Eutrophication was recognized as a pollution problem in European lakes and reservoirs in the mid-20th century. Since then, it has become more widespread. Surveys showed that 53% of lakes in Europe are eutrophic. Phosphorus from excess fertilizers and detergents ends up washing into lakes, creeks, and rivers. This overabundance of phosphorus causes excessive aquatic plant and algae growth, so negative environmental effects include hypoxia, the depletion of oxygen in the water, which induces reductions in specific fish and other animal populations. In this study, aluminum-impregnated mesoporous adsorbent on the base of autochthonous diatomite was tested for its ability to remove phosphate from water The modified diatomite was prepared by thermochemical modification as follows: the initial sample of diatomite was calcined at 450oC then it was kept at 600C in aluminum salt solution at continuous stirring and, after that in the solution of ammonia in ambient temperature. The final suspension was filtered, washed from the associated ions, centrifuged and dried at room temperature and then at 1100C. The obtained samples were stored in a dessicator before the use. The surface structure of the materials was investigated by means of X-ray diffraction (XRD), a N2 adsorption–desorption technique and Fourier transform-infrared (FT-IR) to understand the effect of surface properties on the adsorption behavior of phosphate. The modified diatomite was tested to remove phosphate ions from aqueous solution in batch conditions at initial phosphate concentration 2-5 mg/L – the average phosphate content in water after biological treatment. In the adsorption test, the adsorption isotherms, kinetics, pH, the sorbent doze effect on adsorption capacity have been studied. The conditions of maximal phosphate removal to remain phosphate concentration of 0.6 mg/l (the maximum allowable concentration) have been determined: the solution pH = 5.0; the adsorbent doze =2.0g/l, temperature 200C. The results showed that the modified diatomite had fast kinetics and high adsorption capacity – 0.4mgP/g. The obtained results have been modeled by using appropriate theoretical models - Lengmuire, Freundlich and Redlich-Peterson. The models constants and correlation coefficients were calculated and compared. Both the two-parameter Langmuir and the three-parameter Redlich–Peterson isotherms had higher coefficients of determination for the adsorption of phosphorus onto modified diatomite. It was concluded that the adsorption data of phosphate onto modified diatomite fitted to the Langmuir model (R2 =0.9296) more than Redlich–Peterson model (R2 =0.8273). The relatively low cost and high capabilities of the modified diatomite make it potentially attractive adsorbent for the removal of phosphate from aqueous solution.