Optimization of electrochemical process for phenanthrene removal from aqueous medium by Taguchi

Discharge of refinery effluents containing phenanthrene (Phe) may exert carcinogenic effects on aquatic organisms. The aim of the current investigation was to investigate electrochemical removal of Phe from urban drinking water using a batch reactor. Phe removal efficiency was examined under different operating conditions including current density (1–8 mA/cm²), electrode composition materials such as aluminum (Al), copper (Cu), iron (Fe), steel (AS), or zinc (Zn), pH (4–10), and duration (20–60 min). Phe concentration was determined utilizing standard techniques. Steel–Steel (AS–AS) as anode–cathode electrodes resulted in the least Phe removal (not detected), while Zn–Cu anode–cathode electrodes produced the highest Phe removal (100%) under similar experimental conditions. The increase in current density from 1 to 8 mA/cm² at optimum electrode and pH enhanced Phe removal from 56% to 100%. The rise in duration from 20 to 60 min at optimum electrode and pH increased Phe removal from 32% to 100%. These findings indicated that Phe removal efficiency was elevated with increasing current density, electrolysis time, and pH. Batch experiments indicated that the electrochemical reactor might be effective in removing Phe from drinking water.     

新型双槽光电化学反应器对活性艳红的降解研究

用热氧化法制备了TiO2/Ti薄膜电极,并用XRD和AFM对TiO2/Ti薄膜电极的晶形和表面形貌进行了表征。结果表明：热氧化法制备的TiO2主要为锐钛型纳米颗粒,直径在40 nm左右。设计了一种新型双槽光电化学反应器,用于废水的处理。以热氧化法制备的TiO2/Ti薄膜电极为阳极进行光电催化反应,同时以石墨电极为阴极用于产生双氧水,并与紫外光组成UV/H2O2体系。考察了双槽反应器中活性艳红X-3B在不同条件下的降解效果。降解结果表明：在新型反应器的阴阳两极槽中,活性艳红不仅在TiO2/Ti阳极槽中被降解,而且在石墨阴极槽中也得到降解;活性艳红在酸性条件下的降解效果最好;相对于单纯的电化学氧化和光催化,光电化学协同作用对X-3B的降解效果最好。     

Effects of reducing agent and approaching anodes on chromium removal in electrokinetic soil remediation

A soil remediation method combining in situ reduction of Cr(VI) with approaching anodes electrokinetic (AAs-EK) remediation is proposed. EK experiments were conducted to compare the effect of approaching anodes (AAs) and fixed electrodes (FEs) with and without sodium bisulfite (NaHSO₃) as a reducing agent. When NaHSO₃ was added to the soil before EK treatment, 90.3% of the Cr(VI) was reduced to Cr(III). EK experiments showed that the adverse effect of contrasting migration of Cr(III) and Cr(VI) species, which limits the practical application of this technique, was eliminated in the presence of the reducing agent. Furthermore, Tessier fractionation analysis indicated that the reducing agent changed the distribution of the chemical forms of Cr. The AAs-EK method was shown to acidize the soil as the anode moved toward the cathode and this acid front pushed the “focusing” region toward the cathode. After remediation, the pH of the soil was between 1.8 and 5.0 in AAs-EK experiments. The total Cr removal efficiency was 64.4% (except in the “focusing” region) when the reduction reaction was combined with AAs-EK method. We conclude that AAs-EK remediation in the presence of NaHSO₃ is an appropriate method for Cr-contaminated soil.     

