A Critical Review of the Enhanced Recovery of Rare Earth Elements from Phosphogypsum.

The increasing demand for rare earth elements (REEs), especially from new and innovative technology, has strained their supply, which makes the exploration of new REE sources necessary, for example, the recovery of REEs from phsophogypsum (PG). PG is a byproduct during the wet production of phosphoric acid, which is an attractive secondary resource for REEs due to a large amount of REEs locked in them. In most cases, REEs contained in PG are mainly encapsulated in the gypsum crystal, leading to a low leaching efficiency. Therefore, it is particularly important to use various methods to enhance the leaching of REEs from PG. In this review, we summarized and classified various enhanced leaching methods for the recovery of REEs from PG, and the advantages and disadvantages of different methods were compared. A joint method of recrystallization and RIL may be a promising enhanced leaching approach for the recovery of REEs from PG. Recrystallization could achieve both the complete REE release and simultaneous preparation of industrial materials with high value added, such as high-strength α-hemihydrate gypsum by phase transformation of PG, and the RIL technology could adsorb the releasing REEs and realize their efficient extraction. Such a combination appears to show significant advantages because of high REE recovery, as well as high value-added product preparation at low cost.

Adsorption Mechanism of 4-Amino-5-mercapto-1,2,4-triazole as Flotation Reagent on Chalcopyrite.

A novel compound 4-amino-5-mercapto-1,2,4-triazole was first synthesized, and its selective adsorption mechanism on the surface of chalcopyrite was comprehensively investigated using UV-vis spectra, zeta-potential, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy measurements (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and first principles calculations. The experimental and computational results consistently demonstrated that AMT would chemisorb onto the chalcopyrite surface by the formation of a five-membered chelate ring. The first principles periodic calculations further indicated that AMT would prefer to adsorb onto Cu rather than Fe due to the more negative adsorption energy of AMT on Cu in the chalcopyrite (001) surface, which was further confirmed by the coordination reaction energies of AMT-Cu and AMT-Fe based on the simplified cluster models at a higher accuracy level (UB3LYP/Def2-TZVP). The bench-scale results indicated that the selective index improved significantly when using AMT as a chalcopyrite depressant in Cu-Mo flotation separation.

[Clinical significance of serum telomerase mRNA in patients with prostate cancer].

OBJECTIVE: To explore the clinical significance of detecting serum mRNA of telomerase in the diagnosis of prostate cancer. METHODS: Serum samples were collected from 29 patients with prostate cancer and 29 age-matched patients with cardiovascular or metabolic disease as non-tumor controls. Sera samples from 15 healthy age-matched subjects were used as healthy control. Detection of serum telomerase mRNA was performed with real-time reverse transcriptase quantitative polymerase chain reaction (PCR). RESULTS: Serum telomerase mRNA was detectable in 89.7% (26/29) patients with prostate cancer, but almost undetectable in non-tumor (6.9%, 2/29) and healthy control groups(1/14). CONCLUSION: Using real-time PCR for detecting serum telomerase mRNA may be an auxiliary method for diagnosing and monitoring of prostate cancer.

[Expression and clinical significance of transcription factors in prostate cancer].

OBJECTIVE: To explore the roles of various transcription factors in the occurrence and development of prostate cancer. METHODS: A total of 139 specimens with prostate cancer (PCa) and 83 specimens with benign prostatic hyperplasia (BPH) from hospitalized patients at our hospital from 2008 to 2011 were enrolled. The mRNA expressions of c-Myc, Klf4, Nanog, Oct4A and Sox2 were determined by quantitative real-time polymerase chain reaction (PCR) and the expressions of Klf4 isoforms by conventional PCR. Immunohistochemical method was used for the detection of Klf4 protein via tissue microarray in 404 prostate samples. RESULTS: No significant difference existed in the expressions of Nanog, Oct4A and Sox2 genes between BPH and PCa samples. And the expressions of c-Myc and Klf4 genes were significantly higher in PCa than those in BPH specimens. Immunohistochemical results showed that Klf4 protein could be detected in a large majority of epithelial prostatic cells irrespective of malignant transformation. However, it was predominantly located cytoplasmically in PCa tissues and remained consistent with the expression of a differentially spliced Klf4α isoform. CONCLUSION: Klf4 is highly expressed in both BPH and PCa tissues. But in malignant cells, a specific gene product Klf4α is predominantly detectable in cytoplasm. The positioning of Klf4 protein may have an important relationship with its role in the tumorigenic process.

