ANALYTICAL CHEMISTRY
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2011
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IF 5.874
Cheng-Xiong Yang,Xiu-Ping Yan
The diverse structures and pore topologies, accessible cages and tunnels, and high surface areas make metal–organic frameworks attractive as novel media in separation sciences. Here we report the slurry-packed MIL-101(Cr) column for high-performance liquid chromatographic separation of substituted aromatics. The MIL-101(Cr) packed column (5 cm long × 4.6 mm i.d.) offered high-resolution separation of ethylbenzene (EB) and xylene, dichlorobenzene and chlorotoluene isomers, and EB and styrene. The typical impurities of toluene and o-xylene in EB and styrene mixtures were also efficiently separated on the MIL-101(Cr) packed column. The column efficiencies for EB, m-dichlorobenzene, and m-chlorotoluene are 20000, 13000, and 10000 plates m–1, respectively. The relative standard deviation for five replicate separations of the substituted aromatics was 0.2–0.7%, 0.9–2.9%, 0.5–2.1%, and 0.6–2.7% for the retention time, peak area, peak height, and half peak width, respectively. The MIL-101(Cr) offered high affinity for the ortho-isomer, allowing fast and selective separation of the ortho-isomer from the other isomers within 3 min using dichloromethane as the mobile phase. The effects of the mobile phase composition, injected sample mass, and temperature were investigated. The separation of xylene, dichlorobenzene, and chlorotoluene on MIL-101(Cr) was controlled by entropy change, while the separation of EB and styrene on MIL-101(Cr) was governed by enthalpy change.
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CHEMICAL ENGINEERING JOURNAL
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2019
·
IF 8.355
Qiaoyuan Gao,Dagang Lin,Yongjie Fan,Qin He,Qi Wang
Visible-light-active Fe-2MI assemblies were prepared at room temperature using 2-Methylimidazole (2MI) as organic ligand to form complex with Fe(II) or Fe(III). TGA and XRD characterizations indicated that Fe(II) can form more stable complex and higher coordinating percentage with 2MI relative to Fe(III). Besides, Fe(II)-2MI displayed amorphous state with larger BET surface area and higher photocurrent response. At very low catalyst dosage (0.1 g/L), highest activity for Cr(VI) reduction can be achieved using Fe(II)-2MI as photocatalyst. The estimated pseudo-first-order rate constant (0.021 min −1 ) was 1.4 and 2.1 times that on Fe(III)-2MI and Fe(II)-NaOH, respectively. The well-known ZIF-67 (Co-2MI), ZIF-7 (Zn-2MI) and Fe-MOFs with other organic ligands (H 2 BDC, NH 2 -H 2 BDC or FA) were also used as control samples. Optimal activity for photocatalytic reduction of Cr(VI) was achieved by Fe(II)-2MI. The operating factors was optimized at acidic pH (2.0), higher catalyst dosage (0.3 g/L) and appropriate concentration of coexisting organics (2.0 mM) within the tested range. The stability of Fe(II)-2MI was investigated at different pH values (2, 3 and 4.64), which all displayed good stability. Mechanism study indicated that Fe(II)-2MI has adequate conduction and valence band positions for Cr(VI) reduction and organics oxidation, respectively. Therefore, the as-prepared amorphous Fe(II)-2MI assemblies may be cheap, stable and easy available candidate for the photocatalytic disposal of Cr(VI)-containing wastewaters.
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CARBON
·
2021
·
IF 9.594
Mingyan Jia,Lulin Peng,Maohua Yang,Huangzhao Wei,Mei Zhang,Yu Wang
In this article, we show that the conventional boron-nitrogen co-doped carbon dots (BNCDs) exhibit unique fluorescent ratiometricity in the detection of Cr (VI) due to their unique dual emission system. The 3D fluorescence spectrum study reveals that besides the commonplace emission centered at (360, 465) nm in blue fluorescence region, another center which may be corresponding to N-contain conjugation domains is found at (490, 535) nm. In the presence of Cr (VI) ions, the emission centered at (360, 465) nm is remarkably quenched due to inner filter effect, whereas the emission centered at (490, 535) nm is almost unchanged. By spectrally simulating inner filter effect using different excitation interferents in the 3D fluorescence spectrum study, accompanied with the fluorescence lifetime and absorption comparison, the sensing mechanism has thoroughly been illustrated. The versatile sensing capability of BNCDs in the different real samples not only provides a new way for the rapid determination of Cr (VI) in practices, but also demonstrates the great potential of the carbon-based materials with multiple emission possess in developing ratiometric sensing platform for rapid and accurate assay of different kinds of analytes.
