Removal of malachite green from aqueous solution by zinc oxide nanoparticle loaded on activated carbon: Kinetics and isotherm study

In this research, a novel adsorbent, zinc oxide nanoparticle loaded on activated carbon (ZnO-NP-AC) was synthesized by a simple, low cost and efficient procedure. Subsequently, this novel material was characterizated and identified by different techniques such as Brunauer, Emmett and Teller (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analysis. Unique properties such as high surface area (>603 m²/g) and low pore size (<61 Å) and average particle size lower than 100 Å in addition to high reactive atom and presence of various functional groups make it possible for efficient removal of malachite green (MG). In batch experimental set-up, optimum conditions for quantitative removal of MG by ZnO-NP-AC was attained following searching effect of variables such as adsorbent dosage, initial dye concentration and pH. Optimum values were set as pH of 7.0, 0.015 g of ZnO-NP-AC at removal time of 15 min. Kinetic studies at various adsorbent dosage and initial MG concentration show that maximum MG removal was achieved within 15 min of the start of every experiment at most conditions. The adsorption of MG follows the pseudo-second-order rate equation in addition to interparticle diffusion model (with removal more than 95%) at all conditions. Equilibrium data fitted well with the Langmuir model at all amount of adsorbent, while maximum adsorption capacity was 322.58 mg g⁻¹ for 0.005 g of ZnO-NP-AC.     

Solid phase extraction and removal of brilliant green dye on zinc oxide nanoparticles loaded on activated carbon: New kinetic model and thermodynamic evaluation

The brilliant green (BG) solid phase extraction of carried out following accumulation on including zinc oxide nanoparticles loaded on activated carbon (ZNO-NP-AC) non-toxic and green as material. The influence of variables such as pH, initial BG concentration, contact time, amount of adsorbent, eluent and temperature on BG removal and recoveries were studied and optimized. The high correlation coefficient and possibility of accurate prediction and explanation of experimental data by novel kinetic model show its applicability and superiority for representation of experimental data. The results of present model compared with traditional kinetic models (pseudo-first and second order and intraparticle diffusion model). Additionally, fitting the experimental equilibrium data to numerous conventional isotherm models show that the Langmuir model with high correlation coefficient and low error analysis is more usable to explain the experimental data. The calculated change in entropy and enthalpy of BG adsorption on proposed adsorbent was 136.59 J mol⁻¹ K⁻¹ for 15.0 mg L⁻¹ and 65.2 J mol⁻¹ K⁻¹ 35.2 kJ/mol and 16.1 kJ/mol for 15 mg L⁻¹. The quantitative elution of retained BG by 2.0 mL of EtOH make permit accurate and repeatable monitoring off BG over wide linear range (0.2–500 ng mL⁻¹) with limits of detection (LODs) of 0.08 ng mL⁻¹. The preconcentration factors were 75 and loading half time (t_1/2) values were less than 5 min.     

Comparison of removal of bromothymol blue from aqueous solution by multiwalled carbon nanotube and Zn(OH)2 nanoparticles loaded on activated carbon: A thermodynamic study

In this research Zn(OH)₂ nanoparticles loaded on activated carbon (Zn(OH)₂-NPs-AC) as novel adsorbent and raw multiwalled carbon nanotube (MWCNT) were applied for efficient removal of bromothymol blue (BTB). Both adsorbent has been characterized with different techniques such and SEM, XRD and UV–vis spectrometry. Their size was less than 100 nm. In the removal process the variables are pH, temperature, concentration of BTB, amount of adsorbent and contact time that their influence on removal of BTB was optimized using one at a time approach in batch procedure. Adsorptions of BTB on bath adsorbent depend highly on pH. Following the investigation of temperature effect, the thermodynamic parameters including change in entropy, enthalpy and free Gibbs energy were calculated. For both adsorbents, positive value of enthalpy and negative value of ΔG⁰ show routine feasibility of adsorption using energy. At optimum value of variables, the removal processes onto both adsorbent have high adsorption capacity for best fitting model Langmuir, i.e. for Zn(OH)2-NP-AC and 150 mg/g for PAC. The adsorption rates were well explained with pseudo second order and interparticle diffusion model. It is expected that there could an increase in the number of reactive sites due to their expected high volume, pore size and high surface area.     

