High Adsorption Performance Research Articles

High performance adsorption efficiency of metal oxides towards potassium dichromate

The potassium dichromate (K2Cr2O7) is mostly used as an oxidizing agent in a variety of industrial and laboratory. It poses both immediate and long-term health risks, just like any other compound containing hexavalent chromium. Therefore, its adsorption process on the surface of a different metal oxides of PbO and MgO nanoparticles is thoroughly investigated in this work. Both structural and optical properties have been investigated for these metal oxides using XRD, HRTEM and UV vis spectroscopy. The XRD diffraction peaks confirmed the phases of both PbO and MgO NPs. Moreover, the crystallinity of PbO and MgO is 93,63 % and 95.25 %, respectively. The present metal oxides showed irregular shape such as spherical like shape and Quasi-spherical or rod- like shapes for PbO and MgO NPs. According to the results of the adsorption studies, The PbO NPs shows a high adsorption efficiency of 70 % towards potassium dichromate. The present results illustrated that both metal oxides may be used as an adsorbent to break down Potassium dichromate.

Enhanced reduction of Cd uptake by wheat plants using iron and manganese oxides combined with citrate in Cd-contaminated weakly alkaline arable soils

Iron (Fe) and manganese (Mn) oxides can be used to remediate Cd-polluted soils due to their excellent performance in heavy metal adsorption. However, their remediation capability is rather limited, and a higher content of available Mn and Fe in soils can reduce Cd accumulation in wheat plants due to the competitive absorption effect. In this study, goethite and cryptomelane were first respectively used to immobilize Cd in Cd-polluted weakly alkaline soils, and sodium citrate was then added to increase the content of available Mn and Fe content for further reduction of wheat Cd absorption. In the first season, the content of soil-available Cd and Cd in wheat plants significantly decreased when cryptomelane, goethite and their mixture were used as the remediation agents. Cryptomelane showed a better remediation effect, which could be attributed to its higher adsorption performance. The grain Cd content could be decreased from 0.35 mg kg−1 to 0.25 mg kg−1 when the content of cryptomelane was controlled at 0.5%. In the second season, when sodium citrate at 20 mmol kg−1 was further added to the soils with 0.5% cryptomelane treatment in the first season, the content of soil available Cd was increased by 14.8%, and the available Mn content was increased by 19.5%, leading to a lower Cd content in wheat grains (0.16 mg kg−1) probably due to the competitive absorption. This work provides a new strategy for the remediation of slightly Cd-polluted arable soils with safe and high-quality production of wheat.

Kaolin-Derived Porous Silico-Aluminate Nanoparticles as Absorbents for Emergency Disposal of Toluene Leakage.

To rapidly eliminate toluene from aqueous environments during leakage accidents, this paper synthesized porous silico-aluminate nanoparticles (SANs) via a hydrothermal method, using cost-effective and non-toxic natural kaolin as the basic raw material. The morphology and structure of the porous SANs were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and BET-specific surface area tests. The effects of different conditions, such as the dosage of porous SANs, initial concentration of toluene, temperature, capture time, and pH, on the adsorption performance of porous SANs were analyzed. The as-prepared SANs exhibited a high removal efficiency and rapid adsorption performance toward toluene in aqueous solution. Finally, the kinetics of the adsorption of toluene in aqueous solution by porous SANs were investigated. The mechanism of the adsorption of toluene by porous SANs was further discussed. These findings provide a cost-effective and highly efficient absorbent for the emergency disposal of toluene leakage accidents.

Tailoring of ionic imprinted polymer-based polyeugenol as a selective adsorbent of Fe(III) ions

