Dynamic Adsorption Experiments Research Articles

Influence of biochar on the removal of Microcystin-LR and Saxitoxin from aqueous solutions

The present study assessed the effective use of biochar for the adsorption of two potent HAB toxins namely, Microcystin-LR (MCLR) and Saxitoxin (STX) through a combination of dosage, kinetic, equilibrium, initial pH, and competitive adsorption experiments. The adsorption results suggest that biochar has excellent capabilities for removing MCLR and STX, with STX reporting higher adsorption capacities (622.53–3507.46 µg/g). STX removal required a minimal dosage of 0.02 g/L, while MCLR removal needed 0.4 g/L for > 90%. Similarly, a shorter contact time was required for STX removal compared to MCLR for > 90% of toxin removed from water. Initial pH study revealed that for MCLR acidic conditions favored higher uptake while STX favored basic conditions. Kinetic studies revealed that the Elovich model to be most suitable for both toxins, while STX also showed suitable fittings for Pseudo-First Order and Pseudo-Second Order in individual toxin systems. Similarly, for the Elovich model the most suited kinetic model for both toxins in presence of each other. Isotherm studies confirmed the Langmuir–Freundlich model as the best fit for both toxins. These results suggest adsorption mechanisms including pore filling, hydrogen bonding, π–π interactions, hydrophobic interactions, electrostatic attraction, and dispersive interactions.

Performance on adsorption of toluene by ionic liquid-modified AC in high-humidity exhaust gas.

Volatile organic compounds (VOCs) frequently pose a threat to the biosphere, impacting ecosystems, flora, fauna, and the surrounding environment. Industrial emissions of VOCs often include the presence of water vapor, which, in turn, diminishes the adsorption capacity and efficacy of adsorbents. This occurs due to the competitive adsorption of water vapor, which competes with target pollutants for adsorption sites on the adsorbent material. In this study, hydrophobic activated carbons (BMIMPF6-AC (L), BMIMPF6-AC (g), and BMIMPF6-AC-H) were successfully prepared using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) to adsorb toluene under humidity environment. The adsorption performance and mechanism of the resulting ionic liquid-modified activated carbon for toluene in a high-humidity environment were evaluated to explore the potential application of ionic liquids as hydrophobic modifiers. The results indicated that BMIMPF6-AC-H exhibited superior hydrophobicity. The toluene adsorption capacity of BMIMPF6-AC-H was 1.53 times higher than that of original activated carbon, while the adsorption capacity for water vapor was only 37.30% of it at 27 °C and 77% RH. The Y-N model well-fitted the dynamic adsorption experiments. To elucidate the microscopic mechanism of hydrophobic modification, the Independent Gradient Model (IGM) method was employed to characterize the intermolecular interactions between BMIMPF6 and toluene. Overall, this study introduces a new modifier for hydrophobic modification of activated carbon, which could enhance the efficiency of activated carbon in treating industrial VOCs.

An investigation into the effect of UV irradiation and biofilm colonization on adsorption and desorption behavior of polyurethane (PU) microplastics for bisphenol A (BPA)

Recent studies have demonstrated that microplastics (MPs) can act as a transport vector for pollutants in the environment. However, most studies have focused on carbon-carbon backbone polymers, with little known about heteroatom backbone polymers. In this study, polyurethane (PU) MPs were modified by UV irradiation and microorganism colonization to assess the different aging treatments on the interaction behavior (adsorption/desorption) between PU MPs and bisphenol A (BPA). The results of the adsorption kinetics experiment illustrated that the adsorption process of BPA could be described well by a pseudo-second order kinetic equation on both fresh and aged PU MPs. Although fresh PU MPs revealed the highest saturated adsorption capacity, at low BPA exposure concentrations (≤ 100 μg/L) the adsorption capacities for UV aged and biofilm colonized PU MPs were very similar to fresh MPs or even slightly higher than for fresh MPs, the main adsorption mechanisms including H-bonding interactions and π–π interactions. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) investigations suggested obvious physicochemical property changes (e.g., generation of new functional groups, erosion, etc.) after UV irradiation and biofilm colonization. This study also showed that different exposure environments (ultrapure water, artificial seawater, simulated gastric fluid) could affect BPA adsorption/desorption via hydrophobic and electrostatic interaction on PU surfaces. These results further clarify the adsorption mechanisms of BPA on PU MPs that have undergone different aging treatments, and provides a theoretical basis for the assessment of environmental behavior and exposure risks when PU MPs and BPA coexist.

