Activated Carbon Particles Research Articles

Electrocatalytic degradation of oxytetracycline using three-dimensional electrode and optimization via fuzzy logic modeling

ABSTRACT The present paper focuses on a hybrid system combining electrochemical oxidation (EO) and activated carbon (AC) adsorption in a concept known as three-dimensional (3D) electrocatalytic technology for the treatment of oxytetracycline from aqueous solution; the conventional one-factor-at-a-time variation approach (AC dosage, OTC concentration, and current density) was used for determining the effects of operating parameters on the 3D electrochemical process and optimized via fuzzy logic modeling. The process’s superior performance was assessed based on comparative studies of the degradation efficiency of the 3D electrochemical process with AC adsorption and conventional 2D electrochemical process. The study showed that the AC particle electrode enhanced the performance of the 3D system by up to 21% in terms of OTC degradation efficiency compared to both adsorption and the conventional two-dimensional (2D) electrochemical system. When 2D and 3D processes were compared in required energy and electricity budgets, 3D electrode process with 0.75 g/L activated carbon requires 27.60 kWh/m3 and it perceived 2 times lower than 2D process; accordingly, the electricity budget is €5.38 and €2.81 for electrooxidation and 3D electrode process, respectively. The obtained results suggest that under the electric field, polarized AC worked as both adsorbent and a catalyst in the 3D electrochemical system, enhancing subsequently the decomposition of electro-generated H2O2 to more hydroxyl radicals (·OH) and promote the capacity of OTC mineralization.

Charge/discharge properties of activated carbon/ruthenocene hybrid electrodes in an ionic liquid electrolyte

The electrochemical behavior of ruthenocene (RuCp2) in organic electrolytes is complicated by disproportionation or dimerization reactions owing to the reactive nature of the RuCp2+ cation upon oxidation. In this study, RuCp2 is hybridized inside the micropores of microporous activated carbon (AC) via gas-phase adsorption. The resulting AC/RuCp2 hybrids can be used as electrode materials without dissolution of the adsorbed RuCp2 into electrolyte solution by combining with ionic liquid electrolytes. The charge storage of the hybrids is based on the reversible redox reaction of RuCp2 inside the micropores of AC. This hybridization is not accompanied by the volumetric expansion of the AC particles regardless of the RuCp2 contents. In addition, the AC/RuCp2 hybrids exhibit high redox potential as high as ca. 3.9–4.3 ​V (vs. Li/Li+). These features are advantageous for enhancing the volumetric energy density, which is more important than the enhancement of the gravimetric one, in terms of practical applications of electrical energy storage devices. In addition, the hybridized RuCp2 molecules have a large contact area with a conductive carbon surface, and therefore, enable fast charge transfer at the contact interface. RuCp2 is oxidized to RuCp2+ during charging, and RuCp2+ is pulled to the oppositely (i.e., negatively) charged counter electrode. This attractive force incurs desorption of RuCp2, but ionic liquids shield the attractive force. Consequently, the hybridization realizes a volumetric capacity enhancement with balancing high power density and long cycle lifetimes.

Comparative Study on Electrochemical Treatment of Cyanide Wastewater.

The electrochemical treatment of wastewater is widely used for cleaning due to its efficiency. In this paper, two-dimensional (2D) and three-dimensional (3D) electrochemical systems were used to treat cyanide wastewater. The effect of the applied voltage and the material of the main electrode on the removal of various ions and the characteristics of chemical reactions were mainly studied. The results show that the applied voltage was the key effect of the electrochemical treatment process. The removal of ions from the wastewater at 2 V is mainly due to the effect of electro adsorption and enrichment precipitation, while at 4 V, it is mainly due to anodization and cathodic deposition. The treatment effect of the 3D electrode system was significantly better than the 2D system. The 3D electrode system by used granular activated carbon as the particle electrode, with the carbon filled stainless mesh (CM) and coal based electrode (CB) as the main electrode, the treatment effect were better than main electrode of stainless steel mesh (M). The 3D system with CB as the main electrode had an applied voltage of 4 V, a treatment time of 5 h, plate spacing of 10 mm, and the dosage of activated carbon particles was 2 g. The removal rates of CNT, Cu, Zn, CN−, and SCN− were 94.14, 94.53, 98.14, 98.55, and 93.13%, respectively. The main reaction in anode was the electroly oxidation of CN− and SCN−, while the electrolytic deposition of Cu, Zn, and other metal ions in the cathode surface. There were not only adsorption and electric adsorption of various ions, but also an electrolytic deposition reaction of Cu, Zn, and other metal ions on the surface of the activated carbon particle electrode. During the electrochemical reaction, the concentration of hydrogen ions near the anode increases locally, which produces the precipitation of CuSCN, Cu2Fe(CN)6, and Zn2Fe(CN)6, etc. in the solution, which are helpful for the removal of cyanide and heavy metal ions in cyanide wastewater.

