Chlorine-free lignosulfonate as well as preparation method and application thereof

The invention discloses chlorine-free lignosulfonate as well as a preparation method and application thereof, and relates to the technical field of biochemical engineering. The preparation method specifically comprises the following steps: (1) adding alkali into production water at the temperature of 75-85 DEG C to adjust the pH value to 12-13; (2) adding wood powder into the production water after the pH value is adjusted, and stirring at a constant temperature; and (3) adding industrial anhydrous sodium sulfite into the solution obtained in the step (2), and stirring at a constant temperature to finish the operation. According to the method, the lignosulfonate solution without chloride ions is extracted, the lignosulfonate solution is suitable for being used as a dispersing agent for oxygen pressure leaching of the zinc sulfide concentrate, chloride ions brought into an all-wet-process zinc system are reduced, and the pressure of chloride ion removal of the all-wet-process zinc smelting system is relieved.