Reduction In Adsorption Capacity Research Articles

Enhanced Cr(VI) removal via CPBr-modified MIL-88A@amine-functionalized GO: synthesis, performance, and mechanism.

Water contamination by heavy metals, especially chromium (VI), poses a critical environmental issue due to its carcinogenic nature and persistence in the environment. Addressing this, the current study develops an efficient adsorbent, CPBr-MIL-88A@AmGO, which utilizes the synergistic capabilities of Cetylpyridinium bromide-modified MIL-88A and amine-functionalized graphene oxide to enhance Cr(VI) removal from aqueous solutions. The obtained results indicate that CPBr-MIL-88A@AmGO achieves its highest removal efficacy at pH 2, where the interaction of CPBr and AmGO's positively charged centers significantly contributes to the adsorption processes. According to the Langmuir isotherm model, the composite's adsorption capacity reached a maximum of 306.75 mg/g. The adsorption kinetics adhered to a pseudo-second-order model along with the endothermic nature of the process. Although the presence of SO42- ions significantly reduces adsorption capacity, other interfering ions including Na+, K+, Ca2+, Cl-, and NO3- only slightly affect it. Remarkably, the composite maintains high removal efficiency, over 82%, even after 7 recycling tests, underscoring its potential for practical applications in water treatment systems. The proposed mechanism involves the contribution of electrostatic attractions, ion exchange, complexation, and the reduction of Cr(VI) to Cr(III) in the removal process. This study not only offers a potent solution for Cr(VI) remediation but also contributes to sustainable water resource management.

Experimental study on pore structure evolution of thermally treated shales: implications for CO2 storage in underground thermally treated shale horizons

Extracting gas from unconventional shale reservoirs with low permeability is challenging. To overcome this, hydraulic fracturing (HF) is employed. Despite enhancing shale gas production, HF has drawbacks like groundwater pollution and induced earthquakes. Such issues highlight the need for ongoing exploration of novel shale gas extraction methods such as in situ heating through combustion or pyrolysis to mitigate operational and environmental concerns. In this study, thermally immature shales of contrasting organic richness from Rajmahal Basin of India were heated to different temperatures (pyrolysis at 350, 500 and 650 °C) to assess the temperature protocols necessary for hydrocarbon liberation and investigate the evolution of pore structural facets with implications for CO2 sequestration in underground thermally treated shale horizons. Our results from low-pressure N2 adsorption reveal reduced adsorption capacity in the shale splits treated at 350 and 500 ºC, which can be attributed to structural reworking of the organic matter within the samples leading to formation of complex pore structures that limits the access of nitrogen at low experimental temperatures. Consequently, for both the studied samples BET SSA decreased by ∼58% and 72% at 350 °C, and ∼67% and 68% at 500 °C, whereas average pore diameter increased by ∼45% and 91% at 350 °C, and ∼100% and 94% at 500 °C compared to their untreated counterparts. CO2 adsorption results, unlike N2, revealed a pronounced rise in micropore properties (surface area and volume) at 500 and 650 ºC (∼30%–35% and ∼41%–63%, respectively for both samples), contradicting the N2 adsorption outcomes. Scanning electron microscope (SEM) images complemented the findings, showing pore structures evolving from microcracks to collapsed pores with increasing thermal treatment. Analysis of the SEM images of both samples revealed a notable increase in average pore width (short axis): by ∼4 and 10 times at 350 °C, ∼5 and 12 times at 500 °C, and ∼10 and 28 times at 650 °C compared to the untreated samples. Rock-Eval analysis demonstrated the liberation of almost all pyrolyzable kerogen components in the shales heated to 650 °C. Additionally, the maximum micropore capacity, identified from CO2 gas adsorption analysis, indicated 650 °C as the ideal temperature for in situ conversion and CO2 sequestration. Nevertheless, project viability hinges on assessing other relevant aspects of shale gas development such as geomechanical stability and supercritical CO2 interactions in addition to thermal treatment.