Synthesis and demulsification performance of a novel low-temperature demulsifier based on trimethyl citrate

A significant amount of water-in-oil (W/O) emulsion is generated during petroleum extraction. However, the current commercial demulsifiers are expensive to produce and requires high demulsification temperatures, leading to increased energy and economic consumption. To enhance the efficiency of demulsifiers and reduce the cost of demulsifying W/O emulsions, we have successfully developed a novel demulsifier named TCED through a straightforward two-step process. This demulsifier features trimethyl citrate as the hydrophilic core grafted with three hydrophobic chains. Its structure was characterized using EA, FT-IR and 1H NMR spectroscopy, and the demulsification performance was comprehensively evaluated. At a low demulsification temperature of 40 °C, TCED demonstrated a remarkable demulsification efficiency (DE) of 99.06% and 98.74% in emulsions containing water contents of 70% (E70) and 50% (E50), respectively. Especially, a DE of 100% could be obtained in both E70 and E50 emulsions at a concentration of 600 mg/L. Moreover, TCED displayed a high DE even at high salinity levels of 50,000 mg/L and across a wide pH range of 2–10. Additionally, the phase interface was consistently clear after demulsification. To investigate the demulsification mechanism of TCED, various adsorption kinetics experiments were conducted, including measurements of interfacial tension (IFT), surface tension (SFT), interfacial competitive adsorption, and stability of interfacial film. The results obtained from the experiments indicated that TCED possessed remarkable diffusion and replacement capabilities within the emulsions. As a result, it effectively disrupted the original interfacial active substances, such as asphaltenes aggregates found in crude oil. TCED exhibits a high DE at low concentration and temperature. This characteristic highlights its significant potential for low-temperature demulsification applications in the petroleum industry.

Arsenic and fluoride adsorption from multielement solutions onto aluminium modified montmorillonite

Groundwater is the primary source of drinking water worldwide. However, it might be harmful to consumer's health due to the presence of trace elements, such as arsenic and fluoride, commonly found in Latin American. The main objective of this study was to investigate the adsorption parameters of arsenic (As) and fluoride (F) dissolved in multielemental solutions containing vanadium (V) and boron (B), on aluminium-modified montmorillonite. To achieve that, a new adsorbent was synthesised and characterised using X-ray diffraction spectroscopy (XRD), Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-Ray (EDX) and N2 adsorption/desorption isotherm techniques. Adsorption efficiencies for As and F were evaluated in multielement solutions considering the simultaneous occurrence of B and V, naturally present in groundwater. Kinetic and equilibrium adsorption experiments were carried out in batch conditions for both, mono and multicomponent solutions. The adsorbent characterization indicated an effective incorporation of Aluminium (Al) into the aluminosilicate layers and at the external surface of the montmorillonite. The adsorption process for multielement solutions took a short time and the As adsorption was not affected by the presence of V, B, or F in the solution while F adsorption parameters were enhanced by the co-occurrence of the other species in the solution. The maximum adsorption capacities were 21 and 68 mg g−1 for As and F, respectively, in the presence of B and V, at low adsorbent dosage. The new material was also tested for groundwater samples collected from Buenos Aires province (Argentina) that were naturally contaminated with As, V, B, and F. The removal of these elements was lower when compared to synthetic solutions. However, the material's efficiency in removing the ions from natural groundwater was approximately 50%. These results suggest that the material could be used to develop filters to remediate arsenic and fluoride from naturally contaminated groundwater.

Effective uranium extraction from seawater through immobilization of conjugated microporous polymers on collagen fiber membrane

Extracting uranium from seawater has become an important method to supplement the nuclear industry. Herein, we introduce a simple route to load conjugated microporous polymers onto collagen fiber membranes, resulting in a novel membrane adsorbent material (CMPA-F/CFM) for uranium capture. Its Langmuir adsorption capacity reaches 304.9 mg·g−1 (at 318 K), with fast adsorption kinetic of 60 min, and excellent adsorption selectivity with Kd = 4.69 × 104 mL·g−1 under the temperature of 298 K, initial concentration of 50 mg·L-1, and pH = 7, thus allowing a satisfactory adsorption performance in a 7-day real ocean experiment with a uranium adsorption capacity of 1.25 mg·g−1. Furthermore, in continuous dynamic adsorption experiments, CMPA-F/CFM could treat up to 19.0 L·g−1 of low-enriched uranium (LEU) solution (1 mg·L-1), with a uranium removal rate of up to 87.5 % (10 L of seawater). This study demonstrates broad potential application of membrane adsorption in extraction of low-enriched uranium.

