Pseudo-second Order Kinetic Model Research Articles

Comparison of two carbonaceous supported Fe-rich adsorbents for arsenate removal: A functionalisation and mechanistic study with applicability to groundwater treatment

The presence of arsenic in groundwater, and through this in drinking water, has been shown to present a serious risk to public health in many regions of the world. In this study, two iron-rich carbonous adsorbents were compared for the removal of arsenate (As(V)) from groundwater. Biochars (FeO-biochar and FeO-pyrochar) derived from biomass waste were functionalised in two different ways with iron chloride for comparation. Batch and dynamic parameters were optimised to achieve >99% As(V) removal efficiency. Experimental data best described by the pseudo-second order kinetic model, while multi-stage diffusion appeared to limit mass transfer of As(V). Among the isotherm models evaluated, the Freundlich model best described the experimental results with high correlation coefficients (R2≥0.94) for both adsorbents. Monolayer adsorption capacities were found to be 4.34 mg/g and 8.66 mg/g for FeO-biochar and FeO-pyrochar, respectively. Batch studies followed by instrumental characterisation of the materials indicated the removal mechanisms involved to be electrostatic interactions (outer-sphere), OH- ligand exchange (inner-sphere complexation) and hydrogen bonding with functional groups. Higher pHpzc (9.1), SBET (167.2 m2/g), iron/elemental content and functionalisation technique (e.g., functionalisation of biochar after pyrolysis instead of biomass) for FeO-pyrochar, compared with FeO-biochar, suggested that both the surface chemistry and porosity/surface were important in adsorption. Dynamic studies showed FeO-pyrochar can be used to remove As(V) from groundwater even at low ‘environmental’ concentrations to legislative limit (<10 μg/L), where 7 g of FeO-pyrochar was able to treat 5.4 L groundwater.

Cost-effective synthesis of magnetic graphene oxide nanocomposites from waste battery for the removal of arsenic from aqueous solutions: Adsorption mechanism with DFT calculation

In this study, magnetic graphene oxide (MGO-Fe3O4) nanocomposite was prepared by co-precipitating of FeCl3-6H2O and FeCl2-4H2O on waste battery-derived graphene oxide and used as an adsorbent for the efficient removal of As(III) from aqueous solutions. The prepared nanocomposite was characterized by Fourier transformed infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, zeta potential, and a vibrating sample magnetometer. These characterizations revealed that spare like Fe3O4 nanoparticles (10.5 nm) were decorated on graphene oxide nanosheets and showed excellent saturation magnetization (89.73 emu/g). The adsorption of As(III) by MGO-Fe3O4 was optimized by analyzing various parameters. Experiments showed that 98 % of As(III) was removed at neutral pH in a just 20 min, even though the adsorbent dose was only 0.14 g/L. The adsorption kinetic and isotherm were best fitted with the pseudo-second order kinetic and Frendlich isotherm model. The maximum adsorption capacity (qmax) was found to be 50.2 mg/g at room temperature. Thermodynamic studies showed that the As(III) adsorption process was spontaneous and exothermic in nature. The enhanced adsorption capacity and magnetic properties of MGO-Fe3O4 are crucial in the drinking water treatment process due to the easy magnetic separation of MGO-Fe3O4 from aqueous solution after the adsorption process. Density Functional Theory (DFT) was also used to investigate the interaction between MGO-Fe3O4 and As(III), which further suggested that MGO-Fe3O4 and As(III) mostly interact with each other through surface complexation and hydrogen bonding.

