Desorption Research Articles

Determination of dissociation constants via quantitative mass spectrometry

The interplay of biomolecules governs all cellular processes. Qualitative analysis of such interactions between biomolecules as well as the quantitative assessment of their binding affinities are essential for the understanding of biochemical mechanisms. As scientific interest therefore moves beyond pure structural investigation, methods that allow for the investigation of such interactions become increasingly relevant. In this perspective we outline classical methods that are applicable for the determination of binding constants and highlight specifically mass spectrometry based methods. The use of mass spectrometry to gain quantitative information about binding affinities however is a still developing field. Here, we discuss different approaches, which emerged over the last years to determine dissociation constants (KD) with mass spectrometry based methods. Specifically, we highlight the recent development of quantitative Laser Induced Liquid Bead Ion Desorption (qLILBID) mass spectrometry for the example of double stranded deoxyribonucleic acids as well as for different RNA—RNA binding protein systems. We show that quantitative laser induced liquid bead ion desorption can successfully be used for the top down investigation of complexes and their dissociation constants values ranging from low nM to low µM affinities.

OLYMPIA-LILBID: A New Laboratory Setup to Calibrate Spaceborne Hypervelocity Ice Grain Detectors Using High-Resolution Mass Spectrometry

The coupling of an Orbitrap-based mass analyzer to the laser-induced liquid beam ion desorption (LILBID) technique has been investigated, with the aim to reproduce the mass spectra recorded by Cassini's Cosmic Dust Analyzer (CDA) in the vicinity of Saturn's icy moon Enceladus. LILBID setups are usually coupled with time-of-flight (TOF) mass analyzers, with a limited mass resolution (∼800 m/Δm). Thanks to the Orbitrap technology, we developed a unique analytical setup that is able to simulate hypervelocity ice grains' impact in the laboratory (at speeds in the range of 15-18 km/s) with an unprecedented high mass resolution of up to 150 000 m/Δm (at m/z 19 for a 500 ms signal duration). The results will be implemented in the LILBID database and will be useful for the calibration and future data interpretation of the Europa Clipper's SUrface Dust Analyzer (SUDA), which will characterize the habitability of Jupiter's icy moon Europa.

Selective Sorption of Cerium Ions from Uranium-Containing Solutions by Remotely Activated Ion Exchangers.

This study investigated the effect of the remote activation of the ion exchangers Amberlite IR120 (H+ form) and AV-17-8 (OH- form) in aqueous media to increase the sorption activity of the interpolymer system "Amberlite IR120H:AV-17-8" (X:Y, molar ratio of ionic groups) towards cerium ions from uranium-containing solutions. The sorption properties of the above-mentioned interpolymer system with molar ratios X:Y of 6:0, 5:1, 4:2, 3:3, 2:4, 1:5, and 0:6 were studied using the methods of conductometry, gravimetry, and inductively coupled plasma-optical emission spectrometry. The presented research revealed the dependence of the sorption activity of the interpolymer system "Amberlite IR120H:AV-17-8" (X:Y) on the acidity of the solution. At pH 2.0, the highest cerium ion sorption degree from the model solution (containing both cerium and uranium ions) by the interpolymer system "Amberlite IR120H:AV-17-8" (4:2) was 56% after 48 h of interaction, whereas the cerium ion sorption degrees by raw Amberlite IR120H (6:0) and raw AV-17-8 (0:6) were 30% and 0%, respectively. The increased sorption ability of the interpolymer system "Amberlite IR120H:AV-17-8" (4:2) might be associated with the achievement of the highest ionization degree by this system remotely activated in an aqueous medium. Moreover, the cerium ion desorption study demonstrated a 60% degree of desorption using 2M nitric acid as a desorbing agent (eluent). The obtained results demonstrate the potential of using the remote interaction effect for the activation of the ion exchangers in aqueous media as an interpolymer system for increased cerium ion sorption from uranium-containing solutions.

