Adsorption Isotherm Models Research Articles

Recycling of water treatment plant sludge for copper adsorption from aqueous solutions

Recent studies have explored various adsorbent materials that are low-cost, available in quantity, and effective for heavy metal removal, one of them is the Water Treatment Plant (WTP) sludge. The study aimed to investigate the potential of recycling Water Treatment Plant sludge into an adsorbent for Cu (II) removal. The sludge adsorbent was carbonized by using a furnace at 600°C for 2 hours. This study was conducted in batch. The adsorbent effectiveness was analyzed by varying the dosage, contact time, and activation of the sludge adsorbent on Cu (II) removal. The adsorption isotherm was analyzed using the Langmuir and Ferundlich models, and the kinetic study used pseudo-first-order and pseudo-second-order model. The results showed the removal efficiency of Cu (II) for both activated and non-activated sludge adsorbents reached 98.6–99.9%. The addition of dosage did not affect the increase in Cu (II) adsorption capacity. Activation of the adsorbent increased the adsorption capacity of Cu (II) with the equilibrium time at 60–90 min, shorter than the non-activated adsorbent at 90–120 min. The adsorption isotherm model for both adsorbent types fitted well to the Langmuir model, indicating the adsorption process occurs in a single layer on a homogeneous surface. The adsorption kinetics followed pseudo-second-order with a high correlation coefficient. Water treatment sludge, an industrial by-product, has the potential to be an effective and low-cost adsorbent material for Cu removal.

Adsorption Behavior of Methylene Blue Onto Activated Coconut Shells: Kinetic, Thermodynamic, Mechanism and Regeneration of the Adsorbent.

Adsorption techniques are widely used to remove some classes of pollutants from waters, especially those which are not easily biodegradable. The removal of Methylene blue (MB), as a pollutant, from waste waters of textile, paper, printing and other industries has been addressed by the researchers. The aim of this study is to eliminate MB by Activated Coconut Shells (ACS) produced at low cost by adsorption in batch mode. The ACS was characterized by the FTIR spectroscopy and point of zero charge (pHpzc: 5.06). Some examined factors were found to have significant impacts on the MB uptake of ACS like the initial dye concentration Co (40-120mg/L), solution pH (2-8), ACS dose (1-12g/L), agitation speed (50-500 r/min), particles size (1.0-1.2mm) and temperature (298-333K). The best capacity was found at pH 6 with an adsorbent dose 8g/L, an agitation speed 200 r/min and a contact time of 60 min. Modeling Kinetics and Isotherms shows that the pseudo-second-order kinetic model with R 2 (0.935 -0.998) and Langmuir adsorption isotherm model provide better fitness to the experimental data with the maximum adsorption capacity of 30.30mg/g at 25°C. The separation factor RL (0.933-0.541) in the concentration range studied (10-120mg/L) shows a favorable adsorption. The isotherms at different temperatures have been used for the determination of the free energy ΔG° (198-9.72kJ/mol); enthalpy ΔH° (82.082kJ/mol) and entropy ΔSo (245.689J/K mol) to predict the nature of MB adsorption process. The positive values of (ΔGo) and (ΔHo) indicate a non-spontaneous and endothermic MB adsorption with a chemisorption. The adsorbent elaborated from Coconut Shells was found to efficient and suitable for the removal of MB dye from aqueous solutions, due to its availability, low cost preparation and good uptake capacity.

Adsorption and dersorption of lead using synthetic hydroxyapatite material

The adsorption of Pb2+ ions in solution by synthetic hydroxyapatite material has been researched. Investigations were conducted into the effects of adsorption time, adsorbent mass, solution pH, and Pb2+ ion concentration. The material's adsorption efficiency to Pb2+ can reach 98.7%. Two adsorption isotherm models, Freunlich and Langmuir, were used to evaluate adsorption isotherms. The pseudo-first-order and pseudo-second-order adsorption kinetic models were used to assess the adsorption process's kinetics. Using the electrolysis approach, Pb2+ ions were successfully desorbed from the adsorbed HAp material while recovering metallic Pb on the cathode surface. Pb recovery efficiency can be as high as 93.84%. After desorption, the HAp material retains its original characteristics and still can adsorb Pb2+ ions with a high efficiency of 95.96%.

