Phytotoxicity of sewage sludge passivated by modified potassium feldspar and its effect on ryegrass growth

Effective passivation of heavy metals in sludge is the key to achieve its land use. Potassium feldspar was modified to obtain GxK900, with a lower crystallinity, a higher specific surface area and cationic exchange capacity. GxK900 was chosen to passivate heavy metals in the sludge, and the best passivation conditions were 30% addition and a 10-day passivation period. The passivated sludge extract had no adverse effects on ryegrass germination and promoted radicle growth. The pot experiment revealed that adding 10% passivated sludge encouraged ryegrass growth while having no appreciable impact on the contents of Cu, Cr, Zn and Pb in the roots and above-ground parts compared to control treatment. The transfer factors of the four metals were all less than 1. Passivated sludge was used as a growing medium for landscaping plants, which provided a theoretical foundation for sludge land use and a resource outlet for potassium feldspar minerals.

Automated summary

Effective passivation of heavy metals in sludge is crucial for its land use. GxK900, a modified potassium feldspar with lower crystallinity, higher specific surface area, and cationic exchange capacity, was chosen to passivate heavy metals in the sludge. The optimal passivation conditions were 30% addition and a 10-day passivation period. The passivated sludge extract had no adverse effects on ryegrass germination and promoted radicle growth. The pot experiment showed that adding 10% passivated sludge enhanced ryegrass growth without significantly affecting the contents of Cu, Cr, Zn, and Pb in the roots and above-ground parts. The transfer factors of the four metals were all less than 1. The use of passivated sludge as a growing medium for landscaping plants provides a theoretical basis for sludge land use and a resource outlet for potassium feldspar minerals.