Converting wastes to resource: Preparation of NiO@γ-Al2O3 sludge composite from aluminum-containing sludge for cadmium removal from wastewater

Solid sludge waste and heavy metal water pollution have attracted great interest due to the adverse impacts on the ecological environment, which remains a significant challenge to environmental protection. Herein, with the concept of converting wastes to resources, this work presents a general procedure to fabricate NiO@γ-Al2O3 sludge composite derived from aluminum-containing sludge for efficient cadmium removal. During the procedure, the unstable metal compounds were converted into chemically stable metal oxides, and the organic components in sludge are decomposed via high-temperature treatment. Then, the NiO@γ-Al2O3 sludge composite was obtained by in situ growth of NiO nanocrystals using the calcined sludge as raw materials, followed by calcination to form a porous structure. The as-obtained NiO@γ-Al2O3 sludge composite with hierarchical porosity comprises self-assembled NiO nanosheets with sizes ranging from 1 to 3 μm. Compared with raw sludge particles, the specific surface area of NiO@γ-Al2O3 sludge composite is enhanced significantly (116.27 m2/g), revealing that the preparation procedure is favorable for the improvement of the surface properties of the sludge. The cadmium adsorption results showed that the maximum cadmium adsorption capacity of the sludge composite could attain 160.12 mg/g, and cadmium removal efficiency could reach 99.9% with an optimal dose of 1.5 g/L. Meanwhile, the sludge composite showed high adsorption capacity at the neutral pH condition, which was attributed to the exchange of cadmium ions in solution with the surface protons on the adsorbent. Significantly, a simple regeneration operation was used for the desorption of cadmium ions to realize the regeneration of adsorbents, and the regenerated sludge composite can be recyclable for continuous use. This work provides a waste-to-resource strategy for resource utilization of solid waste sludge and presents an adsorbent material with high surface activity for cadmium adsorption, which may inspire the development and application of other solid waste for wastewater treatment.

Efficient removal of Cs ion by electrochemical adsorption and desorption reaction using NiFe Prussian blue deposited carbon nanofiber electrode.

Prussian blue (PB) analog (NiFe, CoFe, FeFe, and commercial(cPB)) decorated carbon nanofiber (CNF) electrodes were synthesized by the drop casting method in this study to investigate the interaction between PB and CNF for the electrochemical adsorption (EA) and electrochemical desorption (ED) of Cs ion (Cs+). The adhesion of PB on the electrode and the EA and ED of Cs+ were substantially higher when the CNF electrode was used, compared with the fluorine-doped tin oxide supporting electrode. The use of CNF led to the smooth occurrence of EA and ED of Cs+, where the reported efficiency was: NiFe >FeFe >cPB. The EA and ED of Cs+ on NiFe decorated CNF (C-NiFe) were strongly affected by the loading amount of NiFe. Although the strongest EA capacity was identified when 1mg of NiFe was used, it decreased as the loading amount of NiFe increased. Thus, the EA of Cs+ occurs under the reduction of NiFe with some Fe(III) reduced to Fe(II) of NiFe, thus inducing more adsorption of Cs+. Overall, we confirmed that the C-NiFe electrode with appropriate thickness of NiFe layer is potentially an excellent adsorbent for Cs removal.

Nano-flower-like porous carbon derived from soybean straw for efficient N-S co-doped supercapacitors by coupling in-situ heteroatom doping with green activation method

The interlayer nanoflower porous carbon was prepared in this paper by coupling green and sustainable liquefied with in-situ doping using soybean straw as a biomass precursor. The pore structures of the obtained samples were reasonably controlled with non-toxic potassium citrate. The specific surface area of SSL-N/S-K-800 reaches 1756.74 m2 g−1, and the microporosity is 75.38%. In the three-electrode system test, SSL-N/S-K-700 exhibits a specific capacitance of 220 F g−1 at a current density of 0.5 A g−1. Moreover, in the two-electrode system test, the SSL-N/S-K-700 assembled symmetric supercapacitor exhibits an energy density of 11.24 W h kg−1 at a power density of 400 W kg−1. Notably, excellent cycling stability (capacitance retention > 99.2%) is presented after 10,000 cycles. The superior electrochemical properties are attributed to the ion diffusion channels provided by the macropores and mesopores, and the abundant micropores can provide ion adsorption and desorption sites. Additionally, the synchronizing N S doping effectively enhances the pseudo-capacitance of the material. This work explores a green, efficient and sustainable approach for achieving high value-added utilization of waste biomass and enhancing the energy density of supercapacitors for electrochemical energy storage.

