Redox Potential Values Research Articles

An Electrochemical Investigation into the Redox Properties of Push‐Pull Dibenzodioxins and Comparative Analysis with Analogous Heteroacenes

AbstractA series of dibenzodioxins containing electron push‐pull groups were synthesized using simple methods and their spectroscopic and redox behavior was studied. Electrochemical experiments were performed to measure the redox potentials of the substituted dibenzodioxins. The role of individual molecular subunits in tweaking the redox potential values was delineated by comparing them with the electrochemical properties of analogous heteroacenes. In many cases, our redox potentials were found to be comparably low with that of many well‐known heteroacenes.

Characterization of Oxidation-Reduction Potential Variations in Biological Wastewater Treatment Processes: A Study from Mechanism to Application

Oxidation-reduction potential (ORP) sensors would constitute a robust surveillance and control solution for aeration and external carbon dosing in wastewater biological treatment processes if a clear correlation exists between the ORP values and process variables (e.g., dissolved oxygen (DO), nitrate, and chemical oxygen demand (COD). In this study, ORP values and other water quality variables were analyzed, and principal component analysis (PCA) and analysis of variance were used to study the relationships between ORP and main reactive substances under anoxic conditions. Mathematical models were then established using multiple regression analysis. The results showed that under anoxic conditions, ORP was positively correlated with nitrate, DO, and COD and negatively correlated with ammonia nitrogen, phosphate, and pH. COD had a low correlation with the ORP value change. PCA showed that the mathematical model of ORP can be established by using DO, nitrate, and phosphate, for which the adjusted R² value was 0.7195. The numeric relationships among ORP, COD, and nitrate were clearly established and applied to control external carbon dosing. A precise and clear relationship between ORP and COD offers the possibility to substitute COD monitoring for process control.

Geochemical Characterization of the River Waters in the Pumqu Catchments, Central Himalayas

Pumqu is the biggest river in the Qomolangma National Natural Reserve in China. It is one of the headwaters of the river Ganges and is an important international river in southern Tibet Autonomous Region (T.A.R). However, there are a lack of systematic studies on Pumqu’s geochemical properties. In this study, water samples were collected systematically from all the river catchments in different seasons in 2021, the spatiotemporal variations of the geochemical characteristics of the catchments and their controlling factors were studied, and the overall water quality of the river was also evaluated. Overall, the results showed that the water from the Pumqu catchments was slightly alkaline, with an average pH of 8.22. The number of total dissolved solids was comparable to the other rivers on the Tibetan Plateau and showed a similar variation over the year. Affected by the natural geothermal spring water discharge, the values of oxidation reduction potential at some sampling sites were negative in the wet season. Generally, Ca2+ and HCO3− were the dominant ions. Carbonate weathering was the main factor affecting the geochemical features of the studied catchments. The results of correlation analysis showed the influence of rock weathering, glacial meltwater, geothermal water discharge and riverine physicochemical processes on the trace elements. The natural geothermal water discharge was particularly responsible for the elevated Li, which appeared in some of the sampling sites and resulted in relatively high WQI values in the sites. The overall water quality of the Pumqu catchments was excellent. This study provides first-hand information on the overall spatial and temporal span of the physicochemical characteristics and water quality of all the catchments of the river Pumqu, one of the major water systems in the central Himalayas.

Metabolic pathways and ΔpH regulation in Escherichia coli during the fermentation of glucose and glycerol in the presence of formate at pH 6.5: the role of FhlA transcriptional activator.

Escherichia coli is able to ferment mixed carbon sources and produce various fermentation end-products. In this study, the function of FhlA protein in the specific growth rate (µ), metabolism, regulation of ΔpH and proton ATPase activity was investigated. Reduced µ in fhlA mutant of ∼25% was shown, suggesting the role of FhlA in the growth process. The utilization rate of glycerol is decreased in fhlA ∼ 2 fold, depending on the oxidation-reduction potential values. Bacteria regulate the activity of hydrogenase enzymes during growth depending on the external pH, which manifests as a lack of hydrogen gas generation during glycerol utilization at pH values below 5.9. It is suggested that cells maintain ΔpH during the fermentative growth via formate-lactate-succinate exchange. The decrement of the value of pHin, but not of pHex in mutant cells, is regulating ΔpH and consequently proton motive force generation.

Energetics of the Electron Transfer Pathways in the Homodimeric Photosynthetic Reaction Center.

