Malachite Green Adsorption Research Articles

Green synthesis of ZnFe2O4 nanoparticles using Chrysanthemum spp. flower extract for the adsorption and photocatalytic degradation of malachite green dye

AbstractBACKGROUNDNowadays, the large amount of organic textile dyes being regularly consumed also releases hazardous residues into water sources. Nanotechnology can solve part of this problem by using nanoparticles as adsorbents and catalysts for the removal of dyes from water. The present study explored the facile and green synthesis of ZnFe2O4 nanoparticles using Chrysanthemum spp. flower‐mediated extract (ZFOB) as a reducing and capping agent for the removal of cationic malachite green (MG). ZFOB nanoparticles were characterized by various techniques, such as X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy.RESULTSThe average particle size and Brunauer‐Emmett‐Teller (BET) surface area of ZFOB were found to be 60–80 nm and 10.9 m2/g, respectively. The pore size distribution indicated a characteristic of meso‐macropores of the biosynthesized ZFOB nanoparticles. The MG adsorption of the green ZFOB nanoparticles was investigated under batch mode through the effect of various parameters, including contact time (0–60 min), initial concentration (5–100 mg/L), pH (4.0–10.0), and adsorbent dosage (0.25–1.0 g/L). The adsorption process followed the Elovich kinetic model, () = 0.9992, while the adsorption behavior can be described by Koble‐Corrigan, () = 0.9915. Meanwhile, the maximum adsorption capacity was 121.2 mg/g from the Langmuir model at a contact time of 30 min, dosage of 0.5 g/L, and pH 7. Green ZFOB nanoparticles showed a good photocatalytic activity (80.4%) under solar light irradiation and they were able to be recycled up to four times while retaining their high stability.CONCLUSIONZnFe2O4 nanoparticles biosynthesized using Chrysanthemum spp. flower extract can be a good adsorbent and photocatalyst for the removal of MG dye. © 2022 Society of Chemical Industry (SCI).

Pd-ZnO nanoparticles decorated acid activated montmorillonite for the efficient removal of cationic dyes from water

Efficient adsorbent being the need of the hour for the effective removal of dye stuff from textile effluents, we herein report the synthesis of palladium intercalated zinc oxide nanoparticles decorated acid activated montmorillonite (Pd-ZnO@H+-Mt)nanocomposite using ion-exchange process followed by wet impregnation technique with Citrus limon leaf extract as reducing agent and its application as an efficient adsorbent for methylene blue (MB) and malachite green (MG) removal from water. The successful intercalation of Pd into the ZnO lattice was identified by band gap value calculated using UV-DR spectra. ATR FT-IR, XRD, SEM, TEM, TGA, BET, and XPS techniques confirmed the successful preparation of Pd-ZnO@H+-Mt nanocomposite. The synthesized Pd-ZnO@H+-Mt nanocomposite was then evaluated for efficient uptake of cationic dyes through batch adsorption experiments and thereby various parameters that influenced adsorption process were found. The experimental maximum adsorption capacity, qm of Pd-ZnO@H+-Mt for MB and MG dyes were 205 and 167 mg/g. The main driving force for the adsorption of MB and MG was identified to be the presence of mesopores, high specific area of Pd-ZnO@H+-Mt on acid activation, total pore volume and the presence of Pd-ZnO NPs on the surface which enhanced the negative charges of Mt surface thus facilitated better loading of dye molecules. Multilayer coverage of MB/MG molecules on Pd-ZnO@H+-Mt were evidenced through Freundlich isotherm model and experimental data of both MB and MG were described well by pseudo second-order kinetic model. The adsorption phenomenon was identified as feasible, spontaneous, and endothermic for MB adsorption while exothermic for MG adsorption. Moreover, the adsorbent could be recycled thrice. Thus, the synthesized Pd-ZnO@H+-Mt nanocomposite could be utilized effectively in industrial water treatment for the removal of dye stuff as adsorbent.

