The increasing pollution from the textile industry, particularly organic azo dyes, presents a significant environmental challenge, necessitating the development of effective and sustainable treatment methods. This study investigates the adsorption potential of hazelnut shells (raw—RHSs; modified—MHSs) for the removal of organic azo dyes from aqueous solutions. As biomass, hazelnut shells are biodegradable and represent a sustainable alternative to synthetic adsorbents, thereby reducing the ecological footprint. Through a series of batch adsorption experiments, the influence of various parameters, including pH, contact time, concentration, and temperature, on adsorption capacity was examined. Characterization of the hazelnut shells was conducted using optical microscopy and ATR-FTIR, XRF, and XRD spectroscopy, confirming its suitability as a biosorbent. The analyzed isotherms showed that adsorption onto RHSs was best fitted by the Freundlich model, while adsorption onto MHSs was best fitted by the Temkin model. Kinetic studies demonstrated that the adsorption process is well described by the pseudo-second-order model, suggesting that chemical adsorption plays a significant role. The maximal adsorption capacity was 62.11 mg/g for RHSs and 80.65 mg/g for MHSs, highlighting the potential of hazelnut shells as an abundant, low-cost, and eco-friendly adsorbent. Furthermore, recycling studies indicated the feasibility of the adsorbent, underscoring its practical applicability in real scenarios.

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.

This study investigates trace element concentrations in surface waters of Lake Međuvršje and evaluates their environmental relevance within Serbian and EU regulatory frameworks. Seventy-five samples were analyzed for B, Ba, Cu, Mn, Ni, Pb, and Zn. Multivariate analyses (Pearson correlation, PCA, and hierarchical clustering) revealed distinct geochemical groupings, indicating both natural lithogenic influences and potential anthropogenic inputs. Censored data analysis showed that Ni, Pb, Zn, and B were dominated by values below the analytical detection limit, rendering conventional geostatistical interpolation inappropriate. These elements were therefore assessed using detection-based spatial analyses, whereas Cu, Mn, and Ba exhibited sufficient variability for quantitative spatial interpolation. This study highlights the importance of integrating regulatory assessment, multivariate statistics, and censoring-aware spatial analysis to ensure reliable interpretation of freshwater trace element distributions.