Naphthenic acids removal using N-doped hemp fibers based mesoporous carbon from aqueous waste stream

There is a substantial need for removing the contaminants from aqueous waste stream using affordable, stable, and active adsorbents, such as heteroatom-doped carbonaceous materials. Heteroatom such as N-doped carbonaceous materials greatly improve the performance of carbon materials by enhancing their conductivity, basicity, oxidation stability, catalytic activity and adsorption capacity. In this study, hemp fibers (HFs) and N-aminoguanidine were utilized as carbon and nitrogen precursors to synthesize N-functionalized mesoporous carbon materials (N-HFCs) via simultaneous activation and carbonization with ZnCl2. Higher BET surface area with a distinctive mesoporous structure and the covalent bond between N and C was developed in the prepared carbon, making N-HFCs suitable for adsorbing naphthenic acids (2-naphthoic acid and benzoic acid) from aqueous waste streams. Developed covalent bond helps to prevent the leaching of carbonaceous materials during adsorption study. The results showed that N-HFC-2 (ZnCl2: N-HFs ratio = 2:1) exhibited a higher removal efficiency of naphthenic acids (2-naphthoic acid and benzoic acid) compared to nonfunctionalized porous carbon (HFC). Adsorption of 2-naphthoic acid and benzoic acid on the adsorbents followed the typical monolayer type of Langmuir adsorption model. The maximum adsorption capacity of HFC after 48 h was evaluated as 70 and 27 mg/g for 2-naphthoic acid and benzoic acid. Likewise, the maximum adsorption capacity of N-HFC-2 for 2-naphthoic acid and benzoic acid was found to be 71 and 33 mg/g. In the adsorption kinetic experiment, adsorption of 2-naphthoic acid and benzoic acid reached equilibrium within 1 h using both the adsorbents (N-HFC-2 and HFC). Adsorption kinetics were analyzed using pseudo-first-order and pseudo-second-order kinetic models and were found to follow a pseudo-second-order kinetic model. Although changing pH from 4.4 to 8.5 did not have any significant effect on the removal efficiency of 2-napthoic acid using HFC and N-HFC-2, the removal efficiency of benzoic acid was decreased from 94 to 60 % using HFC and increased from 98 to 100 % using N-HFC-2. Comparative evaluations demonstrated that the mesoporous carbonaceous materials derived from HFs are an attractive adsorbent for removal of such contaminants from contaminated aqueous streams.

Selective adsorption of zearalenone by a novel magnetic molecularly imprinted carbon nanomaterial.

In this paper, the objective is to immobilize molecularly imprinted polymers (MIPs) onto the surface of magnetic carbon nanoparticles (Fe3O4@SiO2@C) to develop an effective method for the adsorption of zearalenone (ZEN). The prepared products were characterized by FT-IR, SEM, TEM, XRD, VSM, TGA, and BET. The content of zearalenone in corn samples was monitored by HPLC. The results indicate that the particle size of magnetic molecularly imprinted polymers (MMIPs) is approximately 200nm. The adsorption mechanism of MMIPs was confirmed by static adsorption and dynamic adsorption experiments. The maximum adsorption capacity was 1.56mg/g, and the adsorption equilibrium was reached within 50min. The scatchard model showed that MMIPs had two binding sites, a high-affinity binding site and a low-affinity site. Kinetic second-order fitting indicates that MMIPs are mainly through chemisorption. In the actual sample application, the limit of detection (LOD) and limit of quantitation (LOQ) were 0.3mg/L and 0.9mg/L, respectively. The recovery of corn with the standard addition of ZEN was 73.6-88.1%, and the relative standard deviation (RSD) was 2.86-5.63%. The results demonstrated that MMIPs possess the advantages of straightforward operation, high precision, and cost-effectiveness, rendering them suitable for rapid ZEN detection.

