Adsorption Desorption Research Articles

In situ synthesis of carbon quantum dots on carbon felt fibers as a new solid-phase microextraction sorbent for chromatographic analysis of bisphenol A

In this study, an innovative and efficient solid − phase microextraction (SPME) sorbent was introduced based on carbon quantum dots (CQDs) modified carbon felt (CF) substrate. CF, due to its unique characteristics including high porosity, solvent durability (without swelling), and simple modification, it was proposed as an attractive platform for preconcentration purposes. To create an impressive adsorption capacity, the synergistic effects of CQDs and the carbonaceous structure of CF were profited off. CQDs were successfully synthesized on CF fibers by using an improved one-step hydrothermal method, and the resulting sorbent was referred to as CQDs@CF. Since bisphenol A (BPA) is an environmental toxin and can disrupt the endocrine system and potentially lead to cancer, highlighting the importance of detecting its presence. The prepared sorbent was used to extract bisphenol A (BPA) as a model compound from the real samples, followed by HPLC − UV analysis. Extraction parameters including desorption solvent type, and its volume, extraction, and desorption time, salting out effect and, solution pH were optimized. FESEM, EDX, FT − IR, and N2 adsorption–desorption were used to characterize the sorbent morphology, structure, and elemental contents. Under optimal conditions, the response linearity in the range of 0.05 − 500 ng mL−1 and detection limit at the level of 0.01 ng mL−1 were obtained. Additionally, the relative standard deviations (RSD) for newly prepared CQDs@CF (sorbent to sorbent repeatability) and a certain multi − used CQDs@CF (single sorbent repeatability) at a concentration of 100 ng mL−1 of BPA, were found to be 7.2 and 4.8, respectively.

Lithium Functionalization in a Three-Dimensional Graphene Monolith for Enhanced Adsorption–Desorption Hydrogen Storage

Lithium Functionalization in a Three-Dimensional Graphene Monolith for Enhanced Adsorption–Desorption Hydrogen Storage

Porous CePO4@carbon composite derived from cerium-based metal–organic framework for the simultaneous detection of dopamine, uric acid, and acetaminophen

Cerium phosphate (CePO4) has attracted increasing attention in the field of electrochemistry. In this work, a mesoporous CePO4@carbon composite was successfully prepared via the high-temperature calcination method using cerium-based metal–organic framework (Ce-MOF) as a precursor. The obtained samples were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption–desorption technique, and X-ray photoelectron spectroscopy (XPS). The findings revealed that the in-situ pyrolysis of Ce-MOF generated uniform composite, which showed high electrical conductivity and plenty of catalytic active sites. These structural advantages of the composite were conductive to the electron transfer, substrate diffusion, and redox reactions. Thereafter, CePO4@carbon was developed to modify the commercially purchased glass carbon electrode (GCE: CHI 104) for simultaneous detection of dopamine (DA), uric acid (UA), and acetaminophen (APAP). The linear detection ranges for DA, UA, and APAP were 2.5–310.0 μM, 3.0–305.0 μM, and 2.5–617.0 μM, respectively. The detection limits (LOD) for DA, UA, and APAP were 0.009 μM, 0.016 μM, and 0.014 μM, respectively. Furthermore, the constructed electrode can be employed to detect the concentration of DA, UA, and APAP in real-samples. This work provides a method for manufacturing highly efficient CePO4 based materials for electrochemical sensing.

