High performance polymeric aluminum silicate sulfate (PASS) flocculant from abandoned molecular sieve.

PASS is an innovative inorganic polymer flocculant (IPF), which possesses the advantages of a polysilicate/aluminum sulfate-based flocculant. Recently, solid wastes rich in Si and Al, such as kaolinite, rice husks, and abandoned molecular sieves (AMS) have been recognized as promising raw materials for the synthesis of flocculants. The present study involved the synthesis of PASS flocculant derived from AMS. The efficacy of the as-prepared PASS was evaluated through the flocculation of wastewater containing ultramarine blue (UB) pigment. The optimal flocculation performance of PASS was observed at a Si/Al molar ratio of 1.62 and a polymerization time of 9 h. Furthermore, we investigated the impact of PASS dosage, stirring/settling time, and pH on the flocculation process while also exploring potential mechanisms. The PASS flocculant prepared in this study exhibited superior performance compared to the commercially available polyaluminum sulfate (PAS). The results demonstrated the viability of preparing PASS flocculants from waste resources.

Nano-sized aggregate Ti3C2-TiO2 supported on the surface of Ag2NCN as a Z-scheme catalyst with enhanced visible light photocatalytic performance.

Exposing the photocatalyst's highly active facets and hybridizing the photocatalyst with suitable cocatalysts in the proper spot have been recognized as strong methods for high-performance photocatalysts. Herein, Ag2NCN/TiO2-Ti3C2 composites were synthesized by applying simple calcination and physically weak interaction deposition processes to obtain an excellent photocatalyst for Rhodamine B (Rh B) degradation when exposed to visible light. The findings from the experiments reveal that the Ag2NCN/TiO2-Ti3C2400 composite exhibited an outstanding photocatalytic rate in 80 min, with the highest Rh B degradation rate (k = 0.03889 min-1), which was 16 times higher than that of pure Ag2NCN (k = 0.00235 min-1) and 2.2 times higher than that of TiO2-Ti3C2400 (k = 0.01761 min-1). The results from the following factors: (i) the powerful interfacial contact created by the in situ formation of TiO2, and the superior electrical conductivity of Ti3C2 that makes carrier separation possible; (ii) TiO2 with electron-rich (101) facets are deposited on the surface of Ag2NCN, significantly reducing charge carrier recombination by trapping photoelectrons; (iii) a Z-type heterojunction is constructed between nanosize aggregate Ti3C2-TiO2 and Ag2NCN with non-metal Ti3C2 as the solid medium, improving the transfer and separation of photogenerated charges and inhibiting the recombination of electrons and holes. Additionally, the redox ability of the composite photocatalyst is enhanced. Furthermore, the analyses of active species showed that photogenerated superoxide radicals and holes were the principal active agents inside the photodegradation of Rh B. Moreover, the composite exhibited outstanding photo-stability.

Ag2NCN anchored on Ti3C2Tx MXene as a Schottky heterojunction: enhanced visible light photocatalytic efficiency of rhodamine B degradation.

The quick charge recombination of light-generated electrons and holes severely restricts the photocatalytic applications of single semiconductors. Here, a straightforward electrostatically driven self-assembly technique was used to construct an Ag2NCN/Ti3C2Tx Schottky heterojunction, which was then used to degrade Rhodamine B (RhB) in the illumination of visible light. The findings from the experiments revealed that as a cocatalyst, Ti3C2Tx significantly suppresses the recombination rate and broadens visible absorptivity to improve Ag2NCN photocatalytic efficiency. The optimized Ag2NCN/Ti3C2Tx (AT2) composite exhibited an outstanding photocatalytic rate in 96 min, with the highest RhB degradation rate (k = 0.029 min-1), which was around fifteen times that of pure Ag2NCN (k = 0.002 min-1). Furthermore, the trapping-agent experiment showed photogenerated superoxide radicals and holes were the principal active agents inside the photodegradation of RhB. Compared with Ag-based semiconductors, the composite exhibited outstanding photostability, highlighting its excellent potential for application in visible-light photocatalysis.

