Adsorption Kinetic Data Research Articles

Kinetics of Adsorption-Induced Deformation of Microporous Carbons.

Equilibrium and kinetic behavior of adsorption-induced deformation have attracted a lot of attention in the last few decades. The theoretical and experimental works cover activated carbons, coals, zeolites, glasses, etc. However, most of the theoretical works describe only the equilibrium part of the deformation process or focus on the time evolution of the adsorption process. The present paper aims to cover the existing gap using the thermodynamic framework combined with the diffusion-based description of adsorbate time evolution inside an adsorbent. We obtained self-consistent equations describing equilibrium and out-of-equilibrium adsorption, as well as deformation processes. Further, the obtained equations were verified on the experimental data of carbon dioxide and methane on activated carbons. The model is capable of describing both equilibrium and kinetic adsorption and adsorption-induced deformation data. Additionally, we studied the possible influence of slow relaxation processes in the adsorbent on the adsorption process. The current work helps to interpret experimental data for time-dependent adsorption-induced deformation.

Endoxylanase Immobilized Nanoporous Silica for the Production of Xylooligosaccharides: Equilibrium Kinetics, Thermodynamic Studies, and Enzyme Characteristics

AbstractNanoporous structured silica materials, namely f‐SiO2, SBA‐15, IITM‐41, and MCM‐41 were employed as the matrices for immobilizing endoxylanase by adsorption method. The equilibrium kinetics, activation energy, and thermodynamic parameters associated with endoxylanase adsorption were investigated. Our findings revealed a two‐phase adsorption mechanism: an initial phase featuring rapid adsorption rates, succeeded by a slower phase wherein adsorption gradually progressed until equilibrium was attained. Analysis of the adsorption kinetic data indicated a better fit with the pseudo‐second‐order model, suggesting chemisorption and highlighting its temperature dependency. The calculated activation energy (Ea) values fell within the range of physisorption, indicating the involvement of both types of adsorption processes. Thermodynamic assessments confirmed that the adsorption reactions were spontaneous, feasible, and endothermic. Notably, the immobilization process did not change the optimum pH of the enzyme, while the optimum temperature shifted slightly. Furthermore, immobilized enzymes show a higher reaction rate (Vmax) than the soluble XynC. All immobilized xylanases produced xylobiose (X2) to xylohexose (X6) by hydrolyzing the xylan substrate. Recycling studies showed that up to 80 % of the yield was retained after seven cycles of reuse. Our study demonstrates the potential of nanostructured silica as an effective immobilization matrix for enzymes of industrial significance.

Synthesis and Characterization of cellulose-derived superabsorbent hydrogel and its applications in the treatment of wastewater containing heavy metal ions

A cellulose xanthate (CX) based polymer hydrogel has been synthesized using free radical graft polymerization technique. Two monomers Acrylic Acid (AA) and Acrylonitrile (AN) were reacted with cellulose xanthate to synthesize the desired hydrogel CX-g-poly(AA-co-AN). The synthesized hydrogel has been characterized by various techniques viz. Thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV), Field emission scanning electron microscope (FESEM) and Point zero charge (PZC). This hydrogel has been employed for the removal of toxic metal ions from wastewater. The maximum percentage removal has been found to be 97.5 (±4.87)% for Cu2+ ions and 96.1 (±4.80)% for Co2+ ions under optimum pH 6. The calculated adsorption capacities have been found to be 330.03 (±35.3) mg/g for Cu2+ ions and 325.73 (±22.4) mg/g for Co2+ ions using the Langmuir Adsorption isotherm model. The thermodynamic parameters depicted that the process was endothermic, and spontaneous. The adsorption kinetics data shows excellent fit with pseudo-second-order kinetic model. The synthesized hydrogel exhibits a high swelling ratio of 846.85 (±42.36) g/g and retention ratio of 50.12 (±2.50) % in distilled water. Also, the synthesized hydrogel showed good reusability, exhibiting percentage removal 83.2% for Cu2+ ions and 81.3% for Co2+ ions in the fifth cycle.

