This paper investigates interaction processes of the Fe³⁺, Cu²⁺, Ni²⁺, and Co²⁺ cations with humic acids isolated from brown coals of Ekibastuz basin. It was demonstrated that the sorption of heavy metal ions by humic acids (HA) depends on the concentration and nature of cations and decreases in the order of Fe³⁺ > Cu²⁺ > Ni²⁺ > Co²⁺; while increase in the concentration of humic acids (HA) results in the higher yield of ions and metals. The occurrence of ion exchange and complexation reactions in metal-humic acid systems is confirmed by the appearance of new bands and the shift of the absorption bands corresponding to stretching and deformation vibrations of carboxylate ions, C = O and OH groups. The occurrence of these processes is also evidenced by spectrophotometric data, as well as a decrease in the pH of the solution due to deprotonation of humic acids during these reactions. Thus, based on the data on the degree of sorption of metal cations by humic acids, the results of infra-red spectroscopy and spectrophotometry, it can be concluded that the Fe³⁺, Ni²⁺, Co²⁺, Cu²⁺ cations interact with HA by the ionic mechanism and by the complexation mechanism with electron-donating functional groups. Electrochemical studies of the Cu²⁺ – humic acid system carried out by the method of cyclic voltammetry also indicate the occurrence of the interaction of humic acid with copper cations. Modification of humic acid with copper ions shows the electrochemical activity of copper immobilized on the surface of dispersed humic acid, which is important for the implementation of electrocatalytic reactions on modified glassy carbon-humic electrodes.

For large-scale hydrogen use for alternative fuel problems, hydrogen transportation must be solved. Hydrogen can be transported as compressed gas, liquid, or bound in carriers. The chapter describes current transportation technologiesgaseous hydrogen via pipelines or special trucks, and liquid hydrogen in cryogenic tanks. The potential of using existing natural gas pipelines is analyzed; the need for modern pipeline material complex research is emphasized. Transportation in solid or liquid carriers, disadvantages and advantages of transportation methods, and problems and ways to solve them are analyzed. Hydrogen facilitates the conversion of low-grade crude oils into high-energy transport fuels by catalytic cracking and desulfurization. Ammonia production, essential for fertilizers and explosives, relies heavily on hydrogen synthesis from nitrogen and hydrogen. Methanol and dimethyl ether fuels offer alternatives to hydrogen storage and transportation, while liquid hydrocarbon fuels from coal and biomass utilize hydrogen in conversion processes like Fischer-Tropsch. Proton exchange membrane and alkaline fuel cells depend on hydrogen for electricity generation in transportation. Additionally, hydrogen serves as a reductant in metallurgy, with advancements in direct iron reduction and green steel initiatives driving sustainable practices in the steel industry. These applications underscore in modern processes and its potential for addressing energy and environmental challenges.

Humic substances (HSs) are a diverse class of natural compounds with no fixed chemical composition, formed from plant and microbial residues through the action of environmental factors and living organisms over many years. Despite extensive research spanning two centuries, the complex and variable nature of HSs' structure remains a subject of scientific inquiry. These substances, notably humic acids, fulvic acids, and humin, play crucial roles in ecological and environmental processes due to their abundant functional groups and resilience to biodegradation. This review explores the intricate structure and properties of HSs, their classification, and their occurrence in nature. It highlights the different models proposed to describe the structural fragments of humic acids, emphasizing their aromatic cores and diverse functional groups. The variability in the molecular weight distribution of HSs, attributed to their polydisperse nature, is also discussed, along with methods used for their determination, such as exclusion chromatography. Furthermore, the elemental and functional compositions of humic acids are examined, detailing their acid-base properties and capacity for heavy metal complexation. The synthesis of HSs from natural sources, such as soil, peat, coal, and artificial processes, is covered, showcasing methods like alkaline extraction and hydrothermal treatment. Recent advancements in artificial humification, including oxidative ammonolysis and Fenton reagent-based oxidation, are reviewed for their potential in producing environmentally friendly humic materials from lignin and waste biomass. The study concludes by underscoring the environmental significance and practical applications of HSs, particularly in agriculture, soil conditioning, and environmental remediation. The diverse properties and synthesis methods of HSs make them promising candidates for sustainable material production and environmental management. Humic acids are versatile compounds beneficial for human health due to their potent antioxidant properties, immune-modulating effects, and support for gastrointestinal health and detoxification. Structurally diverse, they feature groups like carboxyl, phenolic hydroxyl, quinones, ketonic carbonyls, amino, and sulfhydryl, contributing to their stability and amphiphilic nature. In pharmaceutical applications, they show promise for drug delivery, antioxidant therapies, wound healing, antimicrobial actions, and biofilm disruption, underlining their biocompatibility and safety. Key words:

Aqueous zinc-ion batteries (AZIBs) are considered as one of the most attractive candidates for safe, low-cost, and environmentally benign energy storage systems. However, the widespread implementation of these systems is still limited due to major problems with the zinc metal anode, including uncontrolled dendrite formation, hydrogen evolution, and the low reversibility of zinc plating and stripping. These issues lead to rapid capacity fading and shortened cycle life, highlighting the urgent need for electrolyte optimization as a simple and effective strategy to overcome anode instability. The purpose of this work was systematically investigated the electrochemical behavior of zinc anodes in a series of electrolytes with different ZnSO ₄ -Li ₂ SO ₄ compositions, namely 2M ZnSO ₄ , 1.5M ZnSO ₄ + 0.5M Li2SO ₄ , 0.5M ZnSO ₄ + 1.5M Li ₂ SO ₄ , 1M ZnSO ₄ + 1M Li ₂ SO ₄ , and 2M Li ₂ SO ₄ . The electrochemical performance was evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge tests, and then post-cycle morphological characterization was performed using scanning electron microscopy (SEM). The results show that adding Li ₂ SO ₄ to the ZnSO ₄ electrolyte significantly changes the structure of the Zn ₂ + solution, thereby increasing the reversibility of zinc plating/stripping and suppressing dendrite formation. In particular, mixed electrolytes exhibit sharper voltage profiles and reduced polarization compared to single-salt systems. Among the tested formulations, the equimolar mixture of 1M ZnSO ₄ + 1M Li ₂ SO ₄ achieved the most balanced performance, delivering stable cycling and a uniform zinc dendrite morphology. This study highlights electrolyte engineering as a practical and scalable approach to stabilize zinc anodes, providing new insights into the design of high-performance aqueous zinc batteries for future large-scale energy storage applications.