Phosphorus Slag Research Articles

Understanding the acting mechanism of NaOH adjusting the transformation of viscoelastic properties of alkali activated phosphorus slag

The transformation of the viscoelastic properties of alkali activated phosphorus slag fresh pastes (AAPS) from the viewpoints of both dispersion effect and hydration was investigated by the in-situ measurement of a microrheology analyzer basing on the measurement of the mean square displacement of particles (MSD). Measurements on microrheological properties, zeta potential, X-ray diffraction, calorimetric response, infrared spectroscopy, SEM and thermogravimetric analysis of AAPS, were carried out. Corresponding parameters (that is Elasticity index (EI), Macroscopic viscosity index (MVI), storage modulus (G′), loss modulus (G″)) were extracted from the MSD curves to quantitatively analyze the changes of viscoelastic properties of AAPS with different NaOH content. Results shown that different NaOH content can lead to notable changes on the viscoelastic properties of AAPS on the base of the various dispersion degree and hydration process of pastes. With the increasing of NaOH content (S1–S5), the transformation of the viscoelastic properties on the AAPS was delayed in terms of the evolution of microrheological parameters with escape time, which owed to the low hydration rate of AAPS merely generating the small quantity of hydration products. In addition to this, electrostatic repulsive force between particles was enhanced promoting the dispersion effect. On the contrary, when the concentration of NaOH reached a threshold (S6–S8), the transformation rate of the viscoelastic properties on the AAPS pastes significantly accelerated. The result was attributed to that higher hydration rate led to more hydration products and stronger cross-linking for inter-particles, together with the decreasing electrostatic repulsive force.

Evaluation of phosphorus slag (PS) content and particle size on the performance modification effect of asphalt

To evaluate the modification effect of phosphorus slag powder (PSP) on the rheological performance of asphalt, five types of PSP with different particle sizes and different content were prepared and added into the AH-70 base asphalt. The dynamic shear rheometer (DSR) test was used to evaluate the influence of PSP content and particle size on the rheological properties of asphalt. Rolling thin film oven test (RTFOT) and pressure aging vessel (PAV) were used to simulate the asphalt aging after modification of PSP. The influence of aging conditions on the phosphorus slag modified asphalt (PSMA) was evaluated, and the impact of PSP on the function group of asphalt was analyzed by Fourier Transform Infrared spectroscopy (FTIR). The results indicated that the interaction between PSP and asphalt was mainly physical blending with some degree of chemical reactions. PSP was more sensitive to aged asphalt but less sensitive to original asphalt because it could react with some carbonyl groups. With the increase of PSP content, the shear complex modulus of PSMA increased first and then decreased, and the phase angle decreased first and then increased after RTFOT aging. With the increase of the specific surface area of PSP, the complex shear modulus of PSMA increased and the phase angle decreased. The result found that with the increase of the specific surface area, the high temperature rutting resistance and fatigue performance of asphalt was improved. This study provided important theoretical and practical guidance for the application of PSMA.

Synthesis and characterization of calcium carbonate whisker from yellow phosphorus slag

AbstractIn this study, a procedure for producing calcium carbonate whisker through yellow phosphorus slag carbonation without adding any crystal control agents was proposed. The influence of process parameters on the crystal phase and morphology of the product was discussed. The content of aragonite in the product was more than 90% under optimal conditions. The whiteness of the product was 97.6%. The diameter of a single particle was about 1.5–3 μm, and the length of a single particle was about 8–40 μm. Various polymorphs and morphologies of CaCO3 could be formed by adjusting the production conditions. The by-products produced during the whole preparation process could also be reused. The whole preparation process of fibrous aragonite from yellow phosphorus slag without using any chemical additives was also proposed. These indicated that the production strategy had a good application prospect.

