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In China, large amounts of industrial byproduct gypsum (IBG) end up as waste and excessive stockpiling due to its low whiteness and high impurity content. In this study, two typical IBG including phosphogypsum (PG) and flue gas desulfurization gypsum (FGDG) were the research object. The impurities removal and the whiteness improvement by the tandem pyro-hydro process were investigated. Species of impurities, mechanism of whiteness improvement and the evolution of the gypsum phase during the tandem process were revealed. The results indicate that the impurities responsible for the poor whiteness of IBG included organic matter, carbon particles, and silicates. The temperature of the pyro process is the critical factor. The IBG is calcinated at 400–500 °C to fully remove organic matter and carbon particles, while decompose silicates to silica. Following, in the hydro step, the calcined IBG was treated with dilute sulfuric acid (0.2–1.0 M) to remove ion impurities such as Fe(III), the higher temperature and higher acidity are favorable to the production of valuable CaSO4. After treatment, the whiteness of IBG was improved from below 40% to above 80%, and the soluble impurity content can meet the standards. Moreover, both PG and FGDG products exhibited a compressive strength exceeding 10.0 MPa of curing for 7 d. This work provides theoretical guidance to promote the resource utilization of IBG, especially as plastering materials after purification and whitening. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South-Central Minzu University (Natural Science Edition) is the property of Journal of South-Central Minzu University (Natural Science Edition) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wastewater containing phosphorus is often added by industrial activities, which is bad for the environment. In this study, composite biochar (PG-RS700) was prepared from phosphogypsum (PG) and rape straw (RS) for the treatment of phosphate in wastewater. SEM, FTIR, XRD and XPS characterization results showed that PG and RS were successfully combined. When PG-RS700 was dosed at 1.5 g/L and the phosphate solution concentration was 50 mg/L and pH = 8, the phosphate removal rate was 100% and the adsorption capacity was three times higher than the corresponding pure PG and RS. The quasi-secondary kinetic model indicated that the adsorption mechanism was chemisorption, and the maximum adsorption capacity for phosphate in the Langmuir isotherm model was 102.25 mg/g. Through pot experiment, the phosphorus adsorbed material obviously promoted the growth of plants. PG-RS700 can be used as a powerful adsorbent to treat phosphate in water and return it to soil as phosphate fertilizer. [ABSTRACT FROM AUTHOR]

Owing to its uncomplicated synthetic methodology and exorbitant market demand, malachite green is widely used in numerous industries, particularly as a fungicide in aquaculture. Considering its intrinsic toxicity and potential long-term health impacts, deployable and cost-effective strategies must be developed for eliminating water-soluble malachite green. In this study, chemically activated phosphogypsum, a byproduct of fertilizer production, was used to remove malachite green from an aqueous system. Due to its low cost and abundance, the use of phosphogypsum as a sorbent material may significantly reduce the cost of adsorption-based processes. Moreover, its structural durability allows efficient recycling without significant deformation during reactivation. However, untreated phosphogypsum exhibits minimal efficiency in adsorbing synthetic dyes due to its unfavorable surface chemistry. Our investigation revealed that Zn activation induced a noticeable increase in pore volume from 0.03 to 0.06 cm3·g−1. A 60 mg·L−1 sorbent dose, pH 7, 150 r·min−1, and operational temperature of 30 °C produced 99% quantitative sorption efficiency. Response surface methodology and artificial neural network were used to optimize process parameters by validating experimental values. No detectable toxicity was observed in Escherichia coli when exposed to the treated water. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are considered vital raw materials for the economy and are on the European Union's list of critical raw materials (CRMs). Europe is mainly dependent on REE imports. This dependence could be reduced if locally available primary or secondary resources would be processed. In Poland, there are, for instance, over 5 million metric tons of phosphogypsum (PG), a fine powdery byproduct from the fertilizer industry, available near the former Wizów Chemical Plant near Bolesławiec. This material that is considered a waste in Poland contains significant amounts of REEs that could theoretically be recovered and contribute to Europe's economy. This work is the first systematic analysis of REE leaching studies with sulfuric acid and PG from Wizów. Process parameters such as temperature, particle size, concentration of the leaching solution, and the addition of oxidant and reductant agents were tested to determine the most efficient process. Ultimately, a leaching efficiency of 99% was obtained. Lanthanum exhibited the highest leaching efficiency at almost 100%, followed by Yttrium, Neodymium, Terbium, and Dysprosium. The results of the laboratory experiments are promising and suggest that larger pilot or commercial experiments can be performed next. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The improvement of saline-alkali land plays a key role in ensuring food security and promoting agricultural development. Saline soils modifies the response of the soil microbial community, but research is still limited. The effects of applying phosphogypsum with rice cultivation (PRC) on soil physicochemical properties and bacterial community in soda saline-alkali paddy fields in Songnen Plain, China were studied. The results showed that the PRC significantly improved the physicochemical properties of soil, significantly reduced the salinity, increased the utilization efficiency of carbon, nitrogen, and phosphorus, and significantly increased the activities of urease and phosphatase. The activities of urease and phosphatase were significantly correlated with the contents of total organic carbon and total carbon. A redundancy analysis showed that pH, AP, ESP, HCO3−, and Na+ were dominant factors in determining the bacterial community structure. The results showed that PRC could improve soil quality and enhance the ecosystem functionality of soda saline-alkali paddy fields by increasing nutrient content, stimulating soil enzyme activity, and regulating bacterial community improvement. After many years of PRC, the soda-alkali soil paddy field still develops continuously and healthily, which will provide a new idea for sustainable land use management and agricultural development. [ABSTRACT FROM AUTHOR]

In this paper, the dihydrate–hemihydrate recrystallization method was employed to produce β-hemihydrate gypsum. The effects of thermodynamic conditions such as temperature, sulfuric acid concentration, and phosphoric acid concentration on the removal of F and P impurities were investigated. Kinetic studies revealed that the throughflow impeller, when compared to the conventional impeller, demonstrates a higher removal rate for soluble phosphorus, while having little impact on soluble fluorine. This study contributes to the utilization of PG resources. [ABSTRACT FROM AUTHOR]

This work is an attempt to understand and optimize the rare earth elements leaching from Moroccan phosphogypsum using a nitric acid solution. The Plackett–Burman statistical design was used to identify the statistically significant factors responsible for the optimum leaching conditions. With this purpose, the following seven variables were studied: nitric acid concentration (X1), solid‐to‐liquid ratio (X2), temperature (X3), leaching time (X4), stirring speed (X5), drying (X6), and particle size (X7). Given that the leaching recovery of rare earth elements is limited by the quantity of dissolved phosphogypsum, we examined two simultaneous responses, namely, the leaching efficiency of rare earth elements YREEs and the leaching efficiency of calcium YCa (dissolution rate of phosphogypsum). The predicted values of the two fitted models were in good agreement with the experimental values by a coefficient of determination (R2) equal to 98.6% and 96.50%, respectively. In the model of YREEs, only the effect of drying was found to be statistically insignificant with a p‐value greater than 0.05. Nitric acid concentration, solid‐to‐liquid ratio, and temperature are the only variables having a statistically significant effect in the model of YCa. At a dissolution rate of phosphogypsum equal to 30.13%, the leaching efficiency of rare earth elements from our sample has reached a maximum of 87.55%. The optimal experimental conditions are a nitric acid concentration of 3.3 M, a solid‐to‐liquid ratio of 1/9, a temperature of 75°C, a leaching time of 20 min, a stirring speed of 200 rpm, and d ≤ 100 µm as a particle size. [ABSTRACT FROM AUTHOR]

