Emerging pollutants from industrial, urban and natural sources pose a risk for aquatic environments around the world. Hence, the development of sustainable and cost-effective solutions for the removal of those pollutants is still a challenging task. Although many promising bio-based adsorbents exist, which have shown to effectively bind organic and inorganic pollutants, most of them have unfavourable mechanical properties in terms of surface area, binding capacity, morphology etc. Chitosan has shown to be to be capable of removing organic and inorganic pollutants from aqueous media taking into account, that modifications of chitosan (crosslinking, grafting, etc.) increased its adsorption capacity (Saheed et al., 2021). Likewise, modifications of polyurethane foams through incorporation of additives are able to increase their absorption capacity of a wide range of pollutants by influencing properties like hydrophobicity, surface area, selectivity (Selvasembian et al., 2021).

In this study, biodegradable chitosan polyurethane foams (BCPF) with up to 30 w/w% chitosan (particle size 63 – 2000 μm) were synthesized. BCPF samples (cuboids, 0.3 g) were incubated in Iron(II) sulfate solution (15 mg L-1) for 90 min or 7 days on a rotary shaker at 20 °C. After incubation, BCPF samples were removed, ammonium chloride, hydrochloric acid and sulphosalicylic acid were added to the solution and the iron content of the solution was measured photometrically at 424 nm. Control samples with pristine chitosan were treated identically. Biodegradability of polyurethane foams was assessed manometrically according to OECD TG 301F for 28 days while acute toxicity of eluates of polyurethane foams (8 weeks incubation in water) was investigated by performing bioassays with larvae of the fairy shrimp Thamnocephalus platyurus.

Incorporation of chitosan increased iron adsorption capacity of polyurethane foams by up to 400 % after 7 days incubation compared to pristine BCPF. Here, chitosan with smaller particle sizes showed higher adsorption capacities, whereas the influence of the mass percentage of chitosan on the adsorption capacity of polyurethane foams was strongly dependent on the formula of the foams. Biodegradation studies exposed degradation rates of more than 10 % while no toxic effects were observed for eluates diluted 1:2 with test media.

The presented results underline the potential of incorporation promising adsorbents for water pollutants into polyurethane foams. Modifications of the polyurethane foams as well as the use of mixtures of several additives allow adapting BCPF adsorbents for application to remove a wide range of pollutants. Since water can flow through BCPF and due to their pore-like structure, they could also eventually be used to remove particular substances like microplastic and could therefore be combined with existing techniques (Kurzweg et al., 2022).