Freundlich Adsorption Isotherm Research Articles

Adsorptive removal of malachite green using novel GO@ZnO-NiFe2O4-αAl2O3 nanocomposites

The performance of a newly prepared nanocomposite adsorbent containing nickel ferrite, zinc oxide and alpha alumina nanoparticles onto graphene oxide substrate was investigated for the adsorptive removal of malachite green. The composites were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM) and BET techniques. The results confirmed the presence of particles in the composites and structure of constituent particles in the composite was better preserved in COM4. The effect of pH (from 3 to 9), initial dye concentration (100 to 1500 mg/L), adsorbent mass, temperature (5 to 45 °C) and contact time on adsorption efficiency was examinaed using linear and non-linear adsorption models. Maximum adsorption was observed for linear Langmuir model (607.66 mg/g) at pH 7 under ambient temperature. The contact time showed 73 % of dye adsorption within the first 15 min. Experimental data fitting showed good agreement with Freundlich adsorption isotherm in the pseudo-first-order linear kinetic model as well as the pseudo-second-order nonlinear kinetic model with a correlation coefficient of 0.97. Also, adsorption mechanism was proposed by surface functional groups, electrostatic interactions, H-bonding, π-π interactions, and permeation of MG dye molecules into the pores of the adsorbent. The adsorbent showed good performances up to three cycles after washing with ethanol when compared to acetone and water.

Adsorptive Removal of Dye (Methylene Blue) Organic Pollutant from Water by Pine Tree Leaf Biomass Adsorbent

In this laboratory batch adsorption study, the raw pine tree leaf biomass solid waste adsorbent material was used for the removal of methylene blue (MB) dye from water at different physicochemical process conditions. The characteristics of adsorbents were determined for particle size, surface area, the existence of functional group identification, and the morphology of the adsorbent surface. The adsorption was performed at different process conditions, which include solution pH, dye concentrations, adsorbent doses, and temperature, respectively. In this study, it was found that MB dye adsorption increased with increases in solution pH and adsorbate MB dye concentration but decreased with adsorbent doses and temperature at fixed process conditions. The Langmuir isotherm model was best fitted with the experimental equilibrium data, with a higher linear regression coefficient (R2) value of 99.9% among the two widely used Langmuir and Freundlich adsorption isotherm model equations. The maximum Langmuir monolayer adsorption capacity of raw pine leaf was found to be 36.88 mg/g, which was comparable with other reported adsorbent capacities towards methylene blue (MB) dye adsorption. The value of the separation factor, RL, from the Langmuir isotherm model equation gives an indication of favorable adsorption. Thermodynamic parameters such as standard Gibbs free energy change (ΔG0), standard enthalpy change (ΔH0), and standard entropy change (ΔS0) indicated that the methylene blue (MB) dye adsorption by pine tree leaf biomass was spontaneous and exothermic in nature and that the mechanism of adsorption was mainly physical adsorption. Finally, limitations and future studies are also discussed here. The outcome of this batch adsorption study may result in the valorization of locally available large pine tree leaf residue waste, which could be used in water purification.

EFFICIENCY OF GRAPHITE CARBON NITRIDE IN THE SORPTION OF IRON (Fe2+) AND COPPER (Cu2+) IONS FROM AQUEOUS SOLUTION

In the present work, freshly prepared from urea powders of graphite carbon nitride were subjected to ultrasonic exfoliation and were used to evaluate their adsorption efficiency for iron and copper ions from an aqueous solution. It has been established that the sorption efficiency is significantly affected by the pH of the medium, the contact time, and the initial concentration of metal ions. It is shown that the Fe2+ sorption isotherm by carbon nitride can be well modeled by both the Langmuir and Freundlich adsorption isotherms based on correlation coefficients

Phosphorus adsorption efficiency and characteristic analysis of basic oxygen furnace slag