Desorption of rare earth elements biosorbed on Euglena mutabilis suspensions and biofilms

AbstractIncreasing demand for rare earth elements (REEs) has stimulated research on novel recovery methods from sources like industrial effluents. Our recent study demonstrated that algal biofilms are good candidates for the adsorption of REEs and that the extracellular polymeric substances (EPS) within the biofilm were a key accumulator of REEs. In this work, we measured the desorption kinetics, extents, and selectivity of REEs from the algae Euglena mutabilis in suspensions and biofilms using aqueous solutions of HCl at pH between 1.5 and 4, and Na2EDTA at pH 5. We examined the potential for reusing suspended and biofilm biomass for repeated adsorption–desorption cycles. The desorption kinetics were similar for suspensions and biofilms, with equilibrium being reached within 20 min. The extent of desorption was higher in biofilms with 86% and 95% desorption, compared to suspensions which had 72% and 74% desorption using HCl and Na2EDTA, respectively. We postulate that the difference between suspensions and biofilms is attributed to the binding sites in the EPS matrix of the biofilm being more readily protonated than those at the algal cell wall surface. Heavy REEs were found to preferentially desorb at pH 4 over lighter REEs. After 3 repeated adsorption–desorption cycles, the adsorption capacity of biofilms increased by 280% and 80% using HCl and Na2EDTA, respectively, compared to an 80% decrease in biosorption capacity for the suspension. The increase in biofilm biosorption capacity was attributed to the simultaneous desorption of divalent cations alongside REEs from the EPS increasing the number of available binding sites.

Synthesis and sorption properties of hybrid composite materials based on saponite and copolymer 5-(4′-nitro)-phenylazo-8-methacryloxyquinoline: MMA

A new polymer–mineral composite was synthesized by adsorption of the copolymer of 5-(4′-nitro)-phenylazo-8-methacryloxyquinoline with methyl methacrylate on the surface of natural saponite clay. Using computer processing of isotherms of low-temperature adsorption–desorption of nitrogen, a decrease in the specific surface area of saponite after fixing this copolymer was recorded. Using the BJH method, it was calculated that after the adsorption of the copolymer, the average pore volume of the surface of the original mineral decreases and the average pore diameter increases. The sorption capacity of the synthesized composite concerning metal ions compared to the original mineral increases.

Management of caffeine in wastewater using MOF and perovskite materials: optimization, kinetics, and adsorption isotherm modelling

Pharmaceuticals and personal care products (PPCPs) have been increasingly used all over the world and they have been reported on water cycle and cause contamination. Among these pharmaceuticals is caffeine (CAF). In this work, CAF removal from aqueous samples by metal–organic framework (UIO-66) and perovskite (La0.7Sr0.3FeO3) was achieved. Detailed studies on the preparation of MOFs and perovskite oxides compounds have been presented. Extensive characterizations such as X-Ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared spectra (FT-IR), N2 adsorption–desorption isotherms were also carried out to assure proper formation and to better understand the physico-chemical behavior of the synthesized samples before and after adsorption. Batch experiments of CAF adsorption onto both MOFs and perovskite were performed to compare the effectiveness of both materials on the removal competence of the CAF residue at different conditions including the effect of pH, initial concentration, and contact time. It was observed that the adsorption capacity of CAF by MOF increased with increasing acidity. On the other hand, the adsorption capacity of perovskite is stable in pH 4–10. The maximum adsorption capacities of UiO-66 and perovskite toward CAF are high as 62.5 mg g−1 and 35.25 mg g−1, respectively. Equilibrium isotherms were investigated by numerous models: Langmuir, Freundlich, Temkin, Redlich-Peterson, Sips, Langmuir-Freundlich, Toth, Kahn, Baudu, and Fritz Schlunder. Moreover, the kinetics of the CAF@MOF and CAF@Perovskite systems have been studied by five kinetic models (Pseudo-1st -order (PFO), Pseudo-2nd -order (PSO), Mixed 1st, 2nd-order, Intraparticle diffusion and Avrami). The best model described the adsorption of CAF onto both of MOF and perovskite was the mixed 1st, 2nd-order model. The metal–organic framework and perovskite were applied to quickly extract CAF from water samples successfully. The maximum removal percentage obtained for MOF and perovskite was 0.89% and 0.94% respectively within 30 min contact time which suggests that these materials are considered as promising adsorbents for CAF.

