Adsorption Values Research Articles

Ammonium Removal in Wastewater Treatments by Adsorbent Geopolymer Material with Granite Wastes: Full-Scale Validation

Elevated ammonium (NH4+) concentrations in untreated waterways contribute to eutrophication and dissolved oxygen depletion. Geopolymer (GP) materials are introduced as sustainable, straightforward operation and low-cost option for pollutant adsorption through ion exchange mechanism. In the present study, a porous metakaolin-based geopolymer with granite waste additions was synthetized, characterised and validated as adsorbent material for NH4+ pollution in water. At this point, treatments to reduce GP alkalis leaching were also considered to comply with the water discharge regulations. The adsorption mechanism was analysed by Redlich-Peterson isotherm model concluding that NH4+ was disposed on the GP surface as a monolayer with strong physical-chemical attraction between molecules. Kinetics of the process followed the Weber-Morris rate equation being the intraparticle diffusion the limiting process. Continuous experiments at lab-scale suggested a maximum removal of 97% during the first hours and an adsorption capacity (q) of 25.24 mg/g. Additionally, as a main novelty of the work, the GP was validated in a full-scale pilot plant monitoring pH, electrical conductivity and NH4+ concentration. The obtained data revealed that the GP is high selective in a real wastewater stream and removed 81% of NH4+, higher adsorption values than those reported for natural and some synthetic zeolites.

Assessing the carcinogenic and non-carcinogenic health risks of metals in the drinking water of Isfahan, Iran

Metals are significant contributors to water pollution, posing serious threats to human health. This study aims to assess the carcinogenic and non-carcinogenic health risks associated with metals in Isfahan drinking water. Eighty water samples were randomly collected from the city's distribution network between January and March 2020–2021. Inductively coupled plasma Optical Emission Spectrometry was used to measure toxic metals, namely Pb, Cr, Cd, Ni, and As concentrations. Results revealed that the mean concentration of Ni (70.03 µg/L) exceeded the WHO reference value (70 µg/L), while the other metals were below the standard values. The average chronic daily intake order of toxic metals was Ni > Cr > Pb > As > Cd. Non-carcinogenic risk assessment through hazard quotient (HQ) and hazard index (HI) demonstrated that both THI for adults (HQingestion + HQdermal = 4.02E−03) and THI for children (HIingestion + HIdermal = 3.83E−03) were below the acceptable limit (less than 1). This indicated no non-carcinogenic risk to residents through water ingestion or dermal exposure. However, findings indicated that the ingestion route was the primary exposure pathway, with HQ values for ingestion exceeding HQ values for dermal adsorption. Carcinogenic risk assessment showed that the risk associated with As metal exceeded the acceptable limit (1 × 10−6). Therefore, implementing treatment improvement programs and appropriate control measures is essential to safeguard the health of Isfahan City residents.

Composite Layered Double Hydroxide Zn-Al/Magnetic Biochar Modified for Highly Effective Malachite Green Adsorption

One of the main needs of humans is water, one source of water pollutantion is from dyes. Adsorption is the most popular method in removing pollutants as it is proven to be efficient. One of the dyes harmful to living things is malachite green. In this study, malachite green dye was removed using a layered double hydroxide (LDH) Zn-Al/magnetic biochar composite. The XRD, FTIR, BET, and VSM analyses show that the LDH Zn-Al, magnetic biochar, and LDH Zn-Al/magnetic biochar composite were successfully produced. The surface area of the Zn-Al/magnetic biochar composite made up of LDH increased from 9.621 m2/g to 99.473 m2/g. The point of zero charge of LDH Zn-Al and magnetic biochar were at pH 6, whereas the composite of these two materials was at pH 7. For LDH Zn-Al, magnetic biochar, and composite LDH Zn-Al/magnetic biochar, pH 8 is the ideal value for adsorption of malachite green. PSO (pseudo-second order) kinetics is the best-fit model. LDH Zn-Al, magnetic biochar, and LDH Zn-Al/magnetic biochar composite had adsorption capacities of 14.472, 15.552, and 25.907 mg/g, respectively, at a temperature of 60°C. Regeneration showed the LDH Zn-Al/magnetic biochar composite had superior and more effective ability compared to LDH Zn-Al and magnetic biochar.

Nitrogen Removal from Landfill Leachate Using Biochar Derived from Wheat Straw.

