Triboelectric separation of aleurone cell-cluster from wheat bran fragments in nonuniform electric field

•Nonuniform electric field was used to refine aleurone particle after tribocharging.•Efficiencies of positive and negative nonuniform electric fields were compared.•Deflected behaviors of bran tissues in the nonuniform electric fields were studied.•We proved that particle size was not the main reason for charging diversity.

Nonuniform electric field (NUEF) was designed to separate aleurone cell-cluster from wheat bran fragments after tribocharging in a polytetrafluoroethylene tube. After triboelectric separation (TS), the ultrastructure, composition and particle size distribution of the bran fragments were studied. The results showed that, the positive-NUEF had a higher efficiency than the negative-NUEF for the enrichment of aleurone cell-cluster. After the first step of TS in positive-NUEF, about 1.5-time more aleurone cell clusters and 1.3-time more testa particles were deflected to the positive electrodes, while the outer pericarp fragments were enriched in the middle fraction. No obvious difference was found between the particle sizes of the electrode-fraction and middle-fraction, suggesting that the difference in particle size was not the main reason for the charging diversity. After two steps of TS in positive-NUEF, the proportion of aleurone cells increased from 51% to 78% with a total yield of 42%, indicating that the nonuniform electric field was effective for the enrichment of aleurone particles.