Adsorption Capacity For Malachite Green Research Articles

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.

Comprehensive analysis of cationic dye removal from synthetic and industrial wastewater using a semi-natural curcumin grafted biochar/poly acrylic acid composite hydrogel.

Polymer composites offer a tailored framework as an exceptional candidate for water treatment due to their tunable chemical structure, porous 3D architecture, physiochemical stability, accessibility, pH-sensitivity and ease of use. In this study, curcumin-engineered biochar is embedded into a cross-linked polyacrylic acid hydrogel matrix using in situ polymerization for developing a semi-natural adsorbent for the removal of cationic dye from an aqueous solution. The physicochemical features of the generated composite hydrogel are significantly influenced by the implementation of curcumin-grafted biochar into the polyacrylic acid substrate. Comprehensive characteristic approaches were employed to explore all aspects of the adsorbent's properties, especially its removal efficacy. The methodical adsorption study was accomplished by monitoring dynamic factors such as pH, adsorbent content, time frame, and initial dye concentration. The presence of the porous aromatized structure of biochar, active oxygen-enrich functional groups (carboxyl, hydroxyl, keto, enol, ether) coupled with the conjugated curcumin structure facilitate the effective establishment of hydrogen bonds, electrostatic interactions, π-π interactions, electron donor-acceptor and charge-assisted H-bonding with the malachite green (MG) and rhodamine B (Rho) molecules. The highest adsorption capacities of MG and Rho reached 521 mg g-1 and 741 mg g-1 respectively, in the range of neutral pH, considering their molecular nature, functionalities, and unique adsorption mechanisms. The isothermal modeling was carried out with Henry, Langmuir, Jovanovic, Freundlich, Temkin, and Koble-Corrigan models to determine the adsorption system. Additionally, the kinetic data were assessed with Bangham, pseudo-first-order, pseudo-second-order, intra-particle, and liquid film diffusion models to ascertain the rate-limiting phase. The Koble-Corrigan and Langmuir isotherm models (R2 > 0.997) as well as pseudo-second-order (R2 > 0.998) and Elovich (R2 = 0.983 and 0.995) kinetics models provide a substantial level of concordance with empirical findings. The analysis of non-linear diffusion models revealed that the Bangham (R2 > 0.995) pore and liquid film diffusion (R2 > 0.960) models has major influence on the rate of the adsorption procedure. The binary adsorption test demonstrated higher efficacy of the synthesized adsorbent in the removal of malachite as compared to rhodamine. This study sheds light on the design of a cost-effective semi-natural polymeric composite for treating dye-polluted wastewaters, a major milestone toward environmental and ecological sustainability.

Magnetic Porous Carbon from Biomass for Malachite Green Removal

For years, environment protection, especially how to purify industrial and agricultural wastewater, has been a disputable issue. The scarcity of water resources increases the urgency of wastewater recycling. Meanwhile, emitting wastewater into rivers and farmland deteriorated environmental issues. To solve this problem, a low-cost and efficient way to produce porous carbon which can adsorb organic solute and then be removed is being discussed in this report, aiming to separate organic pollutants from wastewater. In this report, ferric chloride, potassium carbonate, and biomass (like sawdust) are used to fabricate porous carbon. These ingredients all low-cost and easy to be found in usual laboratory, suggesting that it is simple to imitate this method. Porous carbon produced in this method has excellent specific surface area of 1517 m2/g, which has an adsorption capacity for MG (malachite green) aqueous solution of 988.6 mg/g in maximum.