Rapid removal of polycyclic aromatic hydrocarbons from water using sulfonated mesoporous polymeric adsorbents

Polycyclic aromatic hydrocarbons (PAHs) are potential hazards and are often found in aquatic environments through industrial effluents. Herein, we report sulfonated modified mesoporous thermoplastic polymers to remove potentially carcinogenic PAHs from water rapidly. Mesoporous structures of the thermoplastics (polystyrene, polysulfone, and polycarbonate) were attained using nano-crystallization induced phase separation by flash-freezing route. Sulfonation reactions carried out hydrophilic surface modifications of the polymers. Their ion exchange capacity (IEC) values determined the degree of sulfonation. The sulfonated mesoporous polymers were characterized using Fourier-Transform Infra-Red spectroscopy (FT-IR) for functional groups, Field-Emission Scanning Electron Microscopy (FE-SEM) for mesoporous structures, Brunauer-Emmet-Teller method for specific surface area, and Barrett-Joyner-Halenda method for pore size distributions. The IEC values for the sulfonated mesoporous polymers range from 1.13 – 1.15 × 10-2 meq. g−1. The sulfonated mesoporous polymers showed high specific surface areas (176–185 m2/g) with pore sizes ranging from 5 nm to 9 nm. The sulfonated mesoporous polymers rapidly adsorb PAHs from nearly saturated water solutions within 60 min with % removal of over 98 %. The adsorbents can also be easily regenerated by simple washing with methanol and are found to be recycled up to 10 cycles with only a marginal reduction in adsorption capacities

The simultaneous removal of methylene blue (MB) and Ca2+ by recyclable adsorbents based the scales derived from coal gasification system.

The transformation of solid wastes from industrial production into effective adsorbents could significantly contribute to wastewater treatment. In this study, after acidizing and burning soft scale (SS) from coal gasification system, two magnetic adsorbents (mag-ASS and mag-BASS) were prepared via the combination of magnetite with ultrasonic, respectively. The treatment effects of mag-ASS and mag-BASS were then investigated for simulated wastewater containing macromolecular organic matter [i.e., methylene blue (MB)] and Ca2+. The results indicated that the pseudosecondorder kinetic, Elovich, Freundlich,Langmuir and Temkin model could well describe the adsorption behavior of MB and Ca2+ onto mag-ASS and mag-BASS. The maximum adsorption capacities of mag-ASS for MB and mag-BASS for Ca2+ were 600.53mg/g and 102.54mg/g, respectively. Surprisingly, the adsorption abilities of mag-ASS for MB and mag-BASS for Ca2+ showsignificantly higher than the others. The adsorption mechanisms of MB mainly included electrostatic interaction, π-π conjugate interaction and cation exchange, while those of Ca2+ were mainly electrostatic interaction and cation exchange. The diffusion of MB and Ca2+ onto the magnetic adsorbents might be controlled by the combined effects of intraparticle and liquid film diffusion. There was no significant reduction in adsorption capacity after 8 cycles of adsorptionand desorption, indicating that SS-based magnetic adsorbents had good recyclability and stability. Moreover, the removal efficiency of mag-BASS for total hardness and total organic carbon in real coal gasification gray water (CGGW) was 82.60 and 64.10%, respectively. The treatment of CGGW and theresource of wastes would significantly promote the reasonable disposal of coal gasification scales.