In the present experiment, two types of water-reducing agents, naphthalene (FDN) and polycarboxylic acid (PCE), were selected, and their effects on the mechanical properties of foamed phosphogypsum were evaluated. It was shown that when the water-reducing agent contents were increased, the strength of the foamed phosphogypsum first increased and then gradually decreased, and that the dry density of the foamed phosphogypsum first decreased and then gradually increased. The FDN samples had better mechanical properties and a lower dry density than the PCE samples. The effect of the water-reducing agent dose on the apparent viscosity and shear stress of the phosphogypsum slurries was in the order of 0% > 0.4% > 0.3% > 0.5% > 0.2% > 0.1%. The apparent viscosity and shear stress of the gypsum slurry mixed with 0.4% FDN or PCE were the highest. FDN and PCE both enlarged the pore size distribution range, increased the size and proportion of large pores, and decreased the total pore content of foamed phosphogypsum; however, the effect of PCE was more significant. The foamed phosphogypsum slurry mixed with 0.4% FDN had the highest total pore content. Among the samples, the total pore content of foamed phosphogypsum A was able to reach 91% and the total pore content of foamed phosphogypsum B reached 77%; the lowest proportion of large pores for foamed phosphogypsum A and B separately reached 17% and 7%, respectively. The water-reducing agents mainly reduced the water consumption of the phosphogypsum slurries; improved the viscosity and shear stress of the slurries; affected the stability of the foam in the gypsum slurries; influenced the pore size and distribution in the foamed phosphogypsum samples; and caused a difference in the strength and dry density of the foamed phosphogypsum samples. The viscosity of the gypsum slurry doped with 0.4% FDN better matched that of the foam; therefore, it had the highest macro-strength and the lowest dry density. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resin, mrthyl ethyl ketone peroxide curing agent, and cobalt isooctannate accelerator (accelerator) were selected to stabilise and cure phosphogpsum. Tho c fleets of different do sages of UPR and curing agent on the compressive strength of the solidified bodies at various ages were investigated; thc strength formation mrrhanism and microscopic morphologj* of the phosphogypsum csolidi* fied bodies were analcd by SEM ami FriK;and the leaching toxicity analysis of the phosphogjpsum so・ lidified body was carried out by K2P-MS・ The study shows that:the compressive strength of phosphogj psum solidificci bodies at all ages increases with the increase of UIK doping;uith the increase of curing agent doping, the compressive strength of phosphogypsum solidified bodies shows a trndcncy of increasing firstly and then decreasing later; the compressive strength of phosphogjpsum solidified bodies grou faster in the early stage and slower in the later stage・ The optimal ratio of phosphogypsum solklificd body is 100%, phosphogjpsum, 4()% UPK doping, 0. 8% curing agent doping, 0.4% accelerator doping, ami its 3, 7,28 d compressive strength arc 30. 8,36. 3, 37. 2 respectively. UPR fills up the pore space of phosphogjpsum, tightly waps around the phosphogypsum and binds with each other, and it solidifies rapidly through the copolymrrization reaction triggered by the airing agent ami the activator, and generates the phosphogypsum solidified bodies. Through the copolymrrisation reaction triggered by the curing agrnt ami acc<*lcrator, it solidified rapidly, and the generated polymer thrcc-

In order to study the strength characteristics of red clay stabilized by a high dosage of phosphogypsum, a mix proportion design was carried out at the ratio of phosphogypsum:red clay = 1:0.5, 1:1, 1:2, 1:3, 1:4, and 1:5 using 4%, 6%, and 8% cement as a curing agent, and this study was carried out through the unconfined compressive strength test, water stability test, California bearing ratio (CBR) test, and durability test. As the phosphogypsum content increases, the unconfined compressive strength of the mix shows a trend of increasing and then decreasing, the unconfined compressive strength of the mixture is the largest when the ratio is 1:3, and with the increase in the number of dry and wet cycles, the unconfined compressive strength of the mixture decreases, and the decay is the largest at 2–3 dry and wet cycles. The higher the phosphogypsum content, the better the water stability performance of the mix. In addition, the CBR value of the mixture can meet the requirements of freeway, primary highway, secondary highway bed, and embankment filler bearing ratio. In this paper, a mix durability test method is proposed to express the mix durability performance in terms of mass loss rate and durability coefficient; the mass loss rate of the mix increases with the increase in the number of wet and dry cycles, and the durability coefficient decreases with the increase in the number of wet and dry cycles; the higher the content of phosphogypsum, the better the durability performance of the mix. [ABSTRACT FROM AUTHOR]

Ceramsite was made from sludge, phosphogypsum, and red mud and then modified with different concentrations of hydrochloric, nitric, or citric acid. The resulting composite ceramsite was subsequently utilized for the adsorption of Pb(II). The maximum adsorption capacities of hydrochloric acid– and nitric acid–modified ceramsites were 90.38 and 88.57 mg/g, respectively, which were much higher than those of unmodified ceramsite (66.86 mg/g) and citric acid–modified ceramsite (57.85 mg/g). The variation of isoelectric point, acidic and basic groups, and Fourier transform infrared spectra of ceramsite were compared before and after adsorption. A decrease of isoelectric point implied weakening of electrostatic repulsion between Pb(II) and the modified ceramsite. Functional groups, such as O─H, C═O (or C═C), and Si─O─Si (or Al─O─Al), were involved in the adsorption. In addition, phenol hydroxyl, which exhibited a significant increase in modified ceramsite and a noticeable decrease after adsorption, was the most important group. Besides, the modified ceramsite had larger specific surface areas and pores (30.66 g/m2,.11256 cm3/g), more functional groups, and lower isoelectric points (8.57), which were favorable for adsorption. The adsorption processes described by pseudo‐second‐order kinetics were controlled by chemical adsorptions. Isothermal studies indicated that monolayer adsorption occurred on hydrochloric acid–modified ceramsite and multiple processes occurred on nitric acid– and citric acid–modified ceramsites. Thermodynamic analysis confirmed Pb(II) adsorption on modified ceramsite was spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

