Patent ID: 7754099

Claim:
A method for producing a reducing water purification material, comprising the steps of: A) adding an alkaline compound to an aqueous solution of a ferrous salt to alkalinize at a pH of 7 to 11, thereby forming an iron-based precipitate; B) separating the iron-based precipitate by a solid-liquid separation and recovering the iron-based precipitate, and further adding an alkaline compound to adjust a pH between 11 to 13 to form a strong alkaline iron-based precipitate; C) adding the strong alkaline precipitate to an aqueous solution of a ferrous salt, and adjusting a pH between 7 and 11 and stirring to form a slurry; and D) separating a formed precipitate in the slurry by a solid-liquid separation to form a concentrated precipitate and repeating the steps B), C) and D) with the concentrated precipitate to obtain a reducing water purification material including an iron-based precipitate comprising a mixture of green rust and iron ferrite, or a mixture of green rust, iron ferrite and reducing iron hydroxide, wherein a ratio of divalent iron to total iron (Fe 2+ /total Fe) in the slurry is made to be 0.3 or more, and an oxidation-reduction potential of the slurry is made to be −500 mV to −800 mV versus Ag/AgCl electrode, by repeating the steps B), C) and D) while adjusting contact surface areas with an air interface.