# Immobilised Humic Substances as Low-Cost Sorbents for Emerging Contaminants
[9] concluded that environmental waters in the UK contained approximately 70 pharmaceuticals belonging to different therapeutic classes, such as nonsteroidal anti-inflammatory drugs, \(\beta\)-blockers, antidepressants and the antiepileptic carbamazepine. Various technologies for the removal of emerging contaminants from the aqueous system have been developed, including oxidation, coagulation, precipitation, ion exchange and reverse osmosis [11; 12; 13]. However, these technologies have significant disadvantages, such as incomplete removal and high operating and maintenance costs, as well as high energy requirements [2]. Therefore, more effective and cost-efficient methods and technologies for the removal of pollutants from the aqueous environment are being sought. Adsorption is considered to be one of the most appropriate methods due to its simplicity and potential for regeneration. It is also economical and easy to set up [13]. Although many different sorbents have been used for the removal of metal, metalloid and organic substances so far, due to unsatisfactory efficiency and the high costs of these sorbents, opportunities are still open for finding new environmentally friendly and cost-effective sorbents. Recently, much attention has been paid to sorbents based on natural materials. There are numerous sorbents that contain unmodified raw materials, such as clay minerals [12] and lignitic humic substances (HSs) [14], and there are also sorbents based on natural materials like wood-based biochar [2], iron-modified peat [15], iron humate [16] and many others. Sorbents based on humic substances could be competitive among such materials, making contributions to reducing pollution. Humic substances (HSs), the products of degradation reactions of decaying organic matter, are the main component of soil organic matter that affects soil fertility. In addition, HSs are decisive in providing the turnover of organic carbon [17]. HSs are a general category of naturally occurring, biogenic, heterogeneous organic substances that can generally be characterized as yellow to black in color and of a high molecular weight. Moreover, the presence of carboxylic and phenolic hydroxyl groups in the HS structure ensures its acidic nature [18]. HSs can be tentatively classified as humic acid (HA), fulvic acid (FA) and humin, depending on their solubility [19]. HSs have many valuable properties, including that they are the main sorbent of organic and inorganic chemicals in soil. There are numerous studies investigating HSs as a sorbent for metals. [PERSON] and [PERSON] [14] concluded that the adsorption efficiency of HSs was 80-100%, and the stability of formed metal ion-humic complexes was high for copper and lead, even if it was lower for zinc and cadmium. In recent decades, HSs have been used as a sorbent in HPLC, capillary electrochromatography and solid-phase extraction, and in these applications, they are immobilized prior to use [20]. HSs are mostly used as a native substance, but recently, more attention has been paid to the methods of their chemical modification to improve their physicochemical properties. It is important to investigate different approaches to the modification of HSs, including immobilization, in order to obtain a new, improved material with prospective wide application. Moreover, to better understand the mechanism of sorption, it is also important to characterize the obtained sorbents. [PERSON] and [PERSON] [17] found the immobilization of HSs to be promising for investigating their interaction with different substances. The authors pointed out that immobilized HSs could serve as a sorbent for organic and inorganic substances, enabling the study of their interactions [17]. Furthermore, [PERSON] et al. [21] studied the hydration and water-holding properties of cross-linked HAs (a formaldehyde cross-linking procedure based on the covalent coupling of aromatic moieties of HSs) to obtain a low-cost material that could be used in agriculture and remediation technology.