Solidified Bodies Research Articles

Constitutive model analysis of Chang'e-5 simulated lunar regolith solidified bodies under compression

China’s Chang'e-5 spacecraft successfully collected 1731 g of Lunar regolith and returned it to Earth on December 17, 2020. In this paper, Chang'e-5 simulated Lunar regolith is used as the main material to form stable and dense solid Lunar soil structures by adding different amounts of an inorganic curing agent and water. The internal morphology, failure morphology under uniaxial compression, and stress–strain relationship of the Lunar regolith solidified samples (L-R-S-Ss) are then investigated. The damage constitutive model of the Lunar regolith cured body is analyzed according to the stress–strain curves, with the following results found. (1) Scanning electron microscopy indicates that the L-R-S-Ss contain more microvoids and microfractures, which are the main factors that lead to destruction. (2) The uniaxial failure mode of the L-R-S-Ss is primarily split failure, with both vertical and oblique cracks, with the angle between the main crack and the vertical axis being less than 30°. (3) The content of the curing agent and the amount of water are important factors affecting the L-R-S-S strength. As the water content increases, the L-R-S-S compressive strength tends to decrease. The L-R-S-S strength increases with increasing amount of cementitious material. (4) A cubic polynomial and a rational fraction are used to fit the ascending and descending sections of the L-R-S-S stress–strain curves, respectively, and a piecewise constitutive model of the L-R-S-S specimens is proposed. The calculated results of the model are in good agreement with the experimental curves.

Experimental and numerical studies of the effects of micro/nano carbon fibers in the dynamic behavior of cement-based grouting materials for reinforcement of sand layers

Geological hazards of sand layers pose a serious threat to engineering safety. Grouting reinforcement technology is widely used in such conditions due to its convenience, economy, and effectiveness. To explore the reinforcement effect of carbon fiber (CF) modified cement-based grouting materials on sand layers, grouting solidified bodies (GSB) with CF contents of 0.0%, 0.5%, 1.0%, and 1.5% are selected for Split Hopkinson Pressure Bar (SHPB) impact tests, scanning electron microscope (SEM) scanning, and numerical simulation experiments. The mechanical properties of specimens under dynamic impact conditions and the reinforcement mechanism of CF are studied. Results show that GSB is a strain-rate-dependent material. With the increase of impact rate, peak stress, incident energy, transmitted energy, and dissipated energy of specimens gradually increase, while the integrity of specimens decreases. The CF content remarkably affects the mechanical properties of specimens. When the impact rate is constant, with the increase of CF content, the peak stress and transmitted energy of specimens show a decreasing–increasing– decreasing trend, and the performance of CF-1.0% specimens is optimal. The cement matrix is the main energy storage and release medium, accounting for 97.66% of the energy. When damaged, the cement matrix is mainly fractured. At the microcrack tip, CF influences the direction of crack propagation, reducing the radius of crack propagation, and the main failure mode of CF is debonding. CF can substantially improve the mechanical properties of specimens and reduce the number of cracks. Compared with CF-0.0%-cementitious material (CM) specimens, the peak stress of CF-1.0%-CM specimens is increased by 19.98%. The magnitude of CF force is related to the angle between crack and CF. As the angle increases from 0° to 90°, the CF force gradually increases, reaching the maximum at 90°, with an increase of 133.82%. At this angle, the anti-cracking effect of CF is most substantial. The research results can provide technical support for sand layer grouting reinforcement technology.

Preparation of geopolymer based on municipal solid waste incineration fly ash-phosphorus slag and its function for solidification of heavy metals

Municipal solid waste incineration fly ash (MSWIFA) contains potential contaminants and needs to be efficiently solidified/stablized and so should be managed properly. To achieve this goal, alkali-activated MSWIFA and phosphorus slag (PS) based geopolymer solidified bodies were investigated. Therefore, the mechanical properties of the solidified body, heavy metal leaching characteristics, heavy metal chemical forms, and heavy metal solidification/stabilization mechanisms were also analyzed. The results show that: The addition of an appropriate amount of PS can promote the strength development of a solidified body. When the mass ratio of MSWIFA to PS is 7:3, the strength of the solidified body reaches 22.8 MPa at 90d curing age, which is 5.3 times higher than that of the unmodified material. The MSWIFA/PS immobilized Zn 99.9 %, Pb 99.4 % and Cd 99.8 % in 60 day leaching tests. Meanwhile, PS can significantly increase the proportion of chemically stabilized forms of heavy metals in the solidified body. PS affects on the hydration process of the solidified body. When the mass fraction of PS doping was 30 %, the main hydration products of the solidified body were calcium silicate hydrate (C-S-H) and calcium alumina (AFt). When the mass fraction of PS is 50 %, the main hydration products are calcium aluminosilicate hydrate (C-A-S-H), sodium aluminosilicate hydrate (N-A-S-H), and AFt. These hydration products have good solidification effects on heavy metals. Therefore, it can be concluded that the MSWIFA/PS solidified body is an environmentally friendly and efficient binder.