Landfill leachate (LLCH) disposal poses challenges due to high pollutant concentrations. This study investigates the use of biochar (BC) derived from wheat straw for nitrogen content reduction. Laboratory experiments evaluated BC's adsorption capacity (qm) for nitrogen removal from ammonium chloride solution (NH4Cl) and LLCH, along with testing isotherm models. The results demonstrated that BC was more efficient (95.08%) than commercial activated carbon AC (93.11%), the blank, in adsorbing nitrogen from NH4Cl. This superior performance of BC may be attributed to its higher carbon content (57.74%) observed through elemental analysis. Lower results for BC/LLCH may be due to LLCH's complex chemical matrix. The Langmuir isotherm model best described BC/NH4Cl adsorption (qm = 0.5738 mg/g). The AC/NH4Cl data also fitted into the Langmuir (R2 ˃ 0.9) with a qm of 0.9469 mg/g, and 26.667 mg/g (R2 ˂ 0.9) was obtained for BC/LLCH; the BC/LLCH also gave higher qm (R2 ˃ 0.9) using the Jovanovich model (which also follows Langmuir's assumptions). The mean energy of the adsorption values estimated for the AC/NH4Cl, BC/NH4Cl, and BC/LLCH processes were 353.55, 353.55, and 223.61 kJ/mol, respectively, suggesting that they are all chemisorption processes and ion exchange influenced their adsorption processes. The Freundlich constant (1/n) value suggests average adsorption for BC/LLCH. The BC/LLCH data followed the Harkins-Jura model (R2: 0.9992), suggesting multilayered adsorption (or mesopore filling). In conclusion, biochar derived from wheat straw shows promising potential for landfill leachate remediation, offering efficient nitrogen removal capabilities and demonstrating compatibility with various adsorption models. This research also lays the groundwork for further exploration of other biochar-based materials in addressing environmental challenges associated with landfill leachate contamination.

Synthesis of Functionalized Flexible and Rigid Polyurethane for Oil Spill Treatment

Abstract. To improve the oleophilic and hydrophobic properties of two different types of polyurethane sponge (flexible, FPU, and rigid, RPU) for oil spill cleanup, acrylamido phenyl chalcone palamitamid, a recently synthesized monomer with long chains of linear alkyl groups, was in situ crosslinked with divinylbenzene. Grafted PU cubes were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The water sorption of ungrafted FPU and RPU decreased from 18.05 and 15.66 to 7.31 and 7.06 for grafted FPU and RPU, respectively. The effect of oil type on the sorption capacity testing was explored and compared using crude oil, diesel fuel, and water-oil systems. It was found that the crude oil and diesel fuel sorption of grafted FPU and RPU cubes was increased compared with ungrafted FPU and RPU cubes, and the maximum values for adsorption were recorded using crude oil. These results can be explained by increasing the adherent forces between the adsorbent and the oil surface with increasing oil viscosity, and consequently, the oil adsorption increases. The high oil absorption capacity is mainly attributed to the high porosity of the sponges. The modified FPU and RPU cubes can be effectively used in oil and water spill cleanup.

DNA Adsorption Capabilities of Amine Functionalized Magnetic Cellulose Acetate Butyrate Beads from Aqueous Solution

AbstractIn this work, the magnetic cellulose acetate butyrate beads (mCABs) were prepared and then, their surfaces were modified with [(3‐Aminopropyl) triethoxysilane)] (APTES) solution to generate amine groups (−NH2) as a ligand for DNA adsorption in the aqueous solution. After the surface modification, the −NH2 functionalized mCABs (N−mCABs) were characterized with Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscope (SEM), and energy dispersive X‐ray (EDX) analysis. The optimum pH value of DNA adsorption was observed at pH 4 and at this point, the N−mCABs adsorbed 4.27 mg/g DNA at room temperature (RT). The maximum adsorbed amount of DNA was calculated as 5.24 mg/g and the DNA adsorption was exothermic; furthermore, DNA adsorption was monolayer and the Langmuir adsorption model was more fitted than the Freunclich isotherm model due to the regression coefficient (R2), and the qmax values of the Langmuir model. According to reusability studies, the prepared adsorbent protected its stability and the adsorption capacity after the 5 consecutive adsorption, desorption, and regeneration cycles.

Invariant Molecular Representations for Heterogeneous Catalysis.

