Human health risk assessment of volatile organic compounds in oil-based drill cuttings of shale gas.

Waste oil-based drill cuttings contain dioxins and volatile organic compounds (VOCs), which have the potential to cause serious health effects in humans. Therefore, this paper took oil-based drill cuttings (OBDCs) as the research object and carried out the testing of VOCs and dioxins content by using GC-MS and HRGCS-HRMS and comprehensively evaluated the content, composition and distribution pattern of VOCs and dioxins and the risk to human health posed by the two pollutants in OBDCs. The results showed that the VOCs did not exceed the emission limits in ESPPI (GB 31571-2015), but it is vital to recognise that 1,2-dichloropropane has the potential to cause cancer risk, with soil and groundwater risk control values of 662.95 mg·kg-1 and 0.066 mg·kg-1, respectively. Benzene, 1,2-dichloropropane and 8 other VOCs pose a non-carcinogenic risk to humans. The levels of polychlorinated dibenzofurans (PCDFs) exceeded those of polychlorinated dibenzo-p-dioxins (PCDDs), which accounted for 95.76 percent of the total PCDD/Fs, 2,3,4,7,8-P5CDF (56.00%), 2,3,7,8-T4CDF (9.20%), 1,2,3,6,7,8-H6CDF (8.80%) and 1,2,3,7,8-P5CDF (8.00%) were the main contributing monomers. The findings of the assessment on exposure risk indicate that there is a respiratory risk to oil-based drill cuttings dioxins for adults and children exceeded the World Health Organisation (WHO) acceptable daily intake (ADI) (1-4 pgTEQ/kg/d). Finally, three aspects of solid waste pre-treatment prior to incineration, the incineration process and post incineration were used to reduce the environmental and human health risks from dioxins.

Selective recycling of lithium from spent LiNixCoyMn1-x-yO2 cathode via constructing a synergistic leaching environment.

The global response to lithium scarcity is overstretched, and it is imperative to explore a green process to sustainably and selectively recover lithium from spent lithium-ion battery (LIB) cathodes. This work investigates the distinct leaching behaviors between lithium and transition metals in pure formic acid and the auxiliary effect of acetic acid as a solvent in the leaching reaction. A formic acid-acetic acid (FA-AA) synergistic system was constructed to selectively recycle 96.81% of lithium from spent LIB cathodes by regulating the conditions of the reaction environment to inhibit the leaching of non-target metals. Meanwhile, the transition metals generate carboxylate precipitates enriched in the leaching residue. The inhibition mechanism of manganese leaching by acetic acid and the leaching behavior of nickel or cobalt being precipitated after release was revealed by characterizations such as XPS, SEM, and FTIR. After the reaction, 90.50% of the acid can be recycled by distillation, and small amounts of the residual Li-containing concentrated solution are converted to battery-grade lithium carbonate by roasting and washing (91.62% recovery rate). This recycling process possesses four significant advantages: i) no additional chemicals are required, ii) the lithium sinking step is eliminated, iii) no waste liquid is discharged, and iv) there is the potential for profitability. Overall, this study provides a novel approach to the waste management technology of lithium batteries and sustainable recycling of lithium resources.

Rapid extraction of valuable metals from spent LiNixCoyMn1-x-yO2 cathodes based on synergistic effects between organic acids.

The slow rate of organic acid leaching is the main factor hindering the ecological recycling of spent lithium-ion battery (LIB) cathode materials. Here, a mixed green reagent system of ascorbic acid and acetic acid is proposed to leach valuable metal ions from the spent LIBs cathode materials rapidly. In 10 min, 94.93% Li, 95.09% Ni, 97.62% Co, and 96.98% Mn were leached, according to the optimization results. Kinetic studies and material characterization technologies like XRD, SEM, XPS, UV-vis, and FTIR show that the "diffusion" and "stratification" effects of acetic acid contribute to the dual-function leaching agent ascorbic acid quickly extract metal ions from spent LiNi0.5Co0.3Mn0.2O2 (NCM532) materials at a mild temperature. In addition, the density-functional theory (DFT) calculations of spent NCM532 structural surfaces and leaching agents show that the fast leaching of valuable metal ions is due to the synergy between ascorbic acid and acetic acid. These results provided an approachable thinking for developing advanced and environmentally friendly strategies for recycling spent LIB cathode materials.

Human carcinogenic risk analysis and utilization of shale gas water-based drilling cuttings in road materials.

