Photodegradation of EDTA using Fenton’s reagent: a pilot-scale study

The presence of ethylenediaminetetraacetic acid (EDTA) in decontamination wastes can cause complexation of cations resulting in interferences in their removal by various treatment processes, for example chemical precipitation, ion exchange, etc., and can negatively affect the quality of the final form of the waste. Advanced oxidation processes using ozone, H₂O₂, ultrasonics (US), ultraviolet (UV) light, Fenton’s reagent (Fe(II) + H₂O₂), alone or in combination, are regarded as possible methods of clean and ecologically safe remedial treatment for the degradation of organics. In this study, the development of a column photoreactor (15 L) and a shallow-tank photoreactor (100 L) was carried out at the Centralised Waste Management Facility, Kalpakkam, India. Pilot-scale (batch) studies of the photocatalytic degradation of EDTA (20,000 mg/L) using UV + Fenton’s reagent in these reactor geometries were attempted. The effect of the power of the UV radiation on the kinetics of photodegradation of EDTA (20,000 mg/L) was studied using the column photoreactor. The shallow-tank reactor was used to study the photodegradation of EDTA (20,000 mg/L) using UV radiation, visible radiation, and sunlight. The successful use of sunlight as a source of energy and its greater effectiveness than UV radiation in the treatment of EDTA are presented.     

Influence of luminol on the chemiluminescence intensity in Fenton’s reaction

The kinetics of Fe⁺² oxidation and buildup of luminol oxidation products during Fenton’s reaction at pH 2 have been calculated. The characteristics of the process in neutral (pH 6) and alkaline (pH 12) media have been evaluated. The calculation results have been compared with experimental data on the yield of chemiluminescence induced by Fenton’s reagent and luminol. It has been shown that trivalent iron ions suppress the luminol emission. The presence of iron or another transition metal in the sample can significantly reduce the chemiluminescence quantum yield after luminol introduction if.     

Liquid and gas chromatographic studies of the anaerobic degradation of baker’s yeast wastewater

The digestion of baker’s yeast wastewater was monitored by gas production intensity and composition of gaseous and liquid phases. Favorable coexistence of sulfate reducing bacteria and methanogens was explained by the presence and metabolism of trimethylamine, a degradation product of betaine. Concentration of sulfides decreased at the expense of betaine degradation with final products S₀ and N₂. Since biological wastewater treatment was complicated by both high content of SO₄^2-, eventually becoming reduced to toxic H₂S, and high total nitrogen content, a technological solution that links sulfate reduction to elemental sulfur coupled with reactions producing gaseous nitrogen may have great practical value.     

Oxidative degradation of polyglycols by the Ruff’s system in the aqueous solutions

We have studied oxidative degradation of polypropylene glycol and polyethylene glycols of varied molecular mass induced by hydrogen peroxide in the presence of iron(III) ions. At pH 3, the process is accompanied by aggregation of iron hydroxides and occurs in the microheterogeneous system. In the cases of high-molecular substrates, the oxidation is accompanied by decrease in the polymer globulas size due to the degradation of the polymer chain.     

Paneth’s epistemology of chemical elements in light of Kant’s Opus postumum

Friedrich Paneth’s conception of “chemical element” has functioned as the official definition adopted by the International Union of Pure and Applied Chemistry since 1923. Paneth maintains a distinction between empirical and “transcendental” concepts of element; furthermore, chemical science requires fluctuation between the two. The origin of the empirical-transcendental split is found in Immanuel Kant’s classic Critique of Pure Reason (1781/1787). The present paper examines Paneth’s foundational concept of element in light of Kant’s attempt, late in life, to revoke key distinctions made in his Critique, including that of regulative and constitutive functions of reason. In a section of his Opus postumum devoted to the “Transition from the Metaphysical Foundations of Natural Science to Physics,” Kant bends his philosophical system to address the newly emerging sciences of matter of his time. Specifically, he tried, without success, to develop the transcendental ground for microscale motions of bodies encountered in physical, electrical and chemical processes. Paneth’s discussion of chemical element does not take the Opus postumum into account, which is why it begins with a rejection of Kant’s rejection (in his earlier writings) of chemistry’s status as science. I make the case that Paneth’s definition of element effectively maintains something very like Kant’s critical separation of regulative and constitutive principles, while a advancing the concept of chemical science.     

Improvement of Weyl’s Inequality

Consider the construction of an operator from the sum of two component operators. Weyl’s inequality gives a lower bound to an eigenvalue of the constructed operator using a single eigenvalue from each of the component operators. Using such minimal information gives a poor bound, however, and when the eigenvectors that correspond to the said eigenvalues of the component operators are known, Weyl’s inequality can be significantly improved by considering the overlap of the two eigenvectors. This improvement can sometimes be further improved when several eigenvectors of each component operator are known so that the overlap of sub-eigenspaces are considered instead. The improvement is best when there is minimal overlap and Weyl’s inequality returns when the overlap is complete. An example with the hydrogen molecular ion is presented which illustrates the superiority over Weyl’s inequality when eigenvector or sub-eigenspace information is utilized.     

