Metal adsorption acrylic fiber, non-woven fabric, sheet-like product, and uses thereof as metal adsorbent

A metal adsorption acrylic fiber, wherein:

• said fiber consists of an acrylonitrile-based copolymer comprising at least 85 mass % of a component unit derived from acrylonitrile and component units derived from vinyl acetate and sodium methallylsulfonate and 30-300 mass % of water relative to the mass of the acrylonitrile-based copolymer;
• and
• said fiber has a BET specific surface area of 50 to 500 m2/g, a SAG value of 2 to 20, and a strontium adsorption rate of 85% or more;
• wherein the SAG value represents an amount of acidic terminal groups in said copolymer and is determined by a measurement method comprising:
• X g of the metal adsorption acrylic fiber is dissolved in 50 ml of dimethylformamide, and passed through an ion exchange resin to give a free acid after which neutralization titration is performed with A ml of a 0.01 N potassium hydroxide/methanol solution until pH 7 is reached;
• separately, 50 ml of dimethylformamide which does not contain the metal adsorption acrylic fiber is taken as a blank and passed through the ion exchange resin after which neutralization titration is performed with B ml of a 0.01 N potassium hydroxide/methanol solution until pH 7 is reached;
• and
• the SAG value is calculated using the following equation:
• SAG value (equivalent g/g)=(A−B)/X×f×10−5
• where f=a titer of the 0.01 N potassium hydroxide/methanol solution;
• and wherein the strontium adsorption rate is measured by a measurement method comprising:
• adding 5 g of the metal adsorption acrylic fiber, which has been vacuum dried, to a 1000 mL capacity fluorine resin container, then adding 500 mL of an immersion liquid at 20° C. to the container to start immersion of the metal adsorption acrylic fiber, wherein the immersion liquid comprises an aqueous solution of strontium carbonate with a concentration of 0.1 ppm;
• agitating the container for 24 hours after the start of immersion, while maintaining a temperature of the immersion liquid at 20° C., and then collecting the immersion liquid as a test liquid;
• introducing the test liquid into an inductively-coupled plasma mass spectrometer, and quantitatively measuring a concentration of strontium C1 (ppm) in the test liquid;
• and
• adding 500 mL of the immersion liquid at 20° C., without the metal adsorption acrylic fiber, to another container to give a reference liquid, and quantitatively measuring a concentration of strontium C2 (ppm) in the reference liquid;
• wherein the strontium adsorption rate of the metal adsorption acrylic fiber is given by:
• strontium adsorption rate (%)={(C2−C1)/C2}×100.