As a novel polymer, polyurethane (PU) has been widely applied in leather, synthetic leather, and textiles due to its excellent overall performance. Nevertheless, conventional PU is flammable and its combustion is accompanied by severe melting and dripping, which then generates hazardous fumes and gases. This defect limits PU applications in various fields, including the leather industry. Hence, the development of environmentally friendly, flame-retardant PU is of great significance both theoretically and practically. Currently, phosphorus-nitrogen (P-N) reactive flame-retardant is a hot topic in the field of flame-retardant PU. Based on this, the preparation and flame-retardant mechanism of flame-retardant PU, as well as the current status of flame-retardant PU in the leather industry were reviewed.

The safety of flexible polyvinyl chloride (PVC) materials is now being questioned, partially due to allegations that di-(2-ethylhexyl) phthalate (DEHP), the dominant PVC plasticizer, is an endocrine disruptor and a probable carcinogen. As sustainable alternatives, aliphatic ester-derived plasticizers feature low cytotoxicity, biodegradability, and renewability, but they can only partially replace DEHP in PVC formulations because they have a strong tendency to migrate. Here, using epoxidized fatty acid methyl esters and aliphatic diesters as representatives, we demonstrate that covalently attaching one short ester at each α-position of aliphatic esters via Claisen condensation with judiciously selected dialkyl carbonate significantly suppresses their migration from the PVC matrix. In certain scenarios, the engineered plasticizers even migrate at a rate comparable to, or improved beyond that of DEHP. This approach harnesses the α-proton, a structural feature shared by all aliphatic esters, and dialkyl carbonate, an established “green chemical”, thus providing a potentially general and green route towards DEHP alternatives with unprecedented performance that may contribute to sustainability of the old and oft-maligned PVC industry.

Potential ecological risks of chromium(III) contaminates in tannery effluents have evoked considerable discussion and re-examination over the future role of chrome tannage, which has been long considered as the foundation of the modern leather industry. Despite previous magnetite-supported adsorbents for chromium removal, few of them were specifically engineered to address trivalent chromium, as well as the composition complexity in tannery effluents. Herein, gallic acid, a natural triphenolic compound capable of coordination to chromium(III), was covalently conjugated onto engineered magnetite nanoparticles via 1-ethyl-3-(3-dimethylaminepropyl) carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) chemistry, in an effort to design a magnetically separable nanoadsorbent applicable for remediating chromium(III)-contaminated tannery effluents. The structure of the nanoadsorbent was systematically characterized by multiple techniques, and the influence of pH value, adsorbent dose, temperature, and leather-related co-existing substances on its chromium(III) removal potency was investigated, respectively. Also, kinetics, equilibrium, and thermodynamics studies were conducted to decipher the mechanism by which chromium(III) cations were adsorbed. Finally, the feasibility of treating real tannery effluents that also contained high concentrations of sulfides, chlorides, ammonium nitrogen, total suspended solids, chemical oxygen demand (COD_Cr), and biochemical oxygen demand (BOD) by using the nanoadsorbent designed herein was explored. It was found that the chromium(III) removal percentage was approximately 95.2 ± 1.6%, and the exhausted nanoadsorbent could be conveniently separated from the effluents via a simple magnetic process. By chemical desorption, the nanoadsorbent was regenerable, and reusable for multiple cycles without a significantly compromised adsorption potency. According to these results, we aim at providing an efficient solution that may be a great addition to the ongoing fight against chromium(III) contamination in tannery effluents.

Chromium(III) contamination in tannery effluents continues to represent a significant challenge towards sustainable development of the global leather industry. Despite various magnetite-supported adsorbents for chromium removal previously reported, few of them were specifically designed to address trivalent chromium and the complexity of pollutants in tannery effluents. In the present study, polyacrylic acid, capable of adsorbing chromium(III) by coordination, was grafted from the surface of Fe₃O₄ nanoparticles via the bridging function of a silane coupling agent to produce a magnetically-separable nanoadsorbent (PAA@VTES@Fe₃O₄) for chromium(III) remediation from tannery effluents. The structure and morphologies of the nanoadsorbent were systematically characterized by scanning electron microscopy, low-temperature nitrogen adsorption/desorption experiments, energy dispersive X-ray spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, total organic carbon content and X-ray diffraction analysis. With a saturated magnetization of 46.8 emu g⁻¹, PAA@VTES@Fe₃O₄ could be separated from water within 5 min by using a magnet. Adsorption experiments showed that chromium(III) adsorption on PAA@VTES@Fe₃O₄ was pH- and adsorbent dose-dependent; adsorption equilibrium could be reached in 2.5 h, resulting in a chromium(III) removal percentage of more than 90% under optimized conditions. The adsorption kinetics were best described by pseudo-first order and pseudo-second order models, while the isotherm data were found to agree well with both Langmuir and Freundlich models. Based on the fitting results, it was found that PAA@VTES@Fe₃O₄ exhibited high adsorption capability relative to many other adsorbents previously suggested as efficient for chromium(III) removal from effluents. In addition, a thermodynamic study revealed that the adsorption process was endothermic and spontaneous in nature. By chemical desorption, PAA@VTES@Fe₃O₄ could be regenerated and repeatedly used for five cycles without significantly compromising the adsorption capacity. Even in the presence of large amounts of decomposing organic matter, hair, lime, sulphide and organic nitrogen, PAA@VTES@Fe₃O₄ was still capable of removing more than 90% of chromium(III) from tannery effluents, exhibiting a high potential for practical application.

Plasticizer migration is responsible for premature coating failure in polyvinyl chloride (PVC) synthetic materials that continue to benefit our daily life as a reliable and cost-efficient simulant of genuine leather. In this context, the establishment of standard assays that measure the migration rate of plasticizers under varying scenarios plays a pivotal role in comparing durability of those PVC-derived leather-simulants. In this review, multiple methodologies developed over the last decade for determining plasticizer migration from PVC coating are compiled, with their operational principles, merits, and limitations being taken into consideration along with specific apparatus required for each. A concluding section discusses current challenges in this field, and highlights how nuclear magnetic resonance and computational simulation surpass conventional assays in yielding intercomparable results, and hence screening migration-resistant plasticizers in a labor- and time-saving way. Since migration resistance represents a decisive performance indicator of plasticizers, this systematic review may provide guidance to quite a few practitioners in PVC synthetic material industry, who are now engaged in validating various sustainable alternatives with performance allegedly equal to conventional but toxic di-(2-ethylhexyl) phthalate plasticizer. Graphical abstract