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1.
This paper presents a study on the batch adsorption of a basic dye, methylene blue (MB), from aqueous solution onto ground hazelnut shell in order to explore its potential use as a low-cost adsorbent for wastewater dye removal. A contact time of 24 h was required to reach equilibrium. Batch adsorption studies were carried out by varying initial dye concentration, initial pH value (3–9), ionic strength (0.0–0.1 mol L?1), particle size (0–200 μm) and temperature (25–55°C). The extent of the MB removal increased with increasing in the solution pH, ionic strength and temperature but decreased with increase in the particle size. The equilibrium data were analysed using the Langmuir and Freundlich isotherms. The characteristic parameters for each isotherm were determined. By considering the experimental results and adsorption models applied in this study, it can be concluded that equilibrium data were represented well by Langmuir isotherm equation. The maximum adsorption capacities for MB were 2.14?×?10?4, 2.17?×?10?4, 2.20?×?10?4 and 2.31?×?10?4 mol g?1 at temperature of 25, 35, 45 and 55°C, respectively. Adsorption heat revealed that the adsorption of MB is endothermic in nature. The results indicated that the MB strongly interacts with the hazelnut shell powder.  相似文献   

2.
Sulphuric acid-modified bagasse has been used as low-cost adsorbent for the removal of methylene blue (MB) dye from aqueous solution. In order to remove organic compounds that contribute to chemical oxygen demand (COD), pretreatment with thorough washing of adsorbent using boiling distilled water was performed instead of conventional washing using distilled water at room temperature only. This has resulted in the highest efficiency of color removal of 99.45% and COD reduction of 99.36% for MB dye solution at pH 9. Effects of initial pH, dye concentration, adsorbent dosage, temperature, and contact time have been studied. The adsorption of MB dye was pH dependent. Langmuir and Freundlich isotherm models were tested on the adsorption data. The kinetic experimental data were analyzed using pseudo-first order, pseudo-second order, and the intraparticle diffusion model in order to examine the adsorption mechanisms. The adsorption process followed the Langmuir isotherm as well as the Freundlich isotherm and pseudo-second-order kinetic model. The process was found to be endothermic in nature.  相似文献   

3.
The adsorption capacity of pine tree leaves for removal of methylene blue (MB) from aqueous solution was investigated in a batch system. The effects of the process variables, such as solution pH, contact time, initial dye concentration, amount of adsorbent, agitation speed, salt concentration, and system temperature on the adsorption process were studied. The extent of methylene blue dye adsorption increased with increase in initial dye concentration, contact time, agitation speed, temperature, and solution pH but decreased with increased in amount of adsorbent and salt concentration. Equilibrium data were best described by both Langmuir isotherm and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine tree leaves biomass was 126.58?mg/g at 30?°C. The value of separation factor, R L , from Langmuir equation and Freundlich constant, n, both give an indication of favorable adsorption. The intrapartical diffusion model, liquid film diffusion model, double exponential model, pseudo-first and second order model were used to describe the kinetic and mechanism of adsorption process. A single stage bath adsorber design for the MB adsorption onto pine tree leaves has been presented based on the Langmuir isotherm model equation. Thermodynamic parameters such as standard Gibbs free energy (??G 0), standard enthalpy (??H 0), and standard entropy (??S 0) were calculated.  相似文献   

4.
Cuprous oxide-modified diatomite waste (Cu2O-DW) as a low-cost and effective adsorbent was prepared via a hydrothermal route combined with acid-alkali treatment. The microstructure and surface properties of the obtained Cu2O-DW composite was characterized by Brunauer-Emmett-Teller, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The adsorption behaviors of three different types of dyes such as cationic dye methyl blue (MB), anionic dye acid orange (AO), and reactive dye reactive yellow (RY) onto the as-prepared Cu2O-DW were investigated. Several experimental parameters such as contact time, adsorbent dosage, initial dye concentration, and initial pH values were systematically estimated. The experimental results indicated that as-prepared Cu2O-DW have a better adsorption performance for MB, AO, and RY. Moreover, the kinetic and isotherm models were also used to account for the adsorption mechanism of dye molecules onto Cu2O-DW. The results demonstrated that three different dyes are all fitted well with pseudo-first-order kinetic model. Additionally, the Langmuir and Freundlich isotherm model is more suitable for describing the adsorption process of RY and MB on the as-prepared Cu2O-DW, respectively, and the AO adsorption is propitious to the D-R isotherm model. The value of adsorption energy (E?<?8 kJ mol?1) confirmed that the physical adsorption is dominator during the adsorption process. The findings of the study demonstrated that the synthesized Cu2O-DW composite can be a promising adsorbent for the removal of organic dyes from wastewater and it provided a sustainable development method for cycling the diatomite waste from the brewery.  相似文献   