Coupled electrocoagulation–electro-Fenton for efficient domestic wastewater treatment

This article reports the first use of coupled electrocoagulation and electro-Fenton (EF-EC) to clean domestic wastewater. Domestic wastewater contains high amounts of organic, inorganic and microbial pollutants that cannot be usually treated in a single step. Here, to produce an effluent suitable for discharge in a single process step, a hybrid process combining electrocoagulation and electro-Fenton was simultaneously used to decrease chemical oxygen demand (COD), turbidity and total suspended solids (TSS) from domestic wastewater. The electrocoagulation–electro-Fenton process was firstly tested for the production of H₂O₂ using Ti–IrO₂ and vitreous carbon- or graphite electrodes arranged at the anode and the cathode, respectively. The concentration of H₂O₂ recorded at 1.5 A of current intensity during 60 min of electrolysis using vitreous carbon- and graphite electrodes at the cathode was 4.18 and 1.62 mg L^?1, respectively. By comparison, when the iron electrode was used at the anode, 2.05 and 1.06 mg L^?1 of H₂O₂ were recorded using vitreous carbon and graphite, respectively. The H₂O₂ concentration decrease was attributed to hydroxyl radical formation generated by the Fenton reaction. Electro-Fenton using iron electrode at the anode and vitreous carbon at the cathode with a current density imposed of 0.34 A dm^?2 ensures the removal efficiency of 50.1 % COD_T, 70.8 % TSS and 90.4 % turbidity. The electrocoagulation–electro-Fenton technique is therefore a promising secondary treatment to simultaneously remove organic, inorganic and microbial pollutants from domestic, municipal and industrial wastewaters.     

阴阳极成对耦合紫外光辅助电催化降解毒死蜱

以空气扩散阴极、纯铂阳极和紫外灯构建了阴阳极成对耦合紫外光辅助电催化的体系,并系统地研究了电流密度、阳极SO42-浓度以及毒死蜱初始浓度对毒死蜱降解效果的影响.结果表明,当阴极/阳极的电流密度为45/450 mA·cm^-2,阳极SO42-浓度为1.0 mol·L^-1,毒死蜱初始浓度为25 mg·L^-1时,反应60 min后毒死蜱降解率可达99%.对阴极产物的红外分析结果表明,毒死蜱降解后结构中的吡啶环和PS被破坏,产生亚硝氮和正磷酸盐,毒性得到减弱.通过对比阴阳极成对耦合紫外光复合体系与阴极耦合紫外光复合体系、阳极耦合紫外光复合体系的电流效率,发现阴阳极成对耦合紫外光复合体系的电流效率是阴极耦合紫外光复合体系的2倍,是阳极耦合紫外光复合体系的4倍.     

Multi-factor principle for electrolyte additive molecule design for facilitating the development of electrolyte chemistry

When I read the paper"Electrolytes enriched by potassium perfluorinated sulfonates for lithium metal batteries"from Prof. Jianmin Ma's group, which was published in Science Bulletin (doi.org/10.1016/j.scib.2020.09.018), I felt excited as presented a multi-factor principle for applying potassium perfluorinated sulfonates to suppress the dendrite growth and protect the cathode from the viewpoint of electrolyte additives. The effects of these additives are revealed through experimental results, molecular dynamics simulations and first-principle calculations. Specifically, it involves the influence of additives on Li+ solvation structure, solid electrolyte interphase (SEI), Li growth and nucleation. Following the guidance of the multi-factor principle, every part of the additive molecule should be utilized to regulate electrolytes. This multi-factor principle for electrolyte additive molecule design (EAMD) offers a unique insight on understanding the electrochemical behavior of ion-type electrolyte additives on both the Li metal anode and high-voltage cathode. In these regards, I would be delighted to write a highlight for this innovative work and, hopefully, it may raise more interest in the areas of electrolyte additives.     

