Analysis Of Adsorption Isotherms Research Articles

Preparation of Peanut Shell Cellulose Double-Network Hydrogel and Its Adsorption Capacity for Methylene Blue

To achieve optimal recovery and value-added utilisation of cellulose in peanut shells, the cellulose in peanut shells was first extracted using the sodium hydroxide-sodium chlorite method. Then, cellulose hydrogel was prepared by graft copolymerisation using N, N’-methylenebisacrylamide as the cross-linking agent, sodium persulfate as the initiator, and acrylic acid as the monomer. Orthogonal optimisation experiments were designed to obtain optimal process parameters for hydrogel preparation with the cellulose dosage of 0.40 g, initiator dosage of 0.20 g, polymerisation temperature of 70°C, cross-linking agent of 0.25 g, and monomer dosage of 3.0 mL. The effect of initiator dosage on hydrogel synthesis was the most significant, followed by monomer dosage and reaction temperature. Characterisation using X-ray diffraction analysis and scanning electron microscopy revealed that the hydrogel was amorphous and exhibited a distinct three-dimensional double network structure. Hydrogel swelling kinetic analysis showed that the hydrogel swelling process was divided into three stages, and fitted the Schott secondary swelling kinetic model. The prepared hydrogel had a good adsorption effect on methylene blue; the adsorption of methylene blue by the hydrogel was 1.259 mg/g at 25°C when the initial concentration of methylene blue was 5 mg/L. The adsorption kinetics of the hydrogel fit the pseudo-first-order kinetic model, pseudo-second-order kinetic model, Eovich model and particle diffusion model. The best fitting effect was obtained with the pseudo-second-order kinetic model. The adsorption isotherm analysis of methylene blue on hydrogel showed that the adsorption process was consistent with Langmuir and Freundlich models. The correlation coefficient of the Freundlich isotherm model was higher, indicating that the adsorption of methylene blue on hydrogel was mainly chemisorption.

Enhanced adsorption of methylene blue by mixed-phase bismuth ferrite prepared by non-aqueous sol-gel route

We report here a non-aqueous sol-gel synthesis of bismuth ferrite (BFO) particles in THF, DMF, and DMSO solvents, their subsequent utilization in adsorption of methylene blue, and a comparison of their adsorption efficiencies. BFO is attractive for adsorption because of its excellent dispersion in water. XRD data shows that all the solvents yield a mixture of a primary rhombohedral and a secondary orthorhombic phases with varying fractions. The DMSO yields the most impure samples having the highest fraction of secondary phase. However, the adsorption efficiencies of the samples order as DMF < THF < DMSO, with DMF showing 26.28 %, THF 51.63 %, and DMSO 96.54 %. A higher refractive index and donicity of DMSO leads to better solvation of the sol and incorporation of sulfur in the metal-oxide network during the sol-gel reaction. DMSO aids in columnar growth of orthorhombic phase, which, due to sulfur incorporation, forms a more open and less crystalline phase, which are the factors responsible for DMSO samples showing enhanced adsorption. Analysis of adsorption kinetics and isotherm on the DMSO samples confirms diffusive regimes pertaining to film-diffusion and intra-particle diffusion with the diffusive kinetics becoming faster at higher dye concentration. Fitting to Langmuir isotherm yields maximum monolayer coverage of 7.14 mg of dye per g of the adsorbent. The DMSO samples also show excellent adsorption at high pH conditions.

How β-cyclodextrin- loaded mesoporous SiO2 nanospheres ensure efficient adsorption of rifampicin.

