Study on the solidification performance and mechanism of heavy metals by sludge/biomass ash ceramsites, biochar and biomass ash.

Industrial by-products are stored in large quantities in the open, leading to wasted resources and environmental pollution, and the natural environment is similarly faced with phosphate depletion and serious water and soil pollution. This study uses these by-products to produce a new sludge/biomass ash ceramsite that will be used to adsorb nitrogen and phosphorus from wastewater, and solidify heavy metals in the soil while releasing Olsen P. The sludge/biomass ash ceramsites are made using sewage sludge and biomass ash in a certain ratio calcined at high temperatures and modified for the adsorption of nitrogen and phosphorus from wastewater. Sludge/biomass ash ceramsites before and after phosphorus adsorption, biochar and biomass ash were compared to analyze their heavy metal adsorption capacity and potential as phosphate fertilizer. After phosphorus adsorption, the sludge/biomass ash ceramsites released effective phosphorus steadily and rapidly in the soil, with a greater initial release than biochar and biomass ash, and the ceramsites were in a granular form that could be easily recycled. Biochar and biomass residue, due to their surface functional groups, are better at solidifying heavy metals than sludge/biomass ash ceramsites. Biochar, biomass ash and sludge/biomass ash ceramsites significantly reduced the concentrations of Cd, Cu, Pb and Zn in the soil. Correlation analysis demonstrated that there was a synergistic relationship between the increase in soil Olsen P content and the change in pH, with the increase in soil Olsen P content and the increase in pH contributing to heavy metal solidification.

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.