Performance and mechanistic study on electrocoagulation process for municipal wastewater treatment based on horizontal bipolar electrodes

• EC modified with BPEs enhances pollutant removal and reduce energy consumption. • Increasing BPE number cannot increase flocculants yield exponentially. • Simulations help to predict the distribution of electrochemical reactions on BPEs. The design of electrodes is crucial to electrocoagulation process (EC), specifically, with respect to pollutant removal and energy consumption. During EC, the mechanisms for interaction between different electrode arrangement and electrode reactions remain unclear. This work presents an integrated EC process based on horizontal bipolar electrodes (BPEs). In the electrochemical cell, the graphite plates are used as driving cathode while either Fe or Al plates serves as driving anode and BPEs. The BPEs are placed horizontally between the driving electrodes. For municipal wastewater treatment, the pollutant removal efficiency and energy consumption in different configurations of two-dimension electrocoagulation (2D-EC) system with horizontal BPEs were investigated. The removal efficiency of turbidity, total phosphorus and total organic carbon increased significantly with the number of BPEs. Noted that the energy consumption for TP removal decreased by 75.2% with Fe driving anode and 81.5% with Al driving anode than those of 2D-EC, respectively. In addition, the physical field simulation suggested the distributions of potential and current in electrolyte and that of induced charge density on BPE surface. This work provides a visual theoretical guidance to predict the distribution of reactions on BPEs for enhanced pollutant removal and energy saving based on electrocoagulation process for municipal wastewater treatment.     

The storage mechanism difference between amorphous and anatase as supercapacitors

Although TiO2 nanotubes is a promising electrode as supercapacitors due to its high energy density, easy synthesis and chemical stability, there are draw backs such as low conductivity and capacitance. Many studies concentrated on improving its electrochemical performance itself but little attention was payed to the reason of capacitance differences caused by its different crystal structures. Herein, we prepare amorphous and anatase TiO2 nanotubes and hydrogenated them by a simple electrochemical hydrogenation method to improve their conductivity and capacitance. And then study and compare their morphology and structure differences by SEM, TEM, XRD and BET. The results show that the pore size distribution, internal structure order and internal carrier concentration are the main reasons for their electrochemical performance differences. The microporous structure less than 2 nm in amorphous nanotubes act as a trap of electrolyte ions at current density larger than 0.1μA cm-2, leading to small charge and discharge capacitance. The long-range ordered crystal structure of anatase is more favorable for the orderly diffusion of carriers, reducing the inelastic scattering of carrier diffusion process and the electron hole-complexing probability, making anatase nanotubes exhibit higher coulomb efficiency and cycle stability than that of amorphous ones.     

Chaos and pattern formation in a spatial tritrophic food chain

The model of Hastings and Powell describes a tritrophic food chain that exhibits chaotic dynamics. The model assumes that the populations are homogeneously mixed, so that the probability that any two individuals interact is uniform and space can be ignored. In this paper we propose a spatial version of the Hastings and Powell model in which predators seek their preys only in a finite neighborhood of their home location, breaking the mixing hypothesis. Treating both space and time as discrete variables we derive a set of coupled equations that describe the evolution of the populations at each site of the spatial domain. We show that the introduction of local predator–prey interactions result in qualitatively distinct dynamics of predator and prey populations. The evolution equations for the predators involve averages over the local density of preys, whereas the equations for the preys involve double averages, where the local density of both preys and predators appear. Our numerical simulations show that local predation also leads to spontaneous pattern formation and to qualitative changes in the global dynamics of the system. In particular, depending on the size of the predation neighborhoods, the chaotic strange attractor present in the original model of Hastings and Powell can be replaced by a stable fixed point or by an attractor of simpler topology.     

模拟镉污染土壤的电动力学修复研究

采用阳离子交换膜调控电解过程中pH值的变化和电解富集土壤中的元素,在pH=5.0的缓冲溶液中进行土壤的电动强化处理.通过对镉形态的分析,找到镉在电场中迁移转换的规律.在处理时间内,阳极附近镉的去除率达99%以上,阴极镉的富积系数达2.026,表明电场对土壤中重金属的迁移溶出有强化去除作用.     

Sensitivity of ecological models to their climate drivers: statistical ensembles for forcing.

