A study published in the Journal of Analytical and Applied PyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More by Ruiying Wang, Fen Li, Hong Yan, Oxana P. Taran, Ying Yang, and Dongdong Yang explores a promising solution for tackling noxious sulfur-containing gases like methyl mercaptan (CH3​SH) and hydrogen sulfide (H2​S). These gases, often byproducts of sewage treatment and biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More decomposition, pose significant environmental and health risks, even at trace concentrations. The research focuses on developing high-performance, cost-effective adsorbents from agricultural waste—specifically, rice husks and walnut shells—by converting them into low-graphitized, porous biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More. The team introduced a silicon-template modification method, demonstrating that strategically engineered biochar can achieve superior, targeted removal of these stubborn air pollutants.

The foundational idea of this work lies in overcoming the limitations of conventional biochar, which often suffers from disordered pore structures that don’t efficiently match the size of odor molecules. By employing a silicon-template method, the researchers incorporated sodium silicate (Na2​SiO3​) with the biomass precursors (peanut shells, rice husks, and walnut shells) before pyrolysis. During the high-temperature process, theNa2​SiO3​ converted in situ to silicon dioxide (SiO2​). A subsequent chemical wash using a sodium hydroxide ( NaOH) solution dissolved and removed the SiO2​ scaffold. This templating strategy was crucial: it facilitated the formation of well-developed mesoporous and macroporous architectures in the carbon matrix and enhanced local graphitization, resulting in a hybrid, low-graphitized structure ideal for gas adsorption.

Before modification, rice husk biochar (DKB series) exhibited the best intrinsic capability for CH3​SH adsorption, while walnut shell biochar (HTB series) performed best for H2​S. The optimized, directly pyrolyzed materials were DKB-700-5 for CH3​SH and HTB-800-10 for H2​S. Applying the SiO2​ templating and removal to these best performers yielded DK-700-5 (rice husk-derived) and HT-800-10 (walnut shell-derived).

The enhancement was dramatic. The modified DK-700-5 achieved a CH3​SH sulfur capacity of 15.8 mg/g, representing an 8.3-fold improvement over its unmodified counterpart. The modified HT-800-10 showed a significant H2​S sulfur capacity of 13.5 mg/g in mixed gases, which is a 2.45-fold enhancement in H2​S adsorption compared to its unmodified version. The resulting materials were characterized as low-graphitization carbons, possessing abundant structural defects and disordered carbon domains that provide high-energy, active sites for molecular interaction.

The study identified distinct, tailored adsorption mechanisms for the two optimized materials. The DK-700-5 biochar, optimal for CH3​SH capture, relied on a combination of physical confinement within its dominant mesoporous structure and chemical interactions. Critical to this was the presence of carboxyl groups (O−C=O) and oxygen vacancies. The CH3​SH was initially adsorbed, followed by gradual oxidation facilitated by superoxide radicals (⋅O2−​) generated at the oxygen vacancies. This led to the ultimate conversion of the pollutant into less harmful sulfate ions (SO42−​), with intermediates like R-SO-R and elemental sulfur (S0) also detected.

The HT-800-10 material, superior for H2​S adsorption, employed its hierarchical porous structure and a high specific surface area of 513.27 m2/g. H2​S adsorption involved physical capture and oxidative transformation. Surface superoxide radicals (⋅O2−​) and oxygen-containing functional groups played a pivotal role in converting H2​S into elemental sulfur (S0) and sulfate (SO42−​), enabling efficient capture and catalytic conversion.

In conclusion, this research confirms that optimizing pyrolysis conditionsThe conditions under which pyrolysis takes place, such as temperature, heating rate, and residence time, can significantly affect the properties of the biochar produced.   More to achieve low graphitization, combined with silicon-templating to engineer porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More, is a powerful and practical strategy. It effectively tailors biomass-derived carbon materials for high-efficiency, targeted environmental odor control.

Source: Wang, R., Li, F., Yan, H., Taran, O. P., Yang, Y., & Yang, D. (2026). Study on the performance and structure of low graphitized biochar prepared by silica template method for adsorbing odorous gases. Journal of Analytical and Applied Pyrolysis, 193, 107411.