Excellent Adsorption Ability Research Articles

Ferrous sulfide supported on modified diatomite for the removal of Cr(VI): Performance and mechanism

How to remove hexavalent chromium (Cr(VI)) from aqueous solution has always been a challenging problem in the environmental field. In this study, a novel composite of oxalic acid modified diatomite (DT) supported ferrous sulfide (FeS) was prepared by hydrothermal synthesis. The experiment results showed that the oxalic acid modified diatomite retained its original porous structure and possessed rougher surface, which could be used as a good loading/dispersing material to provide more adsorption sites. The composite material FeS/DT (the mass ratio of ferrous sulfide to modified diatomite is 1:1) can reduce more than 99 % of Cr(VI) to Cr(III) within 20 min, and Cr(III) can be adsorbed to the surface of diatomite. FeS/DT had a good adsorption and reduction effect at initial pH 3.0–9.0. The experimental results were in agreement with pseudo-second-order kinetic model and Langmuir isotherm adsorption model. Maximum adsorption capacity of FeS/DT for Cr(VI) can reach 141.6 mg/g. The reasons for the excellent reduction and adsorption ability of the FeS/DT were the reducibility of ferrous sulfide and porous structure of modified DT. This study revealed the reaction mechanisms of FeS/DT with Cr(VI), and demonstrated the feasibility of FeS/DT in the removal of Cr(VI) from water environment.

A theoretical study of the effect and mechanism of FeN3-doped biochar for greenhouse gas mitigation

Paddy fields are a major emission source of greenhouse gases (GHGs) [for instance, methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2)] among agricultural fields. Biochar has been deemed a potential candidate for the reduction of GHGs in paddy fields. However, there is no consistent conclusion that biochar can simultaneously reduce emissions of CH4, N2O, and CO2. Herein, we proposed the FeN3-doped biochar (FG) as an excellent material for GHGs restriction in paddy fields via the first-principles calculation. The computation results indicated that the FG exhibited satisfactory adsorption ability for CH4, CO2, and N2O, which improved the adsorption energies to −1.37 , −1.54, and −2.91 eV, respectively. Moreover, the density of state (DOS) analyses revealed that the factor responsible for FeN3-doped biochar to exhibit excellent adsorption ability was the occurrence of drastic energy up- or down-shift of the electron for Fe d, C p, O p, or N p orbital upon adsorption of CH4, CO2, or N2O. Our study suggested an advanced modified biochar material for reducing the GHGs emissions in paddy fields, in addition to exploring the adsorption properties and mechanisms of FeN3-doped biochar for GHGs mitigation, which provided a strategy to explore biochar modification and efficient emission reduction materials.Graphical

Light-Driven Self-Cascade Peroxidase-like Nanozymes without Exogenous H2O2.

The peroxidase (POD)-like nanozyme typically requires the addition of exogenous H2O2. To address the limitation, previous work mainly adopted a cascade strategy for H2O2 production. Herein, we propose a new light-driven self-cascade strategy to construct POD-like nanozymes without exogenous H2O2. The model nanozyme resorcinol-formaldehyde resin-Fe3+ (RF-Fe3+) is synthesized with the hydroxyl-rich photocatalytic material RF as the carrier to in situ chelate metal oxides, which can simultaneously achieve the functions of in situ H2O2 generation under irradiation and substrate oxidation via POD-like behavior. Notably, RF-Fe3+ exhibits high affinity to H2O2, attributed to the excellent adsorption ability and hydroxyl-rich feature of RF. Furthermore, the dual photoelectrode-assisted photofuel cell was further constructed with a high-power density of 120 ± 5 μW cm-2 based on the RF-Fe3+ photocathode. This work not only demonstrates the new self-cascade strategy of in situ generation of catalysis substrates but also provides an opportunity to extend the catalytical field.

