Sorption-desorption Cycles Research Articles

Identification of hydrated phases in ALPO4-5, and explanation of their effect on the water sorption and dynamics

A sequence of phases between structural phases in ALPO4-5, commencing from the 4-coordinated aluminum atoms (tetrahedra) in the bare crystal, up to the formation of 6-coordinated (octahedra), and 5-coordinated (bipyramids) aluminum atoms upon the progressive increase of the sorbate water loading, was identified by means of density functional theory calculations, combined with Rietveld refinement of our measured XRD patterns, and produced a crystallographic information file (CIF) at 313 K and relative humidity 81.5%. We modeled the thermodynamics of the sorbed water at progressively increasing chemical potentials via grand canonical Monte Carlo computations, and explained, on the basis of the formed phases, the hysteresis loop which appears in the gravimetrically measured isotherms of the literature during the sorption-desorption cycles. Molecular dynamics simulations predicted the impact of the existence of hydrated phases on the sorbate water diffusivity; collective diffusivities at the linear response regime were also calculated and thereby, transport coefficients.

Changes in Porous Parameters of the Ion Exchanged X Zeolite and Their Effect on CO2 Adsorption.

Zeolite 13X (NaX) was modified through ion-exchange with alkali and alkaline earth metal cations. The degree of ion exchange was thoroughly characterized with ICP, EDS and XRF methods. The new method of EDS data evaluation for zeolites was presented. It delivers the same reliable results as more complicated, expensive, time consuming and hazardous ICP approach. The highest adsorption capacities at 273 K and 0.95 bar were achieved for materials containing the alkali metals in the following order K < Na < Li, respectively, 4.54, 5.55 and 5.94 mmol/g. It was found that it is associated with the porous parameters of the ion-exchanged samples. The Li0.61Na0.39X form of zeolite exhibited the highest specific surface area of 624 m2/g and micropore volume of 0.35 cm3/g compared to sodium form 569 m2/g and 0.30 cm3/g, respectively. The increase of CO2 uptake is not related with deterioration of CO2 selectivity. At room temperature, the CO2 vs. N2 selectivity remains at a very high stable level prior and after ion exchange in co-adsorption process (XCO2 during adsorption 0.15; XCO2 during desorption 0.95) within measurement uncertainty. Additionally, the Li0.61Na0.39X sample was proven to be stable in the aging adsorption-desorption tests (200 sorption-desorption cycles; circa 11 days of continuous process) exhibiting the CO2 uptake decrease of about 6%. The exchange with alkaline earth metals (Mg, Ca) led to a significant decrease of SSA and micropore volume which correlated with lower CO2 adsorption capacities. Interestingly, the divalent cations cause formation of mesopores, due to the relaxation of lattice strains.

Cyclic performance of coke oven gas - Steam reforming with assistance of steel slag derivates for high purity hydrogen production

Steel slag-derived CaO (CaO(SS)) was applied in cyclic sorption enhanced steam reforming of coke oven gas process (cyclic SE-SRCOG) for high-purity hydrogen production. Effects of leaching acid concentration on the cyclic CO2 capture capacity of CaO(SS) were investigated. Using 1 mol/L acetic acid solution as leaching solution, the prepared CaO-based sorbent showed a stable CO2 capture capacity of 0.27 gCO2/gCaO after 35 sorption-desorption cycles. Impacts of operating modes (with different particles contents and loading patterns), operating procedure, and leaching residue (LR) blending on cyclic SE-SRCOG performance were experimentally investigated in detail. Combined catalyst-sorbent by adhesively tableting exhibited the worst stability due to loss of Ni active sites, caused by severe sintering and coverage by CaCO3. With a reforming temperature of 600 °C, cyclic SE-SRCOG with layered packing catalyst-sorbent particles could achieve H2 purity of 95% and CH4 conversion of 87% at the 5th cycle, and they were still maintained to be 87% and 65% at the 10th cycle, respectively. In operating mode using layered packed catalyst-sorbent particles, integration of LR into the sorbent facilitated further improvements of CH4 conversion to 86% at the 10th cycle, mainly due to that LR could act as catalytic promoters of SRCOG and sintering-resistance spacers of CaO(SS).

