Hainan, et al (2024) Responses of nitrobenzene removal performance and microbial community by modified biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More supported zerovalent iron in anaerobic soil. Scientific Reports. https://doi.org/10.1038/s41598-024-67301-5

Nitrobenzene, a prevalent industrial chemical used in pharmaceuticals, dyes, and pesticides, poses significant environmental risks when it contaminates soil and groundwater. Given its high toxicity and persistence, effective remediation methods are crucial. Recently, modified biochar-supported zero-valent iron (ZVI) composites have shown promise in removing nitrobenzene from anaerobic soil environments.

The study focuses on the nitrobenzene removal performance of these composites, particularly those modified at different temperatures and with various chemicals. Biochar, a carbon-rich material derived from biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More, provides a large surface area and functional groups that support the dispersion of ZVI particles, enhancing their reactivity. By modifying biochar with substances like sodium hydroxide (NaOH), hydrochloric acid (HCl), and nitric acid (HNO3), researchers aimed to improve its effectiveness in contaminant removal.

The experiments revealed that biochar pyrolyzed at 700°C (referred to as 700°C biochar) outperformed biochar pyrolyzed at 300°C. The 700°C biochar composite enhanced nitrobenzene removal efficiency, achieving a 64.4% removal rate with NaOH modification (NaOH-700-Fe50). In contrast, the 300°C biochar composite inhibited nitrobenzene removal.

The key mechanism driving nitrobenzene removal in this context was microbial degradation, rather than direct chemical reduction by ZVI. The biochar-ZVI composites significantly altered the soil microbial communities, increasing their richness and diversity. This change was beneficial, as higher microbial diversity can lead to more stable ecosystems capable of resisting environmental stresses. Specifically, ZVI enhanced the symbiotic relationships among microbial genera while reducing competition, fostering an environment conducive to nitrobenzene degradation.

Further analysis indicated that the modified biochar composites not only increased the microbial community’s capacity to degrade nitrobenzene but also upregulated genes associated with electron transfer processes, crucial for microbial respiration and contaminant breakdown. This dual enhancement of microbial activity and genetic expression underlines the potential of biochar-ZVI composites in environmental remediation.

The study’s findings suggest that NaOH-700-Fe50 is a particularly promising composite for in-situ remediation of nitrobenzene-contaminated groundwater. Its effectiveness lies in its ability to inhibit nitrobenzene desorption from soil, thereby preventing the contaminant from entering the aqueous phase and facilitating its degradation within the soil matrix.

Overall, the research highlights the significant potential of biochar-supported ZVI composites, especially those modified at higher pyrolysis temperatures, in enhancing soil and groundwater remediation efforts. By leveraging the synergistic effects of biochar’s physical properties and ZVI’s chemical reactivity, coupled with microbial community dynamics, these composites offer a robust solution for tackling nitrobenzene pollution in anaerobic environments.