Water-based drilling cuttings (WDC) generated during shale gas development will endanger human health and ecological security. The modern analytical techniques are used to analyze the organic pollutants in WDC, and the human health and ecological security risks of harmful pollutants in WDC under specific scenarios are evaluated. The results showed that the content of organic pollutants in WDC was evaluated by human health and safety risk assessment. The comprehensive carcinogenic risks of all exposure pathways of single pollutant benzo(a)anthracene, benzo(a)pyrene, benzo(k)fluoranthene, and indeno(1,2,3-cd)pyrene were acceptable. However, the cumulative carcinogenic risk of exposure to dibenzo(a,h)anthracene particles via skin exposure was not acceptable. It was considered that only dibenzo(a,h)anthracene had carcinogenic effect, and the risk control limit of dibenzo(a,h)anthracene in WDC was 1.8700 mg/kg by calculation. As well as, the "WDC-cement" gel composite structure was deeply analyzed, and the physical and chemical properties and mechanism of organic pollutants in cement solidified WDC were analyzed, which provided theoretical support for the study of WDC pavement cushion formula. Based on the above conclusions and combined with the actual site, by studying and adjusting the formula of WDC pavement cushion, the WDC pavement cushion was finally designed by 6% cement + 50% WDC + 44% crushed stone. The 7d unconfined compressive strength met the requirements of the Chinese standard "Technical Guidelines for Construction of Highway Roadbases" (JTG/T F20-2015). Also, the process route of WDC as road cushion product was sampled and analyzed. In addition, the leaching concentration of main pollutants all met the relevant standards of China. Therefore, this study can provide a favorable way for the efficient, safe, and environmentally friendly utilization of WDC, and ensure the ecological environment safety and human health safety of WDC in resource utilization.

Highly Efficient Inherent Linearly Polarized Electroluminescence from Small-Molecule Organic Single Crystals.

Small-molecule organic single crystals (SCs) with an inherent in-plane anisotropic nature enable direct linearly polarized light emission without the need for spatially separated polarizers and complex optical structures. However, the device performance is severely restricted by the starvation of appropriate SC emitters and the difficulty in the construction of efficient SC electroluminescence (EL) devices, leading to a low external quantum efficiency (EQE) of usually smaller than 1.5%. Here, highly efficient inherent linearly polarized light-emitting diodes (LP-LEDs) are demonstrated by exploiting 2,6-diphenylanthracene (DPA) SCs as intrinsically polarized emitters. The LP-LEDs exhibit a 2.5-fold enhanced maximum EQE of 3.38%, which approaches the theoretical limit for the DPA SC-based EL device and is the highest among organic SC-based LEDs reported thus far. More importantly, a high degree of polarization (DOP) up to 0.74 is achieved for the intrinsically polarized EL emission of the DPA SC-based LP-LEDs. By leveraging the highly efficient LP-LED, an interchip polarized optical communication system consisting of organic SCs is demonstrated for the first time. This work creates a solid foundation for the exploitation of a vast new library of small-molecule organic SCs for LP-LEDs and carries broad implications for polarized optics and relevant optoelectronic devices.

Femoral Neck System vs. four cannulated screws in the treatment of Pauwels III femoral neck fracture.

OBJECTIVE: To compare the clinical efficacy of the Femoral Neck System (FNS) vs. four cannulated screws in Pauwels III femoral neck fractures. METHODS: This retrospective study included patients with newly occurred type Pauwels III femoral neck fracture treated at author' Hospital of between January 2017 and February 2021. The patients received FNS (n = 27) or four cannulated screws (control group, n = 31). The operation time, blood loss, fracture healing time, incidence of complications (such as short femoral neck, necrosis of femoral head, nonunion of fracture, and failure of internal fixation withdrawal), and hip Harris score at the last follow-up were analyzed. RESULTS: The operation time, blood loss, and fracture healing time were not significantly different between the two groups (all P > 0.05). In the FNS group, three and one patients were with femoral neck shortening and femoral head necrosis, respectively, while no fracture nonunion or failure of internal fixation withdrawal occurred. In the control group, seven, two, one, and two patients were with femoral neck shortening, femoral head necrosis, nonunion, and internal fixation failure, respectively. The cumulative complication incidence was 14.8% and 38.7% in the FNS and control groups (P = 0.042). The excellent and good rates of the hip Harris score at the last follow-up were 92.6% and 71.0% in the FNS and control groups, respectively (P = 0.036). CONCLUSION: The study suggested that the clinical efficacy of FNS was better than internal fixation using four cannulated screws in treating Pauwels III type femoral neck fracture.

