Fitted Isotherm Model Research Articles

Activated Carbon/Pectin Composite Enterosorbent for Human Protection from Intoxication with Xenobiotics Pb(II) and Sodium Diclofenac.

The use of enterosorbents—materials which can be administered orally and eliminate toxic substances from the gastrointestinal tract (GIT) by sorption—offers an attractive complementary protection of humans against acute and chronic poisoning. In this study, we report the results of developing a microgranulated binary biomedical preparation for oral use. It was designed with a core-shell structure based on pectin with low degree of esterification as the core, and nanoporous activated carbon produced from rice husk, AC-RH, as the shell, designated as AC-RH@pectin. The adsorption properties of the synthesized materials were studied in aqueous solutions for the removal of lead (II) nitrate as a representative of toxic polyvalent metals and sodium diclofenac as an example of a medicinal drug. The composite enterosorbent demonstrated high adsorption capacity for both adsorbates studied. Adsorption kinetics of lead and diclofenac adsorption by AC-RH, pectin, and AC-RH@pectin, fitted well a pseudo-second-order model. According to the Langmuir adsorption isotherm model, the best fitted isotherm model, the maximum adsorption capacity, qmax, of AC-RH@pectin for diclofenac and for lead (II) was 130.9 mg/g and 227.8 mg/g, respectively. Although qmax of AC-RH for diclofenac, 537.6 mg/g, and qmax of pectin for lead (II), 245.7 mg/g, were higher, the maximum adsorption capacity of AC-RH for lead (II), 52.7 mg/g, was much lower than that of the composite AC-RH@pectin and the adsorption capacity of pectin for diclofenac was negligible. Therefore, the composite material AC-RH@pectin demonstrated substantial efficiency of removing both species which potentially defines it as a more universal enterosorbent suitable for treating poisoning caused by substances of different chemical nature.

Removal of Mn 2+ in geothermal water by manganese sand: process and mechanisms

Geothermal water resources are being exploited widely in many areas to relieve pressure on water resources generally. Excessive Mn 2+ concentration in geothermal water will seriously reduce its utilization rate. Therefore, this study investigated the removal of Mn 2+ from simulated geothermal water by manganese sand. The Mn 2+ removal rate from simulated water with a concentration of 10 mg l −1 by 2 g manganese sand at 298, 323, 343 and 363 K was more than 90%. The removal efficiency of Mn 2+ is influenced by adsorbent dosage, adsorbent particle size, initial Mn 2+ concentration and competing ions, and less so by a pH of 5–9. A pseudo-first-order kinetic model fits the adsorption data better than a pseudo-second-order model. The pseudo-first-order adsorption rate constants (K 1 ) ranged from 0.14 to 0.5 h −1 as the temperature increased from 298 to 363 K. The Langmuir isotherm model fits the adsorption data better than the Freundlich and Temkin isotherm models. The maximum monolayer adsorption capacities ( q m ) obtained by the Langmuir isotherm model fitting were 0.91/1.02/1.22/1.23 mg g –1 at 298/323/343/363 K. Thermodynamic studies revealed that the adsorption was endothermic and physical in nature. These findings suggest that the potential of manganese sand for removing Mn 2+ in geothermal water is considerable. Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues

Synthesis and Characterization of a Magnetic Carbon Nanofiber Derived from Bacterial Cellulose for the Removal of Diclofenac from Water.

Engineering and synthesis of novel materials are vital for removing emerging pollutants, such as pharmaceuticals from contaminated water. In this study, a magnetic carbon nanofiber (MCF) fabricated from bacterial cellulose was tested for the adsorption of diclofenac from water. The physical and chemical properties of the synthesized adsorbent were examined by field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, energy-dispersive X-ray spectroscopy (EDS), a vibrating sample magnetometer (VSM), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The characterization results showed that the MCF is a carbon nanofiber with a three-dimensional interconnect network, forming a porous material (mesopores and macropores) with a specific surface area of 222.3 m2/g. The removal of diclofenac (10 mg/L) by the MCF (0.75 g/L) was efficient (93.2%) and fast (in 20 min). According to the Langmuir isotherm model fitting, the maximum adsorption capacity of the MCF was 43.56 mg/g. Moreover, continuous adsorption of diclofenac onto MCF was investigated in a fixed-bed column, and the maximum adsorption capacity was found to be 67 mg/g. The finding of this research revealed that the MCF could be a promising adsorbent used to remove diclofenac from water, while it can be easily recovered by magnetic separation.

