Formaldehyde was detected in dialdehyde carboxymethyl cellulose (DCMC) tanning agent prepared through periodate oxidation of sodium carboxymethyl cellulose (CMC). Formaldehyde was then introduced into leather through DCMC tanning, which poses a potential risk to human health. The formation mechanism of formaldehyde in DCMC was investigated by composition analysis and intermediate identification of DCMC with different polymerization degrees and sugar unit structures. Formaldehyde was derived from the overoxidation of C-6 on the reducing glucose residue of CMC. Moreover, glucose was produced from the concomitant degradation of CMC during oxidation, and then oxidized to liberate formaldehyde. The low degradation degree and high degree of substitution of CMC reduced the possibility of the formation of reducing glucose residue and glucose during oxidation, thereby resulting in low formaldehyde content in DCMC and DCMC-tanned leather. These findings serve as a foundation for the minimization of formaldehyde in DCMC and the development of ecological tanning approach.

中文翻译：

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制备过程中甲醛形成二醛羧甲基纤维素鞣剂。

在通过羧甲基纤维素钠（CMC）的高碘酸盐氧化制得的二醛羧甲基纤维素（DCMC）鞣剂中检测到甲醛。然后通过DCMC鞣制将甲醛引入皮革中，这对人体健康构成潜在风险。通过不同聚合度和糖单元结构的DCMC的组成分析和中间鉴定，研究了DCMC中甲醛的形成机理。甲醛源自CMC还原葡萄糖残基上C-6的过度氧化。而且，葡萄糖在氧化过程中伴随着CMC的降解而产生，然后被氧化释放出甲醛。CMC的低降解度和高取代度降低了氧化过程中形成还原性葡萄糖残留和葡萄糖的可能性，从而导致DCMC和DCMC鞣制皮革中的甲醛含量低。这些发现为最大限度地减少DCMC中的甲醛和开发生态鞣制方法奠定了基础。