Preperation of sodium alginate-based SA-g-poly(ITA-co-VBS)/RC hydrogel nanocomposites: And their application towards dye adsorption

A superabsorbent polymer, Sodium Alginate-g-Poly (Itaconic acid-co-Sodium 4-vinyl benzenesulfonate)/ Ricinus communis (SA-g-P(ITA-co-VBS)/ RC) hydrogel, was prepared by free-radical graft co-polymerization for sequestration of toxic malachite green (MG) dye as a cationic dye model. The surface morphological of shape and composition of the prepared hydrogel used have been characterized by FESEM, EDX, TEM, FTIR, X-ray diffraction XRD, and TGA. Optimizing the synthesis conditions for prepared a hydrogel with the highest swelling ratio have been studied, the results show that employing 0.08 g KPS and 0.09 g MBA, 1.0 g ITA, 2.0 g VBS, 1.0 g SA, and 1.0 g RC, the composites greatest swelling capacity in distilled water was 3400 %. It was discovered that the dye adsorption capacity of the polymer was greatly impacted by the monomer VBS level in the hydrogel, which gives it a better ability to swell. The porosity of the hydrogel spheres, thus significantly enhancing the MG adsorption capacity with the rate-limiting controlled by chemical adsorption, intraparticle diffusion, and film diffusion. Study the influence of different reaction conditions on the removal of MG dye from aqueous solution are adsorbent dose, pH, zero-point charge, temperature, thermodynamic adsorption, adsorption isotherm, and kinetic models have been done. Additionally, (SA-g-P(ITA-co-VBS)/RC) demonstrated strong MG dye adsorption capabilities and reusability in at least four adsorption-desorption cycles this process indicating its considerable potential for use as the adsorbent for dye removals from aqueous solution.

Sargassum macro-algae-derived activated bio-char as a sustainable and cost-effective adsorbent for cationic dyes: A joint experimental and DFT study

Activated bio-char prepared from the pyrolysis and CO2-based physical activation of Sargassum macro-algae was developed as a sustainable and cost-effective adsorbent for malachite green (MG) and methylene blue (MB) adsorption. Prepared activated bio-char was characterized with CHNS, FESEM, Raman, FT-IR and N2 adsorption/desorption methods. Langmuir isotherm and pseudo second order kinetics model best fitted equilibrium and kinetics data. The maximum adsorption capacity for MG and MB were 500 and 204.8 mg/g. The effect of solution pH and temperature on adsorption efficiency was studied and discussed. Acid treatment easily regenerated the adsorbent. After 5 cycles, the MB and MG adsorption efficiency reached 89 % and 78 %, respectively. A Density Functional Theory (DFT) calculation showed that pH-N-(CH3)2 of MB was strongly attracted to the -COOH functional groups in activated bio-char. For MG, the order of preferred interactions between the ph-N-(CH3)2 groups and the functional groups of adsorbent was -CONH2>-COOH>-COH.

Construction of hollow mesoporous zirconia nanospheres with controllable particle size: Synthesis, characterization and adsorption performance

Organic dyes are difficult to remove effectively in water because of their stable physical and chemical properties. In this study, hollow mesoporous zirconia nanospheres with controllable particle sizes were successfully prepared by in-situ deposition of Zr(OH)4 on the surface of SiO2. The adsorption performance for malachite green (MG) and methylene blue (MB) were tasted. The adsorption removal rates for MG and MB could reach as high as 99 % and 98 %, respectively. The adsorption process could be explained by pseudo-second-order kinetic model and Langmuir isotherm model, and the maximum adsorption capacities for MG and MB were calculated by Langmuir model as 1354.24 and 24.63 mg/g, respectively. Thermodynamic study indicated that the adsorption process of MG and MB were spontaneous endothermic and spontaneous exothermic, respectively. The adsorption mechanism of hollow zirconia nanospheres for MG and MB mainly includes electrostatic interaction, hydrogen bonding and π-π interaction. The results of co-existence ions study demonstrated that the presence of Mg2+ and Ca2+ obviously reduced the removal rates of MB. Desorption-regeneration study showed that the adsorbents can be used for multiple cycles.

