Redlich-Peterson Isotherm Research Articles

Biopolymeric Ni3S4/Ag2S/TiO2/Calcium Alginate Aerogel for the Decontamination of Pharmaceutical Drug and Microbial Pollutants from Wastewater.

The ubiquitous presence of pharmaceutical drugs and microbes in the water is leading to the development of drug resistant microbes. Therefore, efficient materials that can remove or inactivate the drug and microbe contaminants are required. In this work, nickel sulfide/calcium alginate (Ni3S4/CA), silver sulfide/calcium alginate (Ag2S/CA), modified titanium dioxide/calcium alginate (TiO2/CA), and Ni3S4/Ag2S/TiO2/calcium alginate (Ni3S4/Ag2S/TiO2/CA) aerogels have been synthesized for the removal of the oxytetracycline (OTC) drug and microbial contaminants from real beverage industry wastewater. The results revealed that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient for OTC adsorption and inactivation of microbes compared to Ni3S4/CA, Ag2S/CA and TiO2/CA aerogels. The OTC adsorption depends greatly on the solution pH, and optimum OTC removal was observed at pH 6 in its zwitterionic (OTC±) form. The formation of H-bonding and n-π electron donor-acceptors is possible to a considerable extent due to the presence of the double bond benzene ring, oxygen and nitrogen, sulfur-containing functional groups on the OTC molecules, and the Ni3S4/Ag2S/TiO2/CA aerogel. Based on the statistical analysis, root-mean-square deviation (RMSD), chi square (χ2) values, and higher correlation coefficient (R2) values, the Redlich–Peterson isotherm model and Elovich kinetic model are most suited to modelling the OTC adsorption onto Ni3S4/Ag2S/TiO2/CA. The prepared aerogels’ excellent antimicrobial activity is observed in the dark and with solar light irradiation. The zone of inhibition analysis revealed that the antimicrobial activity of the aerogels is in the following order: Ni3S4/Ag2S/TiO2/CA > TiO2/CA > Ag2S/CA > Ni3S4/CA, respectively. Moreover, the antimicrobial results demonstrated that reactive oxygen species, electrons, and active radical species are responsible for growth inhibition and killing of the microbes. These results indicated that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient in decontaminating pollutants from wastewater.

One-Pot synthesis of MWCNTs/Fe-MOFs nanocomposites for enhanced adsorption of As(V) in aqueous solution

Arsenic is a toxic carcinogen, and arsenic pollution in groundwater is one of the most serious environmental problems in the world. Thus, it is an urgent problem to efficient removal of arsenic from groundwater. In this work, a novel MWCNTs/MIL-53(Fe) nanocomposite was successfully synthesized to improve the water stability of MIL-53(Fe) by incorporation of carboxylated multi-walled carbon nanotubes (MWCNTs) using a one-pot hydrothermal method, and was then used to efficiently adsorb As(V) ions from groundwater. Adsorption experimental results demonstrated an ultrafast adsorption rate of As(V) on the MWCNTs/MIL-53(Fe) nanocomposites in solution pH values of 3 to 10, and the adsorption equilibrium could be reached in circa 20 min with an adsorption capacity of 27.24 mg·g−1 in a low As(V) concentration of 10 mg·L−1. The adsorption kinetics of As(V) on the MWCNTs/MIL-53(Fe) was found in line with the pseudo-second-order (PSO) kinetic model, and was simultaneously controlled by both internal diffusion and liquid film diffusion. The adsorption isotherm data conformed to the Redlich-Peterson isotherm model, indicating both physical and chemical adsorption occurred at heterogeneous interfaces. Moreover, the postulated adsorption mechanism of As(V) on MWCNTs/MIL-53(Fe) nanocomposites was ascribed to hydrogen-bond interaction, electrostatic attraction and chemical complexation. Therefore, the as-prepared MWCNTs/MIL-53(Fe) nanocomposites not only exhibit superior water stability and outstanding adsorption performance in removing arsenic-contaminated groundwater, but also offer a novel insight for rational preparation of water-stable MOF-based composites.