PHYSICAL AND CHEMICAL PROCESSES OCCURRING IN THE GRANULATED PHOSPHORUS SLAG DUMPS

One of the most dangerous man-made mineral formations located in the territory of Kazakhstan is disposal areas for granulated phosphorus slag, since its shells contain initially the dangerous gases such as PH3, H2S, HF, etc. Permanent sources of such gases are also Ca3P2 (intrinsically poisonous gas), CaS and CaF2. In the structures of phosphorous ash disposal areas, the chemical and physical-chemical processes contain initially gases, which may be in different modifications. For example: • Phosphene (PH3) in the form: PH3→P2O5→HPO3→H3PO4; • Hydrogen sulfide (H2S): H2S→H2SO3→ H2SO4; • Hydrogen fluoride and silicon tetrafluoride: HF→SiF4→H2SiF6→H2SiO3; • Carbon oxide (СО): СО→СО2→СОСl2. Such chemical processes intensify greatly the anthropogenic effect of phosphorous ash disposal areas on the environment – biogeocoenosis. In addition to the processes related to gas components, in the phosphorous ash disposal areas, the hydration processes occur as a result of interaction of slag with water. Thereat, sub-microcrystalline CSH(I) and calcium are generated. Depth of slag hydration reaches 1…3 μm. Such processes form a thin layer on the surface of slag particles resulting in linking of separate grains into a whole. Therefore, the surface of phosphorous ash disposal areas has the certain strength with cracks, through which water, air, snow, etc. are penetrating into the disposal area. It is evident that granulated phosphorus slag in the form of disposal areas has very adverse impact on the biogeocoenosis, causing the pressing need for their disposal; moreover, such slags are valuable raw material for the construction industry and agriculture only after their decontamination from dangerous gases. Keywords. Granular phosphorus slag, dumps, hazardous gases, chemical reactions.

The effect of NaOH content on rheological properties, microstructures and interfacial characteristic of alkali activated phosphorus slag fresh pastes

This study focused on the effect of NaOH activators content on rheological properties, microstructures and interfacial characteristic of alkali activated phosphorus slag (AAPS) fresh pastes. Various parameters including rheological properties (fluidity, yield stress, and apparent viscosity), microstructures (flocculent structure, particle size distribution and geometrical properties of agglomerate structures) and interfacial characteristic (zeta potential) of AAPS fresh pastes with different NaOH activators content, were acquired, respectively. Morphologi G3 microscope was used to quantitatively analyze the microstructure properties of AAPS fresh pastes. Results shown that the effect of NaOH content on rheological properties of AAPS was attributed to the changes in the microstructures and interfacial characteristic of fresh pastes. With NaOH activators content increased, flocculent structures with smaller size were evenly distributed, and chain agglomerate structures with low binding force gradually substituted for group agglomerate structures with strong stability corresponding to greater elongation and smaller HS Circularity. This phenomenon could also be partly ascribed to stronger electrostatic repulsive force between particles in the high alkaline environment, leading to greater dispersion effect of free water on particles.

Reaction Mechanism Analysis of Phosphorus Slag - Fly Ash - Phosphorus Gypsum - Cement Foamed Concrete

In this study, phosphorous slag powder, fly ash and cement were used as composite cementing materials, and phosphogypsum was used as the activator of phosphorous slag powder and fly ash to stimulate their activity. The hydration reaction of cement, phosphorus slag powder, fly ash and phosphogypsum was studied. The results show that the hydration products of cement, cement + phosphorous slag powder, cement + phosphorous slag powder + fly ash, and cement + phosphorous slag powder + fly ash + phosphorous gypsum have the same mineral composition but different relative content. The hydration samples of cement, cement + phosphorous slag powder, cement + phosphorous slag powder + fly ash, and cement + phosphorous slag powder + fly ash + phosphogypsum have certain differences in microstructure and quantity, especially ettringite. Cement hydration can stimulate the activity of phosphorus slag powder and fly ash, in turn, the addition of phosphorus slag powder, fly ash and phosphogypsum can promote the hydration process of cement, improve the quality of hydration products, and improve the density of concrete structure.

Mechanical and durability properties of self-compacting concrete made with fly ash microbeads and phosphorous slag powder

The self-compacting concrete with two kinds of pozzolanic admixtures of fly ash microbeads (FB) and phosphorus slag powder (PS) was studied in this work. The mechanical properties and durability of self-compacting concrete with different admixtures were investigated and the results indicated that the concrete workability is best when FB and PS were 15%, respectively. While early mechanical properties were not as good as the control samples, but long-term strength exceeded the control from extending over curing time. Chloride ion permeation test proved that the sample of self-compacting concrete with 15% FB had the lowest electrical flux for the value for 1690 Coulombs and the minimum diffusion coefficient for 5.30 × 10−8 m2/s. The effect of improvement to PS on mechanical properties and electric flux was not as good as that of FB. Meanwhile, XRD, TGA-DTG, and SEM tests were performed on the samples for curing 7 days and 28 days. XRD test showed a 28-day peak of Calcium Hydroxide has a dramatic drop for CFB-15%. TGA-DTG test showed that the 28-day hydration degree of CFB-15% was 64.08%, which was much higher than that of the control group and CPS-15%. SEM test proved the spectacular filling property and pozzolanic effect of FB varied the interfacial adhesion of the cement particles. Mercury intrusion experiments indicated the amount of internal pore decreased with the addition of FB and PF.