The synthesis and super capacitive characterization of microwave-assisted highly crystalline α-Fe2O3/Fe3O4 nanoheterostructures.

A facile microwave-assisted solvothermal process for the synthesis of narrow-size distributed α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 nanostructures was demonstrated using PVP as a surfactant. During the reaction, the influence of the reaction media, such as the mixture of ethylene glycol and water on the formation of α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 was systematically studied. Interestingly, pure aqueous medicated solvothermal reaction conferred phase pure rhombohedral Fe2O3 (hematite) and linearly upsurging the formation of cubic Fe3O4 (magnetite) with the increasing concentration of EG and further, in pure EG, it deliberated cubic Fe3O4. FESEM and FETEM images of α-Fe2O3/Fe3O4 nano heterostructure clearly showed the nanosized Fe3O4 particles of 4-6 nm decorated onto Fe2O3 nanoparticles. Further, the electrochemical properties of α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 nanoparticles were investigated with galvanostatic charge-discharge and cyclic voltammetry measurements using a 3-electrode system. The findings show that their specific capacitances are linked to the type of iron oxide. More significantly, the α-Fe2O3/Fe3O4 nanoheterostructure exhibited the utmost capacitance of 165 F g-1, which is greater than that of pristine α-Fe2O3 and Fe3O4. Enhancement in the electrochemical performance was found due to the improved charge transfer that occurred at the interface of the nanoheterostructure. The nanoparticles of Fe3O4 deposited on the Fe2O3 increased the active sites, which accelerated the process of adsorption and desorption of ions, thereby enhancing the interface-assisted charge transfer and reducing the internal resistance, which is ultimately responsible for enhanced capacitance. Such heterostructures of nano iron oxide may fulfill the requirements of electrodes in supercapacitors.

Role of surface chemistry in conditioning of materials in particle accelerators

For the vacuum scientists and the accelerator community, finding solutions to mitigate pressure rises induced by electron, photon and ion desorption, and also beam instabilities induced by ion and electron clouds is a major issue. Along the time, changes in the surface chemistry of vacuum chambers are observed during beam operations, leading to modifications of: outgassing rates, stimulated desorption processes and secondary emission yields (SEY). To understand the role of the surface chemistry of air exposed materials in the electron conditioning process, typical air exposed materials used in particle accelerators : thin film coatings (NEG, i.e a Ti-Zr-V alloy, and carbon), copper (and its oxides Cu2O and CuO) and niobium were conditioned by low energy electron irradiation for a better understanding of electron-cloud effect. First, SEY was measured to understand the changes of surface conditioning upon particle irradiation; then, surface chemistry evolution after electron irradiation was investigated by both XPS and TOF-SIMS analyses using the ANDROMEDE facility at IJCLab. Finally, the relationship between the surface chemistry and the conditioning phenomenon will be discussed.

Iron Oxides Nanoparticles as Components of Ferroptosis-Inducing Systems: Screening of Potential Candidates

