Results 1 - 10 of 12
Results 1 - 10 of 12. Search took: 0.017 seconds
|Sort by: date | relevance|
[en] The conditional experiments are completed in two kinds of columns, -5 mm and-10 mm, for uranium ore heap leaching. The results show that: 1) The performance of uranium ore and acid consumption are good, which is suitable for acid leaching; 2) The usage of antioxidant is better in alkaline leaching than acid leaching; 3) The influence of uranium ore size is significant. (authors)
[en] Lake Qinghai in the Qinghai-Tibet plateau is the largest lake in China. This study firstly reported the geochemistry of Cd in the lake. Water samples were collected from Lake Qinghai (n = 69) and Buha River (n = 12), while sediment (n = 22) and topsoil (n = 45) samples were collected from the lake and around the lake area, respectively. In addition, pore water samples (n = 20) were separated from sediment samples. Water samples were analyzed for pH, K, Na, Ca, Mg, Cl, S, and Cd, while sediment and topsoil samples were analyzed for K, Na, Ca, Mg, Al, Fe, Mn, S, Sc, and Cd. The average concentration of Cd was 0.014 μg L−1 in the water of Lake Qinghai and 0.007 μg L−1 in the water of Buha River. However, the average concentration of Cd was 0.320 μg L−1 in the sediment pore water, much higher than that in the lake water and river water. Cadmium concentration in the lake water might be mainly controlled by salinity, while it in the pore water might be mainly controlled by carbonate minerals. Cadmium concentration in the river water might be controlled by alkalinity and pH. The average concentration of Cd in the sediment was 0.284 mg kg−1. The enrichment of Cd in the lake sediment was significantly higher than that in the topsoil around the lake. Anthropogenic atmospheric deposition of Cd did not led to the increase in dissolved Cd level in the lake water, but led to its enrichment in the lake sediment.
[en] CoxMg1−xAl2O4 (x = 0–0.8) nanoparticles were synthesized by sol–gel method, and characterized by X-ray powder diffraction and transmission electron microscopy. X-ray photoelectron spectroscopy and 27Al solid-state NMR spectroscopy were performed to study the chemical environments of cations in the nanoparticles as a function of cobalt content and annealing temperature. The results show that the crystallite size of the particles is about 20–40 nm. Besides the tetrahedral and octahedral coordinations, the second octahedrally coordinated Al3+ ions are observed in the samples. The inversion parameter (two times the fraction of Al3+ ions in tetrahedral sites) decreases with the increase of annealing temperature and cobalt content. The fraction of octahedral Mg2+ decreases with the increase of Co concentration. The absorption spectra indicate that Co2+ ions are located in the tetrahedral sites as well as in the octahedral sites in the nanoparticles. The intensity of the absorption peak corresponding to octahedral Co2+ ions (300–500 nm) decreases with increasing annealing temperature. -- Highlights: ► Effects of Co content and temperature on the cation distribution in CoxMg1−xAl2O4 nanoparticles are studied. ► Mg2+ and Co2+ ions occupy both tetrahedral and octahedral sites in the nanoparticles. ► The secondly octahedral Al3+ ions are observed besides the above two coordination sites. ► Inversion parameter of the samples decreases with the increase of annealing temperature and cobalt content. ► Optical properties of the nanoparticles are discussed on the basis of the structural results.