Multiaperture g-C3N4@SiO2 to activate peroxydisulfate via visible light for efficient Rhodamine B removal.

The sulfate radical-based advanced oxidation process (SR-AOPs) has been verified as a promising method to handle the persistent organic compounds in water using peroxydisulfate (PDS) as oxidant. A Fenton-like process was constructed and showed great potential to remove organic pollutants using visible-light-assisted PDS activation. The g-C3N4@SiO2 was synthesized via thermo-polymerization, and characterized using powder X-ray diffraction (XRD), scanning electron microscope equipped with an energy-dispersive X-ray (SEM-EDX), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) method, photoluminescence (PL), transient photocurrent, and electrochemical impedance. Photocatalytic performance was demonstrated using the removal rate of Rhodamine B (RhB), and 96.08% RhB was removed from the solution within 50 min (10 mg/L in 200 mL, g-C3N4@SiO2 = 0.25 g/L, pH = 6.3, PDS = 1 mmol/L). The free radical capture experiment proved that HO•, h+, [Formula: see text] and [Formula: see text] were generated and removed RhB. The cyclic stability of g-C3N4@SiO2 has also been studied, and the result shows no noticeable difference in the six cycles. The system of visible-light-assisted PDS activation might provide a novel strategy for wastewater treatment and must be an environment-friendly catalyst.

Effects of different dietary protein levels on intestinal aquaporins in weaned piglets.

This study was conducted to investigate the relationship between changes in intestinal aquaporins (AQPs) in piglets fed diets with different protein levels and nutritional diarrhoea in piglets. Briefly, 96 weaned piglets were randomly divided into four groups fed diets with crude protein (CP) levels of 18%, 20%, 22% and 24%. The small intestines and colons of the weaned piglets were collected, and several experiments were conducted. In the small intestine, AQP4 protein expression was higher in weaned piglets fed the higher-CP diets (22% and 24% CP) than in those fed the 20% CP diet except at 72 h (p < 0.01). At 72 h, the AQP4 protein expression in the small intestine was lower in the 18% group than in the other three groups (p < 0.01). Under 20% CP feeding, AQP2, AQP4 and AQP9 protein expression in the colons of piglets peaked at certain time points. The AQP2 and AQP4 mRNA levels in the colon and the AQP4 and AQP4 mRNA levels in the distal colon were approximately consistent with the protein expression levels. However, the AQP9 mRNA content in the colon was highest in the 18% group, and the AQP2 mRNA content in the distal colon was significantly higher in the 24% group than in the 20% group. AQP2 and AQP4 were expressed mainly around columnar cells in the upper part of the smooth colonic intestinal villi, and AQP9 was expressed mainly on columnar cells and goblet cells in the colonic mucosa. In conclusion, 20% CP is beneficial to the normal expression of AQP4 in the small intestine, AQP2, AQP4 and AQP9 in the colon of weaned piglets, which in turn maintains the balance of intestinal water absorption and secretion in piglets.

Photocatalysis coupled with adsorption of AC@Ni0.5Cu0.5Fe2O4 in peroxydisulfate assisted system efficiently enhance ciprofloxacin removal.

Nickle-copper ferrite (Ni0.5Cu0.5Fe2O4) supported on activated carbon (AC) (AC@Ni0.5Cu0.5Fe2O4) was synthesized and used as adsorbent, photocatalyst, and activator of peroxydisulfate (PDS) to realize the removal of ciprofloxacin (CIP). AC@Ni0.5Cu0.5Fe2O4 properties were characterized by scanning electron microscope equipped with energy-dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), N2 adsorption-desorption isotherm plot of Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), vibrating sample magnetometer (VSM). A rapid removal rate (94.30%) of CIP was achieved on AC@Ni0.5Cu0.5Fe2O4/PDS/UV system with the condition of catalyst dosage 0.30 g/L, initial pH 7.3, PDS addition 0.20 mM, CIP concentration 10 mg/L (200 mL), UV 28 W, in 30 min. Free radical quenching experiments indicate that reactive species of superoxide (·O2-), holes (h+), sulfate radicals (SO4-·) and hydroxyl radicals (·OH) were produced and all worked. The reusability test demonstrated that AC@Ni0.5Cu0.5Fe2O4 could be recycled five times with minimal performance reduction for the removal of CIP. The XRD and SEM of the after used AC@Ni0.5Cu0.5Fe2O4 did not change significantly, which further showed its stability and recyclability. This work might provide new insight into the application of AC@Ni0.5Cu0.5Fe2O4 in photocatalysis coupled with adsorption in peroxydisulfate assisted system and has high potential in CIP removal.