Facile synthesis of magnetic ZnAl layered double hydroxides and efficient adsorption of malachite green and Congo red

Excessive dye effluent has contaminated the ecosystem, and it is challenging to effectively remove dye from the aqueous system. In the present work, magnetic Zn-Al layered double hydroxides (MZA) was synthesized via co-precipitationmethod for the adsorption of malachite green (MG) and Congo red (CR) in the aqueous solution. The successful synthesis of MZA was characterized by SEM-EDS, XRD, FT-IR BET and VSM. The batch experiments were conducted to investigate the effect of various adsorption parameters on the adsorption capacity of MG and CR by MZA, such as MZA dosage, solution pH, etc. Further adsorption studies, kinetics, isotherm, and thermodynamic were performed to explore the adsorption behavior of MG and CR on MZA. The maximum adsorption capacity at 298 K for MG and CR on MZA were 850.93 and 279.09 mg/g, respectively. Adsorption kinetics followed the pseudo-second-order model. Adsorption thermodynamics showed spontaneous, endothermic for MG and CR adsorption on MZA. The electrostatic attraction, hydrogen bonding, and molecular intercalation mainly occurred during adsorption process. In addition, MZA exhibited higher adsorption capacityafter 4 cycles of continuous adsorption–desorption. In conclusion, MZA might be a potential adsorbent for purifying wastewater containing MG and CR.

Removal performance and adsorption kinetics of dyes by a Co-based metal organic framework

A succession of Zr-based porphyrinic metal-organic frameworks (Zr-MOFs) are synthesized with metalation and utilized as adsorbents for removal of the cationic dye malachite green (MG) and the anionic dye methyl orange (MO). Results show the optimal adsorbent is MOF-525(Co) and the removal efficiencies for MG and MO by MOF-525(Co) are 99.0% and 90.5% at 60 min as the initial dye concentration is 100 mg L−1. The N2 adsorption/desorption results indicate the high surface area, micropore of MOF-525(Co); the FT-IR spectra and adsorption thermodynamics results demonstrate that the adsorption mechanisms of both MG and MO by MOF-525(Co) belong to the π-π stacking interactions of physical adsorption, and the hydrogen bonds and Co–O bond of chemical adsorption. Additionally, the optimal pH of dye adsorption is 7.0 for MG and 3.0 for MO, and the adsorption capacities of MG and MO decrease in saline solution. The adsorption kinetics reveal that the pseudo-second-order kinetic model is better for illustrating the adsorption performances of both dyes by MOF-525(Co); the adsorption isotherm models suggest that the Freundlich model is fitted for MG adsorption but the Langmuir is fitted for MO. Furthermore, the adsorption processes can be demonstrated as spontaneous, exothermic for MG with negative entropy but endothermic for MO with positive entropy by thermodynamics data. In conclusion, MOF-525(Co) possesses a significant adsorption ability and excellent reusability for MG, and it could be a promising adsorbent for MG removal.

Preparation of Reusable Porous Carbon Nanofibers from Oxidized Coal Liquefaction Residue for Efficient Adsorption in Water Treatment.

Porous carbon nanofibers are commonly used for adsorption processes owing to their high specific surface area and rich pore structure. However, the poor mechanical properties of polyacrylonitrile (PAN)-based porous carbon nanofibers have limited their applications. Herein, we introduced solid waste-derived oxidized coal liquefaction residue (OCLR) into PAN-based nanofibers to obtain activated reinforced porous carbon nanofibers (ARCNF) with enhanced mechanical properties and regeneration for efficient adsorption of organic dyes in wastewater. This study examined the effects of contact time, concentration, temperature, pH, and salinity on the adsorption capacity. The adsorption processes of the dyes in ARCNF are appropriately described by the pseudo-second-order kinetic model. The maximum adsorption capacity for malachite green (MG) on ARCNF is 2712.84 mg g-1 according to the fitted parameters of the Langmuir model. Adsorption thermodynamics indicated that the adsorptions of the five dyes are spontaneous and endothermic processes. In addition, ARCNF have good regenerative performance, and the adsorption capacity of MG is still higher than 76% after 5 adsorption-desorption cycles. Our prepared ARCNF can efficiently adsorb organic dyes in wastewater, reducing the pollution to the environment and providing a new idea for solid waste recycling and water treatment.