Aplikasi Karbon Aktif dari Cangkang Kelapa Sawit Sebagai Adsorben pada Minyak Jelantah Bahan Sabun

Standart soap quality in SNI 06-3532-1994 is a max water content of 15%, max free fatty acids 2.5% of the number of soaps 196-206 mg/gr in addition there are quality parameters that are not included in the SNI is many foams. Meanwhile, some industrial companies in Indonesia attract consumers with a lot of foam produced by the company's products.The purpose of this study is to discuss the effect of the size of the active carbon particles of palm shells on the reduction of free fatty acids in jelantah oil as the manufacture of soap raw materials and soap quality. determination of Free Fatty Acids using AOCS Ca 5a-40-1997 method, testing moisture content using SNI method 06-3532-1994, The number of hoardings uses the volumetric method. The results of this study showed that particle sizes of 100 mesh and 120 mesh occurred significant differences in the decline of free fatty acids. Where the particle size of 120 mesh is stronger absorbency in lowering Free Fatty Acids. this is because materials with smaller diameters have a greater absorption rate. This is related to the surface area of the activated carbon adsorbent of the palm shell that is available to interact with the substance contained in the solution. But there is no significant difference in the quality of soap, namely; Water Rate, Lots of Foam, Number of Hoarding.

An Investigation of Tensile and Thermal Properties of Epoxy Polymer Modified by Activated Carbon Particle

In this work, the effects of adding activated carbon (AC) powder with epoxy resin were investigated experimentally. The particulate epoxy composites are manufactured in vacuum technique with different weight fraction ratios of AC (0, 5, 10, 15, 20, 25, 30, 35 and 40) % wt. The particle size was measured during this work by laser particle size analyzer with an average size of about (14.74μm). The interaction between epoxy material and AC powder was examined by using Fourier Transform Infrared (FTIR) spectroscopy analysis. Moreover, the glass transition temperature (Tg) of the pure epoxy and composite material were measured by Differential Scanning Calorimeter (DSC). The tensile strength behavior and interaction strength between the matrix material and powder were investigated by conducting tensile test and SEM analysis. The results of FTIR test reveal that there is no a new peak after reinforcing epoxy with AC powder, which proves there is a strong interaction between epoxy resin and AC powder. The DSC results show that the increases by adding AC to epoxy will increase Tg temperature. The findings of FTIR analysis were supported by SEM analysis, which shows a good interaction and strong interfacial between matrix and particles. The tensile strength values increased with increasing AC content up to 15 % wt. with a max value of 26.34 MPa (19.16%), then it decreased to 18.15 MPa at 40 % wt.

Effect of preparation conditions on gas permeability parameters of porous SiC ceramics

The influence of binder content, firing temperature, SiC particle size, activated carbon content and activated carbon particle size on gas permeability parameters of porous SiC ceramics were investigated according to their pore structure performances and microstructure. The influencing degree of these preparing conditions on gas permeability parameters were also compared. The results showed that Darcian permeability parameter k1 and non-Darcian permeability parameter k2 increase with increasing of SiC particle size, activated carbon content and activated carbon particle size, but with decreasing of binder content and firing temperature. Binder content and activated carbon particle size have more significant effects on k1 than other three preparing conditions which their influencing degree in descending order are activated carbon content, SiC particle size and firing temperature. The influencing degree of preparing conditions on k2 and k1/k2 are ambiguous, but it is clear that SiC particle size have largest influence on k2 and k1/k2.

