改性粉煤灰处理含磷废水的研究

采用浓硫酸固相反应法对粉煤灰进行改性用于含磷废水的净化,考察了pH值,吸附剂用量,磷初始浓度,反应时间对净化过程的影响。通过实验发现溶液pH值在4-10范围内对磷的吸附过程影响不显著,改性粉煤灰可以在较宽的pH值范围内进行脱磷处理;随着粉煤灰加入量的增加和初始溶液中磷酸根浓度的降低,磷的净化率逐渐增加。对于含磷50 mg/L的溶液,当粉煤灰的投加量为1.5%时,磷的吸附效率可达99.66%,净化后水中含磷量为0.17 mg/L。改性粉煤灰对水中磷的净化过程速度较快,5 min可达到最大净化率。改性粉煤灰对磷的吸附等温线符合Freudlich方程。     

Anionic Surfactant Impregnation in Solid Waste for Cu2+ Adsorption: Study of Kinetics,Equilibrium Isotherms,and Thermodynamic Parameters

Coconut shell powder (CP) and diatomite (Di) were modified with microemulsion (μE), producing low-cost adsorbents for copper (II) removal from aqueous solutions. The μE was prepared using as active phase an anionic surfactant sodium octanoate (SO), obtained from the saponification of octanoic acid. The effect of modification on the adsorption capacity of Cu⁺² was evaluated taking into consideration the solution pH, equilibrium time, temperature, and initial concentration of metal in solution. The adsorbents were analyzed by characterization techniques of X-Ray Fluorescence, scanning electron microscope and Fourier Transform Infrared Spectroscopy. The obtained experimental data were analyzed using the equations of Langmuir, Freundlich, Temkin, and Dubinin Radushkevich models. The initial concentration of 50 mg Cu⁺²/L solution and 0.2 g of adsorbent materials modified with the μE presented a Cu⁺² removal efficiency of 86.81% and 96.3% for CP and Di, respectively. The kinetic models of pseudo first-order, pseudo second-order, Elovich, and intraparticle diffusion were used in this study to describe the adsorption rate. The presence of sodium octanoate functional (OS) group provided ion exchange sites suitable to Cu⁺² adsorption. The stability of the OS impregnation using microemulsion was evaluated based on a desorption study.     

Removal of Phosphate from Aqueous Solution Using Zeolite Synthesized from Fly Ash by Alkaline Fusion Followed by Hydrothermal Treatment

The removal of phosphate from aqueous solution by the adsorption process using zeolite synthesized from fly ash was investigated in this study. The XRD patterns revealed that the major crystalline phase of the synthesized zeolite was gismondine. The phosphate immobilization capacity (PIC) increased significantly from 52.7 mg/g of fly ash to 102.9 mg/g of synthesized zeolite after conversion. The batch experiments were conducted to investigate the effect of pH, initial phosphate concentration, and adsorbent amount. The maximum adsorption capacity was obtained at the pH value of 7.0. The adsorption process followed Ho' pseudo-second-order model, and both liquid film and intra-particle diffusion were the rate-controlling step for the process. The adsorption equilibrium data had been analyzed by Langmuir, Freundlich, Radlich-Peterson, Koble-Corrigan, Tempkin, Dubinin-Radushkevich, and Generalized models. The results showed that the Langmuir model gave the best fit. The process was also found to be endothermic. The maximum phosphate adsorption capacity obtained was 132.02 mg/g (30°C), 156.36 mg/g (40°C) and 184.17 mg/g (50°C), respectively, suggesting that the synthesized zeolite is a promising material and can be used to remove phosphate from wastewater.     

Fly ash as a sorbent for boron removal from aqueous solutions: Equilibrium and thermodynamic studies

ABSTRACT

This study presents the application of fly ash from brown coal and biomass burning power plant as a sorbent for the removal of boron ions from an aqueous solution. The adsorption process efficiency depended on the parameters, such as adsorbent dosage, pH, temperature, agitation time and initial boron concentration. The experimental data fitted well with the Freundlich isotherm model and the maximum capacity was found to be 16.14 mg g^?1. The adsorption kinetics followed the pseudo-second-order model. Also, the intra-particle diffusion model parameters were calculated. Thermodynamic parameters such as change in free energy (ΔG°), enthalpy (ΔH°), entropy (ΔS°) revealed on exothermic nature of boron adsorption onto the fly ash.     

