Nano-biochar interactions with contaminants in the rhizosphere and their implications for plant-soil dynamics

The rhizosphere hosts diverse microbes crucial for plant growth. This is because plant roots secrete organic compounds, thereby enriching the rhizosphere with essential nutrients. Biochar improves soil quality, while nano-biochar shows promise in contaminant adsorption. Its production from biochar is easily achievable through top-down methodologies including hydrothermal synthesis, ball-milling, sonication, and centrifugation. The advantages of employing nano-biochar are evident in several aspects. Nano-biochar exhibits enhanced properties such as greater surface area, increased porosity, and greater reactivity compared to bulk-biochar. This enhanced surface area allows for greater adsorption capacity, enabling nano-biochar to effectively immobilize contaminants in the environment. In this review, detailed interactions and applications of nano-biochar are summarized. Nano-biochar interacts with contaminants in the rhizosphere by electrostatic interaction, cation-π interactions and redox reactions, influencing soil microbial communities and plant resilience. Nano-biochar can adsorb contaminants from the rhizosphere, such as heavy metals and organic pollutants. Thus, it helps alleviate abiotic stresses, improves nutrient availability, and supports plant growth. Furthermore, the mechanistic processes of surface oxidation, mineral dissolution, organic matter release, and mechanical fragmentation in biochar are discussed, culminating in biochar ageing and nano-biochar formation, which creates a conducive environment for microorganisms. This review examines nano-biochar-rhizosphere interactions, highlighting their effects on plant-soil dynamics and resilience. Future research should address synthesis scalability and safety concerns to unlock nano-biochar's potential in sustainable agriculture and environmental management.