Antibacterial, Antifungal, and Antibiotic Adsorption Properties of Graphene-Modified Nonwoven Materials for Application in Wastewater Treatment Plants

The utilization of adsorptive nonwovens as a pretreatment unit may lead to novel, cost-efficient wastewater treatment technologies with remarkable properties for environmental protection, such as efficient adsorption of antibiotics. This paper uses graphene-modified nonwoven (GMN) to examine (i) how the adsorption of tetracycline (TCY)—especially since this antibiotic is frequently detected in the environment—takes place on an environmentally relevant concentration scale, and (ii) what factors influence the antibacterial and antifungal properties profile of this material class. This study demonstrates that combining graphene particles with commercial textile auxiliaries clearly enhances the antibacterial and antifungal properties of the modified nonwoven materials. The enzyme-linked immunosorbent assay (ELISA) was used to detect the TCY residues at ng/mL scale. The adsorption results follow Henry and Redlich–Peterson isotherms and emphasize the adsorption process at low concentration levels of TCY. Therefore, the appropriately designed GMNs have a great potential application for wastewater treatment in sewage plants. Statistical analysis (skewness and kurtosis) of nonwovens and modified nonwovens morphology allowed us to determine the parameters influencing the growth of fungi in such structures. GMN structures are capable of adsorbing antibiotics; a two-fold reduction of TCY was obtained in the studies.

Adsorption and recovery of phosphate from aqueous solution by katoite: Performance and mechanism

Phosphate removal and recovery from wastewater is an effective approach to alleviate eutrophication and overcome the future scarcity of phosphorus. Katoite, a kind of calcium aluminate hydrate, was synthesized and examined as a novel adsorbent to remove phosphate from aqueous solution and recover phosphate as potential slow-release fertilizer. Batch experiments showed that the maximum phosphate adsorption capacity of katoite reached 111.51 mg P/g. Also, a high equilibrium adsorption capacity of 80.14 mg P/g was obtained at the initial concentration of 10 mg P/L. The adsorption could be well described by the Elovich kinetic model and Redlich-Peterson isotherm model. Thermodynamic study suggested that the adsorption was an endothermic process and occurred favorably and spontaneously. Moreover, the adsorption was almost independent of the ionic strength and showed high selectivity for phosphate in solutions containing common coexisting anions. The phosphate adsorption on katoite could be attributed to inner-sphere complexation and surface precipitation, which were further suggested by the SEM-EDS, FTIR and XPS analysis. Desorption experiments results indicated the possible plant availability and successive release property of the phosphate adsorbed on the surface of katoite. Overall, the study suggested that katoite is a promising candidate for phosphate adsorption and subsequent recovery as a slow-release phosphorus fertilizer.

Sorption studies of Pb(II) onto montmorillonite clay

In this research, the lead (Pb(II)) removal rate of montmorillonite (Mt) was studied in aqueous solution. The adsorption conditions (contact time, pH, and temperature) were adjusted to study the effect of those factors on the removal rate of Pb(II) adsorption by Mt. The results indicated that the effect of temperature on the Pb(II) removal rate of Mt was not significant. The Pb(II) removal rate was found to be pH-dependent, improving with increasing pH in the range of 3 to 7. The equilibrium time of adsorption was attained after around 1 hour. The adsorption kinetics were analyzed by fitting to three models (pseudo-first-order (PFO) kinetic model, pseudo-second-order (PSO) kinetic model and intraparticle diffusion model. In comparison, R2 value (0.9952) of PSO kinetic model is better than PFO (0.9718), supposing that the adsorption process of Pb(II) onto Mt was chemisorption. The intraparticle diffusion model fitting showed that the Pb(II) adsorption process by Mt was controlled by three steps. Langmuir, Freundlich, Redlich-Peterson and Sips isotherm models were used to describe the adsorption mechanism of Pb(II) adsorbed onto Mt. The experiment results showed the adsorption isotherms are a perfect fit to the Sips model, indicating both homogeneous monolayer adsorption and heterogeneous multilayer adsorption were occurred in the Pb(II) adsorption process by Mt, and the adsorption was mainly controlled by heterogeneous multilayer adsorption.

