Adsorption Capacity For Malachite Green Research Articles

Polydopamine modified coconut shell biochar decorated with ZIF-8 for improved adsorption of malachite green and rhodamine B from aqueous solution.

Although various biochars from different biomass materials have been developed to remediate dye-contaminated environments, the removal capabilities of pristine biochar for dyes urgently require further enhancement due to insufficient surface adsorption sites. To introduce more adsorption sites, this work proposes a simple approach to fabricate coconut shell biochar (CSB) based adsorbent by anchoring zeolitic imidazolate framework-8 (ZIF-8) via the active sites provided by polydopamine (PDA)-coated CSB. The nucleation sites provided by the PDA layer promote the dispersion of ZIF-8 on the surface of CSB, resulting in sufficient adsorption sites for removing malachite green (MG) and rhodamine B (RB) from wastewater. The resulting CSB/PDA/ZIF-8 demonstrates a large specific surface area (749.54 m2∙g-1) and outstanding adsorption capacities for MG (1568 mg∙g-1) and RB (1496 mg∙g-1). Furthermore, CSB/PDA/ZIF-8 adsorbents can maintain a satisfactory removal rate for MG (91%) and RB (77%) even after five reuses. The analysis of the adsorption mechanism exhibits that electrostatic interactions, hydrogen bonds, coordination bonds, and π-π stacking are of significance for adsorbing MG and RB. Therefore, CSB/PDA/ZIF-8 is a promising candidate for dye wastewater treatment, while this work provides guidance for the high-quality utilization of biomass materials.

Preparation of Porous Novel QuEChERS Adsorbent ZIF‐67/PAA/PES Composite Microspheres and Their Application for Rapid Adsorption of Triphenylmethane Dyes in Wastewater and Fish

ABSTRACTTriphenylmethane dyes have a wide range of applications in textiles, pharmaceuticals, food, and other fields. Malachite green (MG), fuchsin acid (FA), and crystalline violet (CV) were typical representatives of triphenylmethane dyes, and they are carcinogenic and mutagenic to aquatic organisms and environment. However, they need to be separated and enriched for their accurate quantification due to their low content. Therefore, it is important to develop a rapid and accurate enrichment method to monitor these dyes in aquatic systems for human health. In this paper, a novel QuEChERS adsorbent porous ZIF67/PAA/PES composite microspheres were prepared and applied for the rapid adsorption of triphenylmethane dyes in wastewater and fish samples, which improved the adsorption capacity and the analytical sensitivity of the targets. The experimental results demonstrated that the porous ZIF‐67/PAA/PES composite microspheres exhibited excellent selective adsorption capacity of MG, FA, and CV, and after six adsorption–desorption cycles, the material adsorption amount can reach more than 90% of its original adsorption amount in wastewater. In addition, the porous ZIF67/PAA/PES composite microspheres were applied as QuEChERS adsorbents for the enrichment of MG and CV dyes in fish, and the adsorption rates of the dyes were 99.11% and 99.03%, with the RSDs of 1.58% and 1.27%, respectively. The limits of detection were 0.0093 and 0.0127 mg/L for MG and CV. Through the Langmuir adsorption isotherm models to predict the MG, FA, and CV of the maximum adsorption capacity were 5417.3622, 2119.9011, and 1654.1026 mg/g, respectively. Thus, the novel porous ZIF67/PAA/PES composite microspheres are more advantageous as QuEChERS adsorbents for sample pre‐treatment and have very important research significance.

Highly efficient malachite green adsorption by bacterial cellulose and bacterial cellulose/locust bean gum composite

In this study, bacterial cellulose (BC) and BC/locust bean gum (LBG) composite produced from banana hydrolysate were both used as the adsorbent for various organic dyes adsorption especially for malachite green (MG) adsorption for the first time. The BC/LBG(2%) composite exhibited significantly enhanced swelling rate and textural characteristics while maintained the basic structure of BC as depicted by XRD, FT-IR, and NMR, providing a foundation for its application as an excellent adsorbent. The composite exhibited a high adsorption rate and adsorption capacity for MG (exceeding 95 % and 2000 mg/g), and had a good selectivity for MG adsorption in the solution containing crystal violet (CV), rhodamine B (RB), and methyl orange (MO). The MG adsorption process conformed to multiple models including Langmuir and pseudo-first-order models. And the adsorption mechanism mainly comprised chemical adsorption (hydrogen bonding and electrostatic interactions) and physical adsorption. The reusability of BC/LBG(2%) composite was attractive for industrial application that the MG adsorption rate reduced merely a little (still higher than 88 %) after the 5th regeneration process. Overall, considering its adsorption capacity, selectivity, and reusability, BC/LBG(2%) composite prepared by in-situ fermentation with LBG addition was a competent adsorbent for MG adsorption and MG containing wastewater treatment.

