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 recultivation of landfills is one of the main tasks in ensuring the environmental safety of urbanized areas. The waste of old landfills contains mainly soil-like material. The contamination of soil-like materials is uneven, but the level of contamination in some parts can be within acceptable limits. If there is no contamination or if the contamination levels are considered acceptable, the material can be utilized as soil for recultivation. This study aims to evaluate the fertility of soil-like material from landfills. The parameters used to characterize fertility were the content of humus and mobile forms of nitrogen, phosphorus, and sulfur, as well as potassium, calcium, magnesium, and pH value. The samples of soil-like material were collected in November 2021 at a landfill located in the Voroshilovsky district of Volgograd at a depth of greater than 2.5 m, where there was no or low contamination. The soil-like materials are rich in humus and nutrients. However, they contain an average amount of magnesium. This indicates the fertile potential of the material and the possibility of its use as fertile soil during recultivation. The slightly alkaline environment, high potassium content, and mobile sulfur in soil-like materials necessitate the development of measures to normalize these indicators and select plants for phytoremediation.

Keywords: landfill, soil-like material, fertility, environmental safety, humus, nitrogen, phosphorus, potassium

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.