5.
An organophilic calcined hydrotalcite (OHTC) was prepared by treating calcined hydrotalcite (HTC) with sodium dodecylbenzene sulphonate (an anionic surfactant) to achieve a high loading of thiol functionality through the immobilization of 2-mercaptobenzimidazole (MBI) as a chelating agent. The adsorbent (MBI-OHTC) obtained was characterized using XRD, FTIR, SEM, TG/DTG, surface area analysis and potentiometric titration. The adsorption of MBI-OHTC to remove Hg(II) ions from aqueous solutions was studied as a function of pH, contact time, metal ion concentration, ionic strength and adsorbent dose. The optimum pH range for the maximum removal of Hg(II) was 6.0–8.0. The maximum value of Hg(II) adsorption was found to be 11.63 and 21.52 mg g?1 for an initial concentration of 25 and 50 mg l?1, respectively at pH 8.0. The equilibrium conditions were achieved within 3 h under the mixing conditions employed. A reversible pseudo-first-order used to test the adsorption kinetics. The adsorption mechanism consisted of external diffusion and intraparticle diffusion and the intraparticle mass transfer diffusion was predominated after 20 min of experiment. Extent of adsorption decreased with increase of ionic strength. The experimental isotherm was analyzed with two parameters (Langmuir and Freundlich) and three parameters (Redlich–Peterson) equations. The isotherm data were best modeled by the Freundlich isotherm equation. Complete removal (≈100%) of Hg(II) from 1.0 l of chlor-alkali industry wastewater containing 9.86 mg Hg(II) ions, was possible with 3 g of the adsorbent dose at pH 8.0. About 95.0% of Hg(II) can be recovered from the spent adsorbent using 0.1 M HCl.  相似文献   

6.
The kinetics and mechanism of methylene blue adsorption onto raw pine cone biomass (Pinus radiata) was investigated under various physicochemical parameters. The extent of the methylene blue dye adsorption increased with increases in initial dye concentration, contact time and solution pH but decreases with the amount of adsorbent, salt concentration and temperature of the system. Overall the kinetic studies showed that the methylene blue adsorption process followed pseudo-second-order kinetics among various kinetic models tested. The different kinetic parameters including rate constant, half-adsorption time and diffusion coefficient are determined at different physicochemical conditions. Equilibrium data were best represented by Langmuir isotherm among Langmuir and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine cone biomass was 109.89 mg/g at 30°C. The value of separation factor, R L, from Langmuir equation and Freundlich constant, n, both give an indication of favourable adsorption. Thermodynamic parameters such as standard Gibbs free energy (?G 0), standard enthalpy (?H 0), standard entropy (?S 0) and the activation energy (A) were calculated. A single-stage batch absorber design for the methylene blue adsorption onto pine cone biomass has been presented based on the Langmuir isotherm model equation.  相似文献   

7.
Neutral starch microspheres (NSMs) were synthesized with epichlorohydrin as the cross-linking agent from soluble starch by inverse microemulsion method. Anionic starch microspheres (ASMs) were prepared from NSMs by the secondary polymerization with chloroacetic acid as the anionic etherifying agent. Scanning electron microscopy (SEM) revealed that microspheres had good sphericity and fine dispersibility, and the average particle size was about 75 ??m. The adsorption procedure of Cu2+, Pb2+ on ASMs was carried out by batch experiments, Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms, the adsorption equilibrium data were found to fit the Langmuir and Freundlich isotherm model, the Freundlich isotherm was more adequate than the Langmuir isotherm in simulating the adsorption isotherm of Cu2+,the adsorption of Cu2+, Pb2+ on ASMs was a spontaneous, the isosteric heat of adsorption at different adsorption levels was always negative and indicative of an exothermic process. The pseudo first- and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model, which indicated that the chemical sorption was the rate-limiting step, instead of mass transfer.  相似文献   