This study presents an analysis of a set of iron oxides nanoparticles (NPs) (γ-Fe2O3, α-FeOOH, δ-FeOOH, 5Fe2O3·9H2O, and Fe3O4) as potential candidates for ferroptosis therapy in terms of a phase state, magnetic characteristics, and the release of Fe2+/Fe3+ as ROS mediators. Due to the values of saturation magnetization for Fe3O4 (31.6 emu/g) and γ-Fe2O3 (33.8 emu/g), as well as the surface area of these particles (130 and 123 m2/g), it is possible to consider them as promising magnetically controlled carriers that can function with various ligands. The evaluation of the release of Fe2+/Fe3+ ions as catalysts for the Fenton reaction showed that the concentration of the released ions increases within first 3 h after suspension and decreases within 24 h, which probably indicates desorption and adsorption of ions from/onto the surface of nanoparticles regardless their nature. The concentration of ions released by all nanoparticles, except α-FeOOH-Fe2+, reached 9.1 mg/L for Fe3+ to 1.7 mg/L for Fe2+, which makes them preferable for controlling the catalysis of the Fenton reaction. In contrast, a high concentration of iron ions to 90 mg/L for Fe3+ and 316 mg/L for Fe2+ released from compound α-FeOOH-Fe2+ allows us to utilize this oxide as an aid therapy agent. Results obtained on iron oxide nanoparticles will provide data for the most prospective candidates that are used in ferroptosis-inducing systems.

Sulfur-Doped Binary Layered Metal Oxides Incorporated on Pomegranate Peel-Derived Activated Carbon for Removal of Heavy Metal Ions.

In this study, a novel biomass adsorbent based on activated carbon incorporated with sulfur-based binary metal oxides layered nanoparticles (SML-AC), including sulfur (S2), manganese (Mn), and tin (Sn) oxide synthesized via the solvothermal method. The newly synthesized SML-AC was studied using FTIR, FESEM, EDX, and BET to determine its functional groups, surface morphology, and elemental composition. Hence, the BET was performed with an appropriate specific surface area for raw AC (356 m2·g−1) and modified AC-SML (195 m2·g−1). To prepare water samples for ICP-OES analysis, the suggested nanocomposite was used as an efficient adsorbent to remove lead (Pb2+), cadmium (Cd2+), chromium (Cr3+), and vanadium (V5+) from oil-rich regions. As the chemical structure of metal ions is influenced by solution pH, this parameter was considered experimentally, and pH 4, dosage 50 mg, and time 120 min were found to be the best with high capacity for all adsorbates. At different experimental conditions, the AC-SML provided a satisfactory adsorption capacity of 37.03−90.09 mg·g−1 for Cd2+, Pb2+, Cr3+, and V5+ ions. The adsorption experiment was explored, and the method was fitted with the Langmuir model (R2 = 0.99) as compared to the Freundlich model (R2 = 0.91). The kinetic models and free energy (<0.45 KJ·mol−1) parameters demonstrated that the adsorption rate is limited with pseudo-second order (R2 = 0.99) under the physical adsorption mechanism, respectively. Finally, the study demonstrated that the AC-SML nanocomposite is recyclable at least five times in the continuous adsorption−desorption of metal ions.

Study of biochar impregnated with Al recovered from water sludge for phosphate adsorption/desorption

Aluminum ions extracted from water sludge and waste biomass (Korean pine residue) were utilized to develop a biochar for phosphate removal. The biochar impregnated with the extracted aluminum ions adsorbed phosphate from wastewater up to 11.9 mg P/g which is comparable to those of Al2(SO4)3 impregnated biochar (14.3 mg P/g) and AlCl3 impregnated biochar (2.26 mg P/g). Co-existence of anions (HCO3−) deteriorates phosphate adsorption about 15% followed by SO42−, NO3− and Cl−. Phosphate desorption and aluminum ion release from the phosphate saturated Al-biochar were less than 5% in distilled water while they were 65 and 15% in citric acid solution (2%), respectively, in 48 h. Al-biochar also showed the characteristics of slow release P fertilizer which is helpful to protect water environment from eutrophication. Al-biochar using waste KPR and Al ions extracted from water sludge was very effective in removing phosphate from wastewater. In addition, the phosphate saturated biochar showed very high potential for agricultural application as an eco-friendly P fertilizer.

