Triboelectrification of proteo-lignocellulose constituent particles for predicting their positions in triboelectric...

Tribo-electrostatic separation (TES) of proteo-lignocellulosic biomass residues such as oilseed meals holds promise for sustainable classification of their ingredients with retained functionalities. However, there is a significant gap in our understanding of how the tribo-charging behavior of oilseed meal constituent particles (i.e., protein, cellulose, lignin, and hemicellulose) correlate with their enrichment during TES. This research utilized an online tribo-charge measurement system to investigate the charging behavior of soybean protein isolate, microcrystalline cellulose (MCC), alkaline lignin, de-alkaline lignin, and xylan using four different tribo-charger materials of polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), nylon, and copper alloy C12200 at different lengths under laminar airflow, considering different particle dosing rates (g/h). Accordingly, all protein and fiber powders acquired positive charge densities (nC/m²) with PTFE tubes and negative charges with nylon tubes, irrespective of length or particle dosing rates. In contrast, all powders in contact with PVC and copper alloy tribo-chargers exhibited distinct charging behaviors, where soybean protein had a high positive charge, MCC was negatively charged, and lignin particles remained almost neutral. The charge-to-mass ratios (nC/g) of protein and dietary fiber particles were highest at lower particle dosing rates with long tribo-charger tubes, indicating that particle-wall collisions contribute more to charge acquisition in diluted flows, while particle-particle collisions are more significant in concentrated flows. The deduced triboelectric series was: (+) Nylon> Soybean protein> Xylan> Alkaline lignin> De-alkaline lignin> Copper alloy> PVC > MCC > PTFE (-). These findings will be utilized to assess oilseed meal TES, providing insights into the key factors that correlate the particles' tribo-charging behavior with their separation behavior.