Micron sized anionic poly (methacrylic acid) microgel particles for the adsorptive elimination of cationic water pollutants

Abstract In this article, we reported the micron sized particles of poly (methacrylic acid) (p [MAA]) microgel and explored their applications as anionic adsorbents. The micron sized particles of poly (methacrylic acid) microgel were prepared by a simple inverse suspension polymerization method. The adsorptive elimination of adsorbates of cationic nature including malachite green (MG) and methylene blue (MB) from the aqueous medium was studied systematically. The adsorption tests were carried out using various initial concentrations of dyes and with different amounts of adsorbents. The adsorption equilibrium was established in 60 min. The adsorption capacity of the p (MAA) microgel was found as high as 351 mg/g for MG and 65 mg/g for MB. The maximum removal percentage for MG and MB was recorded as 88 and 68%, respectively. The adsorption data was computed with adsorption isotherm models including Langmuir, Freundlich, and Temkin. The Langmuir model was observed to be more applicable for the adsorption of MG while the adsorption of MB was best matched with Temkin model. The adsorption data was also treated with pseudo first order and pseudo second order kinetic models along with intraparticle diffusion and Elovich models. The pseudo second order kinetic model was most suitable with adsorption of both the MG and MB.

Malachite Green Adsorption Using Carbon-Based and Non-Conventional Adsorbent Made from Biowaste and Biomass: A Review

Malachite Green Adsorption Using Carbon-Based and Non-Conventional Adsorbent Made from Biowaste and Biomass: A Review

Integrated Adsorption and Photocatalytic Degradation of Malachite Green Using Carbon Based Nanocomposites (ZnO-AC)

Malachite green dye is widely used in dye industries, aquaculture industries and food industries. The prevalence of this malachite green in the effluent of wastewater could potentially harm human health and destroy the aquatic system. Hence, to completely destroy its presence in the effluent, a technique of integrated adsorption and photocatalytic degradation was introduced. Integrated photocatalyst adsorbent (IPCA) utilizing zinc oxide as photocatalyst and supported on activated carbon derived from melinjo shell, ZnO-AC was synthesized. Activated carbon derived from the melinjo shell provides a porous surface for adsorption while zinc oxide is sensitive to photons and enhances better light absorption. ZnO-AC was subjected to scanning electron microscope (SEM) and Fourier Transform infrared spectroscopy (FTIR) characterization. The analysis revealed a porous sponge network and an intense peak of zinc oxide at 650-700 cm−1. The performance of ZnO-AC was evaluated by studying the effect of initial dye concentration (10-50 ppm), pH (2-11) and ZnO-AC dosage (5-25 mg) in the presence of UV light. In this study, the optimum conditions for dye degradation were found to be 10 ppm initial dye concentration, pH 11 and 15 mg ZnO-AC dosage. Kinetic behaviour of the dye degradation was also investigated. The photocatalytic degradation followed Langmuir-Hinshelwood model and the data corresponded well with pseudo-first-order kinetics.

Linear and nonlinear modeling of kinetics and isotherm of malachite green dye adsorption to trimellitic-modified pineapple peel

Adsorption is known for toxic dye removal in water, which can utilize a plant-based material to make a low cost and sustainable adsorbent. This study addresses the issue of preparing a cellulose-based adsorbent that is catered to cationic dye property and address inaccurate data interpretation and parameter estimation errors in adsorption analysis. The objective of this research is to overcome these challenges by modifying the surface of cellulose with carboxyl and utilizing original nonlinear equations with errors evaluation within the applied models to interpret the adsorption. In this paper, the pineapple peel cellulose will be reacted with 1,2,4–benzene tricarboxylic acid for malachite green adsorption. Characterization results showed a peak of C = O at 1712 cm−1, confirming the success of the modification. Through analyzing lowest sum of normalized error in linear and nonlinear model fitting, the best fit was obtained from the nonlinear Sips isotherm, with qm = 51.3 mg g−1, KS = 0.016 L/g, and 1/n = 2.0, as well as PSO kinetics k2 = 0.0142 g mg−1 min−1, qe = 24.8 mg g−1 which suggest that the modification of cellulose promotes collaborative adsorption, a mixing mechanism for MG dye adsorption.

