Urea-Loaded Hydroxyapatite–Carboxylated Cellulose Composites as Slow-Release N Fertilizer Pellets for Efficient Delivery of Nitrogen

• Published in: Industrial & engineering chemistry research 2023-09, Vol.62 (37), p.14853-14865
• Main Authors: Channab, Badr-Eddine, Elhassani, Chirâa Elidrissi, Essamlali, Younes, Marrane, Salah Eddine, Chakir, Achraf, Zahouily, Mohamed
• Format: Article
• Language: English
• Subjects: Applied Chemistry
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.3c00737

Nitrogen (N) is the most widely applied macronutrient to maintain soil fertility. However, the conventional N fertilizers applied to the soil are generally of low N use efficiency due to N loss by means of lixiviation and volatilization. Therefore, the application of slow-release N fertilizers is one of the advanced solutions to overcome these issues. The purpose of this study is to develop new slow-release N fertilizers (N-SRFs) pellets using oxidized cellulose nanocrystals (CNCOX) and citric acid grafted cellulose nanocrystals (CNCCA) modified natural hydroxyapatite hybrid nanocomposites (HAP–CNCox and HAP–CNCCA) as a carrier for nitrogen delivery. The HAP–CNCox and HAP–CNCCA hybrid composites were prepared by an in situ wet chemical precipitation method using phosphate rock as a source of calcium (Ca2+) and phosphorus (PO4 3–). Urea was immobilized onto the CNC–HAP composites in an aqueous solution to produce three N-SRF formulations: HAP–urea, HAP–CNCox–urea, and HAP–CNCCA–urea. Fertilizer formulations were fully characterized by means of structural (FTIR and DRX) and morphological (SEM) tools, and the results demonstrated that urea molecules are strongly bonded to HAP and HAP–CNC composites through several mechanisms including H-bonding, metal–ligand interactions, and physical storage within the existing micro- and nanopores. The water release experiment of developed N-SRFs demonstrated that the developed SRFs displayed a slow-release N property and required 18 days for a complete N release in water compared to the pure urea, which dissolves rapidly within the first 3 h. The release kinetics of urea in water was best described by Korsmeyer–Peppas, while the release mechanism in water is best described by a first-order kinetic model.