Fig 4 - uploaded by Rinaldo Cervellati
Content may be subject to copyright.
![Comparison of Ce(IV) with Ce(III) as a catalyst. [H 2 SO 4 ], 0.20 M ; [NaIO 3 ], 0.025 M ; [MA], 0.050 M ; [H 2 O 2 ], 1.0 M ; (darker) [Ce(III)], 0.0025 M ; (lighter)](publication/273513921/figure/fig1/AS:302228914098186@1449068396559/Comparison-of-CeIV-with-CeIII-as-a-catalyst-H-2-SO-4-020-M-NaIO-3-0025-M.png)
Comparison of Ce(IV) with Ce(III) as a catalyst. [H 2 SO 4 ], 0.20 M ; [NaIO 3 ], 0.025 M ; [MA], 0.050 M ; [H 2 O 2 ], 1.0 M ; (darker) [Ce(III)], 0.0025 M ; (lighter)
Source publication
![Fig. 3. (a) Iodine production with Mn(II), lower range. [KIO 3 ] 0 =...](publication/273513921/figure/fig3/AS:667717921169423@1536207766538/a-Iodine-production-with-MnII-lower-range-KIO-3-0-0020-M-H-2-SO-4-0_Q320.jpg)
![Fig 4. Comparison of Ce(IV) with Ce(III) as a catalyst. [H 2 SO 4 ],...](publication/273513921/figure/fig1/AS:302228914098186@1449068396559/Comparison-of-CeIV-with-CeIII-as-a-catalyst-H-2-SO-4-020-M-NaIO-3-0025-M_Q320.jpg)
Cerium(III) catalysts can replace manganese(II) in the classic Briggs-Rauscher oscillator also containing acid, iodate, hydrogen peroxide, and malonic acid. H 2SO 4 was used as an acid; if HClO 4 is used, cerium iodate precipitates. Cerium(III) oxalate typically precipitates by the time oscillations end. Ce(III) at low concentrations is roughly thr...
Context in source publication
Context 1
... Ce(IV) is added last to a BR mix- ture containing H 2 O 2 but no catalyst, the solution be- comes turbid, but much less precipitation takes place. Reduction to Ce(III) is much slower than with "free Ce(IV)", so there is an induction period as Ce(III) in- creases, and then oscillations begin. Table 5 summa- rizes several runs with Ce(IV) catalyst. Fig. 4 shows a comparison of Ce(III) with ...
Citations
... Substitutions of chemicals are possible; different acids, organic substrates, and ions, such as Ce(III) instead of Mn(II) catalyst, can be used to generate BR oscillations [7][8][9][10]. However, the oscillatory behavior is not the only one that attracted the attention of non-linear scientists in the Briggs-Rauscher reaction [11][12][13][14][15]. ...
In this account, we describe the crazy-clock phenomenon involving the state I (low iodide and iodine concentration) to state II (high iodide and iodine concentration with new iodine phase) transition after a Briggs-Rauscher (BR) oscillatory process. While the BR crazy-clock phenomenon is known, it is the first time that crazy-clock behavior is linked and explained with the symmetry-breaking phenomenon, highlighting the entire process in a novel way. The presented phenomenon has been thoroughly investigated by running more than 60 experiments, and evaluated by using statistical cluster K-means analysis. The mixing rate, as well as the magnetic bar shape and dimensions, have a strong influence on the transition appearance. Although the transition for both mixing and no-mixing conditions are taking place completely randomly, by using statistical cluster analysis we obtain different numbers of clusters (showing the time-domains where the transition is more likely to occur). In the case of stirring, clusters are more compact and separated, revealed new hidden details regarding the chemical dynamics of nonlinear processes. The significance of the presented results is beyond oscillatory reaction kinetics since the described example belongs to the small class of chemical systems that shows intrinsic randomness in their response and it might be considered as a real example of a classical liquid random number generator.
... Each potentiometric cycle is reliable, typically lasting 10-30 seconds, thus potentiometric methods have been developed to study the antioxidant concentration in complex matrices. [9][10][11][12][13][14][15] However, potentiometric measurement require platinum, silver or other similar electrodes that are not readily available in educational settings. This idea of using BR reaction to quantify antioxidant can be made simpler for use to the wider student and agricultural communities if potentiometric measurements can be replaced by color change, which can be monitored visually or be coupled with a simple spectrometer that is widely available. ...
The Briggs-Rauscher (BR) reaction is free radical based where the kinetics of formation of different iodide species leads to potentiometric and color oscillations. These oscillations were monitored in this study using a UV/Vis attenuated total reflection probe to develop an assay to measure the antioxidant content in complex matrices. The periodicity of the BR reaction was found to be very consistent (range 24-25 seconds, n = 16). Adding various amounts of ascorbic acid, a well-known antioxidant, led to an inhibition of the reaction with a linear calibration curve of antioxidant periodicity time (APT, r 2 > 0.99). The validity of this test in complex matrices was studied by determining the APT of nine fruits, and the resulting antioxidant capacity in ascorbic acid equivalency was calculated. The results generated by this assay were found be accurate through comparison with the well-established FRAP assay. These results show that visual or spectrometric monitoring of BR reaction can be used as a reliable, quick, and inexpensive alternative to more established assays with the added advantage that values generated from this assay is at pH 2 which is similar to that in the human stomach.