ABSTRACT An imprinted polymer has been successfully synthesized using polyeugenol and polyethylene glycol dimethacrylate (PEGDMA) crosslinker for selective adsorption of Fe3+ ions. The synthesized imprinted polymer is milled to obtain a polymer with high adsorption performance. This work aims to determine the effect of milling on ionic imprinted polymer (IIP) and non-ionic imprinted polymer (NIP) as selective adsorbents of Fe3+ ion against competing metal ions. Adsorbent synthesis was carried out by adding polyeugenol with the crosslinking agent ethylene glycol dimethacrylate (EGDMA) in chloroform solvent and with the initiator 2,2’-Azobis(2-methyl propionitrile) (AIBN). IIP and NIP were used as adsorbents in the adsorption selectivity test of Fe3+ on the binary metals Fe3+/Cu2+, Fe3+/Zn2+, Fe3+/Ag+, and Fe3+/Cd2+. SEM (Scanning Electron Microscope) shows a more identical and smaller particle surface morphology in the milled IIP. Surface area analysis using the BET method (Brunauer-Emmett-Teller) showed an increase in the surface area of IIP after milling treatment. The adsorption capacity and selectivity of Fe3+ metal ions on milled IIP were greater than that of IIP. The selectivity of Fe3+ adsorption is greater in the binary metal ion mixture Fe3+/Cu2+ and Fe3+/Zn2+ than in the Fe3+/Cd2+ and Fe3+/Ag+ solutions.

High-efficient depletion and separation of histidine-rich proteins via Cu2+-chelated porous polymer microspheres

Depletion and separation of histidine-rich proteins from complicated biosamples are crucial for various downstream applications in proteome research and clinical diagnosis. Herein, porous polymer microspheres coated with polyacrylic acid (SPSDVB-PAA) were fabricated through double emulsion interfacial polymerization technique and followed by immobilization of Cu2+ ions on the surface of SPSDVB-PAA. The as-prepared SPSDVB-PAA-Cu with uniform size and nanoscale pore structure enabled coordination interaction of Cu2+ with histidine residues in his-rich proteins, resulting in high-performance adsorption. As metal affinity adsorbent, the SPSDVB-PAA-Cu exhibited favorable selectivity for adsorbing hemoglobin (Hb) and human serum albumin (HSA) with the maximum adsorption capacities of 152.2 and 100.7 mg g−1. Furthermore, the polymer microspheres were used to isolate histidine-rich proteins from human whole blood and plasma, underscoring their effectiveness. The liquid chromatography tandem mass spectrometry (LC-MS/MS) results indicated that the content of 14 most abundant proteins in human plasma was depleted from 81.6 % to 30.7 % and low-abundance proteins were enriched from 18.4 % to 69.3 % after treatment with SPSDVB-PAA-Cu, illustrating potential application of SPSDVB-PAA-Cu in proteomic research.

Experimental Study on the Preparation of Lignin-Based Activated Carbon and the Adsorption Performance for Phenol.

Biomass waste and wastewater are important wastes in the process of industrialization, which need to be effectively treated and utilized. In this work, an innovative method of collaborative treatment of biomass waste and phenol-containing wastewater is proposed. Biomass waste was used to produce activated carbon (AC), and then AC was used for phenol removal in wastewater treatment. Two kinds of typical biomass waste material, namely, coconut shell and lignin, were used. Physical activation (steam activation) and chemical activation methods were compared. Results show that steam activation is an effective method for coconut shell AC production. The largest Brunauer-Emmett-Teller (BET) surface area was 1065 m2/g at 800 °C. Chemical activation could produce AC samples with higher BET specific surface area. The lignin AC with K2CO3 activation has the largest BET surface of 1723.8 m2/g at 800 °C. FTIR results indicated that K2CO3 activation could greatly enhance the formation of surface oxygen-containing functional groups. Both coconut shell AC and lignin AC samples show excellent performance for phenol removal. The highest phenol removal efficiency for coconut shell AC and lignin AC are 96.87% and 98.22%, respectively. Adsorption kinetic analysis show that the pseudo-first-order kinetic model is able to describe the adsorption characteristics of phenol in wastewater treatment. Recycling properties show that regeneration of lignin AC could maintain high adsorption performance for phenol.

Construction of attapulgite decorated cetylpyridinium bromide/cellulose acetate composite beads for removal of Cr (VI) ions with emphasis on mechanistic insights