UPTAKE OF Co(II), Pb(II) AND Ni(II) IONS BY Annona senegalensis STEM BARK BIOCHAR FROM AQUEOUS SOLUTION: OPTIMIZATION, KINETIC AND THERMODYNAMIC STUDIES

The concern for heavy metal pollution in the environment is especially so since they are non-biodegradable. The use of agro materials in the removal of these heavy metal pollutants has been recognized as a low-cost alternative to the costly conventional remediation techniques. The equilibrium sorption of the chemically activated Anonna senegalensis stem bark was investigated. Using standard techniques, the physicochemical properties of activated carbon (MAASC) were ascertained. By using a simultaneous batch adsorption approach, the adsorption of Co2+, Pb2+, and Ni2+ onto MAASC was examined as a function of pH, solution temperature, initial metal ion concentration, agitation time, adsorbent dose, particle size, and carbonization temperature. The equilibrium sorption data generated were fitted into Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models as well as pseudo first-order, pseudo-second-order and intraparticle diffusion kinetic models. From the obtained results, it was discovered that the Langmuir isotherm provided the best match conformation of all the models, except for Pb2+, which was best for Freundlich with an R2 of 0.95. Physisorption was shown to be the mechanism by Dubinin-Radushkevich. For Co2+, Pb2+, and Ni2+, respectively, the pseudo second-order kinetic model had R2 values of 0.997, 0.999, and 0.999 that best matched the data. Both intraparticle diffusion and the boundary layer effect also contributed to regulating the rates of the adsorption process. The study's thermodynamic results showed that Ho for Co2+, Pb2+, and Ni2+ were 27.51, 19.70, and 13.37 KJ/mol, respectively. These values are all positive and suggest an endothermic reaction, supporting the physisorption mechanism.

Removal of Humic Acid from Water by Adsorption Using Chitosan and Metal Organic Framework ZIF 8 Loaded Chitosan Adsorbents

Water is the most necessary need for life on the earth. There are a lot of organic pollutants in water. One of the organic pollutants is natural organic substances. Humic acid, a natural organic substance, turns into very harmful substances along with other pollutants. In this study, the humic acid removal from aqueous solution by adsorption using chitosan and chitosan/ZIF 8 composite spheres was examined. Chitosan spheres cross-linked with epichlorohydrin (ECH) and composite spheres consisting of metal organic framework ZIF8 and chitosan were prepared as adsorbents. Equilibrium, kinetic, and thermodynamic studies were investigated for humic acid adsorption by pristine chitosan-ECH and composite chitosan/ZIF 8 adsorbents. Chemical adsorption was found to be compatible with the Freundlich isotherm model and the pseudo-first-order kinetic model for pure chitosan adsorbents. Studies were carried out using chitosan/ZIF8 composite adsorbent, and the most suitable models for chemical adsorption were determined as Langmuir isotherm and pseudo-second order kinetic model. The response surface method was applied with the design expert program to determine the optimum experimental conditions. The adsorption tests were carried out using chitosan-ECH, ZIF 8 and chitosan/ZIF 8 adsorbents for specified optimum conditions, and the humic acid removal was determined as 95.1%, 98.3%, and 97.3%, respectively. In addition, desorption was performed using chitosan-ECH and chitosan/ZIF 8 spheres, and the desorption efficiency was found to be 20.9% and 82.5%, respectively. It has been observed that the developed adsorbents have potential in removing humic acid from water.

By-product Eucalyptus leaves valorization in the basic dye adsorption: kinetic equilibrium and thermodynamic study

Abstract Algerian Eucalyptus Leaves (AEL), a natural biodegradable adsorbent abundantly available, was used for the removal of methylene blue (MB) dye. The AEL properties for the removal of MB were investigated under different conditions by varying the AEL amount, MB concentration, pH of the solution and the reaction temperature. Scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) techniques have been used to characterize AEL biosorbent. Experimental results showed that the adsorption of MB dye at the concentration of 50 mg L−1 reached to 91 % at pH 10 with a stirring speed of 200 rpm and after 180 min of reaction time. The experimental data were analyzed using the linear forms of different kinetic models (pseudo-first order kinetic model, pseudo-second order kinetic model, and intra-particle diffusion models). The results demonstrated that the adsorption kinetics of MB was consistent with the pseudo-second order model with R 2 value of 0.9969. The isotherm models Langmuir, Freundlich, Dubinin, Elovich, Brunaut Emmet Teller and Temkin models were also investigated to describe the adsorption equilibrium. The results show that the AEL adsorption is in accordance with Temkin isotherm. The thermodynamic study revealed that the adsorption is spontaneous and exothermic. Therefore, as a cheap green adsorbent with high MB adsorption performance, AEL is expected to become one of the best candidate materials for future industrial wastewater treatment.

