Formation Of Cl Research Articles

Activating Magnesium Electrolytes through Chemical Generation of Free Chloride and Removal of Trace Water.

Mg batteries are attractive next-generation energy storage systems due to their high natural abundance, inexpensive cost, and high theoretical capacity compared to conventional Li-ion based systems. The high energy density is achieved by electrodeposition and stripping of a Mg metal anode and requires the development of effective electrolytes enabled by a mechanistic understanding of the charge-transfer mechanism. The magnesium aluminum chloride complex (MACC) electrolyte is a good model system to study the mechanism as the solution phase speciation is known. Previously, we reported that minor addition of Mg(HMDS)2 to the MACC electrolyte causes significant improvement in the Mg deposition and stripping voltammetry resulting in good Coulombic efficiency on cycle one and, therefore, negating the need for electrochemical conditioning. To determine the cause of the improved electrochemistry, here we probe the speciation of the electrolyte after Mg(HMDS)2 addition using Raman spectroscopy, 27Al nuclear magnetic resonance spectroscopy, and 1H-29Si heteronuclear multiple bond correlation spectroscopy on MACC + Mg(HMDS)2 at various Mg(HMDS)2 concentrations. Mg(HMDS)2 scavenges trace H2O, but it also reacts with MACC complexes, namely, AlCl4-, to form free Cl-. We suggest that although both the removal of H2O and the formation of free Cl- improve electrochemistry by altering the speciation at the interface, the latter has a profound effect on electrodeposition and stripping of Mg.

Performance evaluation of urea injection on the emission reduction of dioxins and furans in a commercial municipal solid waste incinerator

Polychlorinated dibenzo-p-furans and dioxins (PCDD/Fs) that pose a great threat to human health are commonly found during the incineration of municipal solid waste. In this study, industrial urea was injected into a commercial MSW incinerator flue gas to evaluate the suppression performances of PCDD/Fs, and the possible inhibition mechanisms were proposed. The results show that the use of urea dramatically reduced the PCDD/Fs emission concentration from 8.87 to 0.63ng/Nm3, along with a significant decrease in the I-TEQ value (0.26 → 0.047ng I-TEQ/Nm3), below the Chinese national standard of 0.1ng I-TEQ/Nm3. The emission reduction cost of the industrial urea was over 41 % lower than that of using activated carbon. Urea molecule poisoned the metal ions, thus seriously inhibiting the de novo synthesis of PCDD/Fs. Furthermore, the decomposition products of urea reduced the concentration of HCl in the flue gas, thereby reducing the formation of Cl2 and hindering the chlorination reaction, which was identified from the reduction of chlorination degree and lower distribution of high-chlorinated PCDD/Fs. This research provided some practice basis and experience to reduce the emission of PCDD/Fs from municipal solid waste incineration for future commercial promotion and application.

Role of Carbonate Species on General Acid Catalysis of Bromide Oxidation by Hypochlorous Acid (HOCl) and Oxidation by Molecular Chlorine (Cl2).

Kinetic models for disinfectant decay and disinfection byproduct (DBP) formation are necessary for predicting water quality from the treatment plant to the tap. A kinetic model for conditions relevant to chloramine disinfection of drinking water (pH 6-9 and carbonate-buffered) was developed to simulate incomplete bromide (Br-) oxidation during short prechlorination periods because it is the first step in a complex system of reactions that leads to disinfectant loss and DBP formation. Hypochlorous acid and molecular chlorine were the free chlorine species relevant to Br- oxidation, and Cl2 hydrolysis and formation reactions were necessary to accurately simulate Cl2 concentrations instead of assuming equilibrium. Previous work has shown that Br- oxidation by HOCl and Cl2 formation are acid-catalyzed and Cl2 hydrolysis is base-catalyzed, but the impact of carbonate species had not been studied. This work showed that the carbonate species have an enhanced catalytic impact with rate constants up to 1000 times larger than would be estimated by the Brønsted relationship for similar acids, which causes the oxidation by HOCl rate constant (kHOCl) to nearly double and oxidation by Cl2 to occur above pH 7 in high-alkalinity waters.

