Vladimir Pavićević

Apricot kernel shells were evaluated as a sustainable activated carbon precursor for wastewater treatment using experimental and theoretical methods. Two adsorbents were synthesized: physically activated with CO₂ (AKS-CO₂) and chemically activated with H₃PO₄ (AKS-H₃PO₄). Comprehensive materials characterization and adsorption tests using Pb²⁺ ions and Rhodamine B dye (RhB) as model pollutants revealed that AKS-H₃PO₄ significantly outperformed its physically activated counterpart. With an exceptionally high specific surface area (1159.4 m²/g) enriched with phosphorus-containing functional groups, the chemically activated carbon demonstrated outstanding removal efficiencies of 85.1% for Pb²⁺ and 80.3% for RhB. Kinetic studies showed Pb²⁺ adsorption followed pseudo-second-order kinetics, indicating chemisorption, while RhB adsorption fitted pseudo-first-order kinetics, suggesting intra-particle diffusion control. The thermodynamic analysis confirmed the spontaneity of both processes: Pb²⁺ adsorption was exothermic under standard conditions with positive isosteric heat at higher concentrations, reinforcing its chemisorption nature, whereas RhB adsorption was endothermic, consistent with physisorption. Density Functional Theory (DFT) calculations further elucidated the mechanisms, revealing that Pb²⁺ preferentially binds to oxygen-containing functional groups, while RhB interacts through hydrogen bonding and π–π stacking. These findings establish chemically activated apricot kernel shell carbon as a high-performance adsorbent, exhibiting exceptional removal capacity for both ionic and molecular contaminants through distinct adsorption mechanisms.

The modification of agricultural wastes for improved phosphate removal from wastewater is an innovative approach aimed to address the growing environmental challenges posed by nutrient pollution. As agricultural runoff contributes significantly to the eutrophication of water bodies, the effective removal of phosphorus from wastewater has become a critical necessity for environmental sustainability. This field of study not only explores the repurposing of agricultural residues but also emphasizes their potential as low-cost bio-based sorbents for phosphate remediation, thereby offering a dual benefit of waste reduction and environmental protection. Research has shown that various types of agricultural wastes, when modified through physical and chemical processes, can enhance their ability to capture and retain phosphorus from wastewater. Techniques such as metal loading and biochar production have proven effective, leading to notable advancements in the efficacy of these materials as phosphate adsorbents. Studies have indicated that chemically and thermically modified agricultural wastes can achieve phosphorus removal efficiencies comparable to traditional methods, making them a promising alternative in wastewater treatment applications. Despite the potential benefits, the implementation of modified agricultural wastes also faces several challenges. Issues such as: the economic feasibility of large-scale application, the complexity of modification processes, and concerns about the long-term sustainability of these technologies present significant hurdles. Overall, the modification of agricultural wastes represents a vital intersection of waste management and environmental conservation, promoting a circular bioeconomy while providing practical solutions to the pressing problem of nutrient pollution in aquatic systems.

Pollution of water bodies is a significant issue in modern society, with increased concentrations of organic pollutants rendering standard water treatment techniques insufficient to meet legal water quality standards. To reduce ecological pressure and mitigate the toxicity of these pollutants, it is necessary to oxidize and transform them into non-hazardous forms. Advanced oxidation processes, particularly photocatalysis, have gained prominence for this purpose. Photocatalysis enables the complete conversion of organic matter into carbon dioxide and water. Optimizing process parameters can further enhance the efficiency of photocatalysis in industrial wastewater treatment plants.

Essential oils are aromatic, volatile, complex mixtures of various compounds, mainly hydrocarbons (monoterpene and sesquiterpene) and some oxygenated hydrocarbons. Juniper berry essential oil has wide application and high commercial value due to its considerable antimicrobial activities. It is used in medicine, food, cosmetic and pharmaceutical industry and veterinary medicine. Generally, it is obtained by hydrodistillation, technique for the extraction of substances which do not mix or mix very poorly with water and are unstable at their boiling temperatures. It provides high quality of essential oil and also represents a relatively simple, safe and environmentally friendly process. The variations in the chemical composition of the essential oil obtained from juniper berries at various distillation rates (3, 6 and 8 ml/min) and various mass ratio juniper berries−water (hydromodules - 1:3, 1:4 and 1:5) are presented in this paper. It is important to emphasize that the variations made influence only in quantitative (mass %), but not in qualitative chemical composition (no differences, same 58 components were detected in all experiments). To reflect those effects, only 23 identified components with the content higher than 0.5 mass % were selected, constituted 95−96 mass % of the essential oils. The major constituents of the essential oils were monoterpenes (67.39−71.00 mass %), followed by sesquiterpenes (21.64−24.54 mass %), while the oxygenated monoterpene (1.54−2.42 mas. %) and oxygenated sesquiterpenes (0.89−1.46 mass %) were much less present. According to volatility, the high volatile (boiling point 153−167ºC) components are the main constituents of the essential oils (61.69−63.81 mass %), followed by the low volatile (boiling point 252−288oC) components (22.57−26.04 mass %), and the least present medium volatile (boiling point 173−212ºC) components (7.24−9.61 mass %). The variations in the mass content of the essential oil at various distillation rates showed clear general trends for all hydromodules (with exceptions at some components). With the increasing of distillation rate, mass % of high and medium volatile components decreased, while mass % of low volatile components increased. This is caused by higher extraction of low volatile components at high distillation rate, which resulted the increasing of their mass %. The variations in the mass composition of the essential oil at various hydromodules showed less expressive trends for all distillation rates. That means it has much less influence on the mass composition than the variation of distillation rate. Therefore, experiments at various distillation rates should be continued in combination with the fractionation of the essential oil by simultaneous hydrodistillation and rectification, including the effects of preparation procedures of juniper berries and defining of optimal energy consumption, i.e. optimal time period of hydrodistillation.