TURK 2025

One of the priority tasks in the field of environmental protection is the search for effective and eco-friendly wastewater treatment technologies from various types of pollutants.
This study aimed to obtain native and modified plant-based biosorbents and examine their adsorption capacity. Cotton stalks, tarragon wormwood, and walnut shells were used as raw materials for sorbents.
To achieve the objectives, chemical and physicochemical methods were applied. The concentration of a substance in the solution was determined using spectrophotometric method.
Modification was carried out with a 0.8–1% sodium hydroxide solution under static conditions (1:30 solid-to-liquid ratio) for 3 hours at room temperature with continious stirring. Then the mixture was filtered, washed with water until a neutral reaction, dried, and used as a modified adsorbent.
It was found that after modification, the adsorption capacity of cotton and tarragon increases almost twofold. For example, for iodine: cotton stalks - from 12.63% to 24.44%, tarragon wormwood - from 11.21% to 24.07%. Similar results were observed for methylene blue adsorption.
When determining Cr⁶⁺ using 1,5-diphenylcarbazide, the water under study was added to the resulting adsorbent in a ratio of 0.5 g: 50 ml and the optical density was measured at 540 nm. The content of chromium ions was recorded by spectrophotometric methods for 1, 3, 6, 24, 48 and 144 hours of contact of biosorbents with solutions.
The applied purification method ensures a high chromium removal efficiency (80–95%). Walnut shells showed an increase in efficiency from 75.6% to 94.8%, while tarragon mass improved from 67.6% to 89.3%. Modified biosorbents were found to be more effective in chromium ion adsorption compared to their native forms.
The concentration of unbound heavy metal ions was determined using calibration curves based on the optical density of absorption bands.