Photosynthetic reaction centers from a green sulfur bacterium (GsbRC), the PscA/PscA proteins, and photosystem I (PSI), PsaA/PsaB proteins, share structural similarities. Here, we report the redox potential (Em) values of GsbRC by solving the linear Poisson-Boltzmann equation and considering the protonation states of all titratable sites in the entire GsbRC protein and identify the factors that shift the Em values with respect to PSI. The Em values for one-electron reduction of the accessory (A-1) and adjacent (A0) chlorophylls in GsbRC are 100-250 mV higher than those in PSI, whereas the Em values for the Fe4S4 cluster (FX) are at the same level. The PsaA-Trp697/PsaB-Trp677 pair in PSI, which forms the A1-quinone binding site, is replaced with PscA-Arg638 in GsbRC. PsaB-Asp575 in PSI, which is responsible for the Em difference between A1A and A1B quinones in PSI, is absent in GsbRC. These discrepancies also contribute to the upshift in Em(A-1) and Em(A0) in GsbRC with respect to PSI. It seems likely that the upshifted Em for chlorophylls in GsbRC ultimately originates from the characteristics of the electrostatic environment that corresponds to the A1 site of PSI.

Process Technology for Production of Hydrogen-Rich Water and Water Characterizing by Highly Negative Oxidation Reduction Potential

The construction of plasma reactors and the technological process of obtaining water rich in hydrogen and characterized by a negative oxidation potential are presented in the publication. Hydrogen-rich water was obtained based on non-plasma technology and water saturation with hydrogen gas in a reactor vessel or in glass bottles. We have developed a plasma flow reactor that allows for contactless microstructuring and modifying the properties of water / aqueous solutions by resonant stochastic vibration amplification of selected chemical compounds in water with broadband electromagnetic noise with frequencies ranging from 100 Hz to 50 MHz generated during plasma discharge. This water is then saturated with hydrogen gas in the reactor or in glass bottles. The water obtained in the reactor is characterized by a high concentration of hydrogen (8 mg/L) and a negative oxidation-reduction potential (ORP) value (-450 mV). In this technology, the process of saturating water with hydrogen in a 1 m3 tank at a temperature of 20oC takes about 30 minutes. In the technology of obtaining water with negative ORP potential in the bottles, the process of saturating the water with hydrogen lasts only 5-10 seconds. Water obtained with such technology in the glass bottles does not contain much hydrogen gas after 24 hours, while it is characterized by a negative ORP value of about -380 mV even for a period of three months. Obtaining water with presented parameters is possible only in the case of water subjected to the influence of broadband electromagnetic noise with frequencies ranging from 100 Hz to 50 MHz generated during plasma discharge.

Aeration control strategy design based on dissolved oxygen and redox potential profiles for nitrogen and phosphorus removal from sewage in a sequencing batch reactor

Oxygen availability during different stages of biological nutrient removal (BNR) plays utmost critical role in all wastewater treatment techniques. Inadequate aeration control results in low treatment efficiencies and may lead to significantly higher costs. Hence, a strategically designed aeration scheme is very crucial. This study was carried out with the objective of maximising nitrogen and phosphorus removal from sewage by implementing an optimised aeration strategy. To achieve this, a 4-hour Anaerobic/Aerobic/Anoxic (AOA) cycle based on dissolved oxygen (DO) and oxidation-reduction potential (ORP) values was strategically designed, implemented and monitored in a 4.5 l laboratory-scale Sequencing Batch Reactor (SBR). On an average, feed waste consisted of 170 mg/l of biological oxygen demand (BOD), 228 mg/l of chemical oxygen demand (COD), 64 mg/l of total nitrogen (TN) and 33 mg/l of ortho-phosphate (PO43−). The average BOD, COD, TN and PO43− loading rates of 0.510, 0.684, 0.192 and 0.099 kg/(m3-d), respectively were applied to the reactor. During the 90-day operation of the SBR, it was observed that BOD, COD, TN and PO43− removal were achieved with 91%, 93%, 90% and 75% efficiencies, with removal rates of 0.477, 0.614, 0.173 and 0.075 kg/(m3-d), respectively. Also, the cycle study revealed that P removal occurred during the aerobic phase, while N removal occurred during the anoxic phase through denitrification. A mass balance analysis for N also revealed that denitrification and microbial uptake accounted for 59% and 41% of nitrogen removal, respectively. Study revealed that nutrient removal was achieved successfully while avoiding any unnecessary extended aeration costs. Such aeration strategy based on DO and ORP values could be deployed not only to optimise the aeration phase lengths, but could also be used for dynamic process control to manage fluctuations in influent characteristics and system conditions.