Novel disinfection method for toxic cyanobacteria (Oscillatoria tenuis) and simultaneous removal of cyanotoxins aided by recyclable magnetic nanoparticles

An optimized disinfection method with metal ions to address cyanobacteria contamination in freshwater is presented, based on recyclable magnetic nanoparticles. In this study, the disinfection ability of individual metal ions (Ag+ and Cu2+) and combined (Ag+ + Cu2+) were evaluated with a target cyanobacteria, Oscillatoria tenuis, under various environmental conditions. The usage of combined Ag+ and Cu2+ reduces the time and concentration needed to achieve the same disinfection effectiveness compared to individual metal ions. However, the addition of Cu2+ and Ag+ stimulated production of cyanotoxin during disinfection, with an increase of 24.8% for anatoxin-a. To reduce the potential health risk, we evaluated the recovery and reuse of metal ions, and removal of cyanotoxins after disinfection, using magnetic nanoparticles with permanently confined micelle arrays (Mag-PCMA) under various environmental conditions. Recovery efficiency of Ag+, the most valuable ion, was excellent (99.8%), although it decreased to 74.5% with increasing Cl- concentration (0–10 mg/L). The regeneration and reuse of Mag-PCMA was studied for 5 cycles. Removal efficiency of Cu2+, anatoxin-a and cylindrospermopsin were minimally changed during the 5 sorption-desorption cycles, and that of Ag+ remained above 93% by the end of 5th cycle, indicating that this disinfection method may be sustainable for practical use with low energy requirements and minimized environmental impacts.

From green biowaste to water treatment applications: Utilization of modified new biochar for the efficient removal of ciprofloxacin

Water pollution caused by antibiotics is a serious environmental problem in recent years. Using biochar to remove such pharmaceutical pollutants has recently emerged as a promising option. After H3PO4 modification, a new waste-based biochar (MPCWSB500) from sour cherry stalk was successfully synthesized to remove ciprofloxacin (CFX) from aquatic media, and modification of feedstock has significantly improved the adsorption capacity of biochar. MPCWSB500 is suitable for both batch and continuous treatment systems. The CFX sorption was systematically studied using various kinetics and isotherm models. The surface characteristics of the modified biochar and the possible CFX−biochar interactions were investigated by BET, FT−IR, and SEM−EDX analysis. Short operation time, high sorption capacity (410.06 mg g−1), and nearly 100% removal efficiency were recorded as significant findings at optimum experimental conditions (pH: 6.3, contact time: 40 min, MPCWSB500 dose: 15 mg). Furthermore, the modified biochar exhibited more than 95% CFX removal efficiency in continuous mode at all flow rates (1–10 mL min−1). Its sorption performance was minimally affected by the presence of Cl−, K+, Na+, and NO3− ions in the adsorption medium. In addition, up to 5 sorption-desorption cycles, biochar regeneration and recycling produced satisfactory results. The proposed biochar was also successfully used to remove CFX from simulated hospital wastewater and synthetic urine samples. These features are all important advantages for its real applications. Overall, our research offers a practical approach for removing CFX from the polluted aquatic environment.

