Biochar modification has received significant research attention due to its attractive and fruitful rewards in improving biochar performances. However, the determinants of modified biochars’ stability and the ability of aged modified biochars to remove heavy metals have not been comprehensively evaluated. Therefore, three commonly used functional groups of modified biochars (5% and 10% H₂O₂-modified (BCH5 and BCH20); 25% and 65% HNO₃-modified (BCA25 and BCA65); and amino-modified (BCN), were prepared in this study to explore their stability and the Cd(II) removal performance of aged functional groups modified biochars was studied. The results showed that the O/C ratio is not sensitive enough to predict the stability of functional groups modified biochars, which was commonly used to evaluate pristine biochar (BC0); instead, -COOH content is crucial for modified biochar stability (r = −0.99, r = −0.91, p < 0.05). BCA65 displayed the highest less prone to oxidation property, which indicated that the high surface charges and uniform surface determined the less prone to oxidation ability of the functionally modified biochars. The order of the stability of functionally modified biochars was HNO₃-modified > H₂O₂-modified > amino-modified. After oxidation, the surface charges and pores were significantly reduced, and the Cd²⁺ adsorption mechanism of modified biochar changed from multilayer adsorption to monolayer adsorption, which led to a reduction in overall Cd(II) removal. The maximum adsorption capacities of BCA65 were reduced from 18.15 mg·g⁻¹ to 4.86 mg·g⁻¹ after oxidation, particularly. In the design and preparation of modified biochar, the long-term stability of the structure and function of modified biochar and its sustainable application in the environment should be considered while improving the heavy metal removal performance of biochars.

Polycyclic aromatic hydrocarbons (PAHs) show negative impacts on human health. Dietary intake is the predominant way for PAH exposure, of which barbecued food is a crucial contributor. This review aims to provide a comprehensive insight into the formation mechanism, influencing factors, mitigation strategies, and health risks of PAHs in barbecued food. PAHs in barbecued food are formed by Hydrogen abstraction and acetylene addition (HACA) mechanism, Diels-Alder reaction and Maillard reaction, which was influenced by heat source, temperature, cooking time, and the meat type. There are significant differences in PAH concentrations in different barbecued foods, where chrysene dominates among the selected PAH species. To reduce PAHs formation, adding marinades and adopting alternative cooking methods are suggested, which effectively reduce PAH levels by 53 -89 %. In addition, it is estimated that people in countries such as Pakistan has an incremental lifetime cancer risk (ILCR) over 10^-5 via barbecued food consumption, indicating potential health risk. This work highlighted that regular monitoring of PAH levels in barbecued food and dynamic modification of relevant safety limits are recommended to ensure food safety.

The presence of Fe(III) or oxygen can affect the biochar-mediated degradation of pollutants. However, the effects of changes in the form and species of Fe(III) on the degradation of pollutants have not been systematically investigated. Therefore, this study investigated biochar-mediated p-nitrophenol (PNP) degradation, which is influenced by species of Fe(III) at pH 2.5, 5.7, and 8.0. At pH 2.5, the anoxic degradation of PNP by biochar was 9.30 mg g⁻¹. Fe(III) could compete for electrons from biochar; therefore, PNP degradation was reduced 29%. Comparison with O₂, the higher redox potential of Fe(III) prevents the occurrence of a Fenton-like reaction. Consequently, the degradation of PNP decreased by 77%. At pH 5.7, the degradation of PNP (9.62 mg g⁻¹) by biochar was greatest, but after Fe(III) was introduced into the system, most of the Fe(III) precipitated, which significantly inhibited PNP degradation by 18% and 66% under anaerobic and aerobic conditions, respectively. Oxygen can take electrons from biochar to form ⋅O₂ ⁻ to reduce PNP; therefore, PNP degradation is the same under anaerobic and aerobic conditions. Interestingly, at pH 8.0, the addition of Fe(III) significantly increased the apparent degradation of PNP by 41% and 15% under anaerobic and aerobic conditions, respectively. Acidification experiment revealed that the increase in PNP degradation was due to the co-precipitates Fe(III) with PNP on the biochar surface. This study demonstrated that additional caution should be taken when estimating the biochar-mediated degradation performance of organic pollutants in practical environmental applications, especially when Fe(III) coexist in the system. Graphical Abstract