Fabrication of demethylated lignin-based micro-particle for efficient adsorption of malachite green from aqueous solution

Recently, the research on low-cost and renewable lignin-based adsorbent for the effective removal of organic dyes from wastewater has attracted great interest. Herein, a demethylated lignin-based micro-particle (DLMP) adsorbent with high hydroxyl content was prepared by using AlCl3 as modification reagent, which exhibited an excellent adsorption capacity for malachite green (MG). The results showed that the size distribution of DLMP was about 100–500 nm, the surface area reached 17.35 m2/g, and the phenolic hydroxyl (Ar-OH) group content was up to 5.77 mmol/g, which was much better than that of originally organosolv lignin (OL). With this DLMP as the lignin-based adsorbent, all adsorption processes fitted well with the Langmuir isothermal and the Pseudo-second-order kinetic models. The maximum adsorption capacity for MG reached 168.24 mg/g, which was higher than most of the previously published biomass-based adsorbents. Simultaneously, DLMP adsorbent could be easily regenerated, obtaining outstanding recyclability. After eight cycles, the adsorption capacity of DLMP retained at 144.59 mg/g. Finally, the investigation of the possible adsorption mechanism suggested that the synergistic interactions of electrostatic force, hydrogen bonding, π-π stacking and the superior micro-size structure significantly improved the adsorption property. In conclusion, DLMP adsorbent displays a high adsorption capacity and an excellent recyclability for the removal of MG, which might have widespread prospect in the low-cost and renewable biomass-based adsorbent.

Adsorption–desorption behavior of malachite green by potassium permanganate pre-oxidation polyvinyl chloride microplastics

Microplastics (MPs) and the typical hydrophilic organic pollutant Malachite green (MG) are frequently detected in sewage treatment plants. Potassium permanganate (KMnO4) pre-oxidation is an economical and effective technology in wastewater treatment. It is important to study the surface physicochemical characteristics of MPs and understand their fate in wastewater treatment plants after pre-oxidation. In this study, Polyvinyl chloride (PVC) MPs were treated by single and composite KMnO4 pre-oxidation with different pH values. After the pre-oxidation treatment, the appearance of OMn spectra and surface nanoparticles indicated the oxides (MnO2) were produced on the MPs surface. Moreover, the adhesion of MnO2 is helpful to improve the hydrophilicity and adsorption capacity of MG. The adsorption capacity of pristine PVC for MG was 2.6 mg/g. But the adsorption capacity increased to 7.0 mg/g for single oxidation and 140.7 mg/g for composite oxidation, respectively. The desorption experiment results indicate the pre-oxidation process could reduce the release efficiency of MG from the PVC MPs due to the better binding of surface MnO2 nanoparticles to MG. However, the total desorption capacity is still high. which illustrates that there is a high potential risk of MG which can transfer from the surface of the PVC MPs to the gastrointestinal fluids.

Dual-functional marine algal carbon-based materials with highly efficient dye removal and disinfection control.

The design and simple, green preparation of dual-functional materials for the decontamination of both hazardous dyes and pathogenic microorganisms from wastewater remain challenging currently. Herein, a promising marine algal carbon-based material (named C-SA/SP) with both highly efficient dye adsorptive and antibacterial properties was fabricated based on the incorporation of sodium alginate and a low dose of silver phosphate via a facile and eco-friendly approach. The structure, removal of malachite green (MG) and congo red (CR), and their antibacterial performance were studied, and the adsorption mechanism was further interpreted by the statistical physics models, besides the classic models. The results show that the maximum simulated adsorption capacity for MG reached 2798.27mg/g, and its minimal inhibit concentration for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was 0.4mg/mL and 0.2mg/mL, respectively. The mechanistic study suggests that silver phosphate exerted the effects of catalytic carbon formation and pore formation, while reducing the electronegativity of the material as well, thus improving its dye adsorptive performance. Moreover, the MG adsorption onto C-SA/SP showed vertical orientation and a multi-molecular way, and its adsorption sites were involved in the adsorption process with the increase of temperature. Overall, the study indicates that the as-made dual-functional materials have good applied prospects for water remediation.