Reaction kinetics and kinetics models of alkali activated phosphorus slag

The kinetics of alkali activation of phosphorus slag (PS) is highly related to silicate modulus of the activator and reaction temperature. In present study, it was probed into the hydration reaction kinetics of PS activated by a combination of water glass and sodium hydroxide. The influence of reaction temperatures (from 25 ℃ to 60 ℃) and the activator silicate modulus (Ms, SiO2/Na2O ratio by mass, from 1 to 2) on the hydration reaction kinetics of AAPS were explored by isothermal calorimetric test. The three kinetic models (the exponential mode, the Knudsen linear dispersion mode and the Jander mode) were selected to extract the correlation parameters and quantitatively analyze the acting mechanism on the hydration reaction kinetics of AAPS. The results showed that the effect of different reaction temperatures and Ms on the hydration reaction kinetics of AAPS were prominent. The exponential method was able to satisfactorily model the hydration reaction kinetics of AAPS pastes. However, higher reaction temperatures and lower Ms were required to abstract the desired kinetic parameters when the Knudsen linear dispersion model was used. With the varied curing temperatures and Ms, the variation trends of the time parameters τ and τo (from the exponential mode and the Knudsen linear dispersion mode, respectively) were in line with those trends that the time to acceleration peak and the ending time of induction stage, respectively. According to the Jander model, the rate controlling processes of AAPS shifted from phase boundary reaction controlling process (the N values less than 1) to diffusion controlling process (the N values more than 1) with decreasing Ms and increasing curing temperatures in the case of higher temperature and lower Ms, respectively. On the contrary, phase boundary reaction controlling process kept unchanged at lower temperature (25 °C) and higher Ms (2). Therefore, the conversion of the rate controlling processes of AAPS was responsible for the differences in the hydration reaction kinetics of AAPS.

Study on the Preparation and Fracture Behavior of Red Mud-Yellow Phosphorus Slag-Based Concrete

Serious environmental pollution issues caused by the storage and exposure of large amounts of red mud (RM) and yellow phosphorus slag (YPS) have raised significant concerns. Red mud-yellow phosphorous slag-cement concrete (RM-YPS-CC) is prepared with 25% yellow phosphorus slag content (YPSC) and 10% red mud content (RMC) to replace a portion of the cement at the age of 28 days and was found in this study to satisfy the mechanical property requirements. More ettringite and portlandite were generated with the RM-YPS-CC than with the yellow phosphorous slag-cement concrete (YPS-CC). In addition, the cementitious materials were more interlaced, and there was more disorder in the crystals of the RM-YPS-CC, which formed a more complex spatial structure than the YPS-CC did. Without RM, the initial cracking strength on the surface of the concrete was 5–6 MPa, the maximum crack width was 3.96 mm, and the crack number was 8. However, the cracking strength was 26.5–27 MPa with RMC5, the maximum crack width was 0.66 mm with RMC15, and the crack number was 3 with RMC15. Moreover, studies using the digital image correlation (DIC) method indicated that the displacement distribution and evolution of the first crack area changed quickly at 10 MPa in either horizontal or vertical direction, and a similar trend was maintained from 10 MPa to 27.1 MPa for the YPS-CC. However, with a small distribution and evolution of horizontal or vertical displacement from 5 MPa to 25 MPa, the evolution would change rapidly when reaching 30 MPa for RM-YPS-CC. This study aims to provide new insights into the wide application of YPS and RM for saving energy and reducing emissions and to develop a new method to study the fracture behavior of concrete.

Mineral carbonation of yellow phosphorus slag and characterization of carbonated product

A procedure for producing high-purity CaCO3 by yellow phosphorus slag carbonation was proposed. The impacts of technological parameters on acid-leaching and carbonation results were discussed. The calcium leaching rate was 99.8%, while the acid-leaching product was amorphous silicon dioxide with granular morphology and some pores in the surface. The carbonation ratio was 98.10%: 1 t of yellow phosphorus slag can be used to produce 881 kg of CaCO3 and sequester 388 kg of CO2 under the optimized conditions. The CaCO3 satisfied the Chinese recommended industrial standard of HG/T 2226-2010. The products with a single calcite or vaterite structure, or binary and trinary mixed structure of calcite, vaterite and aragonite were all successfully prepared. A preliminary economic evaluation predicted that our yellow phosphorus slag carbonation procedure held a promising application for CO2 sequestration.

Effect of Phosphorus Slag Powder on Flammability Properties of Asphalt

AbstractThe consequences of asphalt pavement in a long tunnel under fire are much more serious than in open air conditions. Micropowder additives directly affect the characteristics of the asphalt ...