Activated carbon microspheres with high surface area for efficient organic contaminants removal

Modified carbon microspheres with large specific surface area (1334 m2 g−1) and abundant microporous structure are prepared using glucose as raw material via a simple hydrothermal and subsequent activation-carbonization process. The KHCO3 activation markedly increases the specific surface area (> 6 times) and pore volume (> 4 times) of obtained carbon microspheres, which endow it with excellent adsorption ability towards organic pollutants in aqueous solution. The KHCO3 activated carbon microspheres (KCMS) can efficiently remove 94 % methylene blue in 20 min (98 % in 60 min) at a low adsorbent dosage (10 mg adsorbent vs. 100 ml, 100 mg L−1 dye), and the saturation adsorption capacity reaches 1551.99 mg/g. The synergism of chemical interaction, pore filling effect, π-π interaction, hydrogen bond formation and electrostatic attraction gives KCMS excellent adsorption performance. The KCMS can be repeatedly used with high adsorption capacity. It also exhibits good adsorption ability towards rhodamine B (237.64 mg/g) and tetracycline (297.34 mg/g), indicating it is a wide range adsorbent. The results reveal that the activated carbon microspheres obtained by a simple process are efficient adsorbents for organic pollutants removal in wastewater. It suggests a new opportunity to develop novel low-cost adsorbent with excellent performance.

Electrospun aligned self-standing SnO2/Sb carbon nanofibrous anodic membrane for sulfamethoxazole electrocatalytic degradation

Recently, sulfamethoxazole (SMX) has become an emerging refractory antibiotic pollutant due to abuse and excessive use. In this study, self-standing PAN-based SnO2/Sb/CFs anodic membrane was fabricated by innovatively incorporating SnO2/Sb nanoparticles into carbon nanofibrous (CFs) membrane to treat the typical antibiotic, SMX. The significant sulfamethoxazole (SMX) degradation capacity by the SnO2/Sb/CFs nanofibrous anodic membrane was benefit from the excellent adsorption ability of CFs and the enhanced electrooxidation capacity by SnO2/Sb. In addition, the SnO2/Sb nanoparticles can further increase the oxygen evolution side reaction potential and improve conductivity. The flow-through nano-porous construction of SnO2/Sb/CFs membrane reactor can greatly improve the mass transfer rate and further enhance the degradation rate than the plate construction of conventional electrode. The anodic electrocatalysis on sulfamethoxazole (SMX) testing proven that, the optimal electrocatalytic conditions is at the 2.5 V applied potential, pH at 6, the degradation rate reached 67 % in 1 h at the initial SMX concentration of 10 mg/L. And non-toxic smaller intermediates of SMX were identified by LC-MS/MS, suggesting the refractory and highly toxic SMX was electrochemically degraded into small non-toxic molecules. The outstanding SMX electrochemical degradation performance and anodic carbon nanofibrous membrane stability indicated the SnO2/Sb/CFs anodic membrane has enormous potential to treat the refractory antibiotics from the wastewater.

Electrospun Nanofiber Membrane: An Efficient and Environmentally Friendly Material for the Removal of Metals and Dyes.

With the rapid development of nanotechnology, electrospun nanofiber membranes (ENM) application and preparation methods have attracted attention. With many advantages such as high specific surface area, obvious interconnected structure, and high porosity, ENM has been widely used in many fields, especially in water treatment, with more advantages. ENM solves the shortcomings of traditional means, such as low efficiency, high energy consumption, and difficulty in recycling, and it is suitable for recycling and treatment of industrial wastewater. This review begins with a description of electrospinning technology, describing the structure, preparation methods, and factors of common ENMs. At the same time, the removal of heavy metal ions and dyes by ENMs is introduced. The mechanism of ENM adsorption on heavy metal ions and dyes is chelation or electrostatic attraction, which has excellent adsorption and filtration ability for heavy metal ions and dyes, and the adsorption capacity of ENMs for heavy metal ions and dyes can be improved by increasing the metal chelation sites. Therefore, this technology and mechanism can be exploited to develop new, better, and more effective separation methods for the removal of harmful pollutants to cope with the gradually increasing water scarcity and pollution. Finally, it is hoped that this review will provide some guidance and direction for research on wastewater treatment and industrial production.