Eco-friendly and renewable composite beads were constructed for efficient adsorptive removal of Cr (VI) ions. Attapulgite (ATP) clay decorated with cetylpyridinium bromide (CPBr) was impregnated into cellulose acetate (CA) beads, which were formulated through a simple and cost-effective solvent-exchange approach. FTIR, XRD, SEM, Zeta potential, and XPS characterization tools verified the successful formation of ATP–CPBr@CA beads. The composite beads displayed a spherical and porous shape with a positively charged surface (26.6 mV) at pH 2. In addition, higher adsorption performance was accomplished by ATP–CPBr@CA composite beads with ease of separation compared to their components. Meanwhile, equilibrium isotherms pointed out that the Langmuir model was optimal for describing the adsorption process of Cr (VI) with a maximal adsorption capacity of 302 mg/g. Moreover, the D–R isotherm model verified the physical adsorption process, while adsorption data obeyed the pseudo-second-order kinetic model. Further, XPS results hypothesized that the removal mechanism involves adsorption via electrostatic interactions, redox reaction, and co-precipitation. Interestingly, the ATP–CPBr@CA composite beads reserved tolerable adsorption characteristics with a maximum removal present exceeding 70% after reuse for seven successive cycles, proposing its feasible applicability as a reusable and easy-separable candidate for removing heavy metals from aquatic bodies.

Graphene oxide intercalated Alk-MXene adsorbents for efficient removal of Malachite green and Congo red from aqueous solutions

Currently, adsorbents with high adsorption performance for eliminating pollutants from discharged wastewater have received many researchers’ attention. To this aim, a novel AMXGO absorbent was fabricated by intercalating graphene oxide (GO) into alkalized MXene (Alk-MXene) layer which exhibited high efficacy for the removal of cationic Malachite Green (MG) and anionic Congo Red (CR). Analysis of FTIR, XRD, SEM and TG presented that AMXGO absorbent have a typical three-dimensional layer by layer structure and abundant oxygen-containing groups and its thermal stability was remarkably improved. BET results elucidated that AMXGO1 adsorbent has larger specific surface area and pore volume (16.686 m2 g−1, 0.04733 cm3 g−1) as compared to Alk-MXene (4.729 m2 g−1, 0.02522 cm3 g−1). A dependence of adsorption performance on mass ratio between Alk-MXene and GO, initial dye concentration, contact time, temperature and pH was revealed. Maximum adsorption capacity of MG (1111.6 mg/g) and CR (1133.7 mg/g) were particularly found for AMXGO1 absorbent with a mass ratio of 3:1 and its removal for both dyes were higher than 92%. The adsorption process of AMXGO1 adsorbent for both MG and CR complies with pseudo-second-order kinetic model and Freundlich isotherm model. In addition, adsorption mechanism was explored that synergism effects as electrostatic attraction, π-π conjugates, intercalation adsorption and pore filling were the main driving force for the high adsorption performance of dye. Therefore, AMXGO adsorbent has a potential application prospect in the purification of dye wastewater.

Effect of pretreatment and activation conditions on pore development of coal-based activated carbon

Abundant pore volume and appropriate pore configuration are two crucial characteristics of high-performance carbonaceous adsorbents and catalysts. In this study, influences of pre-treatments (e.g., breaking, sieving and ash removal by acid) and activation conditions (e.g., activation time) on pore parameters (including BET surface area, pore diameter and pore hierarchy degree) of resultant activated carbon were systematically investigated. In addition, the difference between conventional carbonization-activation (i.e., the two-step preparation method) and one-step activation in pore development of activated carbons was revealed. The sample prepared by a 120-minute one-step activation exhibited a BET surface area high to 1038.1 m2/g and a pore hierarchy at 50.7 %. Based on the kinetics analysis using TGA reactor, reaction between the activator (i.e., CO2) and carbon matrix was found enhanced in one-step activation, contributing to the generation of mesopores. Remarkably, a new indicator, Effective Activation Rate (EAR) was proposed to accurately describe the activation rate in one-step synthesis after decoupling the release of moisture and volatile compounds. The above conclusions provide guidance for flexibly regulating the pore configurations of activated carbons derived from natural precursors.

Performance and mechanism of lanthanum-modified MnO2 for defluoridation from water: The role of MnO2 crystal forms

MnO2 has a large potential for defluoridation, however, the influences of its crystal forms on the performance and mechanism of defluoridation are unknown. The research systematically investigated the defluoridation performance and mechanism of a total of eight materials with different crystal forms of MnO2 (α, β, γ, δ) before and after lanthanum modification, separately. It was indicated that the largest Langmuir adsorption of α-MnO2 and La-γ-MnO2 for fluoride achieved 5.04 mg/g and 42.39 mg/g, correspondingly. The surface hydroxyl group and lanthanum loading of the material proved to be the major contributors to defluoridation. For the adsorption performance of eight materials on fluoride, pH was a significant influencing factor, with the highest adsorption performance at pH 5 ∼ 6. The eight materials showed consistent selectivity for fluoride adsorption in the existence of different anions, with the order of influence on the removal efficiency: CO32–> NO3–> SO42–> Cl–. The studies of FTIR, XPS, and variation of solution pH further illustrated that the adsorption mechanism of the eight materials on fluoride was the ion-exchange interaction and the complexation reaction. In addition, the effect of crystal forms on the adsorption of fluoride ions was further elaborated by DFT analysis. Finally, this study provided an in-depth discussion of the parameters of the dynamic process as well as the nature of the penetration curves by applying the Thomas, Clark, and BDST models.