The simultaneous removal of methylene blue (MB) and Ca2+ by recyclable adsorbents based the scales derived from coal gasification system.

The transformation of solid wastes from industrial production into effective adsorbents could significantly contribute to wastewater treatment. In this study, after acidizing and burning soft scale (SS) from coal gasification system, two magnetic adsorbents (mag-ASS and mag-BASS) were prepared via the combination of magnetite with ultrasonic, respectively. The treatment effects of mag-ASS and mag-BASS were then investigated for simulated wastewater containing macromolecular organic matter [i.e., methylene blue (MB)] and Ca2+. The results indicated that the pseudosecondorder kinetic, Elovich, Freundlich,Langmuir and Temkin model could well describe the adsorption behavior of MB and Ca2+ onto mag-ASS and mag-BASS. The maximum adsorption capacities of mag-ASS for MB and mag-BASS for Ca2+ were 600.53mg/g and 102.54mg/g, respectively. Surprisingly, the adsorption abilities of mag-ASS for MB and mag-BASS for Ca2+ showsignificantly higher than the others. The adsorption mechanisms of MB mainly included electrostatic interaction, π-π conjugate interaction and cation exchange, while those of Ca2+ were mainly electrostatic interaction and cation exchange. The diffusion of MB and Ca2+ onto the magnetic adsorbents might be controlled by the combined effects of intraparticle and liquid film diffusion. There was no significant reduction in adsorption capacity after 8 cycles of adsorptionand desorption, indicating that SS-based magnetic adsorbents had good recyclability and stability. Moreover, the removal efficiency of mag-BASS for total hardness and total organic carbon in real coal gasification gray water (CGGW) was 82.60 and 64.10%, respectively. The treatment of CGGW and theresource of wastes would significantly promote the reasonable disposal of coal gasification scales.

Modification of amino functionalized silica nanoparticles with L-proline and furanacrylic acid as novel composites for the efficient removal of methyl orange

The present study deals with the preparation of new composites in which L-proline (LP) and furnacrylic acid (FA) have been grafted on surface of amino functionalized silica nanoparticles (AFS). At first, AFS were prepared by sol-gel approach using tetraethoxysilane (TEOS) as silica source and aminopropyltriethoxysilane (APTES) as silica modifiers. Taking the advantage of amino group on AFS surface, LP and FA were easily grafted on silica surface to obtain LP grafted silica (AFS-LP) and FA grafted silica (AFS-FA) nanocomposites by post modification approach. As prepared composites were characterized by FTIR, SEM, XRD and TGA. The evidence of LP and FA on AFS was elucidated from the FTIR bands found at 1650–1698 cm−1 related to carbonyl group CO) of amide. Additionally, peaks observed at 2965 cm−1 (C-H stretching) of propyl groups and at 1050 cm−1 (Si-O-Si) indicated that the backbone of the material is preserved as silica. The micro images of SEM depicted that the AFS are spherical in shape and have more degree of monodispersivity whereas the SEM images of composites (AFS-LP and AFS-FA) have larger particle size and less degree of monodispersivity. Likewise, XRD peaks at 2θ (∼12°) revealed the mesoporosity of silica as well as hybrid silica and further depression in this peak in case of AFS-LP and AFS-FA depicted the existence of organic moieties on silica. TGA analysis depicted three decomposition steps (high weight loss) in case of AFS-LP and AFS-FA in contrast to two decomposition steps observed in case of AFS. The higher weight loss observed in the case of hybrid composites depicted the grafting of organic molecules on AFS. The prepared composites AFS-LP and AFS-FA were deployed to investigate their adsorption capacity to remove methyl orange (MO) from aqueous media. Experiments revealed that the composites have high adsorption capacity in acidic media (pH=2) with % removal of 85.05 % for AFS-LP and 81.70 % for AFS-FA. The experimental data was evaluated for adsorption isotherms and value of correlation factor (R2) was close to unity in case of Freundlich representing that the adsorption follows Freundlich isotherm. The data was also evaluated for kinetic models and higher values of R2 as well as closeness of experimental and calculated values of Qe predicted that adsorption of MO followed pseudo-second order kinetic model.