CeO2-g-C3N4 S-scheme heterojunctions for enhanced photocatalytic performance: Effects of surface C/N ratio on photocatalytic and adsorption properties

In this work, novel CeO2–C-g-C3N4 S-scheme heterojunctions with significantly enhanced photocatalytic performance were prepared for the first time by a facile one-step molten KCl–LiCl method. The formation mechanism of CeO2–C-g-C3N4 was discussed, where g-C3N4 turned to C by carbonizing and the surface C content was adjusted by controlling the synthesis conditions. The photocatalytic property of the ternary composites first increased and then decreased with synthesis temperature and time. The 580 °C 4h CeO2–C-g-C3N4 exhibited the best performance towards MB (Methylene blue) and TC (Tetracyclines) degradation with a removal degree of 99.9% and 92.5%, respectively. The surface C/N ratio was a key index that influenced the photocatalytic performance, and was calculated to be 0.918–1.352 for various CeO2–C-g-C3N4 catalysts. The 580 °C 4h CeO2–C-g-C3N4 had an appropriate C/N ratio of 0.930 and a narrow band gap. The formed S-scheme 2D heterojunctions and generated C clearly promoted the separation of photo-excited e-/h+. Besides, it was indicated that e- and ·O2− were the main active species for TC photodegradation. The 580 °C 4h CeO2–C-g-C3N4 exhibited a large BET surface area, high negative zeta potential, strong π-π electron donor-acceptor interaction, and an excellent MB adsorption ability. It was evident that chemisorption on catalyst surface played an important role for adsorbing MB. The formation mechanism of CeO2–C-g-C3N4 and the effects of the surface C/N ratio on photocatalytic performance, determined in this work, offer new insights for preparing and structuring highly effective photocatalysts, which is expected to promote further photocatalytic and adsorption applications.

Bi2Sn2O7/UiO-66-NH2 heterojunction photocatalyst simultaneously adsorbed and photodegraded tetracycline

A series of Bi2Sn2O7/UiO-66-NH2 nanoparticles were synthesized by in-situ solvothermal method as efficient adsorption and visible-light-driven photocatalysts for the removal of tetracycline（TC）. Among them, the BUN16 presents excellent adsorption and degradation ability for the TC, which is more than 3.6 times that of monomers. The adsorption-enhanced degradation mechanism of BUN16 nanomaterials was revealed via BET, XPS, Zeta potential, FT-IR, EPR, EIS and kinetic analysis, meanwhile the performance of removing TC decreased slightly after five cycles. The excellent catalytic performance can be attributed to its excellent adsorption capacity and the synergistic effect of the Z-type heterojunction charge transfer mechanism. This work provides a basic principle for the scientific construction of Z-type heterojunction materials with adsorption catalytic function to remove TC in actual wastewater.

Alpha-MnO2 nanoneedle embedded in MgO-chitosan biochar for higher removal of arsenic from groundwater: Co-effects of oxidation and adsorption

High performance and high permeability of reactive materials are crucial issues for the remedy of arsenic (As)-enriched groundwater by permeable reactive barriers. The remediation strategy integrating adsorption and oxidation has gained wide concerns due to its deep removal for As(Ⅲ). In this study, a granular bifunctional nanocomposite MgO-Chitosan-MnO2 (MgO-CS-MnO2) was fabricated as permeable reactive media for the in-situ remediation for high As groundwater. The needle structure of MnO2 could provide adequate oxidation sites, furthermore, the multilayer porous characteristic of MgO-CS could also meet higher adsorption capacity. As a result, the estimated maximal adsorption capacity of MgO-CS-MnO2 for As(Ⅲ) reached to 266.61 mg/g and 578.05 mg/g for arsenate (As(Ⅴ)), which are much higher than current similar adsorbents. The adsorption behaviors of As(Ⅲ/Ⅴ) follow pseudo-second-order kinetic model and Freundlich isotherm model, suggesting that both As(Ⅲ) and As(Ⅴ) are mainly chemisorbed onto MgO-CS-MnO2. It could perform effectively in a broad range of pH values (3−11), moreover, competing oxyanions (CO32-, NO-, and SO42-), organic matters (humic acid) and ion strength exert no significant influence towards As remediation. XPS results revealed As(Ⅲ) adsorbed onto composite completely transformed to As(Ⅴ), and removal mechanisms involved oxidation and metal-O-As(Ⅲ/Ⅴ) complexation. In addition, it can be easily regenerated and recycled maintaining an excellent adsorption and oxidative ability. Besides, Column experiment demonstrated this composite column could effectively treat 1300 and 1700 bed volume (BV) of synthetic As(Ⅲ/Ⅴ)-contaminated groundwater, respectively. Therefore, MgO-CS-MnO2 have a great potential applicability towards high As groundwater improvement as permeable reactive media.