Non-explosive mining and waste utilization for achieving green mining in underground hard rock mine in China

Abstract Innovations of mining technologies were proposed by beneficial utilizations of unfavorable factors such as high geostress, high geotemperature and high mining depth to achieve green mining as mining depth increases inevitably. Cuttability of deep hard rock was investigated by experimental and regressed analyses to find the reasonable stress adjustment method to improve non-explosive mechanized fragmentation for hard ore-rock. A non-explosive mechanized and intellectualized mining method was proposed to continuously and precisely exploit phosphate underground, which promoted the high-recovery, low-waste and high-efficiency exploitation of phosphate with recovery rate over 90%, dilution rate near 5% and cutting efficiency about 107.7 t/h. A circular economy model and the backfill system were proposed to conduct resource utilizations of solid waste, by which the utilization amount of waste increased year after year. In 2018, the utilization amounts of phosphogypsum, yellow phosphorus slag and waste rock increased to 1853.6×103 t/a, 291.1×103 t/a and 1493.8×103 t/a, respectively.

Strength development and acid resistance of geopolymer based on waste clay brick powder and phosphorous slag

AbstractThis study aims to investigate the strength development and durability of geopolymer mortars based on waste clay brick powder (WCBP) and phosphorus slag exposed to acid attack. WCBP was partially replaced with slag (8, 16, and 24 wt%) and resulting blends were activated by an aqueous solution of NaOH and sodium silicate with different SiO2/Na2O ratios (MS) and Na2O concentrations. The optimized geopolymer mortar specimens were also immersed in sulfuric and hydrochloric acid solutions of pH = 1 for 6 months to assess changes in their physical and structural properties. The results were compared with those of Portland cement and high alumina cement mortars as control specimens. The key durability parameters measured were the evaluation of mass change, compressive strength loss, and deteriorated depth. Complementary studies were also carried out using X‐ray diffractometry, Fourier transform infrared spectroscopy, and scanning electron microscopy in line with energy dispersive X‐ray techniques to quantify the compositional and microstructural changes. The results demonstrate a potential of value‐added reuse application for WCBP by adding a suitable amount of slag. The findings also showed that geopolymer mortars were less susceptible to acid attack than the control mortars; however, superior enhancement in durability properties was not achieved.

Study on Phosphorus Slag Activation Technology and Preparation of Phosphate Slag-Based Cementitious Materials

In the paper, phosphorus slags were the main raw material.Orthogonal experiment method and single factor experiment method were used to determine the optimal process parameters for exciting phosphorus slag portland cement. The results show that the phosphorus slag mixture contained 0.05-0.07% triethanolamine,1.5-2% NaCl,1.5-1.8% Na2SO3. The phosphorus slag-based cementitious material was prepared by using the superior phosphorus slag active excitation scheme. The early and late activity indexes of the phosphorus slag-based can effectively support the large-scale resource utilization of phosphorus slag.

Hydration heat evolution of high-belite cement–phosphate slag binder

The influence of phosphate slag with different finenesses and activators on the hydration of high-belite cement has been studied by using the hydration heat of binders, the DTA curves, the SEM images, and the specific strength. Results indicated that doped phosphorus slag in the cement will reduce heat of hydration. The activity of phosphate slag was low at early stage, but pozzolanic activity of phosphorus slag is higher than that of fly ash. Increasing the specific surface area and curing time and using Ca(OH)2 combined with gypsum can clearly promote the hydration degree of phosphorus slag. The findings in this paper show that since phosphorus slag can promote the hydration of high-belite cement, the strength contribution of cement is increased. Moreover, the greater the specific surface area is, the more significant the promotion effect at 90 d is.

Radioactivity of Five Typical General Industrial Solid Wastes and its Influence in Solid Waste Recycling

The level of radionuclides is an important index for the preparation of building materials from industrial solid waste. In order to investigate the radiological hazard of five kinds of typical general industrial solid wastes in Guizhou, China, including fly ash (FA), red mud (RM), phosphorus slag (PS), phosphogypsum (PG), and electrolytic manganese residue (EMR), the radiation intensity and associated radiological impact were studied. The results show that concentrations of 238U, 235U, 232Th, 226Ra, 210Pb, and 40K for different samples vary widely. The concentration of 238U was both positively correlated with 235U and 226Ra, and the uranium contents in the measured samples were all of natural origin. The radiation levels of PG, EMR, EMR-Na (EMR activated by NaOH), and EMR-Ca (EMR activated by Ca(OH)2) were all lower than the Chinese and the world’s recommended highest levels for materials allowed to be directly used as building materials. The values of the internal and external illumination index (IRa and Iγ, respectively) for FA and RM were higher (IRa > 1.0 and Iγ > 1.3 for FA, IRa > 2.0 and Iγ > 2.0 for RM). The radium equivalent activity (Raeq), indoor and outdoor absorbed dose (Din and Dout, respectively), and corresponding annual effective dose rate (Ein and Eout) of RM, PS, and FA were higher than the recommended limit values (i.e., 370 Bq/kg, 84 nGy/h, 59 nGy/h, 0.4 mSv/y, and 0.07 mSv/y, respectively), resulting from the higher relative contribution of 226Ra and 232Th. The portion of RM, FA, and PS in building materials should be less than 75.44%, 29.72%, and 66.01%, respectively. This study provides quantitative analysis for the safe utilization of FA, RM, PS, PG, and EMR in Guizhou building materials.

