The paper presents the concept of sorption and surface phenomena, as well as ion exchange. These processes are accompanied by absorption or exchange of ions due to the free energy of the surface layer of the solid phase. It is proposed to consider the process of ion exchange between the solid and liquid phase during filtration. As a solid phase, synthesized loading is used, which is used in various industries. It is noted that the synthesized load has high mechanical strength and chemical resistance. It is indicated that the size and shape of the loading grain affects the ion exchange rate and hydraulic resistance. The dependence taking into account the free energy of the loading surface and the mechanism of ion exchange in the equivalent dependence is given. Technological characteristics of some types of loading are shown. The duration of filtration is determined by the appearance of dissociated ions in the filtrate and depends on the exchange capacity of the load. Static and dynamic exchange capacities are allocated. The relevance, purpose and objectives of the work are formulated. A scheme of fluid motion through the elementary loading layer is proposed for the mathematical description of the process. The increment of substances in the elementary loading layer is described and the conditions of fluid flow around the loading grain of spherical shape are formulated. The reduction of ion concentrations in the elementary layer is mathematically shown. The concentration gradient is obtained as a partial derivative with two variables. The condition of fluid flow around the loading is introduced, based on the processes of hydrodynamics. The flow pattern of the loading elements depends on the Reynolds number. With the help of mathematical and physical analysis, a theoretical dependence was obtained, which relates the initial concentration of the studied substances in water, the metabolic capacity of the load, the hydrodynamic and physical parameters of the flow. The performed theoretical studies allowed to substantiate the conclusions of this work and to formulate a conclusion about the influence of flow hydrodynamics on the change of absorption of substances from water by loading.