How nanoporous silicon-polypyrrole hybrids flex their muscles in aqueous electrolytes: In operando high-resolution x-ray diffraction and electron tomography-based micromechanical computer simulations

Macroscopic strain experiments revealed that Si crystals traversed by parallel, channel-like nanopores functionalized with the muscle polymer polypyrrole exhibit large and reversible electrochemo-mechanical actuation in aqueous electrolytes. On the microscopical level this system still bears open questions, as to how the electrochemical expansion and contraction of PPy acts on to np-Si pore walls and how the collective motorics of the pore array emerges from the single-nanopore behavior. An analysis of in operando X-ray diffraction experiments with micromechanical finite element simulations, based on a 3D reconstruction of the nanoporous medium by TEM tomography, shows that the in-plane mechanical response is dominantly isotropic despite the anisotropic elasticity of the single crystalline host matrix. However, the structural anisotropy originating from the parallel alignment of the nanopores lead to significant differences between the in- and out-of-plane electromechanical response. This response is not describable by a simple 2D arrangement of parallel cylindrical channels. Rather, the simulations highlight that the dendritic shape of the Si pore walls, including pore connections between the main channels, cause complex, inhomogeneous stress-strain fields in the crystalline host. Time-dependent X-ray scattering on the dynamics of the actuator properties hint towards the importance of diffusion limitations, plastic deformation and creep in the nanoconfined polymer upon (counter-)ion adsorption and desorption, the very pore-scale processes causing the macroscopic electroactuation. From a more general perspective, our study demonstrates that the combination of TEM tomography-based micromechanical modeling with high-resolution X-ray scattering experiments provides a powerful approach for in operando analysis of nanoporous composites from the single-nanopore up to the porous-medium scale.

Quantitative analysis capability of DIUTHAME mass spectrometry verified by acetylcholinesterase enzyme-catalyzed reaction assays.

Matrix-assisted laser desorption/ionization (MALDI) is advantageous for mass spectrometry applications where throughput is important. However, quantitative analysis is essentially problematic for MALDI-MS whose results depend on the intrinsically stochastic microcrystalline state of the matrix. High-throughput screening (HTS) of drug candidates is a typical example that requires high throughput. The application of MALDI-MS to HTS, which is quantitative analysis, imposes restrictions on designing an experimental system. Surface-assisted laser desorption/ionization (SALDI) methods, which do not depend on matrix crystal formation, are expected to be applied to quantitative analyses such as HTS. A recently developed one type of SALDI methods, desorption ionization using through hole alumina membrane (DIUTHAME), possesses a distinct feature that the surface microstructure effective for ionization is formed by through holes. In this study, the quantitative analysis capability of DIUTHAME was verified by applying DIUTHAME to enzyme-catalyzed reaction measurements, which are also used for HTS. Quantitative DIUTHAME-MS was conducted on various conditions of acetylcholinesterase-catalyzed reaction solutions containing cow milk as a substitute of biological media. Even for the enzyme-catalyzed reaction solutions containing complex additives that make the quantitative analysis extremely difficult, DIUTHAME based on the through hole structure enables quantitative measurements of the analytes by applying the reaction solutions to the back side of the laser exposed surface. In comparison with those obtained by MALDI-MS, the results obtained by DIUTHAME-MS showed less variability of data and delivered a better linearity of the Lineweaver-Burk plots and a more reasonable value of the Michaelis constant. Accordingly, it was demonstrated that DIUTHAME-MS possesses the quantitative analysis capability much better than that of MALDI-MS.

