Porous metakaolin-based geopolymer granules for removal of ammonium in aqueous solution and anaerobically pretreated piggery wastewater

This research investigates the applicability of porous metakaolin-based geopolymer granules as an adsorbent to removal ammonium in aqueous solution and anaerobically pretreated piggery wastewater. The air foam content in porous geopolymer preparation was varied at 0, 5, 10, and 15 wt%. The porosity, water adsorption, average pore width, and total pore volume were found positively correlated with air foam content. The ammonium removal efficiency and air foam content were also positively related. The 15 wt% foamed geopolymer (GF15) provided highest ammonium removal efficiencies and adopted as the granular adsorbent. The maximum ammonium adsorption capacity of GF15 geopolymer granules was 47 mg g(-1). It was obtained at pH 6.4, 30 degrees C, 24 h contact time and initial ammonium concentration of 2000 mg L-1. The adsorption kinetic data followed the pseudo-second-order model, with adsorption equilibrium condition reached within 120 min. The GF15 geopolymer granules could be reused multiple times after desorption with 0.2 M NaCl and 0.3 M NaOH. The GF15 geopolymer granules achieved 84% ammonium removal efficiency for anaerobically pretreated piggery wastewater having 75 mg L-1 ammonium initial concentration. The results demonstrated high selectivity toward ammonium ion of the porous geopolymer granules even with the presence of organic compounds and competing ions. This research demonstrates the application of porous geopolymer granules with tailored macropore structure for effective removal of ammonium ion from piggery wastewater. (C) 2021 Elsevier Ltd. All rights reserved.