This review highlights the preparation, properties, and versatile applications of nanocellulose-based hydrogels from agricultural wastes, focusing on sustainability, biomedical use, packaging, water purification, and future development trends.

In this work, we report rice husk ash prepared via a thermal treatment process used as oil sorbents for oil spill cleanup. The oil sorbent with highly porous structures shows a crude oil sorption capacity of 15 g/g. The rice husk ash was studied on the basis of phase composition, microstructure and morphology using X-ray diffraction analysis, FTIR spectrometry and scanning electron microscopy (SEM). The results of the SEM studies strongly indicate that thermal treatment is a suitable method to improve structure of husk particles regarding porosity compared to virgin samples.

This study focuses on the synthesis and characterization of buckwheat husk-derived activated carbon, chemically activated with potassium hydroxide (KOH) and subsequently modified with urea and Prussian Blue (PB). The obtained carbons were evaluated in terms of particle-size distribution, surface morphology, structural features, and electrokinetic properties using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and electrophoresis, as well as N₂ adsorption–desorption (BET surface area and porosity analysis). The results confirmed that both pyrolysis conditions and the type of modifier significantly affect the physicochemical properties of the activated carbon and its behavior in electrolyte solutions. Colloidal stability and particle size were strongly dependent on pH and the type of anions present in solution, with sodium nitrate (NaNO₃) systems showing higher stability than sodium chloride (NaCl). Modification with KOH and urea imparted a more basic surface character, whereas PB introduced more acidic properties. All samples exhibited predominantly negative surface charges and mesoporous structures, which are favorable for adsorption processes and enhance affinity for heavy-metal cations. Among the tested materials, BH-KOH-Fe (Fe-modified KOH-activated carbon) showed the most favorable performance for the targeted application, while BH-KOH (KOH-activated buckwheat husk-derived carbon) exhibited high surface area and good colloidal stability. The prepared materials show promising applicability for water purification, including the removal of organic pollutants and radionuclides (e.g., ¹³⁷Cs and ⁹⁰Sr), as well as metal cations (K⁺, Na⁺, and Li⁺).

In the paper ways of using rubber crumb from worn tires were investigated. Possibilities of preparing Rubber-Bitumen Compounds (RBC) based rubber crumb (RC) from worn tires were studied experimentally. The physico-mechanical characteristics of paving bitumen BND 60/90 modified with rubber crumb and spent engine oil. The structure of rubber crumb was characterized by optical microscopy. Physico-mechanical characteristics of RBC were detrminated by standard methods. It is established that the quantity of entered binders depending on physical and chemical conditions, which was optimal composition of rubber-oil at a ratio of 1:1 and 3:2 and introduction to bitumen in amount of 15-25 wt.%.