Unexpectedly efficient ion desorption of graphene-based materials

Ion desorption is extremely challenging for adsorbents with superior performance, and widely used conventional desorption methods involve high acid or base concentrations and large consumption of reagents. Here, we experimentally demonstrate the rapid and efficient desorption of ions on magnetite-graphene oxide (M-GO) by adding low amounts of Al3+. The corresponding concentration of Al3+ used is reduced by at least a factor 250 compared to conventional desorption method. The desorption rate reaches ~97.0% for the typical radioactive and bivalent ions Co2+, Mn2+, and Sr2+ within ~1 min. We achieve effective enrichment of radioactive 60Co and reduce the volume of concentrated 60Co solution by approximately 10 times compared to the initial solution. The M-GO can be recycled and reused easily without compromising its adsorption efficiency and magnetic performance, based on the unique hydration anionic species of Al3+ under alkaline conditions. Density functional theory calculations show that the interaction of graphene with Al3+ is stronger than with divalent ions, and that the adsorption probability of Al3+ is superior than that of Co2+, Mn2+, and Sr2+ ions. This suggests that the proposed method could be used to enrich a wider range of ions in the fields of energy, biology, environmental technology, and materials science.

Effect of poly-γ-glutamic acid on the phytoremediation of ramie (Boehmeria nivea L.) in the Hg-contaminated soil

Farmlands around the Hg mining areas have suffered from severe Hg contamination issues, triggering a phenomenon of high Hg content in crops, and subsequently threatening human health. In this study, ramie (Boehmeria nivea L.) assisted with poly-γ-glutamic acid (γ-PGA) was employed to remediate the Hg-contaminated soil through incubation experiments. After the soil was amended with γ-PGA, the leaf Hg content increased by 4.4-fold, and the translocation factor value even reached 3.5, indicating that γ-PGA could dramatically enhance the translocation of Hg from root and stem to leaf. γ-PGA could induce the transformation of potentially available Hg to available fractions, resulting in the soil Hg being more bioavailable. Batch trials verified that γ-PGA could mask the adsorption function of Hg ions by soil organic matter, significantly stimulating the desorption of Hg ions from the soil. As a result, the soil Hg would transfer to the aqueous phase and be assimilated by the root of ramie more easily and effectively. The γ-PGA chelated Hg is hydrophilic and has a high affinity with –SH and -S-; thereby, it can easily stride over the Casparian strip, enter the vessel, be translocated upwards, be sequestered in the tissues of leaf, and be incorporated irreversibly. This study can provide a new method for the remediation of Hg-contaminated soil.

Supercritical hydrothermal synthesis of zirconia nanoparticles from zirconium basic carbonate

Zirconia nanoparticles were synthesized by using the supercritical hydrothermal method from zirconium basic carbonate, which is insoluble in water at ambient temperature. The diameters of these nanoparticles were 10–20 nm. They contained both tetragonal and monoclinic phases. A long treatment in supercritical water induced the phase transition from the tetragonal phase to the monoclinic phase with the desorption of carbonate ions. These results indicated that the carbonate ions absorbed on the surface works as a stabilizer of the unstable tetragonal phase. The process developed here allows us to bypass wastewater treatment along with the product refining because byproducts are only water and carbon dioxide.

Complementary Mass Spectral Analysis of Isomeric O-bearing Organic Compounds and Fragmentation Differences through Analog Techniques for Spaceborne Mass Spectrometers

Mass spectrometers on board spacecraft typically use either impact ionization or electron ionization (EI) as ion sources. Understanding the similarities and differences in the spectral signatures and fragmentation patterns produced by different techniques in mass spectrometry could elucidate the composition of organic compounds. Here we present a comparison between the mass spectra obtained through laser-induced liquid beam ion desorption (LILBID; proven to simulate the impact ionization mass spectra of ice grains) and EI mass spectra of pairs of low-mass, isomeric aldehydes and ketones. Our comparison confirms that EI produces more fragmentation of carbonyl compounds, particularly aldehydes, than LILBID. We find protonated molecular ions [M+H]+ in LILBID but molecular ions [M]+ in EI spectra. From the evaluated species, LILBID generally produces oxygen-carrying fragment ions (e.g., [CHO]+ and [C2H3O]+) in the mass ranges 26–30 and 39–44 u, while in EI, most ions in these ranges correspond to hydrocarbon fragments. The LILBID spectra additionally show mostly protonated oxygen-bearing fragments [CH3O]+ and [C2H5O]+ at m/z 31 and 45, less commonly observed in EI spectra. We observe a decrease in the relative intensities of cation fragment mass lines between m/z 26 and 33 and an increase between m/z 39 and 45, with an increasing carbon number for ketones and aldehydes with LILBID and EI, respectively. Our study provides a basis for complementary compositional analysis to identify the structural properties of organic species in a space environment using different spaceborne mass spectrometers (e.g., SUrface Dust Analyzer and MAss Spectrometer for Planetary EXploration) on board NASA’s future Europa Clipper space mission.

