Light-colored polycarboxylated polysaccharide tanning agent, and preparation method and use thereof

A light-colored polycarboxylated polysaccharide tanning agent having a carboxyl content of 5.2 mmol/g to 8.0 mmol/g, a weight-average molecular weight of 350 g/mol to 900 g/mol, and a chromaticity of 1 to 24 that is prepared by the following steps:

• preparing a polysaccharide aqueous solution with a concentration of 20% to 60% by weight;
• adding a catalyst, an organic solvent, and hydrogen peroxide to the polysaccharide aqueous solution;
• conducting an oxidation reaction at 50° C. to 90° C. for 0.5 hours to 4 hours to obtain an oxidized polysaccharide solution;
• and
• optionally adding a neutral salt to the oxidized polysaccharide solution, thoroughly stirring, then allowing a resulting mixture to stand for 30 min until an aqueous phase and an organic phase are fully separated, and discarding the organic phase with colored substances to obtain the light-colored polycarboxylated polysaccharide tanning agent,
• wherein based on a weight of the polysaccharide in the polysaccharide aqueous solution, a weight of the organic solvent accounts for 1 wt % to 15 wt %, a weight of the catalyst accounts for 0.05 wt % to 2 wt %, a weight of the hydrogen peroxide accounts for 30 wt % to 80 wt %, and a weight of the neutral salt accounts for 0 wt % to 30 wt %;
• wherein the organic solvent is at least one selected from the group consisting of tetrahydrofuran, ethyl acetate, and methyl isobutyl ketone;
• wherein the neutral salt is at least one selected from the group consisting of sodium chloride, potassium chloride, sodium sulfate, and potassium nitrate, and
• wherein the polysaccharide is one selected from the group consisting of dextrin, cellulose, and sodium carboxymethyl cellulose.