In this study, β-CD@mesoporous SiO2 nanospheres (β-CD@mSi) were prepared by loading β-cyclodextrin (β-CD) onto mesoporous silica nanospheres through an in situ synthesis. This not only solved the defect of β-CD being easily soluble in water, but also changed the physical structure of the mesoporous silica nanospheres. FTIR and XPS results showed that β-CD was successfully loaded onto mesoporous silica nanospheres (mSi), while enhancing the adsorption effect. β-CD@mSi with a monomer diameter of about 150nm were prepared. At a temperature of 298k, the removal efficiency of a 100mg/L solution of rifampicin can reach 90% in 4h and the adsorption capacity was 275.42mgg-1at high concentration. Through the calculation and analysis of adsorption kinetics, adsorption isotherms and adsorption thermodynamics based on the experimental data, the reaction is a spontaneous endothermic reaction dominated by chemical adsorption. The electron transfer pathway, structure-activity relationship and energy between β-CD@mSi and rifampicin were investigated by quantum chemical calculations. The accuracy of the characterization test results to judge the adsorption mechanism was verified, to show the process of rifampicin removal by β-CD@mSi more clearly and convincingly. The simulation results show that π-π interaction plays a major interaction in the reaction process, followed by intermolecular hydrogen bonding and electrostatic interactions.

Removal of Co(II) from aqueous solutions with amino acid-modified hydrophilic metal-organic frameworks

Adsorbents capable of rapidly and efficiently adsorbing specific metal ions in solution are critical in emergency disposal and waste minimization of radioactive effluents. A microporous zeolitic imidazole framework-90 belonging to metal-organic frameworks (MOFs) was synthesized and functionalized with methionine and lysine to obtain ZIF-90-Met and ZIF-90-Lys with efficient and selective adsorption of cobalt ions. The synthesized materials were characterized by means of SEM, TGA, N2 adsorption–desorption, XRD and FTIR. The adsorption properties of two materials for Co(II) in simulated waste liquid were investigated. Under the conditions of pH = 6.69, T = 303 K and initial concentration of 500.00 mg·L−1, the maximum adsorption capacity of Co(II) on ZIF-90-Met and ZIF-90-Lys were 136.83 mg·g−1 and 164.40 mg·g−1, respectively. Two materials exhibit high selectivity in the adsorption of Co(II) and Ni(II) in multimetal ion solutions. Kinetic and adsorption isotherm analysis showed that the adsorption of Co(II) by ZIF-90-Met and ZIF-90-Lys was consistent with pseudo-second-order chemisorption and Langmuir monolayer adsorption. Thermodynamic analysis shows that the adsorption process of Co(II) by ZIF-90-Met and ZIF-90-Lys is spontaneous and endothermic.

Synthesis of Ce, N co–doped carbon dots as green and effective corrosion inhibitor for copper in acid environment

Background: A new high-effectively corrosion inhibitor was used to replace the traditional corrosion inhibitor and reduce the environment pollution.Methods: Through hydrothermal synthesis, Ce and N co-doped carbon dots (Ce@N-CDs) were generated. Before the performance characterization, the microstructure and chemical composition of Ce@N-CDs were firstly investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) techniques. The electrochemical test revealed that the IE of Ce-10% (200 mg/L) on copper was as high as 98%, presenting the best inhibition effect. According to the adsorption isotherm analysis, the Ce@N-CDs mainly adsorbed according to the Langmuir model, and the adsorption process was completed by combining physical and chemical adsorption.Significant findings: Through the morphology, energy dispersive spectrometer (EDS) and XPS analysis of copper surface after corrosion process, it was found that the Ce@N-CDs formed a dense adsorption/passivation film on the copper surface. The adsorption film mainly came from the pairing of unsaturated bonds between N-doped CDs (N-CDs) and copper surface. The passivation film mainly came from the oxide formed by the reaction between Ce and the surrounding environment. Their dense structure could effectively inhibit the infiltration and erosion of corrosive medium.