Correction to “Experimental Study of the Effect of Different Parameters on the Adsorption and Desorption of Trichloroethylene Vapor on Activated Carbon Particles”

Trichloroethylene (TCE) is used as a solvent in various industrial processes. During its use, TCE vaporizes and its vapor pollutes the working atmosphere. Its recovery is very important and activated carbon may be used for this purpose. In the present study, experiments were conducted with activated carbon particles for adsorption and desorption of TCE vapor. The adsorption isotherms were measured over a temperature range of 30-100 °C. Also, the effects of particle sizes (dp; 355, 500, and 710 μm), initial concentration of TCE vapor (100, 150, 200, and 250 ppm), and temperature (30, 50, and 100 °C) on the adsorption isotherms of TCE on activated carbon with air as the carrier stream were investigated, which were not reported earlier. From the experimental results, it was found that as the particle size decreases the adsorption capacity increases because of the increase in surface area with decrease in size of particles. The effect of the initial concentration of TCE vapor showed proportionality with adsorption capacity. The increase in temperature showed increase in the adsorption capacity. The adsorption isotherms obtained from the experimental results were compared with model isotherms viz. Langmuir and Freundlich. The Langmuir and Freundlich isotherm models showed accurate fits with R2 values of 0.99067 and 0.99142, respectively, suggesting a hybrid adsorption mechanism involving monolayer and multilayer adsorption. From the desorption study, it was found that the recovery of TCE-vapor from activated carbon is possible, and hence its reuse. This study confirms the suitability of activated carbon as an adsorbent for the removal of TCE vapors emitted from industrial and domestic sources. The details of the experiments and results are discussed in this article.

Неспецифическая резистентность телят на фоне антенатального применения кормовой пробиотической добавки

The article presents the results of studies on the use of a feed additive containing live sporeforming bacteria Bacillus subtilis and live yeast Saccharomyces cerevisiae, sorbed on activated carbon particles, to pregnant cows for the formation of immunoglobulins in the body and their isolation in colostrum, as well as for the nonspecific resistance of the resulting calves. The experiments were conducted in the winter-spring period, when the body of cows and calves contains a reduced level of nutrients, immunoglobulins and other biologically active substances, which leads to inhibition of the function of both nonspecific resistance factors and specific immunity. It was found that the feed additive had a positive effect on the physiological and biochemical parameters of calves. In the colostrum of cows of the experimental groups, relative to the animals of the control group, the content of immunoglobulins was 36.4% higher. Calves whose mothers received a feed additive for 30 days at a dose of 20 g per head before calving had higher indicators of total protein, albumins, globulins and factors of nonspecific resistance, such as bactericidal and lysozyme activity of blood serum, phagocytic activity of neutrophils.

Stray particles as the source of residuals in sand filtrate: Behavior of superfine powdered activated carbon particles in water treatment processes

Although superfine powdered activated carbon has excellent adsorption properties, it is not used in conventional water treatment processes comprising coagulation–flocculation, sedimentation, and sand filtration (CSF) due to concerns about its residual in treated water. Here, we examined the production and fate of very fine carbon particles with lacking in charge neutralization as a source of the residual in sand filtrate after CSF treatment. Almost all of the carbon particles in the water were charge-neutralized by coagulation treatment with rapid mixing, but a very small amount (≤0.4% of the initial concentration) of very fine carbon particles with a lesser degree of charge neutralization were left behind in coagulation process. Such carbon particles, defined as stray carbon particles, were hardly removed by subsequent flocculation and sedimentation processes, and some of them remained in the sand filtrate. The concentration of residual carbon particles in the sand filtrate varied similarly with that of the stray carbon particles. The stray and residual carbon particles were similarly smaller than the particles before coagulation treatment, but the residual carbon particles had less charge neutralization than the stray carbon particles. The turbidity of water samples collected after sedimentation was not correlated with the residual carbon concentration in the sand filtrate, even though it is often used as an indicator of treatment performance with respect to the removal of suspended matter. Based on these findings, we suggest that reduction of the amount of stray particles should be a performance goal of the CSF treatment. Examining this concept further, we confirmed that the residence time distributions in the coagulation and flocculation reactors influenced the concentration of stray carbon particles and then the residual carbon particle concentration in sand filtrate, but found that the effect was dependent on coagulant type. A multi-chambered-reactor configuration lowered both the stray carbon particle concentration after coagulation treatment and the residual carbon particle concentration in sand filtrate compared with a single-chambered reactor configuration. When a normal basicity PACl that consisted mainly of monomeric Al species was used, the stray carbon particle concentration was decreased during coagulation process and then gradually decreased during subsequent flocculation process because the monomeric Al species were transformed to colloidal Al species via polymeric Al species. In contrast, when a high-basicity PACl that consisted mostly of colloidal Al species was used, coagulation treatment largely decreased the stray carbon particle concentration, which did not decrease further during subsequent flocculation process. These findings will be valuable for controlling residual carbon particles after the CSF treatment.