Aluminium hydroxide impregnated sawdust adsorbent: An eco-friendly and low-cost strategy for defluoridation of water

Environment-friendly and cost-effective adsorbent is necessary for removal of excess fluoride from water to control the spread of fluorosis among people in fluoride-rich area. Plant-based cellulosic materials are the preferred choice for this purpose. In this work, aluminium hydroxide impregnated sawdust (AHSD) adsorbent has been prepared, characterized and applied for defluoridation of water through batch and fixed-bed adsorption. Fluoride adsorption capacity of AHSD in batch adsorption experiment is 4.45 mg/g for the initial fluoride concentration between 5-50 mg/L. At low fluoride concentration, the Freundlich isotherm model fit reasonably well, while at higher fluoride concentration (> 40 mg/L) the Langmuir model show better fitting with the experimental data. The adsorption kinetics follow pseudo second-order kinetic model. In fixedbed column adsorption, 4 g of the adsorbent is capable of bringing down the fluoride concentration from 5 mg/L to < 1.5 mg/L (WHO limit) for 690 mL of contaminated water. Residual aluminium in the treated water was within permissible limit of WHO. The reasonably good adsorption capacity and effectivity in both batch and fixed-bed column adsorption suggests that AHSD is an environment-friendly, cost-effective and promising adsorbent for defluoridation of water.

Removal of Thymol Blue from Aqueous Solution by Natural and Modified Bentonite: Comparative Analysis of ANN and ANFIS Models for the Prediction of Removal Percentage

In this study natural bentonite (NB) and acid-thermal co-modified bentonite (MB) were utilized as adsorbents for the removal of Thymol Blue (TB) from aqueous solution. The batch adsorption experiments were conducted under different experimental conditions. The artificial neural network (ANN) and adaptive neuro fuzzy inference systems (ANFIS) were applied to estimate removal percentage (%) of TB. Mean squared error (MSE), root mean square error (RMSE) and coefficient of determination (R2) values were used to evaluate the results. In addition, the experimental data were fitted isotherm models (Langmuir, Freundlich and Temkin) and kinetic models (pseudo first order (PFO), pseudo second order (PSO) and intra-particle diffusion (IPD)). The adsorption of TB on both the NB and MB followed well the PSO kinetic model, and was best suited Langmuir isotherm model. When the temperature was increased from 298 K to 323 K for 20 mg/L of TB initial concentration, the removal percentage of TB onto the NB and MB increased from 74.91% to 84.07% and 81.19% to 93.12%, respectively. This results were confirmed by the positive ΔH° values indicated that the removal process was endothermic for both the NB and MB. The maximum adsorption capacity was found as 48.7805 mg/g and 117.6471 mg/g for the NB and MB, respectively (at 323 K). As a result, with high surface area and adsorption capacity, the MB is a great candidate for TB dye removal from wastewater, and the ANFIS model is better than the ANN model at estimating the removal percentage of the dye.

Key particle properties of shells for cadmium chemisorption

Previous studies on cadmium adsorption of calcium carbonate have found that polymorph, and, crystallinity are influential factors for adsorbing cadmium ions. The predominant factor for cadmium adsorption has yet to be elucidated because these factors are linked. To overcome this, here each factor is investigated separately. First, atmospheric grinding prepared surf clam (aragonite phase) and scallop (calcite phase) shells with similar crystallite sizes and specific surface areas. Using adsorption isotherm models, kinetics, X-ray diffraction analysis, and TEM observations, both calcite and aragonite react with cadmium to form cadmium carbonate. The chemisorption follows the adsorption mechanism reported in the literature. Based on the Langmuir isotherm model fitting, the maximum adsorbed amount for the ground surf clam shells is 633.3 mg/g, while that for scallop shells is 195.8 mg/g. Then fine surf clam shell particles with a similar specific surface area, and with a relatively wide range of the aragonite ratio, and crystallite size are prepared via a combination of grinding and a subsequent calcination process. Our experiments where one explanatory variable is changed at a time demonstrate that the polymorph ratio and crystallite size of the ground shells play key roles in the chemisorption.

