<p>The physicochemical properties of the commercial bentonite S-4205-02 (Bentovin) and its structural parameters were determined. Clay agglomerates were predominantly up to 10 – 20 microns in size. X-ray spectral analysis revealed a relatively high content of Fe₂O₃, Na₂O, CaO, which corresponds to the iron-aluminum variant of montmorillonite with a predominance of Na⁺ and Ca²⁺ ions in the interlayer space. The presence of potassium indicates the presence of illite. According to XRD data, the main component of the product is montmorillonite with impurities of quartz/cristobalite, kaolinite, illite, and hematite. Thermal analysis curves and IR spectrum of bentonite were analyzed. The textural characteristics of the powder were determined. The specific surface area was 58 ± 6 m²/g. Based on bentonite and orthophosphoric acid, a geopolymer bentonite-phosphate binder was synthesized for the first time. XRD and IR spectral analysis show that the interaction of aluminosilicate powder with orthophosphoric acid leads to the complete destruction of the montmorillonite structure with the formation of aluminum and silicon phosphates.</p>