Silicic acid, commonly derived from cheap and easily available sodium silicate, has recently received great attention for application in leather industry to produce ecological leather with a cleaner approach. However, leather tanned with silicic acid alone is poor in storage stability, which limits its practical application in leather production. In this work, a new environment-friendly combination tannage based on silicic acid and plant tannin was developed to address this issue along with improving the comprehensive performances of leather. The obtained leather was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and so on. The results showed that compared with leather tanned with silicic acid alone, the leather tanned with this combination method possessed improved thermal stability, enhanced mechanical properties, acceptable softness, appropriate hydrophilicity, and especially enhanced storage stability. More importantly, the combination tanned leather with 1:1 of the mass ratio of silicic acid to vegetable tannin (composed of valonea extract and mimosa extract with the same weight) had more prominent comprehensive performances. In addition, the results demonstrated that hydrogen bonding played an important role in the combination tanning process. Furthermore, the hydrogen bonds generated between phenolic hydroxyl groups of polyphenols with silicon hydroxyl groups of silicic acid molecules inhibited the excessive condensation of Si-OH groups between themselves. Subsequently, the assessment of environmental impact revealed the value of BOD5/COD of the wastewater produced in this combination tanning process is more than 0.3, indicating the chrome-free combination tannage based on silicic acid and plant tannin was an environment-friendly tanning technology. These findings therefore indicated that a new chrome-free tanning method with silicon and biomass materials as main tanning agents has potential practical application prospect in leather production.

中文翻译：

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一种无铬组合鞣制策略：基于硅酸和植物单宁

硅酸通常来源于廉价易得的硅酸钠，最近在皮革工业中以更清洁的方法生产生态皮革而受到极大关注。然而，单独用硅酸鞣制的皮革储存稳定性差，限制了其在皮革生产中的实际应用。在这项工作中，开发了一种基于硅酸和植物单宁的新型环保组合鞣剂，以解决这一问题，同时提高皮革的综合性能。对所得皮革进行扫描电镜、傅里叶变换红外光谱、X射线光电子能谱等表征。结果表明，与单独用硅酸鞣制的皮革相比，用这种组合方法鞣制的皮革具有改进的热稳定性、增强的机械性能、可接受的柔软度、适当的亲水性，特别是增强的储存稳定性。更重要的是，硅酸与植物单宁质量比为1:1的组合鞣革（由等量的瓦罗内阿提取物和含羞草提取物组成）的综合性能更为突出。此外，结果表明氢键在组合鞣制过程中发挥了重要作用。此外，多酚的酚羟基与硅酸分子的硅羟基之间产生的氢键抑制了Si-OH基团之间的过度缩合。随后，环境影响评价表明，该联合鞣制工艺产生的废水BOD5/COD值大于0.3，表明以硅酸和植物单宁为基础的无铬联合鞣制是一种环保鞣制技术。这些研究结果表明，一种以硅和生物质材料为主要鞣剂的无铬鞣制新方法在皮革生产中具有潜在的实际应用前景。