Synthesis and characterization of MOF-5 incorporated waste-derived siliceous materials for the removal of malachite green dye from aqueous solution

The synthesis of MOF-5 and its modification have been investigated towards malachite green (MG) dye removal. The modified MOF-5 adsorbents have been prepared using waste-derived siliceous materials, i.e., rice husk ash (RHA) and/or coal fly ash (CFA) at different ratio. The MOF-5/RHA&CFA/2:1 has been chosen as the best adsorbent for MG dye removal from the aqueous solutions. The adsorption characteristics of the modified MOF-5 for MG dye removal was studied varying various parameters. The MG adsorption efficiency increases with increasing the shaking rate and contact time, but remained constant after 300 rpm and 4 h, respectively. The maximum adsorption capacity of 39.47 mg/g was obtained at adsorbent amount of 0.3 g, initial dye concentration of 150 mg/L, temperature of 30 °C, shaking rate of 200 rpm, contact time of 2 h, and original solution pH. The optimum temperature, pH, and amount of adsorbent for effective MG dye adsorption were 40 °C, 11.5, and 0.2 g, respectively. XRD analysis indicated the presence of crystalline materials has become reduced when RHA and CFA were being incorporated in MOF-5. FTIR analysis showed significant functional groups in the spectrum for both prepared and spent adsorbents. The SEM micrograph results revealed the rough surface morphology with many pores on the MOF-5/RHA&CFA/2:1 before MG adsorption and became smooth and less porous after MG adsorption. While BET analysis indicated that the surface area does not affect the MG dye adsorption efficiency. This study showed that modified MOF-5 adsorbents were successfully used for the removal of MG dye.

Comparative Adsorption Behavior of Malachite Green Dye onto Charred and Aminated Sal (Shorea robusta) Sawdust from Aqueous Solution

Chemically treated Sal sawdust was used to study the adsorption of Malachite Green (MG) dye from an aqueous solution. Raw Sal sawdust (RSSD) was charred and aminated. The surface functional groups of raw and modified adsorbents were determined by Fourier Transform Infrared Spectra (FTIR). The influence of pH on batch experiments, concentration and contact time for charred Sal sawdust (CSSD) and aminated Sal sawdust (ASSD) were investigated. The dye uptake was highest at a pH of 4, and adsorption was found to be 62.63 % and 92.15% for CSSD and ASSD, respectively, at an adsorbent dose of 0.025 g and agitation speed of 190 rotations per minute (rpm). The pertinency of Langmuir isotherm was tested, and the kinetic data was found best fitted for pseudo-second-order. The adsorption capacity of MG dye onto ASSD and CSSD was found to be 91.9 mg/g and 64 mg/g, correspondingly. This showed that ASSD is a more efficient adsorbent than CSSD for excluding MG dye from an aqueous solution.

Removal of Cationic Dyes by Iron Modified Silica/Polyurethane Composite: Kinetic, Isotherm and Thermodynamic Analyses, and Regeneration via Advanced Oxidation Process.

Emerging dye pollution from textile industrial effluents is becoming more challenging for researchers worldwide. The contamination of water by dye effluents affects the living organisms in an ecosystem. Methylene blue (MB) and malachite green (MG) are soluble dyes with a high colour intensity even at low concentration and are hazardous to living organisms. The adsorption method is used in most wastewater plants for the removal of organic pollutants as it is cost-effective, has a high adsorption capacity, and good mechanical stabilities. In this study, a composite adsorbent was prepared by impregnating iron modified silica (FMS) onto polyurethane (PU) foam to produce an iron modified silica/polyurethane (FMS/PU) composite. The composite adsorbent was utilised in batch adsorption of the cationic dyes MB and MG. The effect of adsorption parameters such as the adsorbent load, pH, initial dye concentration, and contact time were discussed. Adsorption kinetics and isotherm were implemented to understand the adsorption mechanism for both dyes. It was found that the adsorption of MB and MG followed the pseudo-second order model. The Langmuir model showed a better fit than the Freundlich model for the adsorption of MB and MG, indicating that the adsorption occurred via the monolayer adsorption system. The maximum adsorption capacity of the FMS/PU obtained for MB was 31.7 mg/g, while for MG, it was 34.3 mg/g. The thermodynamic study revealed that the adsorption of MB and MG were exothermic and spontaneous at room temperature. In addition, the regeneration of FMS/PU was conducted to investigate the composite efficiency in adsorbing dyes for several cycles. The results showed that the FMS/PU composite could be regenerated up to four times when the regeneration efficiency dropped drastically to less than 20.0%. The impregnation of FMS onto PU foam also minimised the adsorbent loss into the environment.

