Scientists at the University of California, Riverside, transformed discarded rice husks into biochar through pyrolysis, a high-temperature process conducted without oxygen.
The resulting porous carbon material was tested against methylene blue and methyl orange, two synthetic dyes widely used in textile manufacturing that persist in waterways.
In batch adsorption experiments, the biochar removed more than 99% of both dyes from aqueous solutions within 60 minutes under optimal pH conditions.
The husk-derived biochar outperformed several commercial activated carbons in uptake capacity per unit mass, according to the study published in ACS Sustainable Chemistry & Engineering.
Researchers attribute the performance to the material's high surface area, abundant oxygen-containing functional groups, and the natural silica structure inherited from the rice husk.
The team also demonstrated that the spent biochar could be regenerated through a simple ethanol wash and reused for at least five cycles with minimal loss of efficiency.
Rice husks constitute roughly 20% of the rice harvest by weight and are often burned in fields or dumped, releasing methane and particulate matter.
Converting this abundant byproduct into a water-treatment medium could simultaneously address agricultural waste disposal and industrial water pollution, the authors suggest.
Researchers recycle rice husks into a wonder material that removes toxic dyes from water
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