This exploration unveils a revolutionary strategy for phosphorus recovery from incinerated sewage sludge ash (ISSA) using a Zr-modified rice-husk biochar (Zr-RB) adsorbent. The method selectively recovers high-purity AlPO4 products, commencing with the extraction of phosphorus from ISSA using 0.1 mol/L H2SO4 and achieving a phosphorus extraction of 54.5 ± 1.6 mg/g.

The Zr-RB adsorbent displays remarkable capabilities, attaining a maximum phosphorus adsorption capacity of 53.1 ± 0.6 mg/g. The adsorption kinetics follow the pseudo-second order model, suggesting chemisorption processes. Even after five adsorption-desorption cycles, the Zr-RB adsorbent maintains high stability, indicating its potential for long-term use.

The adsorption mechanism involves electrostatic attraction and ligand exchange on the Zr-RB adsorbent, efficiently capturing phosphorus from the complex leachate. Notably, the study achieves the production of high-purity AlPO4 products at pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More = 3.0 without the need for additional substances, highlighting the efficiency and sustainability of the Zr-RB adsorbent.

In light of the global phosphorus crisis and the substantial phosphorus content in ISSA, this innovative approach offers a promising solution. Unlike traditional methods, the Zr-RB adsorbent eliminates the need for extensive pretreatment processes, making it a cost-effective and environmentally friendly option for phosphorus and aluminum recovery. The study’s findings contribute to the development of a comprehensive strategy for selective phosphorus recovery, addressing the critical need for sustainable phosphorus resources in the face of depleting phosphate rock reserves.