Cadmium removal from rice protein via synergistic treatment of rhamnolipids and F127/PAA hydrogels

Heavy metal ions can accumulate in the area’s crop harvest, such as rice, via a tight binding with protein. Such binding paves great difficulties to remove heavy metal ions. This study aims to remove cadmium from contaminated rice protein using rhamnolipid biosurfactant together with Pluronic F127/poly (acrylic acid) (i.e., F127/PAA) hydrogels. The two-step consequential washing removed 92% of cadmium in rice protein, making the residual cadmium content below the safety level (<0.2 mg/kg) without impairing the main components and structure of rice protein. Interestingly, the washing by either rhamnolipids or hydrogels failed to effectively remove cadmium, indicating the synergistic effect of the two materials. Mechanistically, rhamnolipids with higher Cd 2+ binding constant compete with protein on binding with cadmium and then deliver it to F127/PAA hydrogels that present highest Cd 2+ adsorptive capability for immobilization. In considering that the F127/PAA hydrogels are reusable, this treatment is low-cost, safe and effective for removal of cadmium from polluted rice products.