Removal of Organic Pollutants Via Electrochemical Oxidation Near Anodes During Electrokinetic Remediation: Proof of Concept

This study designed a practical approach of separating electrodes chambers to prove the influence of electrochemical oxidation on pyrene removal during electrokinetic (EK) remediation. The anode and cathode electrodes were arranged in two independent soil chambers, and the soil chambers were connected by salt bridges. Salt bridges electrokinetic (SBEK) remediation avoided acid–base neutralization and facilitated the intensity of the current. The results showed that 99.5% of pyrene was removed within 7 days in anodic chamber. The removal rate of pyrene was ∼99.6–99.9% at SBEK1 anode and 29.5–36.2% at SBEK1 cathode after 42 days. The changes in current, pH, and redox potential values indicated that an efficient “oxidizer” was formed in the anode chamber. Compared with conventional EK remediation, SBEK can take place under a suitable oxidizing condition because of increasing current intensity and decreasing soil pH in the anode chamber. Furthermore, SBEK with electrode polarity reversal test had better decontamination efficiency of pyrene than fixed electrodes. Removal rate of pyrene increased to 62.9% after 14 days with polarity reversal; correspondingly, the energy consumption of SBEK test was ∼13 times higher than that of the conventional EK test. The novel application of separated electrodes chambers appears to be a viable strategy for removing organic pollutants.

Organic matter degradation and bacterial communities in surface sediment influenced by Procambarus clarkia.

To alleviate excessive organic matter (OM) accumulation in sediments and reduce the risk of endogenous water pollution and eutrophication in aquaculture ponds, an 84-day experiment investigated the effect of the red swamp crayfish Procambarus clarkii on the OM degradation and bacterial communities in sediments. The experiment established two groups, P. clarkia treatment and control (represented as PG and CG, respectively), with three replicates for each group. At the end of experiment, the total, light fraction, and heavy fraction organic matter concentrations in the sediment of the PG group were significantly lower than those of the CG group. Significantly higher oxidation-reduction potential (ORP) and more extensively degraded OM, indicated by fatty acids, were observed in the PG group. Compared to the CG group, the average OM removal efficiency induced by crayfish in the PG group was 15.24%. Using 16S ribosomal RNA (rRNA) high-throughput sequencing, we investigated the differences in benthic bacterial communities between the PG and CG groups. Linear discriminant analysis (LDA) effect size (LEfSe) analysis revealed that Nitrospirae, Nitrospira, Alphaproteobacteria, OLB14, Nitrospirales, Rhodobacterales, Rhizobiales, Micrococcales, Nitrospiraceae, Rhodobacteraceae, Nitrospira, Rhodobacter, Thermomonas, and Denitratisoma were significantly enriched in the PG group. Four significantly different functional groups related to OM degradation were determined between the PG and CG groups according to the functional annotation of procaryotic taxa (FAPROTAX) analysis. These four functional groups, aerobic chemoheterotrophy, manganese oxidation, dark iron oxidation, and dark sulfide oxidation, showed significantly higher relative abundances in the PG group. Overall, P. clarkia effectively increased the ORP values of sediments to provide favorable conditions for OM degradation and changed the composition and function of bacterial communities to improve bacterial abilities for OM decomposition, thereby promoting OM degradation in the sediment.

Kinetic and Thermodynamic Properties of Ytterbium Chloride and Fluoride Complexes in Chloride Melts

