From low cost template made of electrospun polyacrylonitrile fibers, highly stable boron nitride nanotube (BNNT) mat is fabricated using low temperature atomic layer deposition (ALD) of BN. Based on polymer derived ceramics chemistry, this ALD process permits preparing high quality BNNTs that show superhydrophocity, stability over a month in air and various pH conditions as well as excellent performances in water treatment. In particular, the obtained material presents high ability as separation filter for oil from aqueous phase in immiscible mixture and emulsion. The BNNT mat display also excellent renewable performances for various organic solvents and oils absorption making this unwoven material a highly promising material for efficient water purification and treatment.