[en] The treatment of 2,4,5-trichlorobiphenyl (PCB29) in simulated soil-washing solution by granular activated carbon (GAC) adsorption and microwave (MW) regeneration was investigated in this study. The PCB29 adsorption process was carried out in a continuous flow adsorption column. After adsorption, the PCB29-loaded GAC was dried at 103 deg. C, and regenerated in a quartz reactor by 2450 MHz MW irradiation at 700 W for 5 min. The efficacy of this procedure was analyzed by determining the rates and amounts of PCB29 adsorbed in successive adsorption/MW regeneration cycles. Effects of the regeneration on the textural properties and the PCB29 adsorption capacity of GAC were examined. It was found that after several adsorption/MW regeneration cycles, the adsorption rate of GAC increased, whereas, the adsorption capacity decreased, which could be explained according to the change of textural properties. Most of the PCB29 adsorbed on GAC was degraded within 3 min under MW irradiation, and the analysis of degradation products by GC-MS demonstrated that PCB29 experienced dechlorination during this treatment
[en] By dimensional reduction of the 3D motif of CsAgBiBr, a lead-free 2D hybrid double perovskite, (i-PA)CsAgBiBr (1, i-PA=isopentylammonium), was successfully designed. It adopts a quantum-confined bilayered structure with alternating organic and inorganic sheets. Strikingly, the unique 2D architecture endows it highly anisotropic nature of physical properties, including electric conductivity and optical absorption (the ratio α/α=1.9 at 405 nm). Such anisotropy attributes result in the strong polarization-sensitive responses with large dichroic ratios up to 1.35, being comparable to some 2D inorganic materials. This is the first study on the hybrid double perovskites with strong polarization sensitivity. A crystal device of 1 also exhibits rapid response speed (ca. 200 μs) and excellent stabilities. The family of 2D hybrid double perovskites are promising optoelectronic candidates, and this work paves a new pathway for exploring new green polarization-sensitive materials. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
[en] Highlights: • Growth habits of ZCTC been investigated photographically by means of micro-crystallization method, and bulk crystals with dimensions of 51 × 15 × 12 and 28 × 13 × 12 mm3 were obtained by the solvent-evaporation method. • The two-dimensional nucleation growth mechanism and crystal twinning defect of ZCTC crystal were discovered for the first time. • The relative dielectric constants and elastic compliance constants were determined. Meanwhile first-principles calculation was used to calculate elastic constants. • The thermal diffusivities and thermal conductivities were obtained. Bulk single crystals of zinc cadmium thiocyanate, ZnCd(SCN)4 (ZCTC) with dimensions of 51 × 15 × 12 and 28 × 13 × 12 mm3 have been obtained. Growth habits were investigated, two-dimensional nucleation growth mechanism and crystal twinning defect were observed from the as-grown crystals. The thermal diffusivities were measured, and then thermal conductivities were calculated with values decreasing from 1.3683 to 0.8739 W⋅m−1⋅K−1 and 0.8496 to 0.5356 W⋅m−1⋅K−1 as the temperature increasing from 303 to 423 K, along the a- and c-directions, respectively. The relative dielectric constants and elastic compliance constants at room temperature were determined. Meanwhile, first-principles calculation was used to calculate elastic constants.
[en] Halide double perovskites have recently bloomed as the green candidates for optoelectronic applications, such as X-ray detection. Despite great efforts, the exploration of promising organic–inorganic hybrid double perovskites toward X-ray detection remains unsuccessful. Now, single crystals of the lead-free hybrid double perovskite, (BA)CsAgBiBr (BA is n-butylammonium), featuring the unique 2D multilayered quantum-confined motif, enable quite large μτ (mobility-lifetime) product up to 1.21×10 cm V. This figure-of-merit realized in 2D hybrid double perovskites is unprecedented and comparable with that of CHNHPbI wafers. (BA)CsAgBiBr crystals also exhibit other intriguing attributes for X-ray detection, including high bulk resistivity, low density of defects and traps, and large X-ray attenuation coefficient. Consequently, a vertical-structure crystal device under X-ray source yields a superior sensitivity of 4.2 μC Gy cm. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
[en] Tetracycline (TC) is frequently detected in the environment, however, knowledge on the environmental fate and transport of TC is still limited. Batch adsorption experiments of TC by soil and sediment samples were conducted. The distribution of charge and electrostatic potential of individual atoms of various TC species in the aqueous solution were determined using MOPAC version 0.034 W program in ChemBio3D Ultra software. Most of the adsorption isotherms on the soil, river and marine sediments were well fitted with the Freundlich and Polanyi-Manes (PMM) models. The single point organic carbon (OC)-normalized adsorption distribution coefficients (KOC) and PMM saturated adsorption capacity (QOC0) values of TC were associated with the mesopore volume and clay content to a greater extent, indicating the mesopore volume of the soil and sediments and their clay content possibly influenced the fate and transport of TC in the natural environment. The adsorption of TC on soil and sediments strongly depended on the pH and presence of Cu(II). The presence of Cu(II) facilitated TC adsorption on soil and sediments at low pH (pH < 5), possibly due to the metallic complexation and surface-bridging mechanism by Cu(II) adsorption on soil and sediments. The cation exchange interaction, metallic complexation and Coulombic interaction of mechanisms for adsorption of TC to soils and sediments were further supported by quantum chemical calculation of various TC species in different pH.