An important problem concerning rare earth metals and molten salts is the reprocessing of nuclear fuel, since lanthanides are always present in spent nuclear fuel. According to the technology being developed for pyroelectrochemical processing of nuclear waste spent fuel is converted into molten salts by anodic dissolution, followed by electrochemical extraction of actinides from lanthanides.Thus a knowledge of the electrochemistry and thermodynamics of lanthanide compounds in molten salt systems is very useful for the understanding the recycling of spent nuclear fuel.The electroreduction of YbCl3 in alkali chloride melts (NaCl-KCl, KCl, CsCl) was studied in the temperature range 973-1173 K by different electrochemical methods. The diffusion coefficients (D) for Yb(III) and Yb(II) were determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry methods. Decreasing values of D were obtained when the cation in the second coordination sphere changed from Na to Cs. It was shown that such changes are due to the decreasing of counter polarizing effect of cations with increasing cationic radius.The standard rate constants of charge transfer (k s) for the Yb(III)/Yb(II) redox couple were calculated on the basis of cyclic voltammetry data using Nicholson’s approach. The following row of the standard rate constants of charge transfer has been experimentally determined: k s (KCl) < k s (CsCl) < k s (NaCl-KCl).The formal redox potentials E* Yb(III)/Yb(II were obtained in alkali chlorides melts from the linear sweep voltammetry data. From the values of the formal redox potentials were calculated the Gibbs energies and equilibrium constants for the reaction:YbCl2(sol.) +1/2 Cl2(g.) « YbCl3(sol.) (1)It was determined the increasing of the formal entropy for the reaction (1) in transition from NaCl-KCl to CsCl melt that associated with a greater degree of ordering of the reaction products due to the complex formation.Influence of fluoride ions (NaF) on the electrochemical behavior of the Yb(III)/Yb(II) redox couple in an equimolar NaCl-KCl melt was studied. It was determined а decrease of diffusion coefficients and standard rate constants, as well as a shift of the formal redox potentials to the negative region.

ORP should not be used to estimate or compare concentrations of aqueous H2: An in silico analysis and narrative synopsis

Oxidation reduction potential (ORP) has become a commonly used measurement to characterize functional beverages, specifically alkaline ionized water and hydrogen water. Numerous health benefits including antioxidant effects have been attributed to a negative ORP value. A greater negative ORP value is often incorrectly interpreted to mean a greater degree of health benefits and/or a high concentration of H2. Some hydrogen meters use the Nernst equation to calculate the concentration of H2 based on the measured ORP value. Unfortunately, due to the fundamental issues with the ORP meter, the calculated H2 value may be very inaccurate. Using the Nernst equation, we performed an in silico analysis of the ORP as a function of pH, temperature, and H2 concentration. Our analysis shows that a one unit increase in pH (e.g., 7–8) influences the ORP by as much as increasing the H2 concentration by 100 times (e.g., 1–100 mg/L). Similarly, at a saturated H2 concentration (1.57 mg/L) and pH 7, every ∆T of 20 °C changes the ORP by ≈ 30 mV. This is comparable to changing the H2 concentration by a factor of 10 (0.1 mg/L to 1 mg/L). Finally, to measure H2 within 0.1 mg/L, ORP meters need to have an accuracy of about 0.8 mV. However, ORP meters have an error range of at least ±10 mV, which corresponds to a potential error in measured H2 concentration of nearly 2 mg/L (≈125% error). This analysis shows that pH, temperature, and the intrinsic ORP errors can individually influence the ORP greater than the entire contribution of dissolved H2 within normally used ranges. In fact, this can easily result in a water sample with a greater negative ORP than another despite having significantly less H2. This makes it impossible to consistently determine if one water sample has more H2 than another water sample. Therefore, we can only conclude, based on a negative ORP reading, that, excluding the possibility of other reductive redox couples, some level of dissolved H2 is present in the water. Accordingly, ORP and ORP-based H2 meters are not recommended for testing or comparing the concentration of H2 in water. Experimental studies are warranted to determine if the ORP error is as great as or greater than what is predicted via this in silico analysis.

Redox potential determination of the Hell’s Gate globin I protein facing multiple exogenous ligands

Methylacidiphilum infernorum is a methanotroph bacterium that survives under extreme temperature and pH conditions in which five globins were identified. Among them, Hell’s Gate Globin I (HGbI) is a hemeprotein that presents peculiar features if compared to other globins, like stability at pH 2.8, very high oxygen affinity, and pH-dependent hexacoordination. All these features are likely related to the FeIII/II ion of the heme group whose redox behavior needs to be understood. Herein, we present the spectroelectrochemical determination of the redox potential of the HGbI protein in the absence and presence of relevant heme-binding molecules (cyanide, imidazole, carbon monoxide, nitric oxide and oxygen) in solution and also at different pH values (3.5 to 9.5). The spectroelectrochemical studies were performed giving midpoint redox potential (Em) values of −305, −338, and −442 mV vs normal hydrogen electrode (NHE) for the HGbI unliganded protein and bonded to imidazole and cyanide, respectively. The impressive negative value of the unliganded HGbI indicates it is very improbable to keep it reduced for binding and/or store O2. Interestingly, it was noticed an unusual high affinity of ferrous HGbI to imidazole and cyanide. In addition, the Em values showed pH-dependence, exhibiting a sigmoidal response whose pKa value was calculated at 6.9 likely associated to a sixth heme ligand. In presence of CO and NO, the spectroelectrochemical curves showed hysteresis due to the complete dissociation of the ligands in the oxidized state. Oxidation potentials of 385 and 130 mV vs NHE were determined for CO-HGbI(FeII) and NO-HGbI(FeII) species, respectively. Altogether, these results suggest HGbI protein is likely not involved in the storage nor in the transport of oxygen in the Methylacidiphilum infernorum microorganism. Nevertheless, it is implied the physiological function of HGbI might be related to redox-based processes, which remains to be further elucidated.

