The kinetics of the release mechanism from the microparticles was investigated using Higuchi and Korsmeyer-Peppas mathematical models.