Young researchers for 2025-2026
III. Biotechnologies and Environmental Protection
Waste, plastics and pollutants
Institute of Chemistry, MSU
Laboratory of Ecological Chemistry, Institute of Chemistry, MSU
- Dr. Irina CEBAN
- Dr. Oleg PERUHOV
- Mihaela BUGA
- Eugenia MORARU
The project proposes the production of an eco-friendly activated carbon from local waste, such as plum pits/walnut shells, using a chemical activation method with citric acid. Choosing this biocompatible acid instead of more aggressive conventional chemical agents ensures a sustainable and environmentally friendly process. Citric acid acts as a dehydrating agent and a precursor for porosity, facilitating the development of a high specific surface area and a pore structure suitable for pollutant adsorption. The activation process involves impregnating the precursor material with a citric acid solution, followed by controlled thermal treatment to induce carbonization and develop the porous structure. In this study, the obtained activated carbon will be characterized through physicochemical analyses, such as specific surface area determination (BET), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM), to evaluate its structure and adsorptive properties. The resulting material will be tested for the removal of an inorganic pollutant from water, such as lead (Pb²⁺) or cadmium (Cd²⁺) ions, which are heavy metals with a significant impact on human health and ecosystems. This study will assess adsorption efficiency and establish optimal conditions for the use of activated carbon in water treatment applications. To tailor the project to the specific context of the Republic of Moldova, it is recommended to focus on pollutants found in local waters. According to available data, groundwater and surface water in Moldova often contain high concentrations of fluoride, boron, nitrites, nitrates, and heavy metals, exceeding the permissible limits for drinking water. Additionally, pollution levels in the Nistru and Prut rivers have increased, affecting the quality of the country’s water resources. By utilizing local waste and an eco-friendly activating agent, the project contributes to the development of a sustainable water remediation solution, while also reducing the environmental impact of organic waste. The results may provide a viable alternative to conventional materials used in purification processes, promoting circular economy principles and environmental protection.
Summary of the activity and results obtained in 2025
In the Republic of Moldova, the nut sector represents an important agricultural field due to the high quality of cultivated varieties and the expansion of Juglans regia (Chandler variety) plantations. Walnut shells, an agricultural by-product generated in large quantities, are typically left unused, despite their suitability for producing activated carbon. Biomass-derived activated carbon is valued for its effectiveness in removing heavy metals, dyes, and volatile organic compounds from water, owing to its porosity and the diversity of functional groups on its surface. Previous studies have shown that agricultural biomass, including walnut shells, can be an effective precursor for producing adsorbent materials.
This study analyzes the process of transforming Chandler walnut shells into activated carbon using chemical activation with citric acid. Citric acid is a biocompatible activation agent capable of creating functional groups that enhance the adsorption performance of the raw material. The walnut shells were collected from the village of Tîrșiței, Telenești district, and crushed to obtain granulometric fractions of 0.8–2.0 mm. The shells were impregnated with citric acid solutions at concentrations of 30%, 50%, and 70 %, followed by carbonization at temperatures of 350 °C and 450 °C for 2 hours, with a heating rate of 10°C/min. Thermogravimetric (TG, DTA, DTG) and X-ray diffraction analyses were used to evaluate the thermal behavior and chemical structure of the materials.
The results showed that impregnation with citric acid significantly altered the chemical structure of the walnut shells. After carbonization, it was observed that the samples treated at 350°C had a higher yield (ranging from 18% to 45%) compared to those treated at 450°C (ranging from 9 % to 29 %). This result suggests that temperature plays an important role in obtaining activated carbon with optimal characteristics. X-ray diffraction analyses confirmed the presence of citric acid in the impregnated samples, particularly in the CN-6 sample, which displayed distinct peaks in the diffraction range of 15–40°, indicating efficient impregnation of the shells with citric acid.
In conclusion, it was demonstrated that walnut shells impregnated with citric acid could represent a valuable and environmentally friendly source for producing activated carbon, with significant potential for use in water purification processes and other ecological applications. Further testing will be conducted to assess the adsorption capacity of the obtained material, and the most efficient samples will be used to reproduce larger quantities and carry out additional experiments. The results of this study will contribute to the valorization of an agricultural by-product.
Abstracts
- CEBAN, I., PETUHOV, O., BUGA, M., MORARU, E. Thermal characterization of walnut shells: a preliminary stage in the production of activated carbon for water purification. În: 34th Symposium on Thermal Analysis and Calorimetry "Eugen Segal" of the Commission for Thermal Analysis and Calorimetry of the Romanian Academy. 23-24 October, 2025, Bucharest (Romania). https://www.researchgate.net/publication/397996980_Thermal_characterization_of_walnut_shells_a_preliminary_stage_in_the_production_of_activated_carbon_for_water_purification
- CEBAN, I., PETUHOV, O., BUGA, M., MORARU, E. Obtaining activated carbon by chemical method by utilizing local waste. În: MEDICINE, MOLECULAR AND ENVIRONMENTAL SCIENCES International Congress. 10-15 November, 2025, Chisinau (Republic of Moldova) Book of Abstract, 2025 p. 166. DOI: https://doi.org/10.19261/medmol25, https://www.researchgate.net/publication/397997462_Obtaining_activated_carbon_by_chemical_method_by_utilizing_local_waste