High-efficiency removal of hexavalent chromium from contaminated water using nitrogen-doped activated carbon: kinetics and isotherm study

Hexavalent chromium (Cr6+) is a carcinogenic pollutant found in different wastewater streams. The current study investigates the potential removal of Cr6+ from aqueous solutions by nitrogen-doped coconut granulated activated carbon (N-GAC). The raw GAC was chemically and thermally treated with urea (1:1 ratio) in an ethanol medium and calcined under nitrogen atmosphere at temperatures 400 °C and 600 °C. The optimized sample (N-GAC 400 °C) possessed a remarkable surface area (474.62 m2/g) while the chemical composition analysis revealed successful doping of nitrogen with no significant changes on the mesoporous morphology of the raw GAC. The adsorption studies revealed that Cr6+ adsorption capacity was higher for N-GAC 400 °C. The removal efficiency was significantly decreased with increasing the initial solution pH (optimum pH 2.2). The temperature has no significant effect on the adsorption capacity. The equilibrium experimental results were best fitted with Sips and Redlich-Peterson isotherm models with R2 ≥ 0.987 and a maximum adsorption capacity of 15.15 mg/g. The kinetic data agreed with the pseudo 2nd order model (R2 > 0.997). The isotherm and kinetic studies revealed that physisorption and chemisorption processes are involved in the removal process. The adsorption mechanism was mainly controlled by electrostatic interactions, ion exchange and reduction of Cr6+ to trivalent chromium. Accordingly, the N-GAC can be considered a promising material for the adsorptive removal of heavy metals from water.

An experimental and theoretical investigation of cationic azine dye adsorption on natural sepiolite in single and multi-component systems

Adsorption kinetics and equilibria of the azine dyes onto natural sepiolite are investigated using Methylene Blue, Thionin and Safranin O. Experimental equilibrium results for three azine dyes are well predicted by the Freundlich, Langmuir and Redlich-Peterson isotherm models. The model parameters obtained for single solute systems at 298 K are used for the calculation of adsorption isotherms in binary and ternary dye solutions using multi-component isotherm models. Modified extended Langmuir model is satisfactorily fit to the adsorption in binary and ternary solutions. The diffuse-reflectance-infrared-Fourier-transforms technique was used to characterize the bare and dye loaded sepiolite surface. The kinetic results for single, binary and ternary dye systems have been analyzed according to the pseudo-first-order and Elovich models. Vermeulen approximation was also applied to the data for prediction of the diffusion behavior of the dyes. The molecular chemical reactivity of the dye molecules estimated based on the Density Functional Theory was well correlated to the sorption results. The energy gap between the highest-occupied molecular-orbital and lowest-unoccupied-molecular-orbital energies, chemical potential, chemical hardness, softness, global electrophilicity and global nucleophilicity values prove that Methylene Blue is more reactive than Thionine and Safranine O cationic dyes.

Functionalized UiO-66-NH2 by trimellitic acid for highly selective adsorption of basic blue 3 from aqueous solutions.

A novel metal-organic framework (MOF) UiO-66-TLA (UiO-66-Trimellitic Acid) was synthesized by one-pot method with trimellitic acid as modifier, which can effectively remove the basic dye Basic Blue 3 (BB3) in wastewater. Modification with carboxyl groups facilitates the adsorption of the cationic dye Basic Blue 3. The adsorption of BB3 by the modified UiO-66-TLA was significantly greater than that of its parent MOF. The adsorption capacity of the modified UiO-66-TLA for BB3 (234.23 mg g−1) was 93.2% higher than that of the original UiO-66-NH2 (121.24 mg g−1), this is closely related to the electrostatic interaction of -COOH in trimellitic acid. UiO-66-TLA was successfully synthesized as indicated by various characterization results. The adsorption kinetics conformed to the pseudo-second-order model, and the adsorption isotherm conformed to the Redlich-Peterson isotherm. This indicates that BB3 is a multi-parameter model of monolayer/multilayer arrangement on the adsorbent surface, and its rate-controlling step is chemisorption. The adsorption process was non-spontaneous and belonged to an endothermic reaction, in addition, it has great adsorption stability and regeneration The interaction of the modified UiO-66-TLA with BB3 was mainly affected by mechanisms, such as electrostatic interaction, π–π stacking as well as the abundant functional groups on UiO-66-TLA surface. These results demonstrate that UiO-66-TLA is an efficient, regenerable, water-stable material for the removal of BB3 in solution, with practical implications, suggesting its potential as a dye adsorbent.

Fabrication of graphene oxide/inulin impregnated with ZnO nanoparticles for efficient removal of enrofloxacin from water: Taguchi-optimized experimental analysis.

