The present invention provides a porous carbon fiber which has an excellent permeation amount and excellent pressure resistance, which is prevented from the occurrence of detachment or cracking at an interface, and which can exhibit excellent properties needed for use as a support for a fluid separation membrane. The present invention is a porous carbon fiber having a bicontinuous porous structure, wherein

the average value R.sub.ave of the R value of the outer surface and the R value of the inside is 1.0 or more and 1.8 or less,

the absolute value ΔR of the difference between the R value of the outer surface and the R value of the inside is 0.05 or less, and

R value is a carbonization progression degree calculated from a Raman spectrum in accordance with the following formula:

R value=(intensity of scattering spectrum at 1360 cm.sup.−1)/(intensity of scattering spectrum at 1600 cm.sup.−1).

A method of producing a sulfonated polymer. The method includes providing a source for a quantity of a polymer containing polymer fibers. The quantity of the polymer is heated while immersed in sulfuric acid to 100-200° C. for a period time in a closed reactor containing an atmosphere and capable of holding pressure generated by a reaction between the quantity of the polymer and the sulfuric acid resulting in a sulfonated polymer, wherein substantially all the quantity of the polymer from the source is converted into sulfonated polymer. The sulfonated polymer is then removed from the reactor and dried. An electrode suitable for use as an electrode in an electrochemical energy storage cell is disclosed. The electrode contains amorphous porous carbon fibers made from a sulfonated polymer with a morphology wherein the amorphous porous carbon fibers have the morphology of the sulfonated polymer from which they are made.

A method of producing a sulfonated polymer. The method includes providing a source for a quantity of a polymer containing polymer fibers. The quantity of the polymer is heated while immersed in sulfuric acid to 100-200° C. for a period time in a closed reactor containing an atmosphere and capable of holding pressure generated by a reaction between the quantity of the polymer and the sulfuric acid resulting in a sulfonated polymer, wherein substantially all the quantity of the polymer from the source is converted into sulfonated polymer. The sulfonated polymer is then removed from the reactor and dried. An electrode suitable for use as an electrode in an electrochemical energy storage cell is disclosed. The electrode contains amorphous porous carbon fibers made from a sulfonated polymer with a morphology wherein the amorphous porous carbon fibers have the morphology of the sulfonated polymer from which they are made.

A carbon fiber wherein an average fiber diameter of a single fiber is in a range of 3 to 10 μm, and an average value of an intensity ratio (D/G) of a D peak to a G peak in a Raman spectrum in a cross section perpendicular to a fiber axis direction of the single fiber is 0.90 or less in a region inside a circle having a diameter of 1 μm and centered at a center of gravity of the cross section of the single fiber, and is 0.90 or less in a region up to 1 μm inside from an outer periphery of the cross section of the single fiber, wherein the D peak is observed at around 1360 cm.sup.−1 and derived from a defect in a graphite structure and the G peak is observed at around 1590 cm.sup.−1 and derived from the graphite structure.

An embodiment is a method of recycling carbon fibers that includes: preparing a carbon fiber reinforced plastic formed product that includes a carbon fiber reinforced plastic containing a carbon fiber and a resin; thermally decomposing or dissolving the resin in the carbon fiber reinforced plastic formed product by a first heating process or a first dissolving process; and winding while drawing the carbon fiber from the carbon fiber reinforced plastic formed product after the first heating process or the first dissolving process. The winding further includes thermally decomposing or dissolving a residue of the resin attached to the carbon fiber by a second heating process or a second dissolving process and adding a sizing agent to the carbon fiber after the second heating process or the second dissolving process.

An embodiment is a method of recycling carbon fibers that includes: preparing a carbon fiber reinforced plastic formed product that includes a carbon fiber reinforced plastic containing a carbon fiber and a resin; thermally decomposing or dissolving the resin in the carbon fiber reinforced plastic formed product by a first heating process or a first dissolving process; and winding while drawing the carbon fiber from the carbon fiber reinforced plastic formed product after the first heating process or the first dissolving process. The winding further includes thermally decomposing or dissolving a residue of the resin attached to the carbon fiber by a second heating process or a second dissolving process and adding a sizing agent to the carbon fiber after the second heating process or the second dissolving process.

The present invention relates to a method for producing hollow activated carbon nanofibers for activating peroxymonosulfate used in water purification; a catalyst for water purification comprising the hollow active carbon nanofibers produced by the method; and a method for purifying contaminated water using the catalyst. The production method of the present invention can easily produce hollow activated carbon nanofibers capable of rapidly purifying contaminated water by highly efficiently activating peroxymonosulfate used for water purification.

The present invention relates to a method for producing hollow activated carbon nanofibers for activating peroxymonosulfate used in water purification; a catalyst for water purification comprising the hollow active carbon nanofibers produced by the method; and a method for purifying contaminated water using the catalyst. The production method of the present invention can easily produce hollow activated carbon nanofibers capable of rapidly purifying contaminated water by highly efficiently activating peroxymonosulfate used for water purification.

The disclosure relates to a method of making carbon fiber, the method comprising pyrolyzing poly(p-phenylene) (PPP) fiber at a temperature sufficient to convert PPP fiber substantially to carbon fiber. The disclosure also relates to pre-PPP polymer, methods for making PPP fiber from pre-PPP polymer and, in turn, making carbon fiber from PPP fiber.

The disclosure relates to a method of making carbon fiber, the method comprising pyrolyzing poly(p-phenylene) (PPP) fiber at a temperature sufficient to convert PPP fiber substantially to carbon fiber. The disclosure also relates to pre-PPP polymer, methods for making PPP fiber from pre-PPP polymer and, in turn, making carbon fiber from PPP fiber.