## 1 Introduction  
Progressive development and industrialization significantly affect the natural environment, causing pollution with toxic chemical substances, such as medicines, artificial dyes, heavy metals, and chemical warfare agents. The spread of these compounds in the environment contributes to their incorporation into the animal food chain, and thus has an inextricable impact on human health [1]. Artificial dyes entering the aquatic environment along with sewage from the textile industry limit the light penetration, which results in the impaired photosynthetic activity of aquatic plants. One of the most serious threats is the textile industry, responsible for releasing an average of 20,000 tons of artificial dyes into the natural environment per year, accounting for 17-20% of the global water pollution [2, 3]. The dyes most commonly used in the textile industry are chemical compounds containing one or more azo groups in their structure. After entering the human body, azo dyes are transformed by the intestinal microflora into toxic intermediates, i.e., carcinogenic aromatic amines [4]. The toxicity of these amines results from their metabolic oxidation to diazonium salts, which, as electrophilic reducing intermediates, have the ability to form a covalent bond with DNA [5]. Due to its wide availability and low price, one of the dyes commonly used for coloring silk, cotton and wool fabrics, but also in the paper and tanning industry, is methylene blue, which belongs to the group of thioazo dyes [6]. As a result of metabolic processes,methylene blue is transformed into carcinogenic methylene amines and benzidine. Studies conducted on microalgae, i.e., _Spirulina platensis_ and _Chlorella vulgaris_, have shown that the increasing concentration of this pigment leads to the limited growth of these organisms and also causes a decrease in the concentration of chlorophyll in their cells, significantly contributing to limiting their development and photosynthetic abilities [7]. In the pharmaceutical industry, methylene blue is used as a drug against Alzheimer's disease [8], Malaria, and in the treatment of fungal infections of the skin, oral cavity and esophagus, digestive system, vagina, and vascular system in humans, caused by _Candida_ yeasts [9]. Another dangerous metabolite of methylene blue is a cationic dye--Azure B--which also can be incorporated into the structure of DNA and RNA. This metabolite is able to inhibit glutathione reductase in the human body, which is a key enzyme in maintaining cellular redox balance [10]. Therefore, it is extremely important to remove dyes such as methylene blue from the aquatic environment as effectively as possible. For this purpose, biological techniques such as biodegradation, chemical techniques such as flocculation, using metal ions as substances to induce this process, and physical techniques such as filtration, reverse osmosis, adsorption, or electrolysis are used. Due to its ability to handle high flow rates, low process costs, and high efficiency, adsorption is considered the most versatile water treatment process, especially in developing countries [11]. The possibility of controlling the pore size and chemical and physicochemical properties makes polymer adsorbents of increasing scientific interest [12]. In this publication, we propose polymer microspheres as an adsorbent for water treatment. Microspheres are particles ranging in size from 1 to 1000 \(\upmu\)m, characterized by a high surface area to volume ratio. Polymer adsorbents can take various forms, i.e., macroporous, hollow, nanofibers or core-shell [13]. The most frequently used methods for preparing polymer microspheres include emulsion or suspension polymerization, swelling polymerization, controlled polymerization, and precipitation polymerization. Since many factors influence the morphology of microspheres, one of the greatest challenges encountered during the synthesis of microspheres is preventing discrepancies in their shape and particle and pore size [14].