Excellent catalytic performance of mechanically alloyed AlCrFeMnTiZr0.5 high-entropy alloy for malachite green degradation

• AlCrFeMnTiZr 0.5 HEA powder photocatalyst is prepared by mechanical alloying. • AlCrFeMnTiZr 0.5 catalyst exhibits good malachite green degradation under light. • Nano-reactants are mainly oxides or hydroxides of Al and Mn after catalysis. • Nanoparticles and nanosheets covering surface promote adsorption and degradation of MG. • Exfoliated nano-reactants and exposed fresh surface enhance degradation reusability. This work reports that the mechanical alloyed AlFeMnCrTiZr 0.5 high-entropy alloy (HEA) powder was used as catalyst for malachite green (MG) degradation. The HEA with dual solid solutions shows good catalytic performance under visible light. Its efficiency of reaching degradation saturation and maximum degradation rate are much greater than those of Fe 0 powder. The oxides or hydroxides of Al and Mn nucleate and grow on the powder surface, existing in the form of initial nanoparticles and growing nanosheets, which promote the adsorption and catalytic degradation of MG. The exfoliated nano-reactants and exposed fresh powder surface of catalyst enhance the reusability and sustainability of degradation. The catalytic mechanism is mainly visualized by the synergy of chemical dye decomposition and physical dye adsorption.

Application of imino diacetate functionalized poly (methyl methacrylate) in a portable syringe system for the removal of malachite green from different water system

A novel solid phase microextraction in a portable syringe system (SPME-PSS) was developed for removal of malachite green (MG) by using UV-Vis spectrometric determination. A long narrow column (100 cm × 5 mm i.d.) of having 10 mg of iminodiacetate functionalized polymethyl methacrylate (PMMA-ida) connected with a syringe system as an adsorbent medium to enhanced the contact area two medium (solid and liquid), which significantly increase adsorption of MG from aqueous medium to adsorbent. The surface morphology of PMMA-ida was characterized by FT-IR, 1H NMR, DSC and SEM techniques. The adsorption behavior of MG toward PMMA-ida was carried out by applying kinetic, thermodynamics and isotherms studies. The Langmuir and Freundlich's isotherms were used to point out the adsorption mechanism and the adsorption capability of the PMMA-ida. The monolayer adsorption capacity (qmax) of MG toward PMMA-ida was found to be 250.5 mg/g for MG. The proposed adsorbent could be recycled 10 (adsorption/desorption cycles) successfully without any decrease of regeneration capability. The kinetic study was also carried out and found that a higher R2 and good qe values shows the reaction follows pseudo-second-order kinetic. The adsorption was further conformed to be favorable from the Kf and 1/n values (1/n>0.1). The ∆G° (-6.762678) predict that the reaction is spontaneous and viable and the ∆H° (5.33315298) values show that reaction should be endothermic, whereas ∆S° (25.0018608) values show randomness adsorption behavior. We used a multivariate optimization approach for the optimization of extraction parameters. We also centroid simplex mixture of the mixture design to point out the best elution solvent of desorption cycles. The CCD of the response surface method was used to elevate the key factors (pH, final amount of PMMA-ida and (adsorption/desorption cycle). The analytical capability was also checked and found to be a linear response with (r) ≥ 0.9976 at a concentration range 10–100 ng L−1. LOD and RSD values were found 0.055 µg L−1 and 4.1 %. The spiking addition method was used to check the validity of the SPME-PSS method. The SPME-PSS method was successfully applied to water samples for the determination of MG.

