Removal of heavy metals from Industrial brownfields by Hydrolysate from waste chicken feathers in intention of circular Bioeconomy

Contamination of soils with heavy metals is a problem which has a significant negative impact not only on the environment but also on the presence and quantity of soil bacteria; the basis of healthy soil. Currently, new types of biodegradable chelating agents which could effectively wash heavy metals from soils and would replace the used EDTA-based agents are being sought and tested. However, it would be advantageous to use waste materials in accordance with the circular bioeconomy. Therefore, the hydrolysate prepared by the thermal pressure hydrolysis of waste chicken feather initiated by malic acid containing amino acids was tested as a new ecological and cheap chelating agent for the removal of heavy metals from industrial soil. The efficiency of the heavy metal extraction during twenty-four hours was at least the same and usually higher than the EDTA-based agents, especially for Cr, Ni and mainly for As, which could not be washed out by EDTA even with extended contact times of several days. Simultaneously, it was found that the hydrolysate revealed a significant biostimulating effect on soil bacteria, whose amount increased by several orders within five days. Simultaneously, the increased number of bacteria produced biosurfactants which significantly participated in the washing out of heavy metals, thereby increasing the efficiency of the hydrolysate.