16065-83-1Relevant academic research and scientific papers
Kinetics and mechanism of the oxidation of l-methionine by aqueous solution of chromium(VI)
Olatunji, M.Adegboyega,Ayoko, G.Adefikayo
, p. 11 - 15 (1988)
The kinetics of the reduction of Cr(V1) by l-methionine (represented by RSCH3) have been studied in aqueous perchloric acid. The data are consistent with the rate law: -d[Cr(VI)] dt = (k1 + k2[H+]2[RSCH3])[Cr(VI)] with k1 = (3.1 ± 0.5) x 10-4 s-1; k2 = 12.3 ± 1.1 mol-3 dm9 s-1 at I = 1.0 mol dm-3 (NaClO4), [H+] = 40.04-0.10 mol dm-3 and T 25.1°C. The corresponding activation parameters are ΔH1* = 26.2 ± 0.4 kJ mol-1; ΔS1* = -224± 1 JK-1 mol-1; ΔH1* = 33.9±0.01 KJ mol-1; ΔS1* -111±1 JK-1 mol-1. The above rate is very much slower than those of other related reactions. This is interpreted in terms of a rate-determining CrS bonded intermediate which undergoes hydrolysis after electron transfer to yield Cr(III) and methionine sulphoxide. The significance of pathways involving second-order substrate dependence is also discussed.
Ultrasound-assisted method to improve the structure of CeO2?polyprrole core-shell nanosphere and its photocatalytic reduction of hazardous Cr6+
Balakumar, Vellaichamy,Kim, Hyungjoo,Manivannan, Ramalingam,Kim, Hyorim,Ryu, Ji Won,Heo, Gisu,Son, Young-A.
, (2019)
In this work, the CeO2?polypyrrole (CeO2?PPy) core-shell nanosphere has been synthesized via an ultra-sonication method using bath type (WUC-D22H, Daihan Scientific, Korea) and they are utilized for the photo-reduction of hazardous Cr6+ to benign Cr3+. The ultrasonic frequency and power were 20 kHz and 100 W, respectively. The PPy shielded CeO2 in aqueous solution could prevent the dissolution of CeO2 and to improve the photocatalytic ability of CeO2. X-ray diffraction was used to confirm the crystalline structure of as prepared CeO2?PPy core-shell and FT-IR was used to identify the functional groups. The uniform sized core of PPy and shell of CeO2 were observed by transition electron microscopy. The ultrasonic assisted synthesized CeO2?PPy core-shell exhibits a narrow bandgap (UV-DRS) and good reduction efficiency with higher reusability and stability compared to pure CeO2, PPy and mechanical mixing of CeO2?PPy. Moreover, the synergistic effect of CeO2 and PPy core-shell structure facilitate a higher electron transfer rate and prolong lifetime of photogenerated electron-hole pairs which can achieve good reduction rate of 98.6% within 30 min. In particular, the pH, catalyst, and Cr6+ concentration effects were optimized in photocatalytic reduction reactions. Meanwhile, this photocatalysis with fast and effective electron transfer mechanism for the Cr6+ reduction was elucidated. This method opens a new window for simple fabrication of conducting polymers-based metal oxide nanocomposite towards wastewater remediation and beyond.
Excellent photoreduction performance of Cr(vi) over (WO4)2--doped metal organic framework materials
Zhao, Xinyun,Wu, Lamei,Chen, Xi,Hu, Juncheng,Wu, Tsung-Hsueh,Li, Qin,Lv, Kangle
, p. 20704 - 20714 (2020)
A new conductive metal-organic-framework (MOF) photocatalyst, (WO4)2-doped bismuth terephthalate (referred to as nNa2WO4BiBDC), was synthesized and characterized by varying the precursor molar ratio (n = 0.1, 0.3, 0.4, and 0.5) of Na2WO4/Bi(NO3)3 in the presence of terephthalic acid through a one-pot solvothermal process. This study found that doping (WO4)2- into BiBDC enhanced the separation of photo-generated carriers, improved the photocatalytic properties of bismuth terephthalate (BiBDC), and enabled the application in Cr(vi) reduction under UV light irradiation with the synergic effect from citric acid acting as a hole scavenger. Among all the precursor ratios of Na2WO4/Bi(NO3)3 used, 0.4Na2WO4BiBDC has the optimum performance, leading to triple gain in reduction efficiency for undoped BiBDC. The synthetic strategy to dope (WO4)2- into a layered MOF as a viable option for modification of MOFs was demonstrated in this study. Finally, the photoreduction of Cr(vi) by (WO4)2-doped bismuth terephthalate enables a new promising wastewater treatment option. This journal is
CeO2/g-C3N4/V2O5 ternary nano hetero-structures decorated with CQDs for enhanced photo-reduction capabilities under different light sources: Dual Z-scheme mechanism
Kumar, Amit,Naushad, Mu.,Sharma, Gaurav,Sharma, Sunil Kumar,Stadler, Florian J.