Removal of Pb(II) from aqueous solutions by adsorption onto clayey soil of Indian origin: Equilibrium, kinetic and thermodynamic profile

The feasibility of applying natural, untreated clayey soil as low-cost alternative adsorbent for Pb(II) removal from aqueous solutions was investigated with a batch experimental set-up. Experiments were carried out as a function of initial solution pH (1?C8), contact time (10?C360 min), initial Pb(II) concentration (20?C100 mg L^?1), adsorbent dose (0.5?C5 g) and temperature (303?C333 K). Adsorption equilibrium data were well described by the Langmuir isotherm with maximum adsorption capacity of 121.86 mg g^?1 at 303 K. Adsorption of Pb(II) followed pseudo-second-order kinetics. Gibbs free energy (??G⁰) was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The adsorbent was easily regenerated by using 0.1M HNO₃ solution and was reused for five sorptiondesorption cycles without any considerable loss in adsorption capacity. It could be concluded that clayey soil may be used as an inexpensive and effective adsorbent without any treatment or any other modification for the removal of Pb(II) ions from aqueous solutions.     

Adsorption and desorption of copper(II) from solutions on new spherical cellulose adsorbent

An investigation was conducted on the adsorption and desorption of copper(II) from aqueous solutions with a new spherical cellulose adsorbent containing the carboxyl anionic group. Various factors affecting the adsorption were optimized. The adsorption of Cu²⁺ ions on the adsorbent was found to be dependent on the initial time and pH, the concentration, and the temperature. The adsorption process follows both Freundlich and Langmuir adsorption isotherms and was found to be endothermic (ΔH = 23.99 kJ/mol). The Cu²⁺ ions adsorbed on the adsorbent can be recovered with a NaOH or HCl aqueous solution. The maximum percentage of recovery is about 100% when 2.4 mol/L HCl solution is used. In addition, only 7.2% of the adsorption capacity is lost after 30 replications of the adsorption and desorption. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 478–485, 2002; DOI 10.1002/app.10114     

Synthesis and adsorption performance of fly ash/steel slag-based geopolymer for removal of Cu (II) and methylene blue

In order to realize the value-added resource utilization of solid waste, geopolymer particle adsorbents were prepared at low temperatures using silica-aluminum-rich fly ash and steel slag powders as raw materials. In order to investigate the mechanism of their adsorption of dyes and heavy metal ions from wastewater, the effects of steel slag/fly ash ratio, adsorbent dosage, initial concentration of methylene blue (MB) and Cu²⁺ solution, adsorption time and temperature on the adsorption performance of the fly ash/steel slag-based geopolymer adsorbents were investigated, systematically. Results presented that the adsorption capacities of MB and Cu²⁺ were 33.30 and 24.15 mg/g, and the removal efficiencies were 99.90% and 96.59% with the dosages of 3 and 4 g/L geopolymer adsorbents (steel slag/fly ash ratio of 20 wt.%), respectively. The adsorption processes of MB and Cu²⁺ on the adsorbents were in accordance with the proposed pseudo-second-order and Langmuir isotherm models, which mainly included physical and chemical adsorption mechanisms. The adsorption was a spontaneous endothermic process. The fly ash/steel slag-based geopolymer had good removal ability for dyes and heavy metal ions, and it could maintain good adsorption performance after three cycles of regeneration. It had potential application in wastewater treatment.     

Adsorption of Cu2+ Cations from Aqueous Solution by S-doped TiO2

S-doped TiO₂ as a novel adsorbent for Cu²⁺ cations removal from aqueous solutions was synthesized by simple sol-gel process. Removal of Cu²⁺ cations from aqueous solutions was investigated with particular reference to the effects of initial Cu²⁺ cations concentration, pH-value, adsorbent dosage, and temperature on adsorption. It was found that the maximum adsorption capacity was 96.35 mg g^?1 at 328 K. The adsorption equilibrium isotherms and the kinetic data were well described by the Langmuir and pseudo-second-order kinetic models, respectively. The high uptake capability of S-doped TiO₂ makes it a potentially attractive adsorbent for the removal of heavy metal pollutants from aqueous solution.     