Thermodynamic and kinetic studies for the adsorption of malachite green on diatomite

Pollution by dyes is one of the main pollutions of industrial effluents. This research examined Moroccan diatomite as a low-cost adsorbent to remove one of the dangerous dyes, malachite green (MG). Brunauer–Emmett–Teller analysis, scanning electron microscopy, pHpzc and X-ray diffraction were used to characterise diatomite. The studies were carried out at different levels of pH, diatomite masses and MG concentrations at a temperature of 25°C. Equilibrium, kinetics and thermodynamic characteristics were also studied. The results show that the diatomite consisted of an integrated and nearly circular sieve plate with many small ordered pores, giving it a high specific surface area of 17.36 m2/g. The ideal pH was found to be 7, with a saturation period of 90 min. The results indicate that MG removal increased accordingly as the pH increased and also as the adsorbent mass increased. The results of the isotherms showed that the Langmuir model is the most adequate, while the adsorption of MG is better characterised as monolayer adsorption. The maximum adsorption capacity obtained from the Langmuir model is about 22.17 mg/g at 25°C. Kinetic studies indicated the pseudo-second-order model as the most adequate model. It was also revealed that intraparticle diffusion is not the only rate-controlling step. From the thermodynamic data, it was concluded that the adsorption is endothermic – that is, the adsorption is more favourable at high temperatures. The research confirmed the applicability of diatomite as an effective and inexpensive adsorbent for removing hazardous materials.

Fabrication of nano-biocomposite for the removal of Eriochrome Black T and malachite green from aqueous solution: isotherm and kinetic studies.

The increasing generation of toxic dye wastewater from various enterprises continues to be a serious public health issue and happens to be of environmental concern, posing a significant challenge to existing conventional water treatment facilities. Malachite green (MG) and Eriochrome Black T (EBT) are extremely hazardous and carcinogenic substances; hence it is crucial to remove them from water bodies. A well-known cleaner, more economical, and environmentally friendly treatment method is adsorption. The kind of adsorbent material employed determines how well the treatment procedure works. A physiologically compatible nanocomposite adsorbent (HAP@CT@MNP) was fabricated from laboratory synthesized hydroxyapatite (HAP) and magnetite (MNP) for its application in the wastewater remediation process. The ability of the fabricated nanocomposite to remove the harmful dyes EBT and MG from a simulated wastewater was evaluated. The impact of operational parameters including pH, adsorbate concentration, adsorbent dose, contact time, and temperature was examined to gauge the maximum adsorption capacity of the developed nanocomposite. The optimum pH for the eradication of EBT and MG were found to be 3 and 7.4, respectively. The maximum capacity evaluated was 222mg/g and 500mg/g at room temperature and at contact time of 50 and 40min respectively. The binding of either EBT or MG followed the monolayer Langmuir model and kinetic studies revealed the suitability of pseudo-second-order model. Studies using spectroscopy and isotherm modeling showed that the main mechanism controlling the adsorption of EBT and MG onto HAP@CT@MNP is physisorption. The efficacy of the adsorbent to be reused with 8% loss in its efficiency reveals the economic viability of HAP@CT@MNP. The current work showed that a biocompatible nanocomposite could be successfully fabricated and used as an enhanced adsorbent for the quick and effective removal of the toxic dyes EBT and MG from wastewater.

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.

