One-Step Synthesis of Starch-Based Composite Chrome-Free Tanning Agents via In Situ Catalysis Using Hydrotalcites

Theoxidation of starch into valuable chemicals holds great promisefor the leather industry, but the catalytic efficiency of existingreactions is low. Moreover, residual catalyst in the reaction liquidis a potential environmental hazard. Herein, starch was oxidized byhydrogen peroxide and a magnesium aluminum iron hydrotalcite (MgAlFe-LDH)catalyst to introduce functional groups and nanomaterials, forminga starch-based hydrotalcite composite (OS-MgAlFe-LDH) in one step.This catalyst showed improved catalytic efficiency, and the generationof pollution was avoided. Moreover, the prepared OS-MgAlFe-LDH wassuitable as a complex tanning agent for chrome-free tanning with improvedefficiency, and MgAlFe-LDH acted as a crosslinking reinforcing agent.Using this tanning agent, the hydrothermal stability of crust leatherwas enhanced (shrinkage temperature: 75 & DEG;C). The tanned leatherhad high porosity (79.06%) and a uniform tanning agent distributionascribed to the varying molecular weights of the components of theOS-MgAlFe-LDHs (weight-average molecular weight: 5438 g/mol). Thebinding energy between OS-MgAlFe-LDHs and the leather collagen (94.62kcal/mol) was high, inhibiting the migration of OS-MgAlFe-LDHs fromthe collagen matrix. Thus, OS-MgAlFe-LDHs exhibited strong crosslinkingperformance with leather collagen. In summary, a sustainable and environmental-friendlytanning agent was prepared by a one-step synthesis in this work, offeringa fundamental step for the preparation of biomass materials in theleather industry. A"killing two birds with one stone" strategy(catalysis and coordination) for green and sustainable leather manufacturing.