Reduction of ostazine dyes’ photodynamic effect by Fenton reaction

The aim of this work was to evaluate the influence of ostazine dyes on the microbial population in environment. These dyes act as photosensitizers after irradiation by visible light. The photodynamic effect was induced in this way. The effect of irradiated water solutions of ostazine green, ostazine yellow, and ostazine blue on the Escherichia coli growth was tested. Furthermore, the effect of these dyes (at c = 3.5 μg mL⁻¹) on bacterial growth was evaluated after their pretreatment by the Fenton reaction. Dramatic changes in dyes’ toxicity were observed after coloured solutions were pretreated by the Fenton reaction.     

The Biochemistry of Life’s Energy

On December 10, 1997, the 101st anniversary of Alfred Nobels death, in Stockholms Concert Hall Swedish King Carl XVI Gustav awarded one half of the 1997 Nobel Prize in Chemistry (3.75 million kronor, about $500,000) to Professor Emeritus Paul Delos Boyer, age 79, of the University of California, Los Angeles and Dr. John Ernest Walker, age 56, of the Medical Research Council Laboratory of Molecular Biology, Cambridge, England for their elucidation of the enzymatic mechanism underlying the synthesis of adenosine triphosphate (ATP) and one half (3.75 million kronor, about $500,000) to Professor Emeritus Jens Christian Skou, age 79, of Århus University, Århus, Denmark for the first discovery of an ion-transporting enzyme, Na⁺, K⁺-ATPase.     

Molecular interpretation of Trouton’s and Hildebrand’s rules for the entropy of vaporization of a liquid

The entropy of vaporization at a liquid’s boiling point is well approximated by Trouton’s rule and even more accurately by Hildebrand’s rule. A cell method is used here to calculate the entropy of vaporization for a range of liquids by subtracting the entropy of the gas from that of the liquid. The liquid’s entropy is calculated from the force magnitudes measured in a molecular dynamics simulation based on the harmonic approximation. The change in rotational entropy is not accounted for except in the case of liquid water. The predicted entropies of vaporization agree well with experiment and Trouton’s and Hildebrand’s rules for most liquids and for water except other liquids with hydrogen bonds. This supports the idea that molecular rotation is close to ideal at a liquid’s boiling point if hydrogen bonds are absent; if they are present, then the rotational entropy gain must be included. The method provides a molecular interpretation of those rules by providing an equation in terms of a molecule’s free volume in a liquid which depends on the force magnitudes. Free volumes at each liquid’s boiling point are calculated to be ～1 Å³ for liquids lacking hydrogen bonds, lower at ～0.3 Å³ for those with hydrogen bonds, and they decrease weakly with increasing molecular size.     

The estimation of ether’s enthalpies of formation

Taking hydrocarbon as gerneratrix, the differences of enthalpies of formation of ether and their corresponding generatrixes were compared and concluded and the equation to estimate ether’s enthalpy of formation, which was Δ_f H _e^°/(kJ/mol) = K(Δ_f H _m^ℴ − 90 + A) was obtained. The results can be elucidated with bond dissociation energies data, bond-enthalpy of formation method, induction effect and conjugative effect. The more essential account to explain the results can be got by using quantum chemistry theories, etc. Using replacement and comparison method, the way of estimation of organic compounds’ thermodynamic properties including enthalpy of formation can be obtained either. The article is published in the original.     

Heterogeneous Fenton degradation of azo dye 4BS over Co–Mn–Fe ternary hydrotalcites

This work described the application of Co–Mn–Fe hydrotalcites (Co–Mn–Fe LDHs) as heterogeneous catalysts for Fenton reaction process. The Co–Mn–Fe LDHs were synthesized by the co-precipitation method and were characterized by X-ray diffractometry (XRD), infrared spectroscopy (IR), zeta potential, and BET surface area measurement. The catalytic activity of different kinds of hydrotalcites was evaluated by the degradation of Direct Scarlet 4BS (4BS). The Co–Mn–Fe LDHs showed the best catalytic performance among four catalysts. The presence of the Mn²⁺/Mn³⁺ at surface of catalyst could accelerate the reduction of Co³⁺–Co²⁺, and then increased in the catalytic activity of the Co–Mn–Fe LDHs. The effect of initial pH, catalyst dosage, dye concentration, and reaction temperature on the degradation of 4BS had been investigated. Radical reaction mechanism was proposed by the addition of radical scavenger. The degradation kinetic followed pseudo-first-order model. The activation energy of Co–Mn–Fe LDHs was determined to be 37.3 kJ/mol. The catalytic activity of Co–Mn–Fe LDHs was maintained after four cycles of reaction, which proved the reusability of catalyst. Finally, the possible reaction mechanisms involved in the heterogeneous Fenton system were proposed.     

