Study On Synthesis And Soulution Aggregation Behavior Of Modified Lignin-Amine Cationic Surfactants

Lignin is a natural aromatic compounds which is only less than cellulose with a three-dimensional network structure. So far, only about 6% lignin(mostly lignin sulfonate) was used effectively, and the majority is used as fuel, which don’t get high-value-added utilization. This has caused serious resources waste. People have paid more and more attention to make good use of industrial lignin as the shortage of oil resources and environmental pollution have been becoming more and more serious. So how to effectively use lignin has become a research hotspot for various countries. So far, the researches on lignin focus mainly on chemical modification, but the behaviors of its solution are relatively few. As we know, the modification of lignin and its use as surfactants in industry are all under the condition of the solution. So, it is necessary to study its aggregation behaviors.Lignin-amine cationic surfactants were synthesized via mannich reaction using sulfate lignin, diamine, diethylenetriamine and formaldehyde as raw materials in this thesis. The basic physico-chemical properties and solution aggregation behaviors of the surfactants were investigated. The main content is show as follows:1. The synthesis and characterization of lignin-amine cationic surfactants. Lignin-amine cationic surfactants were synthesized via mannich reaction in two steps in order to introduce of dehydroabietyl groups as hydrophobic groups and diethylenetriamino groups as hydrophilic groups in lignin.2. The aggregation behaviors of lignin-amine cationic surfactants were studied in dilute acidic aqueous solution. The effect of particle size, the critical aggregation concentration, surface tension, zeta potential and inorganic salt and pH of lignin-amine cationic surfactants on their aggregation behavior was characterized by zeta potentiometer, surface tensiometer, ultraviolet spectrophotometer. The results obtained showed as follows:(1) Lignin-amine solution is positively charged colloidal solution in dilute hydrochloric acid solution, and its critical aggregation concentration(CAC) is 0.10 g·L-1. Lignin amine exists mainly in single molecule when its concentration is lower than the CAC, and in multi-molecular aggregations when the concentration is over the CAC. Zeta potential of lignin-amine increased rapidly to a maximum, and then reduced slightly with increasing of the concentrations. The surface tension of the solution is 44.09 mN·m-1 when no dehydroabietyl groups were introduced, and reached 36.25 mN·m-1 after dehydroabietyl groups were introduced. This indicated surface activity increased. The apart-time of the emulsion prepared from water and toluene using lignin-amine as a surfactant is 58.3 min when the volume of water was exactly 20 ml. The foamability is 9.8 mL in initial foam volume and 6.9 mL after standing for 5 min.(2) The value of surface tension increased, zeta potential and stability decreased when the inorganic salts were added to the solution. The particle size of lignin amine decreased firstly, then increased significantly or even gathered together into larger particles to form a precipitate in lignin amine solution. The effect of salts on aggregation behaviors of lignin amine was different while the varieties, dosage and the concentration of lignin amine were changed. The effect of pH of the solution on aggregation behavior of lignin amine are the same as salts.