EFFECT OF CERTAIN CATALYTIC POISONS ON THE ACTIVITY OF CUPRUM-PALADIUM COMPLEXES APPLIED ON CARBON MATERIAL IN THE REACTION IN THE REACTION OF CARBON MONOXIDE OXIDATION BY AIR OXYGEN

Oxide and metal complex catalysts for low temperature gas-phase oxidation of carbon monoxide by air oxygen lose their activity under the action of chemical poisons such as SO2, H2S, PH3, H2O. We have developed a highly efficient Wacker-type catalyst in which the carrier is a carbon fiber material (CFM), the precursor of which was cellulose hydrate. For such a catalyst, there are no studies on the effect of catalytic poisons, namely SO2 and H2O, on its activity in the reaction of low-temperature oxidation of CO with oxygen. The morphology, elemental composition and adsorption properties of carbon fiber material and carbon monoxide oxidation catalyst are investigated. Pd(II)-Cu(II)/CFM relative to water vapor and sulfur dioxide, as well as their effect on the protective properties of the catalyst. SEM studies (scanning electron microscope) confirmed the morphology typical of CFM and found very small agglomerates in the case of the catalyst, which are formed by paratacamite Cu2(OH)3Cl crystallites caused by oxidation of the carbon surface by palladium (II). When applying the catalyst components, the fibers do not lose their shape, but the surface of the fibers is unevenly covered with impurities. Palladium (II) is reduced by a carbon surface by about 10%, agglomerates [Pdo]n are not observed, while fiber erosion increases and very small agglomerates are formed on the surface, which are formed by Cu2(OH)3Cl phase crystallites. Carbon material is generally characterized by a high content of carbon and oxygen, but their distribution is heterogeneous. In the analysis of adsorption isotherms, which are classified as type IV, it was found that CFM and the catalyst based on it belong to the microporous samples. It is proved that only at the relative humidity of the gas-air mixture, which is equal to 30% C &lt; MPCSO2 (20 mg/m3). Catalyst poisoning does not disrupt the catalytic process, but with increasing amount of absorbed sulfur dioxide (QSO2 ) the degree of conversion of carbon monoxide decreases and especially sharply at the absorption of 10.3⋅10–4 mol SO2. Thus, the results obtained on the effect of relative humidity and the amount of adsorbed by the catalyst SO2 on the activity of Pd(II)-Cu(II)/CFM catalyst, indicate a significant reduction in the degree of conversion of carbon monoxide. Therefore, in the case of applying of such a catalyst, for example in respiratory protection against CO, a preliminary stage of absorption of moisture and sulfur dioxide should be provided.

Preparation of novel magnetic porous biochar and its adsorption mechanism on cerium in rare earth wastewater

A novel and efficient process for the removal of Ce(IV) from aqueous solutions was sought, and a new magnetic porous biochar (PBC/ZF) was synthesized by loading ZnFe2O4 (ZF) onto porous biochar (PBC) using a one-step hydrothermal method. The SEM observation of the external features showed that the cubic spinel structured ZnFe2O4 (ZF) particles were loaded onto the porous biochar (PBC) surface. This resulted in a composite with superb paramagnetic properties as well as higher adsorption properties. In addition, the microstructure was characterized by FTIR, which demonstrated that the target material was supplied with a large amount of carboxyl groups (-COOH) by citric acid during the synthesis process. The BET showed that the target material had a higher specific surface area than ZnFe2O4 with PBC, confirming the successful preparation of the target material after activation of the biomass using ZnCl2 immersion as well. The effect of different factors on the adsorption effect was investigated experimentally. The results showed that PBC/ZF had a good adsorption effect on Ce(IV) with a short adsorption equilibrium time and a maximum adsorption capacity of 228.9 mg/g at room temperature with lower acidity (pH = 2.5). The adsorption kinetics and isotherm analysis showed that the Ce(IV) adsorption process fitted well with the quasi-secondary kinetic model and Langmuir model. It indicates that the process is a single molecular layer adsorption process. It was demonstrated that PBC/ZF also has high removal rate for high concentration Ce(IV) solution, and it is easy for solid-liquid separation under the action of applied magnetic field after adsorption. It provides a new treatment method and theoretical support for the adsorption treatment technology of Ce (IV) wastewater.