Decolourisation of Beet Sugar Syrup Using Activated Carbon and Glucose Oxidase Enzyme

This paper presents the development and optimization of a new approach which combines the utilization of activated carbon and glucose oxidase enzyme for decolourisation of beet sugar syrup. The combining of the physical adsorption with the enzymatic reaction was managed to improve the decolourisation of beet sugar syrup from 35.29 to 83.68% compared to the basic adsorption by activated carbon after 120 min of operation under the optimum conditions. The maximum decolourisation efficiency by the coupled process was achieved at glucose oxidase dosage of 0.07 g, glucose concentration of 20 mM, and solution pH 7 at the temperature of 30ºC using 0.01 g of activated carbon particles. Given the high effectiveness, reusability, and the eco-friendly nature of the process, the proposed method can serve as an alternative to ordinary decoloursation techniques.

Hydroxyapatite nanoparticle functionalized activated carbon particle electrode that removes strontium from spiked soils in a unipolar three-dimensional electrokinetic system

Biohazard performance of Sr radionuclide can be significantly magnified by its release from the contaminated sedimentation. In this study, hydroxyapatite nanoparticle-functionalized activated carbon electrode (AC-HAP) was synthesized and stacked to the cathode compartment of the electrokinetic (EK) system to develop a unipolar three-dimensional (3D) electrochemical process for Sr2+ removal from spiked soils. Sr2+ adsorption by AC-HAP can be fitted by the pseudo-first-order and pseudo-second-order kinetic models and the Langmuir, Freundlich, and Temkin isotherm models. The largest monolayer adsorption capacity of AC-HAP of 69.49 mg g−1 was evaluated in the pH range of 10–12 and at 40 °C. 3D EK further intensified the adsorption process of AC-HAP and the corresponding Sr2+ removal from aqueous environments. Voltage gradients and proposing time had a significant effect on the migration and transmission of Sr2+ in the electrolyzer. The influence of competitive ions on Sr2+ removal in the stock solutions followed Al3+ < Mg2+ < K+ < Na+ < Ca2+ while followed Al3+ < Na+ < K+ < Mg2+ < Ca2+ in 3D EK. The first three cycles for AC-HAP had taken roughly 50% of the reusability percentage. Sr2+ removal from spiked samples in 3D EK was achieved by acid dissolution, electromigration, and selective uptake on particle electrode.

Practical Aspect of Electrophoretic Deposition to Produce Commercially Viable Activated Carbon Supercapacitor Electrode

Recent years are seeing many published evidences in the successful electrophoretic deposition (EPD) of energy storage electrodes (notably electrodes for lithium-ion battery [1], solid-state electrolyte [2] supercapacitor [3] and flow batteries [4,5]), but their advancement for industrialization are still far from actual adoption [6]. An obvious reason is because the deposited thickness of the coating’s layer in these studies are very thin (less than 1 mm), which give the extreme performance values that are attributed to a complete utilization of low-density active materials (< 1 mg cm-2) for fast accessibility of electrons and ions through the thin layer to the current collector surface. While these fundamental studies are useful for identifying the maximum achievable properties, they are absolutely impractical for any commercial applications which demand thick layers (50 to 80 µm) and high-density active materials (5 to 20 mg cm-2) to provide usable capacity at all power extraction capabilities.This is particularly true for a packed supercapacitor device whereby it is essential to account for the entire mass of the system, which include current collectors, separators, electrode films, binder, electrolyte, connectors and packing materials [7]. This applies even if the estimation is based upon industrial-level active material mass loadings of 10 mg cm-2 or beyond. In such circumstances, the active material mass is only about 30% of the total weight of the device [8]. This means that the system performance calculated from the electrode property has to be divided by 3 or 4 [9]. The divisor is raised to 30 if a thinner electrode having a mass loading of 1 mg cm-2 is employed [7]. Thus, sufficient mass loading of an electrode is required to lower overheads from inactive materials, which can ensure a decent electrochemical performance for a supercapacitor.In view of closing the knowledge gap between fundamental studies and commercial applications, this presentation will show the practical aspects of energy storage electrodes produced by EPD (Figure 1). Activated carbon (AC) particles are sourced from a commercial supplier, and used as an exemplary system of supercapacitor investigation. Practical supercapacitor electrodes with industrially relevant parameters are demonstrated, specifically high-density active material and thick coating layers. This presentation will discuss: (a) formulation of colloidal electrolyte containing activated carbon particles, (b) methodologies and processes of electrophoretic deposition, (c) use of 2D foil vs 3D microporous structure as deposition substrate, (d) impact of post-process calendaring on electrode properties, and (e) electrochemical cycling activities in coin cell assembly, in particular cyclic voltammogram, capacitance, current density, electrochemical impedance spectroscopy and cycle number in comparison to the performance of a scaled-up AC electrode in an A7 sized pouch cell. Overall, this presentation will emphasize the practical aspects of EPD for producing high-quality commercially viable supercapacitors.