Comparative adsorption of selected pesticides from aqueous solutions by activated carbon and biochar

ABSTRACT This work aimed to determine activated carbon (AC) and hard wood derived biochar (BC) adsorption capacity for the uptake of four pesticides atrazine, chlorothalanil, α-endosulfan and β-endosulfan from aqueous solution by conducting batch experiments under different experimental conditions. Structural properties of AC and BC were determined through ‘SEM (Scanning Electron Microscope), FTIR (Fourier Transform Infrared Spectrometer) and XRD (X-ray Powder Diffraction Spectroscopy)’. The optimized pH, particle size, contact time, agitation speed and initial pesticides concentration for the maximum adsorption rates were found to be 7, 250 μm, 60 min, 180 rpm and 12 μgL−¹ respectively. Pesticides adsorption were enhanced by increasing pH to 7 while slight decrease were noted when pH increases from 7 to 9. The adsorption equilibrium data were well described by the Langmuir isotherm model having a significant correlation coefficient value from 0.9999 to 1. Adsorption kinetic data were well fitted with the Lagergren's Pseudo-Second-Order kinetic model. The standard Gibb's free energy (ΔG) negative value at every temperature shows the practicability and spontaneity of the adsorption process. While the negative value for enthalpy change (ΔH) indicated the collective impact of exothermic adsorptions process with randomness intensifying due to positive entropy change.

Sctudies on adsorption of Brilliant Green from aqueous solution onto nutraceutical industrial pepper seed spent

The study proposed the removal of Brilliant Green, a cationic dye, by adsorption process from wastewater solution utilizing a low-cost adsorbent such as Nutraceutical Industrial Pepper Seed Spent (NIPSS). The study comprises an investigation of the parametric influence on the adsorption process. The parameters identified are pH, dye concentration, process temperature, quantity of the adsorbent, and particle size. The study of statistics found from experiments was carried out by incorporating Freundlich, Brouers-Sotolongo, Langmuir, Toth, Sips, Jovanovic, and Redlich-Peterson isotherm models. The adsorption kinetics were determined by implementing pseudo-first-order and second-order models, diffusion film models, and Dumwald-Wagner and Weber-Morris models. The experimental adsorption capacity qe was found to be about 130 mg/g. This value was closest to the maximum adsorption of 144.6mg/g predicted by the Brouers-Sotolongo isotherm which had a correlation coefficient (R2) of 0.998. The adsorption kinetics data was confirmed to be a pseudo-second-order model. The change in free energy, enthalpy change, and entropy change were vital thermodynamic factors in concluding that adsorption is almost spontaneous and endothermic process. Change in enthalpy (ΔH°) reduced value indicates the physical nature of the process. The adsorption of BG dye on the adsorbent surface was authenticated by FTIR spectroscopy and SEM imaging. A Central Composite Design (CCD) Quadratic model under Response Surface Methodology (RSM) was implemented for statistical optimization of adsorption capacity for the five parameters studied, namely, time, temperature, concentration of the dye, weight of the adsorbent, and pH. Software Design Expert 7.0 was used to evaluate 3D contour plots. The process of optimization yielded a value of 350 mg/g. Thus, incrementing the adsorption process by 84.2 %. The study provides insights on various dye and adsorbent interaction possibilities and derives that NIPSS is an efficient adsorbent to extract BG dye from wastewater solutions.

Feasibility of vanadium ion adsorption/desorption using nickel–aluminum complex hydroxides with different molar ratios

Herein, metal complex hydroxides containing nickel (Ni) and aluminum (Al) at different molar ratios (Ni:Al = 1:1 (NA11), 1:2 (NA12), 2:1 (NA21), 3:1 (NA31), and 4:1 (NA41)) were prepared. Scanning electron microscopy images, X-ray diffraction patterns, specific surface area, number of hydroxyl groups, and pHpzc were evaluated. Further, the adsorption capacity of vanadium ions was assessed, with NA21 showing a high potential to adsorb vanadium ions from the aqueous phase (177.5 mg/g). In addition, the effects of various factors, including pH, contact time, initial concentration, and temperature, on the adsorption of vanadium ions were demonstrated in this study using NA21. The optimal pH value for adsorbing vanadium ions was 5.0. Adsorption isotherms and kinetic data were fitted to a pseudo-second-order model (correlation coefficient: 0.958) and a Freundlich model (correlation coefficient: 0.930–0.982), respectively. This study elucidated that a part of the adsorption mechanism of vanadium was related to ion exchange and characteristics of NA21 surface. Moreover, NA21 showed capability to selectively adsorb vanadium ions from binary solution system containing chloride, nitrate, or sulfate ions. Vanadium ions adsorbed onto NA21 were more easily desorbed by a sodium hydroxide solution than a sodium sulfate solution. NA21 demonstrated consistent performance over at least three adsorption and desorption cycles under experimental conditions of this study. These findings provided valuable insights into the recovery of vanadium ions from aqueous media via adsorption/desorption treatment using NA21.

