Mordenite zeolite with an average size of 17µm was synthesized hydrothermally from the gel composition of 9.4 Na2O: Al2O3:40 SiO2:1040 H2O in the absence of organic structure directing agent (OSDA) and without seed addition. The crystallinity, elemental composition, and morphology of the mordenite crystals were confirmed by XRD, EDS and FE-SEM, respectively. The impregnation with phosphate of the synthesized mordenite was achieved by suspending it in aqueous solution of 5wt.% H3PO4. The effect of the phosphorus impregnation was studied using solid-state NMR. The electrochemical behavior of phosphate mordenite zeolite was investigated in carbon paste via cyclic voltammetry. The optimized composite electrode was used for detection of thiocyanate ions.