Highly Efficient Flow-Electrode Capacitive Deionization Utilizing High-Aspect Ratio Functionalized Carbon Nanotubes

Flow-electrode-based capacitive deionization (FCDI) has attracted much attention owing to its continuous and scalable desalination process without the need for a discharging step, which is required in conventional fixed-electrode capacitive deionization. However, flow electrode slurry is poorly conductive, which restricts desalination performance, but higher carbon mass loading in the slurry could improve salt removal capacity due to enhanced connectivity. However, increased viscosity restricts higher loading of active materials. Herein, we report a significant increase in salt removal performance by introducing functionalized carbon nanotubes (FCNTs) into activated carbon (AC)-based flow electrodes, which led to the generation of conducting bridges between AC particles. The salt removal rate in the presence of 0.25 wt% FCNT with 5 wt% AC improved four-fold from that obtained with only 5 wt% AC, which is the highest value reported in the literature so far (from 1.45 to 5.72 mmol/m2s, at a saline water concentration of 35.0 g/L and applied potential of 1.2 V). Further, FCNTs with a high aspect ratio (~50,000) can more effectively enhance salt removal than low-aspect ratio FCNTs (~1300). Electrochemical analysis further confirms that the addition of FCNTs can efficiently form a connecting percolation network, thus enhancing the conductivity of the flow electrode slurry for the practical application of highly efficient desalination systems.

Understanding the Performance of Flow-Electrodes for Capacitive Deionization through Hydrodynamic Voltammetry

Flow-electrode capacitive deionization is a promising approach to scale up this desalination technology, because of its ability to regenerate the electrodes outside the main cell, and thereby remove a higher amount of salt from the feed water using carbon slurries as flowable electrodes. Previous works have focused on improving the performance by changing the flow-electrode composition or by proposing different cell designs, using a wide range of volumetric flow rates for the electrode, as well as performing mathematical and experimental modelling considering the slurries as Newtonian fluids. In this work, hydrodynamic voltammetry is used to understand the electrochemical behaviour of the carbon slurries, to develop an optimization method that will give an improved electrochemical performance of the slurries. Results show that the apparent viscosity of the slurries must be considered to explain the behaviour of the slurry within the cell, as well as the effect of shear thinning on the migration of activated carbon particles inside the slurry. A dimensionless number is proposed to define a threshold that will ensure a capacitive behaviour of the flow-electrode. Figure 1

Physical Properties of Furfural Resin-Based Active Carbon for Improved Electric Double Layer Capacitor

