Reuse of a waste adsorbent poly(AAc/AM/SH)‐Cu superabsorbent hydrogel,for the potential phosphate ion removal from waste water: Matrix effects,adsorption kinetics,and thermodynamic studies

The most commonly applied methods for the treatment of used adsorbents is to recover them in acid/alkaline medium or direct enflame them. This work dealt with a new potential and economic method to utilize a waste adsorbent. Poly(AAc/AM/SH) superabsorbent hydrogels have proved to be a good adsorbent for Cu²⁺ ions and after adsorption the hydrogels were recovered in acid medium. In this report, the Cu²⁺ ion adsorbed hydrogel has not undergone any regeneration process and applied directly to phosphate ion adsorption. The Cu²⁺ ions‐loaded poly(AAc/AM/SH) hydrogels, were stable within a wide pH range and suitable for phosphate ion adsorption. The factors affecting the phosphate adsorption, such as pH, ionic strength, contact time, temperature, initial concentration of the phosphate ion, and coexisting ions were systematically investigated. The phosphate adsorption was highly pH dependent; and the maximum adsorption of 87.62 mg/g was achieved at pH 6.1. The adsorption data fitted the Langmuir adsorption isotherm better than the Freundlich isotherm. The concomitant anions show profounder adverse influence on phosphate ion adsorption of poly(AAc/AM/SH)‐Cu hydrogel and the effect follows the order citrate > sulfate > bicarbonate > chloride > nitrate. The thermodynamic parameters including ΔH°, ΔG°, and ΔS° for the adsorption processes of phosphate ions on the gel were also evaluated, and the negative ΔG° and ΔH° confirmed that the adsorption process was spontaneous and exothermic. The adsorption kinetic results suggest that the adsorption process was well described by the pseudo second‐order kinetic model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dynamics and Thermodynamics Studies on the Lead and Cadmium Removal from Aqueous Solutions by Padina sp. Algae: Studies in Single and Binary Metal Systems

Raw and modified biomasses prepared from Padina sp. algae have been used as sorbent for the removal of lead and cadmium from single and binary aqueous solutions. The effects of chemical pretreatment, exposure time, initial solution pH, initial metal concentration, and temperature on the metal uptake by the algae were investigated. It was observed that initial solution pH considerably influenced Pb and Cd uptake. The maximum removal occurred at initial pH of 5.0 for lead and 6.0 for cadmium. Also, alkali modified biomass has been shown to have a high uptake capacity for both lead and cadmium. The kinetic and equilibrium experimental data fitting tested with various models. The pseudo-first-order kinetic model and Langmuir isotherm provided the best correlation of the kinetic and equilibrium experimental data, respectively. The maximum uptake estimated from the Langmuir isotherm was 264 mg g^?1 for lead and 164 mg g^?1 for cadmium ions. Experimental biosorption data in binary system were well described by the extended Langmuir model. Various thermodynamic parameters, such as ΔG°, ΔH°, and ΔS° were calculated.     

Assessment of kinetic and isotherm models for competitive sorption of Cs+ and Sr2+ from binary metal solution onto nanosized zeolite

This study examined the sorption performance of synthesized nanosized zeolite for the elimination of Cs⁺ and Sr²⁺ cations in a binary metal system. The influence of pH, sorbent amount, temperature, and contact time was studied. The relationship between each of these parameters and the removal efficiency was investigated. An analysis of the rate data was performed using both pseudo-first- and second-order reaction models. The ranking of three equilibrium sorption isotherm models used (Redlich–Peterson, Langmuir, and Freundlich) with a variety of numbers of parameters was determined using the corrected Akaike’s information criterion. The results demonstrate that a pseudo-second-order model fits the sorption kinetic data better than a pseudo-first-order model. The isotherm model rank order that best described the data statistically was Redlich–Peterson?>?Langmuir?>?Freundlich for the cesium ions and Langmuir?>?Redlich–Peterson?>?Freundlich for the strontium ions. Our results revealed that the existence of Sr²⁺ caused a significant reduction of Cs⁺ sorption in the binary metal mixture according to a lumped parameter model and vice versa. The results show that the synthesized material’s surface had a relatively stronger affinity for Cs⁺ than for Sr^2+.     