Characteristic pollutants risk assessment of modified manganese residue utilization in sintered product.

The resource disposal of electrolytic manganese residue can effectively solve the problem of environmental pollution caused by it, among which the problem of heavy metal pollution is the most prominent. In this study, a new type of eco-friendly brick mixed with electrolytic manganese residue was designed. The influence of the content of electrolytic manganese residue on its macroscopic properties, microscopic properties, and leaching characteristics was analyzed by test methods such as compressive strength test, radioactivity test, XRF, XRD, FTIR, and ICP test of bricks. The results showed that the manganese content in the EMR leachate was 8120 mg/L, which exceeded the Chinese standard. The leaching experiment of ordinary aqueous solution of sintered bricks mixed with 20% EMR showed that the content of heavy metals was far lower than the Chinese national standard. There was no non-carcinogenic risk of heavy metals in the strong acid leaching solution of sintered bricks mixed with 20% EMR. Only the carcinogenic risk values of Cr for adults and children were 4.21 × 10-4 and 9.82 × 10-4 respectively, both exceeding the USEPA limit, but the application scene of sintered bricks was difficult to achieve strong acidity, so it was judged that it had no carcinogenic risk to the human body. Characteristic heavy metals such as Mn, Cr, and As existed stably in sintered bricks through substitution and encapsulation. In addition, the compressive strength and radioactivity of EMR sintered bricks met the requirements of the Chinese national standard "Fired Ordinary Bricks." This product can be used as national standard MU20 grade brick. This study provided an efficient method for the safe and environmentally friendly disposal of EMR in a sustainable control system.

[Clinical analysis of extended PFNA combined with MIPPO plate for reconstruction of lateral wall in treatment of AO-A3.3 intertrochanteric fracture].

OBJECTIVE: To compare the clinical efficacy of lengthened proximal femoral nail anti-rotation(PFNA) combined with minimally invasive percutaneous plate osteosynthesis(MIPPO) and common PFNA in the treatment of AO-A3.3 intertrochanteric fracture. METHODS: The clinical data of 58 patients with AO-A3.3 intertrochanteric fracture treated from January 2015 to April 2020 were retrospectively analyzed. Among them, 27 patients were treated with extended PFNA + MIPPO plate to reconstruct the lateral wall (group A), and 31 patients were treated with closed reduction and PFNA fixation (group B). The bleeding volume, operation time, femoral neck length and tip apex distance(TAD), fracture healing time and postoperative complications were observed and compared between two groups. Harris score was used to evaluate hip joint function 10 months after operation. RESULTS: All patients were followed up for 12 to 28 months. The incision healed well after operation. The bleeding volume and operation time of group A were significantly more than that of group B (P<0.05), and the fracture healing time of group A was significantly less than that of group B(P<0.05). There was no significant difference in the length of femoral neck between two groups at 2 days after operation(P>0.05). The length of femoral neck at 6 months after operation in each group was shorter than that at 2 days after operation(P<0.05), and the shortening of femoral neck at 6 months after operation in group B was significantly shorter than that in group A(P<0.05). There was no significant difference in TAD values between two groups at the same time point(P>0.05) at 2 days and 6 months after operation. There was no significant difference in TAD values between 2 days and 6 months after operation(P>0.05). The incidence of complications in group B was significantly higher than that in group A(P<0.05). The Harris scores of hip joint function in group A were higher than those in group B 10 months after operation (P<0.05). CONCLUSION: Compared with the treatment of AO-A3 femoral intertrochanteric fracture with closed reduction and PFNA fixation, the lengthened PFNA combined with MIPPO small plate for reconstruction and fixation of the lateral wall can promote the fracture healing, improve the patient's functional recovery, and significantly reduce the complications.

The pozzolanic activity of calcined oil-based drilling cuttings-aluminosilicate composites.

