Modified red soil for removing cyanobacteria and preparation method

The invention discloses modified red soil for removing cyanobacteria. The modified red soil comprises raw materials in percentage as follows: red soil, polyepichlorohydrin-dimethylamine, polymeric ferric sulfate and water. A preparation method of the modified red soil comprises steps as follows: 1, weighing out the polyepichlorohydrin-dimethylamine, and diluting the polyepichlorohydrin-dimethylamine with water through stirring to obtain a polyepichlorohydrin-dimethylamine mother solution; 2, weighing out the polymeric ferric sulfate, and diluting the polymeric ferric sulfate with water to obtain a polymeric ferric sulfate mother solution; 3, weighing out the red soil, and dissolving the red soil after drying and grinding to obtain a red soil mother solution; 4, adding the polyepichlorohydrin-dimethylamine mother solution and the polymeric ferric sulfate mother solution to the red soil mother solution, and diluting the mixture with water to obtain the modified red soil. According to the modified red soil, the polyepichlorohydrin-dimethylamine and the polymeric ferric sulfate are used as flocculating agents, the red soil is used as a flocculation aid, and active aluminium and active iron, which are higher in content, of the red soil are used as coagulants, so that the cyanobacteria removal rate is increased, and secondary pollution cannot be caused after the cyanobacteria are removed. The preparation method is simple, low in cost and simple to operate.