Sustainable synthesis and characterization of nano-triple superphosphate from solid marine wastes

Abstract

Today, it is vitally important to develop an environmentally sound source for the manufacturing of phosphate fertilizers, as the availability of mineral rock phosphate is diminishing day by day. The present study focuses on the utilization of solid marine wastes from snail and cockle shells to synthesize nano-triple superphosphates (TSPs). The exothermic reaction processes between calcium carbonate (CaCO₃) (from snail and cockle shells) and suitable amounts of orthophosphoric acid (H₃PO₄) (60% w/w) resulted in the sustainable production of triple superphosphates in a quantitative proportion of 1 : 2. Each of the freshly produced substances has been studied using a variety of techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, and Fourier-transform infrared spectroscopy (FT-IR) which confirmed the fact that each of the resulting substances are TSPs which are suitable to be applied as plant nutrients. The crystallite size has been estimated using various models and assumptions (linear straight-line method, Moshi–Scherrer model, Williamson–Hall model, size–strain plot, Halder–Wagner model, and Sahadat–Scherrer model), where the Halder–Wagner model yielded the most appropriate results (D = 32.25 nm, 58.82 nm, 21.73 nm). EDX analysis confirmed the formation of pure TSPs with higher weight percentages of calcium (19.22–24.52%) and phosphorus (27.16–28.13%) and the Rietveld refinement technique verified that the synthesized TSP materials are nearly 100% pure. The microscopic particles progressed to produce spherical and plate-shaped structures, according to SEM examination. The beneficial studies suggest that using marine snail or cockle shells as an initial resource for TSP manufacture in fertilizer manufacturing industries may substitute the usage of non-sustainable phosphate and calcium resources.