Self-foaming calcium modified carbon foam derived from a liquefied product resin of tobacco stalks for the removal of Pb2+ in water

This study demonstrated a self-foaming plus in-situ modification strategy that led to an efficient and environmentally friendly carbon foam adsorbent for removal of Pb2+ from aqueous solution. Specifically, the resin derived from liquefied tobacco stalk (TSLPR resin) was used as the precursor of carbon foams. Various characterization techniques were employed to investigate the morphology, structure, surface area, pore size, and adsorption capacity of the materials. Upon carbonization of the resin foam at 800 ℃, considerable CaO and CaCO3 converted from Ca (NO3)2 were distributed on the surface of the cell wall, indicating the success of the in-situ modification. By using a carbon foam loaded with 7% calcium (Ca@CF-7) as an adsorbent for removal of Pb2+ at a pH of 4 and 25 ℃, the dynamic adsorption equilibrium was achieved within 480 minutes. The theoretical maximum adsorption capacity (qm) obtained by Sips model reached 348.8 mg·g−1, which is more than 4.5 times higher than the pristine carbon foam. The findings of this study indicated that the chemical co-precipitation of Pb3(CO3)2(OH)2 played a significant role for removal of Pb2+, which could be attributed to the surface alkaline environment provide by CaO and CaCO3. This study offers a novel approach for in-situ modification of carbon foam and also demonstrated the potential of the straw biomass with low lignin content in production of high-performance carbon adsorbents.

Fabrication of porous materials using quinoa husk and attapulgite co-stabilized foam templates for dye adsorption and post-treatment of soil remediation

Water-based foam has great potential in the preparation of porous materials, but there is still a lack of green and simple preparation methods. In this study, a stable water-based foam that co-stabilized with saponin leached from agricultural waste quinoa husk (QH) and nano-clay attapulgite (APT). The thickening effect and interface stability of modified APT played a crucial role in the formation and stabilization of Pickering foam. The free radical polymerization occurred in the continuous phase without affecting the foam stability, and the obtained pore-rich adsorbent displayed high-performance adsorption for methylene blue (MB) and methyl violet (MV), with the adsorption capacities reaching up to 291.95 mg/g and 430.01 mg/g, respectively. In keeping with the idea of sustainable development, the spent adsorbent was pyrolyzed and converted into mineral biochar. The pot experiments showed that the mineral biochar could improve the soil properties and promoted the plant growth. This work provided a new approach to the production of green and stable Pickering foam and also an alternative to realize the sustainable high value utilization of waste QH.

Tannic acid-assisted construction of amino-functionalized cellulose nanofiber composite aerogel for high-performance adsorption of Cr(VI), Cu(II) and Congo red: Experimental and DFT studies