用硫酸改性粉煤灰处理含磷废水的研究

以硫酸对粉煤灰进行改性用于含磷废水的净化,考察了pH值,吸附剂用量,磷初始浓度,反应时间、反应温度对净化过程的影响。通过实验发现溶液pH值在8~11范围内对磷的吸附过程影响不显著,改性粉煤灰可以在较宽的pH值范围内进行脱磷处理;随着粉煤灰加入量的增加和初始溶液中磷酸根浓度的降低,磷的净化率逐渐增加。对于含磷<80 mg/L的溶液,当粉煤灰的投加量为3%时,反应温度40℃,磷的吸附效率可达97.6%。改性粉煤灰对水中磷的净化过程速度较快,30~40 min可达到最大净化率。     

EXPERIMENTAL INVESTIGATION ON ADSORPTION OF AMIDO BLACK 10B DYE ONTO ZEOLITE SYNTHESIZED FROM FLY ASH

This work presents experimental studies on adsorptive removal of Amido black 10B dye using a low-cost zeolite synthesized from fly ash to study the effect of various parameters, namely pH, temperature, agitation speed, adsorption time, zeolite loading, and dye concentration, on dye removal efficiency. Dye removal efficiency increased with increase in adsorbent dosage, adsorption time, and stirrer speed, and the optimal values of zeolite dose, adsorption time, and stirrer speed were found to be 10 g/L, 6 h, and 300 rpm respectively. On the other hand, dye removal efficiency decreased with increase in the initial dye concentration as well as temperature, indicating that the adsorption process is exothermic and is effective at low concentrations of adsorbate. Maximum dye removal was obtained at low pH values (between 2 and 5), indicating the fact that the zeolite surface is positively charged. Experimental data matched well with the pseudo-first-order kinetic model and the Freundlich equilibrium isotherm. The most important observation in this work is that zeolite synthesized from fly ash could act as a very effective adsorbent for the removal of amido black dye from its aqueous solutions.     

Characteristics of coal fly ash and adsorption application

Several fly ash samples were collected and their physico-chemical properties were characterised using N₂ adsorption, XRD, SEM, and pH titration. These fly ash samples were applied as low-cost adsorbents for removal of methylene blue and humic acid from aqueous solution. It is found that the adsorption has a close relationship with surface area and pore volume. Higher surface area and pore volume of fly ash will result in higher adsorption of methylene blue (MB) and humic acid (HA). The adsorption of MB and HA on various fly ash samples can reach 7 and 10 mg/g, respectively. Solution pH will also influence humic acid adsorption on fly ash and higher pH will result in lower adsorption. Ionic strength will also influence HA adsorption.     

Removal of Cu2+ and Pb2+ ions from aqueous solutions by starch-graft-acrylic acid/montmorillonite superabsorbent nanocomposite hydrogels

In this study, the removal of copper(II) and lead(II) ions from aqueous solutions by Starch-graft-acrylic acid/montmorillonite (S-g-AA/MMT) nanocomposite hydrogels was investigated. For this purpose, various factors affecting the removal of heavy metal ions, such as treatment time with the solution, initial pH of the solution, initial metal ion concentration, and MMT content were investigated. The metal ion removal capacities of copolymers increased with increasing pH, and pH 4 was found to be the optimal pH value for maximum metal removal capacity. Adsorption data of the nanocomposite hydrogels were modeled by the pseudo-second-order kinetic equation in order to investigate heavy metal ions adsorption mechanism. The observed affinity order in competitive removal of heavy metals was found Cu²⁺ > Pb²⁺. The Freundlich equations were used to fit the equilibrium isotherms. The Freundlich adsorption law was applicable to be adsorption of metal ions onto nanocomposite hydrogel.     

Microwave preparation and properties of O-crosslinked maleic acyl chitosan adsorbent for Pb2+ and Cu2+

A novel chitosan-based adsorbent (CCTM) was prepared by the reaction of epichlorohydrin O-crosslinked chitosan with maleic anhydride under microwave irradiation. The chemical structure of this polymer was characterized by infrared spectroscopy and X-ray diffraction analyses. The effects of various variables such as degree of substitution, adsorption time, initial metal ion concentration, solution pH, and temperature, on the adsorption of Pb²⁺ and Cu²⁺ by CCTM were investigated. The results demonstrate that the microwave irradiation can remarkably enhance the reaction. CCTM has higher adsorption capacity than chitosan. The maximum adsorption capacities for Pb²⁺ and Cu²⁺, with initial concentrations of 0.02 mol L⁻¹ at pH 5, are 246.3 and 132.5 mg g⁻¹, respectively. The adsorbent can be recycled. These results have important implications for the design of effective chitosan-based adsorbents in the removal of heavy metal ions from wastewaters. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