, (2020)
In this work, a carbon quantum dots (CQDs) decorated dual Z-scheme CeO2/g-C3N4/V2O5 heterojunction (CCGV) was rationally synthesized by simple hydrothermal method. The crystal structure, morphology, and optical properties of the photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectroscopy. CCGV catalyst shows high visible absorption, including near infra-red region and solar light via two-channel charge transfer (dual Z-scheme), reduced recombination, and up-conversion effect of CQDs. The heterojunction was used for visible assisted photo-reduction of carcinogenic hexavalent chromium ions (Cr(VI)) with a 99% reduction in 100 min without any sacrificial agent or hole scavenger. The reaction becomes more rapid with tartaric acid as a scavenger with a complete reduction in just 30 min under visible light. Photogenerated electrons are the dominant active species, followed by ●O2?, as revealed by the scavenging experiments. The use of sacrificial agents and scavengers suggests that photogenerated electrons were the dominant active species followed by ●O2? radicals. The electrochemical impedance spectroscopy and photoluminescence results confirm highly reduced recombination, high charge separation, and charge transfer capacity in the dual Z-scheme heterojunction. The conduction band edges of CeO2 and V2O5 (which are protected by the dual charge transfer) have an appropriate potential for the rapid reduction of hexavalent chromium. The XPS scan of the catalyst after separation shows the presence of Cr in the +3 oxidation state, suggesting complete photo-reduction. This study is promising for developing wide spectrum active simple heterojunction photocatalysts for pollutant removal with high efficiency.
Highly efficient and bifunctional Cd(II)-Organic Framework platform towards Pb(II), Cr(VI) detection and Cr(VI) photoreduction
Cai, Xin-Bin,Chen, Ling-Hui,Guan, Bin-Bin,Li, Dan,Li, Qing,Liu, Tian-Hui,Wu, Zhi-Qiang,Zhu, Wei
, (2021)
Lead and chromate/dichromate are widely used in manufacturing industry, but Pb(II) and Cr(VI) ions pose fatal threats to human health and the water ecological environment. It is thus highly desirable to develop novel and valid strategies for rapid detection and effective decontamination of these heavy metal ions. Design and assembly of luminescent Metal-Organic Framework (LMOFs) for effective recognition and removal of Pb(II) and/or Cr(VI) from water provide a feasible avenue to address this issue. Herein, a novel Cd(II)-MOF, [(Cd3L2)]·(solvent)x (labeled as compound 1) with bright blue fluorescence was assembled under the solvothermal reaction of triangular ligand 5'-(5-carboxy-1H-benzo [d]imidazole-2-yl)-[1,1':3′,1″-terphenyl]-4,4″-dicarboxylic acid (H3L) and Cd(NO3)2. Given that the unique structure features of 3D stacking framework, i. e. strong π···π conjugative effects of organic linkers, plentiful free imidazole N atoms and carboxyl O atoms, Cd-MOF of 1 was deliberately deployed as bifunctional platform to sense Pb(II)/Cr(VI) and photochemically reduce Cr(VI) to Cr(III). Notably, 1 emits durable bright blue fluorescence and performs rapid quenching sense for Pb2+, Cr2O72? and CrO42?, with ultra low detection limits of 1.89, 4.83 and 2.84 ?ppb, respectively. Moreover, highly toxic Cr(VI) could be rapidly and thoroughly reduced to Cr(III) ions by 1 under the irradiation of mercury lamp, with reliable recycling ability. The possible photoluminescence, quenching and photocatalytic reduction mechanisms also were tentatively proposed.