Concurrent removal of Fe(II), Cu(II), and Zn(II) cations from acid mine drainage by an industrial solid waste - steel slag: Behaviors and mechanisms

Acid mine drainage (AMD) contamination poses a severe environmental threat and is a significant risk to human health. There is an urgent need to develop environmentally sustainable and technically viable solutions for water contamination caused by heavy metals. In this study, steel slag (SS) was used as a secondary resource to concurrently remove Fe(II), Cu(II), and Zn(II) from AMD. Because of the loose and porous structure, abundant functional groups, fast sedimentation velocity, and excellent solid-liquid separation, SS showed exceptional removal performance for heavy metal ions. The adsorption kinetic data of Fe(II), Cu(II), and Zn(II) showed good regression with the pseudo-second-order model. Besides, the adsorption of Fe(II) by SS conformed to the Freundlich model, whereas the adsorption of Cu(II) and Zn(II) followed the Langmuir model, with the maximum adsorption amounts of Cu(II) and Zn(II) being 170.69 and 155.98 mg/g. Furthermore, competitive adsorption was observed among Fe (II), Cu (II), and Zn (II) in a multi-component system, with the adsorption priority being Fe (II) > Cu (II) > Zn (II). The removal mechanism of Fe(II), Cu(II), and Zn(II) in AMD by SS mainly includes electrostatic attraction, chemical precipitation, and surface complexation. Interestingly, the leached concentrations of Fe(II), Cu(II), and Zn(II) from the spent slag after calcination were all within the detection limit of the Chinese emission standard, demonstrating excellent environmental stability. Theoretically, this renders it a viable candidate for use as an additive in construction materials. Meaningfully, the work offers a practical approach for energy-efficient and eco-friendly heavy metal ions adsorption, and the secondary utilization of SS also contributes to the sustainable development of the steel industry. It is beneficial to implement the development concepts of clean production and efficient utilization of industrial solid waste.

Comparison of the natural and surfactant-modified zeolites in the adsorption efficiency of sunset yellow food dye from aqueous solutions

The removal of Sunset Yellow (E110) on natural zeolite and zeolite modified with the cationic surfactant cetyl pyridinium chloride (CPC) was studied using the adsorption method. The structural characteristics of the surfactant-modified zeolite (SMZ-CPC) were investigated using X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) analysis, and the scanning electron microscopy (SEM) images. The effect of different parameters on the adsorption process, such as equilibration time and amount of adsorbent at 298 K, were determined using UV–Vis spectroscopy. The maximum dye removal percentage on SMZ-CPC was obtained with 0.08 g of adsorbent in 30 min. The results show that the zeolite modified with CPC surfactant (SMZ) has a higher adsorption capacity for Sunset Yellow than the unmodified zeolite (natural form). The experimental adsorption data were nonlinearly analyzed using isotherm equations such as Langmuir, Freundlich, Temkin, Langmuir-Freundlich (or Sips), and Extended Langmuir (EL). The experimental data were better fitted with the Sips isotherm. The adsorption kinetic data were analyzed using eight models in nonlinear forms: the pseudo-first-order (PFO), pseudo-second-order (PSO), integrated kinetic Langmuir (IKL), Elovich, intraparticle diffusion (IPD), mixed order rate equation (MOE), fractal-like pseudo-first-order (FL-PFO) and fractal-like pseudo-second-order (FL-PSO). According to the results of the coefficient of determination (R2), Elovich kinetic model well expressed E110 adsorption onto SMZ-CPC. Most of the dye removal takes place in less than 5 min and the maximum adsorption capacity is 5.06 mg/g. The results of this study show that zeolite modified with cationic surfactant is an effective adsorbent for removal anionic dyes from an aqueous solution.

