Preparation, regeneration and application of a chelating microfiltration membrane

1. A preparation method of a chelating microfiltration membrane, comprising:

A. preparing a polyvinylidene fluoride flat sheet membrane: adding 70-90 parts of a solvent into a reactor, then adding 4-22 parts of a pore-forming agent and 6-16 parts of polyvinylidene fluoride, then dissolving completely to form a casting membrane solution; stirring and reacting the casting membrane solution for 1-44 h in the reactor, wherein the reaction temperature is controlled at 50-100° C.; wherein the casting membrane solution, after being settled and defoamed, is shaped as a diaphragm by employing a thermally induced phase separation process; soaking the diaphragm in distilled water for 1-3 h, and finally drying to produce a polyvinylidene fluoride PVDF flat sheet membrane;

B. defluorination: adding the polyvinylidene fluoride flat sheet membrane obtained in step A and a low concentration alkaline potassium permanganate solution to the reactor, wherein a mass ratio of the flat sheet membrane and the alkaline potassium permanganate solution is 1:20-1:50, with a temperature controlled at 10-100° C., performing the reaction for 1-25 h, and then washing and drying to obtain a defluorinated flat sheet membrane;

C. grafting glycidyl methacrylate: adding the deflourinated flat sheet membrane obtained in step B and a solution of glycidyl methacrylate at a concentration of 0.5-5% to the reactor, wherein a mass ratio of the deflourinated flat sheet membrane and the solution of glycidyl methacrylate is 1:20-1:50, then adding an initiator and a polymerization inhibitor, wherein the temperature is controlled at 10-120° C., and the reaction is performed for 1-25 h, and then washing and drying to obtain a grafted flat sheet membrane;

D. melamine modification: adding the grafted flat sheet membrane obtained in step C and a solution of melamine at a concentration of 0.1-5.0% to the reactor, wherein a mass ratio of the grafted flat sheet membrane and the solution of melamine is 1:20-1:50, with the temperature controlled at 10-120° C., performing the reaction for 1-36 h, and then washing and drying.

2. The preparation method of a chelating microfiltration membrane according to claim 1 , wherein the solvent in step A is one selected from the group consisting of N-methyl pyrrolidone, N,N-dimethyl acetamide, trimethylolpropane, dimethyl phthalate, and triethyl phosphate.

3. The preparation method of a chelating microfiltration membrane according to claim 2 , wherein the pore-forming agent in step A is one selected from the group consisting of polyethylene glycol and polyvinyl pyrrolidone.

4. The preparation method of a chelating microfiltration membrane according to claim 3 , wherein a mass fraction of the alkaline potassium permanganate solution in step B is 0.5-5%.

5. The preparation method of a chelating microfiltration membrane according to claim 4 , wherein the solvent in the solution of glycidyl methacrylate in step C is one selected from the group consisting of methanol, ethanol, n-propanol, isopropanol and toluene.

6. The preparation method of a chelating microfiltration membrane according to claim 5 , wherein the initiator in step C is one selected from the group consisting of 2,2-azoisobutyronitrile, ammonium persulfate, potassium persulfate, and benzoyl peroxide, with a concentration of 0.01-0.05%.

7. The preparation method of a chelating microfiltration membrane according to claim 6 , wherein the polymerization inhibitor in step C is one selected from the group consisting of methylhydroquinone, p-hydroxyanisole, and 2-tert-butylhydroquinone, with a concentration of 0.01-0.05%.

8. The preparation method of a chelating microfiltration membrane according to claim 1 , further comprising a regeneration process including soaking the chelating microfiltration membrane in a solution of hydrochloric acid, nitric acid or sulfuric acid at 0.001-1.0 M for 1-72 h and then soaking and washing in deionized water for 1-72 h.