用活性炭吸附强化超滤过程脱除废水中染料的研究(英文)

In this study, orange G dye was efficiently removed from aqueous solution by ultrafiltration (UF) mem-brane separation enhanced with activated carbon adsorption. The powdered activated carbon (PAC) was deposited onto the UF membrane surface, forming an intact filter cake. The enhanced UF process simultaneously exploited the high water permeation flux of porous membrane and the high adsorption ability of PAC toward dye molecules. The influencing factors on the dye removal were investigated. The results indicated that with sufficient PAC incor-poration, the formation of intact PAC filtration cake led to nearly complete rejection for dye solution under opti-mized dye concentration and operation pressure, without large sacrificing the permeation flux of the filtration process. Typically, the dye rejection ratio increased from 43.6% for single UF without adsorption to nearly 100% for the en-hanced UF process, achieving long time continuous treatment with water permeation flux of 47 L·m 2·h 1. The pre-sent study demonstrated that adsorption enhanced UF may be a feasible method for the dye wastewater treatment.     

Equilibrium,kinetic and thermodynamic study of removal of reactive orange 12 on platinum nanoparticle loaded on activated carbon as novel adsorbent

The proposed research describes the synthesis and characterization of platinum nanoparticles loaded on activated carbon (Pt-NP-AC) and its efficient application as novel adsorbent for efficient removal of reactive orange 12 (RO-12). The influences of effective parameters following the optimization of variables on removal percentages, their value was set as 0.015 g Pt-NP-AC, pH 1, contact time of 13 min. At optimum values of all variables at 25 and 50 mgL⁻¹ of RO-12 enthalpy (ΔH⁰) and entropy (ΔS⁰) changes was found to be 59.89 and 225.076, respectively, which negative value of ΔG⁰ shows a spontaneous nature, and the positive values of ΔH⁰ and ΔS⁰ indicate the endothermic nature and adsorption organized of dye molecule on the adsorbent surface. Experimental data was fitted to different kinetic models including first-order, pseudo-second-order, Elovich and intra-particle diffusion models, and it was seen that the adsorption process follows pseudo-second-order model in consideration to intra-particle diffusion mechanism. At optimum values of all variables, the adsorption process follows the second-order kinetic and Langmuir isotherm model with adsorption capacity 285.143 mg g⁻¹ at room temperature.     

Intraparticle diffusion of cadmium and zinc ions during adsorption from aqueous solution on activated carbon

The adsorption isotherms of cadmium(II) and zinc(II) onto activated carbons were obtained in a batch adsorber. The concentration decay data were obtained in a rotating basket adsorber and were interpreted by a mathematical model, which takes into account the adsorption rate, external mass transport and intraparticle diffusion. The results showed that the overall rate of adsorption of Cd(II) and Zn(II) was mainly controlled by the intraparticle diffusion which was solely due to pore volume diffusion. The contribution of the external mass transport resistance was negligible. The effective pore volume diffusivities of Cd(II) and Zn(II) were predicted reasonably well using the ionic diffusivity of the metal and the void fraction and tortuosity of activated carbon. Copyright © 2005 Society of Chemical Industry     

Adsorption of anionic surfactants and related compounds from aqueous solution onto activated carbon and synthetic adsorbent

The adsorption isotherms of two anionic surfactants and sodium alkyl sulfonates with various carbon numbers onto activated carbon and synthetic adsorbent were measured in aqueous solutions. The adsorption affinities remarkably increased with an increase in the length of alkyl group in the adsorbates for both adsorbents. Furthermore, the amount of adsorption increases with addition of sodium chloride into the solutions. These behaviors suggested that the effect of hydrophobic interactions seem to play an important role on adsorption of both adsorbents.     

Activated carbon from bacterial cellulose as an effective adsorbent for removing dye from aqueous solution

ABSTRACT

Novel activated carbon (AC) derived from bacterial cellulose (BC-AC) was produced by phosphoric acid activation at a carbonization temperature of 500 °C. BC-AC possesses mesoporous structures of 2.3 nm in diameter, porosity of 1.0 cm³/g and surface area of 1734 m²/g with high thermal stability between 100 and 500 °C. BC-AC could be used as an effective adsorbent for removing methylene blue (MB) from aqueous solutions with the maximum adsorption capacity of 505.8 mg/g. BC-AC presented physisorption and the adsorption of MB was most likely to be a monolayer adsorption. The Redlich–Peterson model displayed the best fit with the experimental data.     