EFFECT OF TEMPERATURE ON THE ADSORPTION OF METHYLENE BLUE DYE ONTO SULFURIC ACID–TREATED ORANGE PEEL

The present study explains the preparation and application of sulfuric acid–treated orange peel (STOP) as a new low-cost adsorbent in the removal of methylene blue (MB) dye from its aqueous solution. The effects of temperature on the operating parameters such as solution pH, adsorbent dose, initial MB dye concentration, and contact time were investigated for the removal of MB dye using STOP. The maximum adsorption of MB dye onto STOP took place in the following experimental conditions: pH of 8.0, adsorbent dose of 0.4 g, contact time of 45 min, and temperature of 30°C. The adsorption equilibrium data were tested by applying both the Langmuir and Freundlich isotherm models. It is observed that the Freundlich isotherm model fitted better than the Langmuir isotherm model, indicating multilayer adsorption, at all studied temperatures. The adsorption kinetic results showed that the pseudo-second-order model was more suitable to explain the adsorption of MB dye onto STOP. The adsorption mechanism results showed that the adsorption process was controlled by both the internal and external diffusion of MB dye molecules. The values of free energy change (ΔG ^o) and enthalpy change (ΔH ^o) indicated the spontaneous, feasible, and exothermic nature of the adsorption process. The maximum monolayer adsorption capacity of STOP was also compared with other low-cost adsorbents, and it was found that STOP was a better adsorbent for MB dye removal.     

Kinetics, mechanism, isotherm and thermodynamic analysis of adsorption of cadmium ions by surface-modified Strychnos potatorum seeds

The surface-modified Strychnos potatorum seeds (SMSP) were used as an effective low-cost adsorbent for the removal of cadmium ions from aqueous solution. SMSP was characterized by Fourier transform infrared spectroscopy and scanning electron microscopic analyses. The effect of operating variables such as solution pH, adsorbent dose, contact time, initial cadmium ions concentration and temperature on the removal of cadmium ions were studied in a batch mode adsorption operation. The optimum conditions for the adsorption of cadmium ions onto the SMSP were found to be: pH of 5.0, SMSP dose of 2 g/L, contact time of 30min, temperature of 30 °C for an initial cadmium ions concentration of 100 mg/L. Kinetic data were analyzed using the pseudo-first order and pseudo-second order kinetic equations, intraparticle diffusion model, Boyd kinetic model and shrinking core model. The characteristic parameters for each model have been estimated. Adsorption of cadmium ions onto the SMSP follows the pseudo-second order kinetic model. The rate-limiting steps in the adsorption process were found to be external and internal diffusion. Equilibrium data were well described by the Langmuir isotherm model than the Freundlich isotherm model, which yields a maximum monolayer adsorption capacity of 200 mg/g. Thermodynamic parameters such as standard free energy change, enthalpy change and entropy change were also estimated. The results show that the removal of cadmium ions by the SMSP was found to be spontaneous and exothermic.     

Preparation and characterization of a novel nanocomposite of clinoptilolite/maghemite/chitosan/urea for manganese removal from aqueous solution

Synthesis of a new magnetic nanocomposite of Clinoptilolite/Maghemite/Chitosan/Urea has been carried out to introduce an adsorbent to remove manganese as a toxic heavy metal from aqueous solution. Clinoptilolite zeolite became magnetic using the maghemite nanoparticles, then coated using chitosan as a biodegradable and non-toxic polymer, and finally functionalized by urea to increase the adsorption capacity. For characterization of the nanocomposite, the X-Ray diffraction, IR spectroscopy, vibrating sample magnetometery, and scanning electron microscopy were used. The effects of temperature, contact time, initial metal concentration, solution pH and adsorbent dose on the manganese removal capacity were evaluated. The kinetics of adsorption by the pseudo-first-order, pseudo-second-order, and Elovich kinetic models was studied and the results suggested the compliance of pseudo-second-order kinetic model with the kinetic data. The maximum adsorption capacity of manganese under the optimum condition of pH=2.13, the adsorbent amount of 0.02 g, initial solution concentration of 46.00 mg/L with response surface methodology, equaled 16.30 mg/g. The Langmuir, Freundlich, Temkin and Dobinin-Rudoshkovich adsorption isotherm models were investigated and Langmuir best fit the isotherm data. In the study of the thermodynamic results, negative Gibbs free energy represents the spontaneous nature of manganese removal process.     