The Impurity Removal and Comprehensive Utilization of Phosphogypsum: A Review.

Phosphogypsum (PG), a byproduct during the phosphoric acid production process, also known as the wet process, contains complex and diverse impurities, resulting in low utilization and considerable accumulation. This leads to a massive waste of land resources and a series of environmental pollution problems. Given the current urgent ecological and environmental situation, developing impurity removal processes with low energy consumption and high efficiency, exploring valuable resource recovery, preparing high value-added PG products, and broadening the comprehensive utilization ways of PG are significant strategies to promote the sustainable consumption of PG and sustainable development of the phosphorus chemical industry. This review comprehensively summarizes the advantages and disadvantages of existing PG impurity removal and utilization technologies and probes into the future development direction, which provides references and ideas for subsequent PG research.

Synergy Effect of Nano-Organic Palygorskite on the Properties of Star-Shaped SBS-Modified Asphalt.

With the rapid development of economic construction, styrene-butadiene-styrene (SBS)-modified asphalt is being more and more widely used in highway engineering, but there are still many deficiencies in the process of its use. In order to further improve its performance for use, nano-organic palygorskite (A-Pal) and star-shaped SBS were compounded to obtain modified asphalt in this study. The high-temperature stability of SBS-modified asphalt was enhanced after incorporation with A-Pal for the high-temperature stability test by a dynamic shear rheometer. The A-Pal should improve the surface free energy and adhesion of SBS-modified asphalt by the water stability test analysis. The aging test shows that A-Pal can reduce the thermal oxygen decomposition of SBS and improve the anti-aging performance and the fatigue resistance of SBS-modified asphalt. A-Pal has a certain improvement effect on the low temperature performance of SBS-modified asphalt as shown by a low temperature crack resistance test. A-Pal-compounded SBS-modified asphalt features good storage stability in normal temperatures with the lowest critical compatibility temperature.

Efficient utilisation of flue gas desulfurization gypsum as a potential material for fluoride removal.

This study introduces the use of a waste by-product from wet limestone flue gas desulfurization as a potential material for fluoride removal. Systematic laboratory-scale experiments were tested to identify the fluoride removal performance and determine the underlying mechanism. Flue gas desulfurization (FGD) gypsum removes 93.31% of fluoride from 109 mg/L to 7.3 mg/L. Fluoride can be efficiently removed at the optimum pH range of 5-11. Kinetics analysis indicates that the theoretical fluoride capacity at 1 g/L FGD gypsum is 96.9 mg/g. Equilibrium speciation analysis indicates that the decrease of system pH to lower than 5 is unsuitable for the formation of calcium fluoride, and the increase of system pH to higher than 11 opposes calcium release from FGD gypsum. Thermodynamic analysis confirms the feasibility of converting calcium sulphate into calcium fluoride at pH > 5. FGD gypsum and precipitates were characterized to describe their surface morphology, elemental composition and crystalline phase. Results indicate that FGD gypsum removes fluoride through the combination of calcium with fluoride to generate calcium fluoride.

Preparation of α-CaSO4·½H2O with tunable morphology from flue gas desulphurization gypsum using malic acid as modifier: A theoretical and experimental study.

Huge amount of flue gas desulphurization (FGD) gypsum not only occupies the farmland but also causes severe pollution to the surrounding environment. The most effective way to achieve a high-value utilization of FGD gypsum is to prepare short columnar α-calcium sulfate hemihydrate (α-HH) since short columnar crystals show better mechanical strength than needle-like ones. Here, malic acid, a prolific, inexpensive and environment-friendly modifier was explored for the first time to effectively tune the crystal morphology of α-HH prepared from FGD gypsum in glycerol-water-NaCl solutions. When the concentration of malic acid reached 18.54 × 10-4 mol/kg, α-HH crystals with an average aspect (length-to-diameter) ratio of 1.9 (compared to 29.4 in the absence of malic acid) were prepared. The selective complexation of malic acid with Ca active sites on different α-HH crystal planes played a dominant role in the α-HH crystal morphology transformation, which was then explained by the surface broken bonds theory for the first time. The broken bond number per active Ca atom (Nbper Ca) and broken bond density of Ca atoms (DbCa) on the (2 0 4) end plane were larger than those on the (0 2 0) or (2 0 0) side planes. Therefore, the (2 0 4) end plane was more reactive with organics, resulting in the preferential adsorption of malic acid on the end planes, which reduced the specific surface energy of (2 0 4) and led to an increased exposure of this plane and a decreased exposure of (0 2 0) or (2 0 0) side planes in the final α-HH crystals. Consequently, using malic acid as modifier, the α-HH crystal gradually transformed from a needle-like shape to a short columnar one. This work provided important insights into and perspectives for the selection of crystal modifiers and explanation of the mechanism during the preparation of calcium-containing crystals with controllable morphology.