High-efficiency removal of Cs (I) by vermiculite/zinc hexacyanoferrate (II) composite from aqueous solutions

Aimed to solve the problems of low adsorption capacity, complex preparation and difficult recovery for reported cesium ion adsorbents, a novel high-efficiency Cs+ adsorbent of vermiculite/zinc hexacyanoferrate (II) (VMT/ZnHCF) composite was prepared via in situ synthetic method. The structure and properties of this composite were comprehensively characterized using XRD, FTIR, SEM, TEM, and TG-DTA. The maximum Cs+ adsorption capacity was recorded to be 378.79 mg/g, and this value was significantly higher than the values recorded for other absorbents. This spontaneous and exothermic adsorption behavior could be explained by the Langmuir isotherm model and the pseudo-second-order kinetic model. In addition, this composite exhibited excellent selective adsorption ability towards Cs+ even in solutions containing high concentrations of Na+, K+, Ca2+, and Mg2+. The Cs+ adsorption mechanism was analyzed by conducting ion exchange experiments and using XRD, SEM, and XPS techniques. The Cs+ adsorption of the VMT/ZnHCF composite was synergistically achieved through the ion exchange of Na+ in vermiculite interlayers and Zn2+ in zinc hexacyanoferrate (II) lattices. A high-efficiency and simple preparation of cesium ion adsorbent has been developed in application of cesium ion wastewater treatment. This work can provide theoretical guidance to realize the non-hazardous treatment of radioactive wastewater.

Synthesis of grape-seed derived carbon with high specific surface area for CO2 selective adsorption

Nitrogen-doped porous carbons with BET surface area of 1068.2–3314.5 m2/g and nitrogen contents of 3.2–6.5% were prepared with solid waste grape-seed as raw material, NaNH2 as activator and nitrogen source at low activation temperature. Super The activation mechanism of NaNH2 on hydrothermal carbon precursors was first explored by thermodynamic analysis and TG-IR, which provided theoretical support for pore forming of carbon materials. Maximum CO2 and CH4 adsorption capacity at 273 K and pressure of 101 kPa was 5.42 and 1.76 mmol g−1 respectively, which are higher than those of majority of carbon derived from most solid wastes reported in literature. IAST selectivities of GS-3-450 with the largest BET surface area for CO2/CH4 (40v/60v), CO2/N2 (15v/85v), CH4/N2 (50v/50v) were found to be 20.3, 71.4, 6.0 under 101 kPa and 298 K respectively. The competitive adsorption of GS-3-450 for CO2/CH4 (40v/60v), CO2/N2 (15v/85v), CH4/N2 (50v/50v) gases mixture were examined through breakthrough experiments, and the results showed that the breakthrough time of CO2 was longer than that of CH4 and N2, which was beneficial to the separation of CO2 from gases mixture. Eight cycles of CH4 adsorption–desorption studies revealed that the material exhibited excellent recycling stability. Low temperature preparation method, excellent BET specific surface area and total pore volume, as well as excellent adsorption ability of CO2 and CH4 make it have a very great potential for the capture of CO2 and CH4.

Silicic Acid Removal by Metal-Organic Frameworks for Silica-Scale Mitigation in Reverse Osmosis.

Reverse osmosis (RO) membranes are susceptible to silica scaling, resulting in irreversible degradation of membrane performance. This work covered the fabrication of MIL-101(Fe) for silicic acid adsorption to alleviate the silica scaling of RO membranes. The effect of pH, mixing time and initial concentration on silicic acid adsorption of MIL-101(Fe) was appraised in detail. The adsorption experiments demonstrated that MIL-101(Fe) possessed an excellent adsorption ability for silicic acid with the maximum adsorption capacity reaching 220.1 mgSiO2·g-1. Data fitting confirmed the pseudo-second-order equation and Freundlich equation were consistent with silicic acid adsorption on MIL-101(Fe). Finally, a simulated anti-scaling experiment was carried out using a feed solution pretreated by MIL-101(Fe) adsorption, and the permeance exhibited a much lower decline after 24 h filtration, confirming that MIL-101(Fe) exhibits an excellent application potential for silica-scale mitigation in RO systems.

