Non-linear Isotherm Models Research Articles

Process optimization and enhancement of pesticide adsorption by porous adsorbents by regression analysis and parametric modelling

In the present study, the adsorptive removal of organophosphate diazinon pesticide using porous pumice adsorbent was experimentally investigated in a batch system, modelled and optimized upon response surface methodology (RSM) and artificial neural network-genetic algorithm (ANN-GA), fitted to isotherm, kinetic and thermodynamic models. The quantification of adsorbent elements was determined using EDX. XRD analysis was utilized to study the crystalline properties of adsorbent. The FT-IR spectra were taken from adsorbent before and after adsorption to study the presence and changes in functional groups. The constituted composition of the adsorbent was determined by XRF. Also, the ionic strength and adsorbent reusability were explored. The influences of operational parameters like pH, initial pesticide concentration, adsorbent dosage and contact time were investigated systematically. ANN-GA and RSM techniques were used to identify the optimal process variables that result in the highest removal. Based on the RSM approach, the optimization conditions for maximum removal efficiency is obtained at pH = 3, adsorbent dosage = 4 g/L, contact time = 30 min, and initial pesticide concentration = 6.2 mg/L. To accurately identify the parameters of nonlinear isotherm and kinetic models, a hybrid evolutionary differential evolution optimization (DEO) is applied. Results indicated that the equilibrium adsorption data were best fitted with Langmuir and Temkin isotherms and kinetic data were well described by pseudo-first and second-order kinetic models. The thermodynamic parameters such as entropy, enthalpy and Gibbs energy were evaluated to study the effect of temperature on pesticide adsorption.

Efficient removal of congo red dye using Fe3O4/NiO nanocomposite: Synthesis and characterization

In the present study, the adsorption of congo red (CR) using Fe3O4/NiO magnetic nanocomposites synthesized via a precipitation method was studied. XRD, EDS, FTIR, TEM, BET, and SEM techniques were used to obtain their specifications. The influence of solution pH, adsorbent dosage, time of experiments, initial concentration of CR, and the temperature has been checked. Among the non-linear isotherm models studied, Langmuir with qm=210.78 mg/g at 293 K and R2=0.9983 showed the highest agreement with laboratory results compared to Freundlich, Jovanovic, Halsey, and Temkin models. The results also showed the congo red’s adsorption process on Fe3O4/NiO nanocomposite follows the pseudo-second-order kinetic model. Further, temperature and thermodynamic studies’ effect was carried out, and results showed spontaneously and exothermically the adsorption process. Overall, Fe3O4/NiO nanocomposite, due to low equilibrium time and high adsorption capacity, could remove congo red from contaminated water.

Closing the loop: As(V) adsorption onto goethite impregnated coal-combustion fly ash as integral building materials

Fly and bottom ash(es) are the most abundant generated by-products of coal combustion in thermal power plants. This investigation offers a sustainable solution of a double and circular use of industrial waste material in civil engineering practices; i.e., fly ash (FA) as an eco-efficiently, low-cost material for As(V) adsorption, as well as an additive in building materials. A goethite impregnated sample (FAG) was synthesized and optimized using the column precipitation procedure, then thoroughly, structurally and morphologically characterized using liquid nitrogen porosimetry (BET), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Mössbauer spectroscopy (MS) techniques. The data from the equilibrium adsorption were fitted by linear and non-linear isotherm models; the optimal capacity of FAG/As(V) removal was calculated from the Langmuir model at 31.742 mg g−1 for 45 °C. The kinetics of adsorption process has shown the pseudo-second-order kinetic model (PSO). The Weber-Morris model was applied to determine the intra-particle diffusion as a limiting step of reaction. The low pH dependant FAG leaching confirmed the efficient use of non-hazardous waste material in arsenic removal; furthermore, it also validated the new added value of the used/spent adsorbent as an adhesive in building materials possessing advanced mechanical properties.