Selective adsorption of tannic acid on calcite and implications for separation of fluorite minerals.

Selective adsorption of tannic acid (TA) on calcite surfaces and the implications of this process for the separation of fluorite ore were studied by microflotation tests, surface adsorption experiments, zeta potential measurements, UV-vis analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The microflotation tests indicated that TA, when added before sodium oleate (NaOl), could selectively depress calcite from fluorite at pH 7. Surface adsorption experiments revealed that TA hinders the interaction of NaOl with calcite. The zeta potential of calcite became more negative with TA than with NaOl. However, the characteristic features of TA adsorption were not observed on fluorite, suggesting that the dominant adsorption sites are dissimilar on the fluorite and calcite surfaces in the pulp. UV-vis spectroscopy, XPS, and solution chemistry analysis were utilized to obtain a better understanding of the mechanism for selective adsorption of TA as well as the key factors determined by the Ca2+ and Ca(OH)+ components on the mineral surfaces. A possible adsorption mechanism along with an adsorption mode is proposed for the surface interaction between TA and calcite.

A facile method of transforming FGD gypsum to α-CaSO4·0.5H2O whiskers with cetyltrimethylammonium bromide (CTAB) and KCl in glycerol-water solution.

A facile method to transform flue gas desulfurization gypsum (FGD gypsum) to α- calcium sulfate hemihydrate (α-HH) whiskers with high aspect ratios mediated by cetyltrimethylammonium bromide (CTAB) and KCl in glycerol-water solutions was studied. Addition of KCl facilitated the dissolution of calcium sulfate dihydrate (DH) and created a much higher supersaturation, which could come into being a larger driving force for the phase transformation from DH to α-HH. CTAB as the crystal modifier can significantly promoted 1-D growth of α-HH whiskers along the c axis and the presence of 0.25% CTAB (by weight of FGD gypsum) resulted in the increase of the average aspect ratio of α-HH whiskers from 28.9 to 188.4, which might be attributed to the preferential adsorption of C16H33(CH3)3N+ on the negative side facets of α-HH crystal.

Inhibitory effect and mechanism of AMPKα over-expression on proliferation, invasion and EMT of bladder cancerT24 cells / 中国肿瘤生物治疗杂志

@# Objective: To investigate the effect and mechanism of AMP-activated protein kinase α (AMPKα) over-expression on proliferation, migration, invasion and epithelial mesenchymal transition (EMT) of bladder cancer T24 cells. Methods: A bladder cancer T24 cells over-expressing AMPKα was established and divided into T24 group, pc-DNA group and pc-AMPKα group according to different plasmid transfection. Western blotting was used to verify the over-expression ofAMPKα and detect the expressions of EMT-related proteins and EMT pathway-related molecules. Hoechst staining was used to detect apoptosis of transfected T24 cells. CCK8 assay was used to detect cell proliferation. Cell scratch test was used to detect cell migration. Transwell assay was used to detect cell invasion. Results: The bladder cancer cell line T24 over-expressingAMPKα was successfully constructed. Compared with the T24 group and the pc-DNA group, the level of E-cadherin in the pc-AMPKα group was significantly increased (P<0.01) while the levels of Vimentin and N-cadherin were significantly decreased (all P<0.01), and the activities of P38 and STAT3 which related to EMT pathway were significantly inhibited (all P<0.01); cell proliferation, migration and invasion were significantly decreased while cell apoptosis was obviously enhanced (all P<0.01). Conclusion: Over-expression of AMPKα can inhibit the activity of EMT pathway-related molecules, which leads to obvious apoptosis, limited proliferation, reduced invasion and migration of bladder cancer T24 cells, and accompanied by the reversal of EMT.