Optimized design of quaternary amino-functionalized chitosan fibers for ultra-high diclofenac adsorption from wastewater

The extraction of non-steroidal anti-inflammatory drugs (NSAIDs) from water bodies is imperative due to the potential harm to humans and the ecosystem caused by NSAID-contaminated water. Quaternary amino-functionalized epichlorohydrin cross-linked chitosan fibers (QECFs), an economical and eco-friendly adsorbent, were successfully prepared using a simple and gentle method for efficient diclofenac (DCF) adsorption. Additionally, the optimized factors for the preparation of QECFs included epichlorohydrin concentration, pH, temperature, and (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHTAC) concentration. QECFs demonstrated excellent adsorption performance for DCF across a broad pH range of 7–12. The calculated maximum adsorption capacity and the amount of adsorbed DCF per adsorption site were determined to be 987.5 ± 20.1 mg/g and 1.2 ± 0.2, respectively, according to the D-R and Hill isotherm models, at pH 7 within 180 min. This performance surpassed that of previously reported adsorbents. The regeneration of QECFs could be achieved using a 0.5 mol/L NaOH solution within 90 min, with QECFs retaining their original fiber form and experiencing only a 9.18% reduction in adsorption capacity after 5 cycles. The Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy were used to study the characterization of QECFs, the preparation mechanism of QECFs, and the adsorption mechanism of DCF by QECFs. Quaternary ammonium groups (R4N+) were well developed in QECFs through the reaction between amino/hydroxyl groups on chitosan and CHTAC, and approximately 0.98 CHTAC molecule with 0.98 R4N+ group were immobilized on each chitosan monomer. Additionally, these R4N+ on QECFs played a crucial role in the removal of DCF.

Competitive adsorption of CO2, N2, and CH4 in coal-derived asphaltenes, a computational study

Greenhouse gases are major contributors to global warming, and their concentration is increasing due to the widespread use of fossil fuels. Coal bed methane (CBM) offers a potential solution to this issue. However, the gas adsorption mechanisms of CBM, particularly in the context of coal-derived asphaltenes, are not fully understood. This study provides a comprehensive theoretical investigation of the competitive adsorption of carbon dioxide (CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}), methane (CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document}), and nitrogen (N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}) in the processes of CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}- and N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}-enhanced coalbed methane recovery, with a focus on coal-derived asphaltenes functionalized with CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document}, NH, O, and S groups. Using the Grand Canonical Monte Carlo (GCMC) simulation method and performing Molecular Dynamics (MD) simulations, we studied the adsorption process. To investigate the electronic effects and nature of the interactions, we performed density functional theory (DFT) calculations. The adsorption energy values and non-covalent interactions (NCI) for the adsorption of gases signify the physical adsorption (van der Waals interaction), with CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} exhibiting the highest (absolute) adsorption energy. The Monte Carlo results indicated that elevated temperatures led to a reduction in adsorption capacity. Coal-derived asphaltenes demonstrated greater selectivity for CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} compared to CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} and N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} in competitive adsorption, especially at elevated temperatures. Our findings highlight the significant potential of our asphaltene model, not only in mitigating CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} greenhouse gas emissions but also in recovering CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document}, which is a valuable resource.

A molecular simulation study on the adsorption and separation performance of carbon nanotubes for SO2 in flue gas

To control the emission of SO2 from flue gas into the atmosphere while considering the capture and collection of greenhouse gas CO2, the adsorption behavior of a binary mixture of SO2 and other gases in flue gas (O2/N2/H2O/CO[Formula: see text] in (10, 10) carbon nanotube (CNT) was simulated using grand canonical Monte Carlo (GCMC) simulation. The adsorption and separation performance of SO2 in CNTs with a diameter range of 0.81–1.63 nm for the five-component mixture gas was also analyzed. The findings suggest that the adsorption and separation of SO2 are primarily influenced by CO2 (reduction of adsorption capacity by about 50%, separation coefficient of SO2/CO2 is lowest) with this effect being more pronounced under high pressure. Meanwhile, it was observed that CNTs with larger pipe diameters exhibit higher SO2 adsorption capacity, but relatively lower SO2/CO2 selectivity and lower stability. On the other hand, CNTs with smaller diameters have relatively lower adsorption capacity for SO2, but exhibit good selectivity and stability (under different pressure) for SO2/CO2. Based on the statistical analysis of SO2 adsorption capacity and SO2/CO2 selectivity, it was determined that (6, 6) CNT with a diameter of 0.81[Formula: see text]nm can exhibit excellent SO2 adsorption and separation performance at atmospheric pressure, while appropriate large diameter CNTs should be selected for flue gas treatment under high pressure.

