Congo Red Adsorption Capacity Research Articles

Ionic liquid-water interfacial synthesis of ionic liquid incorporated metal-organic frameworks with enhanced adsorption properties

In the present work, a two-phase system composed of a hydrophobic ionic liquid (IL) containing copper ions (Cu(II)) and water containing organic linkers was constructed and the Cu-based metal-organic framework (Cu-MOF) formed at the IL-water interfaces at room temperature. The IL 1,3-bis(carboxymethyl)imidazolium chloride ([BCMIM]Cl) was also introduced in the MOF structures via using it as co-linker. The adsorption capacity of the synthesized Cu-MOF and [BCMIM]Cl modified Cu-MOFs was evaluated using the organic dye Congo red (CR) as target compound. Experimental results suggested that the incorporation of [BCMIM]Cl in the Cu-MOF remarkably improved the CR adsorption capacity due to the strong π-π and electrostatic interactions between the cation of [BCMIM]Cl and CR. The adsorption behavior of CR on [BCMIM]Cl modified Cu-MOF fitted well with pseudo-second-order kinetics and Freundlich isotherm model. Thermodynamic analysis suggested the adsorption of CR on [BCMIM]Cl modified Cu-MOF was a physical adsorption process. Finally, compared with reported adsorbents, the [BCMIM]Cl modified Cu-MOF exhibited higher CR adsorption capacity, indicating that it was a promising adsorbent for the removal of organic dyes from water.

Cd2+ and Zn2+ Complexes with 2,4,6-Tri(2-pyridyl)-s-Triazine and Terephthalate for Rapid, High-Capacity Adsorption of Congo Red.

Three crystal complexes were designed and synthesised through the solvothermal method, with Cu2+ , Zn2+ , and Cd2+ ions as the metal centres and 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ) and terephthalate (BDC2- ) as the ligands. Their compositions were determined to be Cd(TPTZ)Cl2 (Cd-MOF), {[Zn(TPTZ)(BDC)] ⋅ 3H2 O}n (Zn-MOF), and Cu2 (PCA)2 (BDC)(H2 O)2 (Cu-MOF) (PCA- =2-pyridinium amide), respectively. Cd-MOF can adsorb 90 % of Congo red (CR) in 10 s at room temperature and atmospheric pressure, and CR removal was complete at 20 s over a wide pH range. The adsorption capacity for CR reached 1440 mg g-1 in 5 min. Selective adsorption was demonstrated in mixed dyes. The adsorption kinetic data agree well with the pseudo-second-order kinetic model. The Temkin model was successfully used to evaluate the adsorption isotherms of CR on Cd-MOF at room temperature, suggesting that adsorption occurs through a hybrid of monolayer and multilayer mechanisms.

Extremely Fast and Efficient Removal of Congo Red Using Cationic-Incorporated Hydroxyapatite Nanoparticles (HAp: X (X = Fe, Ni, Zn, Co, and Ag))

Congo red (CR) is a stable anionic diazo dye that causes allergic reactions with carcinogenic properties. The rapid removal of CR using cation-incorporated nanohydroxyapatite (pristine HAp: X (X = Fe, Ni, Zn, Co, and Ag)) was investigated. The pristine and cation ion-doped HAp adsorbents were coprecipitated and subjected to hydrothermal and ultrasound treatments and subsequent microwave drying. The dopant ions significantly engineered the crystallite size, crystallinity, particle size (decreased 38–77%), shape (a rod to sphere modification by the incorporation of Ag+, Ni2+, and Co2+ ions), and colloidal stability (CS) of the adsorbent. These modifications aided in the rapid removal of the CR dye (98%) within one minute, and the CR adsorption rate was found to be significantly higher (93–99%) compared to previously reported rates. Furthermore, the kinetic, Langmuir, Freundlich, and DKR isotherms and thermodynamic results confirmed that the CR adsorption on the HAp was due to the strong chemical adsorption process. The order of the maximum CR adsorption capacity was Fe-HAp > HAp > Ag-HAp > Co-HAp > Zn-HAp. Whereas the CR regeneration efficiency was Fe-HAp (92%) > Ag-HAp (42%) > Ni-HAp (30%), with the other adsorbents exhibiting a poor recycling efficiency (1–16%). These results reveal Fe-HAp as a potential adsorbent for removing CR without the formation of byproducts.