The study of the adhesion properties between asphalt and aggregate plays a critical role in deciphering the fracture behavior and damage characteristics in asphalt mixtures. This research is dedicated to exploring the impact of various aging behaviors on adhesion properties and the reinforcing effects of modifiers. In this context, a novel composite modifier (MPM), was synthesized from phosphogypsum whisker, derived from phosphogypsum waste. Asphalt specimens, encompassing both virgin and modified asphalt with the different dosages of MPM, were prepared under a spectrum of eight aging conditions. The mechanical properties of these specimens were meticulously analyzed using multiscale tests to assess the adhesion properties under diverse aging conditions and modifier dosages. Furthermore, the study delved into the microscopic effects of aging and modification on adhesion properties. The results highlighted that aging detrimentally impacts the adhesion properties of asphalt, with this negative effect progressively intensifying over time. In contrast, the enhancement of adhesion properties by MPM exhibited variation in accordance with its dosage. Limestone, characterized by a rougher external interface and a higher prevalence of high-valent cations, demonstrated more pronounced adhesion properties to asphalt compared to granite. The aging process introduced new diffraction patterns and characteristic peaks in the asphalt, with their intensities showing a direct correlation with the duration of aging. The MPM modification was found to effectively mitigate the deterioration in the structural stability of the virgin asphalt. Overall, this study offers comprehensive insights into the aging and modification mechanisms affecting adhesion properties between asphalt and aggregate, contributing significantly to the resource utilization of solid waste. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG) is a solid waste generated by phosphate fertilizer industries that is currently used in concrete materials. However, adding PG to concrete usually results in reducing its water resistance and corrosion resistance. This paper presents a new method of applying PG to concrete to improve its water resistance. In this paper, a green superhydrophobic PG (SPG) coating was prepared using modified PG as a hydrophobic medium and cement as the bonding material. The contact angle between the superhydrophobic phosphogypsum coating (SPG coating) and water was 156°, and the coating reached a superhydrophobic state with good self-cleaning ability. Even when sandpaper was used to polish the coating, the water contact angle of the coating was still greater than 150°, indicating that the coating had good wear resistance. In addition, the results of water absorption and electrochemical experiments indicated that mortar coated with SPG had better water resistance and corrosion resistance than ordinary mortar. The SPG coatings with water resistance, wear resistance, and self-cleaning properties have potential applications in building exterior walls. [ABSTRACT FROM AUTHOR]

The accumulation of phosphogypsum (PG) has become a significant environmental and economic challenge, making PG reuse an urgent concern. This study aims to explore the potential of combining PG with steel slag (SS), ground granulated blast-furnace slag (GGBS), and cement clinker (CC) to create excessive-sulfate phosphogypsum slag cement (EPSC) for use in self-compacting concrete (SCC). However, residual acid and other impurities in PG can significantly slow down the setting time of EPSC. To optimize the setting time, different methods including wet grinding, washing, and the addition of pure gypsum, limestone powder (LP), and aluminum cement (AC) are used. Results show that the wet grinding method and washing method remove soluble phosphorus impurities and reduce fluorine ion levels by 64%. However, nonsoluble impurities that cannot be removed by wet grinding and washing continue to affect EPSC's setting time. Furthermore, the addition of LP shortens the setting time, but not enough. Using a 3% dosage of AC successfully reduces the setting time to a satisfactory level and EPSC SCC with a 28-day strength greater than 40 MPa is produced using the paste rheological threshold method. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG) is an industrial solid waste generated during the preparation of phosphoric acid, which is produced in large quantities and stockpiled or discharged into the sea. This study aims to design sustainable pavement base materials constituting significant PG content. The physical and chemical properties of the raw materials were first tested. The optimum moisture content and maximum dry density of specimens were determined by compaction tests. The unconfined compressive strength (UCS), split tensile strength (STS), freeze-thaw cycles, and shrinkage tests were used to evaluate the mechanical performance of phosphogypsum pavement base material (PPBM). Furthermore, the interaction mechanism was investigated by applying scanning electron microscope (SEM) and Fourier-transformed infrared (FTIR) tests. The results showed that the 7-day UCS of PPBM with cement content 8%–12% was greater than 3 MPa. The specimens retained 91.3% unconfined compressive strength over five freeze-thaw cycles. Unlike traditional semirigid base materials, the PPBM exhibited no shrinkage strain, which is manifested by the growth of expansion strain with increasing amounts of PG. Through microscopic observation, the PPBM produced ettringite (AFt) and calcium-silicate-hydrate (CSH) with the extension of curing time, which is consistent with the analysis of FTIR spectrums. The crystallized water in the PG participates in the hydration reaction. [ABSTRACT FROM AUTHOR]

In this article, a kind of original bamboo-fiber reinforced phosphogypsum composite wall was proposed. The axial compression tests of eight walls and finite element analysis were carried out. The failure modes and mechanical properties of the walls were explored, the influence of parameters on the axial compression performance of the walls was studied, and the calculation methods of the axial compression capacity and stiffness of the composite walls were proposed. The results show that the phosphogypsum cracked first in the composite walls during the loading process, the cracks gradually spreaded through and widened, and the bamboo tubes inside the composite walls were crushed. The buckling failure occurred in the pure original bamboo wall. The bearing capacity of the composite wall control specimen is 140% and 38.46% higher than that of the pure phosphogypsum wall and the pure original bamboo wall, respectively. The number of dovetail nails has no significant effect on the axial compression performance of the composite wall. The bearing capacity and stiffness of composite wall increase with the increase of bamboo number, wall thickness, bamboo wall thickness and phosphogypsum strength. The calculation method of axial bearing capacity and stiffness of composite wall based on bamboo content is proposed. The finite element simulation results are in good agreement with the experimental and theoretical calculation results. The theoretical calculation method has high accuracy. The composite wall realizes the complementary advantages of original bamboo and phosphogypsum, which provides reference for the development and application of green buildings. [ABSTRACT FROM AUTHOR]

The selective flotation separation of gypsum and quartz in phosphogypsum (PG) is an urgent problem that is very important for the high‐value utilization of PG. In the work, dodecyl amine hydrochloride (DH) was introduced as a collector for the selective flotation separation of gypsum and quartz. The flotation property and selective mechanism of DH on the surface of gypsum and quartz were researched by single mineral flotation experiments, Fourier transform attenuated total reflection infrared spectroscopy analyzer, zeta potential analyzer, X‐ray photoelectron spectrum, molecular dynamic (MD) simulation, etc. Additionally, H+ was introduced into the mineral‐water system simulated by MD to take into account the effect of acidic conditions on the adsorption of DH. The pre‐adsorption of H+ on the quartz surface under strongly acidic conditions hindered the electrostatic force adsorption of DH on the quartz surface. Furthermore, DH was adopted as a collector in the direct flotation recovery of gypsum from PG, and the gypsum concentrates with productivity of 69.85%, CaSO4·2H2O content of 96.33%, and whiteness of 55.00% were obtained. The SiO2 content in the gypsum concentrate decreased from 9.08% to 0.616%. It suggested that DH could serve as a promising collector in the selective separation of gypsum and quartz in PG via flotation. [ABSTRACT FROM AUTHOR]

The chronic accumulation of phosphogypsum (PG) has resulted in significant environmental contamination issues within the wet-process phosphoric acid (WPPA) industry. An innovative technical route for transforming PG into a resource has been achieved through the introduction of floc flotation and acid cleaning in WPPA. The floc flotation using cationic polyacrylamide as a flocculant and micro lotion, which is composed of dioctyl phthalate, polyoxyethylene(10)nonylphenyl ether, kerosene, and n-octanol as a collector, has been performed. The effect of floc flotation on product quality and the underlying mechanisms were investigated by XRF, FT-IR, SEM, and 2-dimensional fractal dimension analysis. The optimal parameters were determined through a factor experiment, which yielded the following results: floc flotation temperature 65 °C, cationic polyacrylamide 180 g/Mg, collector 1.08 kg/Mg, and flushing sulfuric acid concentration 20%. The resulting PG exhibited a high grade of 95.01%, whiteness of 70.8%, and gypsum recovery of 93.52%. Furthermore, the soluble phosphorus and soluble fluorine levels are below 0.1%. In the flotation process, the combination of polyacrylamide and collector effectively separated fine organic matter and siliceous material with a hydrophobic bubble, facilitating their upward movement and subsequent separation from PG. The new WPPA, which exhibits enhanced product quality and reduced production costs, can be utilized extensively within the WPPA. [ABSTRACT FROM AUTHOR]

