Filter and metal ion removal device

A depth filter comprising

• a porous molded article being a sintered material of mixed powder or a swollen material of the sintered material, the mixed powder containing dried gel powder including an ion exchange resin, and thermoplastic resin powder, wherein
• an average particle diameter of the dried gel powder is two or more times as large as an average particle diameter of the thermoplastic resin powder, and
• when each of a surface of the porous molded article and a cross-sectional surface dividing the porous molded article into two in a thickness direction is observed with a scanning electron microscope in a range of a field of view of 950 μm×950 μm and subsequently an average projected area of five particles having large projected areas of the dried gel powder is calculated in each field of view,
• the average projected area on the surface is smaller than the average projected area on the cross-sectional surface.

A metal ion removal device comprising:

• a first filter;
• and
• a second filter configured to remove metal ions from a treatment liquid that has passed through the first filter, wherein
• the first filter is a filter including a porous molded article, the porous molded article being a sintered material of mixed powder or a swollen material of the sintered material, the mixed powder containing dried gel powder including a nitrogen-containing chelating resin, and thermoplastic resin powder, and
• the second filter comprising
• a porous molded article being a sintered material of mixed powder or a swollen material of the sintered material, the mixed powder containing dried gel powder including an ion exchange resin, and thermoplastic resin powder, wherein
• the ion exchange resin is an ion exchange resin including a sulfonic acid group, and the dried gel powder further includes a nitrogen-containing chelating resin,
• a ratio (C1/C2) of a content C1 of the ion exchange resin to a content C2 of the nitrogen-containing chelating resin is 0.1 or more and 100 or less in a mass ratio,
• a number of particles of powder P1 contained on a surface per unit area is smaller than a number of particles of powder P2 contained on a cross-sectional surface per unit area, the surface being a surface of the porous molded article, the cross-sectional surface being a surface dividing the porous molded article into two in a thickness direction, where, among particles of the dried gel powder, P1 denotes a particle of powder having a projected area 10 or more times as large as an average projected area of a particle of the thermoplastic resin powder, the projected area of the particle of the powder P1 being an area on the surface, and P2 denotes a particle of powder having a projected area 10 or more times as large as an average projected area of a particle of the thermoplastic resin powder, the projected area of the particle of the powder P2 being an area on the cross-sectional surface, and
• the first filter is a filter configured such that, when water having a specific electrical resistance value of 18 MΩ·cm or greater is caused to pass through the first filter at a space velocity of 1200 1 hr−1, a specific electrical resistance value of the water after being caused to pass through the first filter is less than 15 MΩ·cm.