Free-Radical-Mediated Formation of Trans-Cardiolipin Isomers, Analytical Approaches for Lipidomics and Consequences of the Structural Organization of Membranes.

Free-radical-mediated processes, such as peroxidation, isomerization and hydrogenation affecting fatty acid integrity and biological functions, have a trans-disciplinary relevance. Cardiolipins (CL, (1,3-diphosphatidyl-sn-glycerol)) and tetra-linoleoyl-CL are complex phospholipids, exclusively present in the Inner Mitochondrial Membrane (IMM) lipids, where they maintain membrane integrity and regulate enzyme functionalities. Peroxidation pathways and fatty acid remodeling are known causes of mitochondrial disfunctions and pathologies, including cancer. Free-radical-mediated isomerization with the change of the cis CL into geometrical trans isomers is an unknown process with possible consequences on the supramolecular membrane lipid organization. Here, the formation of mono-trans CL (MT-CL) and other trans CL isomers (T-CL) is reported using CL from bovine heart mitochondria and thiyl radicals generated by UV-photolysis from 2-mercaptoethanol. Analytical approaches for CL isomer separation and identification via 1H/13C NMR are provided, together with the chemical study of CL derivatization to fatty acid methyl esters (FAME), useful for lipidomics and metabolomics research. Kinetics information of the radical chain isomerization process was obtained using γ-irradiation conditions. The CL isomerization affected the structural organization of membranes, as tested by the reduction in unilamellar liposome diameter, and accompanied the well-known process of oxidative consumption induced by Fenton reagents. These results highlight a potential new molecular modification pathway of mitochondrial lipids with wide applications to membrane functions and biological consequences.

Desorption of Cl− from Mg-Al layered double hydroxide intercalated with Cl− using CO2 gas and water

Abstract Mg-Al layered double hydroxide intercalated with CO32− (CO3·Mg-Al LDH) is effective for treating HCl exhaust gas. HCl reacts with CO32− in CO3·Mg-Al LDH, resulting in the formation of Cl·Mg-Al LDH. We propose that CO2 can be used for the desorption of Cl− from Cl·Mg-Al LDH to regenerate CO3·Mg-Al LDH. Herein, we studied the desorption of Cl− from Cl·Mg-Al LDH by adding water to Cl·Mg-Al LDH and blowing CO2 into it. We also analyzed the effects of temperature and water addition speed on the desorption of Cl− from Cl·Mg-Al LDH. Our results show that the added water adhered to Cl·Mg-Al LDH and that CO2 in the gaseous phase was dissolved in this adhered water, thus generating CO32−. Therefore, anion exchange occurred between CO32− and Cl− in the Cl·Mg-Al LDH, thus desorbing Cl−.

Adsorption of sulfur mustard on clean and water-saturated ZnO(10[formula omitted]0): Structural diversity from first-principles calculations

We investigate the adsorption of a chemical warfare agent, namely sulfur mustard (SM), on clean and water-saturated ZnO(101¯0) surfaces using density functional theory calculations to understand the first step of its efficient neutralization to less toxic chemical compounds. We determine the relative stability of various SM conformers adsorbed at different sites on both ZnO surfaces. The unique hydrogen bonding patterns obtained for the idealized clean and the more realistic water-saturated ZnO surface are analyzed and their influence on the stability of the SM@ZnO structures is demonstrated. We find that absolute values of the calculated binding and interaction energies are significantly higher for the clean than for the water-saturated ZnO surface due to the formation of Cl⋯Zn and S⋯Zn contacts. The high adsorptive reactivity of the clean ZnO surface is also evident from the strong structural changes of the initial local energy minimum gas-phase conformations of the SM molecules upon adsorption. This phenomenon is not observed for the water-saturated ZnO surface, which has almost no impact on the SM conformation after adsorption, leaving it as it exists in the gas phase. The insights from the results obtained provide a missing piece toward the understanding of the complex mechanism of SM neutralization on ZnO surfaces.