Development and testing of silica gel with graphite powder composite adsorbent for cooling applications

This research work discusses the development and testing of innovative composite adsorbents made of silica gel (SG), polyvinyl alcohol (PVA) binder and graphite powder (GP). The investigation examines the specific surface area, thermal conductivity, pore volume, adsorption, and desorption rate of the synthesized composite adsorbent. Out of the various formulations, Composite A (composed of 93 % SG, 5 % GP, and 2 % PVA) demonstrates the specific surface area of 530.37 m2/g and pore volume of 0.497 cm3/g. It is noteworthy that Composite A exhibits a 14 % improvement in thermal conductivity and a 3 % increase in desorption rate when compared to its original material, while consistently maintaining the requisite mass transfer characteristics. There is significant improvement in the thermal conductivity of the composite adsorbents with the addition of more than 5 % GP. However, in addition to this enhancement, there is a reduction in adsorption capacity. X-ray diffraction investigation indicates that the composite adsorbents are thermally stable.FESEM investigation reveals that the composite A exhibit no signs of agglomeration. The suggested composite adsorbent show superior thermophysical attributes compared to both pure and silica gel-based composites, making them promising for achieving optimal performance in adsorption cooling systems (ACS), particularly with respect to the specific cooling power (SCP) and coefficient of performance (COP).

Parametric Investigation of CO2 Desorption of Zeolite 13X Under Microwave Condition

In this study, a parametric experimental analysis is performed to investigate the adsorption and desorption processes by evaluating CO2 concentration, sorbent temperature, adsorption, and desorption capacities, and desorption efficiency using Zeolite 13X with a modified multimode microwave oven. Four parameters varied: average microwave powers (336 to 504 W), gas flow rate (60 to 100 ml/min), regeneration temperature (80–120 °C) as well as the presence of moisture with an initial CO2 concentration of 20 %. This work is the first study that investigates these four main parameters’ effects together on the characteristics of CO2 desorption process of Zeolite 13X. While the adsorption was completed faster with higher flow rates with a faster breakthrough curve, the highest CO2 adsorbed amount was found at the lowest flow rates. The moisture effect on the adsorption capacity was also found to be negative with an adsorption capacity reduction of 20 % under wet conditions. The MW power was the key parameter since it controls the process (temperature), and the desorption stage in all conditions were completed faster with higher microwave power rates. However, low MW power always provided better results in terms of CO2 desorbed amount and desorption efficiency. Moreover, while higher flow rate speeded up the desorption process, it reduced the desorption efficiency. Moisture impact was found to be quite significant with a desorption efficiency reduction of 25 %. It was assumed that this reduction is attributed to the competition between the thermal desorption of CO2 and the absorption of CO2 by extra water in the system. Overall, while the amount of desorbed CO2 varied between 1.13 and 1.76 mmol CO2/g, the desorption efficiency changed from 51 % to 75 %.

Modified paddy husk carbon with linked fibrils of FeHO2 using aluminium as the surface regulator for enhanced As (III) removal in fixed bed system