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Nanomaterials
·
2022
·Vol. 12
·期 21
·3923
·
IF 5.719
Wen-Yi Wang,Tian Sang,Yan Zhong,Chao-Hao Hu,Dian-Hui Wang,Jun-Chen Ye,Ni-Ni Wei,Hao Liu
The surfactant modification of catalyst morphology is considered as an effective method to improve photocatalytic performance. In this work, the visible-light-driven composite photocatalyst was obtained by growing CdS nanoparticles in the cubic crystal structure of CdCO3, which, after surfactant modification, led to the formation of CdCO3elliptical spheres. This reasonable composite-structure-modification design effectively increased the specific surface area, fully exposing the catalytic-activity check point. Cd2+from CdCO3can enter the CdS crystal structure to generate lattice distortion and form hole traps, which productively promoted the separation and transfer of CdS photogenerated electron-hole pairs. The prepared 5-CdS/CdCO3@SDS exhibited excellent Cr(VI) photocatalytic activity with a reduction efficiency of 86.9% within 30 min, and the reduction rate was 0.0675 min−1, which was 15.57 and 14.46 times that of CdS and CdCO3, respectively. Finally, the main active substances during the reduction process, the photogenerated charge transfer pathways related to heterojunctions and the catalytic mechanism were proposed and analyzed.Keywords:surfactant;CdS/CdCO3;photocatalytic;Cr(VI)
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KOREAN JOURNAL OF CHEMICAL ENGINEERING
·
2022
·Vol. 39
·期 7
·1839-1849
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IF 3.146
Zhang Xiaoting,Zhang Shusheng,Ouyang Gangfeng,Han Runping
A zirconium-based metal organic framework (UiO-66-NH 2 ) was prepared using a greener approach for the removal of hexavalent chromium (Cr(VI)) from solution. The characterization of UiO-66-NH 2 was performed using several methods, and the influence of the solution pH, adsorbent dosage, salt, adsorption time, Cr(VI) concentration and adsorption temperature on adsorption quantity was performed in batch mode. UiO-66-NH 2 can efficiently remove Cr(VI) through the synergistic effect of adsorption and reduction. At pH solution of 1.1 and solid-to-liquid ratio of 2 g·L −1 , the removal rate of 100 mg·L −1 Cr(VI) increased to 95.2%. The maximum adsorption capacity of UiO-66-NH 2 from Langmuir model was 252 mg·g −1 . The adsorption equilibrium process can be well described by Langmuir, Koble-Corrigan and Temkin models, while the kinetic process can be predicted by pseudo-second-order and Elovich model. UiO-66-NH 2 showed a good adsorption capacity in a wide range of pH (pH=1.1–10) and also had better regeneration performance after five cycles using 0.01 mol·L −1 NaOH; consequently, it can be a promising adsorbent for the removal of Cr(VI) from solution.
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SCIENCE OF THE TOTAL ENVIRONMENT
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2022
·
IF 10.753
Jing Yang,Qian Guo,Lei Li,Ruixue Wang,Yucheng Chen,Xingrun Wang
Compare to the content of Cr(VI), the distribution of specific Cr(VI) species in soil is rarely paid attention to, which may lead to an inaccurate environmental risk assessment of Cr(VI) contaminated soil or inability to meet stringent requirement for soil remediation . Herein, to reveal the primary mechanisms and factors controlling the evolution of Cr(VI) species in soil, the distribution of Cr(VI) and Cr(III) species in soils with different particle sizes and textures was systematically investigated by using a modified sequential extraction procedure and spectroscopy characterizations (e.g., SEM-EDS mapping). The results show that a significant proportion of Cr(VI) can be captured by minerals containing exchangeable calcium ions and metal oxide hydrates in the soil, forming a relatively stable adsorbed Cr(VI). Also, a small fraction of Cr(VI) can precipitate as calcium chromate with free calcium ion which is the most stable Cr(VI) species in the soil. The majority of Cr(VI) discharged into soil tends to be reduced by ferrous ions or minerals containing ferrous ions with a product of Fe(III)-Cr(III) coprecipitate. Therefore, the speciation of Cr in the soil is closely correlated to Fe and Ca. After the equilibrium of adsorption, precipitation, and reduction reactions of Cr(VI), the rest of Cr(VI) retains as the form of its original water-soluble state in soil. The evolution of Cr(VI) species and the content of specific Cr species in soil are mainly determined by the contents of iron, exchangeable calcium ions and metal oxide hydrates, which effect the Cr(VI) reduction, precipitation and adsorption, respectively.