Polyelectrolytes applied to remove methylene blue and methyl orange dyes from water via polymer-enhanced ultrafiltration

In the present work, polymer-enhanced ultrafiltration (PEUF) was used to study the purification of coloured wastewater. Methylene blue (MB) and methyl orange (MO) dyes were removed from aqueous solutions using water-soluble polymers: poly(2-acrylamide-2-methyl-1-propanesulfonic acid) (PAMPS) and poly(diallyldimethylammonium) chloride (PDDA), respectively. The PEUF technique has the advantage that it can be performed in homogeneous media to clean wastewater, where the novelty focuses on the water-soluble polymers used. Both polymers were first fractionated using an ultrafiltration membrane composed of regenerated cellulose with a molecular weight cut off (MWCO) of 10 kDa followed by subsequent freeze-drying. The removal of both dyes by ultrafiltration in the absence and presence of polymer was systematically studied. The performance of the polymers was studied under different parameters, such as the effect of the MWCO for the ultrafiltration membrane, the pH of the solution, the polymer:dye molar ratio, the initial dye concentration, the interference effect of NaCl and Na2SO4, and consecutive cycles of sorption-desorption. Under optimal conditions, a maximum removal efficiency of approximately 98% and 90% was achieved for MB and MO at pH 6.0 using initial MB and MO concentrations of 3.5 mg L-1 and 80 mg L-1, respectively, together with an ultrafiltration membrane with a MWCO of 10 kDa. The presence of interferents in the PEUF process was found to be not significant for dye elimination. Finally, the reusability of both polymers was demonstrated to be effective after four sorption-desorption cycles.

Creating of highly hydrophobic sorbent with fluoroalkyl silane cross-linker for efficient oil-water separation

Hydrophobic sorbents with good hydrophobicity and high porosity have drawn attention for removing oil spills from water. In this study, a highly reusable hybrid polymeric sorbent was successfully fabricated by the reaction of Polydimethylsiloxane (PDMS) and fluorinated alkyl silanes via bulk polymerization without using any activator, initiator, or catalyst. The fabricated polymer sorbent exhibits good hydrophobicity and porous structure; thus, it can be applied as a sorbent for the removal of oils from wastewater. The hybrid sorbents presented high hydrophobicity and excellent sorption capacity for a variety of oils and organic liquids, and the sorption capacity ranges between ~500–1800%. Due to its hydrophobic structure, it can selectively absorb oil from the bottom and the water surface, immediately. Its easy one-pot fabrication procedure, high oil sorption capacity, quick sorption-desorption cycles and great reusability without any capacity loss make it a very promising material for oil spill applications.

Magnetic Carbon Nanotubes‐Silica Binary Composite for Effective Pb(II) Sequestration from Industrial Effluents: Multivariate Process Optimization

AbstractIn this work, magnetic multiwalled carbon nanotubes‐silica binary composite (mCNT@APS) is synthesized via amide bond and utilized for the Pb(II) adsorption from aqueous solutions in batch mode. The composite is characterized using Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), transmission electron microscopy (TEM), X‐ray diffraction (XRD), and point of zero charge (pHpzc) studies. Three levels and three factorial Box–Behnken design in response surface methodology is employed to assess and optimize the effects of influential parameters: pH, initial concentration, and contact time. Using the desirability function, the obtained optimum conditions are pH 5.4, feed concentration 757 µg mL−1 and contact time 4 min. The electrostatic attraction between the active binding sites of adsorbent and Pb(II) at pHpzc &lt; pH results in higher saturation capacity (79.69 mg g−1) in accordance with the best fitted non‐linearized Langmuir isotherm model. The pseudo‐second‐order model fits well to the kinetic data implying chemisorption of Pb(II) onto mCNT@APS. The material can be regenerated up to 15 sorption–desorption cycles using 5 mL of 1.5 M HNO3. The adsorbent exhibits excellent Pb(II) removal efficiency (&gt;98%) from industrial effluents and tap water samples.