Adsorption of phosphate over a novel magnesium-loaded sludge-based biochar.

The production of sludge-based biochar to recover phosphorus (P) from wastewater and reuse the recovered phosphorus as agricultural fertilizer is a preferred process. This article mainly studied the removal of phosphate (PO4-P) from aqueous solution by synthesizing sludge-based biochar (MgSBC-0.1) from anaerobic fermentation sludge treated with magnesium (Mg)-loading-modification, and compared it with unmodified sludge-based biochar (SBC). The physicochemical properties, adsorption efficiency, and adsorption mechanism of MgSBC-0.1 were studied. The results showed that the surface area of MgSBC-0.1 synthesized increased by 5.57 times. The material surface contained MgO, Mg(OH)2, and CaO nanoparticles. MgSBC-0.1 can effectively remove phosphate in the initial solution pH range of 3.00-7.00, with a fitted maximum phosphorus adsorption capacity of 379.52 mg·g-1. The adsorption conforms to the pseudo second-order kinetics model and Langmuir isotherm adsorption curve. The characterization of the adsorbed composite material revealed the contribution of phosphorus crystal deposition and electrostatic attraction to phosphorus absorption.

Synthesis of Na-Alginate templated Montmorillonite-Silica Composite as adsorbent for removal of Rhodamine B

AbstractIn this study, mesoporous Montmorillonite-Silica composites prepared by using different amount Alginate as sacrificial template, for removal of Rhodamine B is investigated. By alternating Alginate amount it is aimed to switch the porosity of adsorbents thus the adsorption capacities of adsorbents. Synthesized adsorbents had been characterized by using Scanning Electron Microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and N2-Ads/Des techniques. It is observed that beside the decrease in the micropore volume, the total pore volume of the adsorbents increased with the increasing of used Alginate amount. The total pore volumes of adsorbents synthesized with different Clay/Alginate ratio (10, 5, 1) were found as 0.116, 0.172, and 0.178 cm3/g, respectively. Batch adsorption studies showed that the maximum removal efficiencies were obtained at acidic conditions and the adsorbents had better fit with Freundlich isotherm. Qm values obtained from Langmuir isotherm were found as 24.47, 31.97 and 28.48 mg/g for synthesized adsorbents. Also, adsorption kinetic studies showed that for all adsorbents, experimental data had good fit to the pseudo-second order kinetics model. The model parameters were found as 5.9,6.3 and 6.5 (10–3 g/ (mg min). Thermodynamic parameters were also investigated in the study. Negative ∆Go values pointed out that the adsorption of RhB onto synthesized adsorbents was favorable process. Positive values of ∆Ho and ΔS indicated that the adsorption of RhB on adsorbents were endothermic and rising of randomness during the adsorption of RhB on the surface of the adsorbent. Adsorbents could be recovered at least five times without significant decrease in adsorption capacity.

Ni2+ removal by ion exchange resins and activated carbon: a benchtop NMR study

AbstractHeavy metal pollution in water is a critical environmental concern, demanding effective remediation techniques. Traditional methods, including ion exchange and adsorption, often rely on inductively coupled plasma (ICP) atomic emission spectroscopy/mass spectrometry (AES/MS) for the indirect and time-consuming measurement of residual metal concentrations. In contrast, this study employs innovative direct monitoring of nickel removal by benchtop NMR relaxometry using the paramagnetic properties of Ni2+. To prove the feasibility of the NMR follow-up of Ni2+ uptake, batch experiments were performed with Amberlite IR120, Amberlite IRC748, Dowex Marathon MSC, and activated carbon (AC), which were previously characterized by various techniques. The effect of contact time, pH, and Ni2+ concentration on removal efficiency were studied. Pseudo-first and pseudo-second order kinetic models were used. The Langmuir model effectively described the equilibrium isotherms. The longitudinal and transverse relaxation curves of the loaded resins were biexponential. For sulfonic resins, a strong correlation was observed between the relaxation rates of the fast-relaxing fraction and the Ni2+ content determined by ICP-AES/MS. For IRC748, the effect of Ni2+ loading on the relaxation rates was weaker because of Ni2+ complexation. The relaxation curves of loaded AC revealed multiple fractions. Centrifugation was employed to eliminate the contribution of intergranular water. The remaining intragranular water contribution was biexponential. For high Ni2+ loadings, the relaxation rates of the slow relaxing fraction increased with the AC Ni2+ content. These results mark the initial stage in developing a column experiment to monitor, in real-time, adsorbent loading by NMR relaxometry.