Applying organic waste and inorganic additives during composting can be an effective and easy-to-control strategy for optimizing humification, maturation, and the availability of essential mineral elements in compost. In this respect, this study aims to evaluate the effect of organic (olive-mill waste and horse manure) and inorganic (phosphogypsum) additives on the evolution of maturity indices, aromatic compounds, and nutrient availability during composting. Four mixtures [horse manure + green waste (M1), olive-mill + green waste (M2), sewage-sludge + phos-phogypsum + green waste (M3), and green waste (M4)] were carried out. Physicochemical (temperature, pH, phosphorus, nitrogen, and carbon-to-nitrogen (C/N) ratio), infrared-spectroscopic, and phytotoxicity were monitored. The results showed that (in)organic additives have a positive effect on maturity and humification indices, pH stability, and the phosphorus and nitrogen availability in the composts produced. The horse manure additive reduced the carbon and increased the nitrogen, reducing the C/N ratio. Phosphogypsum and olive-mill reduced phytotoxicity, boosting the nitrogen and phosphorus availability of in composts. Fourier transform infrared spectroscopy (FT-IR) analysis revealed that phosphogypsum and olive-mill addition improved the aromatic compounds and reduced the aliphatic ones in M3 and M4 com-posts. These results suggest new approaches to promoting maturity and stability, as well as phosphorus and nitrogen availability in composts, through better use of organic waste and inorganic additives in composting. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The preparation of artificial soil is a potential cooperative resource utilization scheme for red mud and phosphogypsum on a large scale, with a low cost and simple operation. The characteristics of the bacterial community structure and function in three artificial soils were systematically studied for the first time. Relatively rich bacterial communities were formed in the artificial soils, with relatively high abundances of bacterial phyla (e.g., Cyanobacteria, Proteobacteria, Actinobacteriota, and Chloroflexi) and bacterial genera (e.g., Microcoleus_PCC-7113, Rheinheimera, and Egicoccus), which can play key roles in various nutrient transformations, resistance to saline–alkali stress and pollutant toxicity, the enhancement of various soil enzyme activities, and the ecosystem construction of artificial soil. There were diverse bacterial functions (e.g., photoautotrophy, chemoheterotrophy, aromatic compound degradation, fermentation, nitrate reduction, cellulolysis, nitrogen fixation, etc.), indicating the possibility of various bacteria-dominated biochemical reactions in the artificial soil, which can significantly enrich the nutrient cycling and energy flow and enhance the fertility of the artificial soil and the activity of the soil life. The bacterial communities in the different artificial soils were generally correlated with major physicochemical factors (e.g., pH, OM, TN, AN, and AP), as well as enzyme activity factors (e.g., S-UE, S-SC, S-AKP, S-CAT, and S-AP), which comprehensively illustrates the complexity of the interaction between bacterial communities and environmental factors in artificial soils, and which may affect the succession direction of bacterial communities, the quality of the artificial soil environment, and the speed and direction of the development and maturity of the artificial soil. This study provides an important scientific basis for the synergistic soilization of two typical industrial solid wastes, red mud and phosphogypsum, specifically for the microbial mechanism, for the further evolution and development of artificial soil prepared using red mud and phosphogypsum. [ABSTRACT FROM AUTHOR]

Calcium molybdate (CaMoO4) is of significant interest due to its unique properties and numerous industrial applications, such as catalysis, electrochemistry, and optoelectronics. In this study, we developed an economical and environmentally friendly method to synthesize calcium molybdate from Moroccan phosphogypsum (PG) industrial waste and sodium molybdate, all at room temperature. Comprehensive analysis through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman vibrational spectroscopy, and scanning electron microscopy (SEM) revealed the high purity of the synthesized calcium molybdate, with particle sizes of only 12 nm. Additionally, optical characteristics were studied using ultraviolet-visible spectroscopy (UV-vis), which showed an optical band gap of Egap = 3.96 eV for CaMoO4. These results confirm the successful synthesis of calcium molybdate nanoparticles from Moroccan phosphogypsum, demonstrating an effective pathway to valorize this industrial waste into a valuable material. This approach contributes to environmental sustainability by reducing dependence on rare chemicals while offering innovative solutions for the industry's sustainable development. [ABSTRACT FROM AUTHOR]

Phosphogypsum backfill technology is an important way of backfill mining. However, phosphogypsum has problems such as poor water resistance and low strength. Therefore, in this study, phosphogypsum and carbide slag (CS) were mixed to form the phosphogypsum backfill (PB). The effects of the CS content on the workability, mechanical properties, and microstructure of PB were studied by means of pH value, bleeding rate, fluidity, strength, water resistance, SEM, and XRD. The results showed that the incorporation of CS significantly improved the working performance. The softening coefficient initially climbed and subsequently declined. Peak stress and MOE of PB showed a trend of rise-fall, reaching the peak when CS content was 10%. The damage evolution process of PB was revealed. The process of energy dissipation of PB during uniaxial compression showed a law of increasing and then decreasing with increasing CS dosage. The test group composed of 90% phosphogypsum and 10% CS was the best experimental scheme. These results were hoped to provide guidance for the comprehensive utilization of phosphogypsum and CS and the theoretical basis for the application of PB in backfill mining. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG, CaSO4·2H2O), impure gypsum with phosphate residues, is a by-product of fertilizer industry. Due to calcium and phosphorus in its structure, PG can be evaluated for synthetic hydroxyapatite (HAp) production. This study provides a two-step reaction sequence for PG-derived synthetic HAp production. Synthesized HAp (s-HAp) particles were calcined at 900 °C for 4 h, followed by characterization studies with respect to commercial bone ash (CBA) sample to be evaluated as its substitute in bone china industry. Ca/P ratio (wt%) of the samples was investigated by microwave-assisted temperature-controlled acid digestion, followed by ICP-OES analysis. Crystallinity of the samples was analyzed by XRD, and morphological structure was investigated by SEM–EDS analyses. ICP–OES analyses revealed that s-HAp and CBA samples have similar Ca/P ratio, 2.0979 for s-HAp and 2.0917 for CBA samples, respectively. Low-intensity β-TCP phases in the XRD patterns of s-HAp samples revealed low crystalline structure. SEM images indicated a uniform distribution with spherical-like morphology in CBA samples, however, a layer-by-layer morphology and amorphous structure was observed in s-HAP samples. Structural and morphological differences indicate that PG-derived s-HAp samples require purification processes and reaction parameters should be further developed to increase yield. However, this study provides a high potential for a novel approach of an industrial scale valorization strategy for PG. Because the supply–demand cycle is price dependent, the availability of phosphorus in agriculture as a raw material has been a major concern for the usage of phosphate rock. Novel methods for substitute supplies of phosphorus in agricultural applications have been suggested. While HAp is a common ceramic material, its application as a substitute for phosphorus fertilizer is still in its infancy. PG has great potential as a raw material for the synthesis of hydroxyapatite and ammonium sulfate. Large-scale PG production in the phosphoric acid industry puts pressure on research to develop alternate methods for using PG aggregate resources in an economical and environmentally responsible way. The use of PG as a calcium and phosphorus precursor in the synthesis of HAp will result in an economical raw material and an effective waste management plan. [ABSTRACT FROM AUTHOR]