Migration and Transformation of Arsenic in Rice and Soil under Different Nitrogen Sources in Polymetallic Sulfide Mining Areas.

Nitrogen (N) fertilizer affects the migration and transformation of arsenic (As) in soil and rice. We conducted pot experiments and studied the effects of 0.1, 0.2, and 0.4 g∙kg−1 N levels of NH4Cl, (NH4)2SO4, and NH4NO3 fertilizers on the As bioavailability in the As-contaminated inter-rhizosphere soil and As accumulation in the rice organs. The results showed that the concentration of bioavailable As in the rice rhizosphere soil was significantly negatively correlated with pH under the 0.4 g∙kg−1 N level of each fertilizer. At the same N level, while the As concentration was maturity stage > tillering stage in rice stems and leaves treated with NH4Cl and (NH4)2SO4, it was the opposite in roots. This suggests that the transfer of As from roots to stems and leaves mainly occurs in the late stage of rice growth under the condition of only NH4+-N fertilizer applying. The As concentration in rice aboveground organ (grains and stems−leaves) decreased with the increasing N application under the same N fertilizer treatment condition during the mature stage. In addition, the As concentration in rice grains treated with (NH4)2SO4 was the lowest. This result indicated that SO42− and NH4+-N had a significant synergistic inhibition on the As accumulation in rice grains. It was concluded that appropriate (NH4)2SO4 levels for As-contaminated paddy soils with high sulfur (S) contents would obtain rice grains with inorganic As concentrations below 0.2 mg·kg−1.

Effects of dietary protein level on small intestinal morphology, occludin protein, and bacterial diversity in weaned piglets.

Due to the physiological characteristics of piglets, the morphological structure and function of the small intestinal mucosa change after weaning, which easily leads to diarrhea in piglets. The aim of this study was to investigate effects of crude protein (CP) levels on small intestinal morphology, occludin protein expression, and intestinal bacteria diversity in weaned piglets. Ninety-six weaned piglets (25 days of age) were randomly divided into four groups and fed diets containing 18%, 20%, 22%, and 24% protein. At 6, 24, 48, 72, and 96 h, changes in mucosal morphological structure, occludin mRNA, and protein expression and in the localization of occludin in jejunal and ileal tissues were evaluated. At 6, 24, and 72 h, changes in bacterial diversity and number of the ileal and colonic contents were analyzed. Results showed that structures of the jejunum and the ileum of piglets in the 20% CP group were intact. The expression of occludin mRNA and protein in the small intestine of piglets in the 20% CP group were significantly higher than those in the other groups. As the CP level increased, the number of pathogens, such as Clostridium difficile and Escherichia coli, in the intestine increased, while the number of beneficial bacteria, such as Lactobacillus, Bifidobacterium, and Roseburia, decreased. It is concluded that maintaining the CP level at 20% is beneficial to maintaining the small intestinal mucosal barrier and its absorption function, reducing the occurrence of diarrhea, and facilitating the growth and development of piglets.

Insight into the performance and mechanism of magnetic Ni0.5Cu0.5Fe2O4 in activating peroxydisulfate for ciprofloxacin degradation.