Adsorption Behavior and Mechanism of Brilliant Green Dye onto Acid-modified Mesoporous Volcanic Pumice

Water pollution is a major problem in the environment. The important one is the dying effluent from the textile industry. Dye effluent has affected human health and aquatic life. Recently, natural adsorbents have been most commonly used for dye treatment wastewater. This study explores the adsorption mechanism of brilliant green onto HCl-modified pumice. It involves a comparative analysis of the raw and HCl-modified pumice's characterization and adsorption properties. The adsorption experiments were carried out by considering several parameters, such as pH, contact time, initial dye concentrations, and temperatures. The research indicated that the raw and acid-treated pumice possess Si-OH and Si-O-Si groups. These pumice adsorbents are classified as mesoporous, exhibiting BJH pore diameters of 3.23 nm for the raw form and 3.69 nm for the acid-modified variant. The adsorption data revealed that the uptake of brilliant green dye was maximal at a pH of 8. The equilibrium results closely matched the Langmuir isotherm model. The maximum adsorption capacities were 37.13, 40.17, and 42.73 mg g-1 for the raw pumice, and 46.72, 51.81, and 56.17 mg g-1 for the modified pumice at 20, 30, and 40 °C, respectively. Furthermore, the removal efficiency of brilliant green dye with modified pumice was 91.93%, 95.29%, and 96.27% at 20°C, 30°C, and 40°C, respectively. The pseudo-second-order model was the most suitable for elucidating the kinetic adsorption data. The thermodynamic analysis revealed that the adsorption process was endothermic, spontaneous, and physical. Dipole-dipole H-bonding interaction, Yoshida H-bonding, electrostatic interaction, n-𝝅 interaction, cation exchange, and pore filling were all engaged in its process. Consequently, the local pumice volcanic rock became a great, cheap, abundant, and environmentally friendly adsorbent for removing dyes from effluents.

Reactive Blue MEBF 222 dye and textile wastewater treatment using metal-doped cobalt and nickel perovskites by batch and column adsorption process.

Water contamination is a serious issue that has an impact on the whole globe. In the current work, adsorption technique was used to remove synthetic Reactive Blue MEBF 222 textile dye utilizing Cd-doped Co (Co1-xCd1.5xFeO3), Zn-doped Co (Co1-xZn1.5xFeO3), Cr-doped Co (Co1-xCr1.5xFeO3), Zn-doped Ni (Ni1-xZn1.5xFeO3), and Cr-doped Ni (Ni1-xCr1.5xFeO3) perovskites, synthesized by sol-gel auto-combustion approach. According to the findings of batch adsorption studies, maximum adsorption was observed at pH 3 (45.62mg/g), 0.01g/50ml dosage (36.67mg/g), 60min (14.31mg/g), 100ppm dye concentration (47.41mg/g), and 308K (35.96mg/g) for Co1-xCd1.5xFeO3; at 3 pH (42.94mg/g), 0.01g/50ml dosage (35.33mg/g), 60min (12.88mg/g), 100ppm dye concentration (40.52mg/g), and 308K (31.31mg/g) for Co1-xZn1.5xFeO3; at 2 pH (38.82mg/g), 0.01g/50ml dosage (32.20mg/g), 60min (11.98mg/g), 100ppm dye concentration (33.54mg/g), and 308K (29.34mg/g) for Co1-xCr1.5xFeO3; at 2 pH (34.97mg/g), 0.01g/50ml dosage (30.41mg/g), 60min (10.46mg/g), 100ppm dye concentration (27.19mg/g), and 308K (26.12mg/g) for Ni1-xZn1.5xFeO3; and at 2 pH (31.22mg/g), 0.01g/50ml dosage (25.04mg/g), 60min (9.48mg/g), 100ppm dye concentration (21.73mg/g), and 308K (23.61mg/g) for Ni1-xCr1.5xFeO3. The pseudo-second-order model showed good fitness for adsorption kinetic data. Electrolytes, detergents/surfactants, and heavy metal ions had a substantial impact on the adsorption potential. The column adsorption experiments demonstrated optimal bed height, flow rate, and intake dye concentration to be 3cm, 1.8ml/min, and 70mg/l, respectively, in the column experiment. With an adsorption capacity of 44.1mg/g, reactive blue (RB) 222 dye was able to achieve its maximum adsorption. Detailed desorption of RB 222 dye was also achieved. The novelty of this adsorption method lies in its eco-friendliness, ease of handling, and cost-effectiveness.