... Kang et al. (2019) described a novel method of recovering lanthanum as lanthanum oxalate from aqueous solution using biomass-free culture supernatants after the growth of A. niger. In general, it is assumed that biogenic oxalate can interact with phosphate through the following mechanisms (Chi and Xu, 1999;Furrow et al., 2012): ] = $ 10 −26 , is lower than that of LnPO 4 ($10 −23 ), speciation of oxalate-containing secondary minerals during interaction of monazite-containing rare earth phosphates in an acidic fungal-induced environment could be a profitable approach for biorecovery and worthy of examination. Bioprocessing is currently viewed as a promising alternative or adjunct to new methods of element recovery to ensure the security of supply of valuable strategic elements but little is known about microbial interactions with REE. ...
Monazite is a naturally‐occurring lanthanide (Ln) phosphate mineral [Lnx(PO4)y] and is the main industrial source of the rare earth elements (REE), cerium and lanthanum. Endeavours to ensure the security of supply of elements critical to modern technologies view bioprocessing as a promising alternative or adjunct to new methods of element recovery. However, relatively little is known about microbial interactions with REE. Fungi are important geoactive agents in the terrestrial environment and well known for properties of mineral transformations, particularly phosphate solubilization. Accordingly, this research examined the capability of a ubiquitous geoactive soil fungus, Aspergillus niger, to affect the mobility of REE in monazite and identify possible mechanisms for biorecovery. It was found that A. niger could grow in the presence of monazite and mediated the formation of secondary Ce and La‐containing biominerals with distinct morphologies including thin sheets, orthorhombic tablets, acicular needles, and rosette aggregates which were identified as cerium oxalate decahydrate (Ce2(C2O4)3·10H2O) and lanthanum oxalate decahydrate (La2(C2O4)3·10H2O). In order to identify a means for biorecovery of REE via oxalate precipitation the bioleaching and bioprecipitation potential of biomass‐free spent culture supernatants was investigated. Although such indirect bioleaching of REE was low from the monazite with maximal lanthanide release reaching >40 mg L‐1, leached REE were efficiently precipitated as Ce and La oxalates of high purity, and did not contain Nd, Pr and Ba, present in the original monazite. Geochemical modelling of the speciation of oxalates and phosphates in the reaction system confirmed that pure Ln oxalates can be formed under a wide range of chemical conditions. These findings provide fundamental knowledge about the interactions with and biotransformation of REE present in a natural mineral resource, and indicate the potential of oxalate bioprecipitation as a means for efficient biorecovery of REE from solution. This article is protected by copyright. All rights reserved.
... For example, cerium (IV) ions catalyze the oxidation of organic compounds in acidic media [72]. The Belousov-Zhabotinsky reaction (oxidation of citric acid and inorganic model of the biochemical Krebs cycle) is also well studied [73]; cerium can replace manganese in the oscillating reaction of Briggs-Rauscher [74], etc. ...
Cerium oxide nanoparticles (nanoceria) possess enormous biological activity, wherein many aspects related to the biological properties of nanoceria still remain unclear. In the present chapter, we have tried to explore the possible biological mechanisms of nanoceria action in terms of the catalytic activity of CeO2 particles and chemical behavior of cerium ions. Based on the analysis of a large number of about 500 primary sources, we can draw a conclusion that the ability to inactivate reactive oxygen species (oxophilicity) and to scavenge free radicals, as well as the phosphatase-like activity, is typical for both ceria and cerium ions. In turn, ceria nanoparticles specifically interact with electromagnetic radiation, but cannot participate in the natural enzymatic cycles of plants and animals. Future promising therapeutic applications of cerium oxide include delivery of various drugs and treatment of the diseases associated with oxidative stress, redox therapy of oncological diseases, adjuvant in antiviral therapy, prebiotic and immunomodulator, carrier and restriction enzyme mimetic in gene therapy, modulator of signal transduction in neurology, etc.
... Iodine I(+1) and I(+3) are intermediates in many reactions of iodine derivatives [1][2][3][4]. Among others, they are intermediates in the Bray-Liebhafsky [5][6][7][8] and Briggs-Rauscher oscillating reactions [9][10][11][12][13]. I(+1) has also an important role in the exchange of iodine between seawaters and the atmosphere [14][15][16][17]. ...
The absorption spectra in a large range of concentrations show that the reactions of iodate with iodine in 96% sulfuric acid produce (IO)HSO4, I3⁺ and I5⁺, just like in the pure 100% acid. We discovered that, in 96% H2SO4, these reactions also produce I2O which is not formed in the pure acid. I2O is an important intermediate of reactions in diluted sulfuric acid, including the Bray-Liebhafsky reaction, but it had never been observed directly because of its very high reactivity. The equilibrium constants of the reactions producing these four compounds were determined.