Decreasing the dose of equine chorionic gonadotropin does not affect ovarian or pregnancy responses of purebred taurine and crossbred beef heifers

In this study there was evaluation of effects of different doses of equine chorionic gonadotropin (eCG: 200, 300, or 400 IU) administrated at progesterone (P4) plus estradiol-based timed AI (TAI). A total of 1080 heifers were included in the study. There was insertion of the intravaginal P4-device plus administration of 2 mg of estradiol benzoate IM. On D7, 12.5 mg of dinoprost tromethamine IM was administered and on D9, the P4 insert was removed and 0.5 mg of estradiol cypionate IM was administered. Heifers were categorized according to Reproductive Tract Status (RTS; 1−5) and were assigned to one of three treatments: 200 IU (n = 387), 300 IU (n = 357), or 400 IU (n = 336) of eCG. Estrous occurrence was evaluated at TAI 48 h later (D11). A subset of heifers (n = 213) had the largest follicle (LF) evaluated on D9 and on D11, and the formation of a new CL evaluated on D18.There was no effect of eCG treatment on LF on D11 (P = 0.79), occurrence of estrus (P = 0.92), and pregnancy at 30 days after AI (P/AI; 52.2%, 49.8%, and 51.5% for 200 IU, 300 IU, and 400 IU, respectively; P = 0.46). Regardless of the treatment, there was a greater P/AI when heifers had a functional CL, at initiation of the estrous synchronization treatment regimen. It, therefore, is efficacious to reduce the dose of eCG to 300 or 200 IU in purebred taurine and crossbred beef heifers without negative effects on ovarian, estrous or pregnancy responses.

Conditioning-Free MgCl2/AlCl3 Electrolyte for Magnesium Batteries By Chemical Formation of Solvated Chloride

Mg metal is a promising alternative anode material that offers higher theoretical specific capacity than conventional Li-ion batteries (LIBs), and the high natural abundance of Mg makes it more economically appealing than other post-LIB anode materials. The greater energy density hinges on a Mg-metal anode, and reversible Mg electrodeposition and stripping require an effective Mg electrolyte. Various electrolyte systems that support reversible have been introduced, but many of them contain drawbacks, such as narrow electrochemical window, reactivity with electrode materials, or poor Coulombic efficiency. In addition, challenges remain in understanding the relationship between electrochemistry at the Mg anode and the electrolyte composition due to the complicated interface of Mg metal and the electrolyte.To probe the effect of the interface on Mg electrodeposition, an electrolyte with a known solution phase composition, the magnesium aluminum chloride complex (MACC) electrolyte, is explored. The MACC electrolyte undergoes electrolytic conditioning to support reversible Mg electrodeposition and stripping. During conditioning, free Cl- is released electrolytically while Al3+ is irreversibly deposited, and the concentration of the active species [Mg2(µ−Cl)3·6(THF)]+ increases, activating the MACC electrolyte.Here, we show that a small concentration of Mg(HMDS)2 to the MACC electrolyte suppresses Al3+ deposition and promotes reversible Mg electrodeposition and stripping on the first cycle. Such a drastic change from a small concentration suggests that changes are localized at the electrode-electrolyte interface. We show spectroscopically that Mg(HMDS)2 scavenges trace water in the solution. Spectroscopic results also suggest that Mg(HMDS)2 reacts with AlCl4 - in the MACC electrolyte to form free Cl-. Based on the spectroscopic and electrochemical results, we suggest that the formation of Cl- is the primary cause for improved behavior on cycle one, highlighting the role of Cl- in Mg deposition and stripping.

Highly Efficient Bromide Removal from Shale Gas Produced Water by Unactivated Peroxymonosulfate for Controlling Disinfection Byproduct Formation in Impacted Water Supplies.