Catalyst screening is a critical step in the discovery and development of heterogeneous catalysts, which are vital for a wide range of chemical processes. In recent years, computational catalyst screening, primarily through density functional theory (DFT), has gained significant attention as a method for identifying promising catalysts. However, the computation of adsorption energies for all likely chemical intermediates present in complex surface chemistries is computationally intensive and costly due to the expensive nature of these calculations and the intrinsic idiosyncrasies of the methods or data sets used. This study introduces a novel machine learning (ML) method to learn adsorption energies from multiple DFT functionals by using invariant molecular representations (IMRs). To do this, we first extract molecular fingerprints for the reaction intermediates and later use a Siamese-neural-network-based training strategy to learn invariant molecular representations or the IMR across all available functionals. Our Siamese network-based representations demonstrate superior performance in predicting adsorption energies compared with other molecular representations. Notably, when considering mean absolute values of adsorption energies as 0.43 eV (PBE-D3), 0.46 eV (BEEF-vdW), 0.81 eV (RPBE), and 0.37 eV (scan+rVV10), our IMR method has achieved the lowest mean absolute errors (MAEs) of 0.18 0.10, 0.16, and 0.18 eV, respectively. These results emphasize the superior predictive capacity of our Siamese network-based representations. The empirical findings in this study illuminate the efficacy, robustness, and dependability of our proposed ML paradigm in predicting adsorption energies, specifically for propane dehydrogenation on a platinum catalyst surface.

Preparation and characterization of cellulose-based activated carbon by cesium chloride chemical method

Carbon adsorbent material with a specific surface area as high as 436 m2/g was prepared by chemical activation method using cellulose as raw material and cesium chloride as activator, and its structure was characterized. Its adsorption performance on methylene blue solution was investigated, and the adsorption thermodynamics of crystalline violet dye at different temperatures was studied. The results showed that the surface of the prepared activated carbon material was smooth with abundant pores. The methylene blue adsorption value was as high as 176 mg/g, and it could adsorb methylene blue solution quickly and efficiently. It had good adsorption effect on crystal violet solution, the saturated adsorption amount reaches 281 mg/g at 40 °C, and the removal reached 92%, which indicated a self-heating adsorption reaction. Thus, CsCl could be used as an activator of wood raw material for the preparation of activated carbon samples.

Preparation and characterization of polyvinyl chloride based carbon materials with high specific surface area

Using PVC as raw material and KOH as activator, the carbon adsorption material with ultra-high specific surface area up to 5677.2 m2/g was prepared by chemical activation method, and its structure was characterized to study its adsorption performance on methylene blue solution; the activated mixture was analyzed for chlorine element and the recovery of chlorine element was calculated. The results show that the surface of the obtained activated carbon material is in the shape of smooth lotus root flakes with well-developed pore structure; the adsorption value of methylene blue adsorption can reach 765.0 mg/g, which can adsorb methylene blue solution quickly and efficiently; the elemental chlorine can be recovered efficiently with a recovery rate of 95.33 %, which can effectively reduce the toxic hydrogen chloride gas produced in the process of PVC pyrolysis. Excellent adsorption capacity of H2, CO2 and CH4. This experiment can provide an effective method for the harmless treatment of PVC.

RATE AND SELECTIVITY OF HYDROGENATION OF 2-NITRO-2'-HYDROXY-5'-METHYLAZOBENZE OVER NICKEL CATALYST IN AQUEOUS SOLUTIONS OF ALIPHATIC ALCOHOLS

Elucidation of the causes and character of the composition and nature solvent influence on the kinetic regularities and selectivity of hydrogenation reactions of compounds containing several reactive groups is of theoretical and practical significance. In the present work, the process of 2-nitro-2'-hydroxy-5'-methylazobenzene catalytic hydrogenation in the liquid phase is considered in order to obtain the corresponding benzotriazole, an effective UV stabilizer of polymeric materials. The process was carried out on a skeletal nickel catalyst in aqueous solutions with different contents of aliphatic alcohols, both at atmospheric and elevated hydrogen pressures. It has been experimentally established that the shape of the hydrogenation kinetic curves is determined by the composition of the water-alcohol solvent and is transformed from the dependence with a maximum in media with low alcohol content to the stepped curve in concentrated solutions. The dependences of the reaction rate on the content of aliphatic alcohol are complex, and the maximum hydrogenation rates are observed in solvents with a content 0.6÷0.7 ppm. of alcohol. The change in the process rate is associated with a change in the solubility, value of adsorption and reactivity of the starting compound and hydrogen. These factors also determine the selectivity of the process due to their influence on the rates of individual steps in the 2-nitro-2'-hydroxy-5'-methylazobenzene conversion scheme, in particular, on the cyclization rate of the associative surface complex "nitroazobenzene∙H2". The cyclization product of the complex is an intermediate compound, benzotriazole N-oxide, the reduction of which leads to the formation of a substituted benzotriazole. It is shown that the maximum yield of the target product is 48÷3% at atmospheric hydrogen pressure, and increases to 73.5-0.5% at PН2 = 1 MPa.