Sequestration of hazardous alizarin Red S dye from water using mesoporous sponge-PANI composite

In this paper, the performance of the combination of polyaniline, a conductive polymer, and a polyurethane-based dishwashing sponge (sponge/PANI) on the adsorptive removal of Alizarin Red S dye from aqueous solutions was investigated. Firstly, polyurethane-based dishwashing sponges were cut into pieces and then coated by PANI. The sponge/PANI composites were characterized by XRD, SEM-EDX, BET, and FTIR-ATR analysis. Optimum conditions (adsorbent dosage: 0.1 g/50 mL, pH: 6–8, contact time: 120 min, agitation rate: 120 rpm) for adsorption were determined. Adsorption data were applied to different isotherm and kinetic models. According to the isotherm models, Langmuir model was found to be more suitable and the maximum adsorption capacity was found to be 188.68 mg/g at 298 K. According to the adsorption kinetic data, the adsorption process was found to follow the pseudo-second order kinetic model. Meanwhile, from the study on the adsorption mechanism, electrostatic interactions, H-bonding and interlayer force were considered to be the main driving force for adsorption. From the adsorption thermodynamic data, it was found that the adsorption of ARS dye was exothermic ( Δ H o = − 24.00   kJ / mol ) and spontaneous ( Δ G o = − 30.26   kJ / mol at 298   K ). Furthermore, from the reusability studies carried out, it was determined that the prepared adsorbent can be effectively used repeatedly. When the adsorption results were evaluated, it was determined that PANI-coated sponge composites effectively adsorbed Alizarin Red S dye. Moreover, the adsorption efficiency is open to improvement through optimization of surface properties by different methods such as doping.

Efficient removal of the organophosphate pesticide, profenofos using polymer-stabilized microporous Fe2O3-ZnO nanocomposite: Kinetic and thermodynamic analysis

In the contemporary landscape of scientific research, the development of inhibitors for acetylcholinesterase (AChE) holds significance due to their dual application as chemical warfare agents (CWAs) and pesticides. These compounds, whether intentionally deployed for malicious purposes, used in agriculture to combat pests, or accidentally released, pose a substantial threat to humanity. Consequently, there is a dire need to create efficient nanocatalysts capable of eliminating organophosphate toxic substances. This study focuses on the synthesis of a nanocomposite catalyst comprised of polymer-stabilized Fe2O3-ZnO, characterized as porous oval-shaped clusters that exhibit exceptional proficiency in the degradation of the pesticide profenofos (PF). This degradation process is remarkably swift, occurring within a short timeframe under both dark and light conditions. Porosity enhancement was achieved through the combination of polymeric stabilizing agents, namely polyvinylpyrrolidone (PVP) and methyl cellulose (MC). Notably, the highest concentration of profenofos (1825 mg/L) was directly introduced to the Fe2O3-ZnO nanocomposite catalyst. Remarkably, 100 % degradation was achieved within just 60 min in the absence of light, highlighting the feasibility of dark treatment as an effective degradation pathway. The kinetics of the reaction were evaluated using Lagergren pseudo-first order and Ho/McKay pseudo-second order kinetic models, employing varying catalyst doses and profenofos concentrations. The results indicated that the reaction predominantly follows second-order kinetics. Furthermore, thermodynamic parameters, including the change in Gibbs free energy (ΔG), entropy (ΔS), and enthalpy (ΔH), were assessed, revealing the spontaneous and exothermic nature of the reaction. Additionally, a proposed degradation pathway for the chemical warfare agent stimulant, profenofos, was elucidated. To our knowledge, this is the inaugural documentation showcasing the remarkable efficiency of a polymer-stabilized Fe2O3-ZnO nanocomposite catalyst in degrading the organophosphate pesticide, profenofos, achieving rapid degradation rates even under dark conditions. The findings contribute to the advancement of catalytic materials for environmental remediation and provide important insights into the kinetics, thermodynamics, and degradation pathways of organophosphate compounds.