Insight into the adsorption of magnetic microspheres with large mesopores: Tailoring mesoporous structure and ethylenediamine functionalization for ultrahigh Congo red removal

In this study, ethylenediamine (EDA)-functionalized magnetic microspheres with large mesopores (MMMs) were fabricated and explored for the use as highly efficient adsorbents to remove Congo red (CR). The size of mesoporous channels and loading of EDA functional groups were adjusted to optimize the CR adsorption performance of resulting adsorbents. It was found that higher specific surface area (SBET) was favorable for greater CR adsorption, while increasing EDA loading resulted in CR adsorption capacity with a change of first increasing and then declining. The optimal adsorbent FSN-2 with 1.71 wt% N content possessed an ultrahigh maximum CR adsorption capacity of 1662 mg/g, ascribed to its high SBET of 530.91 m2/g and large average pore size of 8.78 nm. The experimental data were fitted best by using the Langmuir model and pseudo-second-order model, suggesting that the adsorption feature be monolayer and chemosorption. The thermodynamic parameters, i.e.ΔG, ΔH and ΔS, were also estimated, indicating the CR adsorption onto FSN-2 was spontaneous and endothermic in nature. High adsorption capacities were recorded in a wide pH range of 5.0 – 9.0, while the addition of Cl-, SO42- and NO3– had negligible effect on its CR removal. Moreover, FSN-2 showed good reusability and high stability in adsorption–desorption cycles, as well as excellent CR removal capacity in simulated actual wastewater. The adsorption mechanisms of CR onto FSN-2 mainly involved electrostatic attraction and hydrogen bonding. This work provides a new insight into the fabrication of highly efficient magnetic adsorbents by optimizing the porous structure and functional group loading for potential practical application in wastewater treatment.

Interface synthesis of Cu-BTC/PVDF hybrid membranes and their selective adsorption activity toward Congo red.

Considering the surface affinity of MOFs and separation advantages of polymer membranes, herein, a one-step interface synthesis strategy is used in the construction of Cu-BTC/PVDF hybrid membranes, in which Cu2+ ions and 1,3,5-benzenetricarboxylic acid (H3BTC) were dissolved in ionized water and n-octanol separately, and polyvinylidene fluoride (PVDF) films were laid at the interface of two immiscible solvents. As a result, Cu-BTC was generated and readily self-assembled inside the PVDF films. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and the Brunauer-Emmett-Teller (BET) method were used to characterize Cu-BTC/PVDF hybrid membranes, and Congo red (CR) was selected as the target dye to evaluate the surface adsorption activity of the hybrid membranes. Batch adsorption tests under various conditions were conducted to optimize the adsorption capacity, adsorption kinetics, isotherms and thermodynamics, which were analyzed to further explore the adsorption behavior. Based on this, the adsorption mechanism was discussed. It is worth noting that because of the π-π stacking interaction and hydrogen bonding, an extraordinary adsorption capacity of CR was achieved, and the good separation advantage and the cyclic adsorption performances endow the resulting Cu-BTC/PVDF hybrid membranes with promising applications in the removal of organic dyes from practical wastewater.

A magnetically recyclable lignin-based bio-adsorbent for efficient removal of Congo red from aqueous solution

It has been always attractive to design a sustainable bio-derived adsorbent based on industrial waste lignin for removing organic dyes from water. However, existing adsorbent strategies often lead to the difficulties in adsorbent separation and recycling. Herein, we report a novel magnetically recyclable bio-adsorbent of Mg(OH)2/Fe3O4/PEI functionalized enzymatic lignin (EL) composite (EL-PEI@Fe3O4-Mg) for removing Congo red (CR) by Mannish reaction and hydrolysis-precipitation. The Mg(OH)2 and PEI functionalized EL on the surface act as active sites for the removal of CR, while the Fe3O4 allows for the easy separation under the help of a magnet. As-obtained EL-PEI@Fe3O4-Mg forms flower-like spheres and has a relatively lager surface area of 24.8 m2 g−1 which is 6 times that of EL. The EL-PEI@Fe3O4-Mg exhibits a relatively high CR adsorption capacity of 74.7 mg g−1 which is 15 times that of EL when initial concentration is around 100 mg L−1. And it can be easily separated from water by applying an external magnetic field. Moreover, EL-PEI@Fe3O4-Mg shows an excellent anti-interference capability according to the results of pH values and salt ions influences. Importantly, EL-PEI@Fe3O4-Mg possesses a good reusability and a removal efficiency of 92 % for CR remains after five consecutive cycles. It is illustrated that electrostatic attraction, π-π interaction and hydrogen binding are primary mechanisms for the removal of CR onto EL-PEI@Fe3O4-Mg. This work provides a novel sustainable strategy for the development of highly efficient, easy separable, recyclability bio-derived adsorbents for removing organic dyes, boosting the efficient utilization of industrial waste lignin.