The construction of magnetic hydroxyapatite-functionalized pig manure-derived biochar for the efficient uranium separation

In this work, three magnetic biochar-supported nano-hydroxyapatite materials were prepared by endowing different magnetic sources, which showed excellent reusability and adsorption ability. It was worth mentioning that the maximum adsorption capacity of the magnetic biochar-hydroxyapatite composite with nickel chloride as the magnetic source reached 1723.5 mg/g and the residual concentration of uranium in the solution could reach the limit standard of China for the discharge of uranium-containing wastewater at low uranium concentration. The removal efficiencies of the composite for uranium in different water systems were all higher than 90.2 %, which reflected the applicability of the composite. Besides, the material was easy to be recycled and reused due to the magnetization. After eight times of reuse, the uranium removal efficiency was still higher than 96.3 % and the magnetism was not significantly weakened. The multiple strong chemical reactions of active sites with uranium, including ion exchange, surface complexation and ionization-precipitation, were the major reason for the excellent adsorption ability. In conclusion, the magnetization of biochar-based materials might be a promising uranium adsorbent, which would open a new direction for the design of biochar-based adsorbents for uranium removal.

High-entropy nanoparticle constructed porous honeycomb as a 3D sulfur host for lithium polysulfide adsorption and catalytic conversion in Li–S batteries

A porous honeycomb-like sulfur host was engineered using oxidized six-element HEA nanoparticles (MgCrMnFeCoNi–O), offering excellent lithium polysulfide adsorption ability and catalytic activity toward the conversion of sulfur species.

An accuracy improved ratiometric SERS sensor for rhodamine 6G in chili powder using a metal-organic framework support.

Internal standard molecule 4-mercaptobenzoic acid (4-MBA) embedded Au core-Ag shell nanorods (Au-MBA@Ag NRs) were prepared by a seed-mediated growth method, then loaded on octahedral MIL-88B-NH2 to obtain a novel ratiometric SERS substrate of Au-MBA@Ag NRs/PSS/MIL-88B-NH2 (AMAPM) for detecting rhodamine 6G (R6G) in chili powder. The porous structure and excellent adsorption ability of MIL-88B-NH2, allowed for increased loading of Au-MBA@Ag NRs, thereby shortening the distance between adsorbed R6G and the "hot spot" resulting from local surface plasmon resonance (LSPR) of Au-MBA@Ag NRs. Based on the SERS characteristic peak ratio of R6G to 4-MBA, the ratiometric SERS substrate displayed improved accuracy and excellent performance for R6G detection, with a wide linear range of 5-320 nM and a low detection limit of 2.29 nM as well as fine stability, reproducibility and specificity. The proposed ratiometric SERS substrate offered a simple, fast and sensitive sensing strategy for R6G detection in chili powder, which demonstrated potential applications in food safety and the analysis of trace analytes in complex matrices.

Excellent adsorption ability of Hg(II) by poly(o-phenylenediamine) modified mesoporous materials

Excellent adsorption ability of Hg(II) by poly(o-phenylenediamine) modified mesoporous materials

Construction of porous materials from Pickering high internal-phase emulsions stabilized by zein-Hohenbuehelia serotina polysaccharides nanoparticles and their adsortion performances

The present research was designed to fabricate the food-grade porous materials (PM) by Pickering emulsions template method. Firstly, two kinds of nanoparticles with small average sizes and negative zeta potentials were respectively prepared based on zein and Hohenbuehelia serotina polysaccharides (HSP) by physical interaction (ZHNPs) and Maillard reaction (MZHNPs). Then, the Pickering high-internal-phase emulsions (PHIPEs) were constructed with different concentration of ZHNPs or MZHNPs serving as stabilizer. Finally, PM-ZHNPs and PM-MZHNPs were respectively prepared based on ZHNPs-stabilized PHIPEs and MZHNPs-stabilized PHIPEs template. PM prepared by different condition possessed the semi-crystalline property and the porous reticular structure. Moreover, all the porous materials were hydrophilic. Adsorption capacity measurements showed that PM not only exhibited the excellent adsorption ability on water by active/passive mode but also presented the strong adsorption performances on oil and pigments. Furthermore, PM could effectively adsorb the Pb 2+ dissolved in simulated gastrointestinal digestive juice. This study provided a theoretical basis for construction of the biosafety porous materials applied in food industries. • ZHNPs and MZHNPs were respectively prepared by zein and HSP with or without Maillard reaction. • PM were fabricated by ZHNPs-stabilized or MZHNPs stabilized PHIPEs template method. • The structural properties and morphology of PM were characterized and observed. • PM presented the excellent adsorption performances on water, oil, pigments and Pb 2+ ion.