Dummy Template-Based Molecularly Imprinted Membrane Coating for Rapid Analysis of Malachite Green and Its Metabolic Intermediates in Shrimp and Fish

A novel malachite green molecularly imprinted membrane (MG-MIM) with specific selectivity for malachite green (MG) and leucomalachite green (LMG) was prepared using a hydrophobic glass fiber membrane as the polymer substrate, methyl violet as a template analog, 4-vinyl benzoic acid as the functional monomer, and ethyleneglycol dimethacrylate as the crosslinking agent. MG-MIM and non-imprinted membrane (NIM) were structurally characterized using scanning electron microscopy, surface area analyzer, Fourier-transform infrared spectrometer and synchronous thermal analyzer. The results showed that MG-MIM possessed a fluffier surface, porous and looser structure, and had good thermal stability. Adsorption properties of MG-MIM were investigated under optimal conditions, and adsorption equilibrium was reached in 20 min. The saturated adsorption capacities for MG and LMG were 24.25 ng·cm-2 and 13.40 ng·cm-2, and the maximum imprinting factors were 2.41 and 3.20, respectively. Issues such as "template leakage" and "embedding" were resolved. The specific recognition ability for the targets was good and the adsorption capacity was stable even after five cycles. The proposed method was successfully applied for the detection of MG and LMG in real samples, and it showed good linear correlation in the range of 0 to 10.0 μg·L-1 (R2 = 0.9991 and 0.9982), and high detection sensitivity (detection limits of MG and LMG of 0.005 μg/kg and 0.02 μg·kg-1 in shrimp, and 0.005 μg/kg and 0.02 μg/kg in fish sample). The recoveries and relative standard deviations were in the range of 76.31-93.26% and 0.73-3.72%, respectively. The proposed method provides a simple, efficient and promising alternative for monitoring MG and LMG in aquatic products.

Cu-ZIF@ red soil nanocomposite sufficient sorbent for dye removal

In this study, Cu-ZIF and Cu-ZIF@ Red soil Nano composite were synthesized in room temperature. Red soil, Cu-ZIF and Cu-ZIF@ Red soil Nano composite were fully characterized by different techniques such as Fourier transform spectroscopy infrared (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), elemental mapping, BET and thermal gravimetric analysis (TG). The results of FESEM indicated Cu-ZIF@ Red soil had meso porous nature with uniform spherical shape of 30 nm. The XRD result showed the main phase of red soil was hematite (Fe2O3) and hexagonal crystal system (primitive R3) and α-SiO2 and the crystal structure of red soil and Cu-ZIF remain unchanged after formation of composite. Adsorption of malachite green (MG) by prepared samples were studied. The highest percent of MG adsorption was occurred at contact time of 60 min, pH 10, and adsorbent dose of 0.1 g. Kinetic studies indicated that the adsorption of MG follows by pseudo second-order model. Thermodynamic results revealed that the adsorption of MG is endothermic, spontaneously process and feasible in the range of 298–338 K. The adsorption isotherm experimental data was fitted better by Langmuir model than Freundlich model. The maximum adsorption capacity of MG for Red soil, Cu-ZIF and Cu-ZIF@ Red soil Nano composite was observed 132, 366.6 and 382 mg g−1, respectively at pH 10. Cu-ZIF@ Red soil Nano composite acts as sufficient reusable sorbent for MG dye.