Phosphogypsum is a by-product of the wet-process phosphoric acid production, and it is rich in Ca and S. Long-term storage of Phosphogypsum can cause serious pollution to the environment; therefore, promoting the sustainable utilization of Phosphogypsum is crucial. This study proposes the use of Phosphogypsum and silicic acid in a sodium hydroxide solution for the hydrothermal synthesis of porous calcium silicate hydrate adsorbent, which is used for adsorbing Fe2+ from simulated hydrochloric acid pickling wastewater. Under the optimal synthesis conditions (37.5 g/L of NaOH, calcium/silicon ratio of 1.0, liquid/solid ratio of 15:1 mL/g, 110 °C, and 4 h), the conversion rate of SO42− in Phosphogypsum is 87.41%. Porous calcium silicate hydrate exhibits excellent OH− release capability in Fe2+-containing pickling wastewater. The adsorption process for Fe2+; is mainly chemical adsorption, involving ion exchange between Ca2+ and Fe2+, as well as complexation reactions of O-Si-O group, -OH group, and Si-O group with Fe2+. This technology aims to provide a solution for the sustainable utilization of Phosphogypsum and the recovery of Fe2+ from pickling wastewater, which has significant practical importance. [ABSTRACT FROM AUTHOR]

This is an article in the field of ceramics and composites. In order to improve the comprehensive utilization of mineral resources and mining technology, mine filling materials are prepared from mineral solid wastes such as phosphogypsum, cement and tailing sands as aggregates, analytical studies of the slurry's comprehensive search performance, mineral composition and microscopic morphology are carried out, and the molecular structure of hydrides is discussed in conjunction with molecular dynamics simulations. The results showed that the addition of phosphogypsum significantly increased the slump of the modified filler, decreased the bleeding rate, and the compressive strength showed a rising trend. The strength value of the modified filler increased significantly with the curing time. The strength of phosphogypsum modified backfill after curing for 28 d is about 1.2 times that of cement backfill. Calcium silicate hydrate and ettringite in phosphogypsum modified filling materials are the main hydration products. SEM image shows that the microstructure of phosphogypsum modified filling materials is relatively compact and there are few micro-cracks. The numerical simulation results show that the elastic modulus of calcium silicate hydrate is higher than that of ettringite. The key to improving the strength of filling material is to promote the formation of calcium silicate hydrate.

Abstract Bamboo is an ideal green building material with excellent mechanical properties. Phosphogypsum (PG) is a kind of solid waste residue which is in urgent need of resource utilization and has been used as construction material. In this paper, a kind of round bamboo-fiber reinforced phosphogypsum composite short column was proposed. Axial compression tests of pure bamboo columns, bamboo columns filled with phosphogypsum inside, bamboo columns with phosphogypsum outside and bamboo columns with phosphogypsum inside and outside were carried out to explore the failure mode and mechanical properties of the short columns. The effects of the parameters include bamboo node, hose hoops, size of the bamboo tube and the strength of phosphogypsum on the mechanical properties of the short columns were analyzed, and the theoretical calculation method of the bearing capacity of the short columns was put forward. The results show that the bamboo nodes and hose hoops can improve the bearing capacity, initial stiffness and ductility of the column. The larger the size of the bamboo tube, the better the mechanical properties of the short column. The bearing capacity of round bamboo—phosphogypsum composite short column is higher than that of pure bamboo column. The ductility of bamboo columns with phosphogypsum outside is obviously higher than that of pure bamboo columns. The finite element analysis results are in good agreement with the test results. The theoretical calculation method of the bearing capacity of columns considering the strength reduction coefficient, the bamboo node effect coefficient and the constraint effect in this paper has high accuracy.

Phosphate rocks, as well as their derivatives and by-products, are complex minerals that make elemental analysis very complicated. Iodine is commonly found in these matrices, and its concentration must be controlled. The present work describes the development of a novel rapid digestion protocol based on ultrasonic-assisted acid digestion for the determination of iodine in phosphate rock and phosphogybsum samples by Iodometric titration. The developed method occurs at low digestion temperature and uses a dilute nitric acid 5% (v/v) solution instead of concentrated acid. The investigated parameters influencing UAD, were completely optimised using experiments design methodology (DOE). Iodine recoveries from dilute nitric acid digestion without sonication were generally lower overall when compared to UAD results, illustrating the effect of ultrasound on iodine dissolution. This technique effectively addresses iodine volatilisation and sample losses problem encountered while using classical digestions. Method validation included: defining the detection and quantification limit of iodine using this method were about 2.2 and 8 mg.kg−1, respectively, and it's suitable for the proposed application. Moreover, the repeatability and reproducibility, expressed as RSD for phosphogybsum sample was 7%, 8.3% respectively, while for phosphate samples is tacked as the mean of relative standard deviation 3.4%, 3.8%. Additionally, accuracy of the method was assessed by analysing a certified reference material and the iodine concentration was found to be in good agreement with the indicative values for this CRM. Thus, the mean recoveries in fortified sample were between 96% and 107%.The developed method is fast, accurate, and it is applicable to the monitoring of iodine in the phosphate industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Elemental enrichment at the bottom of PG stack was found for leaching tests. • The dominant dissolved phases of PG are predicted by geochemical modeling. • The release mechanism was classified as dissolution, diffusion, and wash-off. • pH exerts a significant influence on the solubility and mobility of elements. Phosphogypsum (PG), a byproduct during the production of phosphoric acid and phosphate fertilizers, is predominantly stockpiled with a height greater than hundreds of meters. In this study, the leaching behavior of pollutants from PG stored at different depths was systematically investigated through batch tests, column tests, and geochemical modeling. PG samples were collected at different depths within a range of 48 m from a large-scale PG stack in China. The results showed that the pH, electrical conductivity, and elemental concentration of the leachate exhibited spatial variability in terms of the depth distribution, with evident bottom enrichment effects for metals and soluble salts. The pH-dependent leaching tests investigated the impact of pH variations on the solubility of various elements in PG, with a specific focus on elements precipitation occurring within the natural pH range. The geochemical modeling of leaching tests conducted by PHREEQC enabled the identification of the dominant phases controlling the solubilization of the elements, as well as the dynamic process of changes in element forms and concentrations with pH variation. Column leaching tests reveal the differences in pollutant properties between the unsaturated and saturated zones within the PG stack and categorize the leaching mechanisms of elements into three models including dissolution, diffusion, and wash-off. This study aims to reveal the leaching characteristics of PG at different depths, so as to provide a data foundation for the design of liner system, leachate management strategies, and remediation of heavy metal pollution of PG stack sites. [ABSTRACT FROM AUTHOR]

Calcium molybdate (CaMoO4) is of significant interest due to its unique properties and numerous industrial applications, such as catalysis, electrochemistry, and optoelectronics. In this study, we developed an economical and environmentally friendly method to synthesize calcium molybdate from Moroccan phosphogypsum (PG) industrial waste and sodium molybdate, all at room temperature. Comprehensive analysis through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman vibrational spectroscopy, and scanning electron microscopy (SEM) revealed the high purity of the synthesized calcium molybdate, with particle sizes of only 12 nm. Additionally, optical characteristics were studied using ultraviolet-visible spectroscopy (UV-vis), which showed an optical band gap of Egap = 3.96 eV for CaMoO4. These results confirm the successful synthesis of calcium molybdate nanoparticles from Moroccan phosphogypsum, demonstrating an effective pathway to valorize this industrial waste into a valuable material. This approach contributes to environmental sustainability by reducing dependence on rare chemicals while offering innovative solutions for the industry’s sustainable development.