AbstractA large amount of furnace slag is produced from steelmaking every year. The resultant by‐products will severely damage the natural environment and ecosystems if not treated properly. Businesses worldwide have thus been striving for slag recycling and solving various complex problems. In this study, basic oxygen furnace slag (BOFS) was regarded as an adsorbent to adsorb phosphate in water. In addition to a physical–chemical property analysis of the by‐products, the present study explored the performance of basic oxygen furnace slag in adsorbing phosphorous (P) with different size settings, and observed the surface structure of fused basic oxygen furnace slag.The results revealed that free‐state Ca accounts for the majority in basic oxygen furnace slag content, demonstrating the removal of nearly all phosphorous in water. The results of Fourier‐transform infrared spectroscopy (FT‐IR) on basic oxygen furnace slag with >200 mesh size revealed complex wave crests at the fingerprint region (570–980 cm−1). The result signifies that the basic oxygen furnace slag samples comprise strong Si─O and O─Si─O bonds within silicate minerals. Moreover, basic oxygen furnace slag samples with a particle size >200 mesh contain very high content of lime (CaO) (reaching 49.5%). This property fully demonstrates that basic oxygen furnace slag samples in a small particle size were more active as an aggregate. This study found that the Langmuir adsorption isotherm model (R2 = 0.997) is slightly better than the Freundlich adsorption isotherm model (R2 = 0.984), which shows that the process in which basic oxygen furnace slag adsorbs P is monolayer adsorption, and the adsorption energy is more uniformly distributed among BOFS samples. This study also found that basic oxygen furnace slag samples melted at 1200°C can effectively encapsulate some heavy metal pollutants and form stable glassy slag. The change proved that a fused basic oxygen furnace slag sample could effectively encapsulate heavy metal pollutants and formed glassy‐state slag with high stability. This mechanism would reduce the likelihood of heavy metal leaching when basic oxygen furnace slag serves as a subgrade aggregate, permeable material, or concrete aggregate in the future.

Black Tea Waste as Green Adsorbent for Nitrate Removal from Aqueous Solutions.

The aim of the study was to prepare effective low-cost green adsorbents based on spent black tea leaves for the removal of nitrate ions from aqueous solutions. These adsorbents were obtained either by thermally treating spent tea to produce biochar (UBT-TT), or by employing the untreated tea waste (UBT) to obtain convenient bio-sorbents. The adsorbents were characterized before and after adsorption by Scanning Electron Microscopy (SEM), Energy Dispersed X-ray analysis (EDX), Infrared Spectroscopy (FTIR), and Thermal Gravimetric Analysis (TGA). The experimental conditions, such as pH, temperature, and nitrate ions concentration were studied to evaluate the interaction of nitrates with adsorbents and the potential of the adsorbents for the nitrate removal from synthetic solutions. The Langmuir, Freundlich and Temkin isotherms were applied to derive the adsorption parameters based on the obtained data. The maximum adsorption intakes for UBT and UBT-TT were 59.44 mg/g and 61.425 mg/g, respectively. The data obtained from this study were best fitted to the Freundlich adsorption isotherm applied to equilibrium (the values R2 = 0.9431 for UBT and R2 = 0.9414 for UBT-TT), this assuming the multi-layer adsorption onto a surface with a finite number of sites. The Freundlich isotherm model could explain the adsorption mechanism. These results indicated that UBT and UBT-TT could serve as novel biowaste and low-cost materials for the removal of nitrate ions from aqueous solutions.

Box–Behnken design with desirability function for methylene blue dye adsorption by microporous activated carbon from pomegranate peel using microwave assisted K2CO3 activation

This research aims to convert pomegranate peel (PP) into microporous activated carbon (PPAC) using a microwave assisted K2CO3 activation method. The optimum activation conditions were carried out with a 1:2 PP/K2CO3 impregnation ratio, radiation power 800 W, and 15 min irradiation time. The statistical Box–Behnken design (BBD) was employed as an effective tool for optimizing the factors that influence the adsorption performance and removal of methylene blue (MB) dye. The output data of BBD with a desirability function indicate a 94.8% removal of 100 mg/L MB at the following experimental conditions: PPAC dose of 0.08 g, solution pH of 7.45, process temperature of 32.1 °C, and a time of 30 min. The pseudo-second order (PSO) kinetic model accounted for the contact time for the adsorption of MB. At equilibrium conditions, the Freundlich adsorption isotherm describes the adsorption results, where the maximum adsorption capacity of PPAC for MB dye was 291.5 mg g−1. This study supports the utilization of biomass waste from pomegranate peels and conversion into renewable and sustainable adsorbent materials. As well, this work contributes to the management of waste biomass and water pollutant sequestration.