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ENVIRONMENTAL POLLUTION
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2016
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IF 4.839
Na Li,Fenglian Fu,Jianwei Lu,Zecong Ding,Bing Tang,Jiabin Pang
Chromium-contaminated water is regarded as one of the biggest threats to human health. In this study, a novel magnetic mesoporous MnFe 2 O 4 @SiO 2 −CTAB composite was prepared by a facile one-step modification method and applied to remove Cr(VI). X-ray diffraction, scanning electron microscopy, transmission electron microscopy , specific surface area, and vibrating sample magnetometer were used to characterize MnFe 2 O 4 @SiO 2 −CTAB composites. The morphology analysis showed that the composites displayed a core-shell structure. The outer shell was mesoporous silica with CTAB and the core was MnFe 2 O 4 nanoparticles , which ensured the easy separation by an external magnetic field. The performance of MnFe 2 O 4 @SiO 2 −CTAB composites in Cr(VI) removal was far better than that of bare MnFe 2 O 4 nanoparticles. There were two reasons for the effective removal of Cr(VI) by MnFe 2 O 4 @SiO 2 −CTAB composites: (1) mesoporous silica shell with abundant CTA + significantly enhanced the Cr(VI) adsorption capacity of the composites; (2) a portion of Cr(VI) was reduced to less toxic Cr(III) by MnFe 2 O 4 , followed by Cr(III) immobilized on MnFe 2 O 4 @SiO 2 −CTAB composites, which had been demonstrated by X-ray photoelectron spectroscopy results. The adsorption of Cr(VI) onto MnFe 2 O 4 @SiO 2 −CTAB followed the Freundlich isotherm model and pseudo-second-order model. Tests on the regeneration and reuse of the composites were performed. The removal efficiency of Cr(VI) still retained 92.4% in the sixth cycle. MnFe 2 O 4 @SiO 2 −CTAB composites exhibited a great potential for the removal of Cr(VI) from water.
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SCIENCE OF THE TOTAL ENVIRONMENT
·
2018
·
IF 4.61
Shunquan Shi,Jiakuan Yang,Sha Liang,Mingyang Li,Quan Gan,Keke Xiao,Jingping Hu
Fe 3 O 4 @SiO 2 -NH 2 magnetic particles with core-shell structure were attached on carboxylated biochar derived from phoenix tree leaves to synthesize a novel magnetic biochar for removing Cr(VI) ions from acidic solutions. FSEM, FTEM, XRD characterizations of the synthesized magnetic biochar revealed that the Fe 3 O 4 @SiO 2 -NH 2 magnetic particles distributed uniformly on the surface or macrospores of carboxylated biochar by strong chemical bonding. The Cr(VI) ions adsorption capacity of magnetic biochar was 27.2 mg·g −1 , surpassing original carboxylated biochar (18.2 mg·g −1 ). VSM and XPS characterizations demonstrated that the attached Fe 3 O 4 @SiO 2 -NH 2 magnetic particles not only endowed biochar with perfect magnetic property (23 emu·g −1 ) but also provided complexing sites for binding Cr(III) cations reduced from Cr(VI) anions. The Cr(VI) ions removal by magnetic biochar contained three steps: (1) adsorption of Cr(VI) anions by protonated functional groups; (2) reduction of Cr(VI) anions to Cr(III) cations by electron-donor groups; and (3) chelation of Cr(III) cations by amine groups. The adsorption recycling test showed that magnetic biochar kept 85% of its initial Cr(VI) adsorption capacity at the sixth cycle, and the Fe leakage under pH 1.0 was smaller than 0.25 mg·L −1 . The results indicated that this novel magnetic biochar was applicable for the practical treatment of Cr(VI)-containing wastewater.