A novel nano-adsorbent zinc oxide impregnated graphene oxide/inulin (ZGI) was prepared for the investigation of the removal efficiency of enrofloxacin. Characterization of the nano-adsorbent was accomplished through Fourier transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDS, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The average crystallite size of nanomaterial (ZGI) calculated from XRD data was 14.82nm. The adsorption of enrofloxacin onto ZGI was performed in batch mode. The variables of adsorption process such as adsorbent dose, pH, contact time and initial concentration of enrofloxacin were optimized by Taguchi method to achieve the maximum removal efficiency. The optimum values of variables were: adsorbent dose=25mg, pH=7, contact time=60min and initial concentration=50mg/L. The maximum adsorption capacity and removal efficiency of the material for enrofloxacin were 317.83mg/g and 98.60%, respectively at 303K. Redlich-Peterson isotherm model was the best fitted among the various isotherm models based on highest R2 values (0.9978-0.9981) and lowest χ2 (3.43 ×10-4-2.00×10-3). Kinetic data followed pseudo-second order model (R2≥0.9974) more accurately as compared to pseudo-first order model (R2≤0.9772). The adsorption mechanism was illustrated on the basis of XPS and Raman studies. Reusability investigation showed that the nano-adsorbent ZGI could be used up to 5 adsorption-desorption cycles with greater than 90% removal efficiency.

Study of the Ciprofloxacin Adsorption of Activated Carbon Prepared from Mangosteen Peel

In this study, activated carbon derived from mangosteen peel (abbreviated as ACMP) was successfully fabricated. This as-prepared ACMP possessed graphite and had a porous structure with a specific surface area of 419.8554 m2/g. Investigations of the influencing factors on the ciprofloxacin (CIP) adsorption capability of the ACMP based on the static adsorption method showed that: adsorption equilibrium can be achieved in 60 min, the optimal pH for CIP adsorption was a pH of 6, and the optimal ratio between the material mass and solution volume was 3 g/L. The CIP adsorption process of the ACMP follows the Langmuir, Freundlich, Tempkin, Elovich, and Redlich–Peterson isotherm adsorption models. The maximum adsorption capacity calculated according to the Langmuir isothermal adsorption model for the CIP of the ACMP was (qmax = 29.76 mg/g). The CIP adsorption process of the ACMP followed the apparent quadratic kinetic equation, as well as spontaneous, endothermic, physical, and chemical adsorption. The adsorption rate was governed by membrane diffusion.

Adsorption of rhodamine-B by polypyrrole Sn (IV) tungstophosphate nanocomposite cation exchanger: Kinetic-cum-thermodynamic investigations

ABSTRACT Synthesis of an organic-inorganic polypyrrole Sn(IV) tungstophosphate (Ppy-SWP) nanocomposite cation exchanger is used to study the adsorption of Rhodamine B (RH-B) utilizing batch adsorption by in-situ chemical oxidative polymerization of pyrrole (Ppy) with Sn(IV) tungstophosphate (SWP). FT-IR, XRD, SEM, TEM, and TGA were used to examine the synthesized material’s structural, morphological, and chemical features, revealing the successful Ppy-SWP nanocomposite synthesis. The impact of several parameters, such as pH, adsorbent amount, contact time, and starting dye concentration on RH-B adsorption onto Ppy-SWP, was investigated. The ion exchange capacity (IEC) and maximum level of RH-B dye adsorbed onto Ppy-SWP were reported to be 2.7 meq/g and 209.13 mg/g respectively. Kinetic (pseudo-first order, pseudo-second order, and intraparticle diffusion) and isotherm (Langmuir, Freundlich, Temkin, and Redlich–Peterson) models were used to pick the ideal match for the adsorption data. The Langmuir and Redlich–Peterson isotherm models fit the adsorption data well, while the pseudo-second order model best describes the kinetics data of RH-B adsorption. According to the computed thermodynamic variables standard-free energy, enthalpy, and entropy, the RH-B adsorption onto the Ppy-SWP is a spontaneous, endothermic, and physical sorption process. Even after seven cycles, regeneration experiments revealed an efficiency of greater than 80%.

Phosphate-functionalized ramie stalk adsorbent for efficient removal of Zn2+ from water: adsorption performance, mechanism, and fixed-bed column treatment of real wastewater.