Removal of heavy metals from the aqueous solution by nanomaterials: a review with analysing and categorizing the studies.

With the development of nanotechnology and its application in various sciences, scientists have investigated the use of nanoparticles as adsorbents to remove heavy metals from aqueous solutions all over the world. So far, the results of many of these studies have been published in reputable journals. Obviously, reviewing these articles and summarizing the results of these studies from different aspects will provide new perspectives for the development of this technology for heavy metals removal from water. So the current study was performed to review the results of the published studies between 1/January/1980 to 1/January/2022. The focus of the study is on the analysis of these studies and their classification. In addition, a more detailed investigation was carried out. Among the 5155 articles, 576 articles were included based on Cochrane protocols. Results show that most of the studies (90.8%) were conducted on a laboratory scale and used synthetic solutions. Most studies were performed for Pb, Cd and Cu, removal respectively. Compared to other countries, authors with affiliation from China and Iran have published more articles. The ranking of the use of various nanomaterials were: nanocomposites > metal oxide nanomaterials > metal-based nanomaterials > carbon-based nanomaterials > dendrimers, with the wide range of sizes from less than 10nm to several hundreds of nanometers. The required amount of carbon-based nanoparticles to remove many heavy metals were lower than other nanoparticles. In most studies, pH ≤ 7 has been reported as optimal. Most studies have been followed pseudo second-order and pseudo first-order reactions and have been more agreement with Langmuir and Freundlich adsorption isotherms respectively. The results of studies show that the synthesis and optimization of new nanomaterials can be considered as a new and competitive technology. However, more studies are needed to investigate the removal of heavy metals in real samples and to overcome some challenges in the full-scale application.

Chromium removal from aqueous solution using bimetallic Bi0/Cu0-based nanocomposite biochar.

Chromium (Cr), due to its greater contamination in aquifers and distinct eco-toxic impacts, is of greater environmental concern. This study aimed to synthesize nanocomposites of almond shells biochar (BC) with zerovalent bismuth and/or copper (Bi0/BC, Cu0/BC, and Bi0-Cu0/BC) for the removal of Cr from aqueous solution. The synthesized nanocomposites were investigated using various characterization techniques such as XRD, FTIR spectroscopy, SEM, and EDX. The Cr removal potential by the nanocomposites was explored under different Cr concentrations (25-100mg/L), adsorbent doses (0.5-2.0g/L), solution pH (2-8), and contact time (10-160min). The above-mentioned advanced techniques verified successful formation of Bi0/Cu0 and their composite with BC. The synthesized nanocomposites were highly effective in the removal of Cr. The Bi0-Cu0/BC nano-biocomposites showed higher Cr removal efficiency (92%) compared to Cu0/BC (85%), Bi0/BC (76%), and BC (67%). The prepared nanocomposites led to effective Cr removal at lower Cr concentrations (25mg/L) and acidic pH (4.0). The Cr solubility changes with pH, resulting in different degrees of Cr removal by Bi0-Cu0/BC, with Cr(VI) being more soluble and easier to adsorb at low pH levels and Cr(III) being less soluble and more difficult to adsorb at high pH levels. The experimental Cr adsorption well fitted with the Freundlich adsorption isotherm model (R2 > 0.99) and pseudo-second-order kinetic model. Among the prepared nanocomposites, the Bi0-Cu0/BC showed greater stability and reusability. It was established that the as-synthesized Bi0-Cu0/BC nano-biocomposite showed excellent adsorption potential for practical Cr removal from contaminated water.

Investigation of the removal kinetics, thermodynamics and adsorption mechanism of anionic textile dye, Remazol Red RB, with powder pumice, a sustainable adsorbent from waste water.