Adsorption of methylene blue onto clay/carbon composite: kinetics and isotherms study

ABSTRACT Waste treatment for pollution control is a hot topic being studied and has received growing attention. In this study, spent bleaching earth (SBE), a waste material from the oil refineries, was pyrolyzed in a N2 atmosphere to produce an environmentally sustainable clay/carbon composite (SBE@C (500 °C)). SBE@C (500 °C) was tested for its ability to remove methylene blue (MB) from water. The Langmuir model best explained the adsorption isotherms, with maximum adsorption capacity of 29.54 mg/g (MB solution (10–60 mg/L)). The pseudo-second-order kinetic model effectively described the adsorption kinetics data. Thermodynamic parameters indicated spontaneous and endothermic processes. The impact of coexisting cations on MB adsorption by SBE@C (500 °C) decreased in the following order: Fe3+ > Al3+ > Mg2+ > K+ > Na+. The ionic strength results indicated that increasing the concentration of Na+ ions led to a decrease in adsorption capacity. MB removal was greatest at pH level of 8. The adsorption mechanisms involved π–π interactions, electrostatic interactions, and changes in physicochemical properties. After 3 cycles, SBE@C (500 °C) may be recycled up to 11 times before completely losing its adsorption capacity. Overall, SBE@C (500 °C) shows promise for removing MB from wastewater, while mitigating secondary pollution from SBE.

Synergistic ionic liquid encapsulated MIL-101 (Cr) metal-organic frameworks for an innovative adsorption desalination system

The transformations of brackish water into freshwater employing porous materials such as metal-organic frameworks (MOFs) show a great potential for a green environment. But the adsorption-based desalination slows down due to slow water adsorption/desorption rates and inadequate water storage capacity in conventional adsorbents. Therefore, the restructuring of porous MOFs increases water storage and transfer rates. This paper presents a comprehensive investigation on the fabrication of ionic liquid encapsulated MIL-101 (Cr) MOFs (metal-organic frameworks), and its interactions with water for desalination applications. Firstly, the pristine MIL-101 (Cr) is encapsulated with various types/amounts of ionic liquids. Next, these MOFs are characterized via SEM (Scanning electron microscope), FTIR (Fourier transform infrared), XRD (X-ray diffraction), TGA (Thermal gravimetric analysis), N2 adsorption techniques. The water adsorption on these MOFs is performed experimentally for a wide temperature (30–80 °C) and pressure (0 < P/Ps < 0.95) ranges. The effects of the size (or type) as well as the encapsulation ratio of ionic liquids on water adsorption behaviors are conducted. Based on the experimentally proven water adsorption (isotherms and kinetics) data, an AD (adsorption desalination) system is modelled and simulated. Finally, the AD performances in terms of the specific daily water production (SDWP) and performance ratio (PR) are parametrically studied with respect to various regeneration temperature (50–80 °C) and cycle times (100 s–1000 s). It is found that by ionic liquid encapsulation, the water uptakes/offtake rates are expedited up to 48% (for adsorption)/55% (for desorption), respectively. In addition, the water transfer (Δq) improves up to 45% more than the parent MIL-101(Cr) MOFs. Furthermore, the SDWP increases from 38 to 56 m3 of water per tonne of MOFs per day at the regeneration temperature of 70 °C. The simulation results also show that the ionic-liquid-encapsulated MIL-101 (Cr) MOFs generates water (>25 m3 water per tonne of IL-MOFs) at the regeneration temperature of 50 °C and is potential for the next generation desalination applications.

Removal of sulphur and nitrogen compounds from model fuel by adsorption of modified activated carbon