Biosorption of Zinc from Aqueous Solutions by Rice Bran: Kinetics and Equilibrium Studies

Abstract

Rice bran, an agricultural by‐product, was used for the removal of zinc ions from aqueous solution. The work considered the determination of zinc‐biomass equilibrium data in batch system. These studies were carried out in order to determine some operational parameters of zinc sorption such as the time required for the Zinc‐biosorbent equilibrium, the effects of biomass particle size, pH, and temperature. The results showed that pH has an importance effect on zinc biosorption capacity. The biosorbent size also affects the zinc biosorption capacity. The sorption process follows pseudo‐second‐order kinetics. The intraparticle diffusion may be the rate‐controlling step involved in the adsorption zinc ions onto the rice bran up to 30 min. The equilibrium data could be best fitted by the Langmuir sorption isotherm equation over the entire concentration range (40–160 mg/dm³). Thermodynamic parameters, such as ΔG°, ΔH°, ΔS°, have been calculated. The thermodynamics of zinc ion/rice bran system indicate spontaneous and endothermic nature of the process.     

Electrochemical removal of boron from water: Adsorption and thermodynamic studies

The present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm^?2 at pH of 7.0. First‐, second‐order rate equations, Elovich and Intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)₃ were determined and correlated with isotherm equations such as Langmuir, Freundlich and D‐R models. Thermodynamic parameters, such as standard Gibb's free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°), were also evaluated by Van't Hoff equation. The adsorption process follows second‐order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)₃ was found to be spontaneous and endothermic. © 2011 Canadian Society for Chemical Engineering     

Kinetics and Equilibrium Studies for the Removal of Cobalt,Manganese, and Silver in Ethanol using Dowex 50W-x8 Cation Exchange Resin

Organic solvents such as ethanol, find a wide range of applications in fuel, pharmaceutical industries, food industries, and paint formulations, among others. The removal of Ag(I), Co(II), and Mn(II) ions in ethanol by cation exchange resin, Dowex 50W-x8, was investigated. The adsorption characteristics of metal ions onto Dowex 50W-x8 resin were described by Langmuir isotherms. The maximum sorption exchange capacities at 298 K were obtained as 47.4 mg g^?1, 52.6 mg g^?1, and 58.5 mg g^?1 for Ag(I), Co(II), and Mn(II), respectively. The data was also fitted to Temkin and Dubinin-Radushkevich adsorption isotherm models to evaluate other adsorption properties. The ion exchange of silver, cobalt, and manganese on cation exchange resin followed pseudo-second-order kinetics, and the intraparticle diffusion was rate-determining step. The thermodynamic parameters indicated that the sorption of metal ions onto Dowex 50W-x8 resin was spontaneous (negative ΔG°) and endothermic in nature (positive ΔH°) implying that the adsorption capacity increased with increasing temperature. The resin can be regenerated by eluting metal ions with 3.0 mol L^?1 HNO₃ followed by washing it with 10 mL of Millipore water and 10 mL of 2.0 M NaOH, respectively. The proposed method was applied for metal ion removal in real ethanol samples.     

Removal of Sr(II) from Aqueous Solutions by Aminosilane Functionalized MCM-48

In this research, NH₂-MCM-48 adsorbent was synthesized by grafting of aminopropyl on the surface of MCM-48 mesoporous silica material. The synthesized adsorbent was characterized by FT-IR, XRD, thermogravimetric, and surface area techniques. The removal of Sr (II) by the synthesized adsorbent was studied and the effect of initial pH, contact time, cation concentration, and temperature on the Sr²⁺ adsorption was studied and optimized. Under optimized conditions, the removal capacity of 5.95 meq/g was obtained. The experimental data were analyzed using the Langmuir and Freundlich equations. Adsorption data was fitted with the Langmuir isotherm, indicating that the process was monolayer and chemical in nature. The calculated thermodynamic parameters, ΔH°, ΔS°, and ΔG° confirmed that the adsorption process was endothermic and spontaneous. The regeneration of the adsorbent was examined and it was found that 92% of the initial capacity was conserved after five successive regeneration cycles.     

Adsorptive removal of cationic dye from aqueous solutions by ZnO/ZnMn2O4 nanocomposite

The ZnO/ZnMn₂O₄ nanocomposite (ZnMn) was used as adsorbent for the removal of cationic dye Basic Yellow 28 (BY28) from aqueous solutions. The adsorbent was characterized by X-ray diffraction, scanning electron microscope, TEM, Fourier transform infrared ray, BET, particle size distribution and zeta potential measurements. The adsorption parameters, such as temperature, pH and initial dye concentration, were studied. Kinetic adsorption data were analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The Langmuir and Freundlich isotherm models were applied to fit the equilibrium data. The maximum adsorption capacity of BY28 was 48.8 mg g^?1. Various thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, were calculated.     