Magnetic nickel-copper ferrite (NixCuyFe2O4) nano-catalyst was synthesized by co-precipitation method, and it exhibited excellent ability for activating peroxydisulfate (PDS) in the degradation of ciprofloxacin (CIP). As-prepared Ni0.5Cu0.5Fe2O4 properties were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope equipped with an energy-dispersive X-ray (SEM-EDX), transmissions electron microscopy (TEM), N2 adsorption-desorption isotherm plot of Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), vibrating sample magnetometer (VSM). The maximum degradation efficiency is 80.2% by using 0.500 g/L of Ni0.5Cu0.5Fe2O4 for activating 5.00 mmol/L of PDS to degrade CIP (20.0 mg/L) at 25 ± 2 °C for 50 min (pH = 6.00). The presence of interfering ions Cl-, NO3-, and HCO3- inhibited the reaction by producing reactive species with low oxidation potential, inducing the degradation efficiency down to 60.0%, 58.1% and 21.5% respectively. Ni0.5Cu0.5Fe2O4 displayed great magnetic separation characteristic for the satisfactory magnetization; saturation value is ∼8.6 emu/g. The degradation efficiency of recycled samples has no significant difference after using three times, which is about 60%, indicating that Ni0.5Cu0.5Fe2O4 is a reusability catalyst in activating PDS for CIP degradation. This work might provide an efficient and promising approach to construct recyclable magnetic materials that can be used for wastewater treatment.

Enhanced photothermoelectric detection in Co:BiCuSeO crystals with tunable Seebeck effect.

BiCuSeO is a widely-used thermoelectric material recently proved to be an appealing candidate for broadband photothermoelectric (PTE) detection. Developing a simple and scalable route for advancing PTE properties is therefore essential to explore the full potential of BiCuSeO. Here we systematically demonstrated that Co3+ atomic doping strategies in BiCuSeO single crystals (Co concentration of 1%, 2% and 4%) could modulate the Seebeck coefficient and thus strongly improve the performance of BiCuSeO PTE photodetectors across visible to infrared spectral regions. Benefiting from these strategies, a large enhancement on photovoltage responsivity is achieved and the response time of a 4% Co:BiCuSeO PTE photodetector is one order of magnitude faster than those in most of PTE photodetectors. Also, Co:BiCuSeO PTE photodetectors show good stability with changeless photoresponse after being exposed to air for three months. Therefore, the controllable atomic doping of BiCuSeO with tunable PTE properties as well as fast and broadband photodetection provides the feasibility for facilitating ongoing research toward PTE devices.

A novel method for in situ stabilization of calcium arsenic residues via yukonite formation.

Stabilizing the hazardous calcium arsenic residues (CAR) and monitoring the subsequent fate of arsenic (As) are critical to reduce its risk to the environment. In this work, a novel in situ method has been proposed to stabilize CAR by adding FeIII solution and subsequent formation of the secondary mineral (yukonite). The experiments were conducted at pH 6-9 with different Fe/As molar ratios (0.28-0.66) and the solid phases were characterized by using X-ray diffraction and scanning/transmission electron microscopy. Results showed that the stability of the CAR was significantly increased after the addition of FeIII solution, indicating good fixation effectiveness. The dissolved As concentration in the treated CAR samples continuously decreased to <5 mg/L after 490 days of treatment at Fe/As molar ratio ≥ 0.54 and pH ≥ 8, with the leached As concentration lower than 5 mg/L (US EPA standard) for most of the treated CAR in the TCLP and HVM tests. The formation of yukonite under different experimental conditions is closely related to the enhanced stability of the treated CAR. This work provides a novel in situ method to treat CAR which might have potential for future industrial applications.

Observation of surface precipitation of ferric molybdate on ferrihydrite: Implication for the mobility and fate of molybdate in natural and hydrometallurgical environments.

