Adsorption of methylene blue by activated pyrolysis products of sunflower seed husks

in the context of the global environmental crisis caused by the rapid growth of industrial and household waste, the search for effective methods of their recycling is becoming a key task of sustainable development. Traditional disposal methods, such as burial or incineration, not only require significant resources, but also lead to atmospheric pollution with negatively biologically active gases. In this context, pyrolysis of carbon-containing waste represents a promising alternative combining environmental safety and economic feasibility. Unlike combustion, pyrolysis takes place in an environment with a limited oxygen content, which minimizes CO and CO2 emissions, and also allows for the production of valuable secondary products — pyrolysis gases, liquid and solid carbon materials. The latter are suitable for use as adsorbents. Activation of pyrolysis products by chemical reagents (alkalis, acids, or steam) is used to increase the adsorption capacity, which significantly increases their porosity and adsorption capacity. In this work, the adsorption properties of sunflower husk pyrolysis products activated with an aqueous 2 M solution of potassium hydroxide (KL-21(A)), sunflower husk pyrolysis products combined with bentonite clay (KL-21(A)) and pyrolysis products of crushed worn car tires (KR-21(A)) were determined. Their effectiveness in terms of adsorption of methylene blue (MG), a model cationic dye widely used in assessing the absorption capacity of adsorbents, has been studied by spectrophotometric method. Kinetic dependences of adsorption have been established, and the maximum adsorption capacities of experimental materials have been determined depending on MG concentration. The results of experimental studies allow us to conclude that the activation of pyrolysis products of crop and communal waste with potassium hydroxide improves the adsorption characteristics of the developed material. Objectives: to identify the adsorption properties of pyrolysis products of sunflower seed husk KL-21(A) activated with an aqueous 2 M solution of potassium hydroxide, pyrolysis products of sunflower seed husk combined with bentonite clay KL-21(A) and pyrolysis products of worn-out automobile tires KR-21(A). Methods. A Nabi MicroDigital spectrophotometer (South Korea), laboratory instruments and reagents were used to study the adsorption properties by the spectrophotometric method. Results. Graphical dependences of the absorption capacity on the duration and rate of adsorption are revealed, and adsorption isotherms are constructed and analyzed. Conclusions. An adsorption-active material based on pyrolysis products of sunflower seed husks and pyrolysis products of worn-out automobile tires was obtained. The adsorption capacity of CL-21(A) samples was 474 mg/g, CLG-21(A) – 131 mg/g, and KR-21(A) – 351 mg/g. The obtained isotherms are determined by the Langmuir model. It was found that the adsorption equilibrium occurs after 6 hours in KL-21(A) and a day later in KL-21(A) and KR-21(A). It was found that the highest rate of adsorption is characteristic of the KL-21(A) sample and amounted to 0.00094 mmol/min or 0.300 mg/min in the first 15 minutes of exposure.

утилизация, отходы агропромышленного комплекса, коммунальные отходы, лузга семян подсолнечника, изношенные автомобильные покрышки, адсорбция, метиленовый голубой, изотермы адсорбции