CeO2-CDs clusters decorated Co(OH)2 nanosheets for improved photocatalytic ammonia synthesis

The green synthesis process of photocatalytic ammonia production has received more and more attentions. Herein, a Z-scheme heterojunction with all-solid-state structures is constructed, in which carbon dots can act as electron transferring mediators. The photocatalytic measurement shows that the modified photocatalysts exhibit much higher activities, in which the ammonia production rates can reach above 232 µmol·gcal-1·h−1 under the light irradiation. The improved catalytic properties can be credited to the significantly increased number of photoinduced oxygen vacancies, the excellent visible-light adsorption abilities and photogenerated electron-hole separation efficiencies for the carbon dots bridged heterostructures. More hydroxyl and superoxide radicals can be simultaneously produced in the composites. This work provides reasonable guidance for applications in photocatalytic ammonia synthesis and a promising construction strategy of efficient Z-scheme photocatalysts.

Selective separation and immobilization process of 137Cs from high-level liquid waste based on silicon-based heteropoly salt and natural minerals

• Silicon-based composite adsorbent was effective for 137 Cs removal. • The interaction mechanism of Cs was studied at the molecular level by density functional theory. • A conceptual process for separation and long-term safe disposal of Cs was proposed. A macro porous silica-based ammonium phosphomolybdate (AMP/SiO 2 ) adsorbent was synthesized and tested for separation and recovery of 137 Cs from real radioactive liquid waste. The excellent adsorption ability and high selectivity of AMP/SiO 2 for 137 Cs were confirmed. AMP/SiO 2 had relatively large decontamination efficiency of 137 Cs exceeding 99% in radioactive wastes, and the decontamination factors of 137 Cs were estimated to be 688 and 270 after adsorption in radioactive waste at 1 and 3 mol/L HNO 3 , respectively. In column operation, the separation and recovery of Cs(I) and coexisting ions could be realized using different eluents, and the recovery rate of Cs(I) was more than 90%. The Cs 3d and Mo 3d X-ray photoelectron spectroscopic spectra of AMP/SiO 2 before and after Cs(I) adsorption, suggesting that the ion exchange process of cesium with crystal lattice cations was the governing mechanism, and cesium ions could spontaneously react with approximately two ammonium ions in each AMP lattice by density functional theory simulation. Further, the crystal binding energy of each revised model showed an upward trend with the progress of the adsorption. After sintering at 1200 °C, CsAlSiO 4 , which could stably solidify eluted cesium, was formed in the allophane-based solidified product. The crystalline properties and volume reduction effect of the sintered products were enhanced with the increase in the allophane content. Ba(II) hardly entered the lattice of CsAlSiO 4 and occupied the Cs(I) site, resulting in minor changes in the crystal structure with substitution of Ba(II) for Cs(I).

Carbon nanofibers embedded with tiny CoNi bimetals as the functional interlayer for high-performance lithium–sulfur batteries

Free-standing carbon nanofibers have been recognized as an effective interlayer to improve sulfur cathode electronic conductivity and inhibit shuttling of polysulfides. However, carbon materials show a limited effect on improving electrochemical performance of lithium–sulfur batteries (LSBs) due to their nonpolar and weak physical limitations for the dissolvable polysulfides. It has been reported that introducing chemical bonds between polar compounds and polysulfides helps to suppress the shuttle effect of polysulfides via combining physical confinement with chemical adsorption. Herein, free-standing N-doped carbon nanofibers embedded with bimetallic CoNi (CoNi@N-CNFs) are constructed as an interlayer for LSBs. Apart from improving electronic conductivity of the sulfur cathode, the CoNi@N-CNF interlayer also displays excellent adsorption ability to the dissolvable polysulfides and promotes conversion reactions between sulfur species. Under the synergistic effect of the carbon framework and CoNi bimetals, the CoNi@N-CNF interlayer achieves decent electrochemical performance with a high initial discharge capacity of 1563 mAh g−1 at 0.2C and 0.53% capacity decay per cycle during 100 cycles.