Adsorptive Removal of Methylene Blue Dye by Annealed Waste Foundry Sand

Under optimized experimental conditions, the efficient removal of methylene blue dye from annealed waste foundry sand as adsorbent was carried out. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FE-SEM) and partical size analysis were used to confirm the crystalline structure, composition and morphology of the prepared sorbent. The sorbent achieved its highest adsorption capacity by interacting with an aqueous solution contaminated with methylene blue dye. A comparison was made between the sorbent and three annealed sands based on their dye removal efficiency adsorption data over time. By using Langmuir and pseudo second-order kinetic models to the sorption data, it is observed that both physical and chemical processes can influence the removal process. According to experimental data, annealed waste foundry sand (WFS-300) has a high adsorption efficiency and methylene blue adsorption follows.

Bioremediation of anthraquinone dye using bimetallic Ni-Zn nanohybrid synthesized from Ficus exasperate leaf extract

This study investigated the synthesis of bimetallic core-shape Ni-Zn nanoparticles using Ficus exasperate leaf extract. The incorporated bimetallic Ni-Zn nanoparticles were applied for the removal of anthraquinone dye from an aqueous solution using various adsorption parameters such as adsorbate concentration, contact time, pH, temperature, and adsorbent dosage. The presence of biomolecule compounds in the aqueous extract of Ficus exasperata was confirmed by a UV-visible spectrophotometer (UV) and Fourier Transform Infrared (FT-IR) Spectrometer. A High-Resolution Transmission Electron Spectrometer revealed a spherical shape whose diameter ranged between 10.67- 30.73 nm with an average particle size of 17.42 nm. The maximum adsorption capacity for Langmuir isotherm (qm ) was found to be 50.08 mg/g with R2 of 0.9994 proving the adsorption isotherm best fit for Langmuir adsorption isotherm. The Pseudo second-order kinetic model best fitted the adsorption process. The results of Gibbs free energy ( Δ G ° ) and enthalpy change ( Δ H ° ) of the adsorption of anthraquinone dye are − 81.48 J/mol/K and −26 kJ/mol indicating a spontaneous and exothermic reaction. The regeneration of the green synthesized Ni-Zn nanoparticles up to the fifth removal cycle at 48.08 mg/g revealed excellent results for the removal of anthraquinone dye from an aqueous solution. The obtained results showed that green synthesized core-shape Ni-Zn nanoparticles are excellent and eco-friendly biomaterials for the removal of anthraquinone dye from an aqueous solution.

Sodium hydroxide/magnesium chloride multistage activated sludge biochar: interfacial chemical behavior and Cd(II) adsorption performance.

To enhance the adsorption performance of municipal sludge biochar on Cd(II), modified sludge biochar was prepared by sodium hydroxide/magnesium chloride (NaOH/MgCl2) graded activation, and the Cd(II) adsorption performance on sludge biochar (BC), NaOH-activated sludge biochar (NBC) and NaOH/MgCl2 activated sludge biochar (NBC-Mg) was investigated. The results showed that NaOH/MgCl2 graded activation upgraded the surface structure and enhanced the graphitization of sludge biochar. The adsorption experiments indicated that the adsorption kinetic and adsorption isotherm for Cd(II) were in accordance with the pseudo second-order kinetic and Langmuir model. The adsorption capacity of NBC-Mg (143.49mg/g) for Cd(II) was higher than that of BC (50.40mg/g) and NBC (85.20mg/g). The mechanism of Cd(II) adsorption included ion exchange, complexation, cation-π interaction, and mineral precipitation. After five regeneration, the removal efficiency of Cd(II) by NBC-Mg remained above 90%. This work indicated that sludge biochar prepared by multistage activation could be an effective material for Cd-containing wastewater treatment.