Formation of carbon nanoparticles from soluble graphene oxide in an aqueous solution

Graphite oxide was prepared by the Hummers method. Then after further oxidation, a new kind of carbon nanoparticle, with diameter 10-30 nm, was formed in the aqueous solution. On the basis of structural characterization by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy it is deduced that the nanoparticles are generated by the self-assembly of few-layer graphene oxides. A possible formation mechanism is proposed.     

Adsorption of silver complexes on carbon from aqueous solution

The adsorption of silver diammine complex on graphitized carbon black has been studied in aqueous ammonia solution. The carbon black has been gasified to various levels of burnoff in order to increase its active surface area (ASA). The effect of different parameters, ASA, concentrations of silver diammine and of ammonium cations on the silver adsorption has been investigated. The metal complex interacts specifically with the active sites located in the ASA where it undergoes a reduction to metallic silver. A phenomenological model of the adsorption and decomposition reactions of the silver complex is proposed.     

Boron removal from water and its recovery using iron (Fe) oxide/hydroxide-based nanoparticles (NanoFe) and NanoFe-impregnated granular activated carbon as adsorbent

This study presents information obtained by the synthesis of Fe(3) oxide/hydroxide nanoparticles sol (NanoFe) and NanoFe-impregnated granular activated carbon as adsorbents for boron removal from solutions. The research describes an adsorption method for cleaning a solution containing boron contaminants followed by recovery of the adsorbent and the adsorbed material for safe removal or further reuse. The technology provides an efficient method of boron removal from water. A marked effect of NanoFe and NanoFe-impregnated GAC adsorbents concentration and pH level on boron removal efficiency was demonstrated. At least 95–98% boron recovery efficiency is possible using NanoFe sol and Fe-impregnated GAC that in fact also recover the adsorbent for reuse. Boron adsorption onto the NanoFe-impregnated GAC adsorbent may be described by pseudo-second-order reaction kinetics and the Langmuir isotherm model. The boron adsorption capacity on iron (3) oxide nanoparticles and Fe-impregnated GAC at an equilibrium concentration of 0.3 mg/dm³ as B in the solution is much higher than these values for similar adsorbents reported in the literature.     

Removal of methylene blue dye from aqueous solution by activated carbon prepared from cashew nut shell as a new low-cost adsorbent

Methylene blue dye was adsorbed on an adsorbent prepared from cashew nut shell. A batch adsorption study was carried out with variable adsorbent amount, initial dye concentration, contact time and pH. Studies showed that the pH of aqueous solutions affected dye removal as a result of removal efficiency increased with increasing solution pH. The experimental data were analyzed by the Langmuir, Freundlich, Redlich-Peterson, Koble-Corrigan, Toth, Temkin, Sips and Dubinin-Radushkevich models of adsorption using MATLAB 7.1. The experimental data yielded excellent fits within the following isotherm order: Redlich-Peterson>Toth>Sips>Koble-Corrigan>Langmuir>Temkin>Dubinin-Radushkevich>Freundlich, based on its correlation coefficient values. Three simplified kinetic models including a pseudofirst-order, pseudo-second-order and intraparticle diffusion equations were selected to follow the adsorption process. It was shown that the adsorption of methylene blue could be described by the pseudo-second-order equation. The results indicate that cashew nut shell activated carbon could be employed as a low cost alternative to commercial activated carbon in the removal of dyes from wastewater.     

Adsorption studies on copper,cadmium, and zinc ion removal from aqueous solution using magnetite/carbon nanocomposites

Magnetite/carbon nanocomposites were tested as adsorbents for removal of metal ions from aqueous solutions. The effect of adsorption parameters such as solutions pH (ranging between 2 and 9), the nature and the quantity of the sorbent (10, 20, 40, and 60 mg), initial concentration of metal ions (10, 30, 50, 100, and 150 mg/L), and temperature (25, 45, and 65°C) was evaluated. The removal efficiency of metal ions depends on solution pH and increases with increasing carbon content, the dose of magnetite/carbon nanocomposites, and the temperature and decrease with initial concentration of the metal ions. The adsorption kinetics was described by pseudo-second-order model, and the equilibrium experimental data were well fitted to the Sips isotherm, yielding a maximum adsorption capacity of 41.11, 76.67, and 48.45 mg/g for copper, cadmium, and zinc, respectively. The thermodynamic parameter Gibbs free energy was determined to be negative, which indicated that the adsorption process is spontaneous. The optimum conditions (1 g/L adsorbent, 25°C, and pH 6) were selected for removal of metal ions from real wastewaters, with good results indicating that investigated nanocomposites could be used for the application in real systems.     