Recovery of vanadium element from wastewater of petroleum refineries using effective adsorbent: Mathematical approach via isothermal, kinetics and thermodynamic simulation

Adsorption behavior can be determined using different essential studies such as adsorption isotherm, kinetics, and thermodynamics. In this study, adsorption isotherm models, and kinetic, and thermodynamics studies are used to describe the use of alumina as an effective adsorbent and a remover of vanadium (V+5) ions from aqueous solutions contaminated by this metal. The aqueous solutions used simulate the wastewater of most traditional oil refineries. Efficiency can be determined by comparing the correlation coefficients of the linear relationships used with each model. Using alumina, the perfect removal of vanadium ions was achieved. Vanadium removal increases with an increase in the operating conditions, which are time temperature, agitation speed, pH, and adsorbent’s media dose. However, it also increases with the elimination of the initial concentration. This study shows that the vanadium’s adsorption based on the Langmuir isotherm model gives a correlation coefficient of 0.9999, while when it is based on the Temkin and Freundlich isotherms the correlation coefficient is less. Hence, adsorption on the surface of alumina takes place in monolayer surfaces with a regular distribution of particle’s binding energy and a narrow quantity of identical sites on the surface of alumina. Subsequently, the kinetic study shows that the adsorption behavior matched the pseudo-second-order kinetic model with R2 equaling 0.9999. Also, thermodynamics studies approves that the adsorption is a spontaneous endothermic process of enthalpy change.

CTAB-Si Nanoparticles Derived from Rice Husk Ash for Nitrate Ions Removal in Simulated Wastewater

In this study, silica (Si) nanoparticles derived from rice husk ash is coated with cetyltrimethylammonium bromide (CTAB), a cationic surfactant, and used as adsorbent of nitrate ion in wastewater. CTAB functionalized Si (CTAB-Si) nanoparticles were characterized using scanning electron microscope (SEM), energy dispersive X-Ray (EDX), dynamic light scattering (DLS) Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The synthesized CTAB-Si nanoparticles has a non-spherical shape, with visible polydispersity and is amorphous with average particle size of 72nm. It showed stretching vibrations of silanol at 963cm-1, siloxane at 1073cm-1, sharp peaks at 2852cm-1 and 2922cm-1 due to the methylene tail of CTAB and amine peak at 1,384cm-1. An ∼80% nitrate removal and adsorption capacity of 7.98 mg NO3/g CTAB-Si nanoparticles was obtained at optimized condition using Face Centered Central Composite Design (FC-CCD) at pH 4, 50 mgL-1 of adsorbate concentration, 0.2 gL-1 adsorbent dose and 30 minutes contact time. The adsorption isotherm and kinetic models fits well in Langmuir model and Pseudo second order with a R2 of 0.984 and 0.999 respectively. The efficiency of the nanoparticle after 5 adsorption cycles was ∼50% nitrate removal.

Micellar-enhanced ultrafiltration of heavy metal wastewater with palygorskite under various temperatures and pressures

The micellar-enhanced ultrafiltration process demonstrated significant potential for treating heavy-metal-contaminated wastewater. Operating conditions greatly influence complex formation and ultrafiltration efficiency, suggesting that optimizing these parameters could enhance both the process's effectiveness and its cost-efficiency. In this research, nano-palygorskite was used to treat wastewater contaminated with Cu2+, Zn2+, and Cd2+. The material was characterized using SEM, FTIR, XRD, and Zeta potential, and the effects of temperature and pressure variations on the process were investigated. Under conditions of pH 7.0 and 0.1 MPa, the retention rates of the three heavy metal ions rapidly equilibrated within 40 min, achieving removal efficiencies of 99.94 %, 99.75 %, and 99.56 %, respectively. Temperature changes significantly influenced the retention rates, which increased by approximately 5 % with increasing temperature. At pH 7.0 and 293 K, increasing the pressure improved the retention rates by approximately 3 %, reaching 99.31 %, 98.63 %, and 99.19 %, respectively. The experimental data fit the pseudo-2nd-order kinetic equation and Langmuir isotherm adsorption model, with maximum adsorption capacities of 10.44 mg/g, 9.41 mg/g, and 11.36 mg/g, respectively. Overall, gradual increases in the temperature and pressure accelerated the reaction rate, highlighting their beneficial effects on MEUF. This study underscores the potential of palygorskite as an effective inorganic complexing agent for heavy-metal-contaminated wastewater treatment.