Abstract The As (III) uptake capacity of Fe-impregnated AC greatly depends on the availability of active surface sites of iron oxide. In this context, utilizing aluminium as a surface regulator, we proposed a process to attach linked fibrils of FeHO2 to develop an adsorbent with enhanced As (III) adsorption capacity. The procedure was based on the hydrothermal process using paddy husk-based activated carbon, and both Iron and aluminium ions in the test hydrolysis solution. The exhaust time was observed to rise with increasing dose, falling flow rate, and influent concentration. The CCD optimization result showed that the FeAlPBC was an efficient and cost-effective adsorbent with a maximum response of 1681 min when the independent parameters were retained at 15.0 g FeAlPBC dose, 500 μg/L influent concentrations, 2.0 mL/min flow rate, and a desirability value of 0.986. The experimental results and Thomas and advection-diffusion models were in good agreement. The FeAlPBC samples can be recycled for four cycles with little to no reduction in adsorption capacity. Also, the TCLP test demonstrated that the used FeAlPBC were inert and could be put into landfills without risk. In conclusion, FeAlPBC is a strong contender for removing As (III) from potable water and has a wide range of potential future applications.

Electric-field strengthening uranium extraction from seawater assisted by nanofiltration membranes with sieving-adsorption properties

Electric-field driven uranium extraction from seawater has been proved to greatly enhance the performances of various adsorbents via gathering uranyl ions at the surfaces, but high-concentration interfering cations would also be enriched which generates shielding effects to reduce adsorption capacity. To address this issue, we have fabricated nanofiltration membranes with sieving-adsorption properties by choosing polyamidoxime (PAO) as substrates and polyamide as skin layers. On the one hand, the polyamide skin layers fabricated by interfacial polymerization could effectively separate uranyl ions from other metal ions according to the size-sieving effect since the size of uranyl ions is much larger than most interfering cations. The results demonstrated that the nanofiltration membranes could nearly 100 % reject uranyl ions while the rejections of other metal ions below 30 %. On the other hand, the rejected uranyl ions would be enriched at the surfaces of PAO substrates and followed by adsorption. The increased uranium concentrations are beneficial for both adsorption capacity as well as adsorption rate. Therefore, the adsorption capacity increased by 30 % compared with the pristine PAO adsorbents. This work not only provides a new strategy for the design of high-performance adsorbents, but also could promote the engineering process of uranium extraction from seawater which has an important scientific significance and application value.

Auxiliary depression of copper ion - strengthening the depression of sodium trithiocarbonate on chalcopyrite

Copper ions have been widely used as activators in mineral flotation. However, in this study, it was found that copper ions can be used as auxiliary depressant for chalcopyrite depression, reversing the traditional use of copper ions as activators. In addition, a chalcopyrite depressant called sodium trithiocarbonate (Na2CS3) has been proposed. Na2CS3 was used as the main depressant and copper ions as the auxiliary depressant in this paper. Copper ions could enhance the depression effect of Na2CS3 on chalcopyrite. The depression effect was reflected through micro-flotation tests, and the depression mechanisms were investigated by UV–Vis spectrophotometry determination, contact angle measurements, LEIS experiments, XPS tests, Zeta potential measurements and DFT simulation. The flotation results indicated that Na2CS3 can depress chalcopyrite, and copper ions could enhance the depression effect of Na2CS3 on chalcopyrite. UV–Vis spectrophotometry analysis shows that Na2CS3 can reduce adsorption capacity of BX on chalcopyrite surface. Contact angle measurements and LEIS experiments indicate that hydrophilicity substance is formed after the addition of Na2CS3. XPS tests confirm that the Cu(OH)2 produced by the addition of Na2CS3 was mainly responsible for the depression. Zeta potential measurements and DFT simulation reveal the synergistic mechanism between copper ions and Na2CS3. The enhanced depression effect of copper ion is mainly achieved by promoting the desorption of BX and the formation of Cu(OH)2 on chalcopyrite surface in the presence of Na2CS3.

Linker-Functionalized Phosphinate Metal-Organic Frameworks: Adsorbents for the Removal of Emerging Pollutants.