Different Adsorption Behaviors and Mechanisms of Anionic Azo Dyes on Polydopamine–Polyethyleneimine Modified Thermoplastic Polyurethane Nanofiber Membranes

Considering the notable mechanical properties of thermoplastic polyurethane (TPU), polydopamine–polyethyleneimine (PEI) -modified TPU nanofiber membranes (PDA/PEI-TPU NFMs) have been developed successfully for removal of anionic azo dyes. The adsorption capacity of PDA/PEI-TPU NFMs was evaluated using three anionic dyes: congo red (CR), sunset yellow (SY), and methyl orange (MO). Interestingly, it exhibited different adsorption behaviors and mechanisms of CR on PDA/PEI-TPU NFMs compared with SY and MO. With the decrease in pH, leading to more positive charges on the PDA/PEI-TPU NFMs, the adsorption capacity of SY and MO increased, indicating electrostatic interaction as a main mechanism for SY and MO adsorption. However, wide pH range adaptability and superior adsorption have been observed during the CR adsorption process compared to SY and MO, suggesting a synergistic effect of hydrogen bonding and electrostatic interaction, likely as a critical factor. The adsorption kinetics revealed that chemical interactions predominate in the CR adsorption process, and multiple stages control the adsorption process at the same time. According to the Langmuir model, the maximum adsorption capacity of CR, SY and MO were reached 263, 17 and 23 mg/g, respectively. After six iterations of adsorption–desorption, the adsorption performance of the PDA/PEI-TPU NFMs did not decrease significantly, which indicated that the PDA/PEI-TPU NFMs have a potential application for the removal of CR molecules by adsorption from wastewater.

Adsorption Characteristics of Some Azo Dye on Nanobiocomposite in a Column Operation

Unfixed dyes released from various industries directly impact on the environment quality which is quite alarming and a matter of concern. In the present study, the removal of a carcinogenic azo dye, congo red (CR), was modelled for column adsorption dynamics following batch study in aqueous solution using iron modified cellulose nanobead. The effect of process parameters has been described for both batch and column study. Adsorption capacity of CR in the batch mode and column mode was calculated to be 3.29 and 8.69 mg g−1 respectively. The elution of retained CR from FeCNB phase was performed using 1.0 x 10-1 mol dm-3 NaOH and the maximum elution was found to be 81.25%. The experimental data were well described by BDST model.

Nonhydrolytic sol-gel in-situ synthesis of high performance MgAl2O4/C adsorbent materials

MgAl2O4/C composite was prepared via a facile low-temperature non-hydrolytic sol-gel (NHSG) route, using Mg powder, Al wire and isopropanol as raw materials. The influence of types of magnesium source and heat treatment temperature on the synthesis and adsorption properties were investigated, and the adsorption mechanism was also studied. The results showed that the amorphous MgAl2O4 formed at < 600 °C, and it crystallized at 700 °C. No impurity phase appeared in the samples calcined at 700–1300 °C, which was attributed to MgAl2O4 crystallized directly from Mg(Al(OiPr)4)2. The uniform-doped carbon in MgAl2O4/C composites came in-situ from the organic groups in Mg(Al(OiPr)4)2. MgAl2O4/C showed a superior adsorption capacity for Congo red (CR). The bimetallic alkoxides structure was favorable for high adsorption property, and the adsorption property of amorphous MgAl2O4/C was significantly superior to that of its crystalline counterpart. The adsorption kinetics data was fitted with the pseudo-second-order model, while the Langmuir isotherm model could well descript the adsorption isotherm behavior, and the maximum adsorption capacity for CR was 5690 mg/g. The high adsorption capacity was attributed to the Lewis acid-base reaction and the electrostatic interactions between the anionic dye CR and MgAl2O4/C surface as well as the in-situ carbon, and amorphous state.