Preparation of a Fungal-Modified Material Linked by the Monoamidoxime Terminal Open-Chain Polyether and Its Uranyl Adsorption

In this study, some synthetic methods of condensation, substitution, and amidoxime reaction were used to prepare a kind of new fungal-modified material containing the monoamidoxime terminal open-chain polyether, and its microstructure and morphology were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller analysis, and thermogravimetric analysis. The single-factor method was used to preliminarily investigate uranium(VI) adsorption capacity of the target material influenced by some factors. On this basis, then the orthogonal experiment was applied to further obtain the optimal adsorption conditions (initial U(VI) concentration: 40 mg L–¹, solid–liquid ratio: 25 mg L–¹, initial pH value: 6.0, and contact time: 130 min) and the maximum adsorption capacity (295.48 mg g–¹). The cyclic adsorption–desorption and anti-interference experiments showed that the target material had good regeneration and uranyl selectivity adsorption performance. Langmuir (nonlinear) (R² = 0.9704) and Freundlich (nonlinear) (R² = 0.9675) isotherm models and a pseudosecond-order kinetic model (linear) (R² = 0.9922) were closely fitted with experimental data, and the uranyl-loaded mechanism should be mainly the monolayer and chemical adsorption process.

Methylene blue contaminated water sanitization with alginate/compact discs waste-derived activated carbon composite beads: Adsorption studies

The adsorption behavior of different adsorbents has been studied by various research works. But few studies have compared linear and non-linear isotherm and kinetic models alongside phenomenological coefficients. Here, the effect of activated carbon black (ACB) on the methylene blue adsorption behavior of alginate was examined. A low-cost and green adsorbent was fabricated to can easily be detached from water. For this aim waste compact discs were recycled for the preparation of ACB. Loading of 15 wt% ACB related to pure alginate increased removal yield of alginate significantly. Isotherms and kinetic models in linear and non-linear forms were studied and the results were examined by comparing R2 along with different error function values to find the best fitting. The results were well matched with non-linear pseudo-second-order and linear Langmuir. Intraparticle diffusion model and phenomenological coefficients represented control of adsorption by film diffusion and its limiting by pore diffusion.

Synthesis of DMEA-Grafted Anion Exchange Membrane for Adsorptive Discharge of Methyl Orange from Wastewaters.

This manuscript describes the synthesis of dimethylethanolamine (DMEA)-grafted anion exchange membrane (AEM) by incorporating dimethylethanolamine as ion-exchange content into the polymer matrix via the solution casting method. The synthesis of the DMEA-grafted AEM was demonstrated by Fourier transform infrared (FTIR) spectroscopy. The prepared DMEA-grafted AEM exhibited higher thermal stability, homogeneous morphology, water uptake (WR) of 115%, and an ion exchange capacity (IEC) of 2.70 meq/g. It was used for the adsorptive removal of methyl orange (MO) from an aqueous solution via batch processing. The effect of several operating factors, including contact time, membrane dosage, initial concentration of aqueous dye solution, and temperature on the percentage discharge of MO and adsorption capacity, was evaluated. Experimental data for adsorption of MO onto the DMEA-grafted AEM was analyzed with two parameter and three parameter nonlinear adsorption isotherm models but fitted best using a nonlinear Freundlich isotherm. Adsorption kinetics were studied by using several models, and attained results showed that experimental data fitted well to pseudo-second-order kinetics. A thermodynamic study showed that adsorption of MO onto the prepared DMEA-grafted AEM was an endothermic process. Moreover, it was a feasible and spontaneous process.

