Methanol/CaCl2 Wet Phase Inversion for Selective Separation of Heavy Metal Ions by Nylon 6-Mordenite Zeolite Composite Membranes

Abstract

Nylon 6-mordenite composite membranes having porous morphology were applied to the selective separation of heavy metal ions from aqueous heavy metal solution with Pb2+, Cu2+ and Cd2+. The membrane preparation was carried out in the wet phase inversion method using methanol/CaCl2/Nylon 6 solution. The resultant membranes containing mordenite powders with 10, 20 and 30 wt% loading were obtained as coagulated in water. Depending on the mordenite loading in the composite membranes, the porous morphology was changed in a finger-like and/ or sponge structure. In batch adsorption experiments, the higher mordenite loading in the composite membranes was the higher separation capacity for heavy metal ions. The composite membrane loading 30 wt% mordenite (NZC 30) had the optimal performance of Pb2+ ion capture in the maximum adsorption capacity of 38.5 mg/g at pH 5. The batch separation factor calculated using Langmuir isotherm parameters supported the selective adsorption of Pb2+ relative to those of Cd2+ and Cu2+. In addition, the permeabilities of water and the mixed ion solution with 20 mg/L concentration were investigated. The value of the separation factor of NZC 30 was 9.2 for Pb2+ against Cu2+. In the regeneration of the reused membranes, the values of the regeneration efficiency of NZC 30 still maintained a good separation performance in Pb2+ with 24.1 mg/g at 5-time reusing. Porous nylon 6-mordenite composite membranes were fabricated from methanol/CaCl2/Nylon 6 solution via the wet phase inversion method and applied to selective separation of Pb2+, Cu2+ and Cd2+ from mixture solution