Fabrication of aluminum beads derived from selectively recovered Al-rich precipitates and their application into defluoridation.

This work introduced a new way of fabricating a granular material with the supply of Al-rich precipitates selectively obtained from acid mine drainage (AMD), and its potential as a promising adsorbent for fluoride (F) was evaluated. Through the selective sequential precipitation (SP) process in the field, Al-rich precipitates with high purity (>81%) were collected at the high recovery rate (>99.8%) as a raw material for adsorbent fabrication. The granular adsorbent (ALB) was synthesized through encapsulation of precipitate powders by chemically inducing polymeric bead formation. The characterization results revealed that ALB possessed a highly porous structure and embedded a large number of nanoparticles of amorphous Al hydroxides inside its framework. Less adsorption of F occurred at an alkaline pH condition due to the competitive effect of hydroxyl ions. The adsorption process can be divided into fast adsorption by the outer surface and slow diffusion in the inner phase. The maximum adsorption capacity of ALB for F was calculated to be 17.7 mg g-1 in the Langmuir isotherm model fitting results. By the repetitive adsorption/desorption and XPS results, it turned out that both chemisorption and physisorption gave a contribution in the removal of F, and the regeneration of adsorbent using NaOH was effective to restore the adsorption capability but accompanied the loss of adsorption sites. As a result, it can be concluded that a granule-type material fabricated using Al-rich precipitates selectively recovered from AMD neutralization can be considered as a promising adsorbent for F removal in aqueous solution.

Phosphate recovery from aqueous solution through adsorption by magnesium modified multi-walled carbon nanotubes

In this study, multi-walled carbon nanotubes modified by magnesium (Mg@CNT) was prepared as a novel adsorbent to recover phosphate from wastewater. Mg@CNT with the mass ratio of 0.48 (Mg versus MWCNTs) was the most efficient for phosphate adsorption and the maximum experimental adsorption capacity was up to 198 mg P/g. The Mg@CNT characterization was done by Field emission scanning electron microscope coupled with energy-dispersive spectroscopy detector (FESEM-EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), surface area analyzer (BET), Transmission electron microscope coupled with energy-dispersive spectroscopy detector (TEM-EDS). The MgO nanoflakes spread on the surface of multi-walled carbon nanotubes and reacted with phosphate to generate Mg3(PO4)2·10H2O as the end product. Phosphate adsorption on Mg@CNT was chemisorption onto heterogeneous surface according to the kinetic model and isotherm model fitting results. Several common co-existing ions, e.g., Cl−, NO3− and humic acid, had no obvious negative impact on the phosphate adsorption capacity; while SO42− and CO32− expressed stronger negative impacts and led to 13.2% and 39.5% decrease in phosphate adsorption capacity, respectively. After five adsorption-desorption cycles, Mg@CNT still maintained more than 80% adsorption capacity of the initial and high phosphate desorbability. These results implied that Mg@CNT possessed great application potential in phosphate recovery.

Removal of pharmaceuticals from aqueous samples by adsorption using pristine polypyrrole as adsorbent: kinetic, isothermal and thermodynamic studies

ABSTRACT Conductive polymers have been used as adsorbents to remove organic pollutants from aqueous samples. In this study, pristine polypyrrole (PPy) was used for the first time in the removal of potassium diclofenac (PD) and moxidectin (MOX) from aqueous solutions.PPy was properly characterised by scanning electron microscopy, thermogravimetric analysis, infrared spectroscopy, textural properties, wettability, and point zero charge. Through the characterisation results, it was observed that the adsorbent showed be favourable to adsorption, high temperature of thermal degradation, bands characteristic of the PPy,mesopore structures, and hydrophilicity. The results pointed that pH 6 favoured the removal, reaching percentages of 95.26% for PD and 99.75% for MOX.The kinetic data followed the model of pseudo second-order (PD: R2 = 0.872 and MOX: R2 = 0.887) with equilibrium reached in 20 min for PD and MOX. OThe best fit isotherm model was the dual-site Langmuir-Freundlich (R2 > 0.99), with maximum capacity adsorption of 221.23 mg g−1 for PD and 87.46 mg g−1 for MOX. Finally, the thermodynamic study showed that the adsorption process was spontaneous and endothermic. Through the reuse study, it was possible to show a good cost-benefit ratio when using the developed adsorbent material, since it can be used several times without losing its adsorption capacity. Finally, PPy showed great potential to be used in the adsorption of compounds with different physicochemical properties.