In order to reduce the environmental impact of shale gas production and towards the attenuation of artificial pozzolanic materials production cost, new oil-based drilling cuttings (OBDCs) pozzolanic materials have been introduced. After calcination, the chemical composition and the pozzolanic activity of oil-based drilling cuttings residue (OBDCRs) were investigated. The combination of X-ray diffraction (XRD), thermogravimetric analysis (TG), and Fourier transform infrared (FTIR) techniques shed light on impacts of pretreatment, calcination temperature, and Ba2+ on minerals' structure and pozzolanic activity. The results showed that, after high temperature calcination, the components of Si or Al in the OBDCRs particle surface and structure were activated and recombined to produce corresponding activity. Ba2+ could promote the pozzolanic activity of OBDCRs. The 28-day-compressive strength of OBDCRs was bigger than 31.33Mpa, and the compression strength ratios of cement mortar were bigger than 65%. Therefore, the pozzolanic reactivity of the treated OBDCs was competitive with that of conventional shale, which indicates that the heat treatment of OBDCs produces a cement substitute without any secondary pollution.

Characteristic pollutant purification analysis of modified phosphogypsum comprehensive utilization.

The waste product phosphogypsum (PG) is produced in phosphoric acid production processes. Its storage requires large amounts of land resources and poses serious environmental risks. In this work, detailed experimental research was carried out to investigate the potential reuse of PG after calcination modification as a novel building material for cast-in-place concrete products. The calcination modification mechanism was studied, and the environmental risk assessment of modified PG was presented. The results showed that the calcination modification includes crystal phase transformation, removal of impurities, and modifying the pH value. The calcination was carried out at 280 °C for 5 h, where the resulting product was a pH value of 7.1, and the soluble fluorine and phosphorus removal rates reached up to 69.2% and 71.2%, respectively. These removal rates met the requirements of the China national standard Phosphogypsum (GB/T 23456-2018). To ensure the environmental safety, ecological risk assessment methods for determining the leaching toxicity of the modified PG were employed. The toxicity of Ba and P elements in the modified PG products was assessed, as well as the leaching toxicity concentrations of all particular heavy metals, which were found well below the limits set by the national standards. All the results presented strongly suggest that the 280 °C modified PG presented here has excellent application potential as a raw component in building materials.

High-Luminance Microsized CH3NH3PbBr3 Single-Crystal-Based Light-Emitting Diodes via a Facile Liquid-Insulator Bridging Route.

Micro-/nanosized organic-inorganic hybrid perovskite single crystals (SCs) with appropriate thickness and high crystallinity are promising candidates for high-performance electroluminescent (EL) devices. However, their small lateral size poses a great challenge for efficient device construction and performance optimization, causing perovskite SC-based light-emitting diodes (PSC-LEDs) to demonstrate poor EL performance. Here, we develop a facile liquid-insulator bridging (LIB) strategy to fabricate high-luminance PSC-LEDs based on single-crystalline CH3NH3PbBr3 microflakes. By introducing a blade-coated poly(methyl methacrylate) (PMMA) insulating layer to effectively overcome the problems of leakage current and possible short circuits between electrodes, we achieve the reliable fabrication of PSC-LEDs. The LIB method also allows us to systematically boost the device performance through crystal growth regulation and device architecture optimization. Consequently, we realize the best CH3NH3PbBr3 microflake-based PSC-LED with an ultrahigh luminance of 136100 cd m-2 and a half-lifetime of 88.2 min at an initial luminance of ∼1100 cd m-2, which is among the highest for organic-inorganic hybrid perovskite LEDs reported to date. Moreover, we observe the strong polarized edge emission of the microflake-based PSC-LEDs with a high degree of polarization up to 0.69. Our work offers a viable approach for the development of high-performance perovskite SC-based EL devices.

Property of concrete made of recycled shale gas drilling cuttings.

Exploration and development of shale gas generate a lot of water-based drilling cuttings (WDC), which can then be used in concrete engineering. This work studied mix ratio optimization, mechanical properties, leaching characteristics and the microstructure of the WDC concrete. The results showed that the pH and COD values of these WDC were slightly above 9.0 and 60, respectively. All other indices satisfied the first grade standard of Chinese standard GB8978. On the other hand, a moderate amount of WDC can be improved concrete properties, especially its workability and compressive strength. When the water-binder ratio is 0.52 and the sand ratio is 41%, we can obtain C25 strength grade and 130 ~ 140 mm slump grade concrete by adding high efficiency water reducing agent and fly ash. XRD and SEM analysis showed that the silica and aluminum oxide in WDC reacted with calcium hydroxide to form secondary hydration products: C-S-H gel and ettringite, which are conducive to the formation of concrete strength and solidified the heavy metals and other contaminants. EDX analysis found it is known that the hydration products in WDC concrete can bind metal elements well. The environmental leaching test shows that the recycled WDC added to concrete products as aggregate and admixture is very environmentally friendly and sustainable.