Ion-specific bathochromic shifts: Simultaneous detection of multiple heavy metal pollutants via charge transfer interactions

An anthraimidazoledione-based colorimetric probe (1) has been developed to detect heavy metal pollutants in acetonitrile medium. Adding metal ions, such as Zn2+, Ni2+ and Co2+ induce ion-dependent redshifts in the metal-to-ligand charge transfer (MLCT) band. As a result, the almost colorless solution of1turned into green, yellow and red colors upon adding Zn2+, Ni2+, and Co2+ ions. On the other hand, the blue fluorescence of 1 is slightly quenched in the presence of Zn2+ ions, while the diminution is significant for Ni2+ ions. On the other hand, Co2+ ion results in the red-shift of emission maxima and quenching. Thus, we could observe faint cyan-colored fluorescence with Co2+ ions. The binding affinities for metal ions follow Irving–William’s order. At the same time, the colorimetric responses depend on the ionic radius, hydration enthalpy, coordination number, crystal field stabilization energies of the metal ions, etc. However, in the mixed aqueous environment, the ratiometric response was noticed only with Co2+ ions. Along with ratiometric color change, additions of metal ions result in an increase in both anodic and cathodic peak current along with shifts in the redox potential values. Further, the presence of residual Co2+ was determined in natural water samples.

An investigation on the ion exchange membrane bioreactor with a spiral wound contactor for nitrate removal from contaminated groundwater

In the present study, we report the first operation of a pilot scale ion exchange membrane bioreactor (IEMB). It treated 1–2 m3/d of water contaminated with nitrate. IEMB was made up of anion exchange membrane spiral module integrated with a fixed bed bioreactor (FBBR), a novel configuration for an IEMB system. Nitrate elimination was accomplished through Donnan dialysis using chloride as counter ion followed by heterotrophic denitrification in an anoxic FBBR employing glycerol as electron donor and carbon source. The performance of IEMB revealed an excellent nitrate removal at the selected operating conditions, successfully eliminating a nitrate loading rate of 5.0 kg NO3−/m3/d and producing 30 ± 5 mg/L nitrate in the effluent at steady state. Anion exchange membrane being non-selective also transferred a significant concentration of sulphate from the feed-side to the bio-side leading to sulphate accumulation in FBBR. As a result, denitrification performance was affected due to the activation of sulphate reducing bacteria leading to the upset of FBBR. Batch experimental study aiming to screen the effect of nitrate to sulphate ratio on denitrification, demonstrated the possible occurrence of sulphate reduction at [nitrate]/[sulphate] < 0.2, exhibiting a highly negative oxidation reduction potential (ORP) value (−450 mV). This signifies that a minimum [nitrate]/[sulphate] > 0.2 is required as to suppress sulphate reduction phenomenon during denitrification. IEMB calibration for denitrification using glycerol as a carbon source revealed that 100 % stoichiometric donor/acceptor (C/N) ratio was suitable for producing sufficient nitrate biodegradation and acceptable ORP value (~−220 mV). Present work established promising application prospects of IEMB comprising nitrate selective membrane module for the treatment of high nitrate wastewater with a treatment capacity of 1.5 m3/d at optimized operating conditions.