Uptake of selected heavy metals from contaminated waters utilizing cost-effective and environmentally friendly biosorbents prepared from the residues of a traditionally fermented Ethiopian alcoholic beverage (Tella)

In the current study, the adsorption capacity of Tella residues (residues of fermented alcoholic beverage) for quantitative uptake of Cu(II), Cd(II), Zn(II) and Pb(II) was evaluated. Chemical treatment of the local beer residue (LBR) has improved the removal efficiency of the adsorbent, which was achieved at pH = 5, 1.0 g adsorbent, 50 mg/L initial concentration, 180 min contact time and agitation speed of 100 rpm. The adsorption was found to fit the Langmuir adsorption isotherm model, and the theoretical equilibrium capacities were well fitted with the experimental equilibrium capacities, resulting in chemical adsorption (chemisorptions) on the adsorbent surface while the equilibrium kinetics follows the pseudo-second-order. The adsorption capacity (Qo) of LBR decreases in the following order: Zn(II) > Cu(II) > Pb(II) > Cd(II) as metal concentration ranged from 20-200 mg/L. Thermodynamic parameters, including standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated to predict the nature of adsorption. The negative values of ΔG° and the positive value of ΔH° indicate that the adsorption process was spontaneous and endothermic. Adsorption capacities were found to increase when the temperature ranged from 25-60 °C. Thus, the findings suggest a promising application of LBR as an alternative low-cost novel adsorbent for the removal of toxic heavy metals from wastewater.

Influence of Supercritical Conditions on Isothermal Adsorption Capacity Calculation of Methane and Model Optimization.

The study of isothermal adsorption models for coal and methane under supercritical conditions helps us to understand the gas content distribution in coal seams and improve gas management in coal mines. Coal samples from the Hebi mine and Longshan coal mine were selected for this research. Using the weight method, isothermal adsorption curves of supercritical methane at temperatures of 308, 313, and 318 K were measured. The adsorption phase density of supercritical methane was obtained by using the intercept method and model fitting, and the absolute adsorption capacity of methane was calculated. Simultaneously, the pore volume and specific surface area of the coal samples were tested, and the isothermal adsorption model for supercritical methane was studied and optimized. The results indicate that using mercury intrusion, low-temperature N2, and low-temperature CO2 adsorption methods for testing coal sample pore structures allows for multiscale characterization of the coal pore structure. Based on the Gibbs excess adsorption theory, the phase density of methane obtained from the intercept method and model fitting effectively represent the isothermal adsorption curve of supercritical methane. By combination of the specific surface area and pore volume distribution of the coal with the absolute adsorption capacity of methane, the number of methane adsorption layers on the coal surface was calculated to be between 1.11 and 1.3 layers. This suggests that the isothermal adsorption model for supercritical methane on coal is not solely micropore filling or single molecular layer adsorption but primarily single molecular layer adsorption with concurrent micropore filling adsorption. Based on this adsorption mechanism, an L-DA isothermal adsorption model for supercritical methane on coal was established. The L-DA isothermal model shows good fitting results and effectively explains the adsorption characteristics of supercritical methane on coal.

Surface charge alteration of charcoal derived from bamboo leaves and understanding the interaction with anionic and cationic dye