The Dilemma of Reproducibility of Gating Isotherms for Flexible MOFs.

Porous materials receive a high level of scientific and technological interest due to their applications in various fields such as adsorption, separation and storage, catalysis, ion exchange, nanotechnology, etc. Gas adsorption is a well-established tool for the characterization of the texture of porous solids. Physisorption isotherms are generally expected to be well reproducible for rigid adsorbents, but this is not always the case for nonrigid (flexible) materials. The presence of a metastability region and sensitivity of the activation barriers to the material's texture often influence the isotherms' run. Here, we address the complexity that arises in terms of reproducibility and sample handling for flexible metal-organic frameworks, with the example of DUT-8(Ni). It belongs to the group of "gate opening" metal-organic frameworks and is a typical representative of the pillared layer compounds. We propose characteristic parameters for the analysis and comparison of adsorption isotherms, showing the "gate opening" step, associated with the adsorption-induced solid-state phase transition. A set of 50 nitrogen physisorption isotherms measured at 77 K were analyzed and correlated with the synthetic and outgassing conditions. The study highlights the importance of accurate descriptions and record-keeping of experimental details and their role in the replication of scientific results.

Efficient and selective recovery of Gd(III) via polyethyleneimine modification of lanthanum-based metal–organic frameworks

With the development of the economy and the increasing demand for environmental protection, the efficient and selective recovery of Gd(III) from actual wastewater is of critical importance. In this work, lanthanum-based metal–organic framework (LaBDC) materials were prepared by a hydrothermal method, and then polyethyleneimine (PEI) and LaBDC were combined by an impregnation method to form a novel LaBDC@xPEI composite. The prepared materials were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Experiments show that LaBDC@50%PEI has the highest adsorption capacity (181.77 mg/g) among lanthanum-based MOFs with different PEI loadings at pH = 5.5, which is about 5.1 times that of bare LaBDC. The adsorption isotherm analysis shows that LaBDC@50%PEI follows the Langmuir model. In addition, the adsorption kinetics of LaBDC@50%PEI follows a pseudo-second-order kinetic model, indicating that the adsorption process is chemical adsorption. It is worth noting that LaBDC@50%PEI maintains good adsorption performance and stability after three recycling tests, and exhibits excellent selectivity in cation interference experiments. Overall, the LaBDC@50%PEI composites possess good stability and hold great promises in rapid recovery of Gd(III) from practical aqueous environments.

Lithofacies Characteristics and Sweet Spot Distribution of Lacustrine Shale Oil: A Case Study from the Dongying Depression, Bohai Bay Basin, China

Abstract Lacustrine shale is characterized by rapid lithofacies transformation and compositional heterogeneity, which present challenges in shale oil sweet spot evaluation and distribution prediction and should be systematically studied. Field emission-scanning electron microscopy (FE-SEM), low-pressure adsorption isotherm analysis, mercury intrusion porosimetry (MIP), and triaxial compression testing were employed to comprehensively analyze the oil-bearing capacity, reservoir properties, fluidity, and frackability of different lithofacies. Via analyses of mineral composition, total organic carbon (TOC) content, and sedimentary structure, seven lithofacies were identified: organic-rich calcareous shale (L1), organic-rich laminated calcareous mudstone (L2), organic-rich laminated carbonate-bearing mudstone (L3), intermediate-organic laminated calcareous mudstone (L4), organic-poor laminated calcareous mudstone (L5), organic-poor thin-bedded calcareous mudstone (L6), and organic-rich laminated silty mudstone (L7). Considered together, the oil-bearing capacity, reservoir properties, fluidity, and frackability suggested that the L1 and L7 lithofacies were high-quality sweet spots, with satisfactory oil-bearing capacity (TOC&amp;gt;3.5%; S1&amp;gt;10 mgHC/grock), well-developed pores and microfractures, notable fluidity (as indicated by a high oil saturation index value), and suitable brittleness. The sweet spot distribution was predicted according to multiresolution graph-based clustering analysis of well logs. The results indicate that comprehensive research of the key factors for shale oil and lithofacies prediction can promote sweet spot prediction and enhance shale oil exploration.

