Dichloroacetic Acid Solution Research Articles

Mikania micrantha extract as a novel inhibitor for the corrosion of cold rolled steel in Cl2HCCOOH solution

Plant extract as the corrosion inhibitor has the multiple merits of inexpensive, eco-friendly and biodegradable. The corrosion inhibition of cold rolled steel (CRS) in dichloroacetic acid (Cl2HCCOOH) solution by Mikania micrantha extract (MME) was investigated by weight loss, electrochemical techniques and surface analysis. The results show that MME exhibits efficient inhibition, and the maximum inhibition efficiency is up to 91.2% in 0.10 M Cl2HCCOOH. The adsorption of MME on CRS surface obeys Langmuir isotherm. The activation process from the reactant to transition state is endothermic. The inhibitive performance remains stable from 6 to 48 h at 20 and 30 °C, while drops initially from 6 to 24 h, and then keeps a steady state until 48 h. Increasing acid concentration leads to significant reduction of inhibitive action at 20 °C, while slightly decreases at 30–50 °C. MME is a mixed-type inhibitor that drastically retards both cathodic and anodic reactions simultaneously. Electrochemical impedance spectroscopy has only one time constant, whose Nyquist appears a depressed capacitive loop, and there is only one peak in the Bode-phase plots. The radius of the capacitive arc gradually increases with the increase of MME concentration. Scanning electron microscopy and atomic force microscopy analyses can directly confirm that the addition of MME leads to a prominent reduction in corrosion as well as surface roughness of the CRS surface. The surface tension decreases with the increase of MME concentration. Besides ferulic and chlorogenic acids, other effective components in MME would contribute on the inhibitive action.

Role of reactive oxygen species on the activity of noble metal-doped TiO2 photocatalysts.

Modified TiO2 catalysts are of interest in environmental water remediation since they can lead to efficient electron-hole separation and greatly enhance the photocatalytic properties of TiO2. Reactive oxygen species (ROS), such as the superoxide radical (O2-), hydroxyl radical (OH), and positive valence band holes (h+VB), have been reported as the main oxidative species involved in photocatalytic degradation processes. In this work, the role of these species using TiO2, TiO2/Pt 0.5 wt%, and TiO2/Ag 10 wt% has been examined in order to clarify the oxidation pathways. For this purpose, the contribution of the main oxidative species was analyzed in the photocatalytic degradation of dichloroacetic acid (DCA) solutions using specific scavengers (benzoquinone, tert-butyl alcohol, and formic acid). Moreover, the hydroxyl radicals were quantitatively determined in order better understand the results. Regardless of the catalyst used, it is concluded that OH radicals are the major reactive species responsible for DCA degradation and no significant degradation is due to O2- radicals. Nevertheless, different OH generation pathways were found, depending on the nature of the catalysts. Degradation using TiO2 was conducted mainly via OH radicals generated in the positive holes, while noble metal-doped TiO2 catalysts generated OH radicals through the transformation of O2- radicals.

Enhanced photocatalytic activity using GO/TiO2 catalyst for the removal of DCA solutions.

This work aimed to optimize high-performance photocatalysts based on graphene oxide/titanium dioxide (GO/TiO2) nanocomposites for the effective degradation of aqueous pollutants. The catalytic activity was tested against the degradation of dichloroacetic acid (DCA), a by-product of disinfection processes that is present in many industrial wastewaters and effluents. GO/TiO2 photocatalysts were prepared using three different methods, hydrothermal, solvothermal, and mechanical, and varying the GO/TiO2 ratio in the range of 1 to 10%. Several techniques were applied to characterize the catalysts, and better coupling of GO and TiO2 was observed in the thermally synthesized composites. Although the results obtained for DCA degradation showed a coupled influence of the composite preparation method and its composition, promising results were obtained with the photocatalysts compared to the limited activity of conventional TiO2. In the best case, corresponding to the composite synthesized via hydrothermal method with 5% of GO/TiO2 weight ratio, an enhancement of 2.5 times of the photocatalytic degradation yield of DCA was obtained compared to bare TiO2, thus opening more efficient ways to promote the application of photocatalytic remediation technologies.