This study aimed to achieve the highest percentage removal of dibenzothiophene (DBT), quinoline (QUI), and indole (IND) adsorbed by double-impregnated modified activated carbon (MAC). Modification of commercial activated carbon (AC) by sulphuric acid (H2SO4) of 15%, 30%, 45%, 60%, and 75% w/v followed by subsequent 1 zinc chloride (ZnCl2): 1 AC impregnation ratio and activated at 500 oC in a muffle furnace under self-generated atmosphere for an hour. The determination of optimized MAC was identified through the highest removal rate of DBT, QUI, and IND from adsorption experiments which were analysed using an ultraviolet-visible (UV-Vis) spectrophotometer. It was found that DBT and IND showed a removal high percentage of up to 86.23% and 82.77% respectively by using 75% H2SO4 with ZnCl2 MAC. Meanwhile, QUI favoured 30% H2SO4 with ZnCl2 MAC with a removal percentage of 33.17% which was still higher than unmodified AC. Physical and chemical properties such as the morphological structure, elemental analysis, porosity, pore size, surface functional group, percentage yield, pH, bulk density, content, ash content, and iodine number were studied for the optimized MAC. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to characterize the MAC. Both MACs showed high percentage yields of 72.08% and 71.13% for 30% and 75% H2SO4 and ZnCl2 MAC respectively. Meanwhile, the pH was between the ranges of 5.36-5.53 for both MACs. Bulk densities were also favourable while the moisture and ash content were within acceptable limits. Iodine numbers for 30% and 75% H2SO4 and ZnCl2 MAC were 857 and 861 mg/g respectively, hence indicating that the MAC achieved high porosity and good adsorption performance. Langmuir, Freundlich, and Temkin adsorption isotherm models as well as pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models were considered for understanding the adsorption mechanisms. The study revealed that DBT, QUI, and IND removal processes, followed the Langmuir adsorption isotherm model with correlation coefficients, R2 of 0.9905, 0.9791, and 0.9964 respectively. Moreover, the adsorption kinetic data of DBT, QUI, and IND provided a better fitting to the PSO kinetic model with R2 of 0.9992, 0.9987, and 0.9998 respectively. According to the Langmuir isotherm model and PSO kinetic model, the adsorption mechanisms of DBT QUI and IND were chemisorbed under monolayer formations.

The effect of adsorbent shaping on the equilibrium and kinetic CO2 adsorption properties of ZIF-8

To be used at scale, adsorbents must be shaped into macroscopic objects, e.g. pellets, granules, and monoliths. Shaping may involve various processing steps and additives that collectively contribute to the final equilibrium and kinetic sorption properties of the adsorbent. Understanding the fundamental links between these processing steps and the resulting sorption performance is needed to rationalise the design of shaped adsorbents. Our study aims to advance the state of knowledge in this area. By focusing on ZIF-8, a prototypical metal organic framework (MOF), and CO2, a common small gas adsorbate, we compared a commercial binderless ZIF-8 extrudate and two purpose-made ZIF-8 pellets shaped with a blend of binders. We used analytical, spectroscopic, and imaging techniques to characterise the samples’ chemical, textural, and morphological properties. In addition, we collected equilibrium and kinetic CO2 adsorption data at 283, 293, and 303 K and up to 1 bar. The binderless ZIF-8 extrudate exhibited a homogeneous structure with BET area, micro- and meso-porosity only slightly reduced compared to ZIF-8 powder. The ZIF-8 pellets also maintained the overall BET area of the ZIF-8 powder, but displayed enhanced macroporosity and skeletal density as well as reduced microporosity – features that likely result from the pressure-induced strains of pelletisation. The extrudates are much less mechanically robust than the pellets. All samples displayed CO2 adsorption capacity in line with the CO2 uptake of their respective components. The CO2 kinetics measurements reveal clear distinctions between binderless ZIF-8 extrudate and ZIF-8 pellets, the latter indicating a behaviour associated with the additional presence of macropores. Our study presents quantifiable evidence for the effect of adsorbent shaping on gas adsorption equilibria and kinetics, providing a valuable resource for preliminary process design.

Rapid and efficient adsorption of p-nitrophenol over biomass-derived vertically aligned graphene nanosheets fabricated by hydrothermal/molten salt-assisted pyrolysis method

