Preparation of ultramarine green pigments by recycling of the discarded molecular sieves for green vegetation spectral simulation

Molecular sieves were widely used in the chemical industry, which caused a large number of inactivated molecular sieves to be discarded, resulting in a serious waste of resources and environmental pollution. Recently, recycling of discarded molecular sieves (DMS) has become a research hotspot. This study proposes an economical method using DMS to prepare green pigments mimicking foliage spectrum. The synthesized products were subjected to characterization using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Ultraviolet-visible-diffuse reflectance spectroscopy (UV-Vis-DRS), and scanning electron microscopy (SEM). The analysis revealed that sulfur radicals can be effectively incorporated as chromophores within the β-cages that are formed during the recrystallization process of sodalite, these cages are highly conducive to accommodating the radicals, thereby providing a protective environment that shields them from external influences. By adjusting the mass ratio of Na₂CO₃/S, the visible reflectance spectrum of ultramarine pigments can be easily modified. In addition, camouflage coating based on ultramarine green can be used to simulate the spectral reflectance characteristics of green vegetation. The Spectral Angle Mapping (SAM) system was used to evaluate the simulation effect of the camouflage coating. At a threshold below 98.5%, the camouflage coating still be misidentified as leaves, this method can recycle massive solid waste resources and significantly reduce the preparation cost of imitation green vegetation camouflage pigments.