Two novel organic phosphorous-based MOFs: synthesis, characterization and photocatalytic properties
Zeng, Tianyu,Wang, Liwen,Feng, Lu,Xu, Hailong,Cheng, Qingrong,Pan, Zhiquan
, p. 523 - 534 (2019)
Two novel metal-organic framework (MOF) photocatalysts with different structures [(Cu(H2L)(4,4′-bipy)0.5(H2O)] (1) and [Co(C14H14O6.5P2)(4,4′-bipy)0.5(H2O)2]·H2O (2) were synthesized using a hydrothermal method using a phosphonate ligand [H4L = 1,1′-biphenylene-4,4′-bis(methylene)-bis(phosphonic acid)] and 4,4′-bipyridine ligand. All the samples were characterized by elemental analysis, thermal analysis, and single crystal X-ray diffraction. As novel porous materials, the two complexes showed active performance for the reduction of Cr(vi) to Cr(iii) and the photodegradation of methylene blue (MB) dye in aqueous solution under UV light. Control experiments showed that the pH value was vital for Cr(vi) reduction, meanwhile, the use of a hole scavenger of methanol promoted the photocatalytic reduction significantly. It was also demonstrated that complexes 1 and 2 were efficient for the degradation of MB. Moreover, the possible reaction mechanism of the reaction was also investigated in detail. Finally, the cyclic experiments indicated the two photocatalysts were stable and reusable, enabling them to be potential candidates for use in environment governance.
Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies
Ravishankar, Thammadihalli Nanjundaiah,Ramakrishnappa, Thippeswamy,Nagaraju, Ganganagappa,Rajanaika, Hanumanaika
, p. 146 - 154 (2015)
CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450°C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm-1 due to the Ce-O-Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce CrVI to CrIII and show antibacterial activity against Pseudomonas aeruginosa.
Carbon-Doped Mesoporous Anatase TiO2 Multi-Tubes Nanostructures for Highly Improved Visible Light Photocatalytic Activity
Purbia, Rahul,Borah, Rituraj,Paria, Santanu
, p. 10107 - 10116 (2017)
Development of a high surface area and efficient visible light induced photocatalyst on a large scale is a promising task from the practical perspective. In this study, visible light active C-doped anatase TiO2 multi-tubes were synthesized using banana (Musa acuminata) stem fiber as a sacrificial template, removed by calcination at 450 °C. During the calcination process, the lattice of anatase TiO2 phase was doped with C, and obtained multi-tubes showed high surface area (～99 m2/g) with a mesoporous structure made of ～15 ± 3 nm nanoparticles. The synthesized TiO2 multi-tubes showed an enhanced light absorption property in the whole visible light region and good thermal stability of the anatase phase up to 750 °C. The synthesized C-doped TiO2 multi-tubes manifest an excellent photocatalytic activity for the reduction of Cr (VI) to Cr(III) under the visible light exposure. This process may have lots of practical importance as the method of synthesis of the catalyst is novel and the multi-tubes structure can be synthesized on a large scale through a quick and economical way with excellent photocatalytic activity. This novel multi-tubes structure may also be useful for photovoltaics, antimicrobial, and Li-batteries applications in the future.
Sunlight assisted degradation of dye molecules and reduction of toxic Cr(VI) in aqueous medium using magnetically recoverable Fe3O4/reduced graphene oxide nanocomposite
Boruah, Purna K.,Borthakur, Priyakshree,Darabdhara, Gitashree,Kamaja, Chaitanya K.,Karbhal, Indrapal,Shelke, Manjusha V.,Phukan, Pallabi,Saikia, Dulen,Das, Manash R.
, p. 11049 - 11063 (2016)
In view of the significant impact of magnetically recoverable catalysts in photocatalytic applications, Fe3O4/reduced graphene oxide (rGO) nanocomposite photocatalyst was synthesized by adopting an eco-friendly solution chemistry app
Kinetic Salt Effects on the Reaction between the Cobalt(III) Ion, Co(sep)3+, and the Hexa-aquochromium(II) Ion
Ferranti, Francesco,Indelli, Antonio
, p. 2241 - 2248 (1989)
Highly specific effects are shown by different salts on the title reaction.Some salts increase the rate by a factor between ca. two and four, whereas for others the increase is between 30 and over a 1000 times.This is attributed to the formation of highly reactive ion pairs (or triplets), whose formation constants have been evaluated, in some cases, from the kinetic data at constant ionic strength.These ion pairs involve essentially the CrII reactant, and their high reactivity is related to the rate of formation of the precursor complex and/or to the rate of electron transfer within the precursor complex.
