关键词: 过氧化氢, 再生纤维素, 制备, 成炭剂, 吸附

Abstract:

Hydrogen peroxide was used to oxidize pretreated regenerated cellulose to oxidized regenerated cellulose (OGC) with carboxylic content (CC) ranging from 3.2% to 15.6% depending on the H₂O₂/cellulose molar ratios used, reaction time and the pH. The structure of OGC was characterized by FT-IR, ¹³C NMR, SEM,BET and XRD. The results revealed that the primary hydroxyl at C₆ site in glucose units of regenerated cellulose was selectively oxidized to carboxyl group by H₂O₂ at the present of copper sulfate, and the notable characteristic peaks of carboxyl groups appeared at 173±2 in the spectra of ¹³C NMR. SEM revealed that the pretreated regenerated cellulose by alkali solution would increase the fiber diameter and grooves space, resulting in volume expansion of cellulose, and thereby promoting oxidation reaction. BET surface area (S_BET) and adsorption pore volume (V_p) of OGC 15.6 increased from 10.12 m²·g^-1 to 62.45 m²·g^-1 and 0.0152 cm³·g^-1 to 0.0183 cm³·g^-1, respectively. The crystallinity of OGC showed increasing with the increase of CC, which was due to partial loss of the disordered regions during the washing process because of their increased water-solubility. By TG, there was a reduction in thermal stability in parallel with the increase in CC of the samples, while exhibited high char yields. These changes could be attributed to a reduction in degree of polymerization and the increment of CC. The results demonstrated that the cellulose was selectively oxidized to carboxyl group by H₂O₂, and the properties of OC were depended on the CC. The effect of carbonization agent type on the flame retardant properties of MFAPP/EP was investigated. It revealed that when OGC15.6 (6.25%) acted as carbonization agent, the epoxy resin achieved a UL-94 V0 classification with LOI of 27.2%. The flame retardant properties of MFAPP/EP by OGC15.6 were better than those of GC and pentaerythritol. The adsorption capacity of OGC for Cu²⁺ and Pb²⁺ ions from aqueous single metal solutions was obtained by analyzing concentration determined by atomic absorption spectroscopy. These samples showed maximum adsorption capacities for Cu²⁺ and Pb²⁺ ions ranging from 4.894 to 24.426 mg·g^-1 and 5.845 to 71.833 mg·g^-1, respectively. The OGC15.6 showed larger maximum adsorption capacities than GC. The result illuminated that OGC could be applied to flame retardant EP and metal ions adsorption due to the introduction of carboxylic group.

Key words: hydrogen peroxide, oxidized regenerated cellulose, preparation, carbonization, adsorption