Competitive adsorption of Direct Yellow 12 and Reactive Orange 12 on ZnS:Mn nanoparticles loaded on activated carbon as novel adsorbent

A novel adsorbent (ZnS:Mn nanoparticles loaded on activated carbon) was made. The competitive adsorption of Direct Yellow 12 (DY12) and Reactive Orange 12 (RO12) dyes in binary mixture onto this adsorbent was studied. DY12 and RO12 with severe spectra overlapping were chosen and analyzed simultaneously with high accuracy by first order derivative spectrophotometric method in binary solutions. The effect of multi-solute systems on the adsorption capacity was investigated. Because of the specific characteristics of ZnS:Mn-NP-AC was found to be efficient for the removal of the dyes studied. The adsorption capacities were investigated and described by the mono- and multi-component Langmuir and Freundlich isotherm models for both single and binary dye solutions. The isotherm constants for DY12 and RO12 were calculated. For single solution of DY12 and RO12 dyes, the adsorption capacities of the applied adsorbent were found to be 90.05 mg/g and 94.52 mg/g, respectively. Equilibrium uptake amounts of DY12 and RO12 in binary solution onto the applied adsorbent were found to be considerably decreasing with increasing the concentrations of the other dye. A better agreement between the adsorption equilibrium data and mono-component Langmuir isotherm model was found. However, at concentrations within moderate ranges, the extended Freundlich isotherm model satisfactorily predicted multi-component adsorption equilibrium data. An endothermic and a spontaneous nature for the adsorption of the dyes studied were shown from thermodynamic parameters.     

Application of experimental design for removal of sunset yellow by copper sulfide nanoparticles loaded on activated carbon

In this study, copper sulfide nanoparticles loaded on activated carbon (CuS-NP-AC) was synthesized by novel, low cost and green approach and characterized using different techniques such as SEM, and BET. This material was used for the removal of sunset yellow (SY) from aqueous solutions was investigated. The dependency of removal percentages to variables such as pH, initial SY concentration, adsorbent dosage and sonication time were studied by central composite design (CCD) coupled with response surface methodology (RSM) by considering the desirability function (DF). The accuracy and ability of method at optimum values predicted by this model was studied by conduction of similar experiments at the same previously optimized conditions. A good agreement between experimental and predicted data was achieved that efficiency of this model for prediction of real optimum point. Among the well known previously isotherm models, the experimental equilibrium data efficiently can be represented by the Langmuir model, while the rate of adsorption. Kinetic data efficiently can be interpreted by combination of pseudo-second order as well as intraparticle diffusion models. The small amount of this adsorbent (0.016 g) is applicable for removal of high amount of SY (>90%) in reasonable time (17 min).     

Electrophoretically deposited halloysite nanotubes coating as the adsorbent for the removal of methylene blue from aqueous solution

Halloysite nanotubes (HNTs) coatings were prepared by electrophoretic deposition (EPD) from different alcoholic suspensions using polyethyleneimine (PEI) as the dispersant. The results of conductivity, zeta potential, FTIR and thermal analysis showed that PEI is protonated in alcoholic suspensions and then adsorbed on the surface of HNTs enhancing their zeta potential and so colloidal stability. Optimum concentration of PEI decreased with molecular size of alcohol due to the more adsorption of PEI on HNTs. Kinetics of EPD was the fastest from the suspensions with the highest zeta potential. HNTs coatings exhibited high resistance against cracking during their drying due to the self-reinforcement provided by long HNTs and the presence of PEI in their composition which acts as the binder. The coating (6cm²) deposited from ethanolic suspension with 0.5?g/l of PEI (optimum suspension) removed 36% of MB from its aqueous solution (concentration: 5?mg/l and volume: 30?ml) within 2?h.     