Shale gas extraction processes generate a large amount of hypersaline wastewater, whose spills or discharges may significantly increase the bromide levels in downstream water supplies and result in the formation of brominated disinfection byproducts (DBPs) upon chlorination. Although a few studies have investigated selective bromide removal from produced water, the low removal efficiencies and complex system setups are not desirable. In this study, we examined a simple cost-effective approach for selective bromide removal from produced water relying on the oxidation by unactivated peroxymonosulfate. More than 95% of bromide was removed as Br2(g) in less than 10 min under weakly acidic conditions without significant formation of Cl2(g) even when the chloride concentration was more than 2 orders of magnitude higher. A kinetic model considering the involved reactions was then developed to describe the process well under various reaction conditions. The organic compounds in the produced water neither noticeably lowered the bromide removal efficiency nor reacted with the halogen species to form halogenated byproducts. The tests in batch and continuously stirred tank reactor systems suggested that it was feasible to achieve both high bromide removal and neutral effluent pH such that further pH adjustment was not necessary before discharge. After the treatment, the effect of the produced water on DBP formation was largely eliminated.

Extraction of platinum and gold from copper anode slimes by a process of chlorinating roasting followed by chlorinating leaching

A novel process of chlorinating roasting followed by chlorinating leaching to extract platinum and gold from copper anode slimes was proposed in this research. Results of thermodynamic analysis and experimental research showed that the platinum was chlorinated into PtCl2 while the gold existed in the form of metallic Au during the roasting process. With the copper anode slime being directly leached using a traditional process, the Pt recovery rate was low and came to 80.72%. After the roasting process with sodium chloride and concentrated sulfuric acid in oxygen atmosphere, the recovery rate of Pt increased to a value around 95%. Moreover, with excessive addition of concentrated sulfuric acid, more H2O (g) was generated and the formation of Cl2 (g) decreased due to the transition from HCl (g) and Cl2 (g), as a result of which the Pt recovery rate decreased. In addition, this chlorinating roasting had little effect on the Au recovery due to its difficulty to be chlorinated.

PEG assisted P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst with enhanced elimination of emerging organic pollutants in salinity condition under solar light illumination

In this study, the effect of salinity on degradation of model environmental pollutants (organic dyes and E. coli) was investigated using polyethylene glycol (PEG) assisted P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst. The photocatalyst was firstly synthesized with structure modifier PEG to determine the optimum molecular weight by sol-gel method, and was characterized by XRD, UV–Vis, PL, SEM, TEM, EDS, and photocurrent experiment. The PEG300 modified P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst was found to be the optimal molecular weight which exhibited small crystalline size, narrow band gap, better absorption ability, smaller particles size, large photocurrent density, low recombination rate and higher photocatalytic activity among other PEG modified photocatalyst. The PEG300-P/Ag/Ag2O/Ag3PO4/TiO2 photocatalytic degradation of emerging organic pollutants such as rhodamine B, methyl orange, and methylene blue was significantly higher at aqueous NaCl (2.6 and 3.2 wt%) and artificial salinity (25 and 35‰) compared to freshwater under simulated solar light illumination. Furthermore, the elimination of organic dyes under different environmental factors such as initial pH, light intensity, reaction temperature showed substantial degradation in real environmental conditions at salinity. Moreover, PEG300-P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst demonstrated high practicability on complete inactivation of E. coli, simultaneous degradation of organic dyes, and high stability in seawater. Superoxide anion (O2−) radicals was found to be the dominant reactive species, and subsequent formation of Cl and free chlorine oxidative agents further improved the photocatalytic purification process. The PEG300-P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst showed great potential in treating environmental organic pollutants at salinity condition under solar light illumination.