ИССЛЕДОВАНИЕ АДСОРБЦИИ МОЛЕКУЛ ВОДЫ НА КАЛЬЦИЙСОДЕРЖАЩИХ МАТЕРИАЛАХ МЕТОДАМИ ФИЗИКО-ХИМИЧЕСКОГО АНАЛИЗА

Physico-chemical methods of analysis were used to study calcium-containing materials - water systems. Samples of calcium-containing materials - micromarble of RIF, Koelga, OMUA grades, as well as silicate glass - were studied. The structural characteristics of the studied materials were determined on the basis of the analysis of experimental isotherms of water vapour adsorption obtained by the isopiestic method at 298 K. It was found that the adsorption isotherms of water vapour adsorption on the studied materials have a shape intermediate between II and III type according to Brunauer's classification, which is characteristic of adsorption on non-porous and macroporous adsorbents. The analysis of adsorption isotherms showed that they are practically parallel to each other in a wide range (p/ps=0.05-0.85), in the region of high relative pressures of adsorbent a rise of adsorption isotherm for silicate glass is observed. The identical type of isotherms for micromarbles is explained by the similarity of chemical structure of samples, small differences in the values of adsorption indicate a small difference in the values of specific surface area and particle size of materials. It is shown that adsorption of water vapour on the surface of the samples occurs with the formation of complexes - clusters consisting of calcium carbonate molecules surrounded by adsorbate molecules due to the formation of hydrogen bonds between the surface oxygen and sorbed water molecules. In the framework of theoretical models, sorption and structural parameters of adsorbent and adsorbate were determined from linearised forms of Langmuir and BET equations linking sorption values and relative vapour pressures of adsorbate. NMR-relaxation parameters of sorbed water protons were measured on a spectrometer with a working frequency of 20 MHz. According to NMR data, the relationship between spin-spin and spin-lattice relaxation times and the state of adsorbed water molecules was established. The character of dependences of spin-spin (T2) and spin-lattice (T1) relaxation times of adsorbed water on the value of water sorption (W) indicates the influence of specific surface area and size of adsorbent particles on the mobility of adsorbed water molecules and confirms the mechanism of cluster formation during adsorption of water vapour on calcium-containing materials.

A facile method for synthesis of bismuth oxide nanoparticles on anion exchange resin and its salt removal ability for saline water

In this work, a method was applied to produce bismuth oxide nanoparticles on anion exchange resin (AR@Bi2O3), which was then applied effectively for removing salts in aqueous solution of NaCl and real-world saline water. The results from SEM, EDX, XRD, and FTIR confirm the preparation of AR@Bi2O3 with a crystalline structure and high purity as well as the effective adsorption of salt on the surface of the material. The salt removal was investigated under various conditions of contact time, solution pH, adsorbent mass, initial salt concentration, and solution temperature. The salt adsorption of AR@Bi2O3 reached an equilibrium capacity of 280 mg/g after 45 min, which is best described by the intraparticle diffusion model. Moreover, pH 5 was found to be the optimal value for salt adsorption and Freundlich is the best model for describing the adsorption process, which was a spontaneous process (∆G < 0). The adsorption capacity of the AR@Bi2O3 material likely remained stable at over 260 mg/g even after 10 cycles of adsorption-regeneration, indicating a great potential for practical application of AR@Bi2O3 in saline water treatment.

Aluminium phosphide (Al12P12) nanocage as a potential sensor for volatile organic compounds: A DFT study.