On the photocatalytic degradation of phenol and dichloroacetate by BiVO 4: The need of a sacrificial electron acceptor

The photodegradation of phenol and dichloroacetic acid (DCAA) by BiVO 4 was studied in the absence as well as presence of selected electron scavengers. The experiments were performed under the visible (vis) irradiation of aqueous solutions over a wide pH range (1–13). Phenol was photocatalytically degraded by BiVO 4 into p-benzoquinone below pH 3 and into an open-ring structure at pH 13. Methylene blue (MB) accelerated the reaction below the isoelectric point of BiVO 4 and did not undergo significant degradation. In presence of H 2O 2, phenol was rapidly degraded up to pH 9. The degradation rates are two orders of magnitude higher than in absence of electron scavenger. The degradation of dichloroacetic acid was only possible in presence of H 2O 2. High initial concentrations of H 2O 2 inhibit the reaction and its consumption is very fast. Sequential additions of this sacrificial electron acceptor (SEA) enables the total degradation of a 1 mM DCAA solution.

Reduction of protons assisted by a hexanuclear nickel thiolate metallacrown: protonation and electrocatalytic dihydrogen evolution

The hexanuclear metallacrown [Ni6L12] (L is mu-S-CH2-CH2-S-C6H4-Cl) has been demonstrated to functionally resemble the [NiFe] hydrogenases. Protonation of the [Ni6L12] cluster was studied employing 1H NMR spectroscopy by the sequential additions of dichloroacetic acid or p-toluenesulfonic acid monohydrate into solutions of [Ni6L12] in CD2Cl2 and DMF-d7, respectively; protonation takes place on the thioether sulfurs available in the metallacrown. Electrochemical properties of both the parent and protonated [Ni6L12] species have been studied using cyclic voltammetry. Protonated [Ni6L12] shows an interesting electrocatalytic property as it catalyzes the reduction of protons to molecular hydrogen in the presence of protic acids, such as dichloroacetic acid and chloroacetic acid at -1.5 and -1.6 V vs. Ag/AgCl in DMF, respectively. A catalytic cycle has been proposed based on the observations from the NMR spectroscopic and electrochemical studies of the metallacrown. The behavior of this electrocatalyst was further studied by its immobilization on the surface of a pyrolytic graphite electrode; reduction of a dichloroacetic acid solution in acetonitrile on the surface of the modified electrode occurs at 220 mV more positive potential compared to the unmodified electrode.

Synthesis and characterization of processible polyaniline containing plasticizing dendron-type dopants

Bifunctional dendrons consisting of sulfonic acid core and plasticizing peripheral groups were synthesized and used for polyaniline doping. The second generation dendrons were prepared in a two step procedure involving esterification of iminodiacetic acid, followed by the reaction of the resulting diester with sulfosuccinic acid. Plasticizing dendrons facilitate polyaniline solution processing and efficiently protonate it, despite their relatively large size (molar mass from 764 to 1100 g/mol). Their size and shape influence however the supramolecular organization of the polyaniline–dopant associations. Layered structure, clearly seen in for polyaniline protonated with first generation dendrons by X-ray diffraction, is lost for polyaniline protonated with the second generation ones. The polymer retains its film forming properties giving by casting from dichloroacetic acid solution free standing films which combine plasticized state with reasonably good conductivity from 1 to 8.5 S/cm.

Formation and morphologies of ethylcyanoethyl cellulose/poly(ε‐caprolactone) blending films

AbstractThe texture of ethylcyanoethyl cellulose [(ECE)C]/poly(ε‐caprolactone) (PCL)/dichloroacetic acid (DCA) solutions and the morphology of the (ECE)C/PCL blending films were studied by polarizing optical microscope. The critical concentration of the (ECE)C/PCL/DCA solutions, at which the mesophase began to appear, was not influenced by the addition of PCL molecules, and the evolution of the cholesteric texture varied with different contents of PCL in the blends. Spherulites with a ringed extinction pattern in the (ECE)C/PCL blending films were formed below an (ECE)C concentration of 25 wt %. Moreover, the bright band distance of the alternative ringed extinction pattern decreased with increasing (ECE)C concentration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 550–554, 2004

Miscibility, melting, and crystallization of poly(butylene‐2,6‐naphthalate)/poly(ether imide) blends

