Aluminum tanning of hide powder and skin pieces under microwave irradiation

Abstract

The application and mechanism study of microwave irradiation in traditional industries have attracted considerable attention owing to the unique thermal and athermal effects that could lead to unexpected benefits in high-efficiency and clean production. Herein, we report the investigation of the aluminum tanning under microwave irradiation upon using hide powder and skin pieces, respectively, as simulants of real hide or skin. The aluminum tanning process and the tanned products under microwave heating (MWH) were studied and compared with those of conventional water bath heating (WBH) as the controls. For the tanning system of hide powder, the tanning effluents were analyzed in terms of pH, conductivity, dielectric constant and aluminum content, and the tanned powder was investigated by differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, and FT-IR spectroscopy. For the skin piece system, the pH and aluminum content of tanning effluents were also determined, and at the same time, DSC, TG, SEM, FT-IR and shrinkage temperature were used to illustrate the actions of microwaves on the structure and properties of the tanned pieces. The results show that aluminum reactivity in the penetration and binding process of collagen fibers in hide powder and skin pieces improved using microwave treatment. The residual aluminum content was greatly reduced by microwave heating action, and the increased amount of aluminum with evener distribution was observed in the tanned products. Microwave irradiation also resulted in the tanned products with better thermal stability and thermal decomposition resistance. This work further promotes application of microwave treatments for aluminumbased tanning in leather industry.

Multifunctional, Ultra‐Tough Organohydrogel E‐Skin Reinforced by Hierarchical Goatskin Fibers Skeleton for Energy Harvesting and Self‐Powered Monitoring

“…The chemical and physical interactions in S@HCP were further verified by using FTIR (Fourier transform infrared), TG (thermogravimetric), and XPS (X‐ray photoelectron spectroscopy) methods, respectively. As shown in Figure b, in the FTIR spectrum of S, the smooth peaks at 1640 cm −1 (amide I) and 1539 cm −1 (amide II) represented the characteristic peaks of skin collagen; [ 61 ] the sharp peak at 1703 cm −1 in the FTIR spectrum of H was attributed to the metal coordination in PAA/Zr 4+ hydrogel. These three peaks concurrently were observed in the FTIR spectra of S@H and S@HC (without PDO), which indicates that there are characteristic structures of both skin collagen and the PAA/Zr 4+ hydrogel in S@HCP.…”

“…The thermal stability of S, H, and S@H at 37–600 °C was clearly depicted in the TG (Figure 4c) and the corresponding DTG (Figure 4d) curves. A sharp peak appeared at 336.4 °C in the DTG curve of S, which is the decomposition temperature of skin collagen skeleton, [ 61 ] while a broad peak appeared at 467.3 °C in the DTG curve of H, which is the decomposition temperature of PAA main chains. [ 62 ] It is worth noting that, in the S@H's DTG curve, there was a sharp and wide peak at 421.0 °C (higher than the original decomposition temperature of collagen skeleton), which may be caused by the fact that the collagen fibers were wrapped by the PAA layers, thereby improving thermal stability of collagen skeleton.…”

Green and sustainable ‘Al-Zr-oligosaccharides’ tanning agents from the simultaneous depolymerization and oxidation of waste paper

“…Therefore, developing chrome-free and sustainable tanning agents is of paramount importance for the short and medium-term future development of the leather industry. Given these restrictions and issues, aluminum and zirconium salts have been recently considered promising alternative tanning agents to replace chrome-based agents due to their excellent coordination abilities and low environmental risk (Zhang et al, 2021;Liu et al, 2020;Feng et al, 2015). However, during the initial tanning stage, such chrome-free metal salts react strongly with the collagen fibers.…”