Bimetallic MOF derived ZnCo2O4 nanocages as a novel class of high performance photocatalyst for the removal of organic pollutants

• ZnCo-MOF derived ZnCo 2 O 4 nanocages was facilely synthesized with the help of a hydrothermal technique. • The kinetic studies exhibited the 84.3, 87.9, and 89.5% of degradation of CV, MB, and RhB dye pollutants after the 180 min of irradiation at the rate constants (k) of 0.010, 0.011, and 0.012 min −1 , respectively. • The ZnCo 2 O 4 nanocages delivered the highest photocatalytic degradation percentage for RhB than other organic dye pollutants. • The extensive role of photogenerated holes and hydroxide radicals affecting to the dye degradation phenomena is confirmed by radical scavenger trapping experiments. Synthesis of metal oxides from Metal organic frameworks (MOFs) has taken center stage in the recent years due to its excellent structural behavior. Many MOF derived metal oxides such as ZnO, NiO, Co 3 O 4 , CuO, NiCo 2 O 4 , and CoFe 2 O 4 , etc., has been successfully synthesized using MOFs as templates. In this report, we have adopted the MOF assisted method to prepare ZnCo 2 O 4 (abbreviated as ZCO) nanocages using hydrothermal method were utilized to explore the photocatalytic removal of various organic contaminants like Methylene Blue (MB), Rhodamine B (RhB), and Crystal Violet (CV). The ZCO nanocages has been investigated to evaluate the structural properties by X-ray diffraction (XRD) studies. Morphological, microstructural, chemical compositional and optical characterizations have been carried out using FESEM, TEM, EDS, XPS, and UV–Visible spectrophotometer, respectively. The specific surface area and pore size of ZCO nanocages were confirmed from nitrogen adsorption and desorption isotherm analysis. Further, ZCO nanocages were utilized to explore the photocatalytic removal of various organic contaminants like MB, RhB, and CV. Moreover, ZCO nanocages showed remarkable photocatalytic performance for the removal of different dye pollutants. The kinetic studies exhibited the 84.3, 87.9, and 89.5% of removal of CV, MB, and RhB dye pollutants after the 180 min of irradiation at the 0.010, 0.011, and 0.012 min −1 rate constants (k), respectively. The extensive role of hydroxide radicals and photogenerated holes affecting to the organic pollutant degradation mechanism is studied by radical scavenger trapping experiments. In addition, its recyclability was also confirmed from stability study. Therefore, the present investigations offer a way to develop a MOF derived metal oxide for photocatalytic removal of various organic pollutants.

Statistical physics analysis of adsorption isotherms and photocatalysis activity of MPA coated CuInS2/ZnS nanocrystals for the removal of methyl blue from wastewaters

Copper indium sulfide (CIS), zinc sulfide (ZnS) and CIS/ZnS nano-adsorbents (NAs) encapsulated with mercaptopropionic acid (MPA) were synthesized and characterized with different techniques, and finally tested for the adsorption/photodegradation of methyl blue dye (MB) in aqueous solution under UV irradiation. Structural and optical properties of the nanocrystals were determined via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscopic, UV–Visible and photoluminescence spectroscopy. CIS/ZnS showed a specific surface area of 24.06 cm2 g−1 and an adsorption capacity of 27.71 mg g−1 for MB. MB adsorption kinetic was found to follow the pseudo-second order kinetic model and the Langmuir-Freundlich model was the best model to describe the adsorption isotherms. Taking into account the statistical physics analysis and the theoretical meaning of the parameters, the Hill model with one activation energy presented the best prediction of the experimental data, indicating that MB dye adsorption occurred by the formation of a monolayer and that MB interaction with CIS/ZnS were characterized by only one activation energy. The calculated adsorption energy varied from 19.38 to 20.04 kJ mol−1 suggesting that the adsorption occurred via physical interactions via a multimolecular adsorption process. The photodegradation activity of the core–shell NAs under UV irradiation showed better efficiency than the bare core and Shell NAs thus indicating that ZnS recovery improved the degradation power of the CIS nano-adsorbents (97 %). In summary, these eco-friendly NAs are highly promising materials for efficient wastewater treatment to face water pollution caused by organic compounds via adsorption and photodegradation processes.