AbstractWe prepared blends of poly(butylene‐2,6‐naphthalate) (PBN) and poly(ether imide) (PEI) by solution‐casting from dichloroacetic acid solutions. The miscibility, crystallization, and melting behavior of the blends were investigated with differential scanning calorimetry (DSC) and dynamic mechanical analysis. PBN was miscible with PEI over the entire range of compositions, as shown by the existence of single composition‐dependent glass‐transition temperatures. In addition, a negative polymer–polymer interaction parameter was calculated, with the Nishi–Wang equation, based on the melting depression of PBN. In nonisothermal crystallization investigations, the depression of the crystallization temperature of PBN depended on the composition of the blend and the cooling rate; the presence of PEI reduced the number of PBN segments migrating to the crystallite/melt interface. Melting, recrystallization, and remelting processes occurring during the DSC heating scan caused the occurrence of multiple melting endotherms for PBN. We explored the effects of various experimental conditions on the melting behavior of PBN/PEI blends. The extent of recrystallization of the PBN component during DSC heating scans decreased as the PEI content, the heating rate, the crystallization temperature, and the crystallization time increased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1694–1704, 2004

Electrochemically generated deformations of polyaniline film plasticized with di-2-butoxy-2-ethoxy-ethyl ester of sulfosuccinic acid

Characteristics of electrochemomechanical deformation (ECMD) have been investigated for polyaniline films doped with a bulky dopant, namely the anion of di-2-butoxy-2-ethoxy-ethyl ester of sulfosuccinic acid (PANI/DBEEESSA/SCCA), in which the films were cast from dichloroacetic acid solution. The results were compared with those obtained for PANI, emeraldine base form, films processed from N-methyl-2-pyrrolidone (PANI/NMP). ECMD behaviors in both films have been evaluated as a function of electrolyte, pH, load and temperature. PANI/DBEEESSA/SCCA film exhibits the anodic expansion during redox process similar to that in PANI/NMP film despite the bulky structure of DBEEESSA as dopant. The results are discussed with the mechanisms based on the insertion of anions, the conformation change of polymer matrix and bulky dopant as well as other possible origins.

Studies on the inhibition of aluminium corrosion by 2‐acetylphenothiazine in chloroacetic acids

The inhibition of corrosion of aluminium in chloroacetic acids, namely monochloroacetic acid (MCA), dichloroacetic acid (DCA) and trichloroacetic acid (TCA) solutions, using 2‐acetylphenothiazine (2APTZ) at 30 and 40°C, at concentrations of 1×10−3M, 1×10−4M, 7.5×10−5M, 5×10−5M and 1×10−5M, was studied using the weight loss and hydrogen evolution techniques. At the highest concentration studied, using the hydrogen evolution technique, an inhibition efficiency of 86.16 per cent was obtained. The investigation revealed that 2APTZ inhibited the corrosion reaction. A physical adsorption mechanism is proposed on the basis of the obtained average Ea values of 76.05 kJ/mol for MCA, 70.75 kJ/mol for DCA and 68.52 kJ/mol for TCA. 2APTZ was confirmed to obey the Freundlish adsorption isotherm equation at the concentration studied. The two techniques employed revealed a first‐order kinetics.

Low-Frequency Modes of Peptides and Globular Proteins in Solution Observed by Ultrafast OHD-RIKES Spectroscopy

The low-frequency (1–200cm−1) vibrational spectra of peptides and proteins in solution have been investigated with ultrafast optical heterodyne-detected Raman-induced Kerr-effect spectroscopy (OHD-RIKES). Spectra have been obtained for di-L-alanine (ALA(2)) and the α-helical peptide poly-L-alanine (PLA) in dichloroacetic acid solution. The poly-L-alanine spectrum shows extra amplitude compared to the di-L-alanine spectrum, which can be explained by the secondary structure of the former. The globular proteins lysozyme, α-lactalbumin, pepsin, and β-lactoglobulin in aqueous solution have been studied to determine the possible influence of secondary or tertiary structure on the low-frequency spectra. The spectra of the globular proteins have been analyzed in terms of three nondiffusive Brownian oscillators. The lowest frequency oscillator corresponds to the so-called Boson peak observed in inelastic neutron scattering (INS). The remaining two oscillators are not observed in inelastic neutron scattering, do therefore not involve significant motion of hydrogen atoms, and may be associated with delocalized backbone torsions.