Vehicular Tire as Potential Adsorbent for the Removal of Polycyclic Aromatic Hydrocarbons

ABSTRACT

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants, entering into various water and wastewater systems through various natural and anthropogenic activities. The aim of the work is to convert vehicular tires, a highly available waste material, into potential adsorbent for the removal of PAHs from aqueous solutions. The BET surface area of the prepared vehicular tire activated carbon is 643.86 m²/g. Removal of PAHs using activated carbons and the effect of various parameters such as contact time, adsorbent dose, temperature, and pH on the adsorption have been evaluated. The data were fitted to Freundlich and Langmuir isotherms and values of various constants were evaluated. In all the cases, Freundlich model was found to be better fitted. The equilibrium time for adsorption of PAHs was 120 min. The values of thermodynamic parameters, such as Gibb's free energy change ΔG°, enthalpy change ΔH°, and entropy change ΔS°, were calculated using adsorption equilibrium constants obtained from Langmuir isotherm. The thermodynamic data for adsorption of PAHs revealed spontaneity and endothermic nature of the adsorption process. The samples were analyzed using a UV–vis spectrophotometer for PAH determination. Mixture of sodium hydroxide and ethanol in different proportions was tried for desorption of PAHs and 50% ethanolic NaOH solution was most effective. The developed activated carbon demonstrates good adsorption and desorption capabilities for PAHs, indicating towards its suitability for use in the treatment processes of various industrial effluents or water streams containing PAHs.     

The Removal of Hg (II) Ions from Laboratory Wastewater onto Phosphorylated Haloxylon ammodendron: Kinetic and Equilibrium Studies

Haloxylon ammodendron (HA), a desert plant residue, has been utilized as adsorbent material for the removal of Hg (II) ions from laboratory wastewater after treatment with phosphoric acid to form Haloxylon ammodendron cellulose phosphate (HACP). Three levels of HACP having different phosphorous content were prepared. The HACP samples were characterized by estimating the phosphorous content as well as FT-IR spectra. Using the batch experimental systems, the removal of Hg (II) on the HACP particles was investigated. The data of the adsorption isotherm was tested by the Langmuir, Freundlich and Temkin models. The removal processes of Hg (II) onto HACP particles could be well described by pseudo-second order model. The adsorption rate of mercury was affected by the initial heavy metal concentration, initial pH, adsorbent dose and agitation time and temperature as well as extent of modification. The adsorption experiments indicated that the HACP particles have great potential for the removal of Hg (II) from laboratory wastewater. The maximum adsorption capacity (Q_max) of the HACP towards Hg (II) ions was found to be 384.6 and 416.7 and 476.2 mg/g at 30, 40 and 50°C, respectively. Similarly, the Freundlich constant, n values were found to be 6.6, 4.4 and 3.8 at 30, 40 and 50°C, respectively. The thermodynamics constants of the adsorption process: ΔH°, ΔS° and ΔG° were evaluated.     

功能纳米颗粒对木瓜蛋白酶吸附动力学及热力学研究

以磁性纳米颗粒(MNPs)为内核,外层包裹壳聚糖(CS),进一步键和α-酮戊二酸(α-KA),制备出一种新型的磁性离子交换色谱介质(α-KA-CS-MNPs).分别在277,298,310K的均衡条件下,批量法对木瓜蛋白酶进行等温吸附测定,实验所得数据分别用拟一级动力学模型和拟二级动力学模型进行分析.结果表明:拟二级动...     

ADSORPTION OF A LEATHER DYE ON MESOPOROUS STRUVITE OBTAINED FROM SWINE WASTEWATER

Struvite powder obtained from swine wastewater was used as adsorbent to remove an azo leather dye from aqueous solution. The material was characterized by X-ray diffraction, surface area, and atomic force microscopy. The sample presented a single phase having a mesoporous structure and surface area of 35.63 m² g^?1. Langmuir and Freundlich isotherm models were fitted to the adsorption data and both satisfactorily represented the process. The maximum adsorption capacity was 38.14 mg g^?1. From the analysis of thermodynamic parameters such as free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) it was verified that the adsorption process is very fast, spontaneous, and exothermic in nature, with weak forces acting.     

Biosorption of Strontium by a Nonliving Brown Marine Algae,Padina Sp.

