Author, Institution: Evelina Švedaitė, Kaunas University of Technology
Science area, field of science: Technological Sciences, Chemical Engineering, T005
Research Supervisor: Prof. Dr. Kęstutis Baltakys (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005)
Dissertation Defence Board of Chemical Engineering Science Field:
Prof. Dr. Raimundas Šiaučiūnas (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005) – chairperson
Assoc. Prof. Dr. Joana Bendoraitienė (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005)
Assoc. Prof. Dr. Jolanta Rousseau (Artois University, France, Technological Sciences, Chemical Engineering, T005)
Prof. Dr. Ramūnas Skaudžius (Vilnius University, Natural Sciences, Chemistry, N003)
Prof. Dr. Eugenijus Valatka (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005)
Dissertation defence meeting will be at Rectorate Hall of Kaunas University of Technology (K. Donelaičio 73 – 402, Kaunas)
The doctoral dissertation is available at the library of Kaunas University of Technology (Gedimino 50, Kaunas) and on the internet: E. Švedaitė el. dissertation.pdf
© E. Švedaitė, 2026 “The text of the thesis may not be copied, distributed, published, made public, including by making it publicly available on computer networks (Internet), reproduced in any form or by any means, including, but not limited to, electronic, mechanical or other means. Pursuant to Article 25(1) of the Law on Copyright and Related Rights of the Republic of Lithuania, a person with a disability who has difficulties in reading a document of a thesis published on the Internet, and insofar as this is justified by a particular disability, shall request that the document be made available in an alternative form by e-mail to doktorantura@ktu.lt.”
Annotation: This dissertation examines the removal of phosphorus from aqueous solutions with the aim of reducing eutrophication and ensuring the sustainable use of phosphorus as a critical raw material, by investigating the properties of Ca–Si adsorbents synthesized from opoka and calcium oxide, their effectiveness in removing phosphorus, and their potential applications in agriculture. The results contribute to the implementation of circular economy principles, reduce dependence on primary phosphorus resources, and promote sustainable nutrient management. Experimental studies employed methods for determining the chemical and mineral composition, thermal stability, and adsorption properties of the materials. The microstructure of the adsorbents was analyzed, adsorption kinetic and isothermal parameters were evaluated, and mathematical modeling was applied. The studies showed that opoka is a suitable raw material for the synthesis of Ca–Si adsorbents, with those synthesized by the hydrothermal method (200 °C, 16 h, CaO/SiO₂ = 1.5) exhibiting a high phosphorus adsorption capacity (>200 mg/g) and up to 98% removal efficiency at a concentration of 0.2 g P(V)/L. The adsorption proceeds via a pseudo-second-order mechanism and is governed by chemisorption, resulting in the formation of hydroxyapatite and, at higher concentrations, brushite. By applying a response surface model, optimal process conditions were determined, allowing for the prediction of the adsorption rate and duration. It was found that the spent adsorbents can be used as fertilizer components, leading to an increase in wheat yields from 4354 to 4857 kg/ha and enabling the removal and reuse of phosphorus.