Tetracycline (TC), a common antibiotic, contaminates water sources, posing environmental and health risks. This study compared engineered biochar and hydrochar, both derived from rice husks, for their ability to remove TC from water.

Biochar was produced by heating the husks at high temperatures (250-350°C), while hydrochar was formed using hydrothermal carbonization (HTC) at lower temperatures (180-220°C). The most effective materials were then modified with acid for further improvement.

Key findings:

• Acid activation significantly boosted adsorption: Hydrochar’s capacity increased nearly fourfold, while biochar’s improved by 2.4 times.
• Optimal 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 differed: Hydrochar performed best at pH 5, while biochar preferred pH 3.
• Different adsorption models applied:Biochar fit the Freundlich model, while hydrochar followed the Langmuir model.
• Hydrochar had higher maximum capacity: It adsorbed more TC at higher concentrations compared to biochar.
• Mechanisms differed: Hydrochar relied on hydrogen bonding and hydrophobic interactions, while biochar involved cation exchange and mass diffusion.

Significance:

This research paves the way for developing cost-effective filters using these engineered materials to remove TC and other pollutants from wastewater, contributing to cleaner water and reduced environmental impact.