Adsorption-degradation of malachite green using alkali-modified biochar immobilized laccase under multi-methods

• Laccase was immobilized onto A-MB via multi-immobilization methods. • The adsorption of MG on A-MB followed the pseudo-second-order equation. • The adsorption of MG on A-MB followed the Langmuir isotherm model. • A-MB possessed a relatively high q max (757.58 mg/g) for MG. • The maximum removal rate of immobilized laccases was high than 97.70 %. Malachite green (MG) is an environmental persistent pollutant. The excellent adsorption capacity and enzyme carrier potential of alkali modified biochar (A-MB) are potential solutions for the treatment of MG. In this paper, laccase was immobilized onto A-MB via multi-immobilization methods. The batch adsorption equilibrium experiments were conducted to study the adsorption behavior of MG on carrier A-MB. The results showed that the adsorption of MG on A-MB followed the pseudo-second-order equation and the Langmuir isotherm model. In addition, A-MB possessed a relatively high q max (757.58 mg/g) for MG. The comparative experiment was set up to compare the removal rate of MG on free laccase (FL) and immobilized laccase (adsorption method: A/lac@A-MB; adsorption-crosslinking method: A-C/lac@A-MB; covalent binding method: CB/lac@A-MB), the maximum removal rate of FL was 89.68 %, but the maximum removal rate of A/lac@A-MB, A-C/lac@A-MB and CB/lac@A-MB was 97.70 %, 98.77 % and 97.86 %, respectively.

Preparation of konjac glucomannan/ZIF-67 hybrid aerogel and its adsorption properties for malachite green

Konjac glucomannan/zeolitic imidazole framework-67 (KGM/ZIF-67) hybrid aerogels were prepared as novel adsorbents to remove malachite green (MG) from aqueous solutions. The impacts of adsorption temperature, solution pH, and ionic strength on adsorption capacity were investigated. The results show that ZIF-67 coordinates with the molecular chain of KGM and modifies the KGM aerogel. The adsorption equilibrium time of KZ2 for MG is 150 min. The adsorption process follows the pseudo-second-order and Langmuir models, with a maximum adsorption capacity of 2891.30 mg·g−1 at 30 ℃. MG adsorption using the hybrid aerogels is a spontaneous and endothermic process. This research shows that hybrid aerogels prepared using KGM and ZIF-67 are promising for use in new water purification applications.

Hydrogels Based on Polyacrylamide and Functionalized Carbon Nanomaterials for Adsorption of a Cationic Dye

Malachite green (MG) is used for the dyeing of cotton, paper, and jute, among other materials, and presents acute toxicity to a wide range of aquatic and terrestrial animals. A polyacrylamide (PA) hydrogel modified with a low content of oxygenated and aminated carbon nanomaterials may be a suitable candidate to adsorb MG from wastewater. Herein, graphene oxide and carbon nanotubes (CNTs) were incorporated during the in situ polymerization of PA. The hydrogels were characterized through thermogravimetry, differential scanning calorimetry and infrared spectroscopy as well as imagined by scanning electron microscopy. The swelling and adsorption capacity were investigated to explore the influences of different carbon dimensionalities (1D and 2D), zeta potentials and nanofiller concentrations on the adsorption behavior of the hydrogel. There was an increase of approximately 1500% in the adsorption capacity after 24 h of exposure of a hydrogel with graphene oxide (GO) at 0.25 wt% with respect to the neat PA. Aminated graphene produced similar gains in the adsorption capacity of the GO-hydrogel, although it presents a positive zeta potential that is the opposite of that of GO. The modified CNTs showed smaller gains in the adsorption capacity, reaching a maximum 400% increase with respect to the PA hydrogel. The main factors that seem to affect the adsorption capacity were the dimensionality and degree of functionalization. The graphene oxide-based nanofillers were 3 to 4 times more functionalized than the nanotubes. The adsorption results were adjusted with a pseudo-second order kinetic model that allowed a complementary discussion about the nature of the physico-chemical effects on the process of MG adsorption in the hydrogel nanocomposites.

