Adsorption of nitrogen and phosphorus from wastewater by modified sludge/biomass ash ceramsite: Preparation, adsorption mechanism, and sustainable analysis

Excessive ammonium and phosphate in aquatic settings may produce major eutrophication. Adsorbents can be used to reduce the eutrophication of natural water bodies. In this study, a sustainable and efficient ceramic adsorbent (sludge/biomass ash ceramsite [SBC]) was prepared by using sludge and biomass ash with a weight ratio of 1:1; the sintering parameters were 1070°C for 15 min. The NH4+ -N and P adsorption capabilities were improved by utilizing 1 mol L-1 NaOH and 1.6 mol L-1 La(NO3 )3 ·6H2 O for modification. When the pH and duration were 7 and 1440 min, respectively, the maximum bending capacity of ammonia nitrogen and phosphorus was 3.2 and 2.1 mg g-1 at 308 K. The pseudo-second-order kinetic model better describes the adsorption dynamics of NH4+ -N and P, whereas the Langmuir model better describes the adsorption isotherm models of NH4+ -N and P. The adsorption mechanism of SBC-NaOH on NH4+ -N is ion exchange between Na+ and NH4+ , whereas the adsorption mechanism of SBC-La on phosphorus is ion exchange and La3+ adsorption. SBC combines efficient wastewater purification with the reuse of solid waste. The findings gave rise to the possibility of recycling ceramics as a plant fertilizer with a delayed release in the future. PRACTITIONER POINTS: New ceramsite was made from sludge and biomass ash. NH4+ -N (3.2 mg g-1 ) and P (2.1 mg g-1 ) were effectively adsorbed by ceramsite. The mechanism of NH4+ -N and P adsorption by ceramsite was studied. Absorbed ceramsite can be used as slow-release fertilizer in plant cultivation.