Synthesis of zeolite Na-P1 from coal fly ash produced by gasification and its application as adsorbent for removal of