纯化方式和保存条件对改性落叶松单宁絮凝性的影响

Influence of purification and storage conditions on the flocculation of modified larch tannin

选择一种典型植物多酚——落叶松单宁,研究了纯化方式和保存条件对改性植物多酚絮凝性的影响,通过测定相对黏度和红外谱图分析稳定性变化的原因.对于1 g.L-1的高岭土模拟水样,未纯化落叶松单宁改性后的最佳投加量为10 mg.L-1;经过抽滤、萃取、离心后的纯化样,改性后最佳投加量降低到1 mg.L-1,且以液体或固体形式在4℃或25℃条件下保存30 d后仍具有较好絮凝性;而只经抽滤、离心,未经萃取的纯化样,其改性产物只有保存于4℃才有絮凝性;只经抽滤、萃取,未经离心或只经抽滤的纯化样,对应改性产物只有以固体形式在4℃保存才有絮凝性.以4℃保存的固体样相对黏度变化最小,且相对黏度的变化越小,絮凝性能的稳定性越强.红外结果显示,落叶松单宁中含有大量的酚羟基基团,改性后,叔胺基团加成到芳环上,但保存前后红外谱图变化不大.

A typical plant polyphenol,larch tannin,was chosen to study the influence of purification and storage on the flocculation when it was modified as flocculant.The variability of stability was analyzed by the relative viscosity and Fourier transform infrared spectrometer（FT-IR）.The results showed that the optimum dosage of modified tannin without purification was 10mg · L^-1 to 1 g · L^-1 Kaolin suspension,whereas it achieved 1 mg · L^-1 when it was purified by filtration,extraction and centrifugation.After such purification step,the modified tannin could be stored for 30 days at 4 ℃ or 25 ℃ in either solid or liquid forms,and the flocculation ability was not affected.If tannin was purified only by filtration and centrifugation,the flocculation ability was affected obviously,unless stored at 4 ℃.However,if tannin was purified only by filtration and extraction,or only by filtration,the modified tannin lost its flocculation ability unless stored at 4 ℃ and in solid form.Additionally,if modified tannins were stored at 4 ℃ in solid form,there was little variation of their relative viscosities.The smaller the relative viscosity change,the better the stability of flocculation ability.FT-IR showed that the larch tannin contained a large number of phenolic hydroxyl groups,and the tertiary amine groups were added to the aromatic ring after modification.But there was little difference between the modified tannin before and after preservation.