Vertical graphene (VG) is an emerging three-dimensional graphene with unique structure and properties, which is expected to possess outstanding adsorption performance. Nevertheless, the utilization of VG as an adsorbent has not been investigated, and its conventional preparation methods are complex and expensive. Herein, we utilize a facile hydrothermal/ molten K2CO3-assisted pyrolysis method for preparing VG from cost-effective and renewable fir bark. The optimized VG-1.0 achieved a high adsorption capacity (556 mg/g) for p-nitrophenol (PNP) within 10 min, far superior to commercial activated carbon (360 mg/g) and previously reported graphene-based materials. Its excellent performance can be ascribed to high specific surface area (1423 m2/g), open & vertical channels, rich oxygen-containing groups and high graphitization degree, providing sufficient adsorption sites and unhindered mass transfer pathways. VG-1.0 was easily regenerated by rinsing with NaOH solution and showed good reusability, maintaining > 80 % of its original adsorption capacity after 5 cycles of reuse. The adsorption isotherm and kinetic data of PNP over VG were fitted well with Freundlich/Temkin model and pseudo-second-order kinetic model, respectively. Various characterizations and density functional theory (DFT) simulations have confirmed that the adsorption of PNP on VG is a spontaneous and endothermic process, involving pore filling and surface adsorption such as hydrogen bonding and π-π interactions.

The selective adsorption of Ni2+ over Co2+ from aqueous solutions in surface functionalized metal–organic frameworks

In this study, two metal-organic frameworks (MOFs), zirconium (IV)-based MOF-808 and chromium (III)-based MIL-101 were investigated for the selective adsorption of nickel (Ni2+) over cobalt (Co2+) and the role of the nitrogen (N)-containing functional groups was evaluated using pyrazole (PyC) and amine (–NH2). Selective adsorption and adsorption rates were quantified using batch adsorption experiments. The post-reaction MOFs after Co2+ and Ni2+ adsorption were characterized with attenuated total reflectance Fourier transform infrared (ATR-FTIR) and X-ray photoelectron (XPS) spectroscopies to identify the active adsorption sites and to infer the adsorption mechanism. The overall adsorption of Co2+ and Ni2+ by MOF-808 and MIL-101 increased after their surface functionalization with PyC and –NH2. However, selective Ni2+ adsorption was only observed with MOF-808-PyC. The pseudo-second-order model fit to the kinetic adsorption data suggests chemically driven adsorption of Co2+ and Ni2+ onto all examined MOFs. The ATR-FTIR and XPS analyses of MOFs with adsorbed Co2+ and Ni2+ indicate that the N sites in PyC and –NH2 are the reactive sites. ATR-FTIR analyses of aqueous PyC solutions with metal cations show a greater shift in the N–H vibrational band of PyC when interacting with Ni2+ compared to Co2+, which is linked to a stronger interaction between Ni2+ and PyC, resulting in the Ni2+ selectivity by PyC-functionalized MOF-808. We propose that PyC, as a π-acceptor ligand, exhibits greater affinity for Ni2+ compared to Co2+ due to i) the greater electronegativity of Ni2+ and ii) the greater stability of Ni2+complex with PyC ligand based on the Irving-Williams series and ligand field stabilization energy based on the electron configuration differences between Co2+ (3d7) and Ni2+ (3d8).

Citrus limon peel-based biosynthesis: Lead oxide, zinc oxide, cadmium oxide, and copper oxide nano quantum dots for subtraction of anionic Actas Pink dye (AAPD)

ABSTRACT Adsorption is a highly effective method for wastewater quality adjustment, offering advantages such as low cost and availability of adsorbents. This study investigates the efficient removal of Anionic Actas Pink dye (AAPD), a major contributor to environmental pollution. Green adsorbents including lead oxide (PbO), zinc oxide (ZnO), cadmium oxide (CdO), and copper oxide (CuO) were synthesized via eco-friendly routes for AAPD removal. Maximum adsorption capacities (qe) were observed at pH 7 (PbO, ZnO, CdO) and pH 2 (CuO and native) with values of 83.83 mg/g at 100 ppm, 75.65 mg/g at 100 ppm, 70.50 mg/g 75 ppm, 61.21 mg/g at 150 ppm, and 52.69 mg/g at 150 ppm, respectively, using an adsorbent dose of 0.05 g/50 mL at temperature of 37°C, and 90 min contact time. Adsorption followed Langmuir isotherm for all adsorbents except native, with PbO also fitting Freundlich and Dubinin–Radushkevich isotherms. Kinetics adsorption data supported pseudo-second-order, while thermodynamic analysis indicated spontaneous and exothermic nature. Effects of electrolytes, surfactants, and desorption were also evaluated. Characterization through FTIR, SEM, and XRD confirmed the morphology and functional groups of these nano-quantum dots. Citrus limon peel-based biosynthesis offers sustainable, eco-friendly, and cost-effective alternatives, highlighting their potential for dye adsorption.