Synthesis of TiO\(_2\) Impregnated Ribes nigrum Stem Nanoactivated Carbon and their Application to Remove Heavy Metals

Nanoactivated carbons from Ribes nigrum (black currant) stem were prepared using two-step procedure with excellent yield and were characterized using different spectroscopic techniques. The FTIR spectroscopy revealed O-H, C=C, C=N, and C-O stretching. XRD analysis revealed the particle sizes as 29.57 nm for stem activated carbon (SAC) and 26.55 nm for stem activated carbon impregnated with titanium (SAT) while, the morphology of the SAC and SAT were revealed by SEM to be spherical, granular and porous. The prepared nanoactivated materials were used for removal of Pb2+ and Cd2+ from aqueous solution. The influences of initial metal ion concentration, agitation time, adsorbent dose, temperature and pH were studied in batch experiments at room temperature. The adsorption equilibriums were rapid at 60 min of agitation for Pb2+ and Cd2+ on SAT with appreciable %removal. The adsorption data for Pb2+ and Cd2+ on SAT fitted well into Freundlich isotherm than Langmuir given correlation coefficient (R2) very close to unity and appreciable maximum adsorption capacity KF &gt; 1.00. The fitting into Freundlich indicates multilayer coverage on the adsorbents. The kinetic studies showed good correlation coefficient for a pseudo-second order kinetic model for the SAT. The enthalpies of the adsorption process are: +12.754 and +18.377 KJ mol-1 for Pb2+ and Cd2+ on SAT respectively. The entropies of the adsorption process were also evaluated and have been found to be +41.805 and +12.151 KJ mol-1 for Pb2+ and Cd2+ on SAT. The results showed that SAT has the potential to be applied as alternative low-cost nanoadsorbents in the remediation of metal contamination in water.

Chemically treated Posidonia oceanica fibers as a potential sorbent for oil spill clean up

Posidonia oceanica (PO) fibers were used as biodegradable solid waste material in the removal of oil spills from seawater. In the present study, PO fibers were chemically treated using H3PO4, KOH, ZnCl2 and H2O2. The Fourier Transform Infrared spectroscopy and scanning electron microscopy were used to compare and to determine the structure of the raw and the chemically-treated PO fibers. The main parameters studied in the two systems, a mixture system of oil and water and a system with only oil or only water, were the chemical solutions concentrations, initial oil concentration and time contact. The results revealed that PO fibers treated with phosphoric acid (H3PO4) showed an enhancement of oil sorption of 12% in oil/water layer, compared to raw PO fibers. An increase of hydrophobicity was also observed with treated fibers as revealed by the 50% decrease in water sorption capacity. The isotherm and kinetic models were determined to reveal the nature and the mechanism of the sorption. Langmuir isotherm appeared to be the best fitting model showing a one-layer oil sorption onto PO fibers. In addition, the results fitted well with the pseudo-second order kinetic model compared to pseudo-first order representing the chemical sorption of oil. The results indicated that the treated biosorbent could be used as biodegradable material to clean-up oil spills in aqueous solution.

Adsorption and Desorption Behavior of Partially Hydrolyzed Polyacrylamide on Longmaxi Shale