Excessive growth and abnormal use of dyes and water in the textile industry cause serious environmental problems, especially with excessive pollution of water bodies. Adsorption is an attractive, feasible, low-cost, highly efficient and sustainable technique in terms of green chemistry for the removal of pollutants from water. This study aims to investigate the removal kinetics, thermodynamics and adsorption mechanism of Remazol Red RB, which was chosen as a representative anionic reactive dye, from synthetic wastewater using powdered pumice, taking into account various experimental parameters such as initial dye concentration, adsorption time, temperature and pH. Moreover, to support the proposed adsorption mechanism, before and after adsorption of the samples, the Fourier transform infrared spectrophotometer (FTIR) spectra, X-ray powder diffraction (XRD) diffractograms and High resolution transmission electron microscopy (HRTEM) images were also taken and used. The results show that powder pumice can be an efficient adsorbent for anionic dye removal with a relatively high adsorption capacity of 38.90mg/g, and it is very effective in 30-60min in mild conditions. The experimental data showed a high agreement with the pseudo-second-order kinetic model and the Freundlich adsorption isotherm equation. In addition, thermodynamically, the process exhibited exothermic nature and standard isosteric enthalpy and entropy changes of -4.93kJ/mol and 16.11J/mol. K were calculated. It was determined that the adsorption mechanism was predominantly based on T-shaped pi-pi interactions and had physical characteristics.

Efficient and Low-Cost Surfactant-Assisted Solid Phase Extraction Procedure For Removal Of Methylene Blue Using Natural Dolomite

Water pollution results from rapid urbanization and industrialization which has harmful effects on human health. Adsorption is one of the most efficient processes to remove pollutants from contaminated water. Natural minerals, such as dolomite, are widely spread around the world and may be easily collected in huge quantities. In this work, dolomite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and Fourier-transform infrared spectroscopy (FTIR), and was investigated for its applicability for removal of methylene blue (MB) from aqueous medium in a surfactant-assisted procedure. Using the one-factor one-time approach, batch adsorption studies were performed to establish the best experimental conditions (pH, sorbent amount, shaking time, type and concentration of surfactant and ionic strength) for removal of MB by dolomite. At optimum conditions (pH 8.0, shaking time 90 min, 1.0 g L−1 dolomite, 0.1% w/v sodium dodecyl sulfate, 25 °C), the maximum adsorption capacity was 22.2 mg g−1 and the adsorption process obeyed Langmuir and Freundlich adsorption isotherms. The findings show that dolomite effectively adsorbs MB and may be used as a less expensive sorbent in wastewater treatment to remove MB.Graphical

New insights into selective flotation recovery of gold using dye-derived thermo-responsive polymeric surfactant: DFT calculation and adsorption mechanism

The selective flotation recovery of gold from secondary resources is a sustainable strategy to fill the ever-increasing demand for gold resources, and reduce the environmental pollution. In the present work, a novel method to realize the selective and fast recovery of Au(III) in the flotation process involving the use of thermo-responsive amphiphilic polymer poly(ethylene glycol)-b-poly(N-isopropylacrylamide-co-glycidyl methacrylate) (PEG113-b-P(NIPAM108-co-GMA62)) integrated with rhodamine B thiohydrazide (RBS) affinity ligand was studied. The polymer possessed the selective capture property toward Au(III) salt and excellent adsorption performance on bubble surfaces, driven by specific coordination interactions between Au(III) salt and RBS ligand, and hydrophobic interactions between GMA moieties and bubbles. Flotation using the thermo-responsive polymeric surfactant displayed a high separation efficiency and fast flotation kinetics, achieving a separation efficiency of 85% for Au(III) salt at 28 min, which was comparable with sulfur-functionalized mesoporous materials. This flotation process followed pseudo-second-order kinetics and Freundlich isotherm adsorption model. Furthermore, in flotation recovery of Au(III) salt form actual e-waste leaching solution, separation efficiency of 81% was achieved, while Au grade was improved from 1.55 % to 34.76%. This polymeric surfactant was easily regenerated by the reduction-induced release the bound Au(III) salt and thermal precipitation, leading to retain 81% of separation efficiency after five cycles. This work provides an effective way to fabricate flotation surfactant, which can meet the urgent demand for performance improvement and chemical consumption reduction in practical applications.