Research on the environmental stability performance of chromite ore processing residue solidified products.

Chromite ore processing residue (COPR) is a hazardous waste because of leachable chromium, especially Cr(vi). Therefore, ascorbic acid (AA) and blast furnace slag (BFS) have been used to detoxify and solidify COPR. On this basis, environmental stability experiments with high temperature and freeze-thaw cycles were carried out to explore the stability performance of a solidified body with 40% COPR. The environmental stability performance was analyzed through changes in edge length, mass loss, compressive strength development, and leaching concentration of Cr(vi). The result indicated that the high-temperature environment had much more effect on the solidified body than the freeze-thaw cycle environment in these four aspects: after being maintained at 900 °C for 2 h, the compressive strength of the solidified bodies reached its minimum value (35.76 MPa). However, in the freeze-thaw cycle experiments, the compressive strength of the solidified bodies consistently remained above 80 MPa, and the leaching of hexavalent chromium was below the limit (5 mg L-1). In addition, X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR) analysis verified that COPR was effectively solidified through physical and chemical means. Moreover, high temperature changes the molecular structure of the solidified body, thus reducing the compressive strength and curing ability of the solidified body, while the freeze-thaw cycle experiment has little effect on it.

Highly dense calcium phosphate ceramics prepared by self-hydration with hollow silicon calcium additives

Vertebral compression fractures are common nowadays. The application of calcium phosphate bone cement (CPCs) in the treatment of vertebral compression fractures is the research focus, because of its advantages of good biocompatibility, bone conductivity and injectability. However, it is still limited in the clinical application because of its poor mechanical properties. The main reason for the insufficient strength of CPC is that there are many defects inside the solidified body during the hydration reaction. Therefore, we design a kind of hollow silicon calcium additives to regulate the crystallization behavior of CPC hydration products in the self-curing process to achieve the densification of solidified bodies in the microstructure. Firstly, we plan to increase the nucleation site of hydration products during α-TCP hydration to fill structural defects by introducing hollow bioglass. Secondly, we prepare hollow calcium silicon additive by in situ mineralization which can dissolve calcium and silicon ions efficiently are used to regulate the local hydration microenvironment to reduce the crystal size and increase the number of hydration products to obtain a highly dense solidified body structure. The experimental results show that the initial hydration intensity of CPC increased from 18.36 ± 1.72 MPa to 35.37 ± 1.84 MPa, an increase of about 92.65 %. Also, the toughness of the solidified body has been greatly improved, reaching more than 200 %. After 7 days of hydration, the mechanical strength of CPC was further improved, reaching 89.39 ± 3.65 MPa. With the addition of hollow calcium silica additives, we achieved the conversion from calcium phosphate cement to the calcium phosphate ceramic. Our work provides reference value for the clinical replacement of calcium phosphate ceramic for PMMA in vertebral compression fractures.

Study on acid resistance and high temperature resistance of composite geopolymer-stabilized lead–zinc tailing

Geopolymer is regarded as a potential environmentally friendly substitute for ordinary Portland cement, applicable in construction materials. A cementitious material based on coal gangue and blast furnace slag was employed for the solidification/stabilization of heavy metals from lead-zinc tailings, while multi-walled carbon nanotubes were incorporated to enhance the strength of the solidified matrices. The durability of the solidified bodies was assessed against heating at various temperatures (300 °C, 500 °C, 700 °C, 900 °C, and 1100 °C) and exposure to an acid rain simulation solution with varying pH levels (3, 4, and 5). When subjected to heating and immersion in the erosion solution, the inclusion of lead–zinc tailings led to an augmentation in shrinkage, mass loss, strength reduction, and the leaching of heavy metals from the specimens. X-ray diffraction analysis was performed to characterize the phase transformations in the exposed specimens. The compressive strength of the solidified bodies containing 70 wt% lead–zinc tailings decreased significantly under severe conditions. The leaching test results revealed that the leaching concentrations of these specimens remained well below the standard limits. This suggests that the solidified bodies, which were enhanced with multi-walled carbon nanotubes, exhibited good stability.