The efficacy of aluminium phosphide (Al12P12) nanocage toward sensing methanol (MeOH) and ethanol (EtOH) volatile organic compounds (VOCs) was herein thoroughly elucidated utilizing various density functional theory (DFT) computations. In this perspective, MeOH⋯ and EtOH⋯Al12P12 complexes were investigated within all plausible configurations. According to the energetic features, the EtOH⋯Al12P12 complexes exhibited larger negative values of adsorption and interaction energies with values up to -27.23 and -32.84 kcal mol-1, respectively, in comparison to the MeOH⋯Al12P12 complexes. Based on the symmetry-adapted perturbation theory (SAPT) results, the electrostatic forces were pinpointed as the predominant component beyond the adsorption process within the preferable MeOH⋯ and EtOH⋯Al12P12 complexes. The findings of the noncovalent interaction (NCI) index and quantum theory of atoms in molecules (QTAIM) outlined the closed-shell nature of the interactions within the studied complexes. Substantial variations were found in the molecular orbitals distribution patterns of MeOH/EtOH molecules and Al12P12 nanocage, outlining the occurrence of the adsorption process within the complexes under investigation. Thermodynamic parameters were denoted with negative values, demonstrating the spontaneous exothermic nature of the most favorable complexes. New energy states were observed within the extracted density of states plots, confirming the impact of adsorbing MeOH and EtOH molecules on the electronic properties of the Al12P12 nanocage. The appearance of additional peaks in Infrared Radiation (IR) and Raman spectra revealed the apparent effect of the adsorption process on the features of the utilized sensor. The emerging results declared the potential uses of Al12P12 nanocage as a promising candidate for sensing VOCs, particularly MeOH and EtOH.

Biochar from Manihot esculenta stalk as potential adsorbent for removal of reactive yellow dye

Textile effluent treatment is crucial for a cleaner and safer community. The purpose of this study is to utilize biochar prepared from Manihot esculenta stalk to remove reactive yellow dye through Pyrolysis at 350 °C for 210 min. The effect of quantity of adsorbent, pH values of the adsorbate solution experimented, contact time required, starting dye concentration, current temperature of the solution, speed of agitation, as well as size of the particle on reactive yellow dye removal was examined using biochar through batch trials. At an equilibrium period of 25 min, pH of 7, bio-char dosage of 2 g, temperature of 25 °C, agitation speed of 150 rpm, as well as particle size of 231 µm, 86% of the dye could be removed with highest adsorption capacity of 53.47 mg/g. Pseudo-first order type kinetics in addition to the Langmuir isotherm model were set up to finest fit the adsorption model of reactive yellow dye onto biochar from M. esculenta stalk. The process is chemisorption, exothermic, feasible, and spontaneous, as it is predicted by the thermodynamically negative enthalpy as well as entropy of adsorption values. The spent M. esculenta stalk biochar was reused for six cycles of adsorption at same optimal process conditions and adsorption capacity was found to be insignificant up to fourth cycle. Also, M. esculenta biochar was characterized through scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX) and Fourier Transform Infrared Spectroscopy (FTIR) for morphology, elemental composition, and functional groups respectively. So, the M. esculenta stalk biochar could be an active adsorbent for elimination of reactive dye from the solution of dye.

Characterization of Addition Porang on Polyacrylamide Polymer for Enhanced Oil Recovery

The main purpose of polymer injection is to reduce the water-oil mobility ratio. By increasing the viscosity of the injection fluid, polymer injection can increase sweep efficiency, thereby increasing oil recovery. This study aims to determine the viscosity and adsorption effects of adding porang to polyacrylamide polymers. The method used in this research is a laboratory experiment. The salinity of the formation water used in this study was 6000 ppm, 12000 ppm, and 18000 ppm, with variations in polymer concentrations of 2000 ppm, 4000 ppm, and 6000 ppm on the polymer without a mixture of porang and with a mixture of porang. The result of measuring the viscosity of polyacrylamide by adding porang at the salinity of 6000 ppm and polymer concentration of 6000 ppm was 21.82 cp. With the addition of porang to the polyacrylamide polymer at 2000 ppm concentration and 18000 ppm salinity, the adsorption value of the polymer decreased from 2.708 mg/gr to 1.748 mg/gr for 40 mesh sand and from 3.333 mg/g to 2.358 mg/g for 60 mesh sand.