Particular pollutants, physical properties, and environmental performance of porous ceramsite materials containing oil-based drilling cuttings residues.

The mineral compositions of oil-based drilling cutting residues (ODCRs) were similar to that of clay, which could be used as raw materials for ceramsite. In this study, the maximum addition of ODCRs and the optimum calcination conditions were studied by single factor experiment. The microstructure, phase composition, and element distribution of ceramsite were studied by means of SEM, XRD and EDS. The ceramsite, with a 40% ODCRs content, was calcined at 1000 °C for 2 h. After cooling down, the ceramsite had good physical properties, including low density, low water absorption, and high compressive strength. The bulk density was 850-970 kg/m3, the water absorption was 2.1-10%, and the cylinder compressive strength was 6-11.8 MPa. And most of the heavy metals in ODCRs were effectively solidified. The organic toxic substances were completely burned. The leaching amount of harmful elements met the requirements of Chinese standards. The ceramsite would avoid secondary pollution to the environment. So the ceramsite made from ODCRs can not only improve the processing speed of ODCRs, but also be used as building materials, greening materials, industrial filter materials, etc., and increase its environmental and social benefits.

Three-Dimensional Finite Element Analysis and Biomechanical Analysis of Midfoot von Mises Stress Levels in Flatfoot, Clubfoot, and Lisfranc Joint Injury.

BACKGROUND Midfoot deformity and injury can affect the internal pressure distribution of the foot. This study aimed to use 3D finite element and biomechanical analyses of midfoot von Mises stress levels in flatfoot, clubfoot, and Lisfranc joint injury. MATERIAL AND METHODS Normal feet, flatfeet, clubfeet (30 individuals each), and Lisfranc injuries (50 individuals) were reconstructed by CT, and 3D finite element models were established by ABAQUS. Spring element was used to simulate the plantar fascia and ligaments and set hyperelastic coefficients in encapsulated bone and ligaments. The stance phase was simulated by applying 350 N on the top of the talus. The von Mises stress of the feet and ankle was visualized and analyzed. RESULTS The von Mises stress on healthy feet was higher in the lateral metatarsal and ankle bones than in the medial metatarsal bone. Among the flatfoot group, the stress on the metatarsals, talus, and navicular bones was significantly increased compared with that on healthy feet. Among patients with clubfeet, stress was mainly concentrated on the talus, and stress on the lateral metatarsal and navicular bones was significantly lower. The von Mises stress on the fractured bone was decreased, and the stress on the bone adjacent to the fractured bone was higher in Lisfranc injury. During bone dislocation alone or fracture accompanied by dislocation, the von Mises stress of the dislocated bone tended to be constant or increased. CONCLUSIONS Prediction of von Mises stress distribution may be used clinically to evaluate the effects of deformity and injury on changes in structure and internal pressure distribution on the midfoot.

Ultrabroadband and High-Detectivity Photodetector Based on WS2/Ge Heterojunction through Defect Engineering and Interface Passivation.

Broadband photodetectors are of great importance for numerous optoelectronic applications. Two-dimensional (2D) tungsten disulfide (WS2), an important family member of transition-metal dichalcogenides (TMDs), has shown great potential for high-sensitivity photodetection due to its extraordinary properties. However, the inherent large bandgap of WS2 and the strong interface recombination impede the actualization of high-sensitivity broadband photodetectors. Here, we demonstrate the fabrication of an ultrabroadband WS2/Ge heterojunction photodetector through defect engineering and interface passivation. Thanks to the narrowed bandgap of WS2 induced by the vacancy defects, the effective surface modification with an ultrathin AlOx layer, and the well-designed vertical n-n heterojunction structure, the WS2/AlOx/Ge photodetector exhibits an excellent device performance in terms of a high responsivity of 634.5 mA/W, a large specific detectivity up to 4.3 × 1011 Jones, and an ultrafast response speed. Significantly, the device possesses an ultrawide spectral response spanning from deep ultraviolet (200 nm) to mid-wave infrared (MWIR) of 4.6 µm, along with a superior MWIR imaging capability at room temperature. The detection range has surpassed the WS2-based photodetectors in previous reports and is among the broadest for TMD-based photodetectors. Our work provides a strategy for the fabrication of high-performance ultrabroadband photodetectors based on 2D TMD materials.

Risk assessment of human exposure to heavy metals, polycyclic aromatic hydrocarbons, and radionuclides in oil-based drilling cutting residues used for roadbed materials in Chongqing, China.