A highly efficient adsorbent functionalized with phosphate groups made from a local agricultural waste, ramie stalk, was designed for Zn2+ removal from water. SEM, EDS, FTIR, zeta potential, and XPS tests were used to study the morphology and properties of modified ramie stalk (RS-P). The results showed that the phosphate groups were successfully grafted to the surface of the ramie stalk, which has a multilayered and porous structure and can provide large adsorption sites. Adsorption performance and mechanism were investigated in the static and dynamic adsorption experiments. The adsorption kinetics of Zn2+ by RS-P were better fitted by the pseudo-second-order model, indicating chemical adsorption. Adsorption isotherm was better described by Redlich-Peterson isotherm, which suggested heterogeneous and multi-site adsorption, with a maximum adsorption capacity of 0.558mmolg-1. The characterization of adsorbents before and after adsorption indicated that a combined action of electrostatic interaction and ion exchange was the primary mechanism of adsorption. Dynamic adsorption experiments with fixed-bed column displayed excellent water treatment capabilities. RS-P exhibited good reusability in 5 cycles without much deterioration in its adsorption performances. Complex co-existing ions impaired Zn2+ adsorption during real wastewater treatment. This research benefits agricultural waste recycling and provides safe water to ensure economic, social, and environmental sustainability.

Carbide-derived carbon as an extraordinary material for the removal of chromium from an aqueous solution

In the present work, the adsorptive removal of chromium (Cr) from water by carbide-derived carbon (CDC) was investigated. The morphology and structure of the CDC were characterized by using FTIR, SEM, TEM, XRD, and N2 adsorption-desorption measurements. The effect of adsorption parameters including contact time, initial Cr concentration, temperature, initial solution pH, and CDC dosage was examined on the removal of Cr ions. The kinetic analysis revealed that the experimental data on the removal of Cr ions on CDC is well correlated with the pseudo-second order kinetic model (with R2 > 0.999), while the equilibrium data were fitted by the Redlich-Peterson isotherm model (with R2 > 0.992). The Langmuir and Sips models were also in good compliance with the equilibrium data, indicating a monolayer coverage of Cr ions onto the CDC surface with some heterogeneous active adsorption sites. The CDC revealed a notable Langmuir adsorption capacity of 159.1 mg/g for Cr ions at pH 6 and room temperature. The thermodynamic analysis illustrated that the Cr ions elimination by CDC is a feasible adsorption process and endothermic in nature. After five adsorption/desorption cycles, less than 18% reduction in the adsorption capacity was obtained indicating the stability and reusability of the CDC. Moreover, the CDC demonstrated an excellent potential in removing the Cr ions from real brackish water. According to the adsorption data, both physical and chemical adsorption processes occurred, and the adsorption was mainly controlled by electrostatic interactions with a possible reduction of hexavalent Cr to trivalent Cr at acidic conditions.

Construction of hyper-crosslinked ionic polymers with high surface areas for effective CO2 capture and conversion

The design and preparation of ionic liquids functionalized polymer materials is a trending topic in the fields of polymer science for CO2 capture and utilization. In this work, a series of porous hyper-crosslinked ionic polymers (PIPs) with high surface area and abundant catalytic central units have been synthesized by a simple post-crosslinking of ionic liquid monomer and 4,4′-bis(chloromethyl)-1,1′-biphenyl. The prepared PIPs were used for CO2 adsorption, and their adsorption capacity for CO2 exceeded 100 mg g−1 at 273 K and 1.0 bar. Furthermore, the isotherm adsorption data of CO2 were fitted respectively by Langmuir, Freundlich, Redlich-Peterson, and Toth isotherm models to calculate the thermodynamic parameters, including changes in Gibbs free energy (ΔG°), enthalpy (ΔH°), entropy (ΔS°), and isosteric heat of adsorption (ΔHIsosteric). It is concluded that the adsorption process of CO2 on PIP is a spontaneous physical process. These PIP can also be used as heterogeneous catalysts for the cycloaddition of CO2 with epoxides under metal/solvent/cocatalyst-free conditions. The excellent yields (up to 99%) of cyclic carbonates are ascribable to synergistic contributions of abundant microporous and active ionic catalytic centers. This study provides a new idea for developing functionalized ionic polymers that combine capture and conversion of CO2.

