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Abstract: Study on the coagulation of four species of red tide organisms (Nitzschia pungens, Skeletonema costatum, Prorocentrum minimum and Noctiluca scintillans) with montmorillonite, and the effect of montmorillonite pretreatment on the coagulation shows that the capability for montmorillonite to coagulate with them is in the order:N. pungens > S. costatum > P. minimum > N. scintillans. The coagulation is discussed from the aspects of the structure, shape, size, movement, habit, etc. of different species and the results are explained theoretically. The experimental results also indicate that the treatment of montmorillonite with acid can enhance its coagulating capability. This is due to the fact that Al(OH2) 6+3 , exchanged from the clay lattice by hydrogen ion H+, forms hydroxy-aluminum polymers on the surface of the montmorillonite. The hydroxy-aluminum polymers positively charge and increase the positive characteristic of the clay surface, and also serves as a bridge between adjacent surfaces of particles. These two functions enhance the montmorillonite's capability for coagulating with the organism cells.

Abstract: This article reports studies on the coagulation of kaolin(from Wuxian, Jiangsu, China) on various red tide organisms, and the observation for the first time that the coagulation of kaolin is much greater than that of montmorillonite so that kaolin is a more effective, clay for removing red tide organisms. The authors’ theoretical explanation and analysis by a mathematical-physical model prove that compared to montmorillonite, kaolin has greater attraction for organism cells and therefore greater coagulation capability. This project’s studies on the effects of pH and acid-treatment show that the acid-treatment does not have much influence of the kaolin system; whereas the effect of pH on the kaolin system is the same as that on the montmorillonite system.

Abstract: Coagulation of red tide organism cells with clays is discussed in theory and the effects of some factors on it are studied. A quantitative model is presented which describes how the coagulation varies with pH in solution. According to the model, within the pH-range between $$pH_{zpc_a } $$ and $$pH_{zpc_b } $$ ,V R is negative and the coagulation is strong and strongest at $$pH = \left( {pH_{zpc_a } + pH_{zpc_b } } \right)/2$$ . It is also demonstrated that when the diameter of clay particles is close to that of cells, the collision probability is low, resulting in weaker coagulation. The model results have been corroborated by experiments and so are scientific and theoretical bases for application.