Comparative removal of two textile dyes from aqueous solution by adsorption onto marine-source waste shell: Kinetic and isotherm studies

Scallop shell was used as a low-cost adsorbent for removal of two anionic textile dyes, Reactive Blue 19 (RB19) and Acid Cyanine 5 R (AC5R), from aqueous solutions. The adsorbent was characterized using inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The dye removal efficiency of scallop shell was determined as function of contact time, solution pH, initial dye concentration and adsorbent dosage. With increasing dye concentration, the adsorption of both dyes decreased, while it increased with increasing adsorbent dosage. Optimum removal of RB19 and AC5R was achieved at pH=6. Adsorption equilibrium data were well described by the Freundlich model. The maximum dye adsorption capacity of scallop shell as estimated from the Langmuir isotherm was 12.36 and 12.47 mg/g for RB19 and AC5R, respectively. The adsorption kinetic data showed excellent correlation with the pseudosecond-order model. It was concluded that scallop shell has a remarkable potential for the sorption of RB19 and AC5R and can be used for treatment of the dye contaminated wastewater.     

褐煤吸附MTBE(甲基叔丁基醚)的研究分析

MTBE(甲基叔丁基醚)作为一种汽油添加剂,在水环境中难降解并且不易被有机物吸附。采用颗粒状活性褐煤作为吸附剂去除水溶液中的MTBE,配制样品浓度范围为1.7μg/L~1.9 g/L。实验发现,pH值不影响吸附过程,MTBE的吸附更符合Freundlich吸附模型。在溶液起始浓度为1100 mg/L时,褐煤的最大吸附能力为21.5 mg/g。在MTBE起始浓度为74μg/L时,3 h后达到吸附平衡并且MTBE去除效率达到97.03%。由此可见,褐煤的吸附能力较高,吸附速度较快,可以作为从水溶液中去除MTBE的有效吸附剂。     

Study on the phosphate removal from aqueous solution using modified fly ash

In this work the fly ash was modified by sulfuric acid for the removal of phosphate. It was found that modification of fly ash could significantly enhance the phosphate immobilization ability of the fly ash. The specific surface area of the fly ash increased from 8.8 to 32.5 m²/g after treated with sulfuric acid. The modification of the fly ash also resulted in the mobilization of acid-soluble metal ions due to partial or complete dissolution of the metals under the acidic conditions. Both adsorption and precipitation contributed to the removal of phosphate by the modified fly ash but precipitation was a major mechanism of phosphate removal. The experimental results showed that adsorption of phosphate by the modified fly ash was rapid, the removal percentage of phosphate could reach maximum in 5 min. In the range of 5–9, pH did not significantly affect the removal of phosphate and the removal percentage of phosphate increased with the increase of adsorbent dosage. The adsorption of phosphate by the modified fly ash could be described well by Langmuir isotherm equation, the Langmuir constant Q₀ was 9.15 mg g⁻¹. The XRD patterns and the SEM images of modified fly ash after sorption revealed that CaHPO₄·2H₂O was formed in the removal of phosphate. In addition, phosphate also formed precipitate with aluminum and iron.     

Adsorption Characteristics of Congo Red from Aqueous Solution onto Tea Waste

The feasibility of using tea waste (TW) as a low-cost adsorbent for the adsorption of an anionic dye (Congo red) from aqueous solution has been investigated. Adsorption in a batch process was conducted to study the effect of adsorbent dosage, initial dye concentration, contact time, pH, and temperature. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin models. The adsorption system was best described by the Langmuir isotherm (R ² > 0.99). Adsorption kinetics followed a pseudo-second-order model (R ² > 0.99). The effect of mechanical treatment (vibratory mill) was also studied. The experimental results showed that using this physical treatment leads to an increase in the adsorption capacity of TW from 32.26 to 43.48 mg/g. Thermodynamic analyses revealed that the adsorption of Congo red on TW was endothermic and spontaneous in nature. The results indicated that TW can be employed as a potential low-cost adsorbent for the removal of Congo red from aqueous solution.