[en] Simazine sorption to corn straw biochars prepared at various temperatures (100-600 deg. C) was examined to understand its sorption behavior as influenced by characteristics of biochars. Biochars were characterized via elemental analysis, BET-N2 surface area (SA), FTIR and 13C NMR. Freundlich and dual-mode models described sorption isotherms well. Positive correlation between log Koc values and aromatic C contents and negative correlation between log Koc values and (O + N)/C ratios indicate aromatic-rich biochars have high binding affinity to simazine (charge transfer (π-π*) interactions) and hydrophobic binding may overwhelm H-bonding, respectively. Dual-mode model results suggest adsorption contribution to total sorption increases with carbonization degree. Positive correlation between amounts of adsorption (Qad) and SA indicates pore-filling mechanism. Comparison between our results and those obtained with other sorbents indicates corn straw biochars produced at higher temperature can effectively retain simazine. These observations will be helpful for designing biochars as engineered sorbents to remove triazine herbicides. - Highlights: → Biochars were characterized via elemental analysis, BET-N2, FTIR and 13C NMR. → Freundlich and dual-mode models described sorption isotherms well. → Biochar produced at higher temperature had larger sorption capacity for simazine. → Aromatic-rich biochars have high binding affinity to simazine. → Dual-mode model results suggest adsorption contribution to total sorption. - The corn straw biochar prepared at higher temperature with stronger hydrophobicity, more aromatic C and larger surface area had higher sorption capacity for simazine.
[en] Highlights: • S(IV)/PDS system showed synergistic degradation of BPA than S(IV) and PDS. • BPA degradation involved hydroxyl and oxysulfur radicals in the S(IV)/PDS system. • Based on the identified intermediates, the BPA degradation pathway was proposed. - Abstract: In this study, the bisulfite-peroxydisulfate system (S(IV)/PDS) widely used in polymerization was innovatively applied for organic contaminants degradation in water. The addition of S(IV) into PDS system remarkably enhanced the degradation efficiency of bisphenol A (BPA, a frequently detected endocrine disrupting chemical in the environments) from 17.0% to 84.7% within 360 min. The degradation efficiency of BPA in the S(IV)/PDS system followed pseudo-first-order kinetics, with rate constant values ranging from 0.00005 min"−"1 to 0.02717 min"−"1 depending on the operating parameters, such as the initial S(IV) and PDS dosage, solution pH, reaction temperature, chloride and water type. Furthermore, nitrogen purging experiment, radical scavenging experiment and electron spin resonance (ESR) analysis were used to elucidate the possible mechanism. The results revealed that sulfate radical was the dominant reactive species in the S(IV)/PDS system. Finally, based on the results of liquid chromatography–mass spectrometry (LC–MS) and gas chromatography–mass spectrometry (GC–MS), the BPA degradation pathway was proposed to involve β-scission (C−C), hydroxylation, dehydration, oxidative skeletal rearrangement, and ring opening. This study helps to characterize the combination of PDS and inorganic S(IV), a common industrial contaminant, to generate reactive species to enhance organic contaminants degradation in water.