Metal-organic frameworks (MOFs) are attracting increasing attention as adsorbents of contaminants of emerging concern that are difficult to remove by conventional processes. This paper examines how functional groups covering the pore walls of phosphinate-based MOFs affect the adsorption of specific pharmaceutical pollutants (diclofenac, cephalexin, and sulfamethoxazole) and their hydrolytic stability. New structures, isoreticular to the phosphinate MOF ICR-7, are presented. The phenyl ring facing the pore wall of the presented MOFs is modified with dimethylamino groups (ICR-8) and ethyl carboxylate groups (ICR-14). These functionalized MOFs were obtained from two newly synthesized phosphinate linkers containing the respective functional groups. The presence of additional functional groups resulted in higher affinity toward the tested pollutants compared to ICR-7 or activated carbon. However, this modification also comes with a reduced adsorption capacity. Importantly, the introduction of the functional groups enhanced the hydrolytic stability of the MOFs.

Degradation of Aniline & Para- Chloroaniline from Water by Adsorption Coupled with Electrochemical Regeneration

Treatment methods for water-containing organics are gaining significant attraction in modern-day research. Amines are an important organic compound class encountered in industrial wastewater streams. The current research paper focuses on studying the adsorption behavior of aniline and parachloro-aniline using a graphite-based adsorbent, namely, Nyex-1000, and the subsequent regeneration of the adsorbent. To determine Nyex-1000's adsorption capacity, several parameters, including time, pH, and concentration, were assessed. Adsorption isotherms, kinetics, and used adsorbent regeneration were also investigated. The adsorption of aniline and parachloro-aniline was found to be quite rapid owing to its non-porous nature. Moreover, the low energy requirement makes the process quite economical due to the high electrical conductivity of the adsorbent. The adsorption data was fitted to Langmuir, Freundlich, Redlich Peterson, Sips, and Toth isotherm models. In aniline’s case, Langmuir and Parachloro-aniline Sips models gave the best fitting with the highest R2 value. A regeneration efficiency of 100% was observed in case of both aniline and parachloro-aniline by passing a charge of 5 and 10 coulombs per gram through the adsorbent bed 10 mm in thickness. Adsorption for parachloro-aniline was found to be 0.88 mg/g, and for aniline was found to be 0.40 mg/g. The reduction in adsorption capacity was minimal after several adsorption and regeneration cycles. This study found that spent adsorbent could be regenerated effectively through electrochemical regeneration.

Subcritical CO2 adsorption on geomaterials of coal-bearing strata in the context of geological carbon sequestration

This paper explores the adsorption behaviour of geomaterials in the framework of CO2 sequestration in shallow level coal seams. Manometric adsorption experiments were carried out on two anthracite coal samples, two rock samples from East Irish Sea, MX80-bentonite, Speswhite kaolinite, dry, wet and biofilm-laden (Bascillus mojavensis-laden) sand at subcritical pressure range (up to 6.4 MPa) of isothermal condition at 298.15 K. The experiments were aimed to investigate the influence of the biogeological conditions of coal and caprock constitutions on CO2 adsorption. At lower pressures, the moisture had an influence on the CO2 adsorption on coal resulted in reduced adsorption capacity. At elevated pressures, the volume expulsion behaviour and coal-water interaction had an influence on the adsorption capacities of moist coal sample and resulted in comparable adsorption capacities to dry sample. The disparity in the adsorption capacities between the wet powdered and wet intact core samples showed that the results obtained with powder samples may not reflect the field conditions. Wet conditions and Bascillus mojavensis bacteria influenced the adsorption capacity of sand and showed CO2 chemisorption capacity. The desorption isotherm pattern of wet and biofilm sand showed that the CO2 was continuously adsorbed independent of the gas phase pressure. Among the clay minerals, bentonite had greater affinity towards CO2. Despite the fact that the adsorption capacity of the cap rock is smaller than that of the coal samples, the experimental investigation with constituents of the cap rock provides insights into the effect of biogeological conditions of coal and rock sample constituents on CO2 storage in coal seams.

