Comparing the methods of grain size analysis of gypsum-containing sulfuric acid wastes neutralized with limestone

Introduction. The purpose of the work is to compare different methods of determining the granulometric distribution of gypsum-containing waste generated during the neutralization of sulfuric acid with limestone. The object of the study is gypsum-containing product obtained in the process of utilization of sulfuric acid by limestone at the enterprises of mining, metallurgical, chemical and other industries. Materials and methods. Granulometric distribution was determined using sedimentation methods and laser diffraction method. In addition, microscopic description and characterization of the studied samples were performed. Results. In the course of the study the peculiarities of granulometric analysis of gypsum-containing wastes belonging to the category of saline soils were revealed. Discussion. In the article, special attention is paid to the performance of particle size analysis by laser diffraction. It is important to note that the results obtained by this method are presented in volume percentages and not in weight percentages. This makes it incorrect to directly compare the data obtained using classical methods with the results of laser analysis. Conclusion. It is established that the use of sedimentation methods is difficult due to pronounced coagulation of suspension, which affects the accuracy of the final results. It is shown that special attention should be paid to the stage of sample preparation before testing, including drying of gypsum-containing waste samples at temperatures not exceeding 60°C to avoid loss of crystallization water. Resume. The obtained results can be applied for engineering-geological assessment not only of gypsum-containing wastes of sulfuric acid neutralization, but also of other similar anthropogenic formations. These data are necessary to analyze the stability of waste storage facilities, to develop integrated approaches to their use and to reduce their negative impact on the environment.