Rice bran-based bio-adsorbents: optimizing modification protocols and adsorption kinetics for cadmium decontamination.

This study evaluated Cd2+ adsorption by layer-specific rice bran and developed modification strategies. Unmodified bran (20 g/L) achieved >70% removal. Alkaline-oxidative combined modification was most effective, attaining 90% removal at only 5 g/L. The seed coat-endosperm layer showed superior capacity due to high phytic acid and fibrous microstructure. Mechanistic analyses (FTIR, SEM) indicated coordination complexation, ion exchange, and porous entrapment, with chemisorption rate-limiting. Kinetics followed quasi-second-order and Langmuir isotherm. Coexisting ions and initial concentration effects were examined. Conclusively, alkali-oxidatively modified seed coat-endosperm bran is a highly efficient, low-dosage biosorbent for Cd2+ remediation in wastewater.