Conformational properties of macromolecules of heterocyclic polyester imides in dilute dichloroacetic acid solutions

Several series of polyester imides (PEIs) were prepared by melt polycondensation of trimellitimidobenzoic acid and acetylated, substituted hydroquinones as well as by solution polycondensation of corresponding dichlorides with hydroquinones. The influence of either phenyl- or tert-butyl substituents at the hydroquinone unit on the hydrodynamic (diffusion and viscometry) and optical [flow (FB) and electrical (EB) birefringence] properties of solutions of these PEIs were investigated. Independent methods for quantitative evaluation of the length of the statistical Kuhn segment A gave values of 14.5 nm (translational friction and electrical birefringence) and 12.0 nm (flow birefringence), respectively. The equilibrium rigidity of PEIs with phenyl and tert-butyl lateral substituents at the para-aromatic chain fragment was comparable. Conformational properties of the PEIs were analyzed, and the conjugation energies of the ester and amide groups for para-aromatic polyesters, PEIs, and structurally similar polyamidobenzoxazoles and polyamidobenzimidazoles were compared. The introduction of the phthalimide ring leads to a decrease of conjugation energy and deviation of the ester group from coplanarity. The Kuhn segment values obtained were useful for calculations of phase diagrams of semiflexible segmented block copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 12–24, 2004

Time-resolved optical Kerr-effect spectroscopy of low-frequency dynamics in Di-L-alanine, poly-L-alanine, and lysozyme in solution.

The low-frequency spectra of peptides and proteins in solution have been investigated with optical heterodyne-detected Raman-induced Kerr-effect spectroscopy. Spectra were obtained for di-l-alanine ALA(2) and poly-l-alanine (PLA) in dichloroacetic acid solution. The conformational dependence of those spectra at low frequency has been analyzed. ALA(2) displays a band centered at 50 cm-1, whereas the alpha-helical PLA shows two shoulders at 60 and 140 cm-1. The similarity of the spectral features observed in PLA to those in water can be explained by analogous acoustic translational modes in the hydrogen network of the PLA alpha-helix. The mostly alpha-helical protein lysozyme in aqueous solution has also been investigated and showed significantly more structure with modes at 10, 35, 73, 106, and 164 cm-1.

Influence of degree of molar etherification on critical liquid crystal behavior of hydroxypropyl chitosan

Hydroxypropyl chitosan (HPCS) with different degree of molar etherification (DME, from 0.6 to 6.0) were synthesized and characterized by FTIR, 1H-NMR and elemental analysis. The effect of DME on critical concentration forming lyotropic liquid crystal ( C *) was investigated in three solvents (formic acid, dichloroacetic acid and water). C * increased as DME raised but presented a platform at low DME (less than about 2.6), which was explained based on both the amount and the size of flexible substituents. HPCS with DME ⩾3.2 were water soluble. C * of HPCS aqueous solutions were evidently lower than those of formic acid or dichloroacetic acid solutions. Typical cholesteric texture appeared in HPCS solutions of all three solvents at proper concentrations.

Sistema de injeção em fluxo espectrofotométrico para monitorar peróxido de hidrogênio em processo de fotodegradação por reação foto-Fenton

Fenton processes (Fe 2+ /H2O2/UV). Sample is injected manually in a carrier stream and then receives by confluence a 0.1 mol L -1 NH4VO3 solution in 0.5 mol L -1 H 2SO4 medium. The product formed shows absorption at 446 nm which is recorded as a peak with height proportional to H 2O2 concentration. The performance of the proposed system was evaluated by monitoring the consumption of H2O2 during the photodegradation of dichloroacetic acid solution by foto-Fenton reaction.