Electro-oxidation process assisted by solar energy for the treatment of wastewater with high salinity

Industrial wastewaters characterized by its high content in organics and conductivity entails a challenge for conventional treatments due to its low biodegradability. Electro-oxidative processes have been successfully applied for the treatment of this kind of wastewaters achieving high organics and ammonia removal. The degradation process is executed mainly by electrochemically generated active chlorine species, as HClO and ClO− with E0 = 1.49 V; and E0 = 0.89 V, respectively. Under solar radiation, specifically at 313 nm, the formation of Cl (E0 = 2.4 V) from ClO− is promoted, improving the oxidizing capacity of the process. In this work the combination of an electrochemical device with a solar photo-reactor has been evaluated aiming to increase the degradation rate per kWh−1. Two different complex industrial wastewaters were tested, achieving higher organics degradation when electrochemical treatment was assisted by solar light. Toxicity reduction was also assessed and biodegradability enhanced and allowing its ulterior lower-cost biological treatment.

Elucidating Ionic Correlations Beyond Simple Charge Alternation in Molten MgCl2-KCl Mixtures.

The development of technologies for nuclear reactors based on molten salts has seen a big resurgence. The success of thermodynamic models for these hinges in part on our ability to predict at the atomistic level the behavior of pure salts and their mixtures under a range of conditions. In this letter, we present high-energy X-ray scattering experiments and molecular dynamics simulations that describe the molten structure of mixtures of MgCl2 and KCl. As one would expect, KCl is a prototypical salt in which structure is governed by simple charge alternation. In contrast, MgCl2 and its mixtures with KCl display more complex correlations including intermediate-range order and the formation of Cl--decorated Mg2+ chains. A thorough computational analysis suggests that intermediate-range order beyond charge alternation may be traced to correlations between these chains. An analysis of the coordination structure for Mg2+ ions paints a more complex picture than previously understood, with multiple accessible states of distinct geometries.

Fluid Structure of Molten LiCl-Li Solutions.

Molten mixtures of lithium chloride and metallic lithium (LiCl-Li) play an essential role in the electrolytic reduction of various metal oxides. These mixtures possess unique high temperature physical and chemical properties that have been investigated for decades. However, due to their extreme chemical reactivity, no study to date has been capable of definitively proving the basic physical nature of Li dissolution in molten LiCl. In this study, the evolution of the structure of molten LiCl-Li is probed as metallic Li is electrochemically introduced into the melt in situ, using synchrotron radiation experiments based on high energy wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). The time-resolved scattering results indicate the formation of transient Cl- ion cages surrounding low-density voids with a periodicity of ∼8.3 Å, which suggests the formation of metastable Li nanocluster. The structure of the LiCl-Li nanoclusters in the solution is modeled using ab initio molecular dynamics (AIMD) simulations. The simulation results are in agreement with the X-ray diffraction measurement and suggest the nanoclusters are predominantly Li8, along with smaller clusters.

Aqueous Chlorination Kinetics of Cyclic Alkenes-Is HOCl the Only Chlorinating Agent that Matters?

Although Cl2 and Cl2O have been recognized as highly reactive constituents of free available chlorine (FAC), robust rate constants for Cl2 and Cl2O remain scarce in the environmental literature. In this work, we explored the chlorination kinetics of three structurally related alkenes (α-ionone, β-ionone, and dehydro-β-ionone), a class of compounds whose reactivities with Cl2 and Cl2O have not been previously investigated. Second-order rate constants for Cl2, Cl2O, and HOCl were computed from experimental rate constants obtained at various pH values, [Cl-], and [FAC]. Our results show that while HOCl is the predominant chlorinating agent for the most reactive alkene, Cl2 and Cl2O can dominate the chlorination kinetics of the less reactive alkenes at high [Cl-] and high [FAC], respectively. The tradeoff between overall reactivity with FAC and selectivity for Cl2 and Cl2O previously observed for aromatic compounds also applies to the alkenes examined. In laboratory experiments in which high [FAC] may be used, omission of Cl2O in data modeling could yield second-order rate constants of dubious validity. In chlorinating real waters with elevated [Cl-], formation of Cl2 may enhance the formation kinetics of chlorinated disinfection byproducts (DBPs) and exacerbate the burden of DBP control for water utilities.