Enhanced adsorption of heavy metals in groundwater using sand columns enriched with graphene oxide: Lab-scale experiments and process modeling

In this study, sand enriched with graphene oxide (GO) was applied as the medium to prevent heavy metals migration to groundwater. The retention of heavy metals including Cr(VI), As(III), Cd(II), and Pb(II) in the prepared medium was investigated. Batch experiments results revealed that the adsorption capacities of GO were 530.85, 170.1, 49.78, and 14.41 mg g−1 for Pb(II), Cd(II), As(III), and Cr(VI). The adsorption characteristics of GO were investigated by four linear and nonlinear isotherm models. Nonlinear Freundlich was the best model fitting the experimental observations in equilibrium reactions. The presence of GO enhanced adsorption capacity of the sand column to 92, 87, 88, and 94 % for Pb(II), Cd(II), As(III), and Cr(VI), respectively. The retention of single component and a mixture of heavy metals in the prepared medium was studied, showing that in the mixture of metals, the adsorption capacity of GO reduced by 14, 21, and 39 % for Pb(II), Cd(II), and As(III), respectively. A longer breakthrough time for GO was achieved for Pb(II) (10.83 h) and Cd(II) (4.23 h), indicating higher efficiency of the reactive medium in the retention of Pb(II) and Cd(II). Thomas and Adam’s–Bohart kinetic models were applied to express the dynamic characteristics of the proposed medium. Breakthrough curves of Cr(VI), Cd(II), and Pb(II)were successfully predicted by Thomas model, while that of As(III) was described better by Adam’s–Bohart model. This can be associated with the fact that the Thomas model assumes Langmuir isotherm, while adsorption behavior of As(III) was well-depicted by Freundlich isotherm.

Application of a novel nanocomposites carbon nanotubes functionalized with mesoporous silica-nitrenium ions (CNT-MS-N) in nitrate removal: Optimizations and nonlinear and linear regression analysis

Abstract In recent years, the increase in the use of agricultural fertilizers in industrial development has produced poisonous inorganic ions such as nitrates in water and soil. Nitrates in drinking water which may come from nitrogen fertilizers are a potential health risk. Removal of nitrates from the environment is a big challenge. Following the series of investigation, the present study proposes the multiwall carbon nanotubes functionalized with mesoporous silica-nitrenium ions (CNT-MS-N) as a novel adsorbent for removing nitrate ions (NO 3 − ) from aqueous solution. The ability of CNT-MS-N to remove nitrate ions from aqueous solutions was studied at different operating conditions. The maximum removal (98%) was obtained under the optimum conditions: adsorbent dosage of 70 mg and pH 7 and for initial concentration of 80 (ppm) at 30 °C for 5 h contact time. FTIR spectroscopy showed the contribution of amine, amide groups in removing nitrate and the FESEM-EDX results confirmed the adsorption of nitrate ions on the function groups of CNT-MS-N. In addition, nonlinear and linear isotherms and kinetics models were used to evaluate the equilibrium adsorption results. The coefficient of determination (R2) was used to determine the best-fit model expected by each approach. The results showed that the non-linear Langmuir isotherm model is a better way to achieve adsorption parameters illustrating the adsorption of nitrate ions onto CNT-MS-N with R2 (0.9829). Likewise, it was found that the nonlinear Pseudo-second order rate model using the non-linear regression approach better predicted experimental results with R2 (0.9921). The present investigation confirmed the nonlinear method as an appropriate technique to predict the optimum adsorption isotherm and kinetic data.

Equilibrium Isotherms, Kinetics, and Thermodynamics of the Adsorption of 2,4-Dichlorophenoxyacetic Acid to Chitosan-Based Hydrogels

The aim of this work was to study the equilibrium isotherms, kinetics, and thermodynamics of the adsorption of 2,4-dichlorophenoxyacetic acid to a chitosan-based hydrogel and chitosan/magnetite-based composite hydrogel containing 1.0% (w/w) magnetite. The hydrogel synthesis and adsorption processes were confirmed by Fourier transform-infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Adsorption was affected by contact time, solution pH, initial 2,4-D concentration, and solution temperature. The maximum 2,4-D adsorption capacities of the chitosan-based hydrogel and chitosan/magnetite-based composite hydrogel were 75.29 and 45.33 mg of pollutant per g of dried hydrogel, respectively, determined by the Sips isotherm model. The calculation of Gibbs free energy, enthalpy, and entropy revealed the occurrence of spontaneous, endothermic, disordered processes. The adsorption mechanism takes place by monolayer formation and multisite intra/intermolecular interactions, according to the nonlinear Sips isotherm model. In conclusion, the adsorption of 2,4-D to the hydrogels takes place by diffusion processes, intra/intermolecular interactions, and macromolecular relaxation of the polymer network. Desorption processes confirmed the adsorption mechanism. The hydrogels synthesized in this work are efficient solid matrices for the removal of 2,4-dichlorophenoxyacetic acid and chemical oxygen demand from polluted water and wastewater.

