Nutrient recovery from urine: Urea adsorption onto biochar integrated with Na-chabazite as urease inhibitor
Haotian Wu, Xavier Foster, Hossein Kazemian, Igor Cauphy Peggy Diby, Serge Kaliaguine, Céline Vaneeckhaute
Abstract
This study presents an innovative technical integration for concomitant nutrient recovery from source-separated urine. While cation exchange is known for efficient K + recovery, it faces competition due to the high molarity of NH 4 + in hydrolyzed urine. This study proposes inhibiting urease activity to facilitate the recovery of K⁺ and urea from fresh urine. Na-chabazite was first proposed as a urease inhibitor in this study, reducing urease activity by 50 %. Wood biochar, with its high porosity (308.0 m²/g) and polar functional groups, shows a urea adsorption capacity of 25.4 mg/g, which can be further improved by steam activation. The isotherm analysis suggests that urea adsorption onto biochar follows a multi-layer adsorption process. Finally, an integrated process is suggested: "Na-chabazite and Biochar adsorption → urea hydrolysis → struvite precipitation + ammonia stripping-acid scrubbing", ensuring efficient recovery of urea, NH 4 + , PO 4 3- , and K + from source-separated urine.