Adsorption of methyl blue, dichromate, and copper on ettringite under various pH values

Ettringite is a hydrous calcium aluminum sulfate mineral present in cement. In this study, ettringite was synthesized via co-precipitation to remove methyl blue, dichromate, and copper ions from solutions with various pH values. The synthesized ettringite was characterized using scanning electron microscopy, X-ray photoelectron spectrometry, Fourier transform infrared spectroscopy, zeta potential analysis, and the Brunauer–Emmett–Teller method. Equilibrium adsorption experiments were performed using methyl blue and dichromate at pH values ranging from 5 to 11. To avoid precipitation, equilibrium adsorption experiments were performed on copper ions in solutions with pH values of 3, 4, and 5. The adsorption kinetics experiments for each contaminant were performed at pH 5. The results showed that ettringite was successfully synthesized, and calcite might have precipitated during the synthesis process. The point of zero charge was at pH 8.6. The maximum adsorption capacities for methyl blue, dichromate, and copper ions at pH 5 were 406, 321, and 365 mg/g, respectively. The adsorption kinetics fitted the pseudo-second-order model well. The properties of the contaminants affect their equilibrium and rate constants. Ion exchange is regarded as the primary adsorption mechanism, whereas the other mechanisms include complexation, hydrogen bonding, surface precipitation, π-interaction, and van der Waals forces. This study revealed a new adsorbent, ettringite, for the removal of contaminants from wastewater, which is a promising alternative adsorbent that can be used under specific conditions.

Functionalized activated carbon with whey protein amyloid fibrils for adsorption of arsenic from water

Globally, more than 200 million people are exposed to elevated concentrations of arsenic in groundwater, thus representing an important environmental and public health problem. Apart from inorganic species, water quality suffers also from the occurrence of organic pollutants discharged by the food sector like whey, a by-product of the dairy industry. The valorisation of these organic residues is relevant to reduce water pollution and to develop new materials for different applications. This research reports the synthesis and evaluation of a novel adsorptive activated carbon composite modified with whey protein amyloids for arsenic removal from water. The adsorbent was characterized with FT-IR spectroscopy, X-ray diffraction, N2 physisorption, pH at point of zero charge determination, and thermogravimetric analysis. Experimental adsorption kinetics and isotherms of arsenic removal were determined at optimal pH 5.0, best fitted with the PSO and Sips model, respectively. The corresponding maximum adsorption capacity for As5+ was 0.16 mmol g−1 through an endothermic process. Surface complexation was the predominant phenomenon in the adsorption mechanism as the As-O bond was formed via whey’s functional groups, hydroxyl, amine, and amide, with the latter having the strong affinity to arsenate as elucidated by the HSAB theory. This study highlights the potential of whey protein as a raw material to produce added-value products and its performance as a precursor of novel adsorbents for water purification, therefore minimizing their associated disposal cost and addressing relevant environmental concerns such as arsenic contamination.

Synthesis of stable mesoporous Zr-MOFs using pyrazine-containing ligand for efficient capture of Pb(II) in wastewater

By optimizing the reaction conditions, a zirconium-based adsorbent Zr-PzDC with pyrazine-2,5-dicarboxylic acid as the ligand was synthesized for the treatment of lead ions in an aqueous solution. SEM, EDS-Mapping, XRS and FT-IR characterization confirmed the synthesis of Zr-PzDC. Meanwhile, BET results show that Zr-PzDC is a typical mesoporous material. The analysis of the binding process of Zr-PzDC with Pb(II) in water shows that the adsorption kinetics conform to the pseudo-second-order model; The adsorption isotherm data fits well with the Langmuir model, and the maximum adsorption capacity of Pb(II) is 298.39 mg/g; The thermodynamic parameters show that the adsorption of Pb(II) in water is a spontaneous endothermic process. Combined with the XPS spectral results, physical adsorption is the main binding mode, and single-layer chemisorption is the limiting step in the adsorption process. The results of both static and dynamic column adsorption experiments show that Zr-PzDC can treat lead ions quickly and efficiently, and has excellent reusable performance, which makes Zr-PzDC have good application potential in treating lead-containing wastewater of the battery production process.

Mesoporous Carbons and Highly Cross-Linking Polymers for Removal of Cationic Dyes from Aqueous Solutions-Studies on Adsorption Equilibrium and Kinetics.