Theoretical Studies of Water’s and Methanol’s Effects on Alcoholysis of N-Benzyl-3-oxo-β-sultam

The mechanisms about the water’s and methanol’s effects on the alcoholysis of N-benzyl-3-oxo-β-sultam together with their differences have been studied by using density func- tional theory at the B3LYP/6-31G* level. The results, in comparison with a previous study on the relative reaction without the assistance of water and methanol, show that the added water or methanol can remarkably reduce the energy barrier of alcoholysis reaction of N-benzyl-3-oxo- β-sultam and the most favorite pathway is the breaking of C–N bond instead of S–N. It is also found that the reaction energy barrier of methanol-assisted alcoholysis is a little higher than that of the water-assisted one.     

Reaction of levoglucosenone with Dane’s diene

Cycloaddition of levoglucosenone to 7-methoxy-4-vinyl-1,2-dihydronaphthalene has been studied under different conditions, including heating under atmospheric pressure, in a sealed ampule, and under high pressure, as well as under microwave irradiation and in the presence of various catalysts. The chiral Diels–Alder adduct thus obtained can be used in the synthesis of estrone and its analogs.     

The chemist’s concept of molecular structure

The concept of molecular structure is fundamental to the practice and understanding of chemistry, but the meaning of this term has evolved and is still evolving. The Born–Oppenheimer separation of electronic and nuclear motions lies at the heart of most modern quantum chemical models of molecular structure. While this separation introduces a great computational and practical simplification, it is neither essential to the conceptual formulation of molecular structure nor universally valid. Going beyond the Born–Oppenheimer approximation introduces new paradigms, bringing fresh insight into the chemistry of fluxional molecules, proteins, superconductors and macroscopic dielectrics, thus opening up new avenues for exploration. But it requires that our ideas of molecular structure need to evolve beyond simple ball-and-stick-type models.

Celebrating Michael Faraday’s Discovery of Benzene

Abstract

In 1825, Michael Faraday, working in his workshop at the Royal Institution, discovered what he called bicarburet of hydrogen, now known as benzene. One hundred years later, his discovery was celebrated at the Royal Institution by a host of national and international delegates. Just over thirty years after Faraday’s discovery, the industrial importance of benzene was realised with the establishment of the synthetic dyestuffs industry. In this paper, the Faraday Benzene Centenary Celebration is discussed in detail and compared with other celebrations that have linked benzene with colour, in particular the 1890 celebration in Germany of the benzene ring formula and the 1906 celebration of the foundation of the coal-tar dye industry. It is instructive to review the different economic and political agendas underlying these events, each within the context of a particular time and place.     

Viscosity of liquid alloys: generalization of Andrade’s equation

Abstract  

The Andrade relation for the viscosity of liquid metals has been reformulated in terms of the Debye temperature for liquid metals. This semi-empirical relation has been extended to obtain a relation to calculate the composition and temperature dependence of the viscosity of liquid alloys using parameters which can be determined experimentally. The important inputs are the enthalpy of formation, ΔH, and the excess volume of mixing, ΔΩ. The composition dependence of the viscosity and its deviation from linear behavior could be positive or negative depending on the sign and magnitude of ΔH and ΔΩ. Several limiting cases of the semi-empirical relation for the viscosity of liquid alloys are compared and discussed. The results of the semi-empirical relation for viscosity isotherms for binary and ternary liquid alloys are mostly in reasonable agreement with available experimental results.     

A skeptic’s review of the New SI

Proposals in draft form have been circulated for new Système International (SI) measurement units that are expected to be official instruments of the Treaty of the Metre by 2015. This review outlines the substance of the proposals and examines some of the consequences of the continuing evolution of the SI toward inter-dependence of base units and quantities since its introduction in 1960. The proposals in question fix at an exact value a number of inter-related fundamental natural constants such as the speed of light, the Planck constant, the elementary charge and Boltzmann’s constant. All SI units are then so defined that their magnitude is set by those fixed values. Notably, the ongoing confusions about chemical measurements and the thermodynamic ‘mole’ are exacerbated. On the big principles of the basic purpose of the SI to facilitate communication and the fixing of fundamental physical constants of nature, there are significant problems and unanswered questions. They risk: damage to the enterprise of science; wide economic loss including increased transaction costs and barriers to global trade; barriers to new technologies and to improvements in measurement accuracy; loss of measurement compatibility or consistency; and a circular global measurement system vulnerable to undetectable systematic errors with serious adverse consequences for environmental decision making among many other vital human activities. The New SI requires frank and open discussion throughout science, technology, industry, trade, and global policy well before irreversible decisions are made.     

Synthesis of aromatic polyamidines in Eaton’s reagent

Aromatic polyamidines are prepared via the polycondensation of dicarboxamides and diamines in Eaton’s reagent. The polymers are investigated by elemental analysis and IR and NMR spectroscopy. Polyamidines are well soluble in concentrated sulfuric acid and concentrated formic acid and in polar organic solvents, and temperatures corresponding to their 10% weight losses are in the range 245–280°C.