A novel method for solidification/stabilization of MSWI fly ash by graphene nanoplatelets synergistic alkali-activated technology

Municipal solid waste incineration (MSWI) fly ash with considerable heavy metals needs to be safely disposed of before landfill. In this study, graphene nanoplatelets (GNPs)/MSWI fly ash solidified body was prepared by alkali-activated technology, in order to improve the solidification ability of heavy metals and maximize the utilization of MSWI fly ash to cope with the scarcity of landfill. This paper studied the effect and mechanism of GNPs on heavy metal leaching characteristics. Results showed that solidified body with adding 0.05 wt% GNPs exhibited the highest compressive strength and the lowest heavy metals leaching concentration. Adding GNPs promoted heavy metals in solidified body to be converted into the residual state. Meanwhile, the microstructure and morphology characteristic analysis results indicated that GNPs promoted C-(A)-S-H gels formation. There were various kinds of solidification/stabilization (S/S) mechanisms including physical adsorption, physical encapsulation and chemical bonding in GNPs/MSWI fly ash solidified bodies. This study paves a potential new way for the application of nanomaterials in S/S MSWI fly ash through alkali-activated technology, and graphene is a more promising additive.

Resource utilization of ultrasonic carbonated MSWI fly ash as cement aggregates: Compressive strength, heavy metal immobilization, and environmental-economic analysis

Ultrasonic carbonation technology is effective for municipal solid waste incineration fly ash (MSWI FA) pretreatment. However, the subsequent disposal route is unclear. In this study, the mechanical strength and heavy metal immobilization effects of raw FA (RFA), washed FA (WFA), conventional carbonated FA (CFA), and ultrasonic carbonated FA (UFA) as cement aggregates in the preparation of concrete were investigated in comparison. The reaction kinetic analysis showed that ultrasonic excitation promoted the internal diffusion phase of the carbonation reaction. The compressive strength of the 28-day solidified bodies was in the order of UFA (32.2 MPa) > CFA (22.8 MPa) > WFA (16.4 MPa) > RFA (12.6 MPa). The 3-day UFA solidified body showed the highest degree of hydration and polymerization through 29Si solid-nuclear-magnetic analysis. The nano-CaCO3 in the UFA provided more nucleation sites and hydration reaction sites for the hydration reaction. In addition, the fine UFA particles filled the pores between cement particles, enhancing the strength of the product. Heavy metal leaching tests described that CFA and UFA met the criteria for resource utilization (HJ/T 1134–2020), and the immobilization efficiency of Cu, Pb, and Zn in the UFA solidified body was above 95.6%, 99.3%, and 99.2%, respectively, mainly by the dual immobilization of carbonate chemical precipitation and cement hydration. Considering 11 environmental impact factors and economic benefits, life-cycle-assessment and cost-benefit analysis were selected. The integrated environmental-economic results show that cement usage is the main influencing factor. UFA scenario was recommended as engineering applications with low global warming potential.

Effect of nano silica on solidification/stabilization of heavy metal in alkali-activated MSWI fly ash solidified body

Municipal solid waste incineration fly ash (MSWIFA) containing considerable heavy metals is classified as a hazardous waste. Alkali-activated technology can effectively improve the environmental safety of MSWIFA. Due to the low silica content of MSWIFA, the addition of nano silica (NS) solves the problem to enhance the ability of solidification/stabilization (S/S) and maximize the utilization of MSWIFA. NS/MSWIFA solidified body was prepared by alkali-activated technology in this work. The mechanical and environmental properties of NS/MSWIFA solidified body with various dosages (0–3 wt%). NS were characterized by compressive strength, leaching concentration, and chemical speciation distribution of heavy metals. A comparative study of MSWIFA and solidified bodies for exploring S/S mechanisms was investigated using XRD, FTIR, TG/DTG, NMR, and SEM/EDS tests. The results showed that the leaching concentration of Pb in MSWIFA based on different leaching methods was 23.54 mg/L and 31.7 mg/L, 19.6 times higher than the standard of hazardous waste landfill and 126.8 times higher than the standard of landfill site of municipal solid waste, respectively. The total amount of Zn and Pb was 4739 mg/kg and 2451 mg/kg, respectively, exceeding other heavy metals by 1–2 orders of magnitude. When the addition of NS was 2 wt% and 3 wt%, the compressive strength and the leaching concentration of heavy metals in solidified bodies reached the highest and the lowest, respectively. Comparative analysis indicated that adding NS promoted heavy metals in MSWIFA to be converted into a stable state, and increased hydration product C-(A)-S-H gels formation, making the structure denser. On a broader perspective, NS/MSWIFA solidified body was developed as a low-carbon and environment-friendly binder.