A novel and facile green synthesis method to prepare LDH/MOF nanocomposite for removal of Cd(II) and Pb(II)

To date, many nanoadsorbents have been developed and used to eliminate heavy metal contamination, however, one of the challenges ahead is the preparation of adsorbents from processes in which toxic organic solvents are used in the least possible amount. Herein, we have developed a new carboxylic acid-functionalized layered double hydroxide/metal–organic framework nanocomposite (LDH/MOF NC) using a simple, effective, and green in situ method. UiO-66-(Zr)-(COOH)2 MOF nanocrystals were grown uniformly over the whole surface of COOH-functionalized Ni50Co50-LDH ultrathin nanosheets in a green water system under a normal solvothermal condition at 100 °C. The synthesized LDH/MOF NC was used as a potential adsorbent for removal of toxic Cd(II) and Pb(II) from water and the influence of important factors on the adsorption process was monitored. Various non-linear isotherm and kinetic models were used to find plausible mechanisms involved in the adsorption, and it was found that the Langmuir and pseudo-first-order models show the best agreement with isotherm and kinetic data, respectively. The calculated maximum adsorption capacities of Cd(II) and Pb(II) by the LDH/MOF NC were found to be 415.3 and 301.4 mg g−1, respectively, based on the Langmuir model (pH = 5.0, adsorbent dose = 0.02 g, solution volume = 20 mL, contact time = 120 min, temperature = 25 ℃, shaking speed 200 rpm).

Use of Aluminosilicate Residue from Insulators of High Voltage Transformers for the Adsorption of Basic Dyes

In this study, an aluminosilicate residue from insulators of high voltage transformers was used for the adsorption of basic dyes. The absorbent was characterized by X-ray fluorescence analysis, X-ray diffraction analysis, scanning electron microscopy, multimolecular adsorption theory (Branauer-Emmet-Teller (BET)) and determination of the point of zero charge (pHPZC). The effect of solution pH and adsorbent mass, the kinetic and thermodynamic behavior at different temperatures and the application of non-linear isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushevich were investigated. The pHPZC value for the aluminosilicate was 3.7. The best conditions for adsorption of methylene blue and crystal violet dyes were pH 8.0 and adsorbent mass of 1100 mg in 25 mL. The best fit for the experimental data was obtained applying the pseudo-second-order kinetic model, with an equilibrium time of 480 to 720 min, and the activation energy suggests a physical adsorption mechanism. Isothermal parameters suggest a heterogeneous, favorable and predominantly physical surface adsorption. The thermodynamic studies indicated that the adsorption process is not spontaneous and is exothermic and the Gibbs energy values (ΔGº) suggest physisorption.

Experimental and theoretical studies of Rhodamine B direct dye sorption onto clay-cellulose composite

