In　order　to　explore　the　characteristics　and　mechanisms　of　ammonia　adsorption　by　both　nitrifying　sludge　waterborne　polyurethane　(WPU)-immobilized　pellets　and　nitrifying　sludge　polyvinyl　alcohol-sodium　alginate　(PVA-SA)-immobilized　pellets,　the　ammonia　adsorption　characteristics　of　immobilized　pellets　under　different　initial　ammonia　concentrations,　and　the　influences　of　temperature,　pH,　and　salinity　on　ammonia　adsorption　were　studied　respectively.　Moreover,　the　adsorption　isotherms,　thermodynamics,　and　kinetics　model　analysis　were　employed　to　investigate　the　adsorption　process.　The　adsorption　capacity　increased　as　the　initial　ammonia　concentration　increased.　The　optimal　pH　was　7.0,　and　salinity　and　temperature　exhibited　an　inhibitory　effect　on　adsorption.　The　adsorption　capacity　for　nitrifying　sludge-immobilized　pellets　was　higher　than　the　pellets　with　no　sludge;　the　adsorption　capacity　of　WPU　pellets　was　higher　than　that　of　PVA-SA　pellets.　The　thermodynamics　demonstrated　that　the　adsorption　process　was　a　spontaneous　exothermic　process　and　that　low　temperature　favored　ammonia　adsorption.　The　process　was　fitted　to　the　Langmuir　and　Freundlich　isotherm.　It　exhibited　multilevel　adsorption　at　higher　energy　(Freundlich　isotherm)　and　single　adsorption　at　lower　energy　by　electrostatic　force　(Langmuir　isotherm).　Additionally,　the　process　was　consistent　with　the　pseudo-second-order　kinetic　model,　as　it　explained　that　chemical　adsorption　was　the　primary　mechanism　of　ammonia　adsorption　by　immobilized　pellets.　©　2019,　Science　Press.　All　right　reserved.