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CERAMICS INTERNATIONAL
·
2025
·Vol. 51
·期 30
·65388-65397
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IF 5.6
Jiahao Zha,Chongjun He,Fangzhou Chen,Xianhong Li,Jiayin Song,Chenguang Deng,Qian Li,Lijuan Liu,Mingjun Xia,Yuangang Lu
The fluorescence intensity ratio (FIR) technique has emerged as a pivotal approach in non-contact optical thermometry, offering substantial application potential. In this study, Y 3 Al 5 O 12 (YAG) phosphors co-activated with Ce 3+ and Cr 3+ ions were successfully synthesized through a high-temperature solid-state reaction method. Spectroscopic analysis revealed efficient energy transfer between the dopant ions, manifesting as distinct luminescence intensity variations compared to their single-doped counterparts. Under 450 nm excitation, the system demonstrates prominently yellow-green emission from Ce 3+ ions and well-resolved red emission from Cr 3+ ions, ensuring excellent spectral discrimination. Capitalizing on the differential thermal response between the two luminescent centers, the developed system achieves remarkable temperature sensing performance. The FIR method yields a maximum relative sensitivity of 0.845 % K −1 , maintaining sensitivity above 0.6 % K −1 throughout the 340–580 K range, coupled with exceptional temperature resolution below 0.03 K. Furthermore, we have engineered a novel FIR thermometry system incorporating 3D-printed spectral modules and fiber-optic phosphor encapsulation. The integrated system demonstrates superior sensing capabilities, reaching sensitivity values of 1.23 % K −1 in Cr 3+ lifetime mode and 4.64 % K −1 in FIR mode. These results indicate that Ce/Cr co-doped YAG has exceptional potential in multimodal optical thermometry applications.
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JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY
·
2020
·Vol. 20
·期 3
·1660-1669
·
IF 1.134
Deng Yu-Ying,Xiao Xin-Feng,Wang Dan,Han Bo,Gao Yu,Xue Jian-Liang
Cu-BTC was synthesised by hydrothermal method in this study to adsorb and remove the toxic heavy metal hexavalent chromium Cr(VI) in water. The EDTA-chitosan/Cu-BTC was prepared by the surface modification of Cu-BTC with EDTA-modified chitosan. The initial concentration effects of adsorbed
chromium solution, adsorbent dosage, adsorption time, adsorption temperature and pH of chromium solution on adsorption capacity were estimated using the single-factor optimisation experiment. Results show that the adsorption capacity of the modified composite was higher than that of Cu-BTC.
Cu-BTC and EDTA-chitosan/Cu-BTC exhibited significant adsorption of Cr(VI) under acidic conditions in water and basically independent of temperature. Their adsorption processes conformed with the pseudo-second-order model. The Langmuir adsorption isotherm model obtained the adsorption isotherm,
which indicated that the adsorption process was single molecule adsorption. Isotherm fitting obtained the maximum adsorption amounts of Cr(VI) for Cu-BTC and EDTA-chitosan/Cu-BTC at 27.32 and 46.51 mg·g-1, respectively. Factor and principal component analyses show that the
main factors affecting the adsorption of Cr(VI) in the EDTA-chitosan/Cu-BTC composites are pH, initial concentration and adsorption time. Therefore, EDTA-chitosan-modified Cu-BTC was a more feasible metal-organic framework material than Cu-BTC because of better adsorption performance, which
can be used for adsorption removal of Cr(VI) in water.
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CHINESE CHEMICAL LETTERS
·
2013
·
IF 1.21
Bing Zhao,Ya-Cui Zhou,Meng-Jiao Fan,Zhi-Yu Li,Li-Yan Wang,Qi-Gang Deng
Three tetraaryl imidazole derivatives 5a–5c bearing thiazole groups were synthesized in the presence of [Bmin]Br by one-pot reaction and their structures were fully characterized by the 1 H NMR, IR, MS and elemental analysis. The results of UV–vis spectra and fluorescent spectra upon metal ions complexation show that compound 5a displays high selectivity and sensitivity for Cr 3+ ions. The complexation ratio of compound 5a and Cr 3+ is 1:1.
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SEPARATION AND PURIFICATION TECHNOLOGY
·
2022
·
IF 9.136
Qunfeng Kuang,Kun Liu,Qikun Wang,Qibing Chang
Biochar is used as adsorption material for transition metal ions based on its special high surface area. However, the ion adsorption capacity is limited by the inability through the increasing of specific surface area. Three-dimensional hierarchical pore biochar (ASPB) is prepared by pre-carbonization and KOH activation using soybean protein with gelation properties to construct a three-dimensional framework structure of biomass. The saturation level of Cr(VI) adsorption in 250 mg·L −1 Cr(VI) solution is 489.66 mg·g −1 , which is attributed to the ASPB's vast 2788 m 2 ·g −1 surface area and three-dimensional hierarchical pore structure, with pore structure data indicating an empty volume of 1.65 cm 3 ·g −1 and a 2.386 nm size average pore size. The Cr(VI) adsorption level is higher than the calculated saturated capacity according to Langmuir equation based on the specific surface area. The extra adsorption performance is contributed to the transport channels provided by the three-dimensional framework structure, the large and abundant ion riveting sites provided by micro-mesopores, and the redox and complexation of surface-active groups. The saturated adsorption capacity can keep 86.6 % after three adsorption–desorption cycles.
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