Abstract
Phosphate tailings (PTs) are solid waste, which is produced by phosphate flotation. In this work, PTs were used as raw materials for the preparation of diethylenetriamine pentamethronic acid (DTPMP) intercalated trimetal (Ca-Mg-Al) layered double hydroxides (TM-DTPMP LDHs) by co-precipitation method. TM-DTPMP LDHs were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, differential thermal gravimetric analysis, X-ray photoelectron spectroscopy and applied as a flame retardant to improve the fire safety of epoxy resin (EP). The results showed that the composite materials exhibited obvious layered structure. After intercalation, layer spacing increased from 0.783 to 1.78 Å. When the amount of TM-DTPMP LDH in EP was 8%, the limitted oxygen index of the composite material increased from the original 19.2% to 30.2%. In addition, Cone calorimeter (CC) and Raman spectrum results indicated that with the addition of TM-DTPMP LDHs, the value of heat release rate peak (pHRR) and total heat release (THR) were reduced by more than 43% and 60%, while the value of smoke formation rate (pSPR) and the total smoke production (TSP) decreased nearly 64% and 83%, respectively. The significant reduction in the release of combustion heat and harmful smoke during EP combustion may be attributed to the synergistic flame-retardant effect between hydrotalcite and DTPMP. This work exhibited great potential for the green recycling of PTs and the enhancement of the fire safety of EP.
Highlights
As a typical and extensive phosphorus chemical solid waste, phosphorus tailings (PTs) are one of the main by-products produced in the process of phosphate mining and flotation
The diffraction peaks of (003), (006) and (009) crystal planes can be seen at 11.3◦, 22.97◦ and 34.83◦, which conformed to the diffraction peak angles of TM Layered double hydroxides (LDHs) X-ray diffraction (XRD) crystal planes [24,25]
The diffraction peaks of (003), (006) and (009) crystal planes can be seen at 11.3°, 22.97° and 34.83°, which conformed to the diffraction peak angles of trimetal layered double hydroxides (TM LDHs) XRD crystal planes [24,25]
Summary
As a typical and extensive phosphorus chemical solid waste, phosphorus tailings (PTs) are one of the main by-products produced in the process of phosphate mining and flotation. PTs are mainly composed of calcium and magnesium carbonates, and the main components are CaO, MgO and P2O5 [1,2]. 0.4 tons of PTs are produced for every ton of phosphate concentrate produced [3]. In China, nearly 9.5 million tons of phosphate tailings will be produced every year, but the comprehensive utilization rate of PTs is only about 7% [4]. A large amount of PTs can only be piled up in the tailings pond for a long time. After being washed by rainwater, this will lead to the chemical migration of harmful elements. The effective comprehensive utilization of PTs is imminent
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