Dyes are one of the main water pollutants and many biological and environmental problems are associated with them. Rhodamine B (RhB) is one of the most commonly used dye in the textile, printing, paints, and paper industry. The present work reports the sorptive removal of Rhodamine B direct dye from wastewater onto developed cellulose and clay composites. Sorbent material cellulose (48 g) was extracted from 80 g of bagasse. Then cellulose and two types of acid-activated clays were used to make efficient sorbent namely, composite I and II. Various characterization techniques were used to study the physiochemical properties of the synthesized composites. Different sorption affecting parameters were optimized such as initial dye concentration, time, temperature, pH, and composite dose for the efficient sorption of RhB onto composites. Equilibrium time was 60 min for composite-I and 80 min for composite-II Non-linear equilibrium isotherm and kinetic models demonstrated the fitness of Pseudo-second order and Redlich-Peterson isotherm. Composite-I and II removed 85.9% and 95.6% of RhB at pH 2 in 120 min, respectively. The sorption efficiency was checked, and sorbents were applied to real textile effluent which showed promising removal efficiency of over 90%. To confirm the experimental results, computational optimization and vibrational calculations were carried out using the Gaussian 09 program package with 3–21 G, 6–311 G, and 6–311+G basic sets. Geometric parameters showed the planar geometry. In the case of FTIR spectra, fundamental ring vibrations were observed with C-H and C-C. This study suggests that the developed composites have exceptional sorption ability to remove the dye contents from aqueous media.

Rapid adsorption of arsenate from water on a novel hybrid of zirconia oxide anchored rGO functionalised carbon foam

In this investigation, the hybrid of ZrO2 decorated rGO functionalised carbon foam (ZRCF) as template has been introduced for removing arsenic (V) (As(V)) contamination from the water and easily separated out from water after post decontamination without any separation techniques. An excellent arsenic (As(V)) removal efficiency of 45.4μgg−1 in 60 min has been revealed by prepared ZRCF treated at 300 °C in air. Further probing the adsorption mechanism, both linear and nonlinear kinetics and isotherm models have been employed on the experimental data. It is revealed that the fitted linear kinetics data better explains the PSO kinetics and linear adsorption isotherm describes the best fitting of equilibrium data in Langmuir isotherm based on the regression coefficient (0.98) and χ2 (7.40) value. The present investigation is evaluated the adsorption mechanism between adsorbate and adsorbent such as electrostatic attraction, HSAB reaction and bi-dentate ligand formation.

Dichromate and arsenate anion removal by PEI microgel, cryogel, and bulkgel

Among the various metal ions, chromate (Cr(VI)) and arsenate (As(V)) are the two most hazardous toxic ion species and are found in nature in the form of dichromate and arsenate anions. In this investigation, polyethyleneimine (PEI)-based hydrogels were prepared with microgel, cryogel, and bulkgel morphologies employing glycerol diglycidyl ether as a crosslinker. The prepared PEI-based hydrogels were used to remove dichromate and arsenate anions from aqueous media. PEI microgel, cryogel, and bulkgels weighing 50 mg of each adsorbed 84.7 ± 0.8, 76.5 ± 5.2, and 108.9 ± 2.4 mg.g−1 of dichromate anions and 15.9 ± 0.7, 45.4 ± 1.9, and 79.2 ± 11.6 mg.g−1 of arsenate anions in 30, 120, and 240 min, respectively. The dichromate and arsenate anions adsorption of PEI-based hydrogels were found to fit to the pseudo-second-order kinetic, and nonlinear Langmuir isotherm models, respectively with higher R2 values. The highest distribution coefficient (Kd) value of PEI-based hydrogels for dichromate adsorption was obtained on the cryogel forms of PEI as 1.89 ± 0.05. Likewise, the highest Kd value for the arsenate adsorption was calculated on PEI-based bulkgels as 0.46 ± 0.01. The thermodynamic parameters of PEI based hydrogels in the adsorption of dichromate and arsenate anions e.g., ΔG (all negative (except for the arsenate adsorption by PEI microgels), and ΔH that is around 2−10 kJ.mol−1, and ΔS what is around 0.01−0.02 kJ.mol−1. K−1 were calculated. The reusability studies showed that PEI-based hydrogels can be used for at least 5 consecutive adsorption-desorption cycles with almost 70 % anion removal efficiency after the fifth cycle.

