Advances in Thermo-Chemical Preparation and Adsorption Mechanisms of Carbon Materials Derived from Tobacco Wastes

The rapid growth of China′s tobacco industry leads to a significant increase in tobacco production and processing, inevitably generating substantial tobacco waste. This waste poses both environmental challenges and opportunities for resource utilization. Developing clean and efficient methods to utilize these residues is essential for advancing environmental sustainability and enhancing the economic value of the tobacco industry. One promising approach is the thermochemical conversion of tobacco waste into biochar, which has gained considerable attention as a major strategy for environmental remediation. This review systematically examines the recycling of tobacco waste into biochar-based carbon materials, focusing on thermochemical preparation strategies and their adsorption mechanisms for environmental pollutants in water, air, and soil. Tobacco waste-derived biochars can be classified into three types: pristine, functionalized, and activated biochars, each with distinct physicochemical properties tailored for specific environmental applications. Functionalized and activated biochars demonstrate excellent adsorption performance for airborne contaminants and wastewater pollutants, attributed to mechanisms including electrostatic interactions, surface precipitation, cation-π interactions, ion exchange, and surface coordination. The introduction of functional groups and an increased surface area during activation or functionalization significantly enhances their adsorption capabilities. In contrast, pristine biochars primarily improve soil fertility by enhancing nutrient retention, stimulating microbial activity, and reducing the bioavailability of toxic pollutants, offering an eco-friendly solution for sustainable agriculture. The adsorption capacity of tobacco waste-derived biochars is closely linked to key physicochemical properties, including pore structure, surface functional groups, heteroatom doping, graphitization degree, and aromatic ring carbon structure. Understanding these structural characteristics allows researchers to tailor biochar properties for specific environmental applications. However, challenges remain. Precisely controlling biochar properties during thermochemical conversion and scaling up production methods are key areas needing further attention. Future studies should focus on deepening our understanding of the "preparation-structure-effect" relationship and elucidating fundamental adsorption mechanisms. A top-down strategic approach, incorporating innovative activation techniques, optimized process parameters, and hybrid biochar materials, could further enhance adsorption performance and expanding potential applications. Efficiently converting tobacco waste into high-performance adsorbents will contribute to sustainable waste management, environmental protection, and the circular economy.