Mercury pollution remains a critical environmental concern, demanding effective removal methods. This study introduces a novel approach using ferrous sulfide-doped biochar (FBC) for adsorbing 2-valent mercury (Hg(II)). The synthesized FBC, featuring a core-shell structure of pyrrhotite/magnetite, demonstrated impressive adsorption capabilities at low Hg(II) concentrations, with FBC-5 reducing levels to less than 0.05 mg/L within 30 minutes. The study explored the impact of varying ferric sulfate and alga powder ratios on FBC composition, revealing increased oxygen-containing groups with higher ferric sulfate content.

Langmuir and Freundlich adsorption models were applied, highlighting FBC-4 as the most effective, reaching a maximum capacity of 95.51 mg/g. The FBCs exhibited stability within a pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More range of 3.8-7.2 and demonstrated the ability to adsorb multiple heavy metals. A novel model was introduced to analyze the adsorption preference for different Hg(II) species, identifying calomel in mercury-saturated FBC. Notably, the core-shell structure contributed to minimal iron release.

Considering the environmental implications, mercury’s toxicity necessitates urgent solutions. The study provides a cost-effective sorbent synthesis method with the potential to remove mercury effectively from water without introducing other metals. The research contributes a valuable model for analyzing the adsorption behavior of different mercury species.

Mercury pollution, originating from coal combustion and industrial wastewater, poses a persistent threat. Current methods, including adsorption, stand out for their convenience and efficacy. Biochar, derived from algae, proves advantageous due to its functional groups and high cation exchange capacity. Sulfide doping, particularly with FeS, enhances biochar’s mercury adsorption capabilities. The study’s one-process method for synthesizing FBCs addresses concerns of excess iron release, providing a stable and efficient sorbent for mercury removal. The research emphasizes the importance of developing intuitive models for understanding adsorption details and metal ion behaviors, contributing to advancements in environmental remediation.