The biosorption potential of Padina sp. algae for the removal of strontium from aqueous solutions was studied. The effects of contact time, solution pH, initial metal concentration, and temperature on the strontium uptake by the algae were investigated. The pseudo-first-order, pseudo-second-order, and Weber and Morris kinetic models were applied to test the dynamic experimental data. The pseudo-second-order kinetic model provided the best correlation of the experimental data. The equilibrium experimental results were analyzed in terms of Langmuir, Freundlich, and Sips isotherms. Equilibrium data fitted very well to the Sips model. The maximum uptake estimated by using the Sips model was 330.38 mg/g at pH of 9.5 and temperature 45°C. Using thermodynamic equilibrium coefficients obtained at different temperatures, various thermodynamic parameters, such as ΔG°, ΔH°, and ΔS° were calculated. The thermodynamics of the strontium ion–Padina sp. algaebiosorption system indicate an endothermic process at 288–318 K.     

MODIFIED PLANTAIN PEEL AS CELLULOSE-BASED LOW-COST ADSORBENT FOR THE REMOVAL OF 2,6-DICHLOROPHENOL FROM AQUEOUS SOLUTION: ADSORPTION ISOTHERMS,KINETIC MODELING,AND THERMODYNAMIC STUDIES

In this study, the feasibility of using modified plantain peel to remove 2,6-dichlorophenol from iaqueous solutions was investigated under batch mode. The effects of physical factors such as initial 2,6-dichlorophenol concentration, contact time, biosorbent particle size, biosorbent dosage and temperature on the removal process were evaluated. The results showed that biosorption of 2,6-dichlorophenol was dependent on these factors. The equilibrium biosorption data were analyzed by the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) adsorption isotherm models. The four tested isotherm models provided good fits to the experimental data obtained at 30°C; however, the Freundlich isotherm model provided the best correlation (R² = 0.9874) of the experimental data. The maximum monolayer biosorption capacity (Q _max ) was found to be 14.25 mg/g. The biosorption kinetics data of 2,6-dichlorophenol were analyzed by pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, and liquid film diffusion models. The five kinetic models fitted well to the biosorption kinetic data; however, the pseudo-second-order kinetic model gave the best fit when the biosorption mechanism was controlled by film diffusion. Thermodynamic quantities such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), standard entropy change of biosorption (ΔS°), and activation energy (E_a) were evaluated, and it was found that the biosorption process was spontaneous, feasible, endothermic in nature and of dual nature, physisorption and chemisorption; however, the physisorption process was dominant. Therefore, modified plantain peel has potential for application as an effective bioadsorbent for removal of 2,6-dichlorophenol from aqueous solution.     

Sorption of Cd(II)-MGDA Complexes on Polyacrylate Anion Exchangers

The possibility of polyacrylic anion exchangers application in the removal of Cd(II) complexes with MGDA (methylglycinediacetic acid) from aqueous solutions was presented. Batch sorption experiments were performed using Amberlite IRA 458 and Amberlite IRA 958. The initial solution pH, the initial concentration of sorbed complexes in the molar ratio M(II)-MGDA = 1:1, the temperature, as well as the contact time were varied. The kinetics of Cd(II) sorption in the presence of MGDA was analyzed. The Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models were also applied to describe the adsorption isotherm. The values of the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that in the majority of cases the sorption process was spontaneous and endothermic. From the determined breakthrough curves, the distribution coefficients and the ion exchange capacities were calculated.     

Preparation and characterization of aluminum pillared K10 and KSF for adsorption of trimethoprim

Montmorillonite KSF and K10 were used as precursor materials for synthesis of aluminum pillared K10 and KSF (Al-K10 and Al-KSF) which characterized by TGA, XRD, SEM and FT-IR spectroscopic analysis. The sorption of trimethoprim (TMP) which is commonly employed as an antibiotic onto Al-K10 and Al-KSF was also investigated as a function of adsorbent dosage, solution pH, contact time and temperature. The adsorption kinetics was interpreted using pseudo-first-order, pseudo-second-order kinetic models and intraparticle diffusion model. The pseudo-second-order model provided the best correlation. Adsorption isotherm parameters were obtained from Freundlich, Langmuir and Dubinin–Radushkevich (DR) isotherm models. Adsorption of TMP onto Al-K10 and Al-KSF was physical in nature and ion-exchange mechanism for DR equation, respectively. Al-K10 exhibits higher removal capacity at lower adsorbent dosages in comparison with Al-KSF. The removal capacity was increased by increasing pH. ΔH⁰, ΔS⁰ and ΔG⁰ showed that adsorption of trimethoprim was endothermic, increasing randomness and not spontaneous in nature.     