Global and regional numerical models for terrestrial ecosystem dynamics require fine spatial resolution and temporally complete historical climate fields as input variables. However, because climate observations are unevenly spaced and have incomplete records, such fields need to be estimated. In addition, uncertainty in these fields associated with their estimation are rarely assessed. Ecological models are usually driven with a geostatistical model's mean estimate (kriging) of these fields without accounting for this uncertainty, much less evaluating such errors in terms of their propagation in ecological simulations. We introduce a Bayesian statistical framework to model climate observations to create spatially uniform and temporally complete fields, taking into account correlation in time and space, spatial heterogeneity, lack of normality, and uncertainty about all these factors. A key benefit of the Bayesian model is that it generates uncertainty measures for the generated fields. To demonstrate this method, we reconstruct historical monthly precipitation fields (a driver for ecological models) on a fine resolution grid for a climatically heterogeneous region in the western United States. The main goal of this work is to evaluate the sensitivity of ecological models to the uncertainty associated with prediction of their climate drivers. To assess their numerical sensitivity to predicted input variables, we generate a set of ecological model simulations run using an ensemble of different versions of the reconstructed fields. We construct such an ensemble by sampling from the posterior predictive distribution of the climate field. We demonstrate that the estimated prediction error of the climate field can be very high. We evaluate the importance of such errors in ecological model experiments using an ensemble of historical precipitation time series in simulations of grassland biogeochemical dynamics with an ecological numerical model, Century. We show how uncertainty in predicted precipitation fields is propagated into ecological model results and that this propagation had different modes. Depending on output variable, the response of model dynamics to uncertainty in inputs ranged from uncertainty in outputs that matched that of inputs to those that were muted or that were biased, as well as uncertainty that was persistent in time after input errors dropped.     

超滤膜材质对处理电泳漆液的影响

本文研究了聚砜，酞侧基聚砜，磺化聚砜，聚丙烯腈，醋酸纤维素，氰乙基醋酸纤维素，氯甲基化聚砜和季胺化聚砜等材质超滤膜的亲水性能，荷电性能以及它们对超滤阳极和阴极电泳漆液的影响，实验结果表明：亲水性较强，电负性较强的氰乙基醋酸纤维素和醋酸纤维素膜，适合用于处理阳极电泳漆液；而亲水性较强，电中性和电正性较强的氯甲基化聚砜和季胺化聚砜膜，则适合用于处理阴极电泳漆液。     

Metacommunity models predict the local-regional species richness relationship in a natural system

Many natural communities exhibit positive relationships between local and regional species richness (LSR-RSR relationships), which can be either linear or curvilinear. Previous models have shown that the form of this relationship depends on the relative rates of colonization and extinction and the sensitivity of these rates to competition. We use simple models to show that the LSR-RSR relationship also depends on the type of metacommunity structure (Levins-like or mainland-island), and our models generate a wider range of realistic forms than do most previous models. We parameterize and test our models with two independent data sets for Daphnia in rock pools on islands in Finland and Sweden. We find that the Levins-like model with competition correctly predicts the observed LSR-RSR relationship and provides the best fit to the average local species richness per island. Simulations show that our models are robust to relaxing our assumption of identical species properties. Our study is one of the first to make and successfully test quantitative predictions for how a widely studied community pattern, the LSR-RSR relationship, arises from metacommunity dynamics.     

Determinants of reproductive potential and population size in open populations of Patella vulgata

The importance of external and internal population processes in determining variation in reproductive output and variation in population size were quantified with model simulations for open populations of the sequentially hermaphroditic limpet Patella vulgata using field data from the Isle of Man and South West Ireland. Cross-correlation analyses of model outputs and elasticity analyses show that population dynamics are dominated by the effects of large females, and that recruitment adds little to reproductive output. However, populations experiencing low but highly variable recruitment appear male limited and recruitment pulses carrying young males into the population are correlated to reproductive output with a 2–5-year lag. We conclude that pulses in recruitment can be a major structuring force in these limpet populations, but site-specific post-recruitment processes will determine the relative importance of recruitment to population dynamics and the lag between recruitment and reproductive output.     