N-doped lignin-based activated carbon aerogel derived from bamboo black pulp liquor for efficient removal of malachite green in wastewater.

In this study, a lignin-based aerogel (LA) was prepared through acid precipitation of BPBL, followed by sol-gel method and freeze-drying. Additionally, a one-step activation-carbonization method was used to acquire nitrogen-doped lignin-based activated carbon aerogel (NLACA). The adsorption and catalytic degradation performance for malachite green (MG) were examined. The specific surface area of NLACA after N-doping was 2644.5 m2/g. The adsorption capacity for MG was increased to 3433mg/g with the presence of nitrogenous functional groups on surface of NLACA compared without N-doping. Meanwhile, non-radical singlet oxygen is the primary active substance and degradation efficiency arrives at 91.8% after the catalytic degradation within 20min and it has good stability and reuse. Three possible degradation pathways during degradation were analyzed by LC-MS technique. The adsorption isotherm and kinetic data demonstrated conformity with both the Langmuir model and the pseudo-second-order kinetic model. The primary mechanisms of the adsorption for MG dyes on NLACA include hydrogen bonding, π-π interactions, attraction of electrostatic and pore filling. Hence, NLACA derived from BPBL acts as a cost-effective and high-performance adsorbent and catalyst for removal of MG in dye wastewater. This concept introduces an innovative approach of "treatment of waste with waste" for developing a low-consumption, high-efficiency dye wastewater treatment and provides significant reference to treatment dye wastewater.

Adsorption-desorption behavior of malachite green on aged microplastics in seawater environment

The role of microplastics (MPs) as carriers of contaminants in the water environment is an emerging concern, significantly impacting migration and transformation. This study aims to compare the adsorption behavior of MPs with Malachite green (MG) dye before and after simulated short-term seawater aging (especially during the initial phase of the aging process) and to analyze in-depth the mechanism by which the aging process influences adsorption behavior. Results showed that after aging, the adsorption capacities of Polypropylene (PP), Polyethylene terephthalate (PET), and Polyethylene (PE) for MG were 2.58, 2.43, and 1.59 mg g−1, respectively. The adsorption capacity of other MPs for MG increased significantly, except for PE, which remained nearly unchanged. Calcium chloride (CaCl2) plays a significant role in the seawater aging process, and increasing the concentration of CaCl2 leads to a decrease in the adsorption amount of MG. Additionally, the adsorption capacity for MG varies significantly across different particle sizes and types of MPs, as well as the adsorption capacity of PP for different dyes. The Langmuir and Freundlich models indicate that the adsorption aligns more with the Freundlich model, which suggests that adsorption primarily occurs as multi-layer adsorption on a non-homogeneous surface. These results provide a scientific foundation for evaluating the ecological and environmental risks when MPs and organic dyes coexist. We also propose a novel approach of “treating waste dye with MPs” to mitigate their pollution in the aquatic environment.

Nano clinoptilolite zeolite as a sustainable adsorbent for dyes removal: Adsorption and computational mechanistic studies

Clinoptilolite, a naturally occurring zeolite with unique adsorption properties, is investigated in its nanoscale form as a sustainable adsorbent for effectively removing contaminant dyes, rhodamine B (RhB), malachite green (MG), and methyl green (MeG), from aqueous solutions. The nano clinoptilolite was prepared by ball milling and characterized using various techniques including XRD, FTIR, SEM, TGA, BET, and zeta potential to confirm its structure, functional groups, porous morphology, thermal stability, surface area and pore size distribution, and surface charge, respectively. The nano clinoptilolite has a crystalline size of 19.5 nm, determined by XRD. Its average hydrodynamic size in water is 285 nm, measured by dynamic light scattering. Adsorption experiments were carried out to evaluate the dye removal efficiency under various conditions such as pH, zeolite dose, dye concentrations, and contact time. The equilibrium adsorption data were fitted with different isotherm models such as Freundlich, Langmuir, Langmuir-Freundlich, and Sips; and the kinetics adsorption data were fitted with pseudo-first-order, pseudo-second-order, mixed-order, and Avrami models. Nanosized clinoptilolite exhibited a high maximum adsorption capacity for MG (191.36 mg MG/g at pH 5.0), exceeding a previous report by 336 % (43.86 mg MG/g). RhB adsorption capacity on zeolite was 58.02, 24.28 mg/g at pH 3.0, 7.0, and MeG was 162.94 mg/g at pH 7.0. Finally, Monte Carlo and molecular dynamics simulations were used to elucidate the specific binding sites, adsorption energies, and mechanisms involved in the removal process.