Selective to lithium ions nanocomposite sorbents based on TiO2 containing manganese spinel

A method for obtaining nanocomposite sorbents, which are selective towards Li+ ions, has been proposed. The samples were based on adsorptive-active anatase, the selective component being lithium-manganese spinel LiMn2O4. This component was synthesized preliminarily, its nanoparticles were added to the sol of insoluble titanium hydroxocomplexes, and the nanocomposite was precipitated from this suspension and calcined at 5000C. A number of sorbents with different molar ratio of Ti:Mn were prepared via this procedure; they were investigated by means of chemical analysis, X-ray diffraction analysis, optical microscopy, transmission electron microscopy and scanning electron microscopy. The size of nanocrystallites was 20–30 nm. An increase in the spinel amount caused a decrease in the sorbent grain size; however, they the sorbent grains were mechanically durable due to TiO2 which was a binder. Adsorption of Li+ from the solution containing an excess of Na+ ions was studied. The optimal amount of LiMn2O4 (13%) was determined. The sample was obtained in the form of rather large grains (0.3 mm) and the selectivity coefficient Li+/Na+ was about 500. The sorbent was regenerated by a 1 M HNO3 solution without manganese leakage. After 10 cycles of sorption-desorption, the concentrate was obtained. This concentrate can be used for Li2CO3 precipitation.

Enhanced sequestration of tetracycline by Mn(II) encapsulated mesoporous silica nanoparticles: Synergistic sorption and mechanism

A novel Mn(II) encapsulated mesoporous silica nanoparticles (Mn-MSNs) was developed for efficiently removing antibiotic tetracycline from aqueous solutions. The material has a well-ordered, hexagonal mesopore structure with a large specific surface area (720 m2/g) and maximum sorption capacity (229 mg/g) that is about an order of magnitude higher than that of mesoporous silica nanoparticles without Mn-encapsulated, or encapsulated with other transition metal cations Fe3+ and Cu2+. Sorption results showed that the materials can sequestrate tetracycline within a large concentration range (5 μg/L–450 mg/L). Batch sorption experiment, spectroscopic analysis and density functional theory calculation collectively indicated that Mn–O complexation was the dominant mechanism for the tetracycline sorption. Electrostatic attraction and cation-π interaction also contributed to tetracycline sorption with their contribution levels varying with pH in a synergetic way with the Mn–O complexation. The Mn(II) encapsulated MSNs exhibited a good regeneration property over five repeated sorption-desorption cycles, demonstrating its promising potential in the cost-effective applications of sequestrating tetracycline from wastewater, drinking water, and contaminated solutions.

Sorption of U(VI) ions from aqueous solution by eggplant leaves: Isotherm, kinetics and thermodynamics studies

The research aims to utilize eggplant (Solanum melongena) leaves to remove and recover U(IV) ions from aqueous solutions. The biomass was characterized by SEM, FTIR and EDS analyses. Eggplant leaves appeared a maximum U(VI) uptake up to 99.87% with sorption capacity:110.97 mg/g at pH 5, 0.09 g dose, 28 °C and 50 min in the batch sorption system. The nonlinear assessment of isotherm and kinetics showed that the sorption system was fitted well by the Freundlich model and the pseudo first-order kinetic model. Also, the thermodynamic study displayed an exothermic of the uptake process. Likewise, the sorption-desorption cycle showed the good stability of eggplant leaves structure up to 9 cycles. The high adsorption capacity, low cost, good stability and biodegradable properties of eggplant leaves make it a good adsorbent for removing and recovering U(VI) ions from aqueous solutions.

Contrasting microcystin-LR sorption and desorption capability of different farmland soils amended with biochar: Effects of biochar dose and aging time

