Uranium (U) resources play a crucial role in energy utilization; however, uranium contamination in wastewater and soil has caused severe damage to the ecosystem and human health. Addressing this challenge requires the development of cost-effective and environmentally sustainable remediation materials. This review highlights the environmental merits of biochar-based materials in uranium decontamination, focusing on the diverse applications of modification techniques for enhancing the properties of pristine biochar. By analyzing over 110 relevant studies, the review demonstrates that biochar derived from various biomass sources, with proper modification, could exhibit high adsorption capacities for immobilising uranium in aqueous and soil environments. The primary removal mechanisms identified include physical adsorption and chemical reduction. These works indicate that biochar, produced from green feedstocks and featuring superior reusability, represents a cost-effective, sustainable solution for uranium remediation. Moreover, its application aligns with carbon sequestration and waste valorization, supporting sustainable development goals. Looking ahead, the engineering performance-oriented biochar materials with tailored physicochemical properties hold significant promise for addressing uranium contamination challenges. This review provides a comprehensive evaluation of biochar-based materials as a green alternative for uranium remediation and offers valuable insights into advanced material modification strategies to enhance reactivity and effectiveness.

Soil salinization is a major factor threatening global food security. Soil improvement strategies are therefore of great importance in mitigating the adverse effect of salt stress. Our study aimed to evaluate the effect of biochar (BC) and nitric acid-modified biochar (HBC) (1%, 2%, and 3%; m/m) on the properties of salinized soils and the morphological and physiological characteristics of pakchoi. Compared with BC, HBC exhibited a lower pH and released more alkaline elements, reflected in reduced contents of K+, Ca2+, and Mg2+, while its hydrophilicity and polarity increased. Additionally, the microporous structure of HBC was altered, showing a rougher surface, larger pore size, pore volume, specific surface area, and carboxyl and aliphatic carbon content, along with lower aromatic carbon content and crystallinity. Moreover, HBC application abated the pH of saline soil. Both BC and HBC treatments decreased the sodium absorption rate (SAR) of saline soil as their concentration increased. Conversely, both types of biochar enhanced the cation exchange capacity (CEC), organic matter, alkali-hydrolyzable nitrogen, and available phosphorus and potassium content in saline soils, with HBC demonstrating a more potent improvement effect. Furthermore, biochar application promoted the growth-related parameters in pakchoi, and reduced proline and Na+ content, whilst increasing leaf K+ content under salt stress. Biochar also enhanced the activity of key antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) in leaves, and reduced hydrogen peroxide (H2O2) and malondialdehyde (MDA) content. Collectively, modified biochar can enhance soil quality and promote plant growth in saline soils.