High zeolite loading mixed matrix membrane for effective removal of ammonia from surface water

Abstract

While zeolite-based mixed matrix membrane (MMM) has been proven effective to remove the ammonia in the wastewater by adsorption, its adsorption capacity is limited by the low zeolite loading due to the need of a high concentration of polymer matrix to maintain the mechanical strength. To break the bottleneck, in this study we proposed a facile solvent evaporation method instead of conventional phase inversion method to prepare the zeolite-based MMMs. With this new preparation method, the loading of zeolite could reach up to ∼90wt.% while the MMM still maintained a good mechanical property. The zeolite-based MMM could treat 910 L·m−2 of feedwater before reaching the ammonia breakthrough point (0.5 mg-N·L−1) when treating the synthetic wastewater water. In addition, it showed a high rejection of turbidity and natural organic material (NOM) (∼90%), mainly due to its high negative surface charge density. When applied to treat real surface water, the membrane demonstrated a high normalized treatable capacity (∼900 L·m−2) with a high rejection to NOM (87.4%). Moreover, the MMM even showed a higher fouling resistance than the PVDF microfiltration membrane. Regeneration and cleaning with NaClO could efficiently recover the adsorption capacity and water flux of the MMM. After four cycles of operation, the MMM still maintained a high treatable capacity (850 L·m−2) with a high NOM rejection. This study provides a new strategy for the preparation of high-loading zeolite-based MMM for the effective removal of ammonia from surface water.