Specific surface area, pore size distribution and surface functional group of carbonaceous material for electric double layer capacitor (EDLC) are controlling factors to improve energy density. High specific surface area would lead to high specific capacitance, however some micropores (smaller than 2 nm) may be inaccessible to electrolyte ions due to the narrow pore gate effect at the pore entrance, thereby resulting in specific capacity reduction. Surface functional groups also affect the wettability of the activated carbon electrode and pseudo-capacity was yielded due to redox reaction. The relationships between capacity and multiple factors (i.e., specific surface area, pore size distribution, and surface functional groups) are still unclear. In this study, the specific surface area was fixed at 1200 ± 100 m2/g to eliminate the influence of specific surface area on specific capacity. The influences of pore size distribution and surface functional groups on specific capacity were then evaluated.Furfural resin-based particles (1 µm in diameter) were carburized in a nitrogen atmosphere for 3 h at a temperature ramping rate of 1°C/min to 400°C. The carbonized particles were mixed with KOH at a KOH:carbonized particles ratio of 4:1; the mixture was then activated at 700–800°C for the prescribed holding time, ranging from 0 to 0.5 h, under flowing nitrogen gas at a temperature ramping rate of 10°C/min. After heat treatment had been performed, the active carbon was cooled to room temperature, washed with 1 M HCl, rinsed with distilled water, and dried in an oven at 150ºC for 24 h. Specific surface area/pore size distribution was evaluated by N2 adsorption method. Surface functional groups were evaluated by Boehm method. Active carbon, carbon black and polytetrafluoroethylene were mixed at a mass ratio of 8: 1: 1, then pellets (14 mm in diameter and 2 mm in thickness) were prepared and dried at 115ºC for 24 hours to obtain activated carbon electrodes. Constant current charge/discharge test (potential width: 0-1.0 V, current density: 20-500 mA/g) and was performed at room temperature by two-electrode cell using KOH aqueous solution (6 M) as an electrolytic solution.Table 1 shows the pore structure of 1-μm-diameter active carbon particles treated at 700–800°C for different holding times to set SBET at ca. 1200 m2/g, allowing elucidation of the factor controlling the specific capacity. For a holding time of 0.5 h, the specific surface area (SBET) and total pore volume (Vtot) increased with increasing activation temperature. We found that increasing the holding time led to higher Vmicro and lower Vmeso. The three experimental conditions (700°C-0.5 h, 750°C-0 h, and 800°C-0 h) yielded active carbons with an SBET of 1200 ± 100 m2/g; these are indicated by the orange squares in Table 1. Active carbon by 750°C-0 h or 800°C-0 h had 2 to 3 times larger Vmeso and 1.9 times larger mesopore ratio than the one with 700°C-0.5 h. Specific capacity per weight increases in the order of 750ºC-0 h (148 F/g), 800ºC-0 h (111 F/g), and 700ºC-0.5 h (66 F/g). Figure 1 shows pore size distribution of these active carbons. Although 750ºC-0 h, 800ºC-0 h have similar pore size distributions, specific capacity per weight are very different. This indicates that factors other than pore structure may have a great influence on specific capacity per weight.Figure 2 shows the quantitative results of acid-base surface functional group by acid-base back titration (Boehm method). The total amount of acidic groups increased from 700°C-0.5 h (2.48 mmol/g), 800°C-0 h (2.45 mmol/g) to 750°C-0 h (2.21 mmol/g) and correlates with the large of the capacity. The fractional order of carboxyl groups increased from 750°C-0 h (18.1%), 800°C-0 h (23.0%) to 700°C-0.5 h (31.4%). The increase of carboxyl would be one possible reason for better specific capacity. Carboxyl groups cause pseudo-capacity due to redox reaction and improve wettability, and contribute to high capacity. From these relationships, we assumed that the amount of surface functional groups has a larger influence on the capacity than the pore structure. Figure 1

(Invited) Separation and Hydrogenation of Ions By Micro-Scale Capacitive-Faradaic Adsorbing Fuel Cells