Adsorption of molybdate (Mo(VI)) on the surfaces of ferrihydrite is one of the most critical processes that control its mobility and fate in the environment. However, the sorption mechanism and the effect of pH on the speciation of Mo(VI) on ferrihydrite surfaces are not well understood. In this study, X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR), and Mo K-edge and L3-edge X-ray absorption spectroscopy (XAS) have been utilized to characterize the Mo(VI) species sorbed on ferrihydrite under various pH conditions. XRD, Raman, and FTIR results show that at acidic pH, surface precipitation of poorly crystalline ferric molybdate (PCFM) occurs under apparently undersaturated conditions (theoretical log IAP < log Ksp) and is enhanced by the aging process, whereas Mo(VI) is mainly present as surface adsorbed species at circum-neutral pH. The Mo K-edge and L3-edge X-ray absorption near edge structure (XANES) analyses show that a mixture of tetrahedrally and octahedrally coordinated Mo(VI) simultaneously exists at pH 3-7 and the octahedral Mo(VI) species decreases with increasing pH. The Mo-Fe interatomic distances (3.52-3.56 Å) derived from EXAFS fittings suggest the corner-sharing complexation of both MoO4 and MoO6 with FeO6 octahedra. As the pH decreases from 7 to 3, the coordination number of the Mo-Fe shell (CNMo-Fe) increases from 0.6(3) to 1.9(3), possibly due to the gradual transformation of surface adsorbed Mo(VI) to PCFM. These findings on the observation of Mo(VI) complexation, surface precipitation, and their marked pH dependence during the Mo(VI) adsorption on ferrihydrite have important implications for both understanding the mobility and fate of Mo(VI) in natural and hydrometallurgical industry impacted environments and developing optimal applications for the remediation of Mo contamination in aqueous environments.

Complexation of arsenate to humic acid with different molecular weight fractions in aqueous solution.

Natural organic matter (NOM) has been considered a critical substance in the transport and transformation of arsenic. NOM is a complex mixture of multifunctional organic components with a wide molecular weight (MW) distribution, and it is necessary to understand the complexation of arsenic with MW-dependent NOM fractions. In this study, humic acid (HA) was chosen as the representative fraction of NOM to investigate the complexation mechanism with arsenic. The bulk HA sample was fractionated to five fractions by ultrafiltration technology, and the complexing property of HA fractions with arsenic was analyzed by the dialysis method. We observed that the acidic and neutral conditions favor the complexation of HA fractions with arsenate (As(V)). The HA fractions with molecular weight > 100 kDa, 1-10 kDa, and <1 kDa have the stronger complexing capacity of As(V) than the other HA fractions. The bound As(V) percentage was positively associated with carboxyl content, phenolic content, and especially total acidity. A two-site ligand-binding model can describe the complexing capacity of arsenic onto HA fractions. The results can provide some fundamental information about the complexation of arsenic with MW-dependent HA fractions quantitatively.

High-harmonic generation in Weyl semimetal ß-WP2 crystals.

As a quantum material, Weyl semimetal has a series of electronic-band-structure features, including Weyl points with left and right chirality and corresponding Berry curvature, which have been observed in experiments. These band-structure features also lead to some unique nonlinear properties, especially high-order harmonic generation (HHG) due to the dynamic process of electrons under strong laser excitation, which has remained unexplored previously. Herein, we obtain effective HHG in type-II Weyl semimetal ß-WP2 crystals, where both odd and even orders are observed, with spectra extending into the vacuum ultraviolet region (190 nm, 10th order), even under fairly low femtosecond laser intensity. In-depth studies have interpreted that odd-order harmonics come from the Bloch electron oscillation, while even orders are attributed to Bloch oscillations under the "spike-like" Berry curvature at Weyl points. With crystallographic orientation-dependent HHG spectra, we further quantitatively retrieved the electronic band structure and Berry curvature of ß-WP2. These findings may open the door for exploiting metallic/semimetallic states as solid platforms for deep ultraviolet radiation and offer an all-optical and pragmatic solution to characterize the complicated multiband electronic structure and Berry curvature of quantum topological materials.

Partitioning and transformation behavior of arsenic during Fe(III)-As(III)-As(V)-SO42- coprecipitation and subsequent aging process in acidic solutions: Implication for arsenic mobility and fixation.