Beta-cyclodextrin carbon microspheres by hydrothermal carbonization for malachite green adsorption

This work was aimed at evaluating the adsorption characteristics of beta-cyclodextrin (β-CD) chars. Char was prepared by pyrolysis in a furnace at 550 °C, while spherical hydrochar was obtained through hydrothermal carbonization in a Teflon autoclave at 180 °C. Both chars are water-insoluble and were prepared without cross-linking agents. They were characterized for functional groups, thermal degradation, and surface morphology. The applicability of chars in adsorption was studied using malachite green solution at varying concentrations, contact times and temperatures. Hydrochar exhibits a better malachite green capacity of 18 mg/g. The adsorption rate and equilibrium data fitted well into pseudo-first-order and pseudo-second-order kinetics, and Langmuir and Dubinin–Radushkevich models, respectively. The thermodynamic parameters suggested that the removal process is spontaneous and endothermic in nature.

The Synthesis of Metal–Organic-Framework-Based Ternary Nanocomposite for the Adsorption of Organic Dyes from Aqueous Solutions

In the present study, a ternary magnetic nanocomposite (SiO2/MnFe2O4/ZIF-8) was synthesized via the embedding of the SiO2/MnFe2O4 nanocomposite within the metal–organic framework (ZIF-8). The synthesized nanocomposite was characterized using suitable techniques including FT-IR, XRD, SEM, TEM, VSM, and BET. The nanocomposite showed a high surface area (SBET = 831 m2·g−1) and superparamagnetic behavior (23.7 emu·g−1). All characterization techniques confirmed the successful combination of three nanocomposite parts (MnFe2O4, SiO2, and ZIF-8). The nanocomposite was examined for the adsorption of organic dyes, malachite green (MG) and methyl red (MR), from aqueous solutions. The adsorption conditions including ionic strength, contact time, pH, and adsorbent dosage were optimized by studying their change effect. The SiO2/MnFe2O4/ZIF-8 nanocomposite showed high adsorption capacities (1000.03 and 1111.12 mg/g) for the removal of MG and MR, respectively, from water. The isotherm and kinetics studies indicated that the adsorption of MG and MR dyes on the surface of the SiO2/MnFe2O4/ZIF-8 nanocomposite followed the Langmuir isotherm model and pseudo-second-order kinetic model, suggesting the monolayer chemisorption mechanism. The reusability study of up to five successive cycles indicated the successful reuse of the SiO2/MnFe2O4/ZIF-8 adsorbent for dye removal from wastewater. The comparison of the present adsorbent to the previously reported adsorbents indicated that it is a promising adsorbent for dye adsorption from wastewater and must be investigated in the future for the removal of additional pollutants.

Facile and scalable synthesis of mesoporous composite materials from coal gasification fine slag for enhanced adsorption of malachite green

The recycling of the solid wastes produced in the industrial process and converting them into functional materials with unique structures are of great significance for the sustainable development of human society. In this study, a facile and scalable synthesis method was designed for the preparation of mesoporous composite materials from waste coal gasification fine slag using K2CO3 as a mild chemical additive to chemically recombine SiO2 and Al2O3. At a fine slag to K2CO3 mass ratio of 1:1, a mesoporous composite material (OMB-KB) mainly composed of faujasite-Na and amicite was obtained, which possessed a uniformly porous and loose structure with a specific surface area of 40.26 m2/g and the pore size range of 2–50 nm. Metals inherited from the raw slag and various chemical groups existed on the surface of OMB-KB, making the materials have unique surface chemical properties. OMB-KB exhibited ultra-high adsorption performance on malachite green (MG), and the adsorption capacity reached 7218.31 mg/g when 0.01 g of OMB-KB and 300 ml of MG solution with a concentration of 300 mg/L were used for the adsorption at 298K. The increase of pH was beneficial to the adsorption of cationic MG, and the removal efficiency reached an excellent state at pH ≥ 6. The good fitting of the pseudo-second-order kinetic model and the Freundlich isotherm model suggested that the adsorption process was dominated by chemisorption. The thermodynamic analysis showed that the adsorption of OMB-KB to MG was endothermic, entropy-increasing and entropy-controlled. The adsorption of MG by the material was realized through the exchange interactions between cations, as well as the electrostatic attraction and van der Waals forces between –OH groups and MG. Meanwhile, the oxygen-containing groups and π-electrons in the carbon layer could also adsorb MG molecules by electrostatic attraction.