Random forest model for removal of bromophenol blue using activated carbon obtained from Astragalus bisulcatus tree

In this research, activated carbon (AC) simply was prepared from a local, abundant tree in south of Iran. The AC with low cost and toxicity is a good candidate for bromophenol blue (BPB) removal from aqueous media. The AC with nano scale pore diameter is applicable for this dye removal following optimization of the influence of various parameters including contact time, pH, initial dye concentration and amount of adsorbent. Subsequently, experimental data was analyzed by four kinetic models including pseudo first and second-order, Elovich and the intraparticle diffusion equations and subsequently their respective parameters such as rate constants, equilibrium adsorption capacities and correlation coefficients was investigated and based on well known criterion their applicability was judged. The result shows that adsorption of BPB onto proposed adsorbent at all conditions such as versatile adsorbent dosages and initial BPB concentrations sufficiently described by the combination of the pseudo second-order equation and interparticle diffusion model. It was found that equilibrium rate of the BPB adsorption at various adsorbent dosage well fitted by Langmuir. Investigation of experimental result by two approaches (multiple linear regressions (MLR) and random forest (RF)) models show that RF is a powerful tool for prediction of BPB adsorption by activated carbon obtained from Astragalus bisulcatus tree. The optimal tuning parameters for RF model are obtained based on the n_tree = 100, m_try = 2. For the training data set, the MSE values of 0.0006 and the coefficient of determination (R²) values of 0.9895 for RF model and the MSE value of 0.0104 and the R² value of 0.823 for MLR model are obtained.     

Dual role of activated carbon as fuel and template for solution combustion synthesis of porous zinc oxide powders

In this work, nanosized zinc oxide (ZnO) powders were fabricated by urea–nitrate solution combustion synthesis using activated carbon as a structure-directing template and secondary fuel at different fuel–oxidant ratios. The as-synthesized powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption–desorption measurements, UV–Vis diffuse reflectance spectroscopy, and photoluminescence. The effect of fuel amount on photocatalytic activity of ZnO powders was evaluated by the degradation of an azo dye Orange G. It was observed that combustion synthesis with activated carbon as a secondary fuel had a profound effect on reducing crystallite size and enhancement of specific surface area. The crystallite size of the as-synthesized powders varied from 46 to 26 nm. The ZnO powder prepared at a fuel–oxidant ratio of 1.8 possessed the small crystallite size and high specific surface area of 69 m²/g. It correspondingly resulted in the highest dye removal percentage of 99% with a rate constant of 0.027 min⁻¹. The improvement in dye degradation can be due to the synergistic interaction and interplay of enhanced surface area and catalytic ability of the photocatalyst. This study provides a simple single-step synthesis methodology to produce metal oxide nanopowders with tunable surface properties for high potential applications in catalysis, optoelectronics, and gas sensors.     

Adsorption of thiram from aqueous solution on activated carbon and sepiolite

Adsorption of thiram on activated carbon and acid-heat treated sepiolite from aqueous solution at 10° C, 20° C, 30° C and 40° C has been studied. The adsorption isotherms may be classified as L type of the Giles classification which suggests that there is no strong competition from the solvent for adsorption sites. The experimental data points have been fitted to the Langmuir equation in order to calculate the adsorption capacities of the solids as well as their surface areas available to the thiram molecules. The removal efficiency (P) has been calculated for both adsorbents resulting that activated carbon is more effective (P = 98–100%) in removing thiram from aqueous solution than acid-heat treated sepiolite (P = 14–52%).     

Production of hydroxyapatite-based adsorbent for the removal of cobalt ions from the aqueous solution

The aim of the current study was to recover and separate cobalt ions from multielement solution, using hydroxyapatite (HAp) and magnetic nanocomposite of HAp/Fe₃O₄ as adsorbents. Cobalt ion adsorption process was conducted batchwise within the temperature 25˗55°C, exposure duration 5˗120 min by applying a dose of 0.25–5 g/L as the adsorbent at pH 2 to 9.  Adsorbent characterization was performed using advanced spectroscopic techniques such as Fourier Transform Infrared Spectroscopy, Scanning electron microscopy, and Energy-dispersive X-ray spectroscopy. The maximum ionic adsorption efficiency using HAp was 90.48% against 94.72% in the case of the magnetic nanocomposite of HAp, under optimal conditions. Various isotherm models were used to evaluate the adsorption capacity and equilibrium coefficients for adsorption of the cobalt ions by the prepared adsorbents. The isotherm models data showed that the adsorption process is desirable by the adsorbents and by adding nanoparticles of Fe₃O₄ the adsorption capacity improves.