The coprecipitation and subsequent aging of Fe(III)-As(III)-As(V)-SO42- play an important role in controlling As behavior in acidic systems, such as acid mine drainage and hydrometallurgical acid waste. In this study, we investigated the redistribution and transformation of As in the Fe(III)-As(III)-As(V)-SO42- system (As(III)/As(V) ≈ 1) at different Fe/As molar ratios (i.e., 0.25, 0.5, and 1) and pH (1.2 and 1.8) at 60 °C. The results showed that As(III) and SO42- can be incorporated into the amorphous ferric arsenate and scorodite host phases by forming a Fe(AsO4)x(AsO3)y(SO4)z solid solution. As(III) contents in the freshly coprecipitated solids increased with pH and initial As(III) concentrations. During aging process, As(III) contents in the solid products with Fe/As molar ratios of 0.5 and 1 increased with aging time at pH 1.8. In contrast, As(III) was gradually expelled from aging products with aging time at pH 1.2, regardless of Fe/As molar ratio. X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and Raman spectroscopy characterization results showed that an As(III)-SO42--doped scorodite was formed at Fe/As molar ratio ≤0.5 during the aging process. It was also found that As(III) had an inhibitory effect on the transformation of poorly crystalline ferric arsenate to scorodite. The present study may have important implications for understanding the geochemical cycle of As, Fe, and SO42- in acidic solutions and give further understanding on the mechanisms involved in As removal and fixation in hydrometallurgical unit operations.

The Effect of Gypsum on the Fixation of Selenium in the Iron/Calcium-Selenium Coprecipitation Process.

The coprecipitation of selenium(IV) (Se) with iron(III) (Fe) is a widely practiced method for the removal of Se from mineral processing effluents, but the effect of gypsum as a major secondary mineral on the iron-selenium coprecipitation process is still of concern. In our work we first investigated the effects of pH, Fe/Se molar ratio and the neutralizing agent on the removal efficiency of Se by iron-selenium coprecipitation method. The developed two-step Fe-Se coprecipitation method (Fe/Se molar ratio of 4) was superior to the one-step Fe-Se coprecipitation method at pH 4 using CaO as base in terms of the stability of the generated Fe-Se coprecipitates. Raman experimental results indicated the iron-selenium coprecipitates had the by-product of calcium selenite. We then investigated the effect of incorporation of Se into gypsum on the coprecipitation process at different pHs. The fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and scanning electron microscopy (SEM) of the calcium-selenium coprecipitates showed that the Se incorporated into the structure of gypsum at pH 8-10. Therefore, this work has important implications for the development of new technologies for efficient Se removal.

Non-hydrostatic pressure-dependent structural and transport properties of BiCuSeO and BiCuSO single crystals.

High-pressure experiments usually expect a hydrostatic condition, in which the physical properties of materials can be easily understood by theoretical simulations. Unfortunately, non-hydrostatic effect is inevitable in experiments due to the solidification of the pressure transmitting media under high pressure. Resultantly, non-hydrostaticity affects the accuracy of the experimental data and sometimes even leads to false phenomena. Since the non-hydrostatic effect is extrinsic, it is quite hard to analyze quantitatively. Here, we have conducted high pressure experiments on the layered BiCuXO (X = S and Se) single crystals and quantitatively analyzed their pronounced non-hydrostatic effect by high throughput first-principles calculations and experimental Raman spectra. Our experiments find that the BiCuXO single crystals sustain the tetragonal structure up to 55 GPa (maximum pressure in our experiment). However, their pressure-dependent Raman shift and electric resistance show anomalous behaviors. Through optimization of thousands of crystal structures in the high throughput first-principles calculations, we have obtained the evolution of the lattice constants under external pressures, which clearly substantiates the non-hydrostatical pressure exerted in BiCuXO crystals. Our work indicates that the high throughput first-principles calculations could be a handy method to investigate the non-hydrostatic effect on the structural and electronic properties of materials in high pressure experiments.

Electrical scattering mechanism evolution in un-doped and halogen-doped Bi2O2Se single crystals.