The effects of low oxidation-reduction potential on the performance of full-scale hybrid membrane-aerated biofilm reactors

Membrane-Aerated Biofilm Reactors (MABRs) are becoming a popular process intensification alternative within wastewater treatment plants (WWTP). Indeed, the nitrogen removal capacity of aerobic/anoxic/anaerobic reactors can be substantially enhanced with reduced energy consumption and footprint requirements. However, little is known about how oxidation–reduction potential (ORP) may impact their overall process performance. This study aims to report some of these effects by showing the results of almost three years of monitoring of two hybrid MABRs (R1, R2) adjacent to an existing Biodenipho™ facility. In Period 1 (P1), R1 and R2 were fed with anaerobic mixed liquor from the selector for the biological phosphorus removal zone. In Period 2 (P2), external aeration was introduced to increase ORP values (R1, R2), and membranes were replaced (R1) or cleaned (R2). Results show an increase in nitrification rates: from 0.27 and 0.33 g N m−2 d−1 in R1/R2 during P1 to 1.0 and 0.80 g N m−2 d−1 in R1/R2 during P2. 16 s rRNA amplicon sequencing analysis revealed that the relative abundance of nitrifying organisms increased from 0.2 to 6.7 % in R1 and 0.8 to 5.3 % in R2 in P2 (in detriment of microbes with fermenting capabilities). Energy dispersive X-ray spectroscopy confirmed the presence of coating substances under the lowest ORP (P1), which could be pyrite and its precursors like mackinawite. Overall, it is hypothesized that low ORP conditions (P1) had a detrimental effect on nitrification performance, as it promoted the reduction of different iron and sulfur compounds, which in turn a) precipitate in the biofilm as FeS increasing mass transfer limitations and competing with biomass for space; b) re-oxidize increasing the internal oxygen demand; c) inhibit nitrifiers growth.

In silico studies disclose the underlying link between binding affinity and redox potential in laccase isoforms

Laccases are copper-containing enzymes belonging to the family of multicopper oxidases (MCOs). All MCOs use molecular oxygen to oxidize a wide range of organic compounds by radical catalysis. One of the key fundamental properties of laccases is having high or low redox potentials depending on the active site organization. Several experimental studies have been done to rationalize the high and low redox potential laccases (LRPL), however, molecular understanding is still lacking. In this work, we explored the proteomic profile of laccases produced in the fungal cultures, specifically induced with lignocellulosic biomass such as rice straw. This study was undertaken to explain the differences in the high redox and low redox potential values of different laccases using in-silico approaches. Proteomic profiling and structural and sequence analysis revealed a low level of similarity among them. Docking analyses and molecular dynamics simulation analysis revealed that high redox potential laccases (HRPL) are having good binding affinity compared to low or medium redox potential laccases (MRPL). The stability of these complexes was further analyzed based on reactive distances, active site volume comparison and a number of tunnel formations that were observed to be significantly higher for HRPL. Our results indicate that the number of tunnel formations calculated from the simulation’s trajectories and available water molecules at the T3 site directly correlates with the laccases’ redox potentials. This study will be helpful and provide valuable inputs for the designing of new laccases to improve lignin degradation. Communicated by Ramaswamy H. Sarma

Electronic structure theory investigation on the electrochemical properties of cyclohexanone derivatives as organic carbonyl-based cathode material for lithium-ion batteries

Organic carbonyl-based compounds with redox-active site have recently gained full attention as organic cathode material in lithium-ion batteries (LIBs) owing to its high cyclability, low cost, high abundance, tunability of their chemical structure compared to traditionally used inorganic material. However, the utilization of organic carbonyl-based compounds in LIBs is limited to its poor charge capacity and dissolution of lower molecular weight species in electrolytes. In this study, we theoretically investigated five set of cyclohexanone derivatives (denoted as: H 1 , H 2 , H 3 , H 4 , and H 5 ) and influence of functional groups (-F and -NH 2 ) on their electrochemical properties using advanced level density functional theory (DFT) with the Perdew-Burke-Ernzenhof hybrid functional (PBE0) at 6-31+G(d,p) basis set. In line with the result gotten, the HOMO-LUMO results revealed that compound H 5 is the most reactive among the studied cyclohexanone derivatives exhibiting energy gap values of 0.552, 0.532, 0.772 eV for free optimized structures and structurally engineered structures with electron withdrawing group (EWG) and electron donating group (EDG) respectively. Also, results from electrochemical properties of the studied compounds lithiated with only one lithium atom displayed that compound H 2 exhibited interesting redox potential and energy density for all the studied structures in free optimized state (1108.28 W h kg −1 , 4.92 V vs Li/Li + ), with EWG (648.22 W h kg −1 , 3.313 V Li/Li + ), and with EDG (1002.4 W h kg −1 , 5.011 V vs Li/Li + ). From our result, we can infer that compound H 2 and H 3 with corresponding redox potential, energy density and theoretical charge capacity value of 4.92 V vs Li/Li + , 1108.28 W h kg −1 , 225.26 mA h g −1 and 5.168 V, 1041.61 W h kg −1 , 201.55 mA h g −1 lithiated with only one lithium atom in free optimized state are the most suitable compounds to be employed as organic cathode material in lithium-ion batteries among all the investigated cyclohexanone derivatives.