Competition adsorption of malachite green and rhodamine B on polyethylene and polyvinyl chloride microplastics in aqueous environment.

Microplastics (MPs) will cause compound pollution by combining with organic pollutants in the aqueous environment. It is important for environmental protection to study the adsorption mechanism of different MPs for pollutants. In this study, the adsorption behaviors of malachite green (MG) and rhodamine B (RhB) on polyethylene (PE) and polyvinyl chloride (PVC) were studied in single systems and binary systems, separately. The results show that in single system, the adsorptions of between MPs for pollutants (MG and RhB) are more consistent with the pseudo-second-order kinetics and Freundlich isotherm model, the adsorption capacity of both MPs for MG is greater than that of RhB. The adsorption capacities of MG and RhB were 7.68 mg/g and 2.83 mg/g for PVC, 4.52 mg/g and 1.27 mg/g for PE. In the binary system, there exist competitive adsorption between MG and RhB on MPs. And the adsorption capacities of PVC for the two dyes are stronger than those of PE. This is attributed to the strong halogen-hydrogen bond between the two dyes and PVC, and the larger specific surface area of PVC. This study revealed the interaction and competitive adsorption mechanism between binary dyes and MPs, which is of great significance for understanding the interactions between dyes and MPs in the multi-component systems.

Study on the formation mechanism of hydrothermal prefabricated activated carbon and its adsorption capacity for malachite green

Study on the formation mechanism of hydrothermal prefabricated activated carbon and its adsorption capacity for malachite green

Zeolitic imidazolate framework (AMCD-ZIF) functionalised membrane for the removal of dyes from water

The chemical and thermal stability of zeolitic framework (ZIFs), in addition to the tunability of their functional groups renders them ideal candidates for water treatment applications. With the right functionality, ZIF particles can efficiently remove targeted contaminants from water. This, however, requires separating the particles from the suspension (through centrifugation or filtration) to recycle the ZIF particles after each treatment cycle. This time-consuming and costly process can be avoided by suspending the ZIF particles on solid support compatible with water treatment approaches. The design and preparation of a novel amine-carboxamide modified ZIF-8 (AMCD-ZIF) through the integration of mixed-linkers: 2-methylimidazole (MIM) and 4-amino-1H-imidazole-5-carboxamide (AMCD) in 1:1 ratio following a hydrothermal method, is reported in this study. Prepared and characterized AMCD-ZIF is used as a functionalizing agent to decorate the surface of electrospun polyvinyl chloride membranes (PVC-M). The functionalised electrospun membrane AMCD-ZIF/PVC-M is not only capable of microfiltration of aqueous molecules, due to the high porosity of the PVC-fibrous membrane, but also efficiently removing dyes from water due to the functionality introduced by the (AMCD-ZIF) at the surface of the membrane. Adsorption of aqueous organic dyes; malachite green (MG), methylene blue (MB), and direct blue 71 (DB) from water using the pristine AMCD-ZIF and membrane (AMCD-ZIF/PVC-M) were achieved. Both adsorbents resulted in the complete removal of aqueous MG in 30 min at ambient conditions and neutral pH. The adsorption capacity of MG is 2500 mg/g for AMCD-ZIF and 476 mg/g for AMCD-ZIF/PVC-M at ambient conditions. Adsorption efficiency of MG was maintained at approximately 100 % after six cycles of dye removal, without compromising the efficiency of the structure of AMCD-ZIF and AMCD-ZIF/PVC-M.

