Production of Acid-Activated Sorbents From Plant Raw Materials and Their Testing for Dye Removal From Model Solutions

The study addresses the pressing issue of obtaining new sorbents from plant raw materials and their use for purifying water systems containing hazardous dyes. In the research, the method of chemical kiloton activation is applied to acquire new sorbents, and its advantages are outlined. Three samples of sorbents were obtained: a lignocellulosic sorbent based on walnut shell, which underwent no treatment with chemical reagents; the second sample was obtained by treating a lignocellulosic raw material with a 65 % solution of nitric acid (HNO3); the third sample - with a 65 % solution of acetic acid (CH₃COOH). The chemical activation of sorbents was carried out by the impregnation method in a water bath and rinsing with distilled water until reaching pH = 7—8, followed by gradual drying, initially at temperatures of 60—65 °C, then at 100—105 °C for 1—2 hours, and finally at 125—130 °C until a constant mass was achieved. At the last stage, the material was ground, selecting fractions of 10 mm in size. The prepared sorbents were tested for their efficiency in removing methyl orange dye from model solutions. A comparative analysis of sorbent samples regarding dye removal from model solutions was conducted. It was found that the use of chemically activated lignocellulosic sorbent with acetic acid (CH₃COOH) solution is more effective compared to nitric acid (HNO3) and non-activated sorbent. The optimal consumption rate of kiloton-activated lignocellulosic sorbent was found to be 1.5 g/dm3, with a purification efficiency of 80 %. The optimal contact time of the lignocellulosic sorbent with the adsorbate is 20 hours. The influence of temperature on the dye sorption process was investigated in the range from 291 to 303 K. Increasing the temperature to 303 K resulted in achieving a purification efficiency of 86 %.