Synthesis of Na-A zeolite from water treatment residue using hydrothermal and microwave techniques

Abstract

Na-A zeolite was synthesized from water treatment residue (WTR) using hydrothermal and microwave techniques. WTR was brought from Metropolitan Waterworks Authority (Thailand) and was activated by firing at 700 °C for 3 h in an electric furnace. The activated WTR was reacted with 3 M NaOH solution in a reactor under a controlled temperature of 80, 90 and 100 °C for 8, 10, 12, and 14 h. SEM (Scanning electron microscopy) images reveal the cubic crystal of zeolite. The highest cation exchange capacity (CEC) was obtained from sample synthesized at 90 °C for 14 h and gave the CEC value of 3.14 meq/g Ca2+. For the microwave technique, the raw materials were reacted at 80 90 and 100°C for 30, 60, and 120 min. Results showed that the sample obtained at 80 °C for 30 min represented the highest CEC value of 0.29 meq/g Ca2+.