Introduction. Creation of waste-free technologies for production of low-energy building materials and products involving recycling of secondary raw materials is one of the priority areas of economic development in most countries. In this regard, the urgent task is to develop competitive binders based on phosphogypsum with the addition of hydrated lime by designing rational compositions of phosphogypsum-lime compositions hardening by mixed type.Materials and methods. Waste phosphogypsum from Titanium Investments LLC, Armyansk, was used as a secondary sulfate-containing raw material. Hydrated lime for research was obtained by slaking lump lime produced in shaft furnaces of the lime workshop of Crimean Soda Plant JSC, Krasnoperekopsk. Analysis of the mineralogical composition of phosphogypsum and artificial stone based on it was carried out using synchronous TG-DTA/DSC thermal analysis on an STA 8000 analyzer (Perkin Elmer). The dispersed composition of phosphogypsum and hydrated lime was determined by laser diffraction using a Partica LA-960 laser particle size analyzer (Horiba). The determination of the mechanical characteristics of the prototypes was carried out on the basis of the MCC8 control console (Controls).Results. The results of the development of compositions based on phosphogypsum-lime compositions showed that after forced carbonization of these compositions for 180 minutes in an air-gas environment with a 50 % CO2 concentration, it is possible to obtain a water-resistant stone material (Kr 0.78–0.8) with strength at compression 28–32 MPa, average density 1,750–1,780 kg/m3 and water absorption by mass and volume of 11–15 and 19–26 %, respectively.Conclusions. Probably, additional optimization of the conditions of obtaining samples (pressure, water content of the mixture, introduction of filler), the regime of forced carbonate hardening (hardening time, CO2 concentration) will further improve the studied properties of the resulting stone material. The obtained experimental data suggest that, based on the proposed binder, it is possible to produce a certain range of small-piece wall products, taking into account additional scientific research in this area.

This is an article in the field of ceramics and composites. In order to explore a new way for the application of phosphogypsum in road materials, phosphogypsum powder and asphalt mortar were mixed to prepare phosphogypsum modified asphalt. The effects of mixing temperature, powder-binder ratio and polyphosphoric acid content on the three major indicators of phosphogypsum modified asphalt were studied. The research results show that the softening point increases as the mixing temperature increases, and the ductility increased first and then kept constant. Considering energy efficiency and aging temperature, the processing temperature of asphalt should be in the range 135 °C and 145 °C. increasing the powder gum ratio can increase the softening point of the modified asphalt and decrease the ductility of the asphalt. Therefore, the ratio of filler bitumen should not be greater than 0.9 using phosphogypsum as the modifier. The addition of polyphosphoric acid greatly increases the softening point of modified asphalt, but reduces its ductility and penetration. The optimal amount of polyphosphoric acid should be around 1.5%. Infrared spectroscopy (FTIR) and thermogravimetric analysis (TG-DSC) showed that phosphogypsum physically functioned with Asphalt. When polyphosphoric acid was mixed into asphalt, it would react chemically with asphalt. The research results could provide references for the engineering application and theoretical research of phosphogypsum in road materials.

Soda-saline soils pose significant challenges to agricultural productivity, particularly in regions like the foothill plain of the Ili Alatau in southeast Kazakhstan. In this study, we examined the effectiveness of different ameliorants, including phosphogypsum, elemental sulfur, and sulfuric acid, in reclaiming soda-saline soils and enhancing crop yields. The study was conducted under real climatic and production conditions at the "Amiran" LLP farm. Using a randomized complete block design, we assessed the impact of these ameliorants on soil composition and alfalfa yield over two cutting cycles. The experiment involved the application of phosphogypsum, elemental sulfur, and sulfuric acid to designated plots within the farm, each covering an area of 15m2. Soil samples were collected before and after treatment to assess changes in soil composition and salinity. Alfalfa, a resilient perennial crop, was selected for cultivation due to its tolerance to adverse soil conditions. Our findings reveal that all tested ameliorants successfully neutralized the toxic environment of soda-saline soils, resulting in improved soil conditions and increased crop productivity. Phosphogypsum treatment led to a reduction in bicarbonate and carbonate ions, an increase in sulfate ion concentration, and improved soil structure. Elemental sulfur incubation decreased bicarbonate and carbonate ions, further reducing absorbed sodium levels and enhancing soil fertility. Sulfuric acid treatment provided rapid results in reducing alkalinity and increasing sulfate ion concentration, leading to significant improvements in soil quality and crop yield. However, the reclamation of soda-saline solonetzes presented challenges related to soil heterogeneity and poor water permeability. To address these challenges, we recommend the implementation of mechanical destruction of the solonetz soil horizon and deep soil loosening, accompanied by the addition of ameliorants. In conclusion, our study demonstrates the potential of phosphogypsum, elemental sulfur, and sulfuric acid as effective ameliorants for reclaiming soda-saline soils and improving agricultural productivity in challenging environments. By adopting recommended reclamation strategies, farmers can overcome soil limitations and achieve sustainable crop production in regions affected by soda-saline soil degradation.

Microbial geoengineering technology, as a new eco-friendly rock and soil improvement and reinforcement technology, has a wide application prospect. However, this technology still has many deficiencies and is difficult to achieve efficient curing, which has become the bottleneck of large-scale field application. This paper reviews the research status, hot spots, difficulties and future development direction microbial induced calcium carbonate precipitation (MICP) technology. The principle of solidification and the physical and mechanical properties of improved rock and soil are systematically summarized. The solidification efficiency is mainly affected by the reactant itself and the external environment. At present, the MICP technology has been preliminarily applied in the fields of soil solidification, crack repair, anti-seepage treatment, pollution repair and microbial cement. However, the technology is currently mainly limited to the laboratory level due to the difficulty of homogeneous mineralization, uneconomical reactants, short microbial activity period and large environmental interference, incidental toxicity of metabolites and poor field application. Future directions include improving the uniformity of mineralization by improving grouting methods, improving urease persistence by improving urease activity, and improving the adaptability of bacteria to the environment by optimizing bacterial species. Finally, the authors point out the economic advantages of combining soybean peptone, soybean meal and cottonseed as carbon source with phosphogypsum as calcium source to induce CaCO3.