8.
In this study, activated red mud was used to develop an effective adsorbent in order to remove a toxic azo dye (tartrazine E102) from aqueous solutions. To increase the adsorption capacity, the red mud was activated by acid-heat treatment using 20 wt.% HCl (RM-HCl). To establish the optimum operating parameters, the influence of pH, adsorbent dose, contact time, initial dye concentration, and stirring rate was investigated. The adsorption equilibrium was studied using Langmuir, Freundlich, Dubinin-Radushkevich, Temkin isotherm models, and the characteristic parameters for each adsorption isotherm were determined. The kinetics of the adsorption process was analyzed by means of pseudo-first-order and pseudo-second-order models. The maximum removal efficiency obtained under optimum conditions was 84.72%. These results were in accordance with the isotherm and kinetic data. The results suggested that tartrazine adsorption process follows the pseudo-second-order kinetic model and also that fits Langmuir isotherm model. The maximum monolayer adsorption capacity was 136.98 mg/g.  相似文献   

9.
The preparation, characterization, and environmental application of crosslinked chitosan-coated bentonite (CCB) beads for tartrazine adsorption have been investigated. CCB beads were characterized by using Fourier transform infrared spectrophotometer (FTIR), scanning electron microscope (SEM), and Brunauer–Emmett–Teller (BET) surface area and Barrett–Joyner–Halenda (BJH) pore size distribution analyses were also determined. The values of pH of the aqueous slurry and pH of zero point charge (pHZPC) were almost equal. The adsorption at equilibrium of tartrazine was found to be a function of pH of the solution, stirring rate, contact time, and tartrazine concentration. The optimum conditions for tartrazine adsorption were pH 2.5, stirring rate of 400 rpm and contact time of 80 min. Pseudo-first-order and pseudo-second-order models were used to analyze the kinetics of adsorption with the latter found to agree well with the kinetics data, suggesting that the rate determining step may be chemisorption. The two most common isotherm models, Langmuir and Freundlich, were used to describe the adsorption equilibrium data. On the basis of Langmuir isotherm model, the maximum adsorption capacities were determined to be 250.0, 277.8, and 294.1 mg g?1 at 300, 310, and 320 K, respectively. Desorption studies were carried out at different concentrations of EDTA, H2SO4, and NaOH. All desorbing solutions showed poor recovery of tartrazine.  相似文献   

10.
Abstract

Zinc adsorption by 10 (pH 4.0–6.5) cultivated mineral soils from Finland was studied in batch experiments. Additions of Zn ranged up to 600 mg kg?1 of soil and the corresponding equilibrium concentrations were 0.1–13 mg 1?1. In each soil, Zn adsorption conformed to the Freundlich isotherm. Despite a relatively low initial Zn adsorption by the acidic soils, each of the soils proved to have a high potential to adsorb Zn, but the capacity was highly pH dependent. In addition to the conventional Freundlich adsorption isotherms, calculated separately for each soil, extended Freundlich-type isotherms that also incorporate soil pH and other soil characteristics were used to describe Zn adsorption of several soils simultaneously in one equation. The pH-dependent Freundlich adsorption isotherm proved to serve as a practical tool to assess Zn adsorption by soils varying in pH and other characteristics.  相似文献   

