The overproduction of pollutants resulting from the development of industry causes the deposition of large amounts of toxic and carcinogenic substances, including heavy metals, in the aquatic ecosystem and other ecosystems. This is a civilisation problem of the present times, posing a serious threat to the natural environment, including humans. For this reason, it has recently become extremely important to develop effective methods to minimise the concentration of heavy metal ions in the aquatic systems and thus reduce their negative impact on the environment. One such technique is adsorption, which is believed to be an effective method of removing contaminants such as heavy metal ions from aqueous solutions. Looking at the available literature of the last few years, it can be concluded that adsorbents of natural origin are becoming more and more important. These are agricultural waste, all kinds of biomass, and waste from various industries. The study attempts to present and evaluate the sorption capacity of materials of natural origin, including oat bran, chitosan, alginate, tree bark, coconut fibre, and lignin. The use of such biosorbents is more friendly for the environment compared to their synthetic counterparts and perfectly fits the concept of sustainable development and the circular economy.

In response to the trend toward sustainable management of by-products from the pulp and paper industry as well as plant waste, practical and economical methods are being developed to use them in a way that does not pose a threat to the environment. The main aim of the research was to study the possibility of using lignin and plant biomass as biosorbents for the removal of zinc ions from aqueous solutions. The secondary aim was to build an optimal multilayer system made of biosorbents selected during the research in order to obtain the highest sorption efficiency and to determine the best conditions of the sorption process. The effectiveness of zinc ion sorption was assessed using an appropriate combination of sorbents such as lignin, oat bran, rice husk, chitosan, pectin, sodium alginate, pine bark, coconut fiber and activated carbon, selected on the basis of literature data and the preliminary results of tests carried out using FTIR and AAS. The main component of the sorption system was lignin separated from black liquor. Results indicate that the best Zn sorption system was based on coconut fiber, lignin, and pine bark, for which the maximum sorption efficiency was 95%. The research also showed that the increase in the process temperature, the mass of biosorbents used and the alkaline pH are the factors that increase the efficiency of the sorption. It can be concluded that lignin and plant biomass can be used as ecological sorbents of zinc ions from water solutions. They are safe for the environment, produced from renewable sources, and are by-products or waste materials, which is part of the sustainable development and circular economy currently promoted in the EU.

This study presents a method for extracting lignin and hemicellulose from black liquor using organic acids (citric, malic, and acetic) in comparison to the traditional sulfuric acid method. We investigated and compared the influence of the acid type on the structural properties of the resulting precipitates in the context of their potential applications. The lignin fractions were characterized for their chemical structure (ATR-FTIR, NMR), thermal stability (TGA), morphology and surface elemental composition (SEM-EDS), bulk elemental composition (C, H, N, S), and molecular weight distribution (GPC). The hemicellulose fractions were analyzed for their molecular weight (GPC), surface elemental composition (EDS), and chemical structure (ATR-FTIR). These analyses revealed subtle differences in the properties of the individual materials depending on the extraction method. We showed that organic acids, particularly citric acid, can effectively precipitate lignin with yields comparable to the sulfuric acid method (47–60 g/dm³ vs. 50 g/dm³). Simultaneously, this method produces lignin with higher purity (regarding sulfur content) and an increased content of carboxyl groups. This latter aspect is of particular interest due to the enhanced potential of lignin’s adsorption functions towards metal ions. AAS analysis confirmed that lignin precipitated with citric acid showed better adsorption efficiency towards heavy metals compared to lignin precipitated with sulfuric acid, especially for Cu²⁺ ions (80% vs. 20%) and Cr³⁺ ions (46% vs. 2%). This enhanced adsorption efficiency of the isolated lignins, combined with the environmental benefits of using organic acids, opens a promising perspective for their application in water treatment and environmental remediation. Furthermore, the presented research on the valorization and reuse of paper industry by-products fully aligns with the fundamental principles of the Circular Economy.

Paper-based packaging is widely promoted as a sustainable alternative to plastic; however, functional coatings can reduce fibre integrity and lead to burden shifting in industrial recycling systems. This review examines how these effects undermine the environmental benefits expected from fibre-based packaging and weaken progress towards high-quality circularity, as required by current EU sustainability policy. By comparing leading assessment schemes (PTS, CEPI, 4evergreen) with industrial evidence, we identify a systemic gap: laboratory-focused recyclability tests often overlook fibre-quality degradation and the resulting limitations for circular material loops. To close this gap, we propose a sustainability-oriented extension module based on three measurable ISO-anchored indicators—fibre length, fines fraction and WRV—that prevent “recyclable-only-on-paper” claims and support genuinely sustainable recycling performance. Case studies demonstrate how high laboratory yields can mask low industrial recyclability and thus hinder circular economy objectives. This study contributes to sustainability science by operationalising recyclability in a manner consistent with EU circularity goals and by providing a transparent method to protect fibre value in multiple loop cycles.