Pressed non-fired bricks from phosphogypsum waste for non-load bearing wall

In several countries of the world, phosphogypsum represents a large quantity of waste that poses serious problems of environmental and groundwater pollution. This study aims at recovering phosphogypsum, in its raw state without treatment, in the manufacture of non-load-bearing non-fired bricks. The study starts with the analysis of the radionuclide activity of the materials constituting the bricks, in particular phosphogypsum, in order to avoid any human health problems after the manufacture and use of the bricks. Then, several compositions are tested with several preservation methods in order to optimize the composition. The physical, chemical and mechanical resistance is determined. The results show the possibility to produce non-load-bearing bricks based on untreated phosphogypsum which comply with the standards requirements, using low energy. Indeed, among the considered mixtures, two compositions (60% of PG and of 75% of PG) perfectly verify the physical and mechanical tests. Also, storage of the mixtures for two days in the laboratory and then three days in an oven at 70°C, allows to obtain the best resistance to compression. Thus, the obtained resistance is much higher than the minimum value required for non-load-bearing bricks.

Characterisation of Purified Gypsum and Insoluble Impurities Obtained from Phosphogypsum Waste

In this study, the chemical and phase composition of two samples of phosphogypsum from the waste dumps of the Industry of ChemicalProducts “Elixir – Prahovo” (Serbia) were examined, as well as the possibility of recrystallization of gypsum from an aqueoussuspension of phosphogypsum. The negative effect of higher temperatures on the solubility of calcium sulfate (13.08 mmol/dm3 at95°C vs. 15.43 mmol/dm3 at 40°C) was utilized. In several repeated cycles, calcium sulfate component was progressively dissolvedin water at room temperature and then precipitated at 100°C, using the same liquid phase throughout the experiment. Therefore,phosphogypsum was separated into recrystallized (purified) gypsum, insoluble residue and supernatant, and the mass balance forthe experiment was calculated. Elemental, XRD and SEM-EDS analyses were performed on raw phosphogypsum, purified gypsumand insoluble residue. The whiteness of raw phosphogypsum and purified gypsum were determined and compared. The main objectiveof the study was to investigate the nature of insoluble impurities, in order to define and optimize the methods for their removalduring a potential industrial processing of phosphogypsum.

(Polyphenyl Sulfone - Polyether Sulfone) Blending to Performance Flat Sheet Membrane to Remove Some Heavy and Radioactive Elements from Phosphogypsum Waste

In this research, the traditional version of the phase inversion method was used to fabricate a flat sheet of a blended membrane. The method was involved using a polymer that blends polyether sulfone (PES) varied proportions (0,3,4 and 5 wt.%), and polyphenyl sulfone (PPSU) was 20wt%. It was found that with the addition of PES, the membrane properties increased, the best properties were with 4%wt. The ratio was chosen PES 4wt% to study the effect of time, temperature, and pressure on the rejection of heavy and radioactive elements. The increase in the porosity was with the addition of 4% PES. The rejection of heavy and radioactive elements for thUF membrane increases with increasing of the operating pressure and time. While by increasing the temperature, the rejection of heavy and radioactive elements for thUF membrane decreased. The rejection of K, Th, and Pb are higher than other elements, the order of the rejection is K˃Th˃Pb˃U˃Cd˃Zn˃Cu>Ni.