Toxic heavy metals are priority pollutants in wastewater, commonly present in dangerous concentrations in many places across the globe. Although in trace quantities copper is a heavy metal essential to human life, in excess it causes various diseases, whereby its removal from wastewater is a necessity. Among several reported materials, chitosan is a highly abundant, non-toxic, low-cost, biodegradable polymer, comprising free hydroxyl and amino groups, that has been directly applied as an adsorbent or chemically modified to increase its performance. Taking this into account, reduced chitosan derivatives (RCDs 1–4) were synthesised by chitosan modification with salicylaldehyde, followed by imine reduction, characterised by RMN, FTIR-ATR, TGA and SEM, and used to adsorb Cu(II) from water. A reduced chitosan (RCD3), with a moderate modification percentage (43%) and a high imine reduction percentage (98%), proved to be more efficient than the remainder RCDs and even chitosan, especially at low concentrations under the best adsorption conditions (pH 4, R_S/L = 2.5 mg mL⁻¹). RCD3 adsorption data were better described by the Langmuir–Freundlich isotherm and the pseudo-second-order kinetic models. The interaction mechanism was assessed by molecular dynamics simulations, showing that RCDs favour Cu(II) capture from water compared to chitosan, due to a greater Cu(II) interaction with the oxygen of the glucosamine ring and the neighbouring hydroxyl groups.

Green, transparent and flexible electrolyte films composed of a Bombyx mori silk fibroin (SF) host biopolymer doped with glycerol (G), dimethyl sulfoxide (DMSO, D) and 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF₆) ionic liquid (IL), were synthesized. The materials were represented by the notation SF@GD@IL _x (x = 15, 20 and 30 is the mass ratio of SF/[Bmim]PF₆ in %). SF@, SF@G, SF@D and SF@GD samples were also prepared. DMSO was found to play a dual-role, acting as solvent of [Bmim]PF₆, and enhancing ionic conductivity. DMSO, alone or combined with [Bmim]PF₆, led to the increase of the mean roughness and induced the formation of more ordered Silk II conformations (β-sheets). No structural modifications were detected in the SF@GD@IL _x samples upon increasing the temperature up to 100 °C. The highest ionic conductivity was exhibited by the IL-rich sample SF@GD@IL₃₀ (1.07 and 4.61 mS cm⁻¹, at 22 and 100 °C, respectively). In the [Bmim]PF₆-doped electrolytes “free” and coordinated PF₆ ⁻ ions coexist. The weight losses occurring below 200 °C involved essentially the release of adsorbed water and DMSO. The suitable mechanical properties, high ionic conductivity and good electrochemical stability suggest that these electrolytes are attractive candidates for application in electrochemical devices.

The increasing presence of antibiotics in aquatic environments is a growing concern, causing ecological and public health risks. Even low concentrations of antibiotics may lead to the development of antibiotic-resistant bacteria. The interest in building new materials that can be used as templates for removing pollutants from the environment has been growing year upon year. We review the research involving adsorption processes that occur in chitosan-based materials that are employed to remove antibiotics from water. Since covering all the antibiotics that can be found in the environment would be an overwhelming task, we concentrated our efforts on describing the studies related to the removal of tetracycline, ciprofloxacin, cephalexin, and azithromycin, which are perhaps the most ubiquitous ones. We present the chemical modifications introduced into chitosan and chitosan-based materials commonly used as antibiotic adsorbents, as well as the influence of physical chemistry conditions on these processes. In addition, we also review in silico studies that have been carried out to obtain molecular-level insights into the interactions between chitosan-based adsorbents and the four mentioned antibiotics. Particular emphasis is placed on our recent computational work regarding the adsorption of tetracycline by various chitosan-based materials.