<p>Studies were carried out to obtain and evaluate the efficiency of polyaluminumchloride synthesized from aluminum-containing wastes of the oil and gas industry for coagulation of natural and wastewater. Spent aluminumbased adsorbents were used as raw materials; they were chemically treated with sodium hydroxide and hydrochloric acid solutions under controlled temperature conditions. As a result of the synthesis, an active aluminooxychloride phase was formed, which was confirmed by thermogravimetric, differential thermal, and microstructural analyses. It was established that the obtained coagulant has a homogeneous microstructure and a stable phase composition, ensuring high efficiency in coagulation processes. The optimal dose of polyaluminumchloride is approximately 1.25 g/dm³; however, it varies depending on the composition of the source water, particularly the concentration of suspended solids and the pH value. Under optimal treatment conditions, up to 95% of suspended particles can be removed. The developed technology is characterized by technological stability and economic feasibility, and it also contributes to the utilization of aluminum-containing wastes from oil and gas production. The findings confirm the potential of domestically produced polyaluminumchloride for the purification of natural and wastewater and for addressing important environmental challenges. The technology demonstrates operational stability, environmental viability, and importsubstitution potential for water treatment enterprises. </p>