Separation method of water-soluble polymer with tetrahydrofuran as extracting agent

The invention discloses a separation method of a water-soluble polymer with tetrahydrofuran as an extracting agent. The preparation method comprises the following steps: firstly, at temperature of 20-30 DEG C, adjusting a pH value of a reaction solution containing a water-soluble polymer, obtained through a polymerization reaction, to be neutral, adding sulfate to the reaction solution to form a sulfate solution; adding tetrahydrofuran to the obtained sulfate solution, calculating according to a volume ratio, i.e. a ratio of the sulfate solution to the tetrahydrofuran of 1:(0.25-2); standing and demixing after oscillating, wherein the upper layer is an organic-phase tetrahydrofuran phase, the lower layer is a water phase-phase sulfate solution; then separating the obtained tetrahydrofuran by using a separating funnel to obtain a tetrahydrofuran solution rich in water-soluble polymer, performing reduced pressure distillation in a water bath with temperature of 50-70 DEG C by using a rotary evaporator, and evaporating a tetrahydrofuran solvent to obtain the water-soluble polymer, thus realizing the separation of the water-soluble polymer with the tetrahydrofuran as the extracting agent.