Enhanced adsorption of heavy metal ions onto simultaneous interpenetrating polymer network hydrogels synthesized by UV irradiation

Simultaneous interpenetrating polymer network (IPN) hydrogels have been prepared by UV-initiated polymerization of a mixture of 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) and triethylene glycol divinyl ether (DVE-3) with enhanced adsorption properties for heavy metal ion removal. The swelling ratio of the IPN hydrogels determined by gravimetric method increased with the AMPS content in the formulation. The IPN hydrogels were used to remove heavy metal ions from aqueous solution. The effects of pH value of the feed solution and AMPS content in the formulation on the adsorption capacity were investigated. The results indicated that the adsorption capacity increased with the pH values and AMPS content in the formulation. Furthermore, the synergistic complexation of metal ions with two polymer networks in the IPN was found in the adsorption studies. The adsorption isotherm of the IPN hydrogels can be well fitted to the Freundlich model. The adsorption kinetics on IPN hydrogels clearly followed an initial transport-controlled adsorption process, but transited to an attachment-controlled adsorption kinetics in the later stage. Thermodynamic parameters such as the Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) for the adsorption were estimated. Results suggested that the adsorption process was a spontaneous, exothermic process that had positive entropy.     

Removal of Copper(II) and Zinc(II) from Aqueous Solutions Using a Lignocellulosic-Based Polymeric Adsorbent Containing Amidoxime Chelating Functional Groups

In this study, the adsorption of Cu(II) and Zn(II) ions from aqueous solutions onto amidoximated polymerized banana stem (APBS) has been investigated. Infrared spectroscopy was used to confirm graft copolymer formation and amidoxime functionalization. The different variables affecting the sorption capacity such as pH of the solution, adsorption time, initial metal ion concentration, and temperature have been investigated. The optimum pH for maximum adsorption was 10.5 (99.99%) for Zn²⁺ and 6.0 (99.0%) for Cu²⁺ at an initial concentration of 10 mg L^?1. Equilibrium was achieved approximately within 3 h. The experimental kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models and are well fitted with pseudo- second-order kinetics. The thermodynamic activation parameters such as ΔG^o, ΔH^o, and ΔS^o were determined to predict the nature of adsorption. The temperature dependence indicates an exothermic process. The experimental isotherm data were well fitted to the Langmuir model with maximum adsorption capacities of 42.32 and 85.89 mg g^?1 for Cu(II) and Zn(II), respectively, at 20°C. The adsorption efficiency was tested using industrial effluents. Repeated adsorption/regeneration cycles show the feasibility of the APBS for the removal of Cu(II) and Zn(II) ions from water and industrial effluents.     

Poly(ethyleneimine) functionalized organic-inorganic hybrid silica by hydrothermalassisted surface grafting method for removal of nickel(II)

Poly(ethyleneimine)-functionalized organic-inorganic hybrid silica adsorbent was synthesized by hydrothermal-assisted surface grafting technique for the removal of Ni(II) ions from aqueous solution, and was characterized by FT-IR, nitrogen adsorption and the static adsorption-desorption experiment method. The results indicated that the maximum static adsorption capacity of Ni(II) on poly(ethyleneimine)-functionalized hybrid silica adsorbent by hydrothermal heating method was 1.6 times as much as the conventional heating method. The poly(ethyleneimine)-functionalized hybrid silica adsorbent offered a fast kinetics for the adsorption of Ni(II), had a substantial binding capacity in the range of pH 4-8 and could be used repeatedly. The Langmuir adsorption model was more favorable than the Freundlich and Dubinin-Radushkevich adsorption models. The adsorption followed a pseudo-second-order model compared with pseudo-first-order model. Various thermodynamic parameters such as ΔG°, ΔH° and ΔS° indicated that the adsorption process was spontaneous and endothermic. The results showed that poly(ethyleneimine)-functionalized hybrid silica adsorbent could be employed as an effective material for the removal of Ni(II) ions from aqueous solution.     

THE UNIT PROBLEM IN THE THERMODYNAMIC CALCULATION OF ADSORPTION USING THE LANGMUIR EQUATION

The equilibrium constant K in the Langmuir isotherm is usually used to calculate the standard Gibbs free energy of adsorption (ΔG°). However, in a strictly theoretical sense, this calculation method is incorrect. The reason is that the K in the Langmuir isotherm has a dimension. According to the provisions of the International Union of Pure and Applied Chemistry (IUPAC), the standard equilibrium constant (K°) for calculating ΔG° must be a dimensionless parameter. We examined four examples from the literature and found that the calculation of ΔG° presented in these four references was incorrect. Based on the fact that this misapplication is very common, this note reviews the related literature and gives a short comment on this problem. Two methods for calculating the thermodynamic equilibrium constant by the Langmuir equation are provided and discussed.