Physicochemical properties of porous activated carbon prepared from palm kernel shell through a low-cost activation protocol

Biomass-promoting routes for the synthesis of activated carbon (AC) have recently received considerable attention due to the advantages of this method: it is simple, cost-effective, and ecofriendly. This method is also an alternative way to avoid the unsafe practice of waste incineration. We describe the preparation of activated carbon from palm kernel shell (PKS) – an abundant biomass that is available in Africa and Asia. We investigated the effect of process variables such as impregnation ratio (ratio of H3PO4 to PKS) and carbonisation temperature (500–700 °C) on yield, microstructure, morphology, pore structure, and adsorption properties to optimise these parameters. Nitrogen adsorption isotherm analysis indicated that the AC was predominantly microporous in nature. Under optimal conditions, an AC with the highest surface area of 1560 m2/g was obtained. The aqueous adsorption test showed that the AC had significant removal capacity for methylene blue and iodine. The higher iodine value is consistent with the structural properties of the adsorbent, while the lower methylene blue value is consistent with the limited mesopore width. Considering the chemical and surface properties and adsorption properties of the AC produced, PKS has been shown to be an excellent precursor material for AC, thus solving the disposal problems associated with this biomass. Significance: AC significantly promotes adsorption and offers a low-cost and cleaner production method. PKS could serve as a dependable precursor for the synthesis of porous AC. This study provides useful information on how H3PO4-impregnated PKS influences the porosity of the resulting AC. Differences in porosity, yield, and morphology and Brunauer–Emmet–Teller surface area are achievable using AC from PKS.

Facile synthesis of hierarchical core–shell heterostructured ZnO/SnO2@NiCo2O4 nanorod sheet arrays on carbon cloth for high performance quasi-solid-state asymmetric supercapacitors

We synthesized the hierarchical ZnO/SnO2@NiCo2O4 core–shell nanorod sheet arrays (NRSAs) grown on a flexible conductive carbon cloth (CC) substrate by a hydrothermal method. The amalgamation and formation mechanism were proposed. The as obtained ZnO/SnO2@NiCo2O4 core–shell heterostructures is investigated using X-ray diffraction, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, field emission scanning electron microscopy, and nitrogen adsorption and desorption isotherm analysis. The SnO2 layer which is conducting between ZnO and NiCo2O4 may effectively boost the electrical conductivity of the electrodes and also defend the ZnO from corrosion in the alkaline solution. Benefitting from the core–shell heterostructure formation, the hybrid ZnO/SnO2@NiCo2O4//CC electrode delivered a high specific capacity of 244.5 mA h/g, enhanced cycling stability with a 94.5% retention in specific capacitance even after 10,000 continuous charge–discharge cycles and good rate capability. To utilize the high specific capacity and ultra-long cycling stability, the PVA-KOH gel electrolyte based solid-state hybrid supercapacitor device was assembled with AC//CC as a negative electrode and ZnO/SnO2@NiCo2O4//CC as a positive electrode. The fabricated HSC device delivered a specific capacitance of 117.5 F/g with high energy density (41.7 Wh/kg) and power density (6400 W/kg) along with the outstanding capacitance retention of 94.6% even after 10,000 continuous charging and discharging cycles. With exceptional electrochemical performance, a facile and cost-effective preparation, such ZnO/SnO2@NiCo2O4//CC core–shell heterostructured electrode show a great potential for high-performance electrochemical supercapacitor applications in future.