This study explored biochar (BC) amendment effects on microcystin-LR (MCLR) concentration-dependent sorption and sequential desorption (SDE) by diverse soils to assess MCLR-trapping by BC-amended soils. Soil properties varied with rising BC dose and aging time. As aging proceeded, BC-amended soils shared a generally similar ‘firstly increase and then decrease’ trend of MCLR sorption and ‘firstly decrease and then increase’ trend of desorption at most cases. It appeared that MCLR sorption by BC-amended soils was most positively correlated with mesoporosity and surface basic functionality. BC-amendment increased MCLR-trapping for most soils, especially 4% BC at 3 month-aging maximized trapping ratio of GZ, SY and SX to 86.59%–95.43%, 80.01%–87.20% and 78.73%–90.85%, respectively, at 50–500 μg/L MCLR by largely increasing sorption and decreasing desorption. BC-amendment best matched GZ soil because MCLR-trapping of BC-amended GZ exceeded other amended soils at the same BC dose and aging time, but failed to obviously increase MCLR-trapping of HS soil at most cases, except only case with 2% BC at 3 month-aging. Site energy distribution verified that maximally enhanced MCLR-trapping of most soils was due to greatly enhanced sorption affinity during sorption and 1st desorption cycle, making closer MCLR-binding that more resistant to desorption. Contrarily, BC-amendment did not enhance sorption affinity of HS along sorption-SDE to compromise MCLR-trapping increase at most cases. This study validated 3 months as suitable BC-aging time to maximize MCLR-trapping in diverse soils, and elucidated influencing factors and mechanisms from view of site energy distribution, which shed novel insights on MCLR sorption-desorption by BC-amended soils, and guided to optimize BC-amendment strategy for efficient MCLR-immobilization and eco-risk elimination in diverse soils.

Magnetic dummy molecularly imprinted polymer nanoparticles as sorbent for dispersive solid-phase microextraction of phthalate monoesters in human urine samples

In this work, a simple and efficient dispersive solid-phase microextraction (DSPME) method based on magnetic dummy molecularly imprinted polymer nanoparticles (MMIPs) was developed for the extraction of five phthalate monoesters (mPAEs) from human urine samples. The MMIPs synthesized by sol–gel reaction and surface imprinting were analyzed by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, and thermogravimetric analysis. The obtained results demonstrate that the MMIPs prepared herein are characterized by high selectivity, good adsorption capacity (124.5 mg/g), excellent reusability (over five sorption–desorption cycles), and fast adsorption rates (about 30 min to equilibrium) with respect to five mPAEs. In addition, the MMIPs can be easily separated from the sample solutions due to their good magnetic susceptibility (34.0 emu/g). Using MMIPs as sorbent material in DSPME, five mPAEs in three human urine samples were extracted, and then analyzed by high-performance liquid chromatography (HPLC). Based on the obtained results, this method shows good linearity in the range of 1–100 mg/L for monomethyl phthalate, monoethyl phthalate, and monobutyl phthalate, in the range of 1–80 mg/L for monobenzyl phthalate, and in the range of 1–50 mg/L for monoethylhexyl phthalate. Moreover, good recovery (80.0%–101.0%) of all five mPAEs was observed at three spiked level with relative standard deviations of 0.6–6.6%. Overall, the results reported herein indicate that the prepared MMIPs can be used as sorbent material for the dispersive solid-phase microextraction of phthalate monoesters in human urine samples.

High temperature CO2 sorption using mixed oxides with different Mg/Al molar ratios and synthesis pH

