Synthesis and Characterization of Nanozeolite from Sugarcane Bagasse Ash and Its Nutrient Loading Potential

Sugarcane bagasse, a known agricultural waste product in the Philippines with 88% silica (SiO2) content based on elemental analysis, is a viable starting material for zeolite synthesis. In this study, silica derived from sugarcane bagasse ash (SBA) collected from La Carlota, Negros Occidental, Philippines, was extracted via an alkaline extraction method using 2M NaOH and precipitation with 5 N H2SO4 under constant stirring at elevated temperature. Sodium aluminate was added as aluminum source then subjected to ageing at 80 degrees C for 72 h to form the clinoptilolite-type zeolite crystals. Characterization using Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy and X-Ray Diffractometry confirmed the successful synthesis of the SBA silica and clinoptilolite, with an Si/ Al ratio of 1.59 and average pore diameter of 85.77 nm. Surface modification was done by adding CTAB, a cationic surfactant. Nutrient loading was performed using synthesized nanozeolite (SNZ) for N and K loading and surface modified synthesized nanozeolite (SMSNZ) for PK loading which was compared with nutrient loading performance of commercial natural zeolite. The nanozeolite was added to 1 M urea for N loading, 1 M potassium chloride (KCl) for K loading, and 1 M potassium dihydrogen phosphate (KH2PO4) for PK loading at 1:10 (solid: liquid) solution ratio for 8 h under constant stirring followed by filtration and air drying. Chemical characterization of the synthesized nanozeolite revealed that it has a total CEC of 199.30 meq 100 g(-1), ICEC of 182.51 meq 100 g(-1), and ECEC of 16.79 meq 100 g(-1). Nutrient loading resulted in a 9.62% N and 17.01% K2O content using SNZ and a 13.35% P2O5 and 16.26% K2O content using SMSNZ, which were relatively higher compared to using a commercial natural zeolite. These can be attributed to the high internal CEC due to the high quantity of nanopores in the zeolite, which can capture and store the K+ and NH4+ ions via geometric fit, then release them to the soil ondemand via ion-exchange or occlusion. The surface modification with a surfactant drastically alters the surface chemistry of zeolite allowing simultaneous adsorption of anions (PO4-) externally and cations (K+) internally. The chemical characterization confirmed successful loading of N, K, and PK to synthesize nanozeolite from SBA-derived silica, and its potential as a controlled release fertilizer can be tested in further studies.