Cost-effective adsorbents derived from regenerative sources provide a sustainable solution to the pressing environmental pollution challenges. Conventional studies often rely on biochar-based adsorbents obtained at high carbonization temperatures in an induced environment. The present study explored the efficacy of carbon derived from the stems (CBS) and leaves (CBL) of bamboo plants as efficient dye adsorbents at low carbonization temperatures. CBL carbonized at 350 °C exhibited a remarkable dye adsorption efficiency of 90%, significantly outperforming CBS, which achieved only 39% efficiency. To enable the adsorption of both dyes, heterophase metal oxides, specifically Fe-doped ZnO and ZnFe2O4 were incorporated. Zeta potential measurements revealed a transition from negative to positive values with metal oxide incorporation, suggesting alterations in the surface acidity and functional group composition. The adsorption performance of the composite (WC20) sample was evaluated using Congo Red (CR) and Crystal Violet (CV) dyes. Comprehensive studies on the adsorption kinetics, isotherm modeling, and thermodynamics have been conducted to identify WC20 as the most effective composite. The equilibrium adsorption data aligned well with the Langmuir isotherm model, demonstrating maximum adsorption capacities of 65.31 mg g−1 for CR and 38.05 mg g−1 for CV at room temperature of 298 K with constant pH. Thermodynamic analysis indicated a hybrid adsorption mechanism, wherein CR adsorption was predominantly driven by chemisorption, whereas CV adsorption was governed by physisorption. Mechanistic insights have revealed that electrostatic interactions and π–π stacking play crucial roles in dye removal. These findings underscore the potential applicability of WC20 as a cost-effective and efficient adsorbent for the remediation of both cationic (CV) and anionic (CR) dyes in wastewater, highlighting its viability for future environmental management and pollution mitigation strategies.

Experimental and Theoretical Studies on the Adsorption of Bromocresol Green from Aqueous Solution Using Cucumber Straw Biochar

Biochar prepared from crop straw is an economical method for adsorbing bromocresol green (BCG) from textile industrial wastewater. However, there is limited research on the adsorption mechanism of biochar for the removal of BCG. This study utilized cucumber straw as raw material to prepare biochar with good adsorption potential and characterized its physicochemical properties. Through adsorption experiments, the effects of solution pH, biochar dosage, and initial dye concentration on adsorption performance were examined. The adsorption mechanism of cucumber straw biochar (CBC) for BCG was elucidated at the molecular level using adsorption kinetics, adsorption isotherm models, and density functional theory (DFT) calculations. Results show that the specific surface area of the CBC is 101.58 m2/g, and it has a high degree of carbonization, similar to the structure of graphite crystals. The presence of aromatic rings, –OH groups, and –COOH groups in CBC provides abundant adsorption sites for BCG. The adsorption process of CBC for BCG is influenced by both physical and chemical adsorption, and can be described by the Langmuir isotherm model, indicating a monolayer adsorption process. The theoretical maximum monolayer adsorption capacity (qm) of BCG at 298 K was calculated to be 99.18 mg/g. DFT calculations reveal interactions between BCG and CBC involving electrostatic interactions, van der Waals forces, halogen–π interactions, π–π interactions, and hydrogen bonds. Additionally, the interaction of hydrogen bonds between BCG and the –COOH group of biochar is stronger than that between BCG and the –OH group. These findings provide valuable insights into the preparation and application of efficient organic dye adsorbents.

Insight into the corrosion inhibition performance of dimethyldiallylammonium chloride acrylamide copolymer for mild steel in acidic solution

Dimethyldiallylammonium chloride acrylamide (DADMAC-AAM) copolymer was firstly applied as a novel corrosion inhibitor for carbon steel in acidic solution. Electrochemical, theoretical and computational methods were performed to illustrate the corrosion inhibition mechanism of DADMAC-AAM. Results of electrochemical tests indicated that DADMAC-AAM effectively slowed down corrosion rate of mild steel in HCl solution as a mixed-type corrosion inhibitor. Its corrosion inhibition efficiency increased with dosage, and the maximum value reached about 92.44 % with adding 100 mg/L. In-situ scanning vibration electrode technique illustrated that the corrosion inhibition performance of DADMAC-AAM increased with immersion time. Metal surface was covered with a dense hydrophobic film due to the physical-chemical adsorption of DADMAC-AAM molecules, and the adsorption behavior obeyed to the Langmuir adsorption isothermal model. Theoretical calculations were carried out to explain the corrosion inhibition mechanism, and the increase of active energy indicated that the strong inhibitive action of DADMAC-AAM molecule could be due to the increase of activation energy barrier of corrosion reaction. Results obtained from computational simulations proved that DMDMAC-AAM molecules adsorbed on metal surface through interactions between N or O and Fe atoms. This adsorption film could retard the invasion of corrosive species, thus protecting metal from corrosion.