Scheme of post- and pre-combustion processes for CO 2 capture at high temperature using hydrotalcite-derived mixed oxides as CO 2 sorbents. • Several hydrotalcite-derived mixed oxides were prepared to be used as CO 2 sorbents. • Different Mg/Al molar ratios and synthesis pH were used to prepare the materials. • The CO 2 sorption isotherms were determined at 300 °C for screening purposes. • 8.5HT7 showed a high CO 2 sorption capacity: 1.62 mmol/g @ p CO 2 = 1 bar and 300 °C. • The effect of steam over successive CO 2 sorption–desorption cycles was assessed. Several hydrotalcites were prepared by the co-precipitation method with different Mg/Al molar ratios (from 2 to 20) and synthesis pH (8.5 and 10); upon calcination, the hydrotalcite-derived mixed oxides (HDMOs) were obtained, to be used as CO 2 sorbents at high temperature, for instance in post- or pre-combustion CO 2 capture processes. The sorption equilibrium isotherms were determined for screening purposes of all materials prepared using a magnetic suspension microbalance (static experiments) at 300 °C, along with a detailed physicochemical characterization (TG-DTG, ICP-OES, XRD, FTIR, physical sorption–desorption of N 2 at −196 °C and TPD-CO 2 ). In addition, the most promising HDMOs, in terms of CO 2 sorption capacity, were submitted to successive CO 2 sorption–desorption cycles (dynamic experiments) in a packed column at 300 °C, with and without water in the feed, to assess their potential in a sorption–desorption cyclic operation. The results indicate that a synthesis pH of 8.5 provides samples with better CO 2 sorption capacities and that there is an optimum Mg/Al molar ratio (between 4 and 10). The sample with a synthesis pH of 8.5 and a Mg/Al molar ratio of 7 (called 8.5HT7) provided an outstanding CO 2 sorption capacity (1.62 mmol·g −1 at 1 bar of CO 2 and 300 °C) when compared with the other samples herein prepared, but also when compared with commercial (MG63 and MG70) and with other similar materials found in the literature. Finally, an average working capacity of 1.04 mmol·g −1 and 2.11 mmol·g −1 was obtained after repeated sorption–desorption cycles at 0.4 bar of CO 2 and 300 °C for the 8.5HT7 HDMO under dry and wet conditions (45 vol.% H 2 O), respectively.

Effective removal of heavy metals from water using porous lignin-based adsorbents

Multifunctional composite materials are the key to improving removal capacity and environmental utility. Here, the adsorbent (SLCA) was obtained by free-radical polymerization of acrylic acid with sodium lignosulfonate and citric acid. FTIR, SEM, TGA and XPS characterization methods were used to prove the structure and properties of SLCA adsorbents. The maximum uptake capacities of the optimized SLCA adsorbent is 276 mg g−1 of Cu2+ and 323 mg g−1 of Pb2+, respectively. The Langmuir isotherm and the second-order kinetic model were established to illustrate that the capture of Cu2+ and Pb2+ by the adsorbent belongs to chemisorption on the monolayer. XPS analysis confirmed that complexation and electrostatic attraction are the mechanism of pollutant removal. Not only that, as-resulting adsorbent revealed no significant adsorption cycle efficiency reduction even after 5 runs of sorption-desorption cycle, manifesting that it is of great stability and could be regarded as a promising candidate adsorbent. The purpose of this research was to develop a green lignin-based adsorbent with strong environmental protection and regeneration ability based on cheap polyacrylic resin.

Processing technology for carbonate ore from the Argun deposit

Priargun Mining and Chemical Association has been producing uranium in the Streltsov ore field for more than 50 years. The main ore bodies with high content of uranium have been mined out during this period of time, and the uranium content has dropped in ore which is currently extracted. In connection with this, appraisal of the mineral resources and mineral reserves of Priargun MCA has been accomplished. The Argun ore is composed of a few process types—iron silicate and uranium, silicate–uranium–molybdenum, carbonate and uranium, carbonate and molybdenum, carbonate–uranium–molybdenum and rebellious ore (contains zirconium and brannerite). It is required to undertake technology-based rating and certification of the Argun ore. The autoclave leaching technology is found to be higher economically efficient as against the atmospheric leaching technology due to lower operating expenses. From the preliminary studies, four samples of anion-exchange resins are recommended for further testing: A500Y, BM77-14, D299 and Ambersep 920UXL SO4. These ion-exchangers were used to analyze their influence on sorption–desorption of uranium and molybdenum. All these ion exchangers had preserved their sorption capacity in 10 sorption–desorption cycles. Based on the studies into adsorption of uranium and molybdenum from leached slurry at the Argun deposit, the optimal sorbent for extraction and separation of uranium and molybdenum is Ambersep 920UXL SO4. Producibility of natural uranium to meet ASTM C 967-13 standards is analyzed on a laboratory scale. The produced uranium concentrate contains much less impurities than it is stipulated by International Standard Specification ASTM С 967-13. The action chart of processing of carbonate ore from the Argun and Zherlovoe deposits is developed and economically justified.