This study presents the results of applying the methods of synthesizing mesoporous carbon and mesoporous polymer materials with an extended porous mesostructure as adsorbents for cationic dye molecules. Both types of adsorbents are synthetic materials. The aim of the presented research was the preparation, characterisation, and utilisation of obtained mesoporous adsorbents. The physicochemical properties, morphology, and porous structure characteristics of the obtained materials were determined using low-temperature nitrogen sorption isotherms, X-ray diffraction (XRD), small angle X-ray scattering (SAXS), and potentiometric titration measurements. The morphology and microstructure were imaged using scanning electron microscopy (SEM). The chemical characterisation of the surface chemistry of the adsorbents, which provides information about the surface-active groups, the elemental composition, and the electronic state of the elements, was carried out using X-ray photoelectron spectroscopy (XPS). The adsorption properties of the mesoporous materials were determined using equilibrium and kinetic adsorption experiments for three selected cationic dyes (derivatives of thiazine (methylene blue) and triarylmethane (malachite green and crystal violet)). The adsorption capacity was analysed to the nanostructural and surface properties of used materials. The Generalized Langmuir equation was applied for the analysis of adsorption isotherm data. The adsorption study showed that the carbon materials have a higher sorption capacity for both methylene blue and crystal violet, e.g., 0.88-1.01 mmol/g and 0.33-0.44 mmol/g, respectively, compared to the polymer materials (e.g., 0.038-0.044 mmol/g and 0.038-0.050 mmol/g, respectively). The kinetics of dyes adsorption was closely correlated with the structural properties of the adsorbents. The kinetic data were analysed using various equations: first-order (FOE), second-order (SOE), mixed 1,2-order (MOE), multi-exponential (m-exp), and fractal-like MOE (f-MOE).

Bio-sorption capacity of cadmium and zinc by Pseudomonas monteilii with heavy-metal resistance isolated from the compost of pig manure

The tolerance of Pseudomonas monteilii X1, isolated from pig manure compost, to Cd and Zn, as well as its capacity for biosorption, were investigated. The minimum inhibitory concentrations (MIC) of Cd and Zn for the strain were 550 mg/L and 800 mg/L, respectively. Untargeted metabolomics analysis revealed that organic acids and derivatives, lipids and lipid-like molecules, and organic heterocyclic compounds were the main metabolites. The glyoxylate and dicarboxylate metabolism pathway were significantly enriched under Cd2+ stress. The isothermal adsorption and adsorption kinetics experiments determined that the strain had adsorption capacities of 9.96 mg/g for Cd2+ and 23.4 mg/g for Zn2+. Active groups, such as hydroxyl, carboxyl, and amino groups on the cell surface, were found to participate in metal adsorption. The strain was able to convert Zn2+ into Zn3(PO4)2·4H2O crystal. Overall, this study suggested that Pseudomonas monteilii has potential as a remediation material for heavy metals.

Selective adsorption and identification of penicillin G sodium in milk by molecularly imprinted polymer doped carbon dot.

A carbon dot (CD) was prepared by o-phenylenediamine and water, which showed bright yellow fluorescence under ultraviolet light irradiation (λ = 580nm), and verified good fluorescence quenching effect on penicillin G sodium (Png-Na). Using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, and Png-Na as a template, a kind of composite microsphere combining CD and molecularly imprinted polymer (MIP) was synthesized by surface-initiated atomic transfer radical polymerization (SI-ATRP). For reasons ofcomparison, we also prepared MIP without CD and non-imprinted polymers (NIPs). Through static and dynamic adsorption experiments, the maximum adsorption capacity was 47.05mgg-1 and the equilibrium time was 30min. High-performance liquid chromatography (HPLC) was utilized to determine the content of Png-Na in the spiked milk samples. A sensitive, rapid, and simple method for determination of Png-Na in food samples was developed. The utilized approach enabled the quantification of Png-Na within theconcentration range 20-1000μg L-1 (with a limit of detection of 5μg L-1). The recoveries achieved were in the range 93.3-98.2%, with a relative standard deviation of 1.2-4.2%. The results demonstrated that CD@MIP possessed the capability of specific adsorption and fluorescence detection of Png-Na, enabling simultaneous detection and enrichment of Png-Na in real samples.