Solvent extraction of lanthanides with triisoamylphosphate and di-(2-ethylhexyl)phosphoric acid from trichloroacetic acid and nitric acid solutions

The study on solvent extraction of some rare earth elements with triisoamyl phosphate (TiAP) and a mixture of TiAP and di-(2-ethylhexyl)phosphoric acid (D2EHPA) from trichloroacetic acid and nitric acid solutions has been carried out. It was found that Y has been more effectively extracted with TiAP from the trichloroacetic acid solution than from the mono and dichloroacetic acid solutions. The influence of various factors such as acid, RE and salting-out agent concentrations on the distribution ratio has been studied. The synergistic extraction effects were observed for low trichloroacetic acid and high nitric acid concentrations. The influence of the TiAP–D2EHPA ratio and the total concentration of two extractants, as well as acid concentration on the synergistic extraction ratio has been investigated. RE extraction isotherms by TiAP and D2EHPA alone and by a mixture of these extractants in the above extraction systems were established.

Evaluation of two solar pilot scale fixed-bed photocatalytic reactors

Two large pilot scale fixed-bed photocatalytic reactor designs are evaluated by assessing the processing rate for 2 mg l −1 phenol solutions. Taking into account total volume treated and reactor surface area, processing rates for the packed-bed and coated-mesh reactors were 140 mg m −2 h −1 and 20 mg m −2 h −1, respectively. The significantly lower degree of removal for the coated-mesh reactor is attributed to insufficient surface contact times, low levels of available attached TiO 2 and a small reactor to tank volume ratio. In the absence of any time dependent UV intensity data, irradiation intensity was estimated from daily global irradiation data assuming a Gaussian distribution. Photonic efficiencies for removal of 100 mg −1 dichloroacetic acid solutions using the packed-bed reactor are only 40% lower than ideal suspension systems suggesting that fixed-bed photocatalysis is highly suitable for degradation of contaminated water.

A study of conformational stability of polyglycine and poly(L-alanine), and polyglycine/poly(L-alanine) blends in the solid state by (13)C cross-polarization/magic angle spinning NMR.

13C Cross-Polarization/Magic Angle Spinning nmr and T(1rhoH) experiments of polyglycine (PG), poly(L-alanine) (PLA), and PG/PLA blends prepared from dichloroacetic acid solution have been carried out, in order to elucidate the conformational stability of these polypeptides in the solid state. From these experimental results, it was clarified that the conformations of PG and PLA in their blends are strongly influenced by intermolecular hydrogen-bonding interactions that cause their miscibility at the molecular level.

Poly(l-alanylglycine): Multigram-Scale Biosynthesis, Crystallization, and Structural Analysis of Chain-Folded Lamellae

The biosynthesis of poly(l-alanylglycine) (poly(AG)) was performed in high cell density cultures of recombinant Escherichia coli. The purity of the material was determined by amino acid analysis, elemental analysis, and 1H NMR spectroscopy. Fed batch fermentation increased the yield of recombinant protein from levels of tens of milligrams per liter (typical of batch fermentation in rich media) to hundreds of milligrams per liter. Poly(AG) comprising 64 diads [(AG)64] was recrystallized from dichloroacetic acid solutions in the form of texture-oriented chain-folded lamellae with a lamellar stack periodicity of 3.2 nm. The crystal structure within the lamellar core is similar in general, but different in detail, to the antiparallel β-sheet structure previously reported for oriented films of poly(AG) and fibers of Bombyx mori silk fibroin (silk II). The structure consists of polar antiparallel (ap) β-sheets, with repetitive folding through γ-turns every eighth amino acid (including the fold), stacking with like surfaces together. The wide-angle X-ray diffraction signals index on an orthorhombic unit cell with a (hydrogen bond direction) = 0.948 nm, b (sheet stacking direction) = 0.922 nm, and c (chain direction) = 0.695 nm. The stacking distance (b-value) is increased by about 3% in comparison with the previously reported structure of poly(AG), owing, we believe, to steric interaction at the lamellar fold surfaces. Random shears of approximately ±a/4 and shears of ±c/2 in the ac plane are required to obtain a good fit between the calculated and measured X-ray structure factors.

X‐ray diffraction studies on the cross‐β form of poly (O‐benzyl‐L‐serine)

AbstractPoly(O‐benzyl‐L‐serine) of degree. polymerization 90 in oriented film cast from dichloroacetic acid (DCA) solution yielded the x‐ray patterns of the intramolecular cross‐β form, in which the extended segments stand upward and downward to the surfaces of a thin film. These x‐ray photographs further suggest that residual solvent molecules are bound to the polymer, and it may provide an important clue in understanding the nature of the cross‐β conformation in a diluted DCA solution.