Direct Yellow 8 Azo Removal by Bentonite Clay Solution: Experimental and Theoretical Studies

In the theoretical part, removal of direct yellow 8 (DY8) from water solution was accomplished using Bentonite Clay as an adsorbent. Under batch adsorption, the adsorption was observed as a function of contact time, adsorbent dosage, pH, and temperature. The equilibrium data were fitted with the Langmuir and Freundlich adsorption models, and the linear regression coefficient R2 was used to determine the best fitting isotherm model. thermodynamic parameters of the ongoing adsorption mechanism, such as Gibb's free energy, enthalpy, and entropy, have also been measured. The batch method was also used for the kinetic calculations, and the day's adsorption assumes first-order rate kinetics. The kinetic studies also show that the intraparticle diffusion process was active. Density Functional Theory (DFT) was used to study the dye structure with Gaussian 09 and predict the active site in a molecule using total electron density (TED) and electrostatic surface potential (ESP).

Facile preparation of iron oxyhydroxide–biopolymer (Chitosan/Alginate) beads and their comparative insights into arsenic removal

• Facile synthesis of bionanocomposite beads performed to remove arsenic from water. • Comparative analysis of the beads performed using two different biopolymers. • In-situ inorganic nanoparticle formation in polymer beads showed better As removal. • IICB showed higher adsorption efficiency for As(V) and As(III) spiked groundwater. • Insignificant metal leaching observed during regeneration and reuse of beads. Bare iron-based nanoadsorbents have been explored extensively for arsenic removal owing to the inherent affinity of iron for arsenic. However, bare nanoparticles have poor hydraulic properties and tend to agglomerate when used as adsorbents. Encapsulation of nanoparticles into polymeric materials is a safer way to restrict the transportation of highly reactive nanoparticles in the surrounding media without compromising the efficiency of these adsorbents. This study presents a modified method for synthesizing bionanocomposite beads intending to achieve optimal dispersion of nanoparticles throughout the biopolymer. In-situ iron oxyhydroxide alginate beads (IIAB) and chitosan beads (IICB) were prepared via gradual precipitation of ferric ions within the polymeric gel matrix. Electron microscopy images were used for morphological analyses of beads. Batch trials were conducted to assess the effect of dose, pH, contact time, and ionic strength on arsenic adsorption. Maximum adsorption capacities obtained via Langmuir isotherm model fitting were in the following order: IICB for As (V) > IICB for As (III) > IIAB for As (V) > IICB for As (III). 1.2 g/L of IICB and 2 g/L of IIAB were found to be sufficient for treatment of arsenic spiked groundwater. FTIR and XPS analyses reveal the role of hydroxyl and amino groups in the adsorption process. Spent beads could be easily harvested, regenerated using 0.1 M NaOH, and used for multiple cycles without significant leaching.

Testing of electron beam irradiated sheep wool for adsorption of Cr(III) and Co(II) of higher concentrations

Electron beam irradiated sheep wool dosed (0–410) kGy showing good adsorption properties was tested for Cr(III) and Co(II) of higher concentrations. Fitting to ten isotherm models was examined as follows: Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Flory-Huggins, Halsey, Harkins-Jura, Jovanovic, Elovich and Redlich-Peterson. Both cations being Lewis acids generate complex salts, such as carboxylates or cysteinates, with ligands from keratin. Various composition and architecture of the complexes are responsible for different isotherm model fitting. The chromic cation showed adherence to Freundlich, Temkin, Halsey, Harkins-Jura and Jovanovic models for all or almost all dosed samples unlike cobaltous cation matching Langmuir, Flory-Huggins and Redlich-Peterson isotherm models. No model fitted the both examined cations simultaneously. On the contrary, simultaneously non-fitting to all dosed samples was observed for Elovich and partially Dubinin-Radushkevich models.

