*2.2. Samples Preparation*

Environmentally safe, biodegradable hybrid hydrogel materials based on hydroxypropyl methylcellulose (HESBHM based on hydroxypropyl methylcellulose) were received using the watering method with hydroxypropyl methylcellulose solutions at a concentration of 8% wt. by dissolving the polymer in a mass ratio of 8:100 hydroxypropyl methylcellulose: distilled water heated to 90–100 ◦C. After that, a defined amount of sodium alginate (2.5% wt.) was added to the previously prepared hydroxypropyl methylcellulose (8% wt.) solution and allowed to mix homogeneously on a magnetic stirrer (magnetic stirrer MM-7P). To analyze the properties of the HESBHM based on hydroxypropyl methylcellulose, solutions of hydroxypropyl methylcellulose and sodium alginate were received at different concentrations of humic acids (5, 10, 15% wt.). A total of 20 parallel experiments were carried out for each composition of HESBHM.
