boron and perchlorate

This study investigated the potential of a novel fabricated black phosphorus (BP) nanoparticle electrode as an alternative to noble metal-based catalysts for application in electrolysis. The BP electrode was compared with other conventional catalysts (boron-doped diamond (BDD) and a dimensional stable electrode (DSA)) under different electrolyte conditions for the generation of specific oxidants (e.g., OH

Topics: Boron; Chlorine; Diamond; Electrodes; Electrolysis; Oxidants; Oxidation-Reduction; Perchlorates; Phosphorus; Sulfates; Water Pollutants, Chemical

Formation of chlorate (ClO

Topics: Boron; Chlorates; Diamond; Electrodes; Hydrogen Peroxide; Methanol; Oxidation-Reduction; Perchlorates; Titanium; Water Pollutants, Chemical

In this work, the valorization of brines, with concentrations similar to those produced by reverse osmosis or electrodialysis processes, by electrolysis with diamond anodes is evaluated. To do this, synthetic brines made from solutions of NaCl (with target concentrations ranging from 1.0 to 2.0 M and an additional test at 5.0 M) were used as the raw material for the electrochemical production of perchlorate using commercial electrochemical cells equipped with boron-doped diamond (BDD) anodes. The effect of key parameters on the rate and efficiency of perchlorate production was evaluated. The results show that it is possible to transform more than 80% of the initial chloride concentration into perchlorate, with current efficiencies higher than 70% regardless of the initial concentration of sodium chloride contained in the brine. Moreover, it was observed that both hypochlorite and chlorate were produced almost simultaneously at the beginning of electrolysis, while perchlorate was only produced when a certain value of applied electric charge was passed through the system. The results obtained were essentially independent of the concentration of NaCl, as the high concentrations used in this study avoided mass transfer limitations. Moreover, the specific energy cost of perchlorate production was estimated to range from 26.14 kWh kg

Topics: Boron; Electrochemical Techniques; Electrodes; Electrolysis; Perchlorates; Salts

Chlorination byproducts (CBPs) are harmful to human health and the environment. Their formation in chlorine mediated electro-oxidation is a concern for electrochemical urine treatment. We investigated the formation of chlorate, perchlorate, and organic chlorination byproducts (OCBPs) during galvanostatic (10, 15, 20 mA · cm(-2)) electro-oxidation of urine on boron-doped diamond (BDD) and thermally decomposed iridium oxide film (TDIROF) anodes. In the beginning of the batch experiments, the production of perchlorate was prevented by competing active chlorine and chlorate formation as well as by direct oxidation of organic substances. Perchlorate was only formed at higher specific charges (>17 Ah · L(-1) on BDD and >29 Ah · L(-1) on TDIROF) resulting in chlorate and perchlorate being the dominant CBPs (>90% of initial chloride). BDD produced mainly short chained OCBPs (dichloromethane, trichloromethane, and tetrachloromethane), whereas longer chained OCBPs (1,2-dichloropropane and 1,2-dichloroethane) were more frequently found on TDIROF. The OCBPs were primarily eliminated by electrochemical stripping: On BDD, this pathway accounted for 40% (dichloromethane) to 100% (tetrachloromethane) and on TDIROF for 90% (1,2-dichloroethane) to 100% (trichloromethane) of what was produced. A post-treatment of the liquid as well as the gas phase should be foreseen if CBP formation cannot be prevented by eliminating chloride or organic substances in a pretreatment.

Topics: Boron; Chlorates; Chlorides; Chlorine; Electrochemical Techniques; Electrodes; Ethylene Dichlorides; Halogenation; Humans; Hydrocarbons, Chlorinated; Iridium; Oxidation-Reduction; Perchlorates; Urine

Rates of ClO4(-) formation from ClO3(-) oxidation were investigated in batch experiments as a function of organic compounds (p-nitrophenol, p-benzoquinone, p-methoxyphenol, and oxalic acid) and current density using boron-doped diamond film anodes. Excluding organics, ClO4(-) formation rates ranged from 359 to 687 μmoles m(-2) min(-1) for current densities of 1-10 mA cm(-2). The presence of p-substituted phenols inhibited ClO4(-) formation rates between 13.0 and 99.6%. Results from a reactive-transport model of the diffuse layer adjacent to the anode surface indicate that competition between organics and ClO3(•) for OH(•) within a reaction zone (0.02-0.96 μm) adjacent to the anode controls ClO4(-) formation. Under kinetic-limited conditions (1.0 mA cm(-2)), organics reach the anode surface and substrates with higher OH(•) reaction rates demonstrate greater inhibition of perchlorate formation (IPF). At higher current densities (10 mA cm(-2)), organic compound oxidation becomes mass transfer-limited and compounds degrade a small distance from the anode surface (∼ 0.26 μm for p-methoxyphenol). Therefore, OH(•) scavenging does not occur at the anode surface and IPF values decrease. Results provide evidence for the existence of desorbed OH(•) near the anode surface and highlight the importance of controlling reactor operating conditions to limit ClO4(-) production during anodic treatment of organic compounds.

Topics: Boron; Computer Simulation; Diamond; Electrochemical Techniques; Electrodes; Kinetics; Models, Theoretical; Organic Chemicals; Perchlorates

This research investigated the mechanism of perchlorate (ClO(4)(-)) formation from chlorate (ClO(3)(-)) on boron-doped diamond (BDD) film anodes by use of a rotating disk electrode reactor. Rates of ClO(4)(-) formation were determined as functions of the electrode potential (2.29-2.70 V/standard hydrogen electrode, SHE) and temperature (10-40 °C). At all applied potentials and a ClO(3)(-) concentration of 1 mM, ClO(4)(-) production rates were zeroth-order with respect to ClO(4)(-) concentration. Experimental and density functional theory (DFT) results indicate that ClO(3)(-) oxidation proceeds via a combination of direct electron transfer and hydroxyl radical oxidation with a measured apparent activation energy of 6.9 ± 1.8 kJ·mol(-1) at a potential of 2.60 V/SHE. DFT simulations indicate that the ClO(4)(-) formation mechanism involves direct oxidation of ClO(3)(-) at the BDD surface to form ClO(3)(•), which becomes activationless at potentials > 0.76 V/SHE. Perchloric acid is then formed via the activationless homogeneous reaction between ClO(3)(•) and OH(•) in the diffuse layer next to the BDD surface. DFT simulations also indicate that the reduction of ClO(3)(•) can occur at radical sites on the BDD surface to form ClO(3)(-) and ClO(2), which limits the overall rate of ClO(4)(-) formation.

Topics: Boron; Diamond; Electrodes; Environmental Restoration and Remediation; Oxidation-Reduction; Perchlorates; Water Pollutants, Chemical