With industrialization, heavy metals and dyes pose potential environmental and human health risks. Developing adsorbent materials with three-dimensional structures and abundant active sites is essential for removing these pollutants. In this study, we developed an environmentally friendly, high-adsorption composite aerogel (CNF-TA-PMMT-PEI) comprising cellulose nanofiber (CNF), polydopamine-modified montmorillonite (PMMT), tannic acid (TA), and polyethyleneimine (PEI). The introduction of TA and PEI increased the number of adsorbed active sites and the interaction between CNF and PMMT through strong hydrogen and chemical bonding. CNF-TA-PMMT-PEI has a honeycomb-like pore structure, high porosity (98.29 %), abundant functional groups, and showed rapid and excellent adsorption performance for Cr(VI), Cu(II), and Congo red (CR), with the Qm of 456.62, 289.86, and 3429.23 mg/g, respectively. The adsorption process followed the pseudo-second-order kinetic model and Langmuir model, indicating that the chemisorption of the monomolecular layer controlled the adsorption, and the thermodynamic adsorption indicated a spontaneous heat absorption reaction. The aerogel had good anti-interference properties and excellent adsorption performance in natural water. After 7 cycles, the removal of Cr(VI), Cu(II) and CR was maintained at 74.81 %, 68.23 % and 81.54 % of the initial performance, respectively. FTIR, XPS and DFT calculations revealed the amine group of the PEI and the phenolic hydroxyl group on TA are the main adsorption sites. The CR had the lowest adsorption energy (−4.23 Ha) compared to Cu(II) and Cr(VI), suggesting stronger interactions and greater stability on CNF-TA-PMMT-PEI. The adsorption mechanism for Cr(VI) involved electrostatic interactions, reduction, and chelation. For Cu(II), including chelation. For CR, adsorption through electrostatic attraction, π-π interactions, and Schiff base formation. In summary, CNF-TA-PMMT-PEI is an eco-friendly adsorbent with outstanding adsorption capacity and effective recovery performance for simulated wastewater.

One‐Step Synthesis of Thiol‐Functional Mesoporous Silica Nanospheres and Selective Removal of Cationic Dyes

AbstractThe surface characteristics of nanoparticles have a huge impact on adsorption effects. In this paper, thiol‐functional mesoporous silica nanospheres (MSNs−SH) are successfully prepared through simple one‐step hydrolysis and co‐condensation of tetraethyl orthosilicate and (3‐mercaptopropyl) triethoxysilane with hexadecyltrimethylammonium bromide and sulfobetaine 12 as dual‐template. The obtained MSNs−SH have high surface area (1260 m2 g−1), accessible mesopores (2.2 nm), great pore volume (1.7 cm3 g−1), and uniform adjustable diameter (90 nm). Furthermore, the diameter and pore‐size of MSNs−SH can be controlled via adjusting the ethanol content in the synthesis system. MSNs−SH exhibit a fast adsorption kinetics, marked adsorption capacity of cationic rhodamine B (RB 534.2 mg g−1), and remarkable selective adsorption for cationic dyes. Theoretical analysis reveals the adsorption behavior of RB on MSNs−SH follows the Langmuir isotherm models and pseudo‐second‐order kinetic. Additionally, the thermodynamic results indicate that the adsorption process is a spontaneous process driven by temperature. The results demonstrate that MSNs−SH are greatly potential for effectively removing cationic dyes from wastewater, with the advantages of simple preparation, high adsorption performance and perfect selectivity.

Solution-processable polymers of intrinsic microporosity for selective silver removal from aqueous solution and subsequent disinfection by silver-laden coatings

Silver ions (Ag+) in waterways pose a growing threat to the environment and living organisms. Achieving an effective and green process for Ag+ removal requires an adsorbent with excellent specificity for silver ions and easy recoverability after fouling or blocking. However, this remains a major challenge. To address this concern, we developed a high-performance adsorbent by grafting polymers of intrinsic microporosity (PIM) with thioamide groups. This thioamide-modified PIM (TPIM-1) adsorbent exhibited an exceptional adsorption capacity of 656 mg g−1 and high selectivity (distribution coefficient of 833.3 mL g−1, selectivity coefficient of 346 over Cd2+) for aqueous Ag+ removal. TPIM-1 also features good solubility in selected solvents, allowing regeneration through a dissolution separation precipitation (DSP) procedure once fouling or blocking occurs. Over 80 % of the adsorption capacity was recovered after nine continuous regeneration cycles, showcasing potential cost-effective reusability. Density Functional Theory (DFT) results reveal that the grafted thioamide groups play a critical role in selective Ag+ adsorption, with a binding energy of 54 kcal mol−1. In addition, the Ag+-loaded PIM-coated glass surface showed excellent antibacterial ability, inhibiting the growth of Bacillus subtilis and E. coli. This study provides a viable strategy for the development of a low-carbon footprint silver removing adsorbent from wastewater.