Adsorption of ibuprofen using waste coffee derived carbon architecture: Experimental, kinetic modeling, statistical and bio-inspired optimization

Pharmaceuticals in water are a growing environmental concern, as they can harm aquatic life and human health. To address this issue, an adsorbent made from coffee waste that effectively removes ibuprofen (a common pharmaceutical pollutant) from wastewater was developed. The experimental adsorption phase was planned using a Design of Experiments approach with Box–Behnken strategy. The relation between the ibuprofen removal efficiency and various independent variables, including adsorbent weight (0.01–0.1 g) and pH (3–9), was evaluated via a regression model with 3-level and 4-factors using the Response surface methodology (RSM) . The optimal ibuprofen removal was achieved after 15 min using 0.1 g adsorbent at 32.4 °C and pH = 6.9.Moreover, the process was optimized using two powerful bio-inspired metaheuristics (Bacterial Foraging Optimization and Virus Optimization Algorithm). The adsorption kinetics, equilibrium, and thermodynamics of ibuprofen onto waste coffee-derived activated carbon were modeled at the identified optimal conditions. The Langmuir and Freundlich adsorption isotherms were implemented to investigate adsorption equilibrium, and thermodynamic parameters were also calculated. According to the Langmuir isotherm model, the adsorbent's maximum adsorption capacity was 350.00 mg g-1 at 35 °C. The findings revealed that the ibuprofen adsorption was well-matched with the Freundlich isotherm model, indicating multilayer adsorption on heterogeneous sites. The computed positive enthalpy value showed the endothermic nature of ibuprofen adsorption at the adsorbate interface.

Degradation of Diazo Dye and its Kinetic and Equilibrium Studies Using the Potential of Bryophyllum fedtschenkoiin Aqueous System.

Phytoremediation is emerging as an eco-friendly, innovative, and cost-effective approach for the removal of textile dyes from wastewater from the previous decade. The current research work aims to explore the potential of a terrestrial ornamental plant, Bryophyllum fedtschenkoi (Raym.-Hamet & H. Perrier) Lauz.-March. for remediating the diazo dye as Congo red (CR) in aqueous form. B. fedtschenkoi was grown hydroponically before treatment with 100 mL of a different concentration of CR dye solution. A maximum decolorization potential of 90% was obtained for 10mg L- 1 after 40h of equilibrium. The kinetic studies have revealed that the experimental results for the removal of CR dye using the B .fedtschenkoi plant are suitable for Pseudo-first order with R2 ≥ 0.92, while the equilibrium studies agreed with the Freundlich adsorption isotherm with R2 ≥ 0.909. The dye removal by the plant was confirmed with the help of analytical techniques Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Gas Chromatography-Mass Spectrometry (GC-MS) and High-Performance Liquid Chromatography (HPLC) were also performed on dye-degraded metabolites to explore the mechanism of dye degradation.

One-pot synthesis of magnetic N-doped mesoporous carbons as an efficient adsorbent for Ag(I) removal

An efficient strategy was proposed to fabricate magnetic N-doped mesoporous carbons (Fe0/NMC) via one-pot process. This one-pot strategy involved the synthesis of N-containing porous polymers using amphiphilic triblock copolymer (F127) through self-assembly of melamine formaldehyde resin, and the formation and entrapment of Fe0 nanoparticles by an in-situ carbothermal reduction approach. The surface morphology and the main chemical groups of the developed Fe0/NMC were characterized by various analytical methods such as XRD, FTIR, TGA-DTA, BET, TEM and VSM. Fe0/NMC exhibited a mesoporous structure and Fe0 nanoparticles were dispersed homogeneously on Fe0/NMC, with a saturation magnetization of 134.6 emu/g. As an adsorbent, Fe0/NMC showed an excellent adsorption capacity for Ag (I), reaching 335 mg/g. The adsorption process was consistent with the quasi-secondary kinetic model and Freundlich isothermal adsorption model, which indicated that the adsorption process was multilayer adsorption and the adsorbed element Ag was present on Fe0/NMC in the form of Ag(I) as well as chelates and Ag monomers. It could be believed that Fe0/NMC was a viable adsorption material for Ag(I) and had full-scale applications.

