Silver–Biochar Nanocomposites for Sustainable Escherichia coli Disinfection: A Review

Abstract

Water contamination by pathogenic microorganism remains a critical global health concern, especially in decentralized and resource limited regions. Among various waterborne pathogens, Escherichia coli is considered as a threat due to its ability to cause various diseases like diarrhea, hemorrhagic colitis, hemolytic uremic syndrome and septicemia. Even though conventional disinfection methods are effective, they have been limited by high energy requirement, operational complexity and formation of secondary pollutant. To overcome these, biochar‐based metal composites have emerged as sustainable alternatives for water disinfection. This review critically evaluates the past 5 years (2020–2025) development of silver–biochar composites for E. coli inactivation. Various preparation methods such as chemical, carbothermal, and phyto reductions are discussed in relation to nanoparticle dispersion, stability and antibacterial activity. This review highlights the high efficiency of Ag–biochar composites rose from synergetic mechanisms including metal ion release, reactive oxygen species (ROS) generation and bacterial adsorption. Furthermore, emerging bimetallic composites shows significantly enhanced antibacterial activity through charge separation and rapid ROS generation. This review provides a mechanistic and comparative framework that correlates preparation methods with antibacterial activity, stability and metal leaching, which are overlooked in existing literature. In addition, it critically evaluates the challenges related to reproducibility, scalability, and real‐water application.