The economical removal of organics from sodium aluminate solutions has been required for decades. Based on security filtration using tricalcium aluminate hexahydrate (TCA) as a filter aid, a novel short process to eliminate impurity particles and remove organics simultaneously was presented. Ultrafine TCA samples with poor crystallization, high TCA content, high surface free energy, and large lattice distortion were prepared in the concentrated sodium aluminate solution. The zeta potential of the TCA binary mixture in alkaline solutions was linearly depended on the TCA content, suggesting the additivity of the zeta potential in the binary mixture. The variation in the electrical double layer of the TCA binary mixture was demonstrated in the alkaline solution. Furthermore, the ultrafine TCA exhibited a high adsorption capacity for organics with long alkyl chains and high relative-molecular-mass. The adsorption capacity of 69.69 mg/g organic carbon for sodium humate was achieved, whereas the digestion at a high temperature remarkably reduced the adsorption capacity of TCA.