Removal of methylene blue from aqueous solution by adsorption onto hydroxyapatite nanoparticles

Water pollution due to industrial discharges is a major problem in many countries as it can have adverse effects on the environment and human health. Among wastewater treatment processes, adsorption technique is widely used to reduce the harmful effects of many pollutants, including dyes. The main objective of this research is to characterize and evaluate the removal capacity of methylene blue (a cationic dye) from an aqueous solution using hydroxyapatite as a bio-adsorbent. Hydroxyapatite was prepared by two different methods and the resulting biomaterials were designated HAp A, HAp B, HAp C, and HAp D. A comparative study of methylene blue adsorption by these biomaterials was performed. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize these adsorbents. The effects of various experimental parameters such as contact time (5–120 min), concentration (5–90 mg/L), pH (6–12) and temperature (25–6°C) were studied. Adsorption studies revealed a removal efficiency of 88.88% at an initial MB concentration of 45 mg/L, an equilibrium time of 20 min, Basic pH and a temperature of 25 °C. The pseudo-second order kinetic model was used to describe the adsorption kinetics, while the Freundlich adsorption isotherm was used to describe the equilibrium adsorption process. This research suggests that the method of synthesis has a significant impact on the ability of the adsorbent to remove organic pollutants from dyes in an aqueous solution.

Modelling of Basic Yellow 28 adsorption onto activated carbon: batch and continuous process

Purpose This study aims to model and investigate Basic Yellow 28 (BY28) adsorption onto activated carbon in batch and continuous process. Design/methodology/approach Batch adsorption experiments were carried out at 25 °C with 50 mg/L BY28 solution at pH 6 with different amounts of activated carbon. Freundlich and Langmuir adsorption isotherm models were used to model batch data. Pseudo-first-order and pseudo-second-order kinetic models were applied with linear regression. The changes of the breakthrough curve with the column height, flow rate, column diameter and adsorbent amount were examined in fixed bed column at room temperature. BY28 adsorption data were modelled by using different adsorption column models (Adams & Bohart, Thomas, Yoon & Nelson, Clark and modified dose–response) with non-linear regression. Findings Freundlich model and pseudo-second-order kinetic model expressed the experimental data with high compatibility. Modified dose-response model corresponded to the fixed bed column data very well. Originality/value Adsorption of Basic Yellow 28 on activated carbon in a fixed bed column was studied for the first time. Continuous adsorption process was modelled with theoretical adsorption models using non-linear regression.

Apple peels as a potential adsorbent for removal of Cu and Cr from wastewater

Abstract Solid waste management (SWM) is one of the biggest concerns of society and agricultural waste is generated in vast amounts. In this study removal of Cu and Cr from wastewater using chemically modified apple peels was studied by following batch sorption experiments. Effects of metal concentration, adsorbent dose, pH, temperature and contact duration on the adsorption of Cu & Cr were investigated by using atomic adsorption spectrophotometer (AAS). SEM & EDX analysis of the adsorbents were recorded to study the morphology of the prepared adsorbents. Qmax value of apple peels is 25 for Cr and 22 for Cu, while for apple peel charcoal it is 33 for Cr and 47 for Cu, for treated apple peels Qmax is 50 for Cr and 52 for Cu adsorption. The data was processed using pseudo first, second order kinetic and intraparticle diffusion. Results depicted that the calculated adsorption capacities (qecal) were found to be close to the experimental values (qecal) by following pseudo-second-order kinetics. The applicability of the Langmuir and Freundlich adsorption isotherms was tested. Results showed that the Langmuir model is best fitted on adsorption data because regression factor R2 values are good for the Langmuir model.

Hierarchical mesoporous spherical Zn(4-hzba) MOF for efficient adsorption of Strontium and Caesium ions from aqueous solution