Adsorptive removal of diclofenac sodium from aqueous solution onto sycamore ball activated carbon – isotherms, kinetics, and thermodynamic study

This study reports the analysis data of diclofenac sodium adsorption on sycamore ball activated carbon surface, in which various parameters such as adsorbent dosage, initial diclofenac sodium concentration, temperature, and pH were analyzed. At 25°C, adsorbent dosage was used the range from 2.5 mg/50mL to 30 mg/50mL, and initial diclofenac concentration was taken from 10 mg/L to 50 mg/L. For adsorption temperature effect, adsorption temperature was investigated from 25°C to 45°C by holding adsorbent dosage constant (10 mg/50mL). By holding constant adsorbent dosage of 10 mg/50mL, contact time effect from 0 to 210 min was investigated with initial DS concentrations of 10, 20, 30, 40, and 50 mg/L. To examine pH effect, pH parameters were adjusted from 2.84 to 10.20. Besides, adsorption isotherm model, kinetic and thermodynamic studies carried out in this study are given. Langmuir isotherm model was determined to be the best fitting isotherm model for diclofenac sodium adsorption on sycamore ball activated carbon. Also, the maximum sodium diclofenac adsorption on sycamore ball activated carbon was calculated 178.89 mg/g at 25°C, and kinetic data displayed that this adsorption occurred quite fast. Pseudo-first and pseudo-second order models were applied for sodium diclofenac adsorption on sycamore ball activated carbon, and the correlation coefficient values of 1.000-0.998 indicate that this adsorption was well fitting with pseudo-second order model. Moreover, from the thermodynamic study, sodium diclofenac adsorption on sycamore ball activated carbon was found to be exothermic, spontaneous, and feasible. Thus, the results obtained from this study confirmed that sycamore ball activated carbon is an economically suitable and effective adsorbent for sodium diclofenac adsorption.

Comparison of adsorption behaviors and mechanisms of methylene blue, Cd2+, and phenanthrene by modified biochars derived from pomelo peel.

Although biochar (BC) has been widely used to adsorb pollutants in environment due to its natural and green characteristics, the structural defects of BC limit the ability to remove various environmental pollutants in aqueous solution. In this study, oxidized biochar (OBC) and sulfhydryl biochar (SBC) derived from pomelo peel (PP) were prepared through an oxidation and esterification reaction. BC and modified BC were used for the removal of methylene blue (MB), Cd2+, and phenanthrene (PHE) in aqueous solution. The adsorption behavior and efficiency toward different types of pollutants were studied by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Raman, X-ray photoelectron spectroscopy (XPS), kinetics, and isotherm model fitting. The results showed that the change of pH had great effect on MB and Cd2+ adsorption, but not on PHE. SBC not only possessed the newly formed sp2-hybridized domains with easy access to aromatic pollutants but also had multiple functional groups (-COOH, -OH, -SH, -NH2) that provided adsorption sites for positively charged pollutants. SBC was more flexible and efficient in purifying pollutants compared to BC and OBC, with the saturated adsorption capacities of MB (209.16 mg/g), Cd2+ (786.19 mg/g), and PHE (521.58 mg/g). Moreover, the adsorption kinetic and isotherms fitting showed that the adsorption mechanisms were closely related to the structure of biochar and the properties of pollutants, including π-π interaction, surface charge, electrostatic interaction, surface functional groups, and Van der Waals force. In addition, the analysis of structure-function relationship demonstrated the enhanced hydrophilicity and the easy exposure of the binding sites on OBC and SBC. Hence, it was significantly effective to regulate microstructure and interfacial properties to promote its adsorption behaviors of biochar.

Competitive removal of cadmium and lead ions from synthetic wastewater using Kappaphycus striatum

The main aim of this study was focused on modeling of simultaneous biosorption of Cd2+ and Pb2+ ions from aqueous solution using Kappaphycus striatum. The effect of process parameters (pH, biosorbent dosage, temperature, initial metal ion concentration, and time) on biosorptive efficiency was examined. The greatest removal efficiency of Pb2+ ions (97.82 %) and Cd2+ ions (86.73 %) was observed at pH 4 and 5, respectively. For simultaneous removal of Pb2+ and Cd2+ ions, the optimum values of process parameters were chosen as biosorbent dosage (1 g/L), pH (5.0), and temperature (30 °C). The equilibrium has been achieved at 60 min. The total removal percent was 45.77 % for total 350 mg/L Pb2+ and Cd2+ ions mixture. The single metal ion biosorption study was done to obtain the parameters which were required for multicomponent biosorption isotherms. For single metal ion system six isotherm models were fitted to experimental data. The best fitted isotherm model for Cd2+ and Pb2+ ions was Fritz and Radke-Prausnitz, respectively. Six multicomponent isotherm models were analyzed to determine the best fitted isotherm model for multicomponent system by minimizing Average Relative Error function. For multicomponent biosorption system, extended Freundlich was found to be the best fitted model. In this study, the mutual effect of both metal ions on Kappaphycus striatum was antagonistic. The biosorption of both metal ions followed pseudo-second order kinetics which shows the chemisorption mechanism. Thermodynamic study confirmed the spontaneous, feasible, and endothermic nature of Cd2+ and Pb2+ ions biosorption on Kappaphycus striatum.