Core-Shell Hierarchical Fe/Cu Bimetallic Fenton Catalyst with Improved Adsorption and Catalytic Performance for Congo Red Degradation

The preparation of heterogeneous Fenton catalysts with both adsorption and catalytic properties has become an effective strategy for the treatment of refractory organic wastewater. In this work, 4A-Fe@Cu bimetallic Fenton catalysts with a three-dimensional core-shell structure were prepared by a simple, template-free, and surfactant-free methodology and used in the adsorption and degradation of Congo red (CR). The results showed that the open three-dimensional network structure and the positive charge of the surface of the 4A-Fe@Cu catalyst could endow a high adsorption capacity for CR, reaching 432.9 mg/g. The good adsorption property of 4A-Fe@Cu for CR not only did not inactivate the catalytic site on 4A-Fe@Cu but also could promote the contact between CR and the active sites on the catalyst surface and accelerate the degradation process. The 4A-Fe@Cu bimetallic catalyst exhibited higher catalytic activity than monometallic 4A@Cu and/or 4A-Fe catalysts due to low work function value. The effects of different pH, H2O2 dosages, and catalyst dosages on the catalytic performance of 4A-Fe@Cu were explored. In the conditions of 7.2 mM H2O2, 2 g/L 4A-Fe@Cu, and 1 g/L CR solution, the degradation ratio of CR by 4A-Fe@Cu could reach 99.2% at pH 8. This strategy provided guidance to the design of high-performance Fenton-like catalysts with both adsorption and catalysis properties for dye wastewater treatment.

Synthesis of high surface area porous biochar obtained from pistachio shells for the efficient adsorption of organic dyes from polluted water

High surface area, micro, and mesoporous functionalized biochar were prepared from pistachio shells and utilized for the adsorption of congo red (CR) and methylene blue (MB) from polluted water. The results indicate that increased pyrolysis temperature improved the porosity, specific surface area (SBET), and pore size. The biochar obtained at 900 °C, named as PSB-900, possess an SBET of 467.8 m2/g with a pore diameter of 5.6 nm, which is higher than the SBET and pore size of the biochar obtained at 600 and 300 °C. The batch adsorption of CR and MB with PSB-900 was performed with different dye concentrations, adsorbent dosage, pH, and temperature to determine their impact on adsorption capacity. The experimental results were further validated with kinetics and isotherm statistics. The PSB-900 achieved the maximum adsorption capacity for CR, 614.7 and 384.2 mg/g for MB. By contrast, biochar obtained at 300 and 600 °C exhibited comparatively low adsorption capacity owing to the difficult pore-filling and low SBET. The characterization results indicate that pore filling, π-π interaction, hydrogen bonding, electrostatic interaction, and surface complexation were the fundamental features of the adsorption mechanisms of organic dyes on PSB-900. Furthermore, a reusability assessment was also conducted, and the results demonstrate that PSB-900 can be recycled after the adsorption process and exhibits good recyclability for multiple cycles.

Ultrasound-assisted preparation of Fe(OH)3@bacterial cellulose aerogel for efficient removal of organic contamination in water

As an abundant and renewable polymer, bacterial cellulose-based aerogel (BCA) loading with Fe(OH)3 nanoparticles was successfully prepared by ultrasound-assisted treatment and exhibited excellent adsorption efficiency for dye removal from polluted water. Wastewater containing toxic synthetic dyes is causing serious damage to the ecological environment and human health, and more attention has been paid to the nanoscale materials for water purification because of their unique structure and large specific surface area. With the help of ultrasonic waves, iron and hydroxide ions could fully penetrate the complex network of cellulose aerogel and generate the uniformed Fe(OH)3 particles, homogeneously being located all over the adsorbent. The physical adsorption from the multi-scaled pore structure in cellulosic aerogel and the chemical formation of electrostatic interaction and the hydrogen bonds between Fe(OH)3 and Congo red (CR) synergistically acted and significantly improved the absorbability. Finally, the maximum adsorption capacity of CR was achieved to 335 mg/g at natural conditions, which was higher than many reported values. The kinetics of the adsorption under different temperatures, pH, and time were comparatively measured, and the physical and structural characteristics were also investigated in detail using XPS, SEM, EDS, XRD, etc., technologies. Importantly, this approach is expected to provide a simple and operable process for fabricating cellulose-based aerogel and broadening the fields of applications.