Thiophene network polyamides (TPPA) with tri(4-aminophenyl)benzene: Synthesis and removal of Hg2+ from aqueous solution

In this study, the thiophenyl polyamide (TPPA) derived from tri(4-aminophenyl) benzene was synthesized for the removal of Hg2+ from the aqueous solution. The adsorbent was characterized by the Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, nitrogen adsorption–desorption, thermogravimetric analysis and differential scanning calorimetry. The adsorption capacity of Hg2+ is 518.7 mg g−1 at a dose of 1.1 g/L of adsorbent. TPPA was shown to have the following advantages: (i) the high selectivity for the excess metal ions Hg2+, (ii) the stability in the pH values ranging between 2 and 6, and (iii) the proper recyclability (87 % of Hg2+ can be removed in 5 adsorption–desorption cycles). Our analysis suggests the models of the pseudo-second-order kinetics and the Langmuir isotherm are suitable for the description of the adsorption of Hg2+ on the thiophene network polyamide. Our experimental and theoretical results reveal the relationship between the structures and the adsorption capacities of TPPA, identifying the oxygen atom (amide) and the sulphur atom (thiophene) as the most important chemical-reaction sites.

Sustainable Banana-Waste-Derived Biosorbent for Congo Red Removal from Aqueous Solutions: Kinetics, Equilibrium, and Breakthrough Studies

This study investigates the adsorption of Congo red (CR) dye from wastewater using banana peel biochar (BPBC) in both batch and fixed-bed column modes. BPBC was characterized using FTIR, SEM, XRD, TGA, and BET analysis, revealing a predominantly mesoporous structure with a surface area of 9.65 m2/g. Batch adsorption experiments evaluated the effectiveness of BPBC in removing CR, investigating the influence of the BPBC dosage, initial CR concentration, and solution pH. Results showed optimal CR removal at pH levels below 4, suggesting a favorable electrostatic interaction between the adsorbent and the dye. Furthermore, a pseudo-first-order kinetic model best described the adsorption process. The Freundlich isotherm provided a better fit compared to the Langmuir and Dubinin–Radushkevich (D-R) models, implying a heterogeneous adsorption surface. The calculated maximum adsorption capacity (Qm) from the Langmuir model was 35.46 mg/g. To assess continuous operation, breakthrough curves were obtained in fixed-bed column experiments with varying bed heights (1–3.6 cm). The results demonstrated efficient CR removal by BPBC, highlighting its potential for wastewater treatment. Finally, this study explored the feasibility of BPBC regeneration and reuse through four adsorption–desorption cycles.

Facile fabrication of sulfonated porous yeast carbon microspheres through a hydrothermal method and their application for the removal of cationic dye

Water pollution containing dyes become increasingly serious environmental problem with the acceleration of urbanization and industrialization process. Renewable adsorbents for cationic dye wastewater treatment are becoming an obstacle because of the difficulty of desorbing the dye from the adsorbent surface after adsorption. To overcome this dilemma, herein, we report a hydrothermal method to fabricate sulfonic acid modified yeast carbon microspheres (SA/YCM). Different characterization techniques like scanning electron microscopy, FTIR spectroscopy, and X-ray diffraction have been used to test the SA/YCM. Decorated with sulfonic acid group, the modified yeast carbon microspheres possess excellent ability of adsorbing positively charged materials. The removal rate of Methyl blue (MB) by renewable adsorbent SA/YCM can reach 85.3% when the concentration is 500 mg/L. The SA/YCM regenerated by HCl showed excellent regeneration adsorption capacity (78.1%) after five cycles of adsorption–desorption regeneration experiment. Adsorption isotherm and kinetic behaviors of SA/YCM for methylene blue dyes removal were studied and fitted to different existing models. Owing to the numerous sulfonic acid groups on the surface, the SA/YCM showed prominent reusability after regeneration under acidic conditions, which could withstand repeated adsorption–desorption cycles as well as multiple practical applications.

