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Human hair natural fiber is mainly considered a waste in our society and its disposal can cause a major environmental impact. Hence, its valorization as a biosorbent of pollutants such as heavy metals is an interesting route to explore since it can reduce the amount of waste and at the same time contributes to the circular economy strategy. In this work, the ability of two kind of human hairs, used as biosorbents to remove Cr(III), Ni(II), Co(II), Mn(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions from multiple-metal aqueous solutions, were examined and compared under different operating conditions. The influence of the time, pH and initial metal concentration on the metal uptake were studied. The biosorption kinetics and isotherm were also modeled observing that pseudo-second order kinetic model and Langmuir model fitted successfully experimental data. Moreover, biosorption process did not significantly modify the morphology and the chemical structure of the hair samples, which was proved by SEM and FT-IR studies. These kinetic results underline the satisfactory capacity of human hair for the biosorption of Pb(II), Cu(II) and Cr(II) (values up to 95%), pointing up the high efficacy of human hair for the removal of heavy metal ions from aqueous media.

Human hair is considered a ubiquitous waste product and its accumulation can cause environmental problems. Hence, the search for alternatives that take advantage of this waste as a new raw material is of interest, and contributes to the idea of the circular economy. In this study, chemically modified human hair was used as a low cost biosorbent for the removal of heavy metal ions from aqueous solutions. The effect of the contact time, the pH, and the biosorbent concentration on the biosorption process were investigated. Kinetic modeling indicated that the pseudo-second order kinetic equation fitted well with R2 > 0.999. Furthermore, the equilibrium data fitted the Langmuir adsorption isotherm at 295 K resulting in saturation concentrations of 9.47 × 10−5, 5.57 × 10−5, 3.77 × 10−5, and 3.61 × 10−5 mol/g for the sorption of Cr(III), Cu(II), Cd(II), and Pb(II), respectively. The biosorption process did not change the chemical structure and morphology of the hair, which was shown by FTIR and SEM. In addition, desorption experiments prove that 0.1 mol/L EDTA solution is an efficient eluent for the recovery of Pb(II) from the treated human hair. To summarize, treated human hair showed satisfactory biosorption capacity and can be considered as an effective biosorbent for the treatment of water with a low concentration of heavy metal ions.

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According to the Circular Economy Package promoted by the European directive, plastic bags companies must use in their formulations a percentage of polyethylene waste (industrial and/or domestic) greater than 70%. Following that regulation requires an understanding of its consequences in the final product from an industrial point of view. This manuscript analyzes the thermal and morphological changes related to the tear resistance of linear-low density polyethylene (LLDPE) samples from industrial waste generated by the company Sphere Spain subjected to the degradation produced by the recycling cycles. The process is analogue to the industrial, starts from samples in pellets then a film by blow extrusion is obtained (odd steps) and posteriorly this film is recycled to pellets again (even steps). The results obtained show that the LLDPE samples develop two crystalline structures (CS1 and CS2) which evolve differently through the recycling cycles with a tendency to decrease in crystallinity due to degradation that is not the same for the process of obtaining film or recycling to pellet. The molecules with a more linear structure and a longer chain break and branch. The more branched structure increases and tends to crosslinking. This leads to a decrease in tear strength in the longitudinal direction, which is not so evident in the transversal direction. The samples could admit four recycling cycles with and acceptable tear resistance. The longitudinal tear strength value decreases by 40% for each film and 20% in the case of tearing in the transverse direction. The results obtained in this research work show that the regulations included in the cited circular economy package can be applied in the manufacture of consumer bags, helping also to reduce the dependence of manufacturers on fluctuations in delivery by collapses in shipping.

The thermosensitive properties of the hydrogel poly(N-isopropylacrylamide) (pNIPAAm) together with the good mechanical properties of lyocell fibres make a combination of the two to be thought of as a smart textile. In the present study the optimal values of various parameters that control the grafting process of pNIPAAm onto lyocell fibres were determined considering the influence of the interaction between them. The copolymerization of pNIPAAm hydrogel onto lyocell fibres was performed in aqueous acidic medium using cerium(IV) as initiator. An experimental design was planned in order to study the effect of the interactions between some variables that affect the kinetics of the graft copolymerization: the cerium(IV) initiator concentration, the N-isopropylacrylamide (NIPAAm) monomer concentration and the liquor fibre-to-bath ratio. The results show that the interaction between the concentrations of NIPAAm and the initiator significantly affects the degree of grafting (DG), the optimum values being 1250 and 12.25 mmol L−1, respectively. In contrast, the liquor ratio parameter shows no significant interaction with the other two variables studied, meaning that it acts independently but showing a proportional relationship with respect to the DG obtained. In addition, the presence of pNIPAAm in the copolymer obtained was confirmed by Fourier transform infrared spectral analysis. Moreover, the water sorption capacity, depending on the temperature, of the lyocell/pNIPAAm copolymer was studied, with an increase being observed when the DG is higher than 60% and also increasing with the temperaturePostprint (published version

Microplastics (MPs, size < 5 mm) are among the most environmentally challenging pollutants. Their continuous and cumulative inflow or generation in the environment is what makes them drastically problematic. These pollutants can come from a wide variety of sources; hence, they are potential vectors that pose extensive risks to environmental and human health. Microfibers (MFs) are one type of MPs. Among the most well-known types of MFs are those detached from textile articles from household laundering or industrial processes. Currently, there are many ways to retain the MFs detached from textile articles. However, as far we know, there are no methods of valorizing the retained MFs. As such, we propose a novel and sustainable treatment method to immobilize MFs in a polymeric matrix, turning them into a composite. To determine the mechanical properties of the expected composites, different proportions of polyester MFs were mixed with low-density polyethylene, which is the material proposed for the immobilization of MFs. The results show that the optimum manufacturing composition was 10% (v/v) polyester MFs in the polymeric matrix. This composition improved some of the tensile mechanical properties of the polymeric matrix. Once the composites are obtained, these can be used for different purposes.

Incorporation of residua into polymeric composites can be a successful approach to creating materials suitable for specific applications promoting a circular economy approach. Elastomeric (Ground Tire Rubber or GTR) and biogenic (chicken feathers or CFs) wastes were used to prepare polymeric composites in order to evaluate the tensile, acoustic and structural differences between both reinforcements. High-density polyethylene (HDPE), polypropylene (PP) and ethylene vinyl acetate (EVA) polymeric matrices were used. EVA matrix defines better compatibility with both reinforcement materials (GTR and CFs) than polyolefin matrices (HDPE and PP) as it has been corroborated by Fourier transform infrared spectroscopy (FTIR), termogravimetric analysis (TGA) and scanning electron microscopy (SEM). In addition, composites reinforced with GTR showed better acoustic properties than composites reinforced with CFs, due to the morphology of the reinforcing particles.