Resin composite, filter aid for water treatment, precoat material for water treatment, and water treatment method

A precoat material for water treatment, comprising a filter aid,

• wherein the precoat material is mixed with a dispersion medium to prepare a suspension of the precoat material in the dispersion medium,
• the suspension is filtered through a filter, thereby forming the precoat layer of the precoat material on the filter,
• water to be treated containing metallic ions is alkalified to precipitate water-insoluble metallic compound grains in the water to be treated,
• the water to be treated is passed through the precoat layer and the filter, whereby the precoat material captures the water-insoluble metallic compound grains contained in the water to be treated,
• a detaching water is directed to the precoat layer which has captured the water-insoluble metallic compound grains to detach the precoat layer from the filter, thereby providing a mixture of detached substance of the precoat layer and the detaching water, and
• the filter aid is magnetically separated from the mixture,
• wherein the filter aid comprises a plurality of aggregates of primary particles, each primary particle comprising a magnetic particle having a surface coated with a polymer, the primary particles have an average diameter between 0.5 μm and 20 μm, the aggregates have an average aggregate diameter greater than the average diameter of the primary particles and less than or equal to 20 μm, and the polymer has an average surface coating thickness between 0.01 μm and 0.25 μm.

A water treatment method, comprising:

• alkalifying water to be treated containing a metallic ion, thereby precipitating water-insoluble metallic compound grains in the water to be treated;
• mixing a filter aid with the water to be treated, thereby preparing a suspension of the filter aid and the water-insoluble metallic compound grains in the water to be treated,
• filtering the suspension through a filter, thereby forming a deposit layer comprising the filter aid and the water-insoluble metallic compound grains on the filter;
• directing a detaching water to the deposit layer, thereby detaching the deposit layer from the filter and providing a mixture of detached substance of the deposit layer and the detaching water;
• magnetically separating the filter aid and the water-insoluble metallic compound grains, which are contained in the mixture;
• and
• recovering the detaching water containing the separated water-insoluble metallic compound grains, and reusing the separated filter aid in subsequent mixing,
• wherein the filter aid comprises a plurality of aggregates of primary particles, each primary particle comprising a magnetic particle having a surface coated with a polymer, the primary particles have an average diameter between 0.5 μm and 20 μm, the aggregates have an average aggregate diameter greater than the average diameter of the primary particles and less than or equal to 20 μm, and the polymer has an average surface coating thickness between 0.01 μm and 0.25 μm.

A water treatment method, comprising:

• alkalifying water to be treated containing a metallic ion, thereby precipitating water-insoluble metallic compound grains in the water to be treated;
• mixing a filter aid with a dispersion medium, thereby preparing a suspension of the filter aid in the dispersion medium;
• filtering the suspension through the filter, thereby forming a precoat layer of the filter aid;
• passing the water to be treated containing the water-insoluble metallic compound grains through the precoat layer and the filter, causing the precoat layer to capture the water-insoluble metallic compound grains contained in the water to be treated;
• directing a detaching water to the precoat layer, thereby detaching the precoat layer from the filter and providing a mixture of detached substance of the precoat layer which has captured the water-insoluble metallic compound grains and the detaching water;
• magnetically separating the filter aid and the water-insoluble metallic compound grains, which are contained in the mixture;
• and
• recovering the detaching water containing the separated water-insoluble metallic compound grains, and reusing the separated filter aid in subsequent mixing,
• wherein the filter aid comprises a plurality of aggregates of primary particles, each primary particle comprising a magnetic particle having a surface coated with a polymer, the primary particles have an average diameter between 0.5 μm and 20 μm, the aggregates have an average aggregate diameter greater than the average diameter of the primary particles and less than or equal to 20 μm, and the polymer has an average surface coating thickness between 0.01 μm and 0.25 μm.