Highly adsorptive removal of heavy metal, dye, and antibiotic pollutants using functionalized graphene nanosheets sono-electrochemically derived from graphitic waste

The development of highly adsorptive materials at low cost is critically important for efficient treatment of industrial wastewater. We herein report a one-step sonoelectrochemical strategy to synthesize functionalized graphene (FG) nanosheets as an effective adsorptive material using graphite waste from spent household batteries. Scanning/transmission electron and Raman microscopy studies reveal that the as-synthesized nanosheets are composed of few (2–6) graphene layers. Additionally, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses imply the presence of oxygen functional groups on the nanosheets (CO and -COOH, oxygen content of 4.29%), which are immensely beneficial for the electrostatic adsorption with heavy metals, dyes, and antibiotics in aqueous solutions. As expected, FG nanosheets exhibit potent capabilities of handling a wide range of pollutants, such as methylene blue, methyl orange, enrofloxacin, and Pb2+, with high adsorption performances (99.95% and 21.21 mg/g for Enrofloxacin, 98.93% and 119.3 mg/g for methylene blue, 95.82% and 25.67 mg/g for methyl orange, 95.56% and 86.10 mg/g for Pb2+). These findings therefore show a great promise for practical uses of the FG material as efficient adsorbents in eliminating metallic, organic, and antibiotic pollutants in water.

Molecular Simulation Studies of Pharmaceutical Pollutant Removal (Rosuvastatin and Simvastatin) Using Novel Modified-MOF Nanostructures (UIO-66, UIO-66/Chitosan, and UIO-66/Oxidized Chitosan).

The ubiquitous presence of pharmaceutical pollutants in the environment significantly threatens human health and aquatic ecosystems. Conventional wastewater treatment processes often fall short of effectively removing these emerging contaminants. Therefore, the development of high-performance adsorbents is crucial for environmental remediation. This research utilizes molecular simulation to explore the potential of novel modified metal-organic frameworks (MOFs) in pharmaceutical pollutant removal, paving the way for the design of efficient wastewater treatment strategies. Utilizing UIO-66, a robust MOF, as the base material, we developed UIO-66 functionalized with chitosan (CHI) and oxidized chitosan (OCHI). These modified MOFs' physical and chemical properties were first investigated through various characterization techniques. Subsequently, molecular dynamics simulation (MDS) and Monte Carlo simulation (MCS) were employed to elucidate the adsorption mechanisms of rosuvastatin (ROSU) and simvastatin (SIMV), two prevalent pharmaceutical pollutants, onto these nanostructures. MCS calculations demonstrated a significant enhancement in the adsorption energy by incorporating CHI and OCHI into UIO-66. This increased ROSU from -14,522 to -16,459 kcal/mol and SIMV from -17,652 to -21,207 kcal/mol. Moreover, MDS reveals ROSU rejection rates in neat UIO-66 to be at 40%, rising to 60 and 70% with CHI and OCHI. Accumulation rates increase from 4 Å in UIO-66 to 6 and 9 Å in UIO-CHI and UIO-OCHI. Concentration analysis shows SIMV rejection surges from 50 to 90%, with accumulation rates increasing from 6 to 11 Å with CHI and OCHI in UIO-66. Functionalizing UIO-66 with CHI and OCHI significantly enhanced the adsorption capacity and selectivity for ROSU and SIMV. Abundant hydroxyl and amino groups facilitated strong interactions, improving performance over that of unmodified UIO-66. Surface functionalization plays a vital role in customizing the MOFs for pharmaceutical pollutant removal. These insights guide next-gen adsorbent development, offering high efficiency and selectivity for wastewater treatment.

Semi-wet synthesis of high-performance Li1.6Mn1.6O4 for selective lithium extraction from Salt Lakes Brine

Among the manganese-based lithium-ion sieves, Li1.6Mn1.6O4 has a high theoretical lithium adsorption capacity as a spinel ion sieve material. Small particle size orthogonal phase purity LiMnO2 powders were prepared by a semi-wet method and calcined in air at 400 °C to obtain Li1.6Mn1.6O4 a lithium-ion sieve precursor. The synergistic effects of oxygen atmosphere, heat treatment conditions and lithium/manganese molar ratio on the crystal structure of LiMnO2 and the lithium adsorption/desorption characteristics of Li1.6Mn1.6O4 were comprehensively investigated with XRD, SEM, TEM, XPS, Raman, DTA-TG and capacity retention study. Notably, when the initial lithium/manganese molar ratio was set at 1.1, and the sample underwent a calcination at 120 °C for 48 h under carefully controlled deoxygenation conditions, we observed the exclusive presence of the desired orthorhombic phase in the LiMnO2 sample. In contrast, when the synthesis conditions deviated from the optimized parameters led to the presence of the monoclinic phase of Li2MnO3. This highlights the sensitivity of Li1.6Mn1.6O4 properties to the synthesis conditions. The results of adsorption-desorption cycles show that the ion sieve Li1.6Mn1.6O4 prepared by heat treatment of ordered o-LiMnO2 is more stable, the structural stability of Li1.6Mn1.6O4 were characterized by high-temperature in-situ XRD experiments during heating from 30 to 800 °C. The equilibrium adsorption capacity was 34 mg g−1 in Qarhan Salt Lake brine at 10th cycle, and a remarkably low Mn dissolution loss rate of 0.6 %. The results have significant potential to advance the development of high-performance adsorbent in the Li-Mn-O system and contribute to the advances in lithium separation technology.