Removal of reactive black 5 dye by using polyoxometalate-membrane

A POM-membrane was fabricated by immobilizing a keggin type polyoxometalate (POM) H5PV2Mo10O40 onto the surface of microporous flat-sheet polymeric polyvinylidene fluoride (PVFD) membrane using a chemical deposition method. The POM-membrane was characterized by FT-IR, SEM and EDX to confirm existing of the POM onto the membrane surface. The POM-membrane was used to remove an anionic textile dye (Reactive Black 5 named as an RB5) from aqueous phases with a cross-flow membrane filtration and a batch adsorption system. The dye removal efficiency of the POM-membrane using the cross-flow membrane filtration system and the batch adsorption system was about 88% and 98%, respectively. The influence factors such as contact time, adsorbent dosage, pH, and initial dye concentration were investigated to understand the adsorption mechanism of the RB5 dye onto the POM-membrane. To find the best fitting isotherm model, Langmuir, Freundlich, BET and Harkins-Jura isotherm models were used to analyze the experimental data. The isotherm analysis showed that the Langmuir isotherm model was found to the best fit for the adsorption data (R 2=0.9982, qmax=24.87 mg/g). Also, adsorption kinetic models showed the pseudo second order kinetic model was found the best model to fit the experimental data (R2=0.9989, q=8.29 mg/g, C0=15 ppm). Moreover, after four times regeneration with HNO3 acid, the POM-membrane showed high regenerability without losing dye adsorption capacity.

Performance characterization of nanofiltration, reverse osmosis, and ion exchange technologies for acetic acid separation

A major obstacle to widespread implementation of bio-based fuels and chemicals is the lack of efficient and cost-effective separation methods. To purify acetic acid produced by biochemical conversion of biomass via anaerobic digestion, this work employs two commonly used separation technologies: (1) ion-exchange (IX) resin and (2) pressure-driven membranes. This study tested five commercially available strong- and weak-base anion-exchange resins and five commercially available nanofiltration (NF) and reverse osmosis (RO) membranes. The pH of the feed solution significantly affected adsorption capacity. At pH 6.3, a strong-base IX resin (IRN-78) performed best (95.1% acetate removal). With strong-base IX resins, the Langmuir isotherm model fit well, whereas for weak-base IX resins, the Freundlich isotherm provided a better fit. A pseudo-second-order kinetic model fit well for both IRN-78 and IRA-67. Regarding membrane separation, RO (BW30XFR membrane) achieved the highest rejection (98.6% acetate rejection), whereas an NF membrane (NF*) achieved the best combination of permeate flux (105 L/(h·m2)) and rejection (83.1% acetate rejection). For membrane performance, the experimental data were fit using the solution diffusion model. Increased pH in the feed solution lowered permeate flux but increased acetic acid rejection. When the acetic acid concentration in the feed solution increased, both permeate flux and acetic acid rejection decreased for membrane NF*.

Highly efficient removal of aluminum, iron, and manganese ions using Linde type-A zeolite obtained from hazardous waste