Projection algorithm-based nonlinear observation of internal states in fuel delivery systems with gas diffusion

In this paper, a nonlinear observer design to estimate different gas species profiles and partial pressures in a fuel delivery system (FDS) with gas permeation is presented. Precise knowledge of critical internal states is of great importance to ensure reliable and efficient operation for FDS. First, a nonlinear isothermal dynamic model including fuel supply, hydrogen consumption, mixture recirculation and exhaust is formulated. Then a nonlinear observer based on projection algorithm is proposed, giving detailed information on internal conditions of FDS online. Without calculation of inverse matrix, the stack output voltage is treated as the only measurable observer input. The voltage estimation error is obtained from the difference between the prediction and the actual measurement, and nonlinear error injection matrix and projection term are employed as correction inputs. Finally, the proposed dynamic state observer is validated and compared with second order sliding mode (SOSM) observer on RT-LAB platform, the results indicate that the observer shows better real-time estimation performance and robustness. Furthermore, the observer demonstrates good robustness in terms of hydrogen partial pressures observation, but less robustness in nitrogen partial pressures estimation. Moreover, the sequence of key system parameters effecting the estimations are analyzed deeply and some conclusions are extracted.

Design and Synthesis of a Dual-Purpose Superadsorbent Containing a High Density of Chelating Motifs for the Fast Mitigation of Methylene Blue and Pb(II).

Maleic acid underwent alternate copolymerization with diallylaminomethylphosphonic acid·HCl [(CH2=CHCH2)2NH+CH2PO3H2 Cl–] and a cross-linker to give a new pH-responsive resin. Methylene blue (MB) removal from its 3000 ppm solution by the resin at pH 7 followed second-order kinetics with an Ea of 34.8 kJ mol–1. MB removal was achieved very fast (10 min), attaining over 98.5% at 328 K. The qe obtained using MB concentrations in the range 100–8000 ppm fitted the Langmuir nonlinear isotherm model to give ΔGo, ΔHo, and ΔSo values of ≈ −21 kJ, 36.5 kJ mol–1, and 185 J mol–1 K–1, respectively. The resin is a superadsorbent with a qmax value of 2445 mg g–1. The adsorbent also removed 97% Pb(II) within 5 min from its 10 000 ppb solution. The resin reduced the Pb(II) concentration from 200 to 3.8 ppb. The resin also demonstrated its ability to remove contaminants from industrial wastewater, reducing priority metal contaminants to ppb and sub-ppb levels. The resin can be recycled with stable efficiency. The outstanding performance places the resin in a top position in a list of recently reported sorbents.

Comparative analysis of linear and nonlinear equilibrium models for the removal of metronidazole by tea waste activated carbon.

Tea waste was carbonized at 400 °C for 45 min and modified with potassium hydroxide (KOH), to enhance the active sites for the adsorption of antibiotics. The developed tea waste activated carbon (TWAC) was used as a novel eco-friendly and cost-effective adsorbent for metronidazole (MZN) removal from aqueous solution. The textural and surface properties of the adsorbent were determined using Brunauer-Emmett-Teller (BET) and FT-Raman analysis. The BET surface was found to have increased from 24.670 to 349.585 after carbonization and KOH modification. The batch experimental parameters were optimized and equilibrium time was found to be 75 min. Linear and non-linear models were carried out on the adsorption isotherm and kinetics to determine the best fit for the adsorption data. The adsorption equilibrium data were well fitted by the Freundlich isotherm and pseudo-second order models, with higher regression correlation (R2) and smaller chi-square (χ2), as predicted by the non-linear model. The thermodynamic results revealed the adsorption of MZN as spontaneous, physical, and consistently exothermic in character. The activation energy value of 7.610 kJ/mol further revealed that the adsorption process is dominated majorly by physical adsorption. The removal of MZN onto TWAC was best described by the non-linear adsorption isotherm and kinetics model.

