Efficient adsorption and degradation of Di-(2-ethylhexyl) phthalate (DEHP) by Nanomaterial-modified biochar: insights into microbial communities, functional genes, and metabolic pathways

Di (2-ethylhexyl) phthalate (DEHP) is a persistent pollutant that harms the environment and human health. Nanomaterial modified biochar (NMBs) significantly enhances the removal efficiency of organic pollutants due to its unique properties and structures. The aim of this research is to clarify the mechanisms of DEHP biodegradation in black soil over a 60 day incubation period, especially regarding the role of NMBs (nano-hydroxyapatite modified (NHBC), nano-zero valent iron modified (NZFBC)), including examining the involved metabolic pathways, the functional microorganisms facilitating the process, the functional genes responsible and the synergies between them. Results indicated that the impact of biochar on DEHP is multilayer adsorption and chemisorption. Among the treatments, NHBC exhibited the optimal degradation performance in black soil, it increased DEHP degradation efficiency from 17.79% (unamended original soil) to 91.12% after 60 days. NMBs addition notably raised the soil pH, soil organic matters (SOM), humus (HU), fulvic acid (FA), humic acid (HA) and enzyme activity. We identified three major metabolic pathways of DEHP enhanced by NHBC treatment ((phthalic acid (PA) to protocatechuic acid (PCA) to tricarboxylic acid (TCA) cycle), (Benzoic acid (BA) to cis-1,2-dihudroxycyclohexa-3,5-diene-1-carboxylate to TCA cycle) and (BA to Benzoate-CoA to TCA cycle). Additionally, 22 bacterial species and 55 functional genes involved in DEHP degradation under the action of NMBs, and identified 10 potential DEHP-degrading bacterias and 20 high-priority genes. The results provide a scientific basis for DEHP adsorption and biodegradation.