MgO-based binders with different formulations for solidifying Pb and Cd in MSWI fly ash: Solidification effect and related mechanisms

The MgO-based binder is a novel and effective material for solidifying municipal solid waste incineration fly ash (MSWI FA). In this study, the effect of MgO-based binders with different MgO contents on the solidification and stabilization of MSWI FA was investigated by adjusting the proportions of MgO, silica fume, and MSWI FA in the solidified system. The leaching behavior and immobilization mechanisms of Cd and Pb in the solidified bodies were focused on. The hydration products generated were characterized by XRD, FTIR, and TG analysis. The results demonstrated that the compressive strength of the solidified bodies and the immobilization efficiencies of heavy metals improved with the increase in MgO addition. The MSWI FA solidified by MgO-based binders could maintain low leaching toxicity over a wider pH range. The generated Mg-containing hydration products, including Mg(OH)2 and M-C-S-H gels, were believed to contribute to the reduction of the leaching concentrations of heavy metals. The immobilization mechanisms of Pb and Cd were different: the immobilization of Pb came from chemical chelation, and Cd was stabilized from alkaline precipitation. In conclusion, this work provides new insights into applying MgO-based binders in MSWI FA solidification.

Effect and mechanism of nano-alumina on early hydration properties and heavy metals solidification/stabilization of alkali-activated MSWI fly ash solidified body

Municipal solid waste incineration (MSWI) fly ash has serious pollution. It needs to be solidification/stabilization (S/S) to sanitary landfill as quickly as possible. In order to achieve the objective, the early hydration properties of alkali-activated MSWI fly ash solidified body were investigated in this paper. Meanwhile, nano-alumina was utilized as an agent to optimize the early performance. Therefore, the mechanical properties, environmental safety, hydration process and mechanisms of heavy metals S/S were explored. The results showed that after adding nano-alumina, the leaching concentration of Pb and Zn in solidified bodies after 3 d curing was significantly reduced by 49.7–63% and 65.8–76.1%, respectively, and the compressive strength was enhanced by 10.2–55.9%. Nano-alumina improved the hydration process, and the predominant hydration products in solidified bodies were C-S-H gels and C-A-S-H gels. Meanwhile, nano-alumina could obviously increase the most stable chemical speciation (residual state) ratio of heavy metals in solidified bodies. Pore structure data showed that, due to the filling effect and pozzolanic effect of nano-alumina, the porosity has been reduced and the ratio of harmless pore structure has been increased. Therefore, it can be concluded that solidified bodies mainly solidify MSWI fly ash by physical adsorption, physical encapsulation and chemical bonding.

Leaching resistance study on immobilization of MnO2/HMSS with sorbed simulated nuclide strontium by metakaolin-based geopolymers

Radioactive waste generated in nuclear energy utilization poses great environmental risks, and the safe disposal technology has become a hot research topic in the field of nuclear environmental security. Immobilization is a common radioactive waste disposal technique, and the leaching resistance of the solidified body is the key to safe disposal. In the study, metakaolin was used as a raw material to solidify strontium, a common nuclide in radioactive waste streams, and then conducted leaching resistance tests. Using control variables, the experiments were used to investigate the effects of adsorption pretreatment prior to solidifying, solidifying with and without the addition of adsorbent on the effect of immobilization. The leaching resistance of the solidified bodies were investigated in three leaching environments: 25℃ deionized water, pH=1 sulfuric acid solution, and 5%wt magnesium sulfate solution during the 42d test cycle. The results showed that both leaching rate and cumulative leaching fraction of the 42d samples for the leaching resistance of radioactive waste immobilization under the environment of deionized water at 25℃. For the three leaching conditions, the adsorption pretreatment with (4:1)MnO2/HMSS before solidifying or the addition of (4:1)MnO2/HMSS while solidifying could effectively improve the leaching resistance of solidified body, and the former was more effective. The results of this study can provide reference for the disposal of strontium-contanining radioactive waste.

Solidification/stabilization of chromite ore processing residue via co-sintering with hazardous waste incineration residue.

