Polysaccharides from Agro-Industrial Waste and By-Products: An Overview on Green Synthesis of Metallic Nanoparticles—An Ecofriendly Approach

This review explores the eco-friendly synthesis of metallic nanoparticles derived from polysaccharides obtained from agricultural and food industry waste. Initially, it outlines the problem of agri-food waste, highlighting its abundance and the potential to extract valuable polysaccharides such as cellulose, hemicellulose, lignin, and pectin. The focus is on green synthesis methods that use these polysaccharides to produce metallic nanoparticles, emphasizing the environmental benefits compared to conventional methods. The article reviews the physicochemical properties of key polysaccharides and details their extraction processes from various agricultural waste. The synthesis of diverse types of metallic nanoparticles, including monometallic (e.g., gold, silver, and platinum), bimetallic (e.g., gold–silver and gold–zinc), and oxide nanoparticles (e.g., zinc oxide and iron oxide), is extensively covered. Additionally, mechanisms of nanoparticle synthesis, such as nucleation, growth, stabilization, and capping, are examined, alongside examples from existing research. The article highlights the applications of these nanoparticles in diverse fields, including food safety, healthcare, agriculture, and environmental protection. It concludes by underscoring the potential of green synthesis to reduce waste and promote sustainable industrial practices and calls for further research to optimize these methods.