Sulfonated mesoporous polystyrene-1D multiwall carbon nanotube nanocomposite as potential adsorbent for efficient removal of xylene isomers from aqueous solution

Xylene isomers are notorious chemical hazards, and their efficient removal from water solutions is still challenging. The current study reports a polymer nanocomposite as a potential adsorbent for successfully removing dissolved xylene isomers from contaminated water. Polystyrene-1D multiwall carbon nanotube nanocomposite (PS-MWCNT) adsorbent was prepared using the one-step bulk polymerization method. Mesoporous PS-MWCNT was prepared using the nano-crystallization phase separation method. The sulfonation of the mesoporous PS-MWCNT nanocomposites was carried out by treating the samples with concentrated sulfuric acid at elevated temperatures. The sulfonated PS-MWCNT (HO3S-PS-MWCNT) was found to be a potential adsorbent for dissolved xylene isomers from water solution. In addition, the HO3S-PS-MWCNT can be efficiently recycled for up to 10 consecutive cycles with negligible decline in adsorption values. The exhibited equilibrium adsorption, rate of adsorption, and rapid regeneration of the HO3S-PS-MWCNT are clear indications for the possibility of practical utilization of these adsorbents in large-scale water treatment plants.

Neurotransmitter amino acid adsorption on metal doped boron nitride nanosheets as biosensor: DFT study on neural disease prediagnosis system

In this study, pristine and iron (Fe), copper (Cu) and platinum (Pt) metal doped boron nitride nanosheet (BNNS) structures possibility of biosensor, adsorbent and neural disease prediagnosis system for gama amino butyric acid (GABA) and Glutamate (Glu) molecules were investigated by Density Functional Theory (DFT). Metal atoms were doped to replace both boron (B) and nitrogen (N) atoms of BNNS. All the adsorption energies on the structure were calculated as negative values for all structures after the GABA and Glu adsorption. The lowest adsorption energy and enthalpy values reached to − 42.1 kcal/mol and − 42.7 kcal/mol, respectively. According to Gibbs free energy (∆G) values of adsorption, most of the adsorption reactions can occur spontaneously. The charge transfer during adsorption happened from GABA and Glu molecules to BNNS structures. Based on the results, Fe-doped BNNS and Cu-doped BNNS could be utilized as electronic and work function type biosensors for GABA molecule and Glu molecule respectively. This study may lead to future biosensor studies, adsorption studies of neurotransmitter amino acids other than GABA and Glu, and BN nanostructure studies modified with different metal doping.

Study of sorption of platinum, palladium and rhodium ions on a carbon sorbent

The article is devoted to the sorption concentration of platinum (II,IV), palladium (II) and rhodium (III) ions from chloride media on a carbon synthetic sorbent. For the study of the sorption concentration of platinum group metals, the carbon synthetic sorbent Lewatit AF5 was chosen. This sorbent has high mechanical strength, high surface area, narrow pore size distribution, and low cost compared to silicate or polymer sorbents. Sorption concentration was carried out under static conditions from model chloride solutions. The concentration of analytes in the initial solutions ranged from 8 to 50 mmol/dm3. Equilibrium concentrations of metals in solutions were determined by inductively coupled plasma atomic emission spectrometry. The dependences of adsorption on contact time, free acidity and redox potential of the system were studied, and the limiting absorption values for each of the metals studied were determined. The study of the kinetic parameters of the sorption of Pt (IV), Pd (II) and Rh (III) ions was carried out from chloride solutions characterized by free acidity values of 0.01 mol/dm3. The time for establishing sorption equilibrium was determined, which was 4 hours for each of the ions. When studying the dependence of adsorption on free acidity and the oxidation-reduction potential of the system (ORP), it was revealed that with an increase in free acidity and redox potential, a decrease in sorption activity is observed, thus we can conclude that aquated complexes of platinum metals, in which metals present not in the highest oxidation state, involved in the sorption process. Processing of experimental data showed the applicability of the linear equation of the Langmuir isotherm for the description of the adsorption process, the limiting adsorption values were calculated, using which the sorption capacity of the sorbent was assessed. The sorption capacity for Pt (II, IV), Pd (II) and Rh (III) was 1.24 mmol/g; 1.16 mmol/g and 0.57 mmol/g, respectively. High values of sorption capacity, as well as a fairly short time to achieve sorption equilibrium without the use of means for the acceleration of the process, in combination with the mechanical characteristics of the sorbent, allow us to conclude that the Lewatit AF5 sorbent is promising for the concentration of platinum group metals from hydrochloric acid solutions.