Mathematical analysis of the effect of process conditions on the porous structure development of activated carbons derived from Pine cones

This paper presents the results of a study on the influence of the degree of impregnation and activation temperature on the formation of the porous structure of activated carbons (ACs) obtained from Pine cones by the chemical activation process using potassium hydroxide as an activator. The advanced new numerical clustering based adsorption analysis (LBET) method, together with the implemented unique numerical procedure for the fast multivariant identification were applied to nitrogen and carbon dioxide adsorption isotherms determined for porous structure characterization of the ACs. Moreover, the Quenched Solid Density Functional Theory (QSDFT) method was chosen to determine pore size distributions. The results showed a significant influence of the primary structure of Pine cones on the formation of the porous structure of the developed ACs. Among others, it was evidenced by a very high degree of surface heterogeneity of all the obtained ACs, irrespective of the degree of impregnation with potassium hydroxide and the activation temperature. Moreover, the analysis of carbon dioxide adsorption isotherms showed, that the porous structure of the studied ACs samples contains micropores accessible only to carbon dioxide molecules. The results also showed a significant advantage of the LBET method over those conventionally used for porous structure analysis based on Brunauer–Emmett–Teller (BET) and Dubinin–Raduskevich (DR) equations, because it takes into account surface heterogeneities. The novel analyses methods were more fully validated as a reliable characterization tool, by extending their application to the isotherms for ACs developed from the same precursor by phosphoric acid activation, and for samples arising from these ACs, further subjected to additional post-treatments. The effect of the raw material used as precursor was moreover analysed by comparison with previous reported results for other ACs. The complementarity of the results obtained with the LBET and QSDFT methods is also noteworthy, resulting in a more complete and reliable picture of the analyzed porous structures.

Application of three types of aminated lignins for efficient removal of Cd(II) and Pb(II) ions in aqueous solution

Lignin is a renewable natural aromatic polymer that is generated as a co-product during lignocellulosic biorefinery processes, and it has been applied widely as a functional biomaterial. In this study, the adsorption behavior of Cd(II) and Pb(II) metal ions was investigated via ion chelation using aminated lignins (ALs) with primary, secondary, and tertiary amine groups. ALs exhibited optimal Cd(II) and Pb(II) adsorption capacities in solution under neutral conditions due to their chelating, electrostatic, and cationic–π interactions with metal ions. The AL with the primary amine group showed the highest adsorption capacities for both Cd(II) and Pb(II), reaching 83.2 and 159.7 mg·g-1, respectively, followed by the ALs with secondary and tertiary amine groups. The adsorption kinetics and isotherm analysis demonstrated that all adsorption behaviors followed the Langmuir isotherm and pseudo-second-order kinetics. Thermodynamic studies revealed that the adsorption processes of Cd(II) and Pb(II) using the ALs were spontaneous and endothermic. These results demonstrate that ALs are promising adsorbents for the removal of Cd(II) and Pb(II) metal ions.

Mechanism adsorption–reduction into the incorporation of microbial fuel cell–metal organic framework and overview of hydrodynamics effects for enhanced reduction of Cr(VI)

Due to the limitation of a sole method for removal of hexavalent chromium (Cr(VI)) which unable to process higher concentrations and limited efficiency of removal. Thus, the integrated reduction and adsorption system was designed by combining microbial fuel cell (MFC) and adsorbent (MOF type HKUST-1, UiO-66, and ZIF-8) to remove Cr(VI). HKUST-1 showed the highest adsorption capacity and Cr(VI) removal percentages compared to other MOF types, reaching 78.616 mg/g and 96.551 % in 90 min (batch adsorption), respectively. In addition, the pseudo-2nd-order kinetic and Langmuir isotherm type matched well with the suggested adsorption mechanism based on the adsorption kinetics and isotherms analysis. On the other hand, the highest power density resulted from the simultaneous integration of MFC adsorption, namely 198 mW/m2, and the removal rate of 99.34 % at 75 mg/L Cr(VI) concentration owing to MOF simultaneously adsorbs by forming a coordinating covalent bond and reducing it with electron donor groups in the organic linker of the MOF. Several important factors influencing the reduction rate of Cr(VI) in the MFC adsorption integration were pH, the Cr(VI) concentration, and substrate at the anode. Moreover, the hydrodynamic effect (agitation) can also increase the performance of the MFC, due to an increase in current leading to a high Cr(VI) removal. Furthermore, the MFC-adsorption integration showed better stability up to five cycles for 35 days. Overall, combining adsorption and MFC for Cr(VI) removal provides promising potency to be explored and developed for the wastewater treatment process.

