Vol 281 Iss. 2

This study evaluates the effectiveness of bioremediation of oil-contaminated terrestrial ecosystems using a composition of organomineral ameliorants. The aim of the study is to establish the influence of ameliorants on reducing the phytotoxicity of oil-contaminated organogenic soils and to track the dynamics of the decline in oil concentration in the soil under their influence. The study is directed at developing an ecologically safe and sustainable method for cleaning soils from oil contamination, which minimizes the negative impact on the environment and contributes to the restoration of soil fertility. As a result, the optimal ratio of components of the peat-diatomite ameliorant (PDA) for activating bioremediation processes in oil-contaminated soils was experimentally substantiated. The following component ratio of PDA was recognized as the most effective for the bioremediation of oil-contaminated soils: peat 51.5-53.5 %; sapropel 31.0-33.5 %; diatomite 15.0-15.5 % (by mass of air-dry matter). A direct dependence of the efficiency of oil destruction in oil-contaminated ecosystems on the application of PDA in the recommended composition was established. The results of the research confirm the effectiveness of the developed PDA.

The accumulation of petroleum sludge in port facilities constitutes a significant environmental liability due to its high viscosity and complex management. This study evaluates the technical feasibility of using this waste as the main binder in the formulation of a cold asphalt concrete, combining it with endogenous aggregates (serpentinites from nickel industry rejects and vitric tuffs) for road maintenance in Moa, Cuba. A physical-chemical characterization of the materials was carried out, and asphalt mixtures with sludge contents of 8.0; 8.5, and 9.0 % were designed. Twenty-four specimens were fabricated using Marshall compaction, and their properties (density, stability, and deformation) were evaluated according to Cuban standards. After applying statistical quality control (rejection of specimens with > 10 % deviation), the experimental results demonstrated that curing time is a determining factor. After 45 days of curing at room temperature, the optimal mixture (8.5 % sludge) developed a Marshall stability of 7.32±0.21 kN and a deformation of 3.38±0.15 mm, satisfactorily complying with the quality indices of Cuban standard NC 54-18:1985 for dense mixtures. Environmental leaching tests confirmed the encapsulation of contaminants. This approach offers a sustainable technical solution for road infrastructure and contributes to the circular economy through the valorisation of industrial waste.

This study focuses on developing a method for utilizing phosphogypsum, a large-tonnage waste product from phosphate raw material processing, whose disposal sites are sources of complex negative impacts on the environment. As a promising approach to the utilization of gypsum-containing waste, the study considers the interaction of phosphogypsum with a sodium carbonate solution (carbonate conversion), which yields calcium carbonate, a marketable product referred to as phosphochalk. Existing technologies typically produce a fine-grained material, which hinders filtration and restricts the potential applications of phosphochalk. This study aims to determine the carbonate conversion parameters that enable the production of phosphochalk with tailored particle size characteristics while maintaining a high degree of feedstock conversion. A series of single-factor experiments was carried out to evaluate the influence of reaction conditions – temperature, Na₂CO₃ concentration in the carbonate solution, liquid-to-solid (L:S) ratio, and phase contact time – on the conversion of CaSO₄·2H₂O. The results showed that raising the conversion temperature to 90-100 °C and increasing the L:S ratio to 10 promote intensive nucleation of CaCO₃ crystals and the formation of large agglomerates. A Na₂CO₃ concentration of 250 g/dm³ and a phase contact time of up to 3 h together yield phosphochalk with a particle size of D90 = 45 μm at a conversion degree of 98.8 %. In terms of its characteristics, the resulting product is suitable for use in the metallurgical industry as a raw material for flux production, which demonstrates its competitiveness in the secondary raw materials market. The recommendations developed in this work enable the design of a low-waste technology for processing technogenic raw materials, consistent with the principles of sustainable development and helping to reduce the environmental burden.