Zeolite performance in removal of multicomponent heavy metal contamination from wastewater

Efficient removal of heavy metal pollutants from wastewater by ion-exchange sorbents requires knowledge and understanding of the interplay between the adsorption patterns of the different components. The present study elucidates the simultaneous adsorption characteristics of six toxic heavy metal cations (Cd2+, Cr3+, Cu2+, Ni2+, Pb2+, and Zn2+) by two synthetic (13X and 4 A) and one natural (clinoptilolite) zeolite from solutions containing equimolar mixtures of the six metals. Equilibrium adsorption isotherms and equilibration dynamics were obtained by ICP-OES and complemented by EDXRF. An order of magnitude lower adsorption efficiency was exhibited by clinoptilolite (maximum of 0.12 mmol ions/g zeolite), relative to that obtained by the synthetic zeolites 13X and 4 A (a maximum of 2.9 and 1.65 mmol ions/g zeolite respectively). The strongest affinities to both zeolites were demonstrated by Pb2+ and Cr3+ (1.5 and 0.85 mmol/g zeolite respectively for 13X, and 0.8 and 0.4 mmol/g zeolite respectively for 4 A adsorbed from the highest solution concentration). The weakest affinities were observed by Cd2+ (0.1 mmol/g for both zeolites), Ni2+ (0.2 and 0.1 mmol/g for 13X and 4 A respectively), and Zn2+ (0.1 mmol/g for both zeolites). Large differences were observed between the two synthetic zeolites in terms of their equilibration dynamics and adsorption isotherms. Pronounced maxima were displayed in the adsorption isotherms for zeolites 13X and 4 A. The decline in adsorption of the weaker adsorbing ions with the increase in total solution concentration was attributed to the thermodynamic equilibrium between the ions adsorbed on the zeolite surface and those in the solution. Regeneration by 3 M KCL eluting solution resulted in considerable reduction in adsorption capacities following each desorption cycle.

Phosphorylated calix[4]arene/balsa wood copolymers for selective uranyl extraction from wastewater and seawater

Hyper-crosslinked polymers are frequently used to recover specific guest molecules due to their high porosities, excellent chemical properties, and structural stability. However, the recovery of powder adsorbents poses a significant challenge in the extraction of uranyl from aqueous solutions, which limits their practical application. A phosphorylated calix[4]arene/balsa wood copolymer (C4-W-P) was successfully synthesized and utilized for the extraction of uranyl from radioactive wastewater and seawater. Compared to previously reported adsorbents, C4-W-P demonstrated rapid uranyl capture kinetics, with adsorption equilibrium achieved within 150 min. The material exhibited a monolayer saturation adsorption capacity of 473.9 mg·g−1 at pH 5. Thermodynamic studies confirmed the spontaneous and endothermic nature of the adsorption process. Furthermore, C4-W-P exhibited exceptional structural stability, with only a 9.7 % reduction in adsorption capacity after six adsorption–desorption cycles. Additionally, C4-W-P demonstrated excellent selectivity in simulated wastewater containing 16 rare metal ions and simulated seawater containing an additional five metal ions. The KdU values were recorded to be 1817.2 and 33,265.3 mL·g−1, respectively, for these conditions. These results demonstrate the high-efficiency uranium removal capabilities of C4-W-P under realistic conditions. The abundant phosphate groups (∼1.69 mmol·g−1) on the material surface were identified as the primary adsorption contributors. Overall, this study provides a promising strategy for uranyl extraction with high selectivity and ease of preparation, contributing to environmental protection and economic development.