Boehmite aerogel with ultrahigh adsorption capacity for Congo Red removal: Preparation and adsorption mechanism

As a toxic azo anion dye, Congo Red (CR) in waste-water poses a potential threat to the environment and human health. An absorbent is often used for its removal, during which, however, the role played by the functional groups is still not fully understood. In this work, a boehmite aerogel with a specific surface area as high as 305 m2/g was successfully developed by a combined sol–gel and freeze-drying method, and its CR adsorption capacity reached as high as 1962 mg·g−1. The adsorption process was dominated by a chemisorption mechanism and could be well described by the Langmuir isothermal model. The combination of the density functional theory (DFT) calculations and experimental results suggested that the amino protonation was responsible for the additional enhancement of CR adsorption in an acidic medium. The adsorption process occurred via interactions between boehmite aerogels and the SO3 functional groups of CR. Additionally, the NH3 group resultant from the protonation of NH2 functional groups of CR in an acidic medium significantly enhanced the CR adsorption on the boehmite aerogels. This work not only developed an ultrahigh efficiency anion adsorbent for CR removal, but also provided a new strategy for the exploration of new adsorbents with further improved performance.

Copolymer-type magnetic graphene oxide with dual-function for adsorption of variety of dyes

BackgroundTo solve the dye pollution, graphene oxide (GO) is an excellent substrate for developing novel adsorbents, meanwhile surface-initiated atom transfer radical polymerization (SI-ATRP) is a progressive modification to significantly promote density of functional groups and magnetic adsorbents can efficiently simple adsorption process. Therefore, our effort has been made to develop an ideal dye absorptive material with: (i) the high adsorption capacity, (ii) the high selectivity, (iii) the favorable regeneration and reuse and (iv) the simple and fast adsorption treatment. MethodsCationic and anionic monomers (sodium 4-styrenesulfonate, Nass and methacryloyloxyethyl trimethyl ammonium chloride, DMC) were grafted onto polydopamine coated magnetic GO (Fe3O4@GO@PDA) by SI-ATRP, obtaining copolymer brush-type Fe3O4@GO@PDA@poly(NASS-co-DMC) adsorbent with dual function of sulfonic acid and tertiary amino groups. The adsorption properties of methylene blue (MB), basic fuchsin (BF), acidic fuchsin (AF), acidic chrome blue K (AK), rhodamine B (RhB) and congo red (CR) were studied. The selectivity of adsorbents was explored in mixed AF/MB solution, and further highlighted by using it to detect of MB and AF in lake water. The recycling and stability were tested by adsorption-desorption experiments in detail. Significant findingsThe adsorption capacities of MB, BF, AF, AK, RhB and CR reached 170.3, 289.7, 330.5, 148.7, 170.4 and 230.5 mg·g−1, respectively, that was found fits well with Langmuir adsorption isotherm and pseudosecond-order kinetic model. The responsible adsorption mechanisms are dominated by electrostatic interaction, hydrogen bond interaction and π-π stacking. Moreover, the adsorption selectivity of Fe3O4@GO@PDA@poly(NASS-co-DMC) could be adjustable by the regulating the ratio of NASS to DMC, and at 4:1, 1:1 and 1:4 of NASS to DMC, adsorbent generated the different recoveries in detection of MB and AF. Furthermore, the adsorbent was recycled multiple times still remained an excellent removal efficiency and structural stability. These findings demonstrates the developed dual-function adsorbent can be applied in the treatment and detection of wastewater containing both cationic and anionic dyes.

Fabrication of polystyrene/CuO@calcined layered double hydroxide microspheres with high adsorption capacity for Congo red

Adsorption is gaining popularity as an efficient, fast, and low-cost method for the removal of organic dyes in the wastewater treatment. In this work, a novel inorganic-organic adsorbent, polystyrene/CuO/calcined layered double hydroxide (PS/CuO@CLDH) microspheres, was successfully fabricated through the dispersion polymerization method for the efficient removal of Conon red (CR). The structure of the microspheres of products was characterized, and the marked impact of key variables (e.g., adsorbent dosage, pH, contact time, and initial dye concentration) on its adsorption was investigated. PS/CuO@CLDH10 exhibits the highest adsorption capacity compared with other composite materials, in which the adsorption capacity can reach 484.6 mg g−1 when the addition amount is 10 mg. Furthermore, the dynamics and isotherms fit better with the pseudo-second-order and Freundlich model. The adsorption thermodynamic data illustrate that the adsorption process of PS/CuO@CLDH10 on CR is endothermic, spontaneous, and thermodynamically feasible. Moreover, PS/CuO@CLDH10 maintains high removal efficiency and structural composition after four cycles, revealing its excellent recyclability and stability. Therefore, this work provides a novel idea for designing and fabricating inorganic-organic composites for efficient adsorption in wastewater treatment.