Covalent organic frameworks as dispersive solid-phase extraction adsorbents for β-lactam detection in aquatic environments

Currently, antibiotic residues in the environment pose a serious public health risk; therefore, new sensitive approaches for detecting the presence of antibiotics are urgently needed. Ionic-type covalent organic frameworks (TAPB-(TFIT)+Cl−-COFs) were designed and prepared in this work, and these imine-linked COFs were characterized by several techniques, proving of porous structure and rich of nitrogen. The materials were applied to the extraction of β-lactams from aqueous samples, and the important parameters of the adsorption–desorption conditions were optimized. A dispersive solid-phase extraction method coupled with ultrahigh-performance liquid chromatography-tandem mass spectrometry (TAPB-(TFIT)+Cl−-COFs-d-SPE-UPLC-MS/MS) was proposed and utilized to determine the levels of 11 antibiotics in the β-lactams in the extracted samples. Good linearity (1.0–200.0 μg·L−1, r > 0.9999) was achieved together with limits of detection and quantification of 0.01–0.92 μg·L−1 and 0.05–2.78 μg·L−1, respectively; recoveries ranged from 75.57 to 114.20 %, conferring relative standard deviations < 8.99 % and negligible matrix effects (84.88–109.40 %). The synthesized TAPB-(TFIT)+Cl−-COFs were demonstrated to have good reusability and high stability. Furthermore, the proposed method was clearly shown to be sensitive and separable for the reliable simultaneous detection of 11 β-lactam residues in aquatic environments.

Coin‐Shaped Carbon Prepared with Cerbera manghas Fibers via Multistage Carbonization and Activation for High‐Performance Symmetrical Supercapacitors

AbstractSupercapacitor energy storage devices and activated carbon (AC) manufacturing materials for producing high‐performance supercapacitors have received extensive attention from researchers. Biomass‐based AC has been extensively studied due to its environmental friendliness, abundant availability, porous structure, and high specific surface area. This work focuses on developing biomass‐based carbon electrodes derived from Cerbera manghas fiber (CMF) with variations in carbonization temperature to obtain optimum supercapacitor cell performance. The prepared CMF AC was characterized using energy dispersive X‐ray, Fourier transform infrared, X‐ray diffraction, scanning electron microscope, and nitrogen isothermal adsorption–desorption. CMF AC with the optimum carbonization temperature (CMF‐600) produced a fibrous structure with a lot of mesoporous so that the specific surface area and specific capacitance were high, namely, 721.495 m2 g−1 and 221 F g−1 at scan rate 1 mV s−1, respectively. The results of this study indicate that selecting the optimum temperature can enhance the performance of supercapacitor cells and make AC based on CMF biomass potential for cheap and efficient energy storage applications.

Bacterial and microalgal co-fixation for remediation of industrial wastewater contaminated with arsenic, mercury, and other pollutants

Microbial remediation is an efficient approach for improving heavy metal-contaminated water environments. Herein, this article developed a composite bacterial agent (CBA) with a high heavy metal tolerance. Within 12 h, the CBA demonstrated removal efficiencies of 65.18 ± 1.53% for As and 60.73 ± 0.94% for Hg in wastewater. This study prepared bacterial–algal fixed spheres (BAFS) to further enhance the removal efficiencies of As and Hg. Moreover, during desorption using 0.1 mol/L HNO3 for 60 min, the BAFS maintained high removal efficiencies for As and Hg after five adsorption–desorption cycles. Applying BAFS to industrial wastewater collected from factory outfall caused substantial reductions in chemical pollutants and other heavy metals. Scanning electron microscopy analysis further revealed that the internal cavities formed through the crosslinking of immobilized materials provided excellent survival carriers for bacteria and microalgae. Infrared spectroscopy analysis demonstrated the involvement of three functional groups, namely -OH, -CH2-, and C-O-C, in pollutant adsorption. Additionally, microbial community diversity analysis indicated that immobilization effectively preserved the pollutant adsorption ability of the microorganisms, increasing the abundance of functional microbial populations. These characteristics improved the efficiency of industrial wastewater treatment while promoting recycling.