Separation of 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene by metal-organic framework Co(aip)(bpy)0.5

BackgroundThe separation of trimethylbenzene isomers is one of the most challenging problems in chemical industry because of their similar boiling points and kinetic diameters. The adsorption performance of 1,3,5-trimethylbenzene (1,3,5-TMS) and 1,2,4-trimethylbenzene (1,2,4-TMS) (1,3,5-TMS/1,2,4-TMS = 1:1) on Co(aip)(bpy)0.5 with cobalt-based columnar lamellae were investigated in this paper. MethodsIn this study, we used competitive adsorption experiments, kinetic and thermodynamic experiments, and regeneration experiments to investigate the adsorption amount and relative selectivity of 1,3,5-TMS and 1,2,4-TMS on Co(aip)(bpy)0.5, adsorption mechanism, and regeneration properties of Co(aip)(bpy)0.5. Significant findingsCompetitive adsorption experiments showed that Co(aip)(bpy)0.5 presented the highest relative selectivity α1,2,4-TMS/1,3,5-TMS among the eight MOFs studied. Both pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models were used to fit the data, which indicated that the PSO model was more compatible. Thermodynamic data was fitted by Langmuir, Freundlich, and Temkin models, from which the Langmuir model was most suitable. Thermodynamic parameters demonstrated that the adsorption was spontaneous and exothermic. The α1,2,4-TMS/1,3,5-TMS could reach 3.5 at 298.15 K. The crystal structure and adsorption experiments suggested that the separation of 1,3,5-TMS from 1,2,4-TMS on Co(aip)(bpy)0.5 was mainly due to π-π interaction, unsaturated metal ions, and Lewis acid-base interaction. After five adsorption-regeneration cycles, the adsorption amount of 1,3,5-TMS and 1,2,4-TMS decreased by 0.12 % and 0.05 %, respectively, and α1,2,4-TMS/1,3,5-TMS remained above 3.0.

Investigation of synergistic mechanism of magnesium ions and cationic surfactant in low-rank coal flotation

The effect of magnesium ions on the adsorption of DTAB (Dodecyltrimethylammonium Bromide) surfactants by low-rank coal using adsorption experiments and microscopic mechanism analysis. In addition, the flotation recovery of coal was summarized for application by micro flotation test. The results of adsorption experiments showed that 0.1 mM magnesium ions concentration is optimal, with 12.55 mg/g adsorption capacity. Besides, correlation analysis reveals that the adsorption capacity is positively correlated with temperature, surfactant concentration, reaction time and the magnesium ions density. Adsorption thermodynamics and kinetics experiments indicate that magnesium ions promote adsorption by increasing the adsorption active sites of coal and accelerating the adsorption rate of DTAB on coal. Furthermore, the results of contact angle, zeta potential, model calculations and FTIR (Fourier transform infrared spectroscopy) analyses reveal that magnesium ions and its hydrolysates can adsorb on the coal as a bridge and destroy the stable hydrogen bond on the coal to activate the adsorption, which enhance the negatively charged coal to electrostatically adsorb positively charged DTAB. Moreover, the recovery rate of low-rank coal flotation using DTAB combined with magnesium ions was tested by a micro flotation apparatus, which provides a guidance for the flotation application by saline surfactant solution on coal.

Frankincense-Based Functionalized Multiwalled Carbon Nanotubes with Iron Oxide Composites for Efficient Removal of Crystal Violet: Kinetic and Equilibrium Analysis.

In this study, novel adsorbents were developed by functionalizing multiwalled carbon nanotubes with frankincense (Fr-fMWCNT) and adding iron oxide (Fe3O4) to the adsorbent (Fr-fMWCNT-Fe3O4). The morphology, surface characteristics, and chemical nature of the synthesized samples were analyzed by using various characterization techniques. The prepared adsorbents were then applied for the elimination of the toxic dye, crystal violet (CV), from water-based solutions by employing a batch adsorption method. The effectiveness of materials for the adsorption of CV was investigated by tuning various effective experimental parameters (adsorbent dosage, dye quantity, pH, and contact time). In order to derive adsorption isotherms, the Langmuir and Freundlich adsorption models were investigated and compared. The Fr-fMWCNT and Fr-fMWCNT-Fe3O4 were found to remove 85 and 95% of the CV dye within 30 min of the adsorption experiment at pH 6, respectively. It was found that a pseudo-second-order reaction rate was consistent with the experimental adsorption kinetics. The equilibrium data demonstrated that the Langmuir model adequately explained the adsorption behavior of the CV dye on the Fr-fMWCNT and Fr-fMWCNT-Fe3O4 surfaces, respectively. According to the Langmuir study, the highest adsorption capacities of the dye are 434 mg/g for Fr-fMWCNT and 500 mg/g for Fr-fMWCNT-Fe3O4. Remediation of the CV dye using our novel composite materials has not been reported previously in the literature. The synthesized Fr-fMWCNT and Fr-fMWCNT-Fe3O4 adsorbents can be economical and green materials for the adsorptive elimination of CV dye from wastewater.

