Method for preparing high-purity nicotine from waste and inferior tobaccos

The invention discloses a method for preparing high-purity nicotine by using waste and inferior tobacco, which comprises the following steps: drying and crushing the waste and inferior tobacco, adding a dilute acid solution A for heating and extracting, and performing coarse filtration to obtain filtrate; performing membrane filtration treatment on the filtrate to obtain a nicotine salt concentrated solution; adjusting the pH value of the nicotine salt concentrated solution to 11-13 by using an alkali solution A, carrying out reduced pressure distillation, absorbing distillate by using a dilute acid solution B, and then carrying out membrane molecule interception treatment to obtain nicotine salt with the purity of 35-45%; then adding an alkali solution B to adjust the pH value to 11-13, then adding an organic solvent for extraction, and collecting an organic solvent extract; and carrying out reduced pressure distillation on the organic solvent extraction liquid by adopting a rectifying column system, and res