Composition-engineered FeCo nanoalloys with lattice expansion and optimized electron structure boosting electrocatalytic Nitrate reduction

Herein, composition-engineered CoFe nanoalloys were in-situ constructed and confined in porous fibrous carbon by electrospinning and controlled graphitization, resulting in (110) lattice space expansion and improved free-electron-migration in nanoalloys, delivering bimetallic synergy by electron structural optimization. Impressively, the reinforced NO3- adsorption and rapid desorption of NH3 over composition-engineered nanoalloys efficiently promote the electrocatalytic dynamic behavior. As a result, the optimal Co1Fe1.5/C affords an excellent NH3 yield of 48.2 ± 1.2 mg h−1 mgcat−1 and a maximum Faraday efficiency of 90.8 ± 1.5 % at −1.1 V vs. RHE, with outstanding stability during 200 h NO3-RR, outperforming the most state-to-the-art catalysts. An excellent conversion of Nitrate (96.4 ± 0.8 %) with a high selectivity for Ammonia (94.4±1.2 %) can be validated. Detailed characterizations including in-situ XPS technique and theoretical calculation studies have demonstrated that Fe composition engineering reinforces the surface adsorption of NO3-, induces the surface electron redistribution of Co center, and optimizes the reaction pathways, resulting in the remarkable bimetallic synergy and enhancing the surface adsorption of a key intermediate of *NO over Co sites during the NO3-RR. Finally, the Zn-NO3- battery assembled by Co1Fe1.5/C was explored, which further indicates the potential of Co1Fe1.5/C in the energy conversion device.

Alkylation of Phenol with Methanol over ZSM‐5 Zeolite

AbstractThe catalytic performance of different molecular sieves in the alkylation of phenol with methanol to produce p‐cresol was evaluated, and the acidity and structure of the catalysts were characterized using N2 adsorption–desorption and Fourier transform infrared spectroscopy techniques. It was shown that the catalytic activity of molecular sieves was closely related to their acidic site number, specific surface area, and pore structure. Since Zeolite ZSM‐5 (Zeolites Socony Mobil No. 5) has a relatively small amount of strong acid as well as a small pore size, it is favorable for the diffusion of p‐cresol out of the pores. Therefore, focusing on ZSM‐5, the effects of operating conditions such as weight hourly space velocity (WHSV), phenol/methanol (P/M) ratio, and reaction temperature on the catalytic performance were investigated. The results showed that increasing the WHSV, P/M ratio, and reaction temperature improved the selectivity to cresol. In addition, X‐ray diffraction and Thermal Gravity/Differential Thermal Gravity characterization methods were also carried out for ZSM‐5, and it was found that the deactivation of ZSM‐5 was due to coke deposition and pore blockage on the active site and that the selectivity to cresol could be restored by regenerating the catalyst and covering the strong acid site, which resulted in the reduction of the strong acid site to increase the selectivity of the product.

Modification of new magnetic nanocomposites Bi2WO6/CuFe2O4 and its excellent catalytic reduction for toxic nitroaromatic compounds and chromium (VI)

