Effect of Formic Acid on Pollutant Decomposition in Textile Wastewater Subjected to Treatment by the Fenton Method

The aim of this research was to determine the effect of formic acid on pollutant decomposition in textile wastewater subjected to treatment by the Fenton method. To estimate the effect of formic acid on treatment efficiency for different types of textile wastewater tested, COD reduction in mixtures of wastewater and formic acid was calculated. The values of COD calculated were then compared with COD values obtained experimentally during the oxidation of samples of wastewater-formic acid mixtures in the Fenton process. It was found that the presence of formic acid did not deteriorate the conditions of wastewater treatment in the Fenton process. Thus the presence of formic acid in textile wastewater is more advantageous than that of acetic acid

Development of covalent triazine frameworks as heterogeneous catalytic supports

Covalent triazine frameworks (CTFs) are established as an emerging class of porous organic polymers with remarkable features such as large surface area and permanent porosity, high thermal and chemical stability, and convenient functionalization that promotes great potential in heterogeneous catalysis. In this article, we systematically present the structural design of CTFs as a versatile scaffold to develop heterogeneous catalysts for a variety of chemical reactions. We mainly focus on the functionalization of CTFs, including their use for incorporating and stabilization of nanoparticles and immobilization of molecular complexes onto the frameworks

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Department of Chemical EngineeringUtilizing carbon dioxide to valuable chemicals is attractive technology for reducing CO2 emission. Among the chemicals converted from CO2, formic acid is one of the most valuable chemicals. Efficient conversion of CO2 to formic acid by electro-biocatalytic system was reported without expensive cofactor and noble metals. In this study, Shewanella oneidensis MR-1 (S. oneidensis MR-1) and encapsulated Formate dehydrogenase1 from Methylobacterium extorquens AM1 (MeFDH1) were applied to electro-biocatalytic reaction as a whole cell and encapsulated biocatalyst, respectively. First, S. oneidensis MR-1, when aerobically grown in Luria-Bertani (LB) medium, exhibited its ability for the conversion of CO2 into formic acid with productivity of 0.59 mM???hr-1 for 24 hr. In addition, CO2 reduction reaction catalyzed by S. oneidensis MR-1, when anaerobically grown in newly optimized LB medium supplemented with fumarate and nitrate, exhibited 3.2-fold higher productivity (1.9 mM???hr-1 for 72 hr). Second, previous study has demonstrated that electro-biocatalytic conversion of CO2 to formic acid by engineered MeFDH1 shows higher productivity than wild type. To increase physical strength, stability, reusability of MeFDH1, MeFDH1 was encapsulated in pure alginate and alginate silica hybrid beads. Michaelis-Menten kinetic constants demonstrated that binding affinity and maximum reaction rate of both encapsulated MeFDH1 were declined. Compared with pure alginate beads (5.4%), alginate-silica hybrid beads (67.4%) exhibited more higher recycling productivity after 4 cycles. These results show that the immobilization of MeFDH1 through encapsulation of by alginate-silica hybrid is a more suitable method to recycle formate production and prevent leakage of MeFDH1.ope

Effects of the anion adsorption and pH on the formic acid oxidation reaction on Pt(111) electrodes

The effects of solution pH and anion adsorption for the formic acid oxidation reaction on the Pt(111) electrode have been examined using electrochemical techniques. Regarding the pH effects, it has been found that oxidation currents for this reaction increase with pH, which indicates that solution formate is involved in the reaction mechanism. Unexpectedly, the adsorption of sulfate on the Pt(111) electrode has a positive effect on the oxidation of formic acid, which also suggests that adsorbed anions are also involved in the mechanism. The activation energy calculated from temperature dependent measurements diminishes with the solution pH and also in the presence of adsorbed sulfate. These measurements corroborate the involvement of solution formate and anions in the oxidation mechanism. Using these results, a rate equation for the oxidation of formic acid is proposed. The current values calculated from this equation are in very good agreement with the experimental currents in perchloric acid solutions.This work has been financially supported by the MICINN (Spain)(project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, FEDER)

Inflating hollow nanocrystals through a repeated Kirkendall cavitation process.