Highly selective capacitive adsorption and rapid desorption of arsenic ions in wastewater achieving by a recyclable urchin-like iron-manganese composite electrode

The demand for environmental protection drives researchers to develop new concepts or technologies to solve the problem of heavy metal pollution in wastewater. Herein, we report recyclable CDI electrodes composed of sea urchin-like iron-manganese composites to explore the capacitive adsorption and selective adsorption effects of arsenic ions in the simulated wastewater. Under the operating conditions of 1 mm electrode spacing and 1.2 V voltage, the maximum saturated adsorption capacity of the composite electrode for arsenic ions reached 411.22 mg/g, and when the initial concentration was 20 mg/L, the removal rate of arsenic ions reached 99.7%. Besides, the composite material also showed an excellent selective adsorption capacity under the coexistence of lead and cadmium ions. Finally, this recyclable composite electrode was capable of rapid desorption and can retain 97% of the initial capacity after fifty cycles of adsorption/desorption.

Estimation of sorption-desorption characteristics of biosorbent of Lantana camara leaves for removal of Pb (II) ions from wastewater.

This study points out the method regarding the removal of Pb (II) ions from water by treatment with Lantana camara leaves' biosorbent (LCLB). The sorption process was investigated by varying different parameters pH, contact time, adsorbent dose, initial metal ion concentration, and temperature. For a 5.00g sorbent dose and a 45min of the contact period, a Pb (II) ion solution with an initial metal ion concentration of 10mg/L resulted in 90.7% maximum elimination at an optimum pH 6 and temperature 298 ± 1.5K with LCLB. The adsorption process was spontaneous and exothermic. The maximum monolayer adsorption was 3.5mg/g for Pb (II) sorption using LCLB. Adsorption of Pb (II) ions using LCLB (R2 > 0.999) followed the pseudo-second-order kinetics. The spectroscopic characterization was done byfourier transform infrared (FT-IR) analysis, while scanning electron microscope (SEM) images were captured for the morphological characterization. Desorption experiments revealed that hydrochloric acid has a strong potential as an eluent for Pb (II) ion desorption. The findings proposed that LCLB can be used as an effectual and cost-effective biosorbent for the expulsion of Pb (II) ions.

Study on kinetics and mechanism of Re(VII) ion adsorption and desorption using commercially available activated carbon and solutions containing Se(VI) as an impurity

This paper presents the potential use of carbon sorbents in recovering rhenium(VII) from highly diluted electrolytes. Tests were performed using synthetic solutions containing selenium(VI) as an impurity. Adsorption of Re(VII) is selective with respect to selenium(VI). Activated carbon is a suitable sorbent for rhenium recovery because unlike ion-exchange resins, it has high chemical resistance and osmotic-shock resistance. The results show that the sorption mechanism is complex. Two follow-up processes occurred—physical adsorption and the reduction of Re(VII) to Re(VI). The processes were strongly influenced by the temperature. The lower the temperature, the higher the process efficiency. The observed sorption capacity was as high as 7.6 mg/g at 298 K and decreased as the temperature increased. The adsorption was a mixed-control process. Increasing the temperature altered the rate-limiting process. The activation parameters were determined using rate constant (k) and Arrhenius equation. In the first step, the activation energy was approximately 0 kJ mol−1. In the second step, the activation energy for k2,obs and k3,obs was determined as 57.3 kJ mol−1. The pre-exponential factors were calculated; their value was 2.98 × 107 min−1. For k1,obs, the activation energy was nearly 0 kJ mol−1.