The present invention relates to methods and apparatuses for water filtration comprising contacting a water stream with a membrane comprising a polysulfone having structural units of Formula I wherein X is OH, NR1R2, or OR3; R1 and R2 are independently at each occurrence hydrogen, a C1-C5000 aliphatic radical, a C3-C12 cycloaliphatic radical, a C3-C12 aromatic radical, a polypeptide, a combination thereof, or R1 and R2 taken together form a 5- or 6-membered aliphatic ring or a 5-membered aromatic ring; R3 is a C1-C20 aliphatic radical, C3-C12 cycloaliphatic radical, C3-C12 aromatic radical, or a combination thereof; B′ and C′ are independently at each occurrence a nitro group, C1-C20 aliphatic radical, C3-C12 cycloaliphatic radical, C3-C12 aromatic radical, or a combination thereof; and q and r are independently at each occurrence 0 to 4. The present invention also relates to a method and apparatus for gas separation, the method comprising contacting a gas stream with a membrane comprising a polysulfone having structural units of Formula I.