How efficient is graphene-based nanocomposite to adsorb Hg from seawater. A laboratory assay to assess the toxicological impacts induced by remediated water towards marine bivalves

Advanced investigations on the use of graphene based nanomaterials have highlighted the capacity of these materials for wastewater treatment. Research on this topic revealed the efficiency of the nanocomposite synthetized by graphene oxide functionalized with polyethyleneimine (GO-PEI) to adsorb mercury (Hg) from contaminated seawater. However, information on the environmental risks associated with these approaches are still lacking. The focus of this study was to evaluate the effects of Hg in contaminated seawater and seawater remediated by GO-PEI, using the species Ruditapes philippinarum, maintained at two different warming scenarios: control (17 °C) and increased (22 °C) temperatures. The results obtained showed that organisms exposed to non-contaminated and remediated seawaters at control temperature presented similar biological patterns, with no considerable differences expressed in terms of biochemical and histopathological alterations. Moreover, the present findings revealed increased toxicological effects in clams under remediated seawater at 22 °C in comparison to those subjected to the equivalent treatment at 17 °C. These results confirm the capability of GO-PEI to adsorb Hg from water with no noticeable toxic effects, although temperature could alter the responses of mussels to remediated seawater. These materials seem to be a promise eco-friendly approach to remediate wastewater, with low toxicity evidenced by remediated seawater and high regenerative capacity of this nanomaterial, keeping its high removal performance after successive sorption-desorption cycles.

Impact of drying process on kraft lignin: lignin-water interaction mechanism study by 2D NIR correlation spectroscopy

Kraft lignin, an industrially available by-product from the pulp and paper industry, has revealed enormous potential to be valorised into a wide range of chemicals and biomaterials in the last two decades. However, the understanding of lignin chemistry remains challenging due to its chemical complexity. The goal of this work was to investigate the effect of drying temperature on the chemical, physical, and hygroscopic properties of hardwood kraft lignin isolated from industrial black liquor and elucidate the molecular interactions occurring between water and kraft lignin. Sorption-desorption isotherms determined by dynamic vapour sorption (DVS) technique revealed that the drying process considerably affected the hygroscopicity of the lignin polymer. Moreover, analytical pyrolysis (Py–GC–MS), dynamic NIR spectra collected as a function of relative humidity (0–95%) during sorption-desorption cycles and principal component analysis (PCA), evidenced chemical differences between lignin dried at room (25 °C) temperature and mild oven (55 °C) conditions. The main spectral changes associated with the water sorption in kraft lignin samples were analyzed using difference spectrum technique. 2D NIR spectral correlation analysis provided water sorption mechanism of lignin polymer, disclosing for the first time the sequential order in which water vapour molecules interact with active sorption sites in kraft lignin.

Alkynyl-Based sp 2 Carbon-Conjugated Covalent Organic Frameworks with Enhanced Uranium Extraction from Seawater by Photoinduced Multiple Effects

Biofouling is a major obstacle to the efficient extraction of uranium from seawater due to the numerous marine microorganisms in the ocean. Herein, we report a novel amidoxime (AO) crystalline cova...

Study on the adsorption of strontium on granular manganese oxide

A number of optimal parameters determining the efficiency and rate of the strontium removal by a granular sorbent synthesized by the interaction of KMnO4 and concentrated H2O2 solution have been determined. The optimal drying temperature was found to be 400 °C at an average grain size of 0.1–0.2 mm. The average value of the strontium distribution coefficient in seawater equaled to 1.4–1.5 × 103 mL/g at the V/m ratio of 1000 mL/g ratio. The maximum value of adsorption in a single-component solution calculated using the Langmuir equation was equal to 1.0–1.1 mmol/g and corresponded to total dynamic exchange capacity. As the number of sorption-desorption cycles increased, total dynamic exchange capacity gradually decreased. The efficiency of Sr-90 removal from real liquid radioactive waste streams has been evaluated.