Efficient recovery and recycling/upcycling of precious metals using hydrazide-functionalized star-shaped polymers

There is a growing demand for adsorption technologies for recovering and recycling precious metals (PMs) in various industries. Unfortunately, amine-functionalized polymers widely used as metal adsorbents are ineffective at recovering PMs owing to their unsatisfactory PM adsorption performance. Herein, a star-shaped, hydrazide-functionalized polymer (S-PAcH) is proposed as a readily recoverable standalone adsorbent with high PM adsorption performance. The compact chain structure of S-PAcH containing numerous hydrazide groups with strong reducibility promotes PM adsorption by enhancing PM reduction while forming large, collectable precipitates. Compared with previously reported PM adsorbents, commercial amine polymers, and reducing agents, S-PAcH exhibited significantly higher adsorption capacity, selectivity, and kinetics toward three PMs (gold, palladium, and platinum) with model, simulated, and real-world feed solutions. The superior PM recovery performance of S-PAcH was attributed to its strong reduction capability combined with its chemisorption mechanism. Moreover, PM-adsorbed S-PAcH could be refined into high-purity PMs via calcination, directly utilized (upcycled) as catalysts for dye reduction, or regenerated for reuse, demonstrating its high practical feasibility. Our proposed PM adsorbents would have a tremendous impact on various industrial sectors from the perspectives of environmental protection and sustainable development.

Amine-impregnated natural inorganic nanotubes via layer-by-layer electrostatically self-assembly approach for efficient CO2 adsorption

Developing cost-effective and high-performance solid amine adsorbents has considered as an important way to alleviate the greenhouse effect. How to precisely regulate its pore structure and surface interface characteristics, and how to cooperate to optimize the dynamic mass transfer and adsorption–desorption behavior of gas in the adsorbent are still challenging work. Herein, we demonstrated a facile and efficient approach to construct polyethyleneimine (PEI) impregnated halloysite nanotubes (HNTs) as an emerging nanocomposite for CO2 capture. Based on the natural electrostatic differences of inner and outer walls for HNTs, the hollow tubular structures of adsorbents were constructed by selective surface modification and layer-by-layer electrostatic self-assembly technology to improve the CO2 uptake capacity and cyclic stability, in which poly(sodium-p-styrene sulfonate) (PSS) and PEI were used as polyanionic and polycationic layer, respectively, to coat the inner walls of HNTs. The loading capacity of PSS-PEI composite ionic layers in HNTs and the influence of PSS polyanionic layer on PEI dispersion were specifically discussed according to the CO2 uptake capacity, adsorption heat, thermodynamics and kinetics of the adsorbents. The optimal PEI20-0.5PHNTs adsorbent exhibited a higher CO2 uptake of 0.87 mmol/g at 80 °C in the flow of 40 vol% N2/60 vol% CO2 than that of PEI20-HNTs, owing to the high amine efficiency due to the uniform dispersion of PEI in the electrostatic composite ionic layers. Furthermore, PEI20-0.5PHNTs reached 75 % of the maximum adsorption capacity at the 5th min of the adsorption process and released the most heat during adsorption at − 18.28 kJ/mol due to the presence of electrostatic composite ionic layers. PEI20-0.5PHNTs showed excellent cyclic stability with a slight loss of 7.4 %. The electrostatic self-assembled adsorbent obtained by layer-by-layer loading of PSS and PEI based on the unique surface charge characteristics of HNTs is an inspiration for the synthesis of cost-effective solid amine adsorbents for practical CO2 capture and separation.