Capacitive deionization processes are aimed at separation of ions from water and wastewater. Since late 1960-s, when the CDI concept was proposed, the technique was improved via incorporation of ion exchange membranes (MCDI), utilization of slurry electrodes (FCDI) and introduction of one or two battery electrode(s) into the process to enhance the salt adsorption capacity of the cell and to reduce the energy demand of the process. In all these processes the monopolar electrodes must be physically connected to the DC power supply via wires, and cathodes and anodes should be separated to prevent short-circuiting. These and other requirements of CDI processes result in serious drawbacks, limitations and sophisticated design of water treatment reactors.A novel CDI-based method for separation of ions from water and wastewater using micro-scale (10µm – 5 mm) fuel cells is proposed1. The fuel cells comprise activated carbon particles loaded with bi-functional catalyst for hydrogen oxidation and oxygen reduction reactions. Within the proposed process of ions removal, the particles act as the micro-scale capacitive-faradaic adsorbing fuel cells (MS-CF-AFC) which require oxygen and hydrogen gases for adsorption of ions during the water treatment step and desorption of ions in brine production.Within the O2-induced adsorption of anions, thereduction of oxygen on Pt (faradaic electrode of the MS-CF-AFC) results in depletion of electrons from the carbonaceous part (i.e. the capacitive electrode) of the micro-scale fuel cell, which leads to adsorption of anions in the electrical double layer of carbon. The hydrogen oxidation that occurs during the regeneration of the anions-loaded MS-CF-AFCs results in accumulation of electrons in the capacitive electrode and in repulsion of perchlorate ions into the regenerant solution. This way the chemical energy of H2 and O2 is converted by the MS-CF-AFCs into the electrical energy which is utilized for separation of ions. For the separation of cations, the MS-CF-AFCs are powered by the H2 gas during the cationsadsorption step and by the O2 gas in brine production.The O2-induced adsorption of anions (and desorption of cations) results in pH increase in the treated water. Consequently, within the MS-CF-AFC treatment the separated anions are “exchanges” with OH- ions. The rate of the process is faster at lower pH values in the treated water. Higher anions adsorption capacity is achieved at higher O2 pressure. The H2-induced desorption of anions (and adsorption of cations) is accompanied by decrease in the pH. Thus, the cations removal process can be regarded as an exchange of separated cations with the H+ ions. The H2-induced step of the MS-CF-AFC processes is faster at higher pHs, and higher cations removal capacity is obtained at higher H2 pressure. To enhance the salt adsorption capacity of MS-CF-AFCs for anions and cations the activated carbon in the cells can be decorated with appropriate surface groups, e.g., carboxylic and amine groups (respectively).The process was proved for the removal of perchlorate, copper and nitrate ions using pure solutions of NaClO4, KNO3 and CuCl2 salts in deionized water and in groundwater, using batch and packed-bed reactors for two types of platinum loaded (5wt%) MS-CF-AFCs prepared from Lewatit AF5 microporous carbon and a powdered activated charcoal.The main disadvantage of the process described above is its inability to “deactivate” toxic NO3 - and ClO4 - ions as the process only concentrates the pollutant (similarly to the well-known ion-exchange). It was shown that Pt-Cu MS-CF-AFCs are capable to adsorb nitrate ions from water and to reduce them into the N2 gas during the H2-induced step of anions desorption from the MS-CF-AFCs.The proposed MS-CF-AFCs can be performed in batch, continuous stirred (CSTR), fixed-bed and other types of reactors normally applied in adsorptive water treatment processes.Potential advantages of the MS-CF-AFCs process are: (1) the process can be utilized for separation of all types of anions and cations (appropriate carbon modification might be required); (2) the process can be performed in any type of adsorption reactors; (3) desalinating hybrid capacitive-faradaic micro-scale fuel cells do not require any wiring as opposite to CDI, previously proposed desalinating fuel cells and battery electrode desalination processes; (4) the regeneration of the MS-CF-AFCs does not require any concentrated solutions of acids, bases or salts; and (5) the hydrogen required for the process can be produced on-site using hydrogen generators and air can be utilized as the oxygen source.[1] Gendel, Y., Amikam, G., Nativ, P., 2020. Separation of Anions and Cations from Water and Wastewater Using Micro-Scale Capacitive-Faradaic or Pseudocapacitive-Faradaic Adsorbing Fuel Cells. US Provisional Patent Application 62/983,689. Figure 1

Phosphate selective recovery by magnetic iron oxide impregnated carbon flow-electrode capacitive deionization (FCDI)

The recovery of phosphorus (P) from wastewaters is a worthy goal considering the potential environmental and economic benefits. Flow-electrode capacitive deionization (FCDI), which employs flowable carbon electrodes instead of the static electrodes used in conventional CDI, has been demonstrated to be a promising P recovery technology. FCDI outperforms CDI and other competitive technologies in a number of aspects including (i) large salt adsorption capacity and (ii) extremely high water recovery rate. In this study, magnetic (Fe3O4 impregnated) activated carbon particles were prepared and applied as FCDI electrodes. The magnetic carbon electrodes were found to have a strong affinity towards P, facilitating the selective adsorption of P to the magnetic particles through a ligand exhange mechanism. Continuous operation of the FCDI system could be achieved with only three minutes required to separate the electrode particles from the brine stream on application of an external magnetic field. A P-rich stream was produced on regeneration of the exhausted magnetic electrodes using alkali solution. We envision that the use of magnetic carbon enhanced flow-electrodes will pave the way for efficient operation of FCDI as well as the preferential recovery of P.