Surface modified novel synthesis of Spirulina assisted mesoporous TiO2@CTAB nanocomposite employed for efficient removal of chromium (VI) in wastewater

In this study, an investigation of the adsorption efficiency of a novel Spirulina based TiO2@CTAB nanoparticle is carried out against one of the highly toxic heavy metal Cr (VI). The co-precipitation method was used to prepare the nanoparticles which were analyzed by various techniques including XRD, UV–Vis spectroscopy, Raman Spectroscopy, FT-IR, BET, FESEM with EDX, Zeta Potential, and Particle Size Analyzer. The pore diameter of the TiO2@CTAB nanocomposite was found to be 3.425 nm with a total surface area of 125.709 m2/g. The pHZPC and XPS studies were used to describe the mechanism of adsorption of Cr (VI) by TiO2@CTAB. For synthesized material, the Langmuir adsorption isotherm model exhibits improved adsorption than the Freundlich adsorption isotherm model, having a removal capacity of 127.551 mg/g. The adsorption of CR (VI) on the surface of TiO2@CTAB follows pseudo-second-order kinetics having an R2 value of 0.99983. Furthermore, the prepared mesoporous TiO2@CTAB adsorbent has high reusability without considerable degradation and may avoid the production of secondary pollutants to a large extent.

Conversion of acidified lignin containing sulfur discharged from a biorefinery process into neutralized biochar: Characterization and metal adsorption

The objectives of this study were to produce biochars using sulfur-rich acidified lignin discharged from a biorefinery process and to evaluate their physicochemical properties and Pb adsorption capacity. As the pyrolysis temperature increased, the lignin acidified by the desulfurization process was converted to neutralized biochar (LBC), which exhibited high carbon content and stability. The carbon content of biochar manufactured at a pyrolysis temperature of 600 °C or higher was over 90 % and showed no significant difference, and their surface structures were found to be different, as revealed through XRD and FTIR analyses. The adsorption capacity of Pb by LBC increased with increasing pyrolysis temperature, and their adsorption capacity was well described by the pseudo-second-order model and the Langmuir isotherm adsorption model. In particular, the internal diffusion effect on the adsorption capacity of Pb was greater for LBC900 than for LBC600. In complex heavy metal solutions, LBC selectively exhibited high affinity for Pb, while the adsorption capacity of other metals was significantly reduced. The adsorption mechanism of Pb by LBC was verified through various analytical methods, and these results demonstrated that the adsorption of Pb by LBC was influenced by functional groups existing on the surface and inside of LBC and by some cation exchange.

Insight into Limited Recoveries in Printed Circuit Board Leaching: Evidence of Gold Adsorption Loss to Polymeric Particles

AbstractSustainable resource utilization ultimately depends on total recovery during recycling operations. PCB leach pulp for target metal recovery contains ceramic and polymeric particles resistant to reagent attack. The investigation herein shows the physicochemical behavior of five polymeric particles namely green, red, black, white, and blue in gold chloride complex [AuCl4]− solution. Gold concentration change was monitored over time to study how the gold solution interacted with the polymeric particles and how the interaction conforms to known adsorption isotherm and kinetic models. The black and green polymeric particles have the highest adsorption per unit mass to about 1.81 mg/g and 2.18 mg/g, respectively. Four adsorption kinetic models evaluated for insight on the adsorption mechanism observed show Elovich and pseudo-second-order (PSO) models fit the kinetic data best compared to other models with correlation coefficients of 0.9867 and 0.9863, respectively. Of the seven adsorption isotherm models evaluated, Sips model shows best fit for the isotherm data with correlation coefficients of 0.9727 and 0.9328 for green and black particles, respectively. Isotherm and kinetic model analyses of the experimental data indicated physisorption and chemisorption as driving mechanism of the interaction between PCB polymeric particles and gold chloride complex aliquot. Graphical Abstract

Uranium extraction from wastewater by heteroatom-doped carbon microspheres derived from polyphosphazene loading with zinc oxide

The effective management of uranium-contaminated wastewater is crucial for environmental protection and public health safety. In this context, a novel composite was synthesized involving the intergration of zinc oxide into heteroatom-doped polyphosphazene carbon microspheres (TAC/ZnO) by hydrothermal method. The incorporation of ZnO into TAC significantly enhanced the porosity, offering more adsorption sites and improving the uranium adsorption performance. The optimal adsorption experiment achieved a remarkable adsorption capacity of 513.9 mg.g−1 for U(VI) at a pH of 5.5 within just 80 min. Additionally, the adsorption process was found to be endothermic and spontaneous, following both the Langmuir isothermal adsorption model and the pseudo-second-order kinetic model. Moreover, the TAC/ZnO presented higher selectivity for U(VI) in the presence of other cations. Even after 8 cycles, TAC/ZnO maintained a good removal rate for U(VI), decreasing from 97.54 % to 81.95 %. Furthermore, the findings from X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations indicated that the adsorption mechanism of U(VI) on TAC/ZnO may involve the coordinated interaction between oxygen atoms in Zn-O and nitrogen atoms in pyridinie-N-oxide with uranyl ions. Overall, this study presents an easily prepared, cost-effective, and highly efficient adsorbent that offers potential for large-scale production and practical application in purifying radioactive wastewater.

Versatile and durable polyvinyl alcohol/alginate/gelatin/quaternary ammonium chitosan/Fe3O4 particles hybrid hydrogel beads: adsorption capabilities for cleaning pollutants

A novel hybrid hydrogel bead (HHBFe) composed of polyvinyl alcohol/sodium alginate/gelatin/quaternary ammonium chitosan (PVA/GA/SA/QCS) and Fe3O4 magnetic nanoparticles was developed through green cross-linking of Ca2+ and tannic acid (TA) combined freeze-thaw method. HHBFe exhibited a good spherical shape, porosity, magnetic properties, and excellent mechanical properties and durability. The adsorption capacity of HHB and HHBFe towards methyl orange (MO), tetracycline (Tc), and Cr (VI) was systematically studied and compared. Results revealed similar adsorption capacities for MO and Cr (VI) between HHB and HHBFe, while the presence of Fe3O4 significantly enhanced Tc adsorption, indicating the versatile adsorption functions of HHBFe. Adsorption kinetic followed the pseudo-second-order model, with external diffusion and intra-particle diffusion controlling process. The adsorption data were consistent with the Langmuir isothermal adsorption model, indicating predominantly monolayer adsorption of pollutants by beads. Notably, the beads exhibited easily regenerated, maintaining 60 % of initial adsorption capacity after 5 cycles, particularly for Tc and Cr (VI). The good adsorption performance of HHBFe can be attributed to the strong interaction between their multi-functional groups including phenolic hydroxyl groups, carboxyl groups, amino groups, etc., and pollutant molecules. The multifunctional HHBFe beads prepared in this study and the results obtained with three completely different types of pollutants provide reliability support for their use in different wastewater treatment fields and even in the field of drug carriers.

P-32 powdered activated carbon detoxifies potentially toxic elements in the Kumasi Abattoir Ghana effluent

Industrial activities, particularly from abattoirs without effluent treatment facilities, threaten ecosystems, releasing a spectrum of potentially toxic elements (PTEs) into the environment. With a defunct wastewater treatment plant (WTP), exploring a low-cost but efficacious and eco-friendly adsorbent for the Kumasi Abattoir Ghana (KAG) effluent treatment is warranted. The study is the first attempt to utilize activated carbon (AC), such as the P-32 Powdered AC (PAC) brand, to detoxify PTEs—Cadmium (Cd), Copper (Cu), Zinc (Zn), Iron (Fe), and Lead (Pb)—in Ghana’s abattoir effluent. The adsorbent was manufactured and supplied by the Climate/Environmental Research and Technology (CLERET) Laboratory, one of the Research and Development (R&D) departments of Explore Scientific Innovations (ESI) Ltd., Ghana, using palm nutshell wastes as precursor. The study systematically evaluated the efficiency and adsorption prowess using incremental masses of 0.5, 1.0, 1.5, 2.0, and 2.5 g of the adsorbent/100 ml effluent, with three replicates per experimental unit in one cycle application of the adsorbent. The PTE concentrations were determined using standard methods before and after applying the adsorbent. Three adsorption isotherm models Langmuir, Freundlich, and Elovich, were applied to investigate the adsorption mechanisms governing the PTEs. The model performance was evaluated using R2 and Root Mean Squared Error (RMSE) metrics. The findings unveiled varied percentage removal efficiencies (% Rs), with Zn exhibiting the highest (79.64 %) at 2.5 g and Cd the least (7.8 %) at 0.5 g, of the carbon. The Freundlich isotherm emerged as the most robust model, consistently exhibiting the highest coefficient of determination (R2) with the lowest RSME values. Fe and Cd had the highest and lowest adsorption capacity (Kf) of 0.181 and 0.001, respectively. The Freundlich exponent (nf) values were within the favorability range of 1–10. The PTE adsorptions were physical rather than chemical. P-32 PAC provided a promising avenue for abattoir effluent management.

Construction of MIL-100(Fe)-DMA material for efficient adsorption of Sr and Cs ions from radioactive wastewater

A novel metal-organic framework (MOF) material, MIL-100(Fe)-DMA, was synthesized using the solvothermal method. The structure of the MOF was characterized using scanning electron microscopy-energy dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy. Batch adsorption experiments were performed to investigate the effects of initial Sr2+ and Cs+ concentrations, adsorption time, pH, and coexisting cations on the adsorption performance of the material. The adsorption mechanism was further elucidated using adsorption kinetics and isotherm models. The results indicated that the adsorption of Sr2+ and Cs+ does not significantly affect the MOF material structure. As reaction time and initial ion concentration increased, the adsorption capacity of MIL-100(Fe)-DMA for Sr2+ and Cs+ increased rapidly and then gradually reached equilibrium. Optimal adsorption occurred under alkaline conditions, with maximum adsorption capacity observed at pH = 8. The adsorption process for Sr2+ and Cs+ was well described by the pseudo-second-order kinetic model, the Weber–Morris model, and the Langmuir adsorption isothermal model. The adsorption process was mainly identified as monolayer chemical adsorption, influenced by multiple factors. Characterization combined with density functional theory calculations revealed that the unsaturated carboxylic acid groups on the surface of the MOFs play a crucial role in the interaction with Sr2+ and Cs+.

Monodispersed FeS nanoparticles decorated on kaolinite for synchronous removal of benzo [a]pyrene and Cr(VI) complex pollution

Novel FeS/kaolinite composite (K-FeS) were successfully prepared using an in-situ precipitation method. At 30 % FeS loading, 1 g/L of the composite material by activating peroxymonosulfate (PMS) was able to completely remove 20 mg/L benzo[a]pyrene (BaP) and 40 mg/L Cr(VI) within 20 min under optimized conditions. The simultaneous removal experiments of BaP and Cr(VI) for the influence factors of BaP concentration, Cr(VI) concentration, composites dosage and PMS dosage to be 20 mg/L, 40 mg/L, 1 g/L, and 0.75 mmol/L, respectively. Experiments on environmental factors show that low temperature and acidic conditions are more favorable for material activity, and the addition of Cl- could promote the removal of BaP and Cr(VI). Comparative experiments showed that the simultaneous presence of BaP and Cr(VI) did not affect the removal of each other. The pseudo second-order kinetic model and Langmuir adsorption isotherm model were better to fit the experimental data, and the thermodynamic analyses indicated that the removal processes of BaP and Cr(VI) were spontaneous and exothermic. Besides, the quenching experiments yielded that SO4− and OH played a dominant role in BaP removal, and Cr(VI) removal mainly depended on the reduction of composites. This study expands the application of clay minerals in water treatment and suggests new strategies for simultaneous treatment of multiple pollutants in the environment.

Kinetics, Thermodynamics, and Mechanistic Studies of Arsenic Removal Utilizing Natural Soil as Adsorbent.

The contamination of water sources with the heavy metal contaminant arsenic (As) causes substantial risks to humans, animals, and other living organisms. Therefore, the introduction of methods for the removal of As is important. The present study aimed to investigate the adsorption model and mechanism of As removal utilizing natural soil adsorbents. The batch adsorption technique was used to analyze the impacts of various parameters such as contact time, initial As concentration, pH, and temperature. Adsorption mechanisms were studied through adsorption kinetic, isotherm, and thermodynamic models. The batch adsorption study findings indicate that the optimal conditions for maximum As removal were achieved by application of 2.2 g of adsorbents in 50 μg/L of As solution for 60 min of contact time at a pH of 5.5 ± 0.5 and a temperature of 40 °C. The highest removal efficiency was achieved when red soil was employed as the adsorbent. The kinetic, isotherm, and thermodynamic models revealed that As adsorption was a chemisorptive, nonspontaneous, and endothermic process.