Isotherms of methylene blue adsorption of active carbons from sludge-lignin according to the data of the planned experiment

Active carbons are used in various industries, as well as in wastewater treatment systems for specific compounds, including organic substances with a large molecular weight. Adsorbents with certain properties and structures are necessary for the effective implementation of the process. In this work, the process of synthesis of active carbons was modeled by the method of the planned experiment. Adsorbents were prepared by pyrolysis of sludge-lignin by thermochemical activation with sodium hydroxide as the activating agent. Isotherms of the adsorption of methylene blue were obtained, which were processed in the coordinates of the linear forms of the Langmuir and Freundlich equations. The constants of these equations were calculated, which served as the output parameters of a three-factor rotatable central compositional plan of the second order. Mathematical models are obtained that connect the coefficients of the Langmuir and Freundlich equations with the pyrolysis conditions, which can be used to determine the adsorption properties of synthesized samples of activated carbons, that is, practically predict the amount of adsorption of methylene blue in a given range of pyrolysis conditions, without conducting experimental studies.