This paper describes the synthesis of mesoporous spherical Zn(4-hzba) MOF with the formula of {[Zn(μ-4-hzba)2]2}n utilizing 4-hydrazinyl benzoic acid (4-hzba) linker by solvothermal method. And investigates its adsorptive efficiency towards strontium (Sr2+) and caesium (Cs+) by varying contact time, pH, and feed solution concentration. 10 mg of Zn(4-hzba) MOF show maximum adsorption capacity of 275.2 mg/g for Sr2+ and 335.05 for Cs+ at pH 4 from a 100 mg/L sample solution within 100 min at room temperature. Among the Langmuir, Freundlich and Temkin adsorption isotherms studies, the Langmuir isotherm was well fitted for Sr2+ and Cs+ adsorption onto MOF, demonstrating the monolayer adsorption. Experimental data and pseudo-second-order kinetic studies showed that chemisorption is the dominant process. High adsorption efficiency was demonstrated by electrostatic interaction between positively charged Sr2+/Cs+ and the negatively charged surface of the MOF at pH 4 was proved by zeta potential analysis. IR, SEM, XPS analysis and Langmuir adsorption studies support the monolayer surface complexation mechanism. While the ion exchange mechanism followed by surface complexation of Sr2+/ Cs+ with replacement of hydrogen in H2NNH- of the MOF. In order to acquire a good picture of the ion exchange mechanism, and Sr2+/Cs+ exchanged MOF were optimized, and the binding energies of Sr2+ (2.19 kJ/mol) and MOF Cs+ (2.06 kJ/mol) were calculated by DFT method using Gaussian 16. Recycle studies of Zn(4-hzba) MOF show 80% recovery of Sr2+ and Cs+ even after seven cycles. The adsorption of Sr2+ and Cs+ was influenced by dosage, initial concentration of metal ions, pH solution, contact time, and coexisting ions of Na, K, Ca, and Mg. Adsorption efficiency of Sr2+ and Cs+ ions in simulated seawater was 92.3% and 96.7%, respectively.

Effect of soil amendments on the sorption behavior of atrazine in sandy loam soil.

The sorption behavior of pesticides applied during cultivation of crops is affected by amendments such as farm yard manure (FYM) and vermicompost (VC) during land preparation. Among pesticides, atrazine, a widely used herbicide in many crops, was analyzed for its kinetics and sorption behavior through the addition of FYM and VC in sandy loam soil. The pseudo-second-order (PSO) model best fit the kinetics results in the recommended dose of FYM and VC mixed soil. More atrazine was sorbed onto VC mixed soil than FYM mixed soil. In comparison to control (no amendment), both FYM and VC (1, 1.5, and 2%) increased atrazine adsorption, but the effect varied with dosage and type of amendment. The Freundlich adsorption isotherm adequately explained atrazine adsorption in soil/soil + (FYM/VC) mixtures, and the adsorption was highly nonlinear. The values of Gibb's free energy change (ΔG) were negative for both adsorption and desorption in soil/soil + (FYM/VC) mixtures, suggesting sorption was exothermic and spontaneous in nature. The results revealed that the application of amendments used by farmers interferes the availability, mobility, and infiltration of atrazine in the soil. Therefore, the findings of this study suggest that amendments such as FYM and VC can be effectively used to minimize the residual toxicity of atrazine-treated ago-ecosystems in tropical and sub-tropical regions.

Preparation of hydrogels based on poplar cellulose and their removal efficiency of Cd(II) from aqueous solutions.

Industrial heavy metal-contaminated wastewater is one of the main water pollution problems. Adsorbents are a promising method for the removal of heavy metal contaminants. Herein, polyaspartic acid/carboxymethyl poplar sawdust hydrogels (PASP/CMPP) and ascorbic acid/carboxymethyl poplar sawdust hydrogels (VC/CMPP) were prepared by aqueous polymerization using alkalized poplar sawdust (CMPP) as the substrate and PASP and vitamin C (VC) as modifiers. The effective results, provided by the characterization analysis of SEM and BET, indicate that the surface of the PASP/CMPP hydrogel has a larger number of loose pores and a larger pore volume than the VC/CMPP hydrogel. The treatment effects of the two hydrogels on simulated wastewater containing Cd(II) were investigated by a batch of experiments. The results showed that PASP/CMPP had a better adsorption effect than VC/CMPP under the same adsorption conditions. Interestingly, the solid concentration effect was found in the process of sorption kinetics and sorption isotherms. The sorption kinetic curves of Cd(II) on PASP/CMPP were well-fitted by the quasi-second-order kinetics under different adsorbent concentrations. The adsorption conforms to Langmuir and Freundlich adsorption isotherm models. More importantly, PASP/CMPP composites are expected to be used as a new kind of environmental adsorbent for wastewater treatment.