... The Briggs-Rauscher (BR) reaction [1] shows different non-linear phenomena in systems containing sulfuric or perchloric acid, iodate, hydrogen peroxide, a metal catalyst (Mn(II) or Ce(III)) and different organic substrates [2][3][4][5][6][7][8][9][10][11][12][13]. This composition suggests a relation with the oscillating Bray-Liebhafsky and Belousov-Zhabotinsky reactions. ...
... In more classical terms, we could say that their concentrations are quasi-stationary. The rate of reaction (16) is given by (17) so that the numerical simulations depend on only one parameter (K12k14) and not on the individual rate constants of reactions (12), (14) and ( is not an elementary reaction and its complicated rate law [26] reduces to the form given in Table 1 at high acidities. The rate constant k-M3 = 1.810 -3 is well known [43,44] and k+M3 is calculated using k+M3 = KM3k-M3. ...
The Dushman reaction (reduction of iodate by iodide) is a subsystem of the Briggs–Rausher oscillating reaction. We show that the previously observed effects of Ce(III) and Mn(II) on the kinetics of the Dushman reaction are mainly ionic strength effects. The observed decrease of the rate constant of the Dushman reaction when the ionic strength increases and the formation of the ion pairs MnSO4(aq) and CeSO4⁺ explain quantitatively our kinetic results. We also show why the original mechanism of the Briggs–Rausher reaction must be revised and propose a variant of the mechanism proposed in 2002 by Furrow, Cervellati and Amadori. This variant establishes a relationship with the reduction of iodate by high concentrations of hydrogen peroxide and the non-catalyzed BR reaction.
... Such oscillations in redox potential could be monitored potentiometrically. Metallic ions such as Ce 4 + , Mn 2 + [20][21][22] have already been used as catalysts in the BR system. In 1994, Rosokha and Tikhonova [23] [24][25][26][27][28][29][30][31][32]. ...
... By its composition, iodate, hydrogen peroxide, malonic acid in the original recipe and Mn(II) or Ce(III) catalyst in acidic solution, it looks like a combination of BL and BZ reactions but experimental studies show that it has its own characteristics [18]. Many variants exist [19][20][21], including the possibility to obtain oscillations in the absence of catalyst [22]. ...
This review summarizes the highlights of the history of oscillating reactions since the discovery of Bray in 1917 through the discovery of Belousov, the exponential growth of the number of works in the field that followed it and chemical chaos. It focuses on the work of Professor Slobodan Anić and the Belgrade group.
... The classic system [2] contains 0.027 M H 2 SO 4 , 0.067 M KIO 3 , 0.050 M malonic acid (MAH 2 ), 0.0067 M MnSO 4 , 1.5 M H 2 O 2 , and 0.01 % starch. Substitutions can be made with different acids, different organic substrates [3][4][5], and Ce(III) instead of Mn(II) catalyst [6]. With the classic concentrations, the oscillations eventually end with a transition to a reduced state with high [I -] and precipitation of solid I 2 . ...
... All oscillating experiments were carried out in double-walled beakers, protected from light, thermostatted at 25°C. The experimental details of that set-up have been reported previously [6]. ...
... It was proposed that the following reaction takes place to lower HOO Á ] 0 = 1.0 M prevented a transition for at least 2500 s. This cerium-based reference system had been previously studied [6]. ...
The interesting behavior of the Briggs–Raucher oscillating reaction does not stop with the end of oscillations. Depending on the initial concentrations, the classic mixture with malonic acid may undergo a sudden transition from a state with low [I2] and [I−], to a state with high [I2] and [I−]. A proposed mechanism involving radical attack on iodomalonic acid and diiodomalonic acid shows qualitative agreement with experiments.
Autocatalytic feedback is often regarded as the core step for the chemo-hydrodynamical patterns in the nonlinear reaction system. The Briggs-Rauscher (BR) reaction shows sequential chemo-hydrodynamical patterns with three states, i.e. labyrinth, high iodine state, and rotating dendritic patterns. The short-lived labyrinth patterns, depending on [Mn2+]0, the ratio of [CH2(COOH)2]0 and [KIO3]0 and light intensities, result from iodide autocatalytic loop, which has three paths (involving Mn2+-induced radical reactions, the oxidation of iodomalonic compounds, and light-induced radical reactions, respectively). The high iodine state appears in a high ratio of [CH2(COOH)2]0 and [KIO3]0, relating to the autocatalytic path involving the oxidation of iodomalonic compounds. The light-induced radical autocatalytic path can act as a convenient control parameter to modulate the patterns in the first stage by increasing the iodine radicals. The dendritic patterns in the third stage result from the Marangoni effect caused by the evaporation of the solutions and reactions between H2O2 and iodine-containing species, which is independent of [CH2(COOH)2]0 and [Mn2+]0. This work contributes to a better understanding of the complex spatiotemporal patterns in the chemo-hydrodynamical system.