Observational Constraints on the Formation of Cl2 From the Reactive Uptake of ClNO2 on Aerosols in the Polluted Marine Boundary Layer

AbstractWe use observations from the 2015 Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) aircraft campaign to constrain the proposed mechanism of Cl2 production from ClNO2 reaction in acidic particles. To reproduce Cl2 concentrations observed during WINTER with a chemical box model that includes ClNO2 reactive uptake to form Cl2, the model required the ClNO2 reaction probability, γ (ClNO2), to range from 6 × 10−6 to 7 × 10−5, with a mean value of 2.3 × 10−5 (±1.8 × 10−5). These field‐determined γ (ClNO2) are more than an order of magnitude lower than those determined in previous laboratory experiments on acidic surfaces, even when calculated particle pH is ≤2. We hypothesize this is because thick salt films in the laboratory enhanced the reactive uptake ClNO2 compared to that which would occur in submicron aerosol particles. Using the reacto‐diffusive length‐scale framework, we show that the field and laboratory observations can be reconciled if the net aqueous‐phase reaction rate constant for ClNO2 (aq) + Cl‐(aq) in acidic particles is on the order of 104 s−1. We show that wet particle diameter and particulate chloride mass together explain 90% of the observed variance in the box model‐derived γ (ClNO2), implying that the availability of chloride and particle volume limit the efficiency of the reaction. Despite a much lower conversion of ClNO2 into Cl2, this mechanism can still be responsible for the nocturnal formation of 10–20 pptv of Cl2 in polluted regions, yielding an atmospherically relevant concentration of Cl atoms the following morning.

Individual impact of several impurities on the performance of direct internal reforming biogas solid oxide fuel cell using W-Ni-CeO2 as anode

Direct feeding of biogas to SOFC is theoretically feasible. However, several contaminants such as ammonia, siloxanes and chlorine compounds included in biogas can cause severely damage in the SOFC components. In this paper, the individual impact of 500 ppm NH3, 1 ppm D4 siloxanes and 250 ppm HCl on the performance of a single SOFC with W-Ni-Ce as anode directly fed by biogas has been investigated. Two singles cells (W-Ni-Ce/SDC/LSCF) were fabricated and tested at 750 °C. The first one was exposed to biogas with NH3 or siloxanes, and the second one to biogas with HCl. The electrochemical behaviour of cells was studied by I-V curves, impedance spectra, and under load demand in biogas with and without impurities. Post-test analyses of the anode/electrolyte interface were performed by SEM-EDS. The results showed that ammonia did not impact on the cell performance, whereas the presence of D4 siloxane caused the cell degradation by the formation of silica in the anode but the degradation rate is slower than SOFC with Ni-YSZ anode. The presence of HCl in biogas gave rise to important oscillations in the potential, and a performance loss under load demand that is probably due to adsorption-desorption processes of Cl on Ni and Ce surfaces. In addition, the presence of CO2 and H2O could improve the oxidation of Ni and CeO2-x reducing their catalytic activity; a severe corrosion in the stainless steel tubing and valves was also detected. Post-tests analysis suggested the formation of SiO2 deposits and Cl adsorbed on Ni and Ce particles.

Dissociative electron attachment to 2-chlorotoluene: Unusual temperature effects for the formation of Cl−

Dissociative electron attachment to 2-chlorotoluene has been studied experimentally. The formed Cl− fragment appears in the energy range from 0 to 2 eV. Increasing the temperature of the target molecule results in a decrease of the height of the threshold peak (∼0 eV) but in a considerable increase of the height of the second peak at 0.78 eV. Such behaviour was observed only rarely and does not occur in similar molecules. We have analysed the out-of-plane vibrations and calculated approximate potential energy curves for the neutral and anionic states. Possible explanations of the observed temperature dependence are discussed.