11.
Laboratory and greenhouse experiments were conducted to determine the influence of soil properties on adsorption and desorption of boron (B) as well as to estimate the degree of reversibility of adsorption reactions. The utility of Freundlich and Langmuir equations for characterizing the plant availability of applied B in soils was established using soybean [Glycine max (L.) Merr.] as a test crop. The adsorption-desorption study revealed that Fe2O3 and clay were primarily responsible for retaining added B in all the 25 different soils under investigation. Organic carbon, pH and cation exchange capacity (CEC) positively influenced the adsorption of B while free Fe2O3, organic carbon and clay retarded release of B from these soils. The degree of irreversibility (hysteresis) of B adsorption/desorption increased with increase in organic carbon and CEC of these soils. Freundlich isotherm proved more effective in describing B adsorption in soils as compared to Langmuir equation. The split Langmuir isotherm demonstrated that any of the adsorption maxima, calculated from lower, upper or entire isotherm, could be of practical use. Contrary, bonding energy coefficient, calculated either at lower or higher equilibrium concentration failed to show any practical benefit. Regression models as a function of B application rate and adsorption equation parameters to predict B uptake from applied B, demonstrated the utility of Langmuir and Freundlich equation parameters.  相似文献   

12.
The adsorption of Cu(II) ions by sodium-hydroxide-treated Imperata cylindrica (SoHIC) leaf powder was investigated under batch mode. The influence of solution pH, adsorbent dosage, shaking rate, copper concentration, contact time, and temperature was studied. Copper adsorption was considered fast as the time to reach equilibrium was 40–90 min. Several kinetic models were applied and it was found that pseudo-second-order fitted well the adsorption data. In order to understand the mechanism of adsorption, spectroscopic analyses involving scanning electron microscope (SEM) coupled with energy-dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectrophotometer were carried out. Ion exchange was proven the main mechanism involved as indicated by EDS spectra and as there was a release of light metal ions (K+, Na+, Mg2+, and Ca2+) during copper adsorption. Complexation also occurred as demonstrated by FTIR spectra involving hydroxyl, carboxylate, phosphate, ether, and amino functional groups. The equilibrium data were correlated with Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. Based on Langmuir model, the maximum adsorption capacity was recorded at the highest temperature of 310 K, which was 11.64 mg g?1.  相似文献   

13.
Poly(acrylamide-acrylic acid-dimethylaminoethyl methacrylate) P(AAm-AA-DMAEMA) resin was prepared by the template copolymerization. PAAm was used as a template for the copolymerization of DMAEMA and AA in aqueous solution using gamma rays. The adsorption of indigo carmine and eriochrome black-T anionic dyes from aqueous media on P(AAm-AA-DMAEMA) has been investigated. The adsorption behavior of this resin has been studied under different adsorption conditions: dye concentrations (50?C500 mg l?1), contact times, temperature (30?C55°C), and pH values (2?C7). The amount of dye adsorbed increased with increasing resin content, but it had a little change with temperature and decreased slightly with increasing pH. Adsorption data of the samples were modeled by the pseudo-first-order and pseudo-second-order kinetic equations in order to investigate dye adsorption mechanism. It was found that the adsorption kinetics of the resin followed a pseudo-second-order model with rate constant (k 2) of 2.5?×?10?3 and 1.8?×?10?2 g (mg?1 min?1) for indigo carmine and eriochrome black-T, respectively. Equilibrium isotherms were analyzed using the Langmuir and Freundlich isotherms. It was seen that the Freundlich model fits the adsorption data better than the Langmuir model.  相似文献   

14.
Co(II) adsorption on high-purity amorphous Fe?CMn binary oxide adsorbent was investigated. The Co(II) adsorption behavior of this synthetic material was studied and discussed as a function of contact time, pH and initial concentration. The Langmuir and Freundlich isotherm models were applied to fit the Co(II) adsorption data on Fe?CMn binary oxide with mesoporous particles of irregular surface morphology and a specific surface area of 201.8?m2?g?1 with a maximum capacity of 32.25?mg?g?1. Various kinetic models applied to the adsorption rate data of the Co(II) ion were evaluated. The results show that the pseudo-second order and the intra-particle mass transfer diffusion models correlated best with the experimental rate data. The adsorption activation energy was found to be 9.07?kJ?mol?1 indicating that it corresponds to a physical adsorption. The evaluated thermodynamics parameters of the adsorption values indicated the endothermic and spontaneous nature of the adsorption. The results obtained confirmed that Fe?CMn binary oxide had the potential to be utilized as a low-cost and relatively effective adsorbent for Co(II) removal from wastewater.  相似文献   