Removal of malachite green by in-situ N-doped biochar derived from wheat bran: kinetics, isotherms, and adsorption mechanism study

The biomass-based adsorbents offer a promising solution for wastewater decolorization owing to their superior specific surface area, low-budget, high adsorption capacities, and environmental sustainability. In this work, wheat bran (WB) was used as raw material for the production of in situ N-doped biochar through a molten salt template method, and the adsorption characteristics of Malachite Green (MG) onto biochars prepared from WB by immersing and non-immersing (BC–NaK and BC–NaK-n) in the mixed salt solution (NaCl and KCl) were investigated. The experimental results indicated that the adsorption capacity of MG onto the BC–NaK was significantly better than BC–NaK-n, which was attributed to the rich functional groups and well-developed pore structure of BC–NaK. The adsorption equilibrium data of MG onto the BC–NaK was fitted well to Sips and Koble-Corrigan isotherm models and adsorption process of MG was spontaneous and endothermic. Meanwhile, the pseudo-second-order model was successfully applied to depict the adsorption process of MG. Furthermore, the adsorption of MG onto BC–NaK was primarily regulated by H-bonding, π–π interaction, hydrophobic interaction, electrostatic interaction. The maximum saturated adsorption capacity of the BC–NaK was 880.14 ± 9.35 mg g−1 at 298 K, further demonstrating that biochar prepared from wheat bran provided a long-term development strategy for dye wastewater treatment.

Hollow ZIF-8 nanomaterial prepared via core-shell etching exhibits exceptional adsorption performance for malachite green

Metal-organic frameworks (MOFs) have attracted widespread attention due to their distinctive structural attributes, such as expansive surface areas and the ease of chemical modification. These characteristics endow MOFs with a high degree of versatility, making them suitable for a broad array of applications. Core-shell MOF@MOF structures have emerged as a notable research area, offering a strategy to enhance MOF functionality by depositing one MOF layer over another. In this study, hollow ZIF-8 nanocomposites were successfully synthesized via the etching process of ZIF-67@ZIF-8 structures. It is noteworthy that the nanomaterial exhibits exceptional adsorption capacity, with a maximum adsorption capacity of 7746 mg/g for malachite green (MG), surpassing that of many previously reported adsorbents. Moreover, the recyclability of these nanocomposites is also excellent, demonstrating sustained effectiveness over five adsorption-desorption cycles. The study systematically investigated key factors that influence MG adsorption, such as the amount of adsorbent used and the initial concentration of MG. Additionally, a comprehensive analysis of adsorption kinetics was conducted to gain insights into the adsorption behavior of the nanocomposites. In conclusion, the hollow ZIF-8 nanomaterial prepared via core-shell etching offers a promising platform for the efficient removal of MG, meeting the urgent demand for high adsorption capacity of MG in water treatment.

A sustainable, eco-friendly Tb/Eu-modified HOFs for ultrasensitive detection and efficient adsorption of carcinogens in complex water environments

Developing a multifunctional material that can detect and remove carcinogens in water environments, simultaneously monitor their toxic metabolites in living organisms is significant for environmental remediation and human health. However, most research only focused on detection or adsorption carcinogens due to the difficulty of integrating multiple functions into one material, let alone monitoring their toxic metabolites. Here, a multifunctional Tb/Eu@TATB-HOF (1) is first developed to monitor two carcinogens, malachite green (MG) and its metabolites leucomalachite green (LMG), and simultaneously remove MG from the contaminated water. 1, as the dual-emission fluorescence sensor, can achieve ultrasensitive and highly visualized sensing for MG and LMG with different response modes. Even in actual samples, 1 still exhibits satisfactory sensing performances. As the adsorbent, 1 displays good recyclability and high adsorption capacity for MG. The sensing and adsorption mechanisms are explored through experiments and theoretical calculations. This work not only provides a novel insight for environmental remediation and human health through detection and removal of carcinogens, simultaneously monitoring their toxic metabolites, but first reveals the enormous potential of HOFs as multifunctional materials simultaneously for fluorescence sensing and adsorption.

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.