PROBLEM TO BE SOLVED: To provide carbon fiber for water purification which has high water purification capacity, and is also hard to be cut even by fraction with water and the weight of adhered substance.SOLUTION: In the carbon fiber for water purification, water vapor adsorption under a relative vapor pressure of 0.35 in a water vapor adsorption isotherm at 20°C is &ge；1.0 cm/g, a difference between the water vapor adsorption under a relative vapor pressure of 0.95 and the water vapor adsorption under a relative vapor pressure of 0.65 is &ge；0.50 cm/g, and also, the average short fiber strength is 5,400 to 10,000 MPa. A water purifying material having high water purification capacity can be obtained by working the carbon fiber for water purification into a flexible structural body in which the single fiber of the carbon fiber composing the same is easy to be swung in water.【課題】本発明は、高い水質浄化能力を持ち、かつ、水との摩擦や固着物の重さによっても繊維が切断されにくい水浄化用炭素繊維を提供することを目的としている。【解決手段】本発明の水浄化用炭素繊維は、２０℃での水蒸気吸着等温線において相対蒸気圧０．３５での水蒸気吸着量が１．０ｃｍ３／ｇ以上であり、相対蒸気圧０．９５での水蒸気吸着量と相対蒸気圧０．６５での水蒸気吸着量の差が０．５０ｃｍ３／ｇ以上であり、かつ、平均単繊維強度が５４００～１００００ＭＰａの水浄化用炭素繊維である。本発明の水浄化用炭素繊維を、構成する炭素繊維の単繊維が水中で揺動しやすい柔軟な組織体に加工することにより、水質浄化能力の高い水質浄化材を得ることができる。【選択図】なし