Synthesis of manganese (IV) oxide at activated carbon on reduced graphene oxide sheets via laser irradiation technique for organic binder-free electrodes in flexible supercapacitors

We report a novel, green, scalable technique to synthesize binder-free, high-purity conductive composite comprising activated carbon (AC), manganese dioxide nanorods (MnO2), and reduced graphene oxide sheets (rGO) for flexible supercapacitors with outstanding electrochemical performance. UV pulsed laser irradiation of GO-based composite dispersion (AC/GO or MnO2@AC/GO) in ethanol aqueous medium was used to induce a photocatalytic reduction of GO and simultaneous anchor AC particles or AC loaded MnO2 nanorods (MnO2@AC) on the reduced GO sheets (rGO) at room temperature and atmospheric pressure. rGO sheets serve as a large surface area, conductive binder to enhance the ion adsorption, electrical conductivity, and mechanical flexibility of supercapacitor electrodes. This laser-induced photocatalytic reduction method was used to prepare two different rGO-based colloidal composites AC/rGO (CG) and MnO2@AC/rGO (MCG). The prepared rGO-based colloidal composites were used to fabricate symmetric supercapacitors (CG//CG and MCG//MCG) and asymmetric supercapacitors (MCG//CG) in which MCG is the positive electrode and CG is the negative one. All prepared rGO-based supercapacitors demonstrated significant improvement in their electrochemical performance compared with rGO-free AC based supercapacitors. The enhancement in the electrochemical properties of rGO-based supercapacitors could be attributed to the intrinsic characteristics of rGO, such as high surface area, excellent electrical conductivity, and super mechanical flexibility. Our approach is a one-step, scalable, cost-effective synthesis technique to produce all binder-free AC/rGO based composites for flexible energy-storage devices.

Highly active and controllable MOF-derived carbon nanosheets supported iron catalysts for Fischer-Tropsch synthesis

N-doped carbon materials as catalyst supports have shown great superiority because of rich porosity, tunable metal-support interaction and electronic promotion effect. Controllable fabrication of carbon materials with specific morphology and different configurations provides wider possibilities for applications in catalysis. Herein, N-doped carbon nanosheets (CNS) were successfully synthesized by using monoclinic ZIF-8 nanosheets as templates. Compared with commercial active carbon and cubic ZIF-8 particles-derived carbon particles, the derived CNS exhibit superior graphitization degree and electronic effect. Consequently, the promoted Fe carburization improved the intrinsic activity for Fe/CNS catalysts in FTS. Further investigation on pyrolysis temperature achieved tunable configuration and content of N dopant. XPS, Raman, Mössbauer spectroscopy, TEM, H2-TPR etc. were combined to elucidate the promotion effect of CNS on dispersion, electronic properties and formation of Fe carbides. By correlating the composition and structure to catalytic performance in FTS, we illustrated the significance of carbon materials in Fe supported catalysts.

Study of the pore size effect on the charge storage of hydrous RuO2 nanoparticles supported within the pores of activated carbon

Hydrous ruthenium oxide (RuO2) nanoparticles are hybridized inside the pores of activated carbon (AC) for preparing electrochemical capacitor electrodes. The hybridization consists of the adsorption of an organoruthenium complex and subsequent heat treatment to reduce the complex into Ru nanoparticles within the AC pores, followed by the electrochemical oxidation of the resulting Ru nanoparticles into hydrous RuO2 nanoparticles. Two kinds of AC with only micropores and both micropores and mesopores of ~4 nm are examined to study the effects of pore sizes on the charge/discharge characteristics of the AC/RuO2 hybrids. Since the introduction of hydrous RuO2 nanoparticles is not accompanied by the volumetric expansion of the AC particles, the volumetric capacity is enhanced in comparison with the pristine AC. However, the capacitance retention at high charge/discharge rates is decreased by micropores or an excessive amount of the hydrous RuO2 nanoparticles. This method is free from the use of any organic solvent, concomitant solvent removal and drying process, or reducing and oxidizing reagents, and therefore, can be used to synthesize porous carbon/metal oxide nanoparticle hybrids for versatile applications.