Recently the layered oxide semiconductor Bi2O2Se was hotly explored for its ultrahigh mobility and ultrafast photo-response whose physical origins need to be further explored or elucidated. Here, we have grown halogen (Cl, Br, I) doped and un-doped Bi2O2Se single crystals by a melt-solidification method. Comparative electrical transport characterizations and detailed data-analysis substantiate that the electron-electron scattering is the major source of resistivity in un-doped Bi2O2Se crystals; however, in halogen-doped Bi2O2Se crystals, electron-electron scattering is only effective at low temperature (<60 K) and subsequently electron-phonon-interaction scattering is dominated to resistivity. Hall measurement and analysis show that electron concentration of halogen-doped Bi2O2Se (∼1020 cm-3) is one-order higher than un-doped one (∼1019 cm-3), but the carrier mobility of halogen-doped Bi2O2Se at 2 K (∼102 cm2 V-1 s-1) is reduced by more than two orders than un-doped ones (∼104 cm2 V-1 s-1). Three kinds of relaxation time (due to the impurity scattering, electron-electron scattering and electron-phonon scattering), calculated by linear-response theory and electron-/phonon-dispersion, are in agreement with experimental results quantitatively. The scattering mechanism evolution from sole electron-electron scattering (un-doped Bi2O2Se) to electron-phonon scattering (doped Bi2O2Se) at high temperature (>60 K) is attributed to the net effect of decreased screened Coulomb-interaction and increased Fermi energy in halogen-doped Bi2O2Se. This work may provide clues of physical origins of superior electrical/photoelectrical properties of Bi2O2Se.

Detoxification and reclamation of hydrometallurgical arsenic- and trace metals-bearing gypsum via hydrothermal recrystallization in acid solution.

Arsenic- and trace metals-bearing gypsum (As-gypsum) is one of the major hazardous solid wastes produced from metallurgical industry that poses a serious threat to the environment. However, the method for effective extraction of As and trace metals from As-gypsum is still lacking. In this study, simultaneous extraction of As and trace metals from a hydrometallurgical As-gypsum via hydrothermal recrystallization in acid solution was investigated. The effects of the type (H2SO4 vs HCl) and concentration of acid, and temperature on extraction efficiency were assessed. The results showed that 99% As, >92% Cu and >96% Zn could be extracted from the As-gypsum during hydrothermal treatment in 6 mol L-1 H2SO4 at 90 and 120 °C, but Pb and Cd could not be extracted efficiently. The results of hydrothermal treatment in HCl solutions demonstrated that higher HCl concentration and temperature significantly enhanced the extraction efficiency and 100% As, Cu2+, Zn2+, Pb2+ and >90% Cd were removed from the As-gypsum after treatment in 6 mol L-1 HCl, at 120 °C, for 12 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy results revealed that dissolution-recrystallization of gypsum is the key process for the removal of the incorporated As and trace metals. Thermodynamic modelling indicated that the released HAsO42-/Me2+ transformed into H3AsO4/MeCln(2-n) (1 ≤ n ≤ 4) species in HCl solution, hence inhibiting their reincorporation into the recrystallization products via isomorphic substitution for SO42-/Ca2+. This work provides a simple and effective method for detoxification and reclamation of As-gypsum.

A systematic study of the synthesis conditions of blue and green ultramarine pigments via the reclamation of the industrial zeolite wastes and agricultural rice husks.

Discarded industrial zeolite waste and agricultural rice husks have caused a waste of resources. To achieve resource reuse, we proposed an economical method for the preparation of ultramarine pigments via the reclamation of industrial zeolite waste (ZW) and agricultural rice husks (RHs) or previously bio-charred rice husks (BRHs). The optimal blue and green pigments were synthesized by solid state reaction of mixtures of BRH/ZW/Na2CO3/S with mass ratios of 1:2:1:1.5 and 2:2:7:3, respectively, and using a two-step calcination process with a first stage at 500 and a second stage at 800 °C. Furthermore, the blue and green pigments were also obtained using directly RH (instead of BRH) as raw material, but this time with RH/ZW/Na2CO3/S mass ratios of 1:2:2:3 and 1:2:7:3.5 and with first-stage and second-stage calcination temperatures of 400 and 800 °C. This was done to reduce additional chemical reactions (e.g., BRH derived from the pyrolysis of RH). The XRD, FT-IR, Raman, and SEM results suggest that the synthetic blue and green pigments have the sodalite structure containing S3- and S2- radicals. The synthetic green pigment using RH as raw material had the best acid resistance. Additionally, the synthesis of blue and green ultramarine pigments via the reclamation of the industrial zeolite wastes and agricultural rice husks can reduce the costs of the production process.