Polyethersulfone fiber webs

A fiber web, comprising:

• polyethersulfone fibers with an average diameter of less than or equal to 250 nm and greater than or equal to 20 nm,
• wherein a relative surface area of the fiber web is greater than or equal to 80%,
• wherein the fiber web has a ratio of maximum pore size to mean flow pore size of greater than or equal to 1.2 and less than or equal to 4,
• wherein polyethersulfone makes up at least 90 wt % of the fiber web, and
• wherein the fiber web comprises a wetting agent.