15.
Abstract

The one and two Langmuir, the Freundlich, and the Temkin isotherms were fitted to phsophorus (P) sorption data for P sorption by calcium (Ca)‐bentonite at different initial concentration and pH values of 3.8, 4.8, 6.0, 7.0, 8.0, and 9.0. Each was found to describe P sorption by Ca‐bentonite with comparable success. The effect of pH on P adsorption by Ca‐bentonite was studied and Langmuir, Temkin, and Freundlich isotherms were converted to the forms:

Langmuir: (Co‐X)X= 1/(0.0275–0.0025pH)(12.323–1.061pH) + (Co‐X)(12.323–1.016pH) Temkin: X = (2.45–0.211pH)In(AC) Freundlich: X = (1.324–0.146pH)C(0.172+0044 P H) where: X = (mmol P/kg) the amount of P sorbed per unit weight of soil, C = (μmol P/L) the P concentration in the equilibrium solution, and Co = ((μmol P/L) initial P concentration. It is noteworthy, that the maximum amount (Xm) of P that can be sorbed in a monolayer decreases by increasing of pH. Finally, the B constant of Temkin isotherms is indepented from pH changes.  相似文献   

16.
Abstract

The apparent recovery of applied zinc (Zn) by plants is very low in calcareous soils of Iran because most of it is retained by the soil solids. Subsamples of 24 surface soil (clay 130–530 g kg‐1; pH 7.7–8.4; electrical conductivity 0.63–3.10 dS m‐1; organic matter 6.0–22.0 g kg‐1; cation exchange capacity 8–20 cmol kg‐1; calcium carbonate (CaCO3) equivalent 180–460 g kg‐1) representing 13 soil series in three taxonomic orders were equilibrated with zinc sulphate (ZnSO4) solutions and the amount of Zn disappeared from solution after a 24‐h shaking period was taken as that adsorbed (retained) by the soil solids. The adsorption data were fitted to Freundlich (X=ACB) and Langmuir [X=(K‐bC)/(1+K#lbC)] adsorption isotherms. Backward stepwiseprocedure was used to obtain regression equations with isotherms coefficients as dependent and soil properties as independent variables. Freundlich A and Langmuir K were found to be highly significantly related to pH and clay and increasing as these soil properties increased. But Langmuir b was related only to clay and Freundlich B showed no significant relationship with any of the properties studied. The distribution coefficient (also called maximum buffering capacity), calculated as the product of Langmuir K and b, was also found to be highly significantly related to pH and clay. It is concluded that pH and clay content of calcareous soils are the most influential soil properties in retention of Zn.  相似文献   

17.

Purpose

Anion exchange resin has been shown to be efficient for adsorption of humic acid (HA). However, the mechanism of the effect(s) of the molecular weight (MW) of HA on the adsorption by anion exchange resin needs to be further explored. The objective of this work was to investigated the effect(s) of HA MW on their adsorption and desorption behavior by interacting with anion exchange resin.

Materials and methods

HA fractions with different MW were obtained by ultrafiltration and characterized. For adsorption kinetic study, the magnetic polyacrylic anion exchange resin (NDMP) was shaken with each HA fraction. The amounts of HA in the solutions at different sampling times were obtained by measurement of the total organic carbon. For isotherm study, batch experiments were performed to obtain the isotherms of each HA fractions. The effects of pH value and the regeneration efficiency for HA fractions with different MW were all investigated.

Results and discussion

The characterization reveals that aromaticity of HA increases as the MW rises, while the negative charge follows the order: HA3 (2,500–1,000 Da)?>?HA4 (>10,000 Da)?>?HA2 (1,000–2,500 Da)?>?HA1 (<1,000 Da). The adsorption amount of HA increases as the negative surface charge rises. Thus, HA3 has the largest adsorption amount by NDMP resin among HA fractions, while the adsorption amount of HA1 is the smallest. HA2 adsorption could be modeled by Freundlich equation, suggesting the interaction between HA2 and NDMP is a heterogeneous process. However, the adsorption isotherms of HA3 and HA4 were both better described by Langmuir equation than Freundlich equation. In addition, the resin fouling follows the order: HA2?>?HA1?>?HA4?>?HA3.