Oil-based drilling cutting residues (OBDCRs) contain many kinds of carcinogenic contaminants, such as heavy metal elements, polycyclic aromatic hydrocarbons (PAHs), and natural radioactive materials (NORMs), which are great risks for the environment and human health. This study investigated the chemical composition, the radioactive strength, the heavy metal contents, and the org matter contents in OBDCRs and estimated the health risks due to exposure to heavy metals, PAHs, and radionuclides in OBDCRs used for roadbed materials. From the measurements, it was found that the content values of benzopyrene (a), diphenylanthracene (a, h), and petroleum hydrocarbons exceeded the standard limit. The content values of Cu, Zn, As, and Ni were higher than 50% of the standard limit. If OBDCRs were directly used to make roadbed materials, the total carcinogenic risk values (CRn) of As, benzoanthracene (a), benzopyrene (a), and dibenzoanthracene (a, h) were all higher than 10-6. The average absorbed dose rate was higher than 80 nGy/h. There were greater risks of carcinogenic environment and potential harms to human health. To reduce the health risks, it is necessary to consider the strategy of the utilization of OBDCRs, the working time, and the service life of the recycled OBDCRs and establish a legal standard and liability for the utilization of OBDCRs as solid waste resources.

Resource recycling sustainability assessment in ready-mixed concrete manufactured on energy consumption and environmental safety in China.

With the rapid development of construction industry, consumption of ready-mixed concrete has increased rapidly in China. As a kind of green building material and waste comprehensive utilization product, industrial solid waste-based ready-mixed concrete have better performance in terms of resource conservation and durability. However, some typical issues are associated with industrial solid waste resource recycling in ready-mixed concrete production process such as energy and material consumption, as well as leaching pollutant emissions. So, a "life cycle assessment" of the particular elements has been carried out, determining the resources consumption of all the processes of the ready-mixed concrete production. Through preparation of several different strength grades of concrete, the embodied energy and resources consumption indicator are quantitative evaluation. In addition, the environmental safety assessment was also proposed. The results show a certain linear relationship of concrete with various strength grade and its resources consumption, the higher strength grade, the more resources consumption potentials in the production of concrete. In this case, the linear correlation coefficient R2=0.98313 between them, and the equivalent coefficient's order of the main resources, is as follows: the first is oil, then natural gas, iron ore, limestone, gypsum, and fly ash, and the last is coal. The more preceding shows more scarcity. Meanwhile, the general leaching of heavy metals Cu, Zn, Ni, Cr, Pb, Cd, and Ba of solid waste-based C20 concrete were also checked out. So, to further ensure the environmental safety, the potential ecological risk method was adopted to assess the heavy metal security and solid waste resource utilization.

Mechanism study on co-processing of water-based drilling cuttings and phosphogypsum in non-autoclaved aerated concrete.

The feasibility of coordinated use of water-based drilling cuttings (WDC), fly ash, and phosphogypsum (PG) as raw materials for the preparation of WDC non-autoclaved aerated concrete (WNAAC) was evaluated by laboratory experiment. The results showed that the pozzolanic reaction of the multi-component cementitious system containing 40% (in mass) of WDC is significantly promoted. Newly formed C-S-H gel and ettringite with the uniform distribution of fibrous and flake-like shape occur, presenting a denser and interlock microstructure. In addition, after cured by steam at 80 °C for 24 h, the mechanical property and unit weight of the WNAAC prepared with 40% WDC fully meet the B06, A3.5 grade of China state standard (GB/T11968-2006). Environmental performance tests confirm that the WNAAC prepared with 40% WDC does not create any secondary contamination.

An effective treatment method for phosphogypsum.

Phosphogypsum (PG) accumulation occupies huge amounts of land resources and results in serious environmental risks. A new recycling product, the phosphogypsum embedded filler (PGEF) made with calcination-modified phosphogypsum, was developed. The preparation process, hydration mechanism of PG, basic physical performances, environmental safety, engineering application, and cost analysis of the PGEF were studied. The results showed that the stress performance and thermal insulation property of the products were satisfied. Environmental performance tests established their findings that the application of PGEF prepared with calcination-modified PG does not cause any secondary contamination. In addition, the cost of PGEF is far lesser than that of the same volume of reinforced concrete. PGEF prepared with calcination-modified PG has shown a perfect application in cast-in situ concrete hollow floor structure.