The Kirkendall effect has been recently used to produce hollow nanostructures by taking advantage of the different diffusion rates of species involved in the chemical transformations of nanoscale objects. Here we demonstrate a nanoscale Kirkendall cavitation process that can transform solid palladium nanocrystals into hollow palladium nanocrystals through insertion and extraction of phosphorus. The key to success in producing monometallic hollow nanocrystals is the effective extraction of phosphorus through an oxidation reaction, which promotes the outward diffusion of phosphorus from the compound nanocrystals of palladium phosphide and consequently the inward diffusion of vacancies and their coalescence into larger voids. We further demonstrate that this Kirkendall cavitation process can be repeated a number of times to gradually inflate the hollow metal nanocrystals, producing nanoshells of increased diameters and decreased thicknesses. The resulting thin palladium nanoshells exhibit enhanced catalytic activity and high durability toward formic acid oxidation

Gas-Phase Photodegradation of Decane and Methanol on TiO_2: Dynamic Surface Chemistry Characterized by Diffuse Reflectance FTIR

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to study illuminated TiO2 surfaces under both vacuum conditions, and in the presence of organic molecules (decane and methanol). In the presence of hole scavengers, electrons are trapped at Ti(III)–OH sites, and free electrons are generated. These free electrons are seen to decay by exposure either to oxygen or to heat; in the case of heating, reinjection of holes into the lattice by loss of sorbed hole scavenger leads to a decrease in Ti(III)–OH centers. Decane adsorption experiments lend support to the theory that removal of surficial hydrocarbon contaminants is responsible for superhydrophilic TiO2 surfaces. Oxidation of decane led to a mixture of surface-bound organics, while oxidation of methanol leads to the formation of surface-bound formic acid

Kinetics and mechanism of formic acid decomposition on Ru(001)

The steady-state rate of decomposition of formic acid on Ru(001) has been measured as a function of surface temperature, parametric in the pressure of formic acid. The products of the decomposition reaction are C0_2, H_2, CO, and H_2)0, i.e., both dehydrogenation and dehydration occur on Ru (001). A similar product distribution has been observed on Ni(110), Ni(100), Ru(100), Fe(100), and Ni(111) surfaces; whereas only dehydrogenation to C0_2 and H_2 occurs on the Cu(100), Cu(110), and Pt(111) surfaces. Only reversible adsorption and desorption of formic acid is observed on the less reactive Ag(110) surface at low temperatures, whereas the more reactive Mo(100) surface is oxidized by formic acid at low temperatures with the products of this reaction being H_2, CO, and H_(2)O (Ref. 10). We report here the confirmation of earlier observations of the occurrence of both dehydrogenation and dehydration of formic acid on Ru(001), and more importantly, we provide a detailed mechanistic description of the steady-state decomposition reaction on this surface in terms of elementary steps

Oxidation of carboxylic acids in water at IrO2-Ta2O5 and Boron Doped Diamond anodes

The electrochemical oxidation of different carboxylic acids (namely, oxalic, formic and maleic) in water at boron doped diamond (BDD) and IrO2-Ta2O5 (DSA-O2) anodes was performed to study the influence of the operative parameters and of the nature of the acid on the performances of the process. Higher abatements were obtained at BDD with respect to DSA anodes for all the selected carboxylic compounds. The rate of abatement decreased in the order oxalic > formic >> maleic at iridium anodes while an opposite trend was observed at diamond anodes (formic maleic > oxalic), thus indicating that different oxidant agents are involved at these two electrodes. Also the effect of the temperature depends on both the nature of the acid and of the anode. Higher current efficiencies were obtained when most part of the process was under the kinetic control of the oxidation reaction, i.e., when low current densities and high flow rates were imposed. High concentrations of carboxylic acids enhanced the current efficiency at all kinetic regimes