Enhanced-efficiency urea fertilizers from organic palygorskite and carnauba wax

Sustainable agriculture has gained prominence in recent decades, mainly due to its potential to mitigate adverse environmental impacts. In this study, new fertilizers were produced through mechanochemical activation to enhance urea-release efficiency. For this purpose, raw and organophilized palygorskite clays and urea were used. To obtain the hybrid fertilizers, the clays and urea were mixed (1:1) in a ball mill (for 3 h) to promote interaction between the materials. The resulting material was placed into a mold and subjected to pressing (2 ton/10 s). The fertilizers were then encapsulated with melted carnauba wax (CW) using the dip-coating technique. The samples were characterized through chemical analysis, mineralogical, thermal, and surface behavior. Urea release was evaluated through dissolution tests in aqueous solutions and leaching experiments in soil columns. The results indicated that the hybrid fertilizers exhibited lower urea release rates, starting at 30 min (PN/U = 3.4%, PWB/U = 3.5%, PTA/U = 6.8%, samples with CW = 0%), compared to the commercial fertilizer samples (U = 100%). Hybrid fertilizers without the CW coating showed limited urea release during the first 6 h. In contrast, CW-hybrid fertilizers demonstrated complete release from the 9th day (PTA/U/C) and the 27th day (PN/U/C), which was attributed to the rupture of the coating barrier. All samples developed in this study demonstrated greater efficacy than commercial urea. However, the application of CW coating played a crucial role in prolonging urea retention and improving the efficiency of all developed samples.