One of the priority goals of sustainable socio-economic development for the period up to 2030 is providing food for the planet’s population. This entails an increase in the output of mineral fertilizers and, consequently, an increase in the quantities of solid industrial waste. Phosphogypsum, a by-product of phosphate fertilizer production from apatite ore, is one example of such waste. The problem of solid industrial waste recycling is urgent. The present study examines the process of converting calcium sulfate, in the form of a reagent, and phosphogypsum into a composite material of calcium sulfate/sulfide. An environmentally friendly material, sucrose, is used as a reducing agent. Reduced phosphogypsum (as well as calcium sulfate) luminescence is suggested to be associated with the formation of a CaS/CaSO₄ composite material. The synthesized materials are characterized by X-ray phase analysis, X-ray photoelectron spectroscopy, elemental analysis, and calcium sulfide qualitative and quantitative content in the samples. It is shown that in the reduction process at the phase contact point, crystal grids are formed with a significant number of defects, which contributes to the convergence of some of the energy levels of the calcium cation and sulfide anion, facilitating the transitions of electrons from the valence zone to the core zone and the formation of luminescence centers (cross-luminescence). Both samples of reduced phosphogypsum and alkaline earth metal sulfates are found to exhibit luminescence properties under ultraviolet radiation. The data obtained open up broad prospects for the use of solid industrial waste for the synthesis of new materials.

The paper presents a comprehensive study of the processing possibilities for phosphogypsum, a large-tonnage chemical industry waste, into highly sought-after products, such as ultraviolet pigments, and alkalizing reagents for the preparation of organomineral fertilizers. The materials obtained were characterized by X-ray diffraction (XRD), transmission electron microscopy, and thermogravimetric analysis (TGA). It was found that the phosphogypsum thermal treatment process in the presence of a reducing agent (charcoal, sunflower husk) allowed us to obtain new products with a high added value. For the first time, the possibility of obtaining various products by varying process conditions was established. The process of thermal reduction of phosphogypsum in the presence of charcoal at temperatures of 800–900 °C and an isothermal holding time of 60 min resulted in us obtaining samples capable of glowing when irradiated with ultraviolet light. This effect is due to the formation of a composite material based on calcium sulfide and calcium sulfate in the system. The process of the regenerative heat treatment of phosphogypsum at temperatures of 1000–1200 °C resulted in us obtaining a composite material consisting of calcium oxide and sulfate, which can be used for fractionating liquid waste from livestock farming and to obtain organomineral fertilizer. The technological methods developed allow the usage of chemical industrial waste and agricultural waste in secondary processing to produce highly innovative products that will contribute to the achievement of the sustainable development goals, in particular, “Ensuring rational consumption and production patterns”.

This paper explores the feasibility of producing manganese- and lead-doped luminescent materials from phosphogypsum. For the first time, orange- and red-emitting ultraviolet pigments were obtained using a sulfide matrix reduced from phosphogypsum. The resulting materials were characterized using X-ray diffraction (XRD), transmission electron microscopy, Fourier transform infrared spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy (XPS). Doping with manganese or lead cations is shown to produce luminophores whose luminescence shifts from orange to red–orange under UV radiation as lead cations replace manganese cations in the CaS:Mn_1-xPb_x solid solution. A sharp increase in red luminescence intensity was observed for CaS: Mn luminophores when they were irradiated with short-wavelength ultraviolet radiation. These results open up broad possibilities for using phosphogypsum, a high production volume (HPV) chemical waste product, to produce highly innovative products.

This paper studies the formation process of a composite material based on an organic substance, biochar from sunflower husks, and an inorganic substance, nickel (II)-copper (II) ferrites of the composition Cu_xNi_1−xFe₂O₄ (x = 0.0; 0.5; 1.0). The obtained materials were characterized by X-ray phase analysis, scanning electron microscopy, and FTIR spectroscopy. It is shown that when replacing copper (II) cations with nickel (II) cations, the average parameters and volume of the unit cell gradually decrease, and the cation–anion distances in both the tetrahedral and octahedral spinel grids also decrease with regularity. The oxide materials were found to form a film on the surface of biochar, repeating its porous structure. The obtained materials exhibit high catalytic activity in the methyl orange decomposition reaction under the action of hydrogen peroxide in an acidic medium; the degradation of methyl orange in an aqueous solution occurs 30 min after the start of the reaction. This result may be associated with the formation of the Fenton system during the oxidation–reduction process. A significant increase in the reaction rate in the system containing mixed nickel–copper ferrite as a catalyst may be associated with the formation of a more defective structure due to the Jahn–Teller effect manifestation, which creates additional active centers on the catalyst surface.

In this work, we introduce the novel possibility of producing blue fluorescent ultraviolet pigments from phosphogypsum. The obtained materials are characterized by X-ray diffraction (XRD), transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS). The formation of the CaS phase in the sample during the reduction of calcium sulfate was established. Thermal treatment of phosphogypsum in the presence of a reducing agent (potato starch) under environmental isolation conditions is found to yield high-quality products with high added value. The highest luminosity is established in samples containing 0.6 mol. %, which were heat-treated under a temperature of 1100 °C for 60 min. The synthesized CaS:Cu materials are shown to emit light in the blue region of the spectrum, with an emission maximum at a wavelength of 480–490 nm. The developed technological methods open the possibility to recycle chemical industry waste, which contributes to the achievement of sustainable development goals, in particular, the goal of ensuring rational consumption and production patterns.