Ligneous biochar research and development of technology for enhanced adsorption of potentially toxic elements

The dissertation is focused on production and modification ligneous biochar for enhanced adsorption of potentially toxic elements (PTEs) from synthetic solutions and landfill leachate. The main object of the research is adsorption of Cr³⁺, Cd²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Cu²⁺ by ligneous biochar. The goal is to assess adsorption of PTEs by biochar and develop technology for modification of ligneous biochar, possessing enhanced adsorption capacity for Cr³⁺, Cd²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Cu²⁺. The thesis approaches several tasks. Task 1, 2, 3 are conducted by experimental studies of the key adsorption mechanisms, biochar characteristics, modification methods, biochar-hydrogel composite swelling and adsorption studies. Task 4 is conducted by theoretical research and numerical modeling studies of fitting to dynamic intraparticle model for adsorption of PTEs by ligneous biochar.

The dissertation consists of three parts including the introduction, 3 chapters, conclusions and references. The introduction discusses the research problem, the relevance of the thesis, describes the object of the research, formulates the aim and objectives of the thesis, describes the research methodology, scientific novelty of the thesis, the practical value of the research findings, defended statements. At the end of the introduction, the publications and reports published by the author on the topic of the dissertation and the structure of the dissertation are presented.

Production technologies of biochar from ligneous feedstock, biochar characteristics and modification techniques, as well as mechanisms of adsorption of potentially toxic elements on biochar, equilibrium isotherms and kinetic models of adsorption are presented in Chapter 1. Chapter 2 presents theoretical and experimental methods of selection of feedstock with variable intrinsic properties for biochar production, physical and chemical characteristics of biochar, equilibrium and kinetic modeling of adsorption, modification with H₂O_2, FeCl₃, MgCl₂ and preparation of biochar-hydrogel composite.

Chapter 3 investigates the effect of modification methods on the adsorption capacity for potentially toxic elements of ligneous biochar and identifies the key mechanisms of adsorption, evaluates the biochar-hydrogel composite potential for application in adsorption of potentially toxic elements from synthetic solutions and landfill leachate, develops the dynamic intraparticle model for adsorption of potentially toxic elements by biochar.

7 publications focusing on the subject of the discussed dissertation were published: 4 articles – in scientific journals included in the Clarivative Analytics Web of Science list (3 of them with citation index), and 3 – in conference proceedings. The 1 patent of the Republic of Lithuania was granted. 8 presentations on the subject have been presented in conferences at national and international level.

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DOI: https://doi.org/10.20334/2020-017-M