The current study presents the results of the chemical and the radiochemical characterization of phosphogypsum obtained from the former Wizów Chemical Plant in Poland. Phosphogypsum is a residue obtained from phosphoric acid production. Phosphogypsum mainly contains calcium sulfate dihydrate and impurities originating from the source phosphate rock, including toxic trace elements and natural radionuclides. The phosphogypsum stacks occupy a large area and are an environmental issue today. The project “Phosphogypsum Processing to Critical Raw Materials”, currently realized at the Institute of Nuclear Chemistry and Technology, focuses on the use of phosphogypsum from the Polish stacks as material to recover rare earth elements (REEs). The remaining gypsum matrix can be used as an inexpensive material in construction. The chemical and radiological characterization of the radioactive isotopes present in phosphogypsum was performed by using inductively coupled plasma mass spectrometry (ICP-MS) and the gamma spectrometry technique. The radioactivity of the Polish phosphogypsum was then compared with the radioactivity of the phosphogypsum waste present worldwide.

In view of the special engineering properties of red clay and the waste of phosphogypsum resources, the expansion and contraction deformation and fissure evolution of phosphogypsum stabilized red clay under different conditions were investigated by laboratory tests and image processing system. The research results show that: (1) the absolute expansion and absolute shrinkage of phosphogypsum stabilized red clay are positively correlated with the compaction degree, the number of dry and wet cycles and the cement dosage, and negatively correlated with the initial water content and the phosphogypsum dosage; (2) the fissure rate increases with the increase of the number of dry and wet cycles, and decreases with the increase of the initial water content, the compaction degree, the cement, and the phosphogypsum dosage; (3) The relationship among absolute expansion rate (absolute shrinkage), degree of compaction and fracture rate can be fitted by the equation f(x,y) = ax+by+cx2+dy2+e; (4) Phosphogypsum has an obvious inhibiting effect on the expansion, shrinkage and cracking of the mix. It is recommended that the cement mixing amount of 6% and phosphogypsum: red clay = 1:1~1:2 as roadbed filler. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG) is a solid by-product of the phosphate industry, rich in contaminants and produced in large quantities. Raw materials and stabilized specimens, consisting of bentonite-lime-PG mixtures, were characterized by mineralogical, microstructural, chemical, alpha-particle, and gamma-ray spectrometry analysis before hydration and after hardening. Compressive strength and leaching tests were performed on hardened specimens. The physicochemical parameters and chemical composition of leachates from raw materials and hardened specimens were determined. PG contains high concentrations of natural radionuclides, specially from U series. Uranium-238 activities are double in PG than the worldwide average for soil values. The mobility of PTEs from PG is Cd (2.43%), Zn (2.36%), Ni (2.07%), Cu (1.04%), Pb (0.25%), and As (0.21%). Cadmium is the cation most easily released by PG in water with a concentration 0.0316 mg kg−1. When PG is added to bentonite-lime mixture, cadmium is no longer released. The radionuclide 238,234U and 210Po predominates in the leachates of PG. However, the activity of 210Po becomes negligible in the leachates of bentonite-lime-PG mixtures. The addition of PG to bentonite-lime mixtures facilitates the trapping of trace elements (PTEs) and radionuclides, providing potential applications for PG as road embankments and fill coatings. [ABSTRACT FROM AUTHOR]

Phosphogypsum is a solid waste with great environmental stockpile pressure produced by the wet production of phosphoric acid. Although there are various methods to purify and utilize phosphogypsum, the means for environmentally friendly, low energy consumption, and high value-added utilization still need to be further explored. Here, CaSO4·2H2O crystal was directly purified and regulated from phosphogypsum by using the anti-solvent method. The antisolvent can be adsorbed in the c-axis direction of the crystal and further inhibit the growth rate in this direction, resulting in a change in the morphology of the crystal. By adjusting the polarity and chain length of the anti-solvent, the morphology of CaSO4·2H2O crystal can change from butterfly-like flake crystals to hexagonal prism-like crystals. When n-propanol with long chain was used as the anti-solvent, the morphology of the CaSO4·2H2O crystal showed a hexagonal prism with a specific surface area of 19.98 m2/g and a Cu2+ loading efficiency of 52.67%. The encouraging results open up new possibilities for the application of phosphogypsum. [ABSTRACT FROM AUTHOR]

The prolonged impact over the Tinto River estuary by both the significant pollution by acid mine drainage (AMD) affecting this river and the polluted releases from phosphogypsum (PG) piles has led to the severe environmental degradation of this ecosystem. The aim of this work was to assess the current environmental quality of the Tinto River estuary through the study of the spatial distribution of metal(loid)s and natural radionuclides in the surface sediments from the channel edge. The sediments contain mean concentrations 5–20 times higher than the background values for pollutants such as Zn, As, Cu, Pb, or U, and up to two orders of magnitude higher for P. The studied sediments are heavily polluted by toxic heavy metals and metalloids (Pb, Zn, Cu, and As) according to the US EPA guidelines. Most of the analyzed sediment samples are also strongly polluted by long-lived natural radionuclides, mainly U-isotopes and 210Pb with concentrations up to one order of magnitude higher than unpolluted sediments, mostly due to the contribution by the PG leachates. The enrichment factors (EF) were extremely high (EF > 50) for As and very severe enrichment (25 ≤ EF < 50) for P, Cd, Zn, Cu, and Pb. [ABSTRACT FROM AUTHOR]

The study of the reaction mechanism of sea salt solution (SSS) on asphalt binder was important for the development of perpetual asphalt pavements in coastal areas. For this, a novel modifier (MPGJ-I) was developed in this study using phosphogypsum whiskers (PSW) synthesized from phosphogypsum (PSP) wastes, then the prepared composite-modified asphalt binders and base asphalt binders were immersed in the SSS with six concentrations. Then, the surface free energy (SFE) test, rheological tests, and Fourier transform infrared spectroscopy (FTIR) test were used to investigate the function mechanism of SSS on the surface properties, rheological properties, and chemical structure. The results showed that the salt in SSS would gradually transfer to the inside of asphalt binder, and with the increase in SSS concentration, the mass accumulation rate of base asphalt binders increased by 0.84% and 0.72%, whereas the modified asphalt binders only increased by 0.64% and 0.61%, respectively. The MPGJ-I effectively alleviated the decline trend of surface properties, with the incorporation of MPGJ-I, the SFE and cohesive work of base asphalt binders increased by 29.14%–32.83% and 5.23%–48.63%, respectively. In addition, with the increase in SSS concentration, the rutting factor (G*/sinδ), and creep recovery rate (R) of base asphalt binders increased by 15.44%–57.69% and 7.58%–22.34%, respectively, and the fatigue life (Nf) decreased by 6.08%–47.24%. Whereas G*/sinδ and R of modified asphalt binders increased by 10.07%–50.77% and 2.15%–19.35%, respectively, and Nf decreased by 1.79%–8.89%, which meant that the incorporation of MPGJ-I effectively restrained the attack action of SSS on base asphalt binders. There was a chemical reaction between SSS and asphalt binder, and the peak intensity of the new characteristic peaks in asphalt binder was positively correlated with SSS concentration, the incorporation of MPGJ-I could reduce the increasing rate of peak intensity to a certain degree. In addition, the principal component analysis (PCA) model showed that the surface properties and fatigue performance were closely related to the SSS concentration, and this correlation was not affected by the modification effect of MPGJ-I. [ABSTRACT FROM AUTHOR]

