PAN基双氰胺甲醛絮凝剂的制备及对染料废水的脱色性能

针对双氰胺甲醛(DDF)在对阴离子染料废水絮凝脱色中形成的絮体数量少、体积小,导致沉降性差、废水出水浊度较高的问题,以聚丙烯腈纤维(PAN)为基体接枝DDF,增大其分子质量,制得阳离子有机高分子絮凝剂PAN-DDF,黏度法测得其分子质量为1 086 718 Da,聚合度为4 347。考察了PAN-DDF投加量、沉淀时间、pH、温度对单一组分和混合组分下刚果红、酸性兰9、活性嫩黄K-6G3种染料絮凝脱色效果的影响,并使用扫描电镜和红外光谱对其表征。结果表明：在30 ℃下,在200 mL染料浓度为20 mg·L⁻¹,pH=10的模拟废水中投加20 mg PAN-DDF,沉淀30 min,脱色效果最佳。其对单一组分的刚果红、酸性兰9、活性嫩黄K-6G的脱色率分别为93.31%、84.16%、83.63%,上清液的浊度分别为1.79、2.23、1.39 NTU;对混合组分中3种染料的脱色率分别为81.74%、76.24%、62.57%,上清液的浊度为2.79 NTU。通过对比PAN接枝DDF前后扫描电镜照片,发现原光滑表面变粗糙,并附着大量颗粒物。红外光谱表征结果表明,PAN-DDF分子结构上含有—NH⁺、—$ {rm{NH}}_{rm{3}}^{rm{ + }}$、C=N⁺=C等多种活性基团。

Preparation of PAN-based dicyandiamide formaldehyde flocculant and its decolorization performance on dye wastewater

Aiming at the small quantity and volume of flocs formed by dicyandiamide formaldehyde (DDF) in flocculation and decolorization of anionic dye wastewater, resulting in poor sedimentation and high turbidity of wastewater effluent, the cationic organic polymer flocculant PAN-DDF was prepared by using polyacrylonitrile fiber (PAN) as matrix grafting DDF, increasing its molecular weight. The molecular weight measured by viscosity method was 1 086 718 Da, and the degree of polymerization was 4 347. The effects of PAN-DDF dosage, precipitation time, pH, and temperature on the flocculation and decolorization of single or mixing dyes of congo red, acid blue 9, and active yellow K-6G were investigated, respectively. The scanning electron microscopy and infrared spectroscopy were used to characterize the flocculants. The results showed that at 30 ℃, 20 mg PAN-DDF was added to 200 mL of simulated wastewater with a dye concentration of 20 mg·L−1 and pH=10, and the decolorization effect was the best after precipitation for 30 minutes. The decolorization rates of single Congo red, acid blue 9, or active bright yellow K-6G were 93.31%, 84.16% or 83.63%, respectively, and the turbidities of the supernatant were 1.79, 2.23, 1.39 NTU. For the mixed dyes, the decolorization rates of the three dyes were 81.74%, 76.24% and 62.57%, respectively, and the turbidity of the supernatant was 2.79 NTU. As observed by scanning electron images of PAN-DDF and DDF, it was found that the original smooth surface became rough and attached a lot of particles. The infrared spectrum showed that PAN-DDF molecular structure contained —NH+, —$ {rm{NH}}_{rm{3}}^{rm{ + }}$, C=N+=C and other active groups.