New magnetic Bi2WO6/CuFe2O4 nanocomposites were synthesized using hydrothermal method. The specific features of Bi2WO6/CuFe2O4 nanocomposites were studied using various analytical techniques such as Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and N2 adsorption desorption analyses, Brunauer-Emmett-Teller (BET). The BET analysis demonstrates that embedded CuFe2O4 nanoparticles in Bi2WO6 structure have increased the pore diameters and surface area for better adsorption of NaBH4 and catalytic performance. The VSM analysis confirms the magnetic behavior of nanocomposite which showed that Bi2WO6/CuFe2O4 could be separated and recoverd easily by an external magnet after catalytic reactions. The catalytic performance of nanocomposites was investigated for the reduction of nitroaromatic compounds including 4-nitroaniline (4-NA), 4-nitrophenol (4-NP), 2-nitroaniline (2-NA) and 2-nitrophenol (2-NP) and chromium (VI) in aqueous solution. The results show the nanocomposites have excellent ability to reduces Cr(VI) to Cr(III) and nitroaromatic compounds to the corresponding amines in green water solution at room temperature. The best performance observed for the 100% conversion of 4-nitrophenol reduction belongs to Bi2WO6/CuFe2O4 20%, which completes in 6 min, and its rate constant is about 0.67 min−1. In addition, the Bi2WO6/CuFe2O4 nanocomposite can be appropriately recycled and reused several times without changing its structure and activity, which is essential for practical applications.

One-pot synthesis of quinazolinone heterocyclic compounds using functionalized SBA-15 with natural material ellagic acid as a novel nanocatalyst

The nanoporous compound SBA-15 was functionalized using (3-aminopropyl)trimethoxysilane (APTES). Then the obtained product was modified with ellagic acid (ELA), a bioactive polyphenolic compound. The structure of the prepared nanoporous composition SBA-15@ELA was extensively characterized and confirmed by various techniques, such as Fourier-transform infrared (FT-IR) spectroscopy, Energy dispersive X-ray (EDX) elemental analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 adsorption–desorption isotherms (BET). The novel, recoverable, heterogenous SBA-15@ELA nanoporous compound was used to investigate its catalytic effect in the synthesis of 4-oxo-quinazoline derivatives (19 examples) with high yields (78–96%), as an important class of nitrogen-containing heterocyclic compounds. The use of an inexpensive mesoporous catalyst with a high surface area, along with easy recovery by simple filtration are among the advantages of this catalysis research work. The catalyst has been used in at least 6 consecutive runs without a significant loss of its activity.

Design of a new nanocomposite based on Keggin-type [ZnW12O40]6− anionic cluster anchored on NiZn2O4 ceramics as a promising material towards the electrocatalytic hydrogen storage

Extensive research efforts have been dedicated to developing electrode materials with high capacity to address the increasing complexities arising from the energy crisis. Herein, a new nanocomposite was synthesized via the sol–gel method by immobilizing K6ZnW12O40 within the surface of NiZn2O4. ZnW12O40@NiZn2O4 was characterized by FT-IR, UV–Vis, XRD, SEM, EDX, BET, and TGA-DTG methods. The electrochemical characteristics of the materials were examined using cyclic voltammogram (CV) and charge–discharge chronopotentiometry (CHP) techniques. Multiple factors affecting the hydrogen storage capacity, including current density (j), surface area of the copper foam, and the consequences of repeated cycles of hydrogen adsorption–desorption were evaluated. The initial cycle led to an impressive hydrogen discharge capability of 340 mAh/g, which subsequently increased to 900 mAh/g after 20 cycles with a current density of 2 mA in 6.0 M KOH medium. The surface area and the electrocatalytic characteristics of the nanoparticles contribute to facilitate the formation of electrons and provide good diffusion channels for the movement of electrolyte ions throughout the charge–discharge procedure.

An effective way to utilize solid waste resources: The application of modified fly ash in removing Cu2+ and Pb2+ in wastewater