In order to realize the harmless and resource disposal of hazardous waste incineration residue (HWIR) and chromite ore processing residue (COPR), this paper prepares glass-ceramics by HWIR. The COPR was co-sintered with the base glass of HWIR to realize the solidification and stabilization of COPR. The results shown that the single-stage sintering method has a simple process and low energy consumption, while the two-stage sintering method has better mechanical properties. Chromium in COPR may be solidified/stabilized by physical encapsulation and chemical fixation. When the content of COPR reaches 50%, the leaching concentration of Cr and Cr(VI) in the solidified body of HWIR solidified COPR (IRSC) is less than 5mg/L, which satisfies the US EPA and CN GB5085.3 standard limits. This study achieves waste control by waste and prepares solidified bodies (IRSC) with good mechanical properties, chemical corrosion resistance, and low leaching concentration of heavy metals, which provides feasibility for its engineering application.

Electrochemical response of solidification Cu2+ contaminated soil influenced by red mud/fly ash ratio

The main purpose of this work was to study a new method for evaluating the solidification of contaminated soil based on electrochemical impedance spectroscopy (EIS). To explore how the EIS parameters were affected by the pore structure and mesostructure of the cured system, the physical and mechanical properties, leaching toxicity, microstructure, and EIS of the stabilized contaminated soil were tested after 7, 28, 60, and 90 days of curing. Based on the EIS results, a physical and equivalent circuit model of the stabilized contaminated soil's impedance response was established to reveal the mechanism of binder-heavy metal ion-soil interaction. The results showed that as the red mud (RM)-fly ash (FA) mass ratio and curing age increased, the strength and structural compactness of the solidified body also increased. The best curing effect was achieved with an RM-FA mass ratio of 7:3 after curing for 90 days. The equivalent circuit model of the solidified body obtained by EIS was Rs (Q1 (Rct1W) Q2Rct2). The pore solution resistance Rs, solid-liquid interface ion transfer resistance Rct 1, and unconfined compressive strength (UCS) qu all showed an increasing trend with increasing RM-FA mass ratio and increasing curing time. Fitting the model demonstrated that both Rs and Rct1 were closely correlated with the strength of the solidified bodies. These conclusions were further verified by scanning electron microscope (SEM) experiments. Overall, this work demonstrates that the strength characteristics of solidified bodies can be evaluated by EIS and reveals the microscopic mechanism of the solidification of Cu2+-contaminated soil.

Electrochemical response and effect evaluation of high belite sulphoaluminate cement combined with red mud-fly ash on solidification of Cu2+-contaminated kaolin

In this paper, the solidification of Cu2+-contaminated kaolin by high belite sulphoaluminate cement (HBSC) combined with red mud (RM) and fly ash (FA) was investigated. The effects of solidification/stabilization (S/S) and its electrochemical responses were experimentally explored by mixing RM and FA as the main raw materials with small amounts of low-energy HBSC and quicklime serving as solidifiers of heavy metal contaminated soil. The solidification mechanism of the solidifier on Cu2+ and its solidification effect were then systematically investigated by analyzing the unconfined compressive strength (UCS) of the solidified body, toxic leaching, permeation characteristics, and surfaces morphologies. The study of the electrochemical response of the solidified body during the solidifying and remediation process allowed the development of an evaluation method for repairing the effect of Cu2+-contaminated kaolin based on electrochemical impedance spectroscopy (EIS). The results showed that the strength, impermeability, and leaching toxicity of solid waste co-HBSC solidifying of contaminated soil met industrial requirements. The incorporation of low energy consumption HBSC generated a mass ratio of RM to FA of 8:2 with the best solidification effect. Heavy metals can be absorbed by chemical precipitation, displacement reactions, and encapsulation by hydration gels. In addition, the electrochemical impedance characteristics of the solidified bodies were found consistent with the conventional evaluation of the solidification effect. In sum, HBSC synergistic solid waste solidifier looks very promising for use in the S/S remediation of Cu2+-contaminated soil.

Solidification and stabilization of harmful elements in antimony tailings and synergistic utilization of multiple solid wastes

The massive generation and accumulation of tailings potentially lead to environmental pollution. Antimony tailings (AT) have higher environmental risks than other types of tailings and thus require special attention. Hence, this article used a variety of industrial solid wastes to solidify and stabilize the harmful components in AT. The solidified bodies prepared by adding different ratios of AT were cured under standard and natural curing conditions, and a series of performance tests and leaching toxicity analysis were performed. The results show that the solidified bodies containing 1000 g AT demonstrates excellent mechanical properties after standard curing for 28 d, with a compressive strength of 15 MPa and flexural strength of about 2.5 MPa. The solidified bodies have a water absorption rate of around 27%, softening coefficient of about 0.7, dry density of 900 kg/m3 and wet density of 1100 kg/m3, which meet waterproof and lightweight requirements. In addition, according to leaching toxicity analysis, the solidified bodies meet environmental standards. The bonding effect of needle-shaped ettringite and the encapsulation and filling effect of gelling substance are beneficial to the solidification and stabilization of AT. This article provides theoretical basis and research ideas for AT treatment and disposal.