What Controls Activity Trends of Electrocatalytic Water Splitting? - Activation Energy Vs. Frequency Factor

Electrocatalytic water splitting is a topic of investigation of numerous research groups for decades. Oxygen evolution reaction (OER), as a more complex and more demanding reaction, is more frequently studied, despite of the fact that the simpler hydrogen evolution reaction (HER), is generally not well understood. Nowadays, recurrent approach to electrocatalysis is conquest for more active and more stable electrode materials, very often lacking significant input to better understanding of reaction mechanisms or understanding of what are the drivers of electrocatalytic activity [1].Importantly, if one asks the key question from the conceptual point of view, and that is: what are the origins of electrocatalytic activity? - the answer will be, in the predominant majority of cases, like 70 years ago. Namely, paradigm of electrocatalysis is Sabatier principle, that suggests optimal (“not too strong, not too weak”) binding of intermediates as main precondition of high reaction rate [2]. Conventional wisdom suggests that confirmation of this should be relatively simple. Namely, Brönsted-Evans-Polanyi (BEP) relations suggest linear relationship between adsorption energy of key intermediates and activation energy. In other words, if we have reliable values of adsorption energies relevant for the electrochemical environment [3], they should form linear dependence with experimentally obtained activation energies.However, high-temperature hydrodynamic experiments on HER indicate that reducing of activation energy by tuning of adsorption energy of intermediates is not necessarily beneficial for enhancement of HER rate. Namely, HER rate is strongly influenced by preexponential frequency factor. Therefore, we propose discussion that will analyse several key aspects of HER electrocatalysis: 1) interplay of activation energy and preexponential factor as a driver of electrocatalytic activity 2) are BEP relations relevant for electrocatalysis 3) can we assess adsorption energies experimentally 4) what are relevant descriptors that shed light on HER activation process, 5) what else is important beyond Sabatier principle for rate of HER [1-7]. Figure 1. Graphical illustration of four interfacial descriptors relevant for HER. Adapted from Ref. [4] with permission from the PCCP Owner Societies, under the terms and conditions of the Creative Commons Attribution 3.0 Unported License.

Electrochemical Ion Separations By Recyclable Electrode Cell

Electrochemical separations using Faradaic electrodes are able to exceed the ion adsorption values as well as selectivity when compared to capacitive electrodes, which is due to the bulk reactions for the former vs. surface confined for the latter. However, the cyclability of battery/faradaic electrodes is constrained to hundreds or a few thousands of cycles. This work proposes an electrochemical ion pumping design with the unique feature of using injectable electrodes to overcome the ciclability issue and easily control the areal capacity. The idea consists on using injectable electrodes with the intention of recycling the active material once the end-of-life of the device is reached due to active material degradation. In this fashion, the active material is replaced in a straightforward deinjecting-injecting process allowing direct reuse of the inactive components of the device, thus contributing to reducing the replacement cost. This device is called Ion Pumping Injectable Cell (IPIC).Moreover, the IPIC system is a tremendously versatile technology due to the simple and easy methodology employed to replace the electrodes. In this fashion, the system was tested using different types of lithium intercalation materials (LFP and LMO), different ion capturing such as potassium (Prussian Blue Analogs, PBA´s), sodium (NMO) or more conventional activated carbon electrodes (capacitive non-selective electrode). In addition to this feature, it is important to remark that the IPIC could be used in a symmetric (e.g. LFP-LFP) or asymmetric configuration (e.g. LFP-LMO). The main difference is that the asymmetric system has the ability of storing energy while capturing ions and deliver that energy in the subsequent step. This is so due to the different electrode potential. The selectivity toward specific ions is achieved by using a chemical ion-selective separator such as an ion exchange membrane (LFP-LFP or LFP-LMO systems), or by using ion selective intercalation materials such as LFP and PBA´s without the need of selective membranes.In this work, the benefits of the injectable electrode cell architecture will be examined, the performance of different cell configurations will be discussed and the electrochemical ion separation mechanism will be analyzed for different applications. Acknowledgements : J.J. Lado and Alba Fombona-Pascual acknowledge Comunidad de Madrid for the fellowship (2020-T1/AMB-19799).