Conclusions

The aromaticity of HA freactions increases as MW rises. HA fractions with 1,000?–?2,500 Da have the largest surface negative charge, while the fractions with MW lower than 1,000 Da are almost electroneutral. The adsorptions of HA fractions onto NDMP suggest there is little effect of size exclusion on adsorption, and the adsorption behavior mainly depends on the negative charge of HAs.  相似文献   

18.
Effluents containing phosphorous as phosphate ions are frequently discharged in freshwater resources contributing to the eutrophication and directly interfering in the biological equilibrium. Clam shell residues and sewage sludge were combined for preparing efficient adsorbents for phosphate removal from aqueous medium. The adsorbents were characterized before and after adsorption testing, and the adsorption equilibrium and kinetics were investigated. Phosphate removal of 89?±?1% was attained for samples prepared with 0.1?< X <?1.0, where X corresponds to sewage sludge/clam shell mass ratio. The analyses of the experimental errors indicated that the phosphorous removal followed the Elovich kinetic model, which describes adsorption in very heterogeneous surfaces. On the other hand, the best modelling was achieved using the Koble–Corrigan isotherm model, which incorporate different aspects of both Langmuir and Freundlich isotherms to represent the equilibrium data. The observed adsorption capacity (21.4 mgP g?1) are comparable or greater to that observed for other adsorbents described in the literature.  相似文献   

19.
Boron (B) adsorption increased with increasing concentration. Langmuir adsorption isotherm was curvilinear. The maximum value of adsorption maxima (b1) was observed Sagipora soil and maximum bonding energy (k) constant was in Anantnag soil. The Langmuir isotherm best explains the adsorption trend at low adsorbent concentrations. A significant correlation among b1, clay, and cation exchange capacity was observed. Linear affiliation was observed in all the soils at all concentration, indicating that B adsorption data conform to the Freundlich equation. Soils with greater affinity for B adsorption, like Sagipora, tended to desorb less B. Boron desorption was positively and significantly correlated with sand content and negatively with clay content and cation exchange capacity. The maximum value of 50.76 mg g?1 for desorption maxima (Dm) was observed in Sagipora soil, and mobility constant (Kd) was maximum in Khag soil (0.412 ml kg?1).  相似文献   

20.
Natural zeolite clinoptilolite and synthetic zeolite Na-A were characterized using XRD and SEM to be used as adsorbents for ammonia from aqueous solutions, ground water, and sewage water. Clinoptilolite was mechanically activated for 2, 4, 6, and 8 h to study the effect of activation in enhancing the adsorption capacity. The adsorption by activated natural zeolite and synthetic zeolite is high pH dependent and achieve the best values at pH?=?7. The adsorption capacity of activated natural zeolite increases with increasing the activation from 2 to 8 h achieving removal percentage close to that obtained using synthetic zeolite. The equilibrium was obtained after 60 min for synthetic zeolite and all the activated natural zeolite (except 2-h-activated product, the equilibrium was achieved after 30 min). The kinetic studies reflected the high fitness of the adsorption results of activated natural zeolite products and synthetic zeolite with pseudo-second-order model rather than the other kinetic models. The obtained isotherms reflected the formation of S-type isotherm curve for the adsorption using mechanically activated clinoptilolite and L-type curve for the uptake using synthetic zeolite. The results represented well with Langmuir model followed by Temkin and Freundlich model for adsorption using synthetic zeolite. The uptake using mechanically activated clinoptilolite can be represented by Temkin model rather than both Langmuir and Freundlich models. Thermodynamic parameters indicate spontaneous endothermic adsorption of ammonia using all the zeolitic products under investigation. Finally, the mechanically activated natural zeolite and synthetic zeolite exhibit high efficiency in the removal of ammonia and other water pollutants from ground water and sewage water.  相似文献   

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