Solidification of uranium mill tailings by MBS-MICP and environmental implications

Uranium mill tailing ponds (UMTPs) are risk source of debris flow and a critical source of environmental U and Rn pollution. The technology of microbial induced calcium carbonate precipitation (MICP) has been extensively studied on reinforcement of UMTs, while little attention has been paid to the effects of MICP on U & Rn release, especially when incorporation of metakaolin and bacillus subtilis (MBS). In this study, the reinforcement and U & Rn immobilization role of MBS -MICP solidification in different grouting cycle for uranium mill tailings (UMTs) was comprehensively investigated. The results showed that under the action of about 166.7 g/L metakaolin and ∼50% bacillus subtilis, the solidification cycle of MICP was shortened by 50%, the solidified bodies became brittle, and the axial stress increased by up to 7.9%, and U immobilization rates and Rn exhalation rates decrease by 12.6% and 0.8%, respectively. Therefore, the incorporation of MBS can enhance the triaxial compressive strength and improve the immobilization capacity of U and Rn of the UMTs bodies solidified during MICP, due to the reduction of pore volume and surface area, the formation of more crystals general gypsum and gismondine, as well as the enhancing of coprecipitation and encapsulation capacity.

Upcycling of air pollution control residue waste into cementitious product through geopolymerization technology

This study explores the possibility of using geopolymerization technology (GT) to immobilize the potentially toxic elements (PTEs, e.g., Zn, Cu, Cr, As) in the APCr and convert it into useful cementitious product. To maximize its recycling, the amount of APCr in the designed product was increased gradually from 20% to 80% by the total solid mass. Leaching test showed that GT can effectively immobilize the PTEs in the APCr solidified samples without any health and environmental concerns. The compressive strength of samples can exceed 18 MPa at 28 days at a highest amount of 80% APCr through GT. Thermogravimetric analysis (TGA) results showed that solidified samples underwent mass loss due to evaporation of free and physically bound water at low temperatures (<200°C) and melting and evaporation of soluble salts in APCr at high temperatures (>800°C). Characterization of solidified samples conducted through the X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy-Energy dispersive analysis (SEM) revealed the formation of C-A-S-H and N-A-S-H gels in solidified bodies and verified that APCr was successfully solidified and embedded into the geopolymer network structure

The Utilization of Alkali-Activated Lead-Zinc Smelting Slag for Chromite Ore Processing Residue Solidification/Stabilization.

Lead–zinc smelting slag (LZSS) is regarded as a hazardous waste containing heavy metals that poses a significant threat to the environment. LZSS is rich in aluminosilicate, which has the potential to prepare alkali-activated materials and solidify hazardous waste, realizing hazardous waste cotreatment. In this study, the experiment included two parts; i.e., the preparation of alkali-activated LZSS (pure smelting slag) and chromite ore processing residue (COPR) solidification/stabilization. Single-factor and orthogonal experiments were carried out that aimed to explore the effects of various parameters (alkali solid content, water glass modulus, liquid–solid ratio, and initial curing temperature) for alkali-activated LZSS. Additionally, compressive strength and leaching toxicity were the indexes used to evaluate the performance of the solidified bodies containing COPR. As a result, the highest compressive strength of alkali-activated LZSS reached 84.49 MPa, and when 40% COPR was added, the strength decreased to 1.42 MPa. However, the leaching concentrations of Zn and Cr from all the solidified bodies were far below the critical limits (US EPA Method 1311 and China GB5085.3-2007). Heavy-metal ions in LZSS and COPR were immobilized successfully by chemical and physical means, which was detected by analyses including environmental scanning electron microscopy with energy-dispersive spectrometry, Fourier transform infrared spectrometry, and X-ray diffraction.

Experimental study of different admixture effects on the porosity and U(VI) leaching characteristics of uranium tailing solidified bodies in acid rain environments

Experimental study of different admixture effects on the porosity and U(VI) leaching characteristics of uranium tailing solidified bodies in acid rain environments