Formulation of NZVI-supported lactic acid/PAN membrane with glutathione for enhanced dynamic Cr(VI) removal

The current technologies for production of nanoparticle-membrane are apt to involve complicated multi-step process and/or toxic chemicals and other defects. This study provides a green and clean cryogel manufacture method for fabrication of hydrophilicity Polyacrylonitrile (PAN) membrane with highly porous structure for supporting nano zero-valent iron (NZVI) via a surface modification by employing biodegradable lactic acid. Non-toxic natural compound, glutathione (GSH) was adopted not only as modifiers but also as chelators to promote the capture capacity of hexavalent chromium (Cr(VI)). The specific surface area of the prepared composite (GLPN, 193.16 m2/g) was larger than the previously studied NZVI-membrane (PPN, 131.61 m2/g), and NZVI was distributed uniformly and not agglomerated on the membrane. Compared with NZVI, the efficiency of GLPN removed Cr(VI) has increased by 39.80%. At low pH and Cr(VI) initial concentration, GLPN can completely remove Cr(VI) when the GSH concentration is increased to 50 mM, and the removal efficiency can still reach 86.96% after 6 regenerations. Visual MINTEQ model and experimental results show that the mechanism of GLPN removing Cr(VI) includes the synergy of electrostatic adsorption, chelation, reduction and co-precipitation. The process conforms to two-parameter nonlinear dynamics and Redlich-Peterson isotherm model. This novel strategy shows that GLPN has excellent stability, reducibility and green reproducibility, and can efficiently remove and recycle heavy metal in the natural water matrices or wastewater.

Adsorption of Dyes Using Graphene Oxide-Based Nano-Adsorbent: A Review

Graphene Oxide (GO) based adsorbents have attracted much attention from researchers because there have been many reports that they are effective for removing dyes from aqueous environments. That is because GO has good mechanical, electrical, optical and chemical properties, so graphene and its derivatives, such as graphene oxide, have been used in various applications in the field of environmental management. Modifying GO into nano size is an effort to improve its performance in removing dyes. This review uses a database from Science Direct, Google Scholar and Springer, which was screened using graphene oxide, pigments, adsorption and nano adsorbent. The performance of the nano adsorbent showed quite good results in the removal of dyes. The isotherm model suitable for adsorption varies between Langmuir, Freundlich and Redlich-Peterson isotherms. Pseudo-second-order (PSO) is the best model to explain the adsorption process kinetics. Nano-adsorbent modification can be reused at least five times with a reduced adsorption capacity of 4-8%. Studies related to adsorption with GO-based nano adsorbents show promising results in pollutant removal. Still, aspects such as synthesis method, surface functional groups interaction and dye ions and the stability of synthesis products need to be investigated further.

Bio-adsorption performances of methylene blue (MB) dye on terrestrial and marine natural fibers: Effect of physicochemical properties, kinetic models and thermodynamic parameters

ABSTRACT Biomass residues and algal wastes were used for the first time to produce new efficient adsorbents from lignocellulosic powders from Solanum elaeagnifolium Cavanilles (SE. Cav) and Gelidium elegans (G. elegans), respectively, for the efficient removal of methylene blue (MB) dye in aqueous systems. The physicochemical features and the efficiency of the bio-sorbents were successfully characterized by FTIR, XRD, TGA/DTG, BET, SEM and isoelectric point (pHpzc) tests. The results indicate that both bio-adsorbents have an overall surface acid due to the occurrence of hydroxyl and carboxylic groups, which directly impact the binding of cationic molecules to the surface. SE. Cav showed an ultimate monolayer absorbency of 50.607 mg/g at neutral pH (6.8) and room temperature (24°C). However, under the same conditions, G. elegans exhibited a higher value (76.689 mg/g). The adsorption kinetics indicates that both materials fit the pseudo-second-order (PSO) model as the correlation factors are quite near to unity. The parameters obtained from the equilibrium data showed that the experimental results fit well with the Langmuir, Freundlich, Redlich-Peterson and Sips isotherms for both bio-adsorbents. Moreover, the thermodynamic parameters suggest that the MB adsorption process for the two materials was exothermic and spontaneous.

