Sustainable coating material based on chitosan-clay composite and paraffin wax for slow-release DAP fertilizer

• Published in: International journal of biological macromolecules 2020-10, Vol.161, p.492-502
• Main Authors: El Assimi, Taha, Lakbita, Omar, El Meziane, Abdellatif, Khouloud, Mehdi, Dahchour, Abdelmalek, Beniazza, Redouane, Boulif, Rachid, Raihane, Mustapha, Lahcini, Mohammed
• Format: Article
• Language: English
• Subjects: Chitosan - chemistry; Chitosan composite; Clay - chemistry; Coating; Controlled and slow release fertilizer; Fertilizers; Paraffin - chemistry; Phosphates - chemistry; Phosphorus - chemistry; Polymers - chemistry; Soil - chemistry; Water - chemistry
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2020.06.074

The coating of fertilizers by polymers is one of the most efficient tools for their slow and control release into soil. This strategy avoids excessive use of the fertilizers and increases their availability to the crops needs. In the present paper, hydro-soluble diammonium phosphates (DAP) fertilizer was double coated following the dip-coating process by chitosan-clay composites as inner coating and paraffin wax as an outer coating. The chitosan composite preparation and characterization were deeply investigated. The montmorillonite (MMT) clay incorporation as filler improves the water barrier diffusion, mechanical properties, and thermal stability of the composite. The combination of the swelling behavior of the chitosan-clay composite (inner coating) and the hydrophobic property of paraffin wax (outer coating) was confirmed by the water holding capacity evaluation and the phosphorus release essays in water and soil. Indeed, the phosphorus dissolution from the coated DAP granules was significantly delayed compared to the uncoated DAP. Moreover, the biodegradation study of composite material in soil and the biochemical oxygen demand (BOD) tests revealed that the coating system proposed could be considered as a carbon source for microorganisms after the fertilization process, which confirms its sustainability. [Display omitted] •Sustainable double-coating approach of DAP fertilizer for the slow-release properties.•The intercalation of clay galleries by the chitosan chain affects the diffusion kinetic of water across the coating material•The phosphorus dissolution rate was considerably delayed in water and soil with a qusi-Fickien diffusion mechanism.•The combination of hydrophobic property and water holding capacity in the proposed coating system for slow release DAP fertilizer was approved.•The biodegradation study reveals that the process of biodegradation could be considered as controlling factor of the nutrients release in soil.