Optimum isotherm by linear and nonlinear regression methods for lead (II) ions adsorption from aqueous solutions using synthesized coconut shell–activated carbon (SCSAC)

Batch experiment was carried out to determine the optimum isotherm suitable to model the adsorption of Pb(II) ions onto synthesized coconut shell–activated carbon (SCSAC). In order to estimate the equilibrium parameters, the equilibrium adsorption data were analyzed using the following two-parameter isotherms: Langmuir, Freundlich, Temkin and Harkins–Jura by applying linear and nonlinear regression methods. In addition, seven linearized isotherm models (including four linearized Langmuir models) and four nonlinear isotherm models were discussed in this study. The specific surface areas of both nonsynthesized CSAC and synthesized SCSAC-activated carbon were estimated by Sears Method to be 650 m2g−1 and 768 m2g−1, respectively. Likewise other properties like bulk density, particle density, porosity, ash content, Scanning Electron Micrographs (SEM) analysis and Fourier Transform Infrared (FTIR) spectroscopy were also estimated. The error functions which includes the Sum of the Squares of the Errors (SSE), root mean square error (RMSE), Average relative error (ARE), Chi-square (X2), Marquardt’s Percent Standard Deviation (MPSD) and the correlation coefficient (R2) between the calculated and experimental data were also used to compare the suitability of different linearized and nonlinearized model parameters. In conclusion, Freundlich nonlinear isotherm was found to be in better agreement with optimum parameters having generated the maximum adsorption capacity Kf (110.10 Lmg−1), highest coefficient of determination R2 (0.9847) and lowest error functions. Hence, nonlinear isotherms of Freundlich and Harkin–Jura exibited greater performance than linear counterparts in the following order: Freundlich (nonlinear) > Harkin–Jura (nonlinear) > Freundlich (linear) > Harkins–Jura (linear) > Temkin (linear) > Temkin (nonlinear) isotherm models. This shows that transformation of nonlinear isotherm equations to linear forms implicitly alter their error structure.

Synthesis of magnetic nickel ferrites nanocomposites: An advanced remediation of electroplating wastewater

Nickel ferrite nanocomposites (NFNCs) were prepared and utilized to remove hexavalent chromium from the effluent of the electroplating industry. The nickel ferrite nanoparticles (NFNPs) were synthesized by the sol-gel auto combustion process, and they were doped ultrasonically onto the surface-modified multi-walled carbon nanotubes (SM-MWCNTs). Characterization results confirmed that the NFNPs with a cubic spinel structure were successfully impregnated onto the SM-MWCNTs. The synthesized NFNCs were tubular structures with an outer diameter in the range of 30–40 nm and had high crystal defect. The NFNCs with the surface area of 210.5 m2 g−1 offer high magnetic separability due to their paramagnetic behavior. Non-linear kinetic, thermodynamic, and isotherm models were used for interpretations, and high Cr(VI) uptake of 129.83 mg/g was obtained at 40 °C. The Cr(VI) uptake by NFNCs was dominated by electrostatic attractions at a low pH and ion exchange mechanism at a higher pH. Lastly, high efficient recyclability of the NFNCs and applicability in removing other heavy metals from electroplating effluent suggested them to be a promising material in wastewater treatment.

Graphene-based nanomaterials for the removal of organic pollutants: Insights into linear versus nonlinear mathematical models

The adsorption–desorption behavior of methylene blue, acid orange 7, bisphenol A, and phenol on the synthesized graphene-based nanomaterials were studied. For this purpose, adsorption experiments were conducted in a batch setup and different parameters such as contact time, pH, adsorbent dose concentration, and initial micropollutant concentration were considered. In addition, linear and nonlinear kinetic and isotherm models were evaluated. The nonlinear pseudo-second-order models (R2 > 0.98), Elovich kinetic models (R2 > 0.94), and Langmuir isotherm models (R2 > 0.98) best fitted the experimental data. Because of the high specific surface area and the type of oxygen functional groups, mechanochemically synthesized graphite oxide exhibited high adsorption capacities for methylene blue, acid orange 7, bisphenol A, and phenol, with a maximum uptake of 288, 232, 110, and 68 mg g−1, respectively. Furthermore, the total costs of applying the mechanochemically synthesized graphite oxide were estimated in the adsorption process, revealing that these nanomaterials offer better uptake values than porous carbon.