Photoreduction of CCl3F in aqueous solutions containing sulfonated poly(ether etherketone) and formate buffers

Irradiation of aqueous solutions containing the sodium salt of sulfonated poly(ether etherketone) and HCO2H/HCO2− buffers with 350 nm photons induced photoreduction of CCl3F to CHCl2F and Cl−. In situ determinations of chloride ion concentrations enabled evaluation of the quantum yield, ϕ(Cl−), which amounted to 0.46 in air-free, neutral solutions. A delayed formation of F− was noticed with a quantum yield of 0.18 probably due to a secondary transformation. High concentrations of the halide ions inhibited somewhat the photoreduction, whereas phase-separated CFC droplets increased the reaction rate. Despite the high quantum efficiencies obtained, no post-irradiation formation of Cl− occurred. This observation together with other findings indicated that a chain process was not involved in the transformation. Most of the kinetic features of the photoreaction are explained in terms of a mechanism involving radicals of the reactants and of the polymer. Efficient photoreductions of CCl3F also took place in sulfonated poly(ether etherketone) solutions containing air.

Postovulatory treatment with GnRH on day 5 reduces pregnancy loss in recipients receiving an in vitro produced expanded blastocyst

The present study tested the hypothesis that administration of GnRH on day 5 of the estrous cycle in embryo transfer (ET) recipients would increase progesterone (P4) concentrations, embryo size, and improve fertility. Holstein and cross-bred Holstein heifers (n = 1562) were synchronized using a modified 5-day CIDR-Synch protocol as follows (All AM treatments): D-8, CIDR inserted; D-3, CIDR removed and PGF2α (500 μg cloprostenol) treatment; D-2, second PGF2α; D0, GnRH (G1, 100 μg gonadorelin acetate) to induce ovulation. On D5 in the afternoon, heifers were assigned in a completely randomized design to one of two treatments: Control (untreated) or GnRH (200 μg). Transfer of day 7 fresh IVP embryos was performed between D6 and D8 after G1. Data collected from each heifer included: embryo stage and quality, body condition score, technician performing ET, interval from G1 to ET, and number of previous transfers. All heifers were evaluated by transrectal ultrasonography on D5, D33, and D60 and a subset of heifers was scanned on D12 (n = 718; to determine ovulation to treatment) and another subset on D33 (n = 295; 16 s video to determine embryo and amniotic vesicle size). Serum P4 was determined from a subset of heifers on D12 (n = 467) and on D21 (n = 837) and pregnancy specific protein B (PSPB) on D28 (n = 843). Pregnancies per ET (P/ET) were analyzed by logistic regression and continuous outcomes by ANOVA. Ovulation to D5 GnRH, defined by the presence of an accessory CL on D12, was 83.9% (302/360) in GnRH-treated heifers vs. 3.3% (12/358) in Controls (P < 0.001). On D12, P4 was greater (P < 0.001) in GnRH-treated heifers (7.2 ± 0.1 ng/ml) vs Controls (6.0 ± 0.1 ng/ml). There was greater P/ET at D33 and D60 of pregnancy for Stage 7 than Stage 6 embryos. Treatment with GnRH did not alter P/ET with either embryo stage but decreased pregnancy loss between D33 and D60 in heifers receiving Stage 7 embryos. Presence of an accessory CL at the D33 pregnancy diagnosis was associated with a larger reduction in pregnancy loss from D33 to D60 in recipients of Stage 7 embryos (11.6 vs 27.6%). Although there was no GnRH effect on embryo size, the presence of an accessory CL was associated (P < 0.05) with larger amniotic vesicle volume in recipients of Stage 7 embryos. In addition, greater PSPB was linked to greater amniotic vesicle volume (P = 0.01) and to reduced pregnancy loss (P < 0.0001). In conclusion, treatment with GnRH on D5 caused ovulation and formation of an accessory CL, increased circulating P4, and reduced pregnancy loss in heifers receiving a Stage 7 but not a Stage 6 IVP embryo.