Enhanced adsorption of malachite green on hydroxyl functionalized coal: Behaviors and mechanisms

The discharge of untreated colored wastewater poses a severe threat to global health. This work reports a simple yet highly efficient way to modify Zhundong coal (MZD) with hydroxyl functional groups for malachite green (MG) removal. The modification significantly improved the adsorption capacity of MG from 63.0 mg/g to 538.7 mg/g. According to Fourier transform infrared spectroscopy, zeta-potential analyzer, X-ray photoelectron spectroscopy, and N2 absorption characterization, the improvement in adsorption capacity was mainly attributed to the enhancement of hydroxyl functional groups on the surface of coal. The adsorption of MG on MZD depended on pH, and the highest removal efficiency reached 99.7% at pH 10 with an initial MG concentration of 500 mg/L. The adsorption process was mainly controlled by chemisorption, and it was endothermic and spontaneous according to thermodynamic analysis. The adsorption data could be well reproduced by the pseudo-second order kinetic model and the Redlich-Peterson isotherm model. The MZD shows good regeneration performance with only a 16.9% reduction of initial adsorption capacity after five circles. Hydrophobic interactions, π-π interactions, and pore-filling contributed to adsorption, whereas electrostatic interactions played a dominant role in the MG removal by MZD. This work provides a new sight to prepare useful and cheap adsorbents from coal to remove contaminants from printing and dyeing wastewater.

Lignin-inspired porous polymer networks as high-performance adsorbents for the efficient removal of malachite green dye

Herein, a series of porous polymer networks (LPPNs) were prepared from sustainable lignin-derivatized aldehyde monomers. It was interesting to discover that the 4-hydroxy benzaldehyde (H type) was favorable to promote the formation of the porous network LPPN-H with the largest BET surface area (739.4 m2/g) and pore volume (1.78 cm3/g) over that of LPPN-G (G type) and LPPN-S (S type), emphasizing the various geometrical shapes of building blocks significantly affected the porosity properties. The porous networks and abundant functional groups of LPPNs enabled efficient and rapid adsorption of malachite green (MG) dye. Strongly depending on the porosity parameters, LPPN-H gave a higher adsorption capacity for MG (Qmax = 1449.8 mg/g) than LPPN-G and LPPN-S, which exceeded many other reported adsorbents. The adsorption process could be well described by the pseudo-second-order kinetic model and Langmuir isotherm model, respectively. Study in adsorption mechanism demonstrated that the electrostatic force, hydrogen bonding, and π-π stacking interactions existed in MG adsorption onto LPPNs. Besides, LPPN-H exhibited high stability and retained over 90% removal efficiency after 10 cycles. Together with the excellent adsorption behaviors and unique porosity properties, the low-cost and green LPPNs exhibited promising utilization in wastewater purification.

A novel surface-oxidized rigid carbon foam with hierarchical macro-nanoporous structure for efficient removal of malachite green and lead ion

This study developed a method to fabricate a surface-oxidized rigid carbon foam (ORCF) with hierarchical macro-nanoporous structure via KOH activation of the carbon foam with two kinds of macropores followed by HNO3 hydrothermal oxidation. The structures of the prepared ORCF were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy, and N2 adsorption-desorption analyzer. Results demonstrate that the ORCF possesses a fluffy and porous structure with rich oxygen-containing groups. There are numerous through-holes on its pore surfaces connected with two-level macropores forming hierarchical macroporous channels. Meanwhile, the ORCF remains a good bulk structure with a compression strength of 0.74 MPa at a bulk density of 0.09 g cm−3. Batch adsorption experiments for malachite green (MG) and Pb2+ were studied through the single variable method to investigate the effects of different initial conditions on its adsorption process. The ORCF has maximum adsorption capacities for MG and Pb2+ of 587.68 mg g−1 and 157.80 mg g−1 with high partition coefficients of 17.41 mg g−1 µM−1 and 14.86 mg g−1 µM−1, respectively. The experimental data are suitable for Langmuir isotherm and Pseudo-second-order kinetic models, which correspond to monolayer chemisorption. Thermodynamic analysis indicates that the adsorption process is spontaneous and endothermic. Moreover, the removal percentages of MG and Pb2+ by the ORCF could remain above 90% after five cycles, implying that the ORCF is an efficient adsorbent with good adsorption ability and cycling stability.