Refining of high-phosphorus manganese alloys, which are formed during electrometallurgical Dephosphoration of manganese ore

Goal. Creation of the most rational way of dephosphorization of manganese alloys. Method. Thermodynamic calculations to establish the preference of the reactions during dephosphorization. Computer modeling of the influence of the charge composition on the process of reducing the phosphorus content. Experimental studies in the laboratory during a two-stage processing of high phosphorus metal. Results. The results of computer modeling and experimental study of the refining process of manganese alloy with high content of silicon and phosphorus indicate the feasibility of using the experimental slag-forming mixture based on Na4SiO4. Comparisons of the calculated data with the results of experimental melting show that there are differences in their values. These differences are due to the fact that in real conditions the thermo-dynamic forecast does not always coincide with the kinetics of the real process. The obtained experimental data indicate that the analyzed system achieves a state of dynamic equilibrium in contrast to the data of thermodynamic calculations by the program, which does not take into account the kinetics of the real process and the assumptions made in the simulation. Scientific novelty. The results of experimental studies have shown that the adopted physico-chemical features of the one-stage method of refining the alloy from silicon and phosphorus at a temperature of ~ 1350oC, provide protection of manganese from oxidation with the use of Na4SiO4. Practical significance. Therefore, it is advisable to implement the developed scheme of dephosphorization of the accompanying manganese alloy, which is formed during the production of low phosphorus slag, in industrial conditions. Given that the limiting link in the refining process is the oxidation reaction of the phosphorus alloy due to the interaction with Fe2O3, it is advisable to use forced mixing of the metal and the alloy by purging with neutral gas. Key words: phosphorus, manganese ore, concomitant manganese alloy, low phosphorus slag, dephosphorization,

Predicting Gaseous Pollution of Sintered Brick Preparation from Yellow Phosphorus Slag

Predicting Gaseous Pollution of Sintered Brick Preparation from Yellow Phosphorus Slag

Migration and transformation behavior of harmful elements of lightweight ceramsite preparation from yellow phosphorus slag

In order to investigate the pollution behavior during the preparation of lightweight ceramsite from yellow phosphorus slag, the migration and transformation of the P-, S-, F-, and As-containing species in the heating system were simulated and calculated by FactSage 7.1 thermochemical software and databases. The results show that the P in the solid of Ca10(PO4)6F2 is transformed to solid Fe3P and a small amount of gaseous (P2O3)2. The S-containing gaseous pollutants (CS2, S2, PS and COS) start to appear, while a large amount of S remains in the solid phase of CaS. A small amount of F is released in the form of SiF4, and all As exists in gaseous products. At temperatures ranging from 100-1100°C, P, S, F, and As elements cannot be transformed into the slag phase.

Modeling the influence of chemical composition on compressive strength behavior of alkali-activated phosphorus slag cement using statistical design

In this study, a statistical experimental design based on response surface methodology (RSM) has been applied to predict and optimize the compressive strength of alkali-activated phosphorus slag in different ages (3, 7, and 28 days). For this purpose, the binder samples were prepared with different molar ratios of SiO2/Na2O (S/N), Na2O/Al2O3(Na/Al), and H2O/Al2O3(H/Al) as alkali activator. Results showed that S/N molar ratio plays its role in early ages of curing and Na/Al molar ratio, and showed its significant effect on 7 and 28 days of compressive strength. H/Al molar ratio had the most significant effect on compressive strength compared to the other parameters. The derived RSM models were statistically adequate and could be used to predict the compressive strength. The optimum chemical composition of activator to obtain the highest compressive strength was achieved as 0.39, 1.34, and 30 for S/N, Na/Al, and H/Al molar ratios, respectively, with compressive strength of 30, 65, and 100 MPa at 3, 7, and 28 days of curing.