The sustainable development of society requires the support of developed industrial production, which inevitably produces a series of industrial by-products, including heavy metal-containing wastewater and solid waste. Using solid waste to adsorb heavy metal ions in wastewater is a sustainable way. This not only reduces the environmental threat caused by solid waste accumulation, but also reduces the treatment cost of heavy metal ions in wastewater. In this study, fly ash was modified to prepare magnetic adsorbent (M-AT), which was used to adsorb Cu2+ and Pb2+ in wastewater. The results showed that M-AT has a good adsorption effect on Cu2+ and Pb2+ in wastewater. Its maximum adsorption capacity for Cu2+ and Pb2+ was 53.18 and 85.86 mg/g, respectively. Ion exchange and complexation reaction were major adsorption mechanisms of M-AT for Cu2+ and Pb2+, they played an important role in the adsorption process. M-AT maintained a good adsorption effect on Cu2+ and Pb2+ under different influence factors. This ensured that M-AT can be used in complex application environments. In addition, M-AT exhibited good reusability, its removal rate for Cu2+ and Pb2+ reached 50.21 % and 75.15 % after 5 adsorption–desorption cycles. And the removal rate of M-AT for Cu2+ and Pb2+ in domestic sewage treatment plant influent, tailings drainage, industrial wastewater was 82.80 %, 87.12 %, 85.12 % and 95.10 %, 91.20 %, 93.13 %, respectively. These results proved the feasibility of M-AT in treating Cu2+ and Pb2+ in wastewater. This study provides a new way for the resource utilization of fly ash. Applying solid waste to treat heavy metal-containing wastewater is a sustainable way to treat industrial waste.

Construction of Bi2WO6/g-C3N4/Cu foam as 3D Z-scheme photocatalyst for photocatalytic CO2 reduction

Photocatalytic CO2 reduction to hydrocarbon fuels represents a promising solution to CO2 emission challenges. However, photocatalytic CO2 reduction systems face hurdles in practical utilization for the low efficiency of photocatalysts and challenge in catalyst immobilization. Therefore, a novel monolithic three-dimensional Z-scheme photocatalyst was synthesized by fabricating Bi2WO6/g-C3N4 heterojunction on Cu foam substrate (Bi2WO6/g-C3N4/Cu foam) via thermal polymerization and electrophoresis deposition. A series of characterization results, including X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and N2 adsorption–desorption, illustrate the crystalline properties, pore structure, and morphology of the composite photocatalyst. Consequently, Bi2WO6/g-C3N4/Cu foam achieved CO production yield of 33.84 μmol/g cat under visible light illumination for 6 h and retained 96.2 % of initial photocatalytic activity after 30 h of reaction. UV–Vis diffuse reflection spectra, photoluminescence spectra and photoelectrochemical analysis was involved to reveal the mechanism of the photocatalytic activity of composite photocatalyst.The synergistic effect of the Z-scheme mechanism and the hierarchical macroporous structure improves the light absorption, light-induced electron-hole pair separation, and charge transmission. This catalyst construction strategy provides a viable approach for facilitating practical photocatalytic CO2 reduction.

Covalent organic framework@cellulose nanofibrils@carboxymethyl cellulose composite hydrogel beads for the removal of nickel ions from aqueous solutions

A novel adsorbent, covalent organic framework (COF)@cellulose nanofibrils (CNF) @carboxymethyl cellulose (CMC) composite hydrogel bead (CCCHB), was prepared for Ni2+ removal from aqueous solutions. The imine COF provides the main active sites for adsorption. CNF is used as the carrier for grafting COF to improve the dispersion of COF and the reinforcing material. CMC is used as the hydrogel matrix to facilitate easy recycling. The equilibrium adsorption capacity (qe) of the CCCHB is vastly influenced by the mass ratio of COF@CNF/CMC. The optimized mass ratio of COF@CNF/CMC is 0.050/1 (g/g). The maximum adsorption is reached at pH=6. The qe of Ni2+ increases with a rise in initial concentration of the solution. Based on Langmuir isotherms, the maximum adsorption capacity of CCCHB is 289.50 mg/g. The adsorption of Ni2+ complies with the pseudo-second-order kinetic model. The CCCHBs still maintain preferable adsorption properties after the seventh cycle of adsorption–desorption. The Ni2+adsorption of the CCCHB is mainly attributed to the chelating effect and electrostatic interaction.