Two benign methods to fabricate water-resistant HA nanofibrous membranes without the use of reactive chemical agents were demonstrated: (a) the exposure of HA membranes in hydrochloric acid (HCl) vapor, followed by a freezing treatment at −20 °C for 20–40 days; and (b) the immersion of HA membranes in an acidic mixture of ethanol/HCl/H2O at 4 °C for 1–2 days