Fast and efficient removal of dyes and Cr(VI) ion from wastewater using halloysite nanotubes-covalently coated polyurethane sponges

Inspired by the mussel adhesion protein, dopamine was used to prepare polydopamine (PDA)-coated polyurethane sponge (PDA-PUS) via self-polymerization reaction. Halloysite nanotubes (HNTs) were grafted with γ-aminopropyltriethoxysilane (APTES). The new organic-inorganic hybrid adsorption material (HNTs@PUS) was fabricated by covalent link of APTES-grafted HNTs and PDA-PUS through Schiff base reaction/Michael addition. The as-prepared HNTs@PUS showed much higher mechanical stability and compressive property than polyurethane sponge (PUS). HNTs@PUS had 7.7, 7.1, 1.7 and 8.5 times adsorption capacity of PUS for Congo red (CR), Methyl orange (MO), Rhodamine 6 G (R6G) and heavy metal ion Cr(VI), respectively. HNTs@PUS had a fast adsorption rate and most of CR, MO, R6G and Cr(VI) were adsorbed by HNTs@PUS within 20 min. In addition, HNTs@PUS maintained 70.3%, 66.5%, 67.3% and 77.4% of its adsorption capacity for CR, MO, R6G and Cr(VI), respectively, after 5 cycles of regeneration. HNTs@PUS could be easily recovered to avoid secondary contamination. Besides, using HNTs@PUS as adsorbents, a continuous flow adsorption device was developed, through which anionic and cationic dyes and heavy metal ion could be continuously and effectively removed from the flowing solution. These results demonstrated that HNTs@PUS had potentially ideal attributes for use as adsorbents in the ultrafast, high efficiency and large-scale removal of anionic and cationic dyes and heavy metal ions from wastewaters. The fabrication strategy not only solved the problem of the poor recyclability and low permeability of HNTs, but also greatly improved the adsorption capacity of PUS, which might accelerate the application of natural “green” HNTs in wastewater treatment.

Synthesis of chitosan-modified magnetic metal-organic framework and its adsorption of Congo red and antibacterial activity

Although various nano-adsorbent have been developed for sewage treatment, only a few adsorbents possess antibacterial activities. We aimed to synthesis a double-purpose nano-adsorbent with adsorption and antibacterial activity. Magnetic composite materials (Fe3O4@ZIF-8@SiO2) with a porous crystalline state and large specific surface area were synthesized. Chitosan (CS) with broad-spectrum antimicrobial activity was used to functionalize the magnetic metal-organic framework nanocomposites. Fe3O4@ZIF-8@SiO2@CS were produced of low cost, mild conditions without any calcination step. Fourier transform infrared spectroscopy, scanning electron microscopy, the Brunauer-Emmett-Teller method, transmission electron microscopy, vibrating sample magnetometry, thermogravimetric analysis, X-ray diffractometry and X-ray energy dispersive spectrometry presented evidence that a new porous adsorbent Fe3O4@ZIF-8@SiO2@CS is rich in –NH2 and CS and have specific surface area of 420.58 m2/g. Fe3O4@ZIF-8@SiO2@CS has loose crystals, thermodynamically stable and well-defined structures, which are used for Congo red (CR) adsorption and bacterial cell killing. We determined optimal adsorption conditions by adjusting adsorption time, pH and ionic strength. Fe3O4@ZIF-8@SiO2@CS shows a good adsorption capacity of CR, reaching 310.4 mg/g at 298 K. The adsorption kinetics and adsorption isotherm obeyed the General-order kinetic (GO model) and Liu model, respectively. The Fe3O4@ZIF-8@SiO2@CS can remove dyes from simulated dye effluent, and it can be reproduced easily without centrifugation or filtration, with the adsorption efficiency exceeded 70% even after five cycles. Fe3O4@ZIF-8@SiO2@CS exhibited antibacterial activity against Staphylococcus aureus and Bacillus subtilis. Double-purpose Fe3O4@ZIF-8@SiO2@CS can be a potential material for wastewater treatment.