Interface properties and applications in laundry of the BS12-SAS mixed systems

In the BS12/SAS mixed systems, the solution exhibits acidity. BS12 can act as a cationic surfactant to form anionic-cationic complexes with SAS. In this study, the surface properties and application characteristics of the BS12/SAS mixed systems were investigated. The static surface tension, dynamic surface tension, and contact angle of BS12, SAS, and their different mixed molar ratios were measured at 25 °C to evaluate interaction parameters, activity coefficient, molar fraction, and thermodynamic variables of surfactants in the mixed micelles. The results demonstrated that the BS12/SAS mixed systems deviated from the ideal state due to the strong molecular attraction between the two components, resulting in a synergistic effect. The mixed systems exhibited higher surface activity and lower critical micelle concentration. Thermodynamic analysis indicated that the spontaneous micellization of binary mixtures of BS12 and SAS occurred through both enthalpy-driven and entropy-driven processes. The adsorption kinetics data revealed that the mixed systems followed a diffusion-adsorption process. Contact angle measurements demonstrated that BS12/SAS possesses superior ability to reduce surface tension, which facilitated rapid droplet diffusion and efficient wetting of the matrix within a short time period. Furthermore, the aggregation behavior of individual surfactants and the two composite systems in aqueous solutions was analyzed using DLS and TEM to investigate their effects on the wetting, emulsification stability, foaming stability, and decontamination capability of liquid paraffin.

Bioremediation of Brilliant Green cationic dye from water using Nutraceutical Industrial Coriander Seed Spent as an adsorbent: adsorption isotherms, kinetic models, and thermodynamic studies.

The article details a feasibility study of removing Brilliant Green (BG), a mutagenic dye from an aqueous solution by adsorption using low-cost coriander seed spent as a by-product in the nutraceutical industry. The study includes an analysis of the parameters that affect the adsorption process. The variables that have been identified include pH, dye concentration, process temperature, adsorbent amount, and particle size of the adsorbent. To obtain information on the adsorption process and to design the mechanism of the adsorption system on experimental equilibrium, 10 isotherm models, namely, Langmuir, Freundlich, Jovanovic, Dubinin-Radushkevich, Sips, Redlich-Peterson, Toth, Vieth-Sladek, Brouers-Sotolongo, and Radke-Prausnitz were applied. It was discovered that the experimental adsorption capacity, qe, was roughly 110mgg-1. The result has a maximum adsorption of 136.17 mgg-1 as predicted by Dubinin-Radushkevich isotherm. Diffusion film models, Dumwald-Wagner and Weber-Morris models, and pseudo-first- and second-order models, were used to determine the adsorption kinetics. It was realized that the adsorption kinetics data fit into a pseudo-second-order model. Thermodynamic analysis with a reduced enthalpy change suggests a physical process. The values of the thermodynamic parameters ΔG0, ΔH0, and ΔS0 demonstrated an endothermic and nearly spontaneous process of adsorption. The small valuation of ΔH0 specifies that the process is physical. FTIR spectroscopy and SEM imaging were used to confirm that the BG dye had been adsorbing on the adsorbent surface. The study concludes that NICSS is an effective adsorbent to extract BG dye from wastewater solutions, offers insights into numerous dye and adsorbent interaction possibilities and indicates that the process can be scaled to fit into the concept of circular economy.

Synthesis of 3D hierarchical flower-like calcium sulfate microspheres for cadmium removal from wastewater

Novel three-dimensional hierarchical flower-like calcium sulfate microspheres (CSMs) were successfully prepared with the assistance of polyethylene glycol, trisodium citrate, and polyacrylic acid. The CSMs were monodispersed as flower-like microspheres constructed from interspersed nanosheets. Their average diameter and Brunauer–Emmett–Teller specific surface area were 15 μm and 16.09 m2/g, respectively. The prepared CSMs were employed as adsorbents in cadmium (Cd(II)) removal from wastewater and their Cd(II) adsorption performances were analyzed. The adsorption kinetic data were best fitted to the pseudo-first-order kinetic model and the experimental isotherm data were precisely fitted to the Freundlich isothermal model. The maximum adsorption capacity of the CSMs could reach up to 18.13 mg/g at 293 K under neutral conditions, affirming the potential utility of the CSMs in Cd(II) removal from wastewater.