Among the polysaccharides currently under investigation for these purposes, sodium carboxymethyl cellulose (CMC), chitosan (CS), and sodium alginate (SA) are the most widely used due to their ease of processing and excellent film-forming abilities. However, their hydrophilicity and low mechanical strength have limited their use individually. To optimize their properties, CMC, CS and SA were combined in the presence of glycerol as a plasticizer in composite films by the solvent casting method, studying the effects of different concentrations and weight ratios between them on some water interaction properties (degree of swelling, water solubility, water vapour permeability and moisture content) and thermal and mechanical properties, since mulching films must maintain the structural integrity of the material when exposed to high temperatures or excess water. To rationalize the macroscopic behavior of the composite films, infrared spectroscopy and X-ray diffraction were used to obtain information on the interactions and structural changes induced by the salt. This approach allowed the identification of the best quality films as well as the composite films obtained with a concentration of each polymer of 1.5 wt% and with a weight ratio between the CS/SA and CMC dispersions of 1:1 and 17:3, respectively. 

The films were enriched with an appropriate % of NH4H2PO4 salt as fertilizer and the release kinetics of NH4+ and PO43- ions were studied. The latter aspect is of great importance as the release of N and P helps to improve the nutrient supply to the soil, thus reducing the use of synthetic fertilizers.

Results were presented as posters and oral presentations at the "XLIX Congress of the Physical Chemistry Division of the Società Chimica Italiana. Physical Chemistry: a fresh glimpse into the microscopic world" in Turin, 4-7 September 2023 and at the "Convegno Congiunto delle Sezioni Sicilia e Calabria della Società Chimica Italiana" in Palermo, 11-12 December 2023. In this last event, the scientific contribution has been rewarded with a scholarship by the Board of the Sicilian Section of the Società Chimica Italiana.

Next step

To characterize films based on CMC, CS and SA, enriched with both the NH4H2PO4 salt and biochar, and how the latter influences the properties useful for the purpose for which they were designed, i.e. to develop an innovative approach whereby fertilizer and soil improver are released during film biodegradation. This could provide promising and useful solutions to a major problem in the agricultural sector.