Interaction of Cocos nucifera cream casein with humic acid suspensions

Two caseins labelled as CaSMG (casein without fats) and CaMG (casein with fats) were extracted from coconut cream. Both caseins were used as coagulants for the aggregation of humic acid (HA) particles in synthetic water at pH = 6 during the jar-test essays. The optimum dosage of CaMG or CaSMG and the residual turbidities of treated water obtained depend on the type of used casein (CaMG or CaSMG) and the concentration of particles in solution. The optimal doses of CaMG and CaSMG are respectively 280 and 180 mg/L for solution S₁ (HA aqueous solution at 15 mg/L), and then 340 and 240 mg/L for solution S₂ (HA aqueous solution at 25 mg/L). The residual turbidities of treated water are respectively 6.88 and 3.85 NTU for solution S₁ and 4.52 and 2.53 NTU for solution S₂. The collected sediment volumes are respectively 1.2 and 1.5 mL for solutions S₁ and S₂. The electrophoretic mobility measurement and transmission electron microscopy images of flocs formed during the flocculation essays suggest that both caseins operate through both mechanisms (charge neutralisation and bridging process mechanism), this last one seems to be predominant. The aggregates formed are the large clusters and result from adsorption of HA particles by the casein molecules.