The paper presents an analysis of the methods for the chemical modification of biochar. The characteristics of acid and basic modifications, modifications with hydrogen peroxide, sulfonation, amination, impregnation with metal oxides, and magnetization are examined. It is demonstrated that the method of modification, the parameters of the technological process, and the nature of the modifying agent all exert an influence on the chemical composition, structure, porosity, pore size, and total specific surface area of the modified coal. The combination of methods, technological parameters, and modifiers allows for the production of sorbents for wastewater treatment based on biochar with specific properties for the sorption of certain groups of different pollutants.

Keywords: biochar, chemical modification, sorption properties, porosity, pore size

The paper presents a new approach to assessing the level of contamination with heavy metals of the soil-like fraction from landfills using Monte Carlo simulation using the example of landfills located within the borders of Volgograd.It was found that with a probability of 36.2%, the contamination level of a soil-like fraction from the landfill located in the Voroshilovsky district will correspond to moderately hazardous, and with a probability of 63.8%, hazardous. It is economically justified to isolate a soil-like fraction with a low level of pollution to detoxify it and further use it in the territory reclamation. For a soil-like fraction from landfill located in the Traktorozavodsky district, the pollution level was determined as extremely hazardous and hazardous with a probability of 87.1% and 3.1%, respectively. It is shown that a useful and usable part cannot be isolated from a soil-like fraction. A soil-like fraction must be neutralized and placed at waste disposal facilities.The presented approach is a useful instrument for pollution level assessment of a soil-like fraction, which can increase the accuracy of an estimate and the management effectiveness of a soil-like fraction during landfill development.

Keywords: landfill, soil-like fraction, heavy metals, pollution level, Monte Carlo method, modeling

The researches results of the fuel ash waste’s and grain crops straw’s influence on the properties of the producing expanded clay gravel are presented in the paper. These wastes were used as auxiliary additives in the raw combination. The optimal composition of the raw combination has been established in the laboratory, for which physical and mechanical characteristics of the samples, including water absorption, compressive strength, bulk density, were analyzed. Characteristics of the expanded clay gravel samples are compared with the state standards requirements. It was found, that the addition 5% fuel ash and 1.5% crop waste (grain straw) ensures optimal swelling of the combination and high strength characteristics of the finished product.

Keywords: expanded clay, fuel ash, waste of crop production, swelling, construction materials, porosity.