Ultrafine biosorbent from waste oyster shell: A comparative study of Congo red and Methylene blue adsorption

High value utilizations of waste oyster shell and industrial waste heat play the crucial roles in field of environmental protection. Crushed shell powder has expended specific surface and exposed chitin and the character makes it suitable for adsorption. Industrial waste heat can be used as energy resource of steam jet mill to produce shell powder with different particle sizes. And this method has relatively great potential in cleaner production since it avoids extra contamination. Average particle size of products decreases sharply from 27.75 μm to 8.15 μm. Specific surface and exposed chitin increase with the decreasing particle size. The results of adsorption experiments indicate powder with smaller diameters has relatively high adsorption capacity of Congo red (CR) increased by 48.3% and Methylene blue (MB) by 62.5% compared with pristine shell powder. Meanwhile, the adsorption capacity of CR is higher than that of MB due to cationic chitin.

One-step coprecipitation synthesis of Cl− intercalated Fe3O4@SiO2 @MgAl LDH nanocomposites with excellent adsorption performance toward three dyes

A magnetic Cl−-intercalated Fe3O4@SiO2@MgAl-Cl− LDH nanocomposite has been successfully synthesized by modified one-step salt-assisted coprecipitation process. The Fe3O4@SiO2@MgAl-Cl− LDH nanocomposite was characterized by FTIR, XRD, XPS, SEM, HRTEM, BET and VSM. The results showed that the Fe3O4@SiO2@MgAl-Cl− LDH particles possessed core (Fe3O4@SiO2) shell (Cl− -LDH) structures and magnetic properties, and Cl− anions were successfully introduced into LDH interlayers. The unique intercalated structure with week interlayer interaction of Fe3O4@SiO2@MgAl-Cl− LDH provide efficient adsorption of methyl orange (MO), Congo red (CR) and methyl blue (MB), leading to its superior performance with much higher uptake capability with the maximum adsorption capacity of MO, CR and MB reaching 733 mg·g−1, 910 mg·g−1 and 385 mg·g−1, respectively. The adsorption process could be well described by pseudo-second-order model for MO, CR and MB. The experimental data of MO and CR could be fitted better with Freundlich model, while that of MB were fitted better with Langmuir model. The adsorption process was spontaneous and exothermic for MO and MB, while spontaneous and endothermic for CR. Moreover, the adsorbent exhibits excellent stability and reusability in the regeneration cycle, and a process called ‘‘post-processing step” is proposed to effectively improve the dye removal ability of the adsorbent in reuse. This study puts forward a new thought for the development of high-performance LDH adsorbents with mesoporous and Cl− intercalation structure for the efficient and rapid removal of dyes.

MOFs meet wood: Reusable magnetic hydrophilic composites toward efficient water treatment with super-high dye adsorption capacity at high dye concentration

Organic dye in water is a crucial global environmental problem. Notably, dyes, especially anionic dye Congo red (CR) and cationic dye Methylene blue (MB), have carcinogenic and mutagenic effects on human health. However, the commercial activated carbon with bad reusability is difficult to collect, which results in poor actual adsorption. In this paper, ZIF-67@wood obtained by in situ growth of ZIF-67 on wood is carbonized to prepare magnetic WC-Co composites. The hierarchical porous structure of wood can facilitate the rapid passage of dye solution, and promote full contact between magnetic core–shell Co/C nanoparticles and dyes. The adsorption capacities of CR and MB by Co/C-1000 are 1117.03 and 805.08 mg g−1, respectively. The pHpzc (7.9) of Co/C-1000 is then determined. When the dye concentration reaches 1200 mg L−1, the removal efficiency of Co/C-1000 reaches 99.98% under gravity. With the flux of 1.0 × 104 L m−2h−1 for CR solution (100 mg L−1), the removal efficiency of Co/C-1000 filter connected with peristaltic pump is almost 99.28%. In addition, the Co/C-1000 filter with high reusability and the adsorbed dyes can be removed by simple burning. This economical, recyclable and self-supporting filter with ultra-high adsorption capacity feature has the potential to replace commercial activated carbon and it will be widely used in practical wastewater treatment.