Insight into adsorption mechanism, modeling, and desirability function of crystal violet and methylene blue dyes by microalgae: Box-Behnken design application

Herein, an environmentally friendly and efficient adsorbent of microalgae (MAG) was applied for the removal of crystal violet (CV) and methylene blue (MB) dyes from aqueous solutions. Multivariate modeling and optimization of CV and MB dyes removal onto MAG via Box-Behnken design (BBD) were investigated depending on three variables i.e. MAG dosage (20–100 mg), initial pH (4–10), and adsorption time (2–6 min). The adsorption kinetics and isotherm analyses revealed that the pseudo-second-order and Langmuir models governed the adsorption of CV and MB dyes onto MAG. The maximum adsorption capacity of MAG generated from the Langmuir equation was computed to be 243.0 mg/g for CV and 297.1 mg/g for MB. The determined thermodynamic parameters denoted that the adsorption mode of CV and MB dyes by MAG was spontaneous and endothermic. Several interactions like electrostatic forces, n-π stacking, and H-bonding caused the adsorption process of CV and MB molecules on the surface of MAG. The results showed that MAG could be an effective and locally available candidate adsorbent for removing dyestuffs from contaminated effluents. • Microalgae were applied for the removal of cationic dyes removal (crystal violet, CV) and (methylene blue, MB). • Box–Behnken design was applied to enhance the adsorption process. • The adsorption capacities for CV and MB were 243.0 mg/g and 297.1 mg/g, respectively. • The adsorption mechanism can be assigned to the electrostatic forces, n-π stacking, and H-bonding

Mechanical and microstructure performance and global warming potential of blended concrete containing rice husk ash and silica fume

The influence of cement replacement by rice husk ash (RHA) and silica fume (SF) is explored in this study. Several microstructural and mechanical properties of the control and different binary and ternary blends of concrete with various amounts of cement, RHA and SF were determined. The binary mix with 20% RHA (RHA20) as well as a ternary mix having 33% RHA along with 7% SF (RHA33SF7) presented highest strengths which is further confirmed from their lowest water absorption and apparent porosity values. The SEM-EDS analysis revealed the formation of dense and compact microstructure in RHA20 and RHA33SF7 probably due to the calcium hydroxide (CH) and highly dense calcium silicate hydrate (C-S-H) phases. Moreover, an increase in the Brunauer-Emmett-Teller surface area along with a reduction in intruded volume, as determined by the N2 adsorption isotherm analysis, proved the densified pore structure of these mixes. The results of the Fourier transform infrared (FTIR) spectroscopy showed a significant shift in the band from 955 to 977 cm−1 due to addition of RHA and SF that causes large amounts of C-S-H gels to form in these mixes. Moreover, both FTIR and thermogravimetric analysis analyses also showed significant reduction of their portlandite phase. In addition to enhanced micro-structural and mechanical performances, a relatively lower CO2-eq (equivalent to kg CO2) per MPa for RHA20 and RHA33SF7 indicates the significant positive impact of using higher amounts of regionally available supplementary cementitious materials in producing green concretes due to their reduced Global Warming Potential. The current findings demonstrated both RHA and SF to be used in concrete industry as a possible revenue source for developing sustainable concretes with high performance.

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents