Isotherm Model Research Articles

Modeling indirectly detected analyte peaks in ion-pair reversed-phase chromatography

In indirect detection, sample components lacking detectable properties are detected by adding a detectable component to the eluent, a so-called probe that interacts with the analytes to be detected. This study focuses on modeling indirect detection in two principally different cases. In case (1), the analyte component has the same charge as the probe component, so the probe acts as a co-ion of the analyte. In case (2), the analyte component has the opposite charge to the probe, so the probe acts as a counter-ion of the analyte.In the co-ion case (1), the analytes are alkyl sulfonates, and a competitive bi-Langmuir isotherm model was used. In the counter-ion case (2), the analytes are amines, and a modified bi-Langmuir isotherm model, incorporating ion-pairing on the stationary phase surface, was derived and applied for simulating the elution profiles. The chromatographic system comprised an XBridge Phenyl column as the stationary phase and an acetonitrile/phosphate buffer mixture with varying concentrations of sodium 2-naphthalenesulfonate as the eluent. In both cases, the detectable probe component was sodium 2-naphthalenesulfonate.The applied isotherm models successfully predicted system peaks with high agreement in both model cases, with calculated relative errors in retention times typically below 4.72 % and often below 1 %. The models were employed to predict the sensitivity of analytical methods, demonstrating excellent agreement between experimental and calculated sensitivities. These findings confirm the validity of the new adsorption isotherm model under these experimental conditions.

Exploration of two novel highly efficient polymer composite materials based on 3-chloropropyltriethoxysilane-grafted waste para-aramid functionalized by organo-phosphonic acid/L-proline and their excellent adsorption performance for gold ions

Two novel highly efficient polymer composite adsorbents based on 3-chloropropyltriethoxysilane-grafted waste para-aramid (PPTA-CP-AT and PPTA-CP-L, PPTA=poly-p-phenylene terephthamide; CP = 3-chloropropyltriethoxysilane; AT=amino trimethylene phosphonic acid; L=L-proline) have been successfully prepared and characterized. The new adsorbents were synthesized by functionalizing 3-chloropropyltriethoxysilane-grafted waste para-aramid with amino trimethylene phosphonic acid and L-proline, respectively. They have been employed to adsorb gold ions from aqueous solution, and the relevant adsorption behaviors have been investigated in detail. The adsorption isotherms of PPTA-CP-AT and PPTA-CP-L were consistent with the Langmuir isotherm model, and the corresponding kinetics could be best described by the pseudo-second-order kinetic model. In particular, the adsorption capacity of PPTA-CP-L was much higher than the values reported in the literature. In addition, the effect of pH on the gold ions adsorption and the thermodynamic parameters of the adsorption procedure were assessed. The research results indicated that PPTA-CP-AT and PPTA-CP-L are two novel adsorbents with high efficiency in wastewater treatment and recovery of precious gold. In particular PPTA-CP-L, which was obtained through facile esterification synthesis at low temperature, showed an excellent adsorption performance and could be used as potentially excellent adsorbent for gold uptake.

Synthesis, (bio)degradation, and utilization of starch-derived biopolymers in defined hard waters

Climate change is causing a change in local rainfall, which generally brings with it a reduction in rainfall and, consequently, an increase in water hardness. This study explores the suitability and stability of various dextrin-derived polymers for cation removal in simulated hard water conditions. Thermal analysis and Fourier-transform infrared spectroscopy confirm the polymers' thermal stability and proper formation. Biodegradability assessments reveal KLEPTOSE®LINECAPS (LC) and GLUCIDEX2® (Glu2) dextrin with pyromellitic dianhydride (PMDA) derivatives have higher durability as they were able to endure enzymatic activity. Adsorption experiments at 300 and 600 ppm indicate significant variations influenced by monomer and crosslinker types, with linear monomers demonstrating superior performance. Notably, different crosslinkers exhibit varying affinities for calcium and magnesium ions, with PMDA derivatives excelling for magnesium and citric acid (CA) derivatives for calcium. Kinetic and isotherm studies reveal a favorable trend towards quasi-second-order kinetics and Freundlich isotherm models, attributed to cavity heterogeneity and diverse attachment points as evidenced in existing literature. These findings suggest promising applications for these polymers, traditionally employed for organic contaminant removal, as additional filters to mitigate water hardness.

Fabrication of organic/inorganic reactive composites for fast removal of arsenic species from groundwater systems

This study investigates the catalytic potential of anionic MnO2 nanosheets (Mn), a cationic covalent organic Framework (COF), and their composites (CM, C2M, and CM2) with varying Mn weight percentages for arsenic removal from groundwater. The catalysts were used as activators of sodium sulfite (SS) under light conditions, enabling the pre-oxidation of arsenic (III) (As3) to arsenic(V) (As5), followed by the adsorption of As5 for complete arsenic removal from water. The Mn-COF-SS systems (C2M, CM, CM2) exhibited superior performance compared to Mn and COF alone, highlighting the dual functionality of the composites as both oxidizing agents and effective adsorbents for arsenic species. Among the composites, CM2 with 32 wt% Mn demonstrates exceptional efficiency, achieving 99.99 % arsenic removal within 30 min. The sorption process in a batch reactor was pH-dependent, with sulfate radicals (SO4-) and electrostatic interactions playing key roles in As3 oxidation and As5 removal, respectively. The pseudo-second-order kinetic model was found to be the dominant model for the sorption process, and the sorption process was compatible with the Freundlich isotherm model, which indicates a multilayer adsorption process of arsenic species on CM2. The practical application of CM2 in a fixed-bed reactor showed its high efficiency for arsenic removal, achieving the contaminant level below 10 ppb as recommended by WHO. This project highlights the potential of CM2 as an effective catalyst for arsenic removal, offering a promising approach to mitigating arsenic contamination in water sources.

Adsorption of VOC vapors on ZnPc: sensing and kinetic studies.

Thin film of sensing unit, 2,3,9,10,16,17-hexakis(3-dietylaminophenoxy)-23-etynylphenyl-(2-ferrocenyl-o-carborane)phthalocyaninato zinc(II) (ZnPc), have been deposited by spray pyrolysis technique on the quartz crystal surface with a fundamental resonance frequency of 10MHz. The surfacemorphology of the film has been studied using the contact mode atomic force microscope (AFM) technique and the average surface roughness was determined to be 36.4nm. Then, this film was exposed to the vapors of methanol, ethanol, 2-propanol, and 1-butanol with various concentrations varying between 50 and 400ppm. In addition, studies on response time and repeatability of the sensors have also been carried out. Films exhibit maximum sensing response to methanol vapor while the lowest sensitivity of the film towards 1-butanol has been observed. After an exposure time of 10min, the frequency shift of 415Hz was recorded for 400ppm methanol vapor concentration, while a frequency shift of 215Hz was observed for the same concentration of 1-butanol. The sensor was 1.30 times more sensitive to methanol vapor than ethanol and 2.00 times more sensitive to methanol than to 1-butanol. Variations in the sensitivity of the sensor have been correlated with the number of carbon groups in analyte vapors. The effect of the number of carbon groups in analyte molecule on adsorption kinetics of the film has also been investigated and compared. Adsorption isotherms of four volatile organic compounds on ZnPc were investigated at room temperature and the experimental data obtained were correlated with different existing adsorption isotherm models such as the Langmuir, the Freundlich, and Temkin model. An overall evaluation of the obtained results showed that the sensing performance, adsorption kinetic, and adsorption isotherms are dependent on the molecular size of the analyte molecules.

Interweaving two dimensional mesoporous covalent organic frameworks for efficient removal of mercury from aqueous solution

The current study defines the ultrasound-assisted solvothermal synthesis of covalent organic frameworks (COFs) using a combination of 4,4′-diaminobiphenyl and trialdehyde (BDTA-COF). The X-ray diffraction (XRD) studies confirm the formation of COF, which aligns better with AA stacking than AB stacking. The morphology of the formed COFs is a flower-like structure. The Fourier transform infrared spectroscopic (FTIR) results show that imine linkages are forming and that the aldehayde and amine peaks are not present. The formed BDTA-COF was found to be mesoporous and exhibit 2.4 nm pore size with 472 m2g−1 surface area. BDTA-COF has been evaluated for the effective removal of Hg+ from an aqueous solution through adsorption. Maximum adsorption efficiency (99 %) was achieved by optimizing the parameters like selectivity of metal, concentration, pH, amount of adsorbent. The nitrogen atoms from the imine linkages and the oxygen atoms in BDTA-COF are the primary active sites for effective adsorption of Hg⁺. The adsorption kinetics control the chemisorption of Hg+ with the BDTA-COF's imine group since the results fit well with the pseudo-second-order model. Among the various isotherm models, the BDTA-COF/Hg+ system followed the Langmuir model and insists on the monolayer adsorption phenomena. After adsorption, the XRD shows a slight change in peak positions, and the SEM image indicates the deposition of micrometer-sized particles onto the BDTA-COF. After adsorption, FTIR and X-ray photoelectron spectroscopic (XPS) tests show the interaction of functional groups of BDTA-COF and Hg+. High surface area, covalency, porosity, ordered confinement, imine linkages and stability of COFs could be the reasons for good adsorption efficiency and need additional tuning for practical applications for adsorption removal of pollutants from water.

Efficient and selective adsorption of Ni(II) and Mo(VI) utilizing novel materials derived from in situ aminated Co/Zn-ZIF-Modified biochar

The imperative need for efficient and selective adsorption of Ni(II) and Mo(VI) is crucial for resource utilization and environmental protection. However, this process faces a challenge due to the scarcity of adsorbents that can adeptly adsorb both metal ions simultaneously. To address this, this study introduces a novel composite adsorbent material, denoted as BECZN, achieved through composite cross-linking of waste orange peel biochar with in situ aminated cobalt/zinc-zeolitic imidazolate frameworks (Co/Zn-ZIF-NH2). The incorporation of Co/Zn-ZIF-NH2 enhances the availability of active groups within BECZN. The aerogel structure of BECZN prevents ZIF material collapse and agglomeration, thereby improving active site exposure. BECZN exhibits notable adsorption capacities, reaching 151.84 mg/g for Ni(II) at pH = 7 and 842.54 mg/g for Mo(VI) at pH = 3. Further investigations indicated that the adsorption of Ni(II) and Mo(VI) obeys the Langmuir isotherm model, while exhibiting pseudo-second-order kinetics and intraparticle diffusion characteristics. Notably, BECZN selectively adsorbs Ni(II) and Mo(VI) efficiently under acidic and neutral conditions, respectively. It can maintain high capacity under the interference of various cations and anions. Meanwhile, this excellent selective adsorption of Ni(II) and Mo(VI) by Co/Zn-ZIF-NH2 is revealed at the atomic level using density functional theory (DFT) calculations. This study offers a theoretical basis and experimental reference for the design and synthesis of ZIF and biomass-based composite adsorbents.

Arsenic Removal from Water using Marble Powder Waste: A Comprehensive Study on Adsorption Dynamics and Machine Learning Predictions

Enhanced aqueous arsenite (As(III) removal by adsorption on marble waste powder (MWP) in batch and continuous mode was investigated. A predictive (ML) algorithm was developed to predict arsenic removal by MWP. This study pioneers the use of ML applications on MWP. The batch-scale data revealed that the adsorption of arsenite on MWP can be best described by the Liu Isotherm model, and non-linear pseudo-first-order kinetics were observed. The intraparticle diffusion model revealed adsorption occurred in more than one step, and further analysis indicated that mass transfer was the dominant step. Under favorable conditions, the regeneration potential of MWP was also observed. From laboratory experiments, three comprehensive datasets (Batch adsorption, continuous adsorption, and regeneration) were generated and used for predictive modelling. Different linear and non-linear ML models were first optimized with hyperparameter tuning using GridSearchCV and then trained and evaluated for their performance. Evaluation metrics and learning curves showed that non-linear ML models outperformed linear models. The extra trees model was the most accurate predictive model, with prediction accuracy of 91.1%, 99.2% and 66.8% in datasets, respectively. The theoretical up-scaling suggests fixed-bed pilot-scale system of MWP can treat around 6,000 liters of arsenic-contaminated water in 1.37 days before the breakthrough.

Harnessing carbon-based adsorbents for poly- and perfluorinated substance removal: A comprehensive review

Poly- and perfluoroalkyl substances (PFAS) are synthetic, highly fluorinated chemicals commonly used in products like water-resistant materials, personal care items, non-stick cookware, and cleaning agents. Due to the strength of their CF bonds, PFAS are extremely persistent in the environment, creating significant challenges for pollution control. Traditional degradation methods often prove ineffective, making adsorption a promising alternative for PFAS removal from contaminated water. Carbon-based adsorbents, valued for their sustainability and efficiency, are particularly effective for this purpose. This review provides a detailed analysis on PFAS properties and their removal using various carbon-based adsorbents, including activated carbon, biochar, graphene oxide, carbon nanotubes, and magnetic composites. Adsorption capacities of these materials were seen vary significantly, from as low as 10.7 mg/g for Fe3O4-hybrid biochar, to as high as 713.85 mg/g for functionalized graphene-based adsorbent, highlighting the superior adsorption efficiency of modified graphene adsorbents compared to traditional biochar and activated carbons. Most of these adsorbents fit the Langmuir isotherm model and pseudo-second-order kinetic model with high coefficient of determination, indicating efficient monolayer adsorption and strong interaction with PFAS. The review also explores different adsorption mechanisms, the effects of process parameters on adsorption efficiency, strategies for adsorbent regeneration, and concludes with a bibliometric analysis that highlights key research gaps. These insights are intended to guide future advancements in the development of effective, scalable PFAS remediation technologies using carbon-based adsorbents.

Magnetic coconut shell biochar/sodium alginate composite aerogel beads for efficient removal of methylene blue from wastewater: Synthesis, characterization, and mechanism

The challenges of recovering powdered biochar and its limited adsorption capacity are major obstacles to the application of agricultural waste in dye adsorption. To address these issues, this work fabricates Fe3O4-modified coconut shells biochar (mCSB)/sodium alginate (SA) aerogel beads using an in-situ crosslinking-gelation method and freeze-drying technology for methylene blue (MB) removal from wastewater. The spherical mCSB/SA aerogel beads with good magnetic properties (12.8 emu·g−1) can be easily separated from aqueous solutions, thereby completely avoiding the hazard of secondary pollution and device obstruction associated with powdered adsorbents. The absorption capability of MB by mCSB/SA aerogel beads was analyzed and optimized at different conditions. Furthermore, the maximum adsorption capacity of mCSB/SA aerogel beads is 625 mg·g−1 for MB, following the Langmuir isotherm model (R2 = 0.9997). Additionally, the adsorption process of MB on mCSB/SA aerogel beads is found to be spontaneous and endothermic, following the pseudo-second-order kinetic (R2 = 0.9991). Encouragingly, the adsorption efficiency of mCSB/SA aerogel beads remains above 95 % even after 5 times of reusability cycles, demonstrating excellent regeneration ability. This work proposes a straightforward and scalable fabrication strategy to convert agricultural waste into efficient adsorbents for wastewater treatment, adhering to the principles of sustainable development.

Preparation of sodium carboxymethyl cellulose/two-dimensional metal carbide composite xerogel by phytic acid crosslinking for uranium recovery

Uranium, as a raw material for clean and green energy, is abundant in the oceans. Therefore, uranium recovery from seawater is an important way to solve the problems of energy shortage and environmental pollution. Here, two-dimensional metal carbides (MXene) and sodium carboxymethyl cellulose (CMC) were crosslinked via phytic acid (PA) to prepare a composite xerogel with cross-linked network structure (PA@MCX). The results showed that PA@MCX had excellent wet-state strength (6.92 MPa) and recyclability, which were critical for adsorbent in practical applications. The adsorbent’s adsorption behavior was more aptly characterized by the pseudo-second-order kinetics and Langmuir isotherm model, yielding a theoretical maximum adsorption capacity of 468.5 mg/g. Furthermore, the phosphate groups in the PA@MCX adsorbent exhibited a strong preference for uranium, achieving a ratio of uranium to vanadium adsorption capacity of 6.6 in tests involving competing ions. After five adsorption–desorption cycles, the adsorbent can still maintain a high elution rate of 80.4 % for uranium. This gel-type adsorbent with high strength, easy recovery, considerable adsorption capacity and excellent selectivity will be one of the mainstreams for uranium extraction from seawater in the future.

An innovative and efficient strategy for removing Congo red using magnetic hollow Zn/Co zeolitic imidazolate framework composite

The discharge of wastewater containing Congo red (CR) poses a significant threat to aquatic ecosystems and human health, underscoring the urgent need for effective removal methods. In this study, we have developed a novel strategy for efficient removing CR, utilizing the synthesized magnetic hollow Zn/Co zeolitic imidazolate framework composite (MH-ZIF). Comprehensive characterization of MH-ZIF and comparison with contrasting materials were conducted. The adsorption behavior of MH-ZIF towards CR followed the pseudo-second-order kinetic model and Langmuir isothermal adsorption model, demonstrating monolayer chemisorption. Remarkably, MH-ZIF exhibited an impressive adsorption capacity of 1167.9 mg g−1 for CR at 293 K. The addition of merely 0.15 g L−1 of MH-ZIF achieved nearly complete adsorption of CR within a concentration of 150 mg L−1. With the assistance of an external magnetic field, CR adsorbed on MH-ZIF can be effectively and swiftly removed within just 30 s. Hence, MH-ZIF demonstrates great promise in effectively removing CR from wastewater, attributed to its high adsorption capacity, selectivity, and magnetic properties.

Design of some ferrite-based nanoparticles for uranium removal from Sella leach liquor

ABSTRACT Uranium is a non-biodegradable, toxic and radioactive inorganic pollutant that can cause serious human health impacts. This work aims to dip magnesium and lanthanum in ferrite nanoparticles and study their ability to bind uranium ions from uranium leach liquor. MgFe2O4, LaFe2O4 and CeFe2O4 nano-adsorbents were synthesised and characterised. Comparative studies of uranium sorption on the synthesised nano-adsorbents were achieved through a series of experiments at different adsorption conditions. The results show fast uranium sorption on the nanoparticles (with a high efficiency of 86.4 to 91.6), which reflects their higher affinities towards uranium ions. There is a clear improvement in the adsorption capacities of the nanoparticles for uranium binding in adsorption systems at higher temperatures. The maximum adsorption capacity of the MgFe2O4, LaFe2O4 and CeFe2O4 nano-adsorbents was obtained at pH 5, 0.5 g/L (S/L), 400 mg/L (Ci), 333 K and 90 min. The maximum adsorption capacities of uranium on MgFe2O4, LaFe2O4 and CeFe2O4 nanoparticles are 160.4, 118.8 and 129.2 mg/g, respectively. The assessment of the kinetic, isotherm and thermodynamic models was studied to evaluate the reliability and accuracy of these models in predicting the behaviour of uranium adsorption onto the used nanoparticles under various conditions. The outcome of these models confirms the hypothesis of the Elovich, pseudo-second order, Bangham, Langmuir, Dubinin and Radushkevich models to describe the adsorption process. Additionally, it suggests that uranium removal by the nanoparticles takes place through endothermic and spontaneous physio-chemical adsorption reactions. The nanoparticles show high capacity (115.7–142.3 mg/g) and efficiency (78.1–81.7%) for the uranium ions from different uranium-containing samples. These results confirm the high affinity of the synthesised nanoparticles for uranium adsorption in different media.

Microplastics affect the removal of dye in textile wastewater: Adsorption capacity and its effect on coagulation behavior

Microplastics (MPs) are easily prone to adsorption reactions in an aquatic environment. Dyes in textile wastewater might be released and adsorbed by microplastics, causing ecological pollution. In this paper, polyamide microplastics (PA MPs) and reactive orange dye (KGN) were used as the main research objects, the adsorption capacity of different MPs, the adsorption mechanisms of KGN on PA MPs, and the effect of microplastic adsorption on the coagulation process were investigated. PA MPs had a maximum adsorption capacity of 0.866 mg/g. The kinetic results demonstrated that chemisorption, which can be broken down into three stages: membrane diffusion, intraparticle diffusion, and dynamic equilibrium, was primarily responsible for controlling the adsorption process. Adsorption took place on the surface of the monomolecular layer, according to the isotherm modeling, which indicated that the adsorption results were more consistent with the Langmuir isotherm. In addition, the effect of microplastic adsorption followed by coagulation experiments was investigated. When reactive orange is adsorbed by PA MPs, the maximum increase in coagulation removal efficiency is 4.7 %, it can also improve the growth ability of flocs, enhance the uniformity, and make their average particle size close to 63 μm. Finally, the possible mechanisms of adsorption and coagulation during the experiments are described, and an outlook for future work is given.

Evaluation of mycotoxin binders against deoxynivalenol and fumonisin B1 using isotherm models and linear equations

This study was conducted to evaluate the adsorbent characteristics of two mycotoxin binders (BBAc – composed of bentonite, β-glucans, and activated charcoal, and SepHt – composed of heat-treated sepiolite) against deoxynivalenol (DON) and fumonisin B1 (FB1) using Brunaeur-Emmett-Teller, Dubinin–Radushkevich, Freundlich, and Langmuir isotherm models and linear regression equations. Both products were tested in vitro at 0.5% with increasing levels of DON or FB1 (0.5–10 mg L−1) using solutions of pH 3 and pH 6 and analysed by LC-MS/MS. FB1 adsorption rates were not different between the products (p > 0.05) at pH 3 and pH 6. At a DON concentration of 1 mg L−1, BBAc had higher (p < 0.05) adsorption rates than SepHt. For DON, the Freundlich model had the best fit with BBAc at pH 3 and 6, and the Langmuir model with SepHt at both pHs. For FB1, the Freundlich model had the best fit with BBAc and SepHt at pH 3, and the Langmuir model with both products at pH 6. All the linear regression equations had lower R2 than the isotherm models. Therefore, the adsorption isotherm models provided more informative and reliable data for the mycotoxins and mycotoxin binders tested herein.

Novel Nanocomposite of Carbonized Chitosan-Zinc Oxide-Magnetite for Adsorption of Toxic Elements from Aqueous Solutions.

Herein, a novel nanocomposite (carbonized chitosan-zinc oxide-magnetite, CCZF) was developed to effectively remove toxic elements in water remediation. Combining the high adsorption capacities of chitosan with the magnetic properties of magnetite and the chemical stability of zinc oxide, the combination of these unique properties makes it an efficient and versatile material that offers a sustainable solution for water purification. The (CCZF) nanocomposite was synthesized through the coprecipitation method and characterized using various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and zeta potential analysis. The results showed impressive maximum adsorption capacities of 891.34 mg/g for Ni2+, 1269.35 mg/g for Co2+, and 1502.67 mg/g for Cu2+, fitting well with a modified Langmuir isotherm model. The adsorption process was spontaneous and endothermic, characterized by low positive enthalpy (ΔH) values ranging from 10.95 to 34.9 kJ/mol, indicative of the physical adsorption mechanism. Additionally, the nanocomposite demonstrated good reusability over multiple adsorption and desorption cycles. This research highlights the potential of the (CCZF) nanocomposite as a highly efficient, reusable adsorbent for the removal of toxic elements from aqueous solutions, contributing significantly to environmental remediation efforts and pollution control.

Comparative adsorption of tetracycline by acid-modified silicomanganese fumes: kinetic and process modelling

ABSTRACT In this novel study, we treated silicomanganese fumes with HNO3 and HCl to produce high-performance adsorptive materials, namely SMF-HN and SMF-HC. These acid-modified materials were then subjected to morphology, crystallinity, thermal, and spectroscopic analysis. The prepared materials were then tested for their efficacy in removing tetracycline antibiotics from wastewater. Surface analysis, a key property in the adsorption process, revealed BET surface areas of 178.14, 154.1, and 7.73 m2/g for SMF-HC, SMF-HN, and SMF, respectively. The adsorption performance was further analysed with respect to various parameters such as pH, dosage, pollutant concentration, and contact time. The adsorption isotherms models in agreement with the Langmuir, Redlich-Peterson, and Sips models, with high R2 values for all the samples. The SMF-HN and SMF-HC show a comparable adsorption capacity at 111.17 and 93.32 mg/g, respectively. The kinetics models indicated that the reaction follows pseudo-second-order kinetics. This study suggests that the adsorption mechanism occurs via chemisorption methods. The regeneration studies demonstrated that SMF-HN and SMF-HC adsorbents maintained a high removal percentage of TC after undergoing five cycles of adsorption-desorption experiments. Specifically, both adsorbents maintained 100% removal of TC in the first three cycles and a slight drop in the fourth (~96%) and fifth cycles (~90%).

Improved Adsorption of Organic Dyes onto a Polypyrrole/Tannic Acid Nanocomposite.

Methyl orange (MO) and methylene blue (MB) dyes are toxic and carcinogenic; thus, their presence in water bodies has been a major concern. Designing an efficient adsorbent for removal of these dyes is a scientific challenge for researchers. In this work, a polypyrrole-tannic acid nanocomposite was prepared via a chemical oxidation method and used as a novel adsorbent for removing these toxic dyes. The synthesized nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller methods. The effect of different parameters on adsorption such as adsorbent doses, temperature, pH, initial dye concentration, and contact time was studied. The adsorption was in line with pseudo-second-order kinetics and the Langmuir isotherm model. ΔG°, ΔH°, and ΔS° were calculated to ascertain the feasibility of adsorption. The maximum adsorption capacities attained for this adsorbent were found to be 204.08 mg/g toward the MO dye and 217.39 mg/g toward the MB dye.

Effective removal of Pb2+ from water by a novel magnetic Fe3O4-MnO2 composite prepared from steel pickling waste liquid: Adsorption behavior and mechanism

The high-value utilization of steel pickling waste liquid (SPWL) is an important direction in the resourceful utilization of hazardous waste. In this study, nano-Fe3O4 prepared from SPWL (S-Fe3O4) was hydrothermally compounded with MnO2 as Fe3O4-MnO2 (SFM), which were compared with Fe3O4-MnO2 (CFM) prepared by chemical reagents. The synthetic materials were evaluated by SEM, VSM, BET, XRD, and zeta potential, the results show that the spherical S-Fe3O4 was encapsulated by spiny spherical shell-like MnO2, and the SFM has a high saturation magnetization and specific surface area (159.91 m2/g). The adsorption experiments demonstrated that the adsorption effect of SFM on Pb2+ is highly similar to that of CFM. The maximal adsorption capacity of SFM reached 129.74 mg/g under ideal composite ratio and pH conditions, and the adsorption process was unaffected by competing heavy metal ions coexisting in the environment. Moreover, the high saturation magnetization strength of the SFM makes it simple to separate materials under a magnetic field. The pseudo-second-order kinetics and Langmuir isotherm models provided a good description of the Pb2+ adsorption on SFM. XPS and FTIR analysis provided evidence that the adsorbent surface has a high concentration of -OH functional groups, and that O atoms serve as Pb2+ binding sites, suggesting that ion exchange occurs during the SFM adsorption process. In this paper, we developed a cheap SFM with high adsorption performance and provided a novel approach to the high-value application of SPWL.

Investigating the adsorption potential of coconut coir as an economical adsorbent for decontamination of lanthanum ion from aqueous solution

Coconut coir was explored as economical sorbent for the adsorptive removal of lanthanum ion (La3+) from aqueous media. Both column and batch studies were conducted to assess the effective removal of La3+ on coconut coir by optimizing different adsorption variables such as bed height, flow rate, pH, adsorbent dosage, shaking time, initial metal concentration, and temperature. Characterization of coconut coir was carried out by scanning electron microscopy (SEM), FT-IR, and BET studies prior and subsequent to adsorption. The effective removal of La3+ was defined in certain media by the pHzpc, which was found to be 5.7 ± 0.1. The optimum 94.04 ± 0.2% adsorption of La3+ on coconut coir was observed by shaking 4 cm3 of 90 mol/L solution of La3+ with 0.3 g adsorbent dose for 10 min at neutral pH. The Langmuir adsorption capacity was found to be q e = 2.88 ± 0.02 mg g − 1 and Freundlich adsorption capacity was KF = 0.1294 ± 0.03 mg g − 1 . The pseudo-second-order kinetic and Langmuir isotherm models provided an ideal fit for the adsorption process. The column analysis also showed direct correlation of bed height and initial metal concentration with % adsorption, while % removal decreased as flow rate increased. The high regression coefficient values confirm that the BDST model is in line with the test data. Van’t Hoff equation proved the spontaneous endothermic process. Effect of external ions and desorption are also studied. The results suggest that coconut coir is a cost effective and efficient bio-sorbent for La3+ ion adsorption from aqueous solution.