Enhancement of butanol production in Clostridium acetobutylicum SE25 through oxidation-reduction potential regulation and analysis of its metabolic mechanisms

In this study, an exogenous regulatory strategy named as oxidation-reduction potential (ORP) regulation was performed in the butanol biosynthesis process by Clostridium acetobutylicum SE25 to accelerate the carbon metabolism flow to butanol and enhance butanol production. The findings show that the dithiothreitol and potassium ferricyanide were the optimal redox agents for regulating the ORP of the fermentation system. Specifically, when the ORP value of fermentation broth was controlled at −400 mV, the highest production of butanol (14.30 ± 0.65 g/L) was obtained, which was 10.80 % higher than that of the control group. And the yield and productivity of butanol were 0.24 g/g and 0.24 g/L/h, respectively. Furthermore, the physiological mechanisms of the effects of different ORP levels on butanol synthesis was investigated, and the results demonstrate that ORP could both regulate the level and ratio of energy charge and NADH/NAD+, and redistribute metabolic flux. Thus, the ORP control strategy, according to the results in this study, is an effective and attainable approach to obtain the high production of butanol.

The influence of hydrogen production on the formation of metabolic pathways and regulation of ΔpH in Escherichia coli

Hydrogen (H2) metabolism in Escherichia coli occurs via reversible membrane-associated hydrogenase enzymes (Hyd). Hyd-3 and Hyd-4 with formate dehydrogenase H (FDH-H) form formate hydrogen lyase complexes. The changes of metabolic pathways and ΔpH (pHin-pHex) regulation during fermentation of glucose, glycerol and formate in non H2-producing hypF (lack of all Hyds) and fdhF (lack of FDH-H) mutants at pH 7.5 were investigated. It was shown that specific growth rate was higher by ∼23% in hypF and fdhF, compared to wild type (wt), suggesting the negative effect of H2 on bacterial growth. Moreover, it was shown that H2 generation did not have a vital role in glucose and glycerol utilization rate at 0–72 h. The utilization of external formate was detected in wt (∼2.6 mM) and hypF (∼0.68 mM), but not in fdhF, due to the absence of enzyme responsible for formate metabolism. Nevertheless, the changes in ΔpH were not evident at 3 h. The ratio of generated end-products and regulation of ΔpH at late log (6 h) and exponential phase (24, 72 h) were various in hypF and fdhF due to formate disproportionation in hypF and proton generation, therewith absence of H2 generation. Taken together it can be concluded that bacteria regulate generation of fermentation end-products via balancing the concentration of acids and ethanol to maintain ΔpH and redox potential values. The results obtained are important for development and regulation of H2 production technology when applying mixed carbon sources.

Effect of salt concentration on the properties of electrolyzed reducing water (ERW) and electrolyzed oxidizing water (EOW): an empirical correlation study

This research aimed to examine the effect of NaCl concentration on the pH and Oxidation Reduction Potential (ORP) values of both EOW and ERW products. The experiment was conducted using distilled water. The electrolysis apparatus consisted of anode and cathode chambers. The chambers were connected by a tube filled with a cotton (or a fabric). Both electrodes (anode and cathode) were made of titanium and formed as a spiral. Electrolysis was performed for 780 minutes, and the pH and ORP values of both EOW and ERW were measured every time. Sodium chloride concentration was varied for 0, 100, and 200 ppm. Experimental results revealed that the higher the NaCl concentration, the higher ERW’s pH rise and the lower the EOW’s pH. Similar results were found for ORP. ERW’s ORP was lowered while EOW’s ORP rose with the increase in NaCl concentration. This study could also generate a mathematical model that correlates pH and time during the electrolysis process. The model was developed by connecting with a simple polynomial. A similar approach was used to develop the model that correlates pH and ORP value.