Synthesis of core–shell magnetic nanocomposite bearing phosphonic acid ligand for uranium extraction from strong HNO3 solution

Recovery of uranium from strong acid media using magnetic nanomaterials as sorbents is vital for sustainable nuclear energy, due to their superparamagnetism and large specific surface energy. However, it remains a huge challenge to develop magnetic nanomaterials for extracting uranium from strong acid media, since magnetic nanomaterials often suffer from poor structural stability and low uranium adsorption performance in strong acid media. Herein, a novel core–shell magnetic nanocomposite Fe3O4@SiO2/P (MBA-VPA) bearing phosphonic acid was fabricated by distillation-precipitation polymerization of N, N'-methylene diacrylamide (MBA) with vinylphosphonic acid (VPA) around the surface of Fe3O4 decorated by SiO2 (Fe3O4@SiO2). By optimizing the polymerization system, high concentration of phosphonic acid with high free movement degree was led into the surface of the sorbent. Under applied conditions (c(H+) = 4 mol L−1, T = 298 K and t = 3 h), the sorbent showed a record-breaking maximum adsorption capacity (qmax) of 262.5 mg g−1 with an excellent selectivity for uranium in the presence of multi-ions. The adsorption capacity of the sorbent in strong HNO3 increased remarkably with increase of the concentration and free movement degree of phosphonic acid. By coating Fe3O4 with an inert SiO2, the sorbent exhibited excellent acidic resistance in strong HNO3. The sorbent could also be magnetically recovered within 15 s, and repeated at least six times without obvious reduction in adsorption capacity. The excellent adsorption performance in strong HNO3 media was primarily assigned to the abundant accessible PO groups, evidenced by X-ray photoelectron spectroscopy (XPS), control experiments and density functional theory (DFT). Most importantly, this work provides a new perspective for developing highly active, excellent acidic resistance, and recyclable magnetic nanomaterials for extracting uranium from strong acid media.

Mixed Diethanolamine and Polyethyleneimine with Enhanced CO2 Capture Capacity from Air.

Supported polyethyleneimine (PEI) adsorbent is one of the most promising commercial direct air capture (DAC) adsorbents with a long research history since 2002. Although great efforts have been input, there are still limited improvements for this material in its CO2 capacity and adsorption kinetics under ultradilute conditions. Supported PEI also suffers significantly reduced adsorption capacities when working at sub-ambient temperatures. This study reportsthat mixing diethanolamine (DEA) into supported PEI can increase 46% and 176% of pseudoequilibrium CO2 capacities at DAC conditions compared to the supported PEI and DEA, respectively. The mixed DEA/PEI functionalized adsorbents maintain the adsorption capacity at sub-ambient temperatures of -5 to 25°C. In comparison, a 55% reduction of CO2 capacity is observed for supported PEI when the operating temperature decreases from 25 to -5°C. In addition, the supported mixed DEA/PEI with a ratio of 1:1 also shows fast desorption kinetics at temperatures as low as 70°C, resulting in maintaining high thermal and chemical stability over 50 DAC cycles with a high average CO2 working capacity of 1.29mmol g-1 . These findings suggest that the concept of "mixed amine", widely studied in the solvent system, is also practical to supported amine for DAC applications.

Preparation of magnetic poly(ethylene glycol dimethacrylate-N-Methacryloyl-(L)-glutamic acid) particles for thrombin purification

In this study, magnetic poly(ethylene glycol dimethacrylate-N-methacryloyl-(L)-glutamic acid) (mPEGDMA-MAGA) particles were prepared by the dispersion polymerization in order to purify thrombin effectively. mPEGDMA-MAGA particles were synthesized by adding different ratios of magnetite (Fe3O4) to the medium in addition to the monomer phases EGDMA and MAGA. The characterization studies of mPEGDMA-MAGA particles were used by fourier transform infrared spectroscopy, zeta size measurement, scanning electron microscopy and electron spin resonance. mPEGDMA-MAGA particles were used in thrombin adsorption studies from aqueous thrombin solutions in both batch and magnetically stabilized fluidized bed (MSFB) system. Maximum adsorption capacity in pH 7.4 phosphate buffer solution is 964 IU/g polymer and 134 IU/g polymer in MSFB system and batch system, respectively. The developed magnetic affinity particles enabled the separation of thrombin from different patient serum samples in one step. It has also been observed that magnetic particles can be used repeatedly without significant reduction in adsorption capacity.