Large-scale volumetric fracturing is generally used during shale gas development. The return rate of fracturing fluid is low, and a large amount of slickwater is retained in the reservoir. The adsorption and desorption of partially hydrolyzed polyacrylamide (HPAM), an additive commonly used in slickwater, on the surface of shale was studied using Longmaxi shale from the Sichuan Basin. The experimental results showed that the mass ratio of the HPAM solution to shale reached saturation adsorption at 20:1 when the concentration of HPAM solution was 1000 mg/L and 25:1 when the concentration of HPAM solution was 500 mg/L. The mass ratio of the HPAM solution to shale was fixed at 25:1, and the adsorption equilibrium was reached at a HPAM concentration of 1000 mg/L when the aqueous solution temperature was 30 °C and 800 mg/L when the aqueous solution temperature was 60 °C. The Langmuir adsorption model yielded a better fit than the Freundlich adsorption model. The adsorption equilibrium time at 30 °C was at 60 min for a HPAM concentration of 500 mg/L, while for a concentration of 1000 mg/L, it was at 90 min. The adsorption equilibrium time at 60 °C was 40 min for a HPAM concentration of 500 mg/L, whereas it was 60 min for a HPAM concentration at 1000 mg/L. The pseudo-second order (PSO) kinetics model yielded better fits than the pseudo-first order (PFO) kinetics model. The adsorption of HPAM on shale was strong, and the adsorbed HPAM resembled cobwebs adhering to the shale surface. HPAM on the surface of shale after adsorption was able to resist the desorption capacity of water. However, when the amount of adsorbed HPAM on shale increased significantly, the amount of residual HPAM on the surface of the shale decreased rapidly during desorption in deionized water. The desorption of HPAM on the shale surface followed a modified desorption model. The higher the concentration of HPAM adsorbed on the shale surface was, the easier it was to desorb and the easier it was to be removed from the shale.

Adsorptive removal of heavy metal ions from aqueous solution by using green synthesized copper oxide nanoparticles

Metal nanoparticles can be synthesized by “green synthesis” methods, an efficient and environmentally friendly process that involves combination of metal salt solution with plant extract. Due to low cost, ideal surface area, plenty of active sites, and high adsorption capabilities, copper oxide nanoparticles (CuO-NPs) have drawn a lot of attention as effective adsorbents. Our present study is primarily concerned about green synthesis route of producing copper oxide nanoparticles (CuO-NPs) from flower extract of Nyctanthesarbor-tristis. The prepared CuO-NPs was used in the adsorption of toxic metal ions including U(VI), Pb(II), Cr(VI), and Cd(II) from water samples was studied. Different analytical techniques like UV-visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy has been used for analyzing the properties of prepared copper oxide nanoparticles. A batch experiment has also been conducted to determine the efficacy of the synthesized copper oxide nanoparticles toward the adsorption of toxic metal ions including U(VI), Pb(II), Cr(VI), and Cd(II) from water samples at various parameters, such as the impact of pH, contact time and adsorbent dosage. According to the results, the adsorption capacity (qmax) of CuO-NPs for U(VI), Pb(II), Cr(VI), and Cd(II) metal ions are 200, 155.27, 131.57 and 90.90 respectively. The kinetic studies showed that the pseudo-second order kinetics model has best fits to the data (R2= 0.85, 0.91, 0.89, 0.92 for U(VI), Pb(II), Cr(VI), and Cd(II) respectively. The study also included pseudo-first order, Elovich models and intra particle diffusion. In light of these findings, copper oxide nanoparticles were found to be a promising nano-adsorbent for the treatment of water.

High efficiency simultaneous adsorption of rare earth elements from aqueous solutions using carbon xerogel-chitosan composite

ABSTRACT This study investigated the simultaneous sorption of rare earth elements (REEs) from acidic media using carbon xerogel functionalised with chitosan. The combined carbon xerogel with chitosan that was synthesised has a sphere-like structure and a larger BET surface area (275 m2 g−1) than pure carbon xerogel alone (228 m2 g−1). To determine the optimal conditions, adsorption of REEs was established under different variables, including pH, contact time, initial concentration, adsorbent wt. and temperature, as well as desorption experiments. The adsorption isotherms showed that both the Freundlich and Langmuir models were followed, in addition to a pseudo-second order kinetic model. The adsorption is likely exothermic, which confirms it is favourable at low temperatures, and a dissociative adsorption process is involved, according to analysis of thermodynamic state functions. Langmuir calculations revealed that the maximum amount of REEs that were adsorbed was 164 mg/g. Because of its superior adsorption capacity and simplicity in using a recycled material following several desorption cycles, carbon xerogel-chitosan is being employed as a novel adsorbent material to remove REEs from aqueous solutions.