Coal fly ash (CFA) was transformed to Na-P zeolite (CFA-ZP) experimentally at atmospheric pressure and low temperature (similar to 400 degrees C) via conventional hydrothermal heating followed by sonochemical energy in 4 h. The synthesized products were characterized using XRD, TGA/DTA, SEM, PSD, and BET techniques and CEC method. The effect of ultra-sonication time on crystallinity of the synthesized zeolite was studied. Crystallinity of Na-P zeolite as high as 87% was achieved at the optimum experimental conditions of NaOH/CFA of 0.27 and 1 h conventional heating followed by 3 h ultrasound irradiation. Experimental results revealed that sonochemical treatment shortened the crystallization time from 24 h to 4 h. Increasing the conventional heating time and decreasing the ultra-sonication time resulted in a lower crystallinity of the synthesized zeolite. (C) 2016 Elsevier Ltd. All rights reserved.