Parametric and Optimization Studies on the entrapment of Potassium Fertilizer into Chitosan-Poly(methacrylic acid) Carrier via Ionic Gelation

Department of Chemical Engineering, College of Engineering and Agro-Industrial Technology, University of the Philippines Los Baños, Los Baños, Laguna 4031, Philippines

Corresponding author: vpmigo@up.edu.ph

Abstract

Nanofertilizer is an emerging technology for exhibiting slow release mechanism of fertilizer application. This slow release mechanism allows increase in nutrient uptake of plants while minimizing environmental pollution; specifically, reducing eutrophication in bodies of water. This study includes parametric and optimization studies for ionic gelation process in the formulation of potassium fertilizer in chitosan polymethacrylic acid (CS-PMAA) carrier, and subsequent characterization of the formulated K fertilizer. A 2k factorial experimnental design was initially implemented to determine significant factors. Results show that polymerization time inversely affects the K content concentration of the K-CS-PMAA fertilizer due to the swelling behavior of chitosan, while K:CS-PMAA ratio directly affects the K content concentration. Upon numerical optimization, the conditions found to maximize K content of the formulated fertilizer are 3000 ppm K⁺ corresponding to 1.5:1 ratio of the K loading concentration to CS-PMAA carrier for 30 mins polymerization time. The optimum K content of K-CS-PMAA fertilizer is about 34.98% w/w – less than the 44.27% w/w K content of the fertilizer grade, muriate of potash (MOP). The Dynamic Light Scattering (DLS) and Scanning Electron Microscope (SEM) results of 368.1 nm and 75.4 nm, respectively, indicated that K-CS-PMAA is nanosized. The Fourier Transform Infrared Spectroscopy (FT-IR) results proved the presence of CS-PMAA with deviations at 1483.01 and 1405.07 caused by the vibration in the --COO^-anion groups of PMAA indicating the attachment of potassium in the nanoparticle. Furthermore, the fertilizer formulated was proved to exhibit slow release behavior with the value of 83.70% K⁺ release after 48 hours compared to the 99.43% release of MOP.