Use of welding powder as a low‐cost adsorbent for waste motor oil removal

AbstractWaste motor oil (WMO), which has no stable form or structure, causes major environmental problems and damage to the ecosystem once it is disposed to the environment. Because of the high toxicity of contents in such effluent, it must be treated before being discharged into the receiving environment. In recent years, the valorization and the use of waste materials to remove toxic pollutants is of great importance to researchers and diverse industries. In this study, the usability of waste welding powder (WWP) as an adsorbent for waste oil removal was investigated. For this purpose, investigating the usability of material, which is generated as industrial waste, in wastewater treatment will lead to the evaluation of waste. The effects of temperature, pH, WWP amount, and initial WMO amount were investigated. According to the adsorption studies, 1 g WWP/L of the processed adsorbent was able to effectively remove 95.05% of WMO (100 mg) at a pH of 2 at 30°C. Stereo microscopy images showed a large amount of oil adsorbed on the WWP surface. The different WWP properties were determined by adsorption isotherm (Harkins–Jura), kinetic (pseudo‐second order), and thermodynamic (ΔG: −5.1 kJ mol–1) experiments. It is thought that WWP, which is a low‐cost and waste material, can be used as a promising adsorbent in WMO removal.

Hemocompatible polyethylenimine-grafted poly (glycidyl methacrylate) based microspheres for effective endotoxin removal

Endotoxin (also known as lipopolysaccharide, LPS), the major component in the outer cell wall of Gram-negative bacteria, is considered to be a main cause of sepsis. To reduce the mortality of sepsis, adsorbents with positively charged surfaces like polyethylenimine (PEI) are commonly employed to adsorb endotoxins; however, there are hidden dangers in binding stability and hemocompatibility of PEI-grafted materials. Herein, poly (glycidyl methacrylate) microspheres prepared by electro-spraying are chosen as the substrate, the surface epoxy groups are utilized to chemically immobilize PEI molecules. Then, heparin coatings are introduced through electrostatic interaction to obtain composite microspheres as hemoperfusion adsorbent. As a result, the hemocompatibility of the microspheres is significantly improved after the introduction of the heparin coatings. Compared to the microspheres only grafting PEI, the hemolysis ratio has a huge decrease from 4.6% to 1.0%. The adsorption process of the composite microspheres is more consistent with Sips isotherm model with a theoretical maximum endotoxin adsorption capacity of 2659.1 EU/g in normal saline solution. And the microspheres exhibit high endotoxin clearance ratio of 81.3% in static plasma (C0 = 12.6 EU/mL, exceeding critical illness level). In vitro dynamic adsorption experiments also indicate that the microspheres remove 86.6% of endotoxin in septic plasma (C0 = 7.2 EU/mL, exceeding critical illness level) within 1 h. We hope that the composite microspheres could have good application potential as an efficiency endotoxin adsorbent in sepsis treatment.

Synthesis of micro-mesoporous hierarchical structure of coal-based activated carbon and its effect on methane adsorption

This research synthesized a series of porous carbon materials utilizing three different coal-rank samples as raw materials through carbonization and activation processes. The resulting activated carbon has a high specific surface area of up to 2092.83 m2/g, a micro-mesopores volume of 1.08 cm3/g and a hierarchical porous structure, and the surface is enriched with heteroatoms. These properties can be adjusted by adjusting the charging temperature, activation temperature and KOH/Coal mass ratio. Methane adsorption experiments showed that the maximum adsorption capacities of the three activated carbons at 40℃ were 7.97 mmol/g, 9.34 mmol/g, and 11.71 mmol/g (Langmuir parameter a), respectively. It was found that methane adsorption is primarily related to nanopores (0.5 nm −2 nm), with micropores playing a dominant role and mesopores supplying transport channels for gas molecules and contributing to their immobilization on solid surfaces. The results of the dynamic and static adsorption experiments were consistent, demonstrating that better adsorption separations could be attained for samples with stronger molecular affinities. Coal-based activated carbon shows potential as a material for low-concentration methane separation due to its superior affinity for methane molecules, providing theoretical support for the selection of materials for variable pressure adsorption.