Coal acid mine drainage (AMD) contaminates natural water to form mine-impacted water (MIW), which is characterized by high levels of acidity, sulfate, and metallic ions. This study investigates the use of a Linde Type-A (LTA) zeolite obtained from a hazardous industrial waste for Al3+, Fe2+, and Mn2+ removal from synthetic aqueous solutions. The aim of this study is to stablish a basis for the subsequent treatment of MIW in order to obtain reuse water. In a central composite rotatable design (CCRD) study, 8.25 g L−1 zeolite and 147 rpm were the optimal conditions for treating the multicomponent solution, yielding 99.9, 99.9 and 99.3% removal for Al3+, Fe2+, and Mn2+, respectively. Isothermal studies showed that the affinity of the ions by the zeolite were ranked as Al3+>Mn2+>Fe2+. The best fitting isothermal models for monocomponent solutions were Tóth, Freundlich, and Sips for Al3+, Fe2+, and Mn2+, respectively. In the multicomponent solution, Sips and Freundlich were the better fitting models for Al3+ and Mn2+, respectively, indicating a weakness of the sorbate-sorbent interactions. Kinetic studies revealed that the quantitative removal of Al3+ was achieved in 5 min. The multicomponent solution was transformed into water that was suitable for non-potable use after an optimal time of 60 min. The results demonstrate that LTA zeolite synthetized from hazardous waste has a high potential for remediating contaminated water by metallic ions at low dosages and short times. Using LTA zeolite for remediating contaminated water could make a positive contribution to the circular economy and environmental sustainability.

Adsorption Equilibrium and Thermodynamic Studies of Ciprofloxacin from Aqueous Solutions by Magnetic Bentonite Nanocomposites

Objectives: Today, due to increasing usage of antibiotics and their destructive effects on health and environment, it is necessary to remove them from receiving waters. Although there are few studies on the use of magnetic nanocomposites for removal of different antibiotics, but the effect of this adsorbent on the removal of Ciprofloxacin (CIP) has not been evaluated yet. Therefore, this study was conducted to investigate the removal of CIP by magnetic Bentonite nanocomposites (Fe3O4- BNP) as an adsorbent. Methods: Batch studies were performed to evaluate and optimize the effects of various parameters such as contact time, temperature of the solution, CIP concentrations and Fe3O4-BNP dosage. The adsorbent characteristics were determined using SEM and FT-IR spectroscopy. Also, the adsorbent surface area was measured by BET technique. Results: the optimal values for the factors affecting CIP removal were calculated. It was revealed that the maximum CIP removal was obtained at pH = 7, temperature = 55°C, CIP concentration = 10 mg/L, Fe3O4-BNP dosage = 1.25 g/L and contact time= 90 min. The maximum removal percentage was 99.25%. It was also revealed that Langmuir isotherm is the best fitted isotherm model. The thermodynamic parameters like ΔG0, ΔH0 and ΔS0 changes for the adsorption of CIP have also been computed and discussed. The heat of adsorption implied that the adsorption was exothermic in nature. Conclusion: The Fe3O4-BNP was successfully applied for the uptake of CIP from industrial wastewater and separated easily by means of magnetic separation.

Characterization of cobalt ferrite-supported activated carbon for removal of chromium and lead ions from tannery wastewater via adsorption equilibrium

In this experiment, cobalt ferrite-supported activated carbon (CF-AC) was developed and characterized via the wet impregnation method for the removal of Cr and Pb(II) ions from tannery wastewater. Batch adsorption was carried out to evaluate the effect of experimental operating conditions (pH of solution, contact time, adsorbent dose, and temperature), and the removal efficiencies of Cr and Pb(II) ions by the developed adsorbents were calculated and recorded for all experimental conditions. These variables were estimated and reported as removal efficiencies of 98.2% for Cr and 96.4% for Pb(II) ions at the optimal conditions of 5, 0.8 g, 80 min, and 333 K for pH, adsorbent dose, contact time, and temperature, respectively. The equilibrium for the sorption of Cr and Pb(II) ions was studied using four widely used isotherm models (the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models). It was found that the Freundlich isotherm model fit better with the coefficient of determination (R2) of 0.948 4 and a small sum of square error of 0.000 6. The maximum adsorption capacities (Qm) of Pb(II) and Cr adsorbed onto CF-AC were determined to be 6.27 and 23.6 mg/g, respectively. The adsorption process conformed well to pseudo-second order kinetics as revealed by the high R2 values obtained for both metals. The thermodynamic parameters showed that adsorption of Cr and Pb(II) ions onto CF-AC was spontaneous, feasible, and endothermic under the studied conditions. The mean adsorption energy (E) values revealed that the adsorption mechanism of Cr and Pb(II) by CF-AC is physical in nature. The results of the study showed that adsorbent developed from CF-AC can be efficiently used as an environmentally friendly alternative adsorbent, for removal of Cr and Pb(II) ions in tannery wastewater.