THE EFFECT OF THE TYPE AND CONTENT OF CARBONATES ON THE CHARACTERISTICS OF POROSITY OF CERAMIC MEMBRANES

Water and Water Purification Technologies. Scientific and Technical News ISSN 2218-9300 THE EFFECT OF THE TYPE AND CONTENT OF CARBONATES ON THE CHARACTERISTICS OF POROSITY OF CERAMIC MEMBRANES O. Yanushevska1 1 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Ukraine, DOI: https://doi.org/10.20535/2218-930012023275757 The main issue considered in the work is the creation of a matrix for ceramic membranes, which would be distinguished by low cost and high porosity. In order to reduce the cost of ceramic membranes, a widespread approach was chosen, which is powerfully used by many researchers, namely the use of natural minerals - kaolin and saponite - as the main components of the matrix. Carbonates were used as pore generating agents to achieve the required porosity value. Three series of ceramic membranes (CM) differing in chemical composition were synthesized in the work: KP1, KP2, and KP3 series. The main composition of CM includes: kaolin, saponite, sodium silicate and carbonates. The effect of the type and amount of carbonates (CaCO3, NH4HCO3, (NH4)2CO3) as pore generating agents on the formation of the porous structure of the samples was studied. The type and content of carbonates varied in different samples from 8 wt% up to 40 wt%. The dry pressing method using pressure equivalent to 8 tons and 15 tons was used to form ceramic membranes. The main parameters by which the properties of ceramic membranes were evaluated: water absorption, total and open porosity. Standard methods were used to determine these parameters for synthesized samples. The chemical composition of the dry mixture of the ceramic membrane, for which the porosity is the maximum in the series of manufactured samples, was established. It was established that the addition of calcium carbonate components to the dry mixture increases the porosity of ceramic membranes and water absorption. The chemical composition of a ceramic membrane sample with the best indicators of total and open porosity in the KP2 series is given. The chemical and phase composition of samples of the KP2 series, as well as their structural and adsorption characteristics, were investigated by X-ray fluorescence and diffraction methods of analysis and low-temperature nitrogen adsorption-desorption. The effect of the addition of silicon carbide on the characteristics of the porosity of the samples was determined. Keywords: calcium carbonate, ceramic membranes, chemical composition, dry pressing method, pore generating agent, porosity Received: 21 March 2023 Revised: 10 June 2023 1. Introduction The global problem of water pollution is becoming increasingly acute due to rapid industrialization. The need for effective purification of water of various origins, in particular in conditions of remote location of МАТЕРІАЛИ ТА ОБЛАДНАННЯ ДЛЯ ВОДОПІГОТОВКИ Accepted: 12 June 2023 treatment facilities, requires the use of membrane technologies, such as allow creating convenient mobile membrane modular installations. Membrane methods are universal and free of many disadvantages of other water purification methods, such as oxidation, adsorption, coagulation and 46 Water and Water Purification Technologies. Scientific and Technical News flocculation (Yang, 2020; Delcolle, 2017). Membrane separation, in particular with the use of ceramic membranes, has a number of advantages: ease of operation and regeneration, absence of additional reagents, high productivity, long service life, etc. (Ha, 2015). Recently, the methods of using natural materials to create ceramic membranes are gaining increasingly popularity in order to make cheaper of CM, since the high cost of their production still remains one of the disadvantages of using CM (Kuzminchuk, 2023; Serhiienko, 2023). One of the important properties of ceramic membranes is the porosity of the membrane matrix, which ensures its transport characteristics, and therefore its efficiency. The porosity of ceramic membranes is ensured by the addition of so-called pore generating agents. It is possible to regulate the overall porosity of the ceramic matrix by changing the type and amount of pore generating agent. For example, in work (Kaur, 2016) different amounts of calcium and sodium carbonate were added to kaolin-based ceramic matrices. The matrix composition was as follows: kaolin (55–95 wt%), Na2CO3 (0–40 wt%), CaCO3 (0–40 wt%), boric acid (2.5 wt%), sodium metasilicate (2.5 wt%). The addition of calcium carbonate increased the porosity and chemical stability of the samples, and the addition of sodium carbonate increased the pore-density by reducing their diameter. It was concluded that the content of CaCO3 is 20 wt % makes it possible to obtain a sample with a pore size of 0.5 μm, a porosity of 37 % and a bending strength of 48 MPa. This sample showed good results in the separation of oil-in-water emulsions – 98 % oil rejection at a transmembrane pressure of 103 kPa. ISSN 2218-9300 In (Simão, 2015), the authors studied the influence of the amount of limestone (10 wt% and 20 wt%) on the porosity and bending strength of ceramic bodies that were formed from kaolin, potassium feldspar (KAlSi3O8), albite (NaAlSi3O8), quartz and white clay in different ratios The obtained ceramic bodies showed an apparent porosity from 28 wt% to 32 wt%, flexural strength from 7 MPa to 29 MPa. A sample containing kaolin (50 wt%), limestone (20 wt%), potassium feldspar (10 wt%), albite (10 wt%) and quartz (10 wt%) showed the best microfiltration properties for removing suspended solids from liquid suspensions. To prepare inexpensive ceramic matrices, the authors (Lorente-Ayza, 2015) used the following components: a Spanish clay mixture, chamotte taken from fired calcite and potato starch. Calcite was used as a pore generating agent in the amount of 15 wt% and 20 wt%. Studies have shown that such ceramic composites are cheap and can serve as microporous material with porosity values ranging from 28 % to 31 %. The study (Aripin, 2022) shows the use of calcium carbonate from onyx stone as a pore generating agent in a ceramic membrane based on kaolin, zeolite, and silica xerogel composites. Four different samples were made with different calcium carbonate content (from 5 wt% to 30 wt%), the sintering temperature of the samples was 1200 °C. It was established that the volume fraction of interconnected pores depends on the content of calcium carbonate. The sample with its content of 30 wt% provides the largest volume fraction of homogeneously interconnected pores, which in turn provides the largest value of the permeate flow. The effectiveness of the separation properties of the membrane was tested in the process of MATERIALS AND EQUIPMENT FOR WATER TREATMENT 47 Water and Water Purification Technologies. Scientific and Technical News removing non-sugar impurities in coconut juice. 2. Materials and Methods The following raw materials and reagents were used for the synthesis of (...truncated)