Magnetic zeolite from fly ash as a cost-effective adsorbent for Cu²⁺, Pb²⁺, Zn²⁺, and Cd²⁺ removal from aqueous media: a comprehensive study

ABSTRACT In this work, we report the synthesis of magnetic zeolite A using fly ash as the main sources of SiO₂ and Al₂O₃, by hydrothermal use in the adsorption of Pb2, Cd2, Zn2⁺ and Cu2. The composite synthesis was successful, and the obtained material was characterised by using different techniques, such as X-ray diffraction (XRD), X-ray fluorescence (XRF), Infrared vibrational spectroscopy (FTIR), Electron Microscopy (SEM), and pH point of zero charge (pHpzc). XRD measurements confirm zeolites A as the main crystalline phases (98.5%), with the presence of a small amount of sodalite (1.5%). In the SEM of magnetic composite, the characteristic morphology for zeolite A was noted, with magnetite nanoparticles dispersed on its surface, resulting in a composite with magnetic properties. In the adsorption study, the magnetic composite showed a fast rate of adsorption, in which the pseudo second order model was the one that best described the experimental data of the metal ions under study. The Redlich-Peterson isotherm model best represented the experimental data of Pb2⁺ and Cd2⁺, while the Langmuir and Sips models fitted Zn2⁺ and Cu2⁺, respectively. Thus, the results showed that the magnetic composite presented high magnetic quality, facilitating its separation from the aqueous medium, as well as being a promising adsorbent in the adsorption of metal ions in aqueous medium.

Synthesis of hollow spherical polyaniline by using poly(styrene‐co‐acrylic acid) sphere as the template for high adsorption of Cr(VI)

AbstractSynthesis of hollow spherical polyaniline (HSPANI) with the merits of facile strategy, low cost, low safety risk and high adsorption capacity of Cr(VI) is always a big challenge. In this manuscript, we proposed a facile way to preparation of HSPANI by using the poly(styrene‐co‐acrylic acid) sphere as template. The results indicated that HSPANI was emeraldine comprised of lots of basically uniform hollow spheres, and its average pore diameter was about 300 nm. HSPANI displayed high adsorption capacity of Cr(VI), and its value arrived at 601.3, 347.8, 235 mg g−1 at pH = 1, 2, and 3, respectively, which were high than many other adsorbents. The endothermic, spontaneous and chemical adsorption process was responsible for this adsorption. The Cr(VI) adsorption capacity was significant relied on its pH, contact time, Cr(VI) concentration and adsorption temperature. The adsorption behavior was well agreed with pseudo second‐order equation and Redlich–Peterson isotherm models. HSPANI exhibited remarkable selectivity for adsorption of Cr(VI) even if the K+, Cu2+, NO3− and SO42− were coexisted. HSPANI also displayed excellent regeneration performance. Therefore, this work not only provided a facile way to synthesis of hollow spherical polyaniline, but also supplied a potential adsorbent for adsorption of Cr(VI) from the industrial wastewater.

Accurate data prediction by fuzzy inference model for adsorption of hazardous azo dyes by novel algal doped magnetic chitosan bionanocomposite

A bionanocomposite comprising of magnetic chitosan doped with algae isolated from native habitat was fabricated and utilized as an efficient adsorbent for the removal of hazardous azo dyes, namely, Direct Red 31 (DR31) and Direct Red 28 (DR28). The algal doped magnetic chitosan (Alg@mCS) was comprehensively characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction analysis (XRD), and Brunauer-Emmett-Teller (BET). On the sorption of dyes, the influence of various process variables such as pH, adsorbent dosage, contact time, temperature, and initial dyes concentration were addressed. The adsorbent demonstrated maximal removal of DR31 and DR28 at pH 5 and 3, respectively. The maximum adsorption capacity of DR31 and DR28 was observed at Alg@mCS dose of 0.6 g L−1 and 7 g L−1 in 10 and 20 min, respectively. The Redlich Peterson isotherm model was shown to be appropriate for dye adsorption, indicating monolayer coverage of the dyes on the adsorbent surface (R2 > 0.99). The adsorption process followed pseudo-second-order kinetics (R2 > 0.99). Based on 320 experimental datasets from batch studies and interpolated data, adaptive neuro-fuzzy inference system (ANFIS) models were utilized to estimate dye elimination (percent). A number of parameters were calculated to validate the model's applicability. The Alg@mCS was proven to be a useful adsorbent for eliminating toxic and harmful azo dyes from aqueous solutions.