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel method has been explored based on the recovery of two industrial wastes V2O5 and phosphogypsum from the fertilizer production industry, which also provide a significant challenge due to their toxicity and environmental impact. To solve the problem of these two harmful wastes, these residues have been transformed into valuable resources, by the elaboration of Nanoparticles vanadate-hydroxyapatite (NPs-HAP/VAP) adsorbent, contributing a sustainable solution without requiring expensive or highly skilled work. This comprehensive investigation explores the adsorption of the reactive red 141 dye (RR 141) on Ca10(VO4) x(PO4)6-x(OH)2, with (xi = 0, 1.5, 3, 4.5, and 6). Using a Centered composite design (CCD), several parameters influencing the adsorption process were examined. The optimal adsorption capacity is 50 mg. g - 1 under optimal conditions 57.5 mg of the adsorbent dose, 152.5 mgL-1 for the RR 141, pH 8, 92.5 minutes of contact time, and incorporation ratio of 4.5 with an R2 of 0.99. These results reinforce the effectiveness of our chosen CCD model. Kinetic analysis demonstrated a pseudoorder reaction model with an R² > 0.92, while the Sips isotherm describes the adsorption process. Thermodynamic studies revealed spontaneous adsorption, suggesting a physical character enhanced by a positive entropy variation. [ABSTRACT FROM AUTHOR]

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This study investigated the synthesis of α-hemihydrate gypsum (α-HH) through semiliquid autoclaving of phosphogypsum (PG) using various carboxylic acids as modifying agents. The impact of carboxyl group spatial location, auxiliary functional group type, and the number of carboxyl groups within the carboxylic acid modifiers on the mechanical strength and crystal morphology of α-HH was analyzed using scanning electron microscopy (SEM), strength testing, and molecular dynamics simulations. The results revealed a significant influence of the carboxylic acid molecular structure on the α-HH crystal morphology. Monocarboxylic acids and dicarboxylic acids with a long carbon chain length between carboxyl groups exhibited preferential adsorption on the (200), (110), and (-110) crystal planes, promoting crystal growth along the c-axis. In contrast, hydroxyl groups and cis double bonds in the modifier structure induced selective adsorption on the (001) plane, hindering growth along the c-axis. Conversely, trans double bonds favored adsorption on the (200), (110), and (-110) planes, enhancing growth along the c-axis. Based on these observations, screening principles for carboxylic acid modifiers were established, suggesting that: 1) the number of carboxyl groups should exceed 2; 2) the optimal carbon atom spacing between carboxyl groups is 3; and 3) auxiliary functional groups such as hydroxyl groups and cis double bonds should be introduced. Modifiers like citric acid, ethylene diamine tetraacetic acid (EDTA), and pyromellitic acid, within concentration ranges of 0.05%-0.1%, 0.1%-0.15%, and 0.05%-0.1%, respectively, yielded α-HH with flexural strengths exceeding 4 MPa and compressive strengths greater than 35 MPa, demonstrating the validity of these principles. [ABSTRACT FROM AUTHOR]

Shrinkage-induced cracking is a common issue in concrete structures, where the formation of cracks not only affects the aesthetic appearance of concrete but also potentially reduces its durability and strength. In this study, the effect of ceramsite sand addition on the properties of a ternary system of cement-ground granulated blast furnace slag (GGBFS)-phosphogypsum (PG) is investigated. In particular, the fluidity, rheology, hydration heat, compressive strength, autogenous shrinkage, and drying shrinkage of the considered mortar specimens are analyzed. The results indicate that an increase in PG content leads to a decrease in fluidity, higher viscosity, lower exothermic peak, and lower compressive strength. However, the shrinkage of the mortar specimens is effectively compensated. The incorporation of internal curing water from ceramsite sand improves fluidity, decreases both yield stress and viscosity, enhances the degree of hydration, and induces mortar expansion. However, the inferior mechanical properties of the ceramsite sand generally produce a decrease in the compressive strength. [ABSTRACT FROM AUTHOR]

A novel synthesis process and characterization of nano-calcium fluoride (n-CaF2) single crystal prepared from phosphogypsum waste. The phosphogypsum (CaSO4·2H2O) powder has been mechanically mixed with NH4F in presence of a controlled amount of water. The mixture still sintered for 48 hours until the formation of nano calcium fluoride particles. The n-CaF2 particles have been characterized by several techniques, The techniques utilized included X-ray diffraction (XRD), infrared spectroscopy (IR), and scanning electron microscopy (SEM). Therefore, it was confirmed that very pure n-CaF2 was obtained with a Ca/F ratio of 0.5 and an average crystalizing size measured according to the Debye-Scherrer equation of 11 nm. Based on the findings reached, The characterization data revealed successful synthesis of n-CaF2 from phosphogypsum. Additionally, the adsorption performance of the elaborated n-CaF2 was tested in Reactive Blue 21 (RB21) anionic dye removal, Adsorption tests were conducted in a batch reactor, focusing on key factors such as contact time, which can significantly influence the adsorption results. adsorption amount, pH, and dye concentration were tested. Hence results show an important adsorption performance of n-CaF2 with Reactive Blue 21 removal rate up to 90%. [ABSTRACT FROM AUTHOR]

Phosphogypsum is a waste from the phosphorus chemical industry which has certain environmental hazards. Using it as a substitute for building materials was thought to alleviate the problems of phosphogypsum pollution and natural mineral consumption. This study tried to develop an environmentally friendly phosphogypsum-based composite filler (PCF) that can be used as a filler in the SMA-13 asphalt mixture. The SMA-13 asphalt mixture was first designed, following which PCF containing phosphogypsum and steel slag powder was prepared. PCF's composition and harmless treatment were determined based on the characterization of the overflowed concentration of fluoride ions, and the pH value of the PCF's leaching solution was evaluated by ion chromatography and a pH meter. The effect of replacing the PCF content in the SMA-13 asphalt mixture was investigated according to high-temperature performance, moisture resistance, and low-temperature performance. Long-term overflowed harmful ion concentrations of PCF-based SMA-13 asphalt mixtures were also included. The results indicate that the steel slag powder content can reduce the overflowed fluoride ion concentration in phosphogypsum. The optimal composition of PCF was 65% phosphogypsum and 35% steel slag powder. The addition of PCF can enhance the SMA-13 asphalt mixture's Marshall stability and dynamic stability when its content is over 20%. SMA-13 asphalt mixtures with PCF can meet the requirements of the specification, although their moisture resistance is reduced by PCF. PCF was proven to increase fracture toughness and energy in a semi-circular bending test at low temperatures, while 40% PCF showed the highest cracking resistance. Furthermore, PCF was able to reduce the long-term overflowed concentrations of fluoride ions and phosphate ions that could meet the environmental requirements. The results of this study provide academic support for the effective consumption of phosphogypsum in road engineering on a large scale. [ABSTRACT FROM AUTHOR]