Preparation of sewage sludge-based adsorbent for ammonia gas removal

Abstract

Adsorbents derived from waste sewage sludge for ammonia gas removal were prepared by carbonization under air atmosphere and modification with H₃PO₄, H₂PO₄ or ZnCl₂. The physical properties of obtained adsorbents were characterized by thermogravimetric analysis, scanning electron microscopy and surface area analysis and the chemical properties by titration method and flame atomic absorption spectroscopy. The ammonia adsorption study was carried out in a fixed bed reactor. The surface area and the fixed carbon content of adsorbents increased after carbonization. The suitable condition for adsorbent preparation was the carbonization at 500℃ and modification with 3M of H₃PO₄, H₂SO₄ and ZnCl₂, the ammonia adsorption efficiency of the adsorbents was found to be 81.95, 90.59, 109.78 mg/g, respectively. The initial ammonia concentration and column size strongly affected the adsorption efficiency. The mechanism of ammonia adsorption on acid and ZnCl2 modified adsorbents occurred via Brønsted-Lowry acid-base reaction and the formation of ZnCl₂•NH₄Cl on surface.