3D geometric structures and biological activity: Application to microbial soil organic matter decomposition in pore space

During the past 10 years, soil scientists have started to use 3D Computed Tomography in order to gain a clearer understanding of the geometry of soil structure and its relationships with soil properties. We propose a geometric model for the 3D representation of pore space and a practical method for its computation. Our basic idea consists in representing pore space using a minimal set of maximal balls (Delaunay spheres) recovering the shape skeleton. In this representation, each ball could be considered as a maximal local cavity corresponding to the “intuitive” notion of a pore as described in the literature. The space segmentation induced by the network of balls (pores) was then used to spatialize biological dynamics. Organic matter and microbial decomposers were distributed within the balls (pores). A valuated graph representing the pore network, organic matter and distribution of micro-organisms was then defined. Microbial soil organic matter decomposition was simulated by updating this valuated graph. The method was implemented and tested using real CT images. The model produced realistic simulated results when compared with data in the literature in terms of the water retention curve and carbon mineralization. A decrease in water pressure decreased carbon mineralization, which is also in accordance with findings in the literature. From our results we showed that the influence of water pressure on decomposition is a function of organic matter distribution in the pore space. As far as we know, this is the approach to have linked pore space geometry and biological dynamics in a formal way. Our next goal will be to compare the model with experimental data of decomposition using different soil structures, and to define geometric typologies of pore space shape that can be attached to specific biological and dynamic properties.     

Influence of host migration between woodland and pasture on the population dynamics of the tick Ixodes ricinus: A modelling approach

Ticks act as vectors of pathogens that can be harmful to animals and/or humans. Epidemiological models can be useful tools to investigate the potential effects of control strategies on diseases such as tick-borne diseases. The modelling of tick population dynamics is a prerequisite to simulating tick-borne diseases and the corresponding spread of the pathogen. We have developed a dynamic model to simulate changes in tick density at different stages (egg, larva, nymph and adult) under the influence of temperature. We have focused on the tick Ixodes ricinus, which is widespread in Europe. The main processes governing the biological cycles of ticks were taken into account: egg laying, hatching, development, host (small, mainly rodents, or large, like deer and cattle, mammals) questing, feeding and mortality. This model was first applied to a homogeneous habitat, where simulations showed the ability of the model to reproduce the general patterns of tick population dynamics. We considered thereafter a multi-habitat model, where three different habitats (woodland, ecotone and meadow) were connected through host migration. Based on this second application, it appears that migration from woodland, via the ecotone, is necessary to sustain the presence of ticks in the meadow. Woodland can therefore be considered as a source of ticks for the meadow, which in turn can be regarded as a sink. The influence of woodland on surrounding tick densities increases in line with the area of this habitat before reaching a plateau. A sensitivity analysis to parameter values was carried out and demonstrated that demographic parameters (sex ratio, development, mortality during feeding and questing, host finding) played a crucial role in the determination of questing nymph densities. This type of modelling approach provides insight into the influence of spatial heterogeneity on tick population dynamics.     

Sediment microbial fuel cell with floating biocathode for organic removal and energy recovery

A sediment microbial fuel cell (SMFC) with three dimensional floating biocathode (FBC) was developed for the electricity generation and biodegradation of sediment organic matter in order to avoid negative effect of dissolved oxygen (DO) depletion in aqueous environments on cathode performance and search cost-effective cathode materials. The biocathode was made from graphite granules with microbial attachment to replace platinum (Pt)-coated carbon paper cathode in a laboratory-scale SMFC (3 L in volume) filled with river sediment (organic content 49±4 g·kg^-1 dry weight). After start-up of 10 days, the maximum power density of 1.00W·m^-3 (based on anode volume) was achieved. The biocathode was better than carbon paper cathode catalyzed by Pt. The attached biofilm on cathode enhanced power generation significantly. The FBC enhanced SMFC performance further in the presence aeration. The SMFC was continuously operated for an over 120-day period. Power generation peaked within 24 days, declined gradually and stabilized at a level of 1/6 peak power output. At the end, the sediment organic matter content near the anode was removed by 29% and the total electricity generated was equal to 0.251 g of chemical oxygen demand (COD) removed.     

Simultaneous removal of Co,Cu, and Cr from water by electrocoagulation

This study provides an electrocoagulation process for the removal of metals such as cobalt, copper, and chromium from water using magnesium as anode and galvanized iron as cathode. The various parameters like pH, current density, temperature, and inter electrode distance on the removal efficiency of metals were studied. The results showed that maximum removal efficiency was achieved for cobalt, copper, and chromium with magnesium as anode and galvanized iron as cathode at a current density of 0.025?A?dm^?2 at pH 7.0. First- and second-order rate equations were applied to study adsorption kinetics. The adsorption process follows second-order kinetics model with good correlation. The Langmuir and Freundlich adsorption isotherm models were studied using the experimental data. The Langmuir adsorption isotherm favors monolayer coverage of adsorbed molecules for the adsorption of cobalt, copper, and chromium. Temperature studies showed that adsorption was endothermic and spontaneous in nature.     

Enhanced electrokinetic remediation of quinoline-contaminated soils

ABSTRACT

The aim of this investigation was to examine the ability of enhanced electrokinetic (EK) remediation to efficiently remove quinoline from contaminated kaolinite soils. In order to accomplish this, the effect of a voltage gradient and anode buffer concentration on migration of quinoline in kaolinite was determined. The results showed that EK transport process effectively stimulated desorption and movement of quinoline in kaolinite. The rate and distance of migration rose with increasing voltage gradient and anode buffer concentration under certain conditions. The mechanisms that drive quinoline migration by electrodynamic processes were established as attributed to either electromigration or electroosmosis, and both played key roles in driving quinoline to migrate towards the cathode.     

Multiple sources of predictive uncertainty in modeled estimates of net ecosystem CO2 exchange

Net ecosystem CO₂ exchange (NEE) is typically measured directly by eddy covariance towers or is estimated by ecosystem process models, yet comparisons between the data obtained by these two methods can show poor correspondence. There are three potential explanations for this discrepancy. First, estimates of NEE as measured by the eddy-covariance technique are laden with uncertainty and can potentially provide a poor baseline for models to be tested against. Second, there could be fundamental problems in model structure that prevent an accurate simulation of NEE. Third, ecosystem process models are dependent on ecophysiological parameter sets derived from field measurements in which a single parameter for a given species can vary considerably. The latter problem suggests that with such broad variation among multiple inputs, any ecosystem modeling scheme must account for the possibility that many combinations of apparently feasible parameter values might not allow the model to emulate the observed NEE dynamics of a terrestrial ecosystem, as well as the possibility that there may be many parameter sets within a particular model structure that can successfully reproduce the observed data. We examined the extent to which these three issues influence estimates of NEE in a widely used ecosystem process model, Biome-BGC, by adapting the generalized likelihood uncertainty estimation (GLUE) methodology. This procedure involved 400,000 model runs, each with randomly generated parameter values from a uniform distribution based on published parameter ranges, resulting in estimates of NEE that were compared to daily NEE data from young and mature Ponderosa pine stands at Metolius, Oregon. Of the 400,000 simulations run with different parameter sets for each age class (800,000 total), over 99% of the simulations underestimated the magnitude of net ecosystem CO₂ exchange, with only 4.07% and 0.045% of all simulations providing satisfactory simulations of the field data for the young and mature stands, even when uncertainties in eddy-covariance measurements are accounted for. Results indicate fundamental shortcomings in the ability of this model to produce realistic carbon flux data over the course of forest development, and we suspect that much of the mismatch derives from an inability to realistically model ecosystem respiration. However, difficulties in estimating historic climate data are also a cause for model-data mismatch, particularly in a highly ecotonal region such as central Oregon. This latter difficulty may be less prevalent in other ecosystems, but it nonetheless highlights a challenge in trying to develop a dynamic representation of the terrestrial biosphere.