Selective recovery of phosphorus from the leachate of incinerated sewage sludge ash using the Zr-modified acid-leaching residue as adsorbent for two-fold resource utilization

Abstract

Phosphorus, as an essential nutrient for plant growth, is crucial for the development of agriculture. In this study, a novel strategy using a zirconium-modified acid-leaching residue adsorbent (Zr-AR adsorbent) was proposed for the efficient and selective recovery of phosphorus from incinerated sewage sludge ash (ISSA). 0.2 mol/L HCl were optimized for the phosphorus extraction from ISSA. The acid-leaching residue with large pore structure and high specific surface area was first reused as a support to prepare Zr-AR adsorbent for a twofold resource utilization of ISSA. Without removing impurities from the leachate, the Zr-AR adsorbent could selectively adsorb phosphorus with a maximum phosphorus adsorption capacity of 53.1 ± 0.8 mg/g in the HCl system. During 5 phosphorus adsorption–desorption processes, the adsorption and desorption ratios of phosphorus remained stable at over 90 %, indicating the high stability of the Zr-AR adsorbent for selective phosphorus recovery. Without adjusting the pH, hydroxyapatite was produced from the phosphorus-rich solution with a phosphorus content of 33.4 ± 1.3 % P2O5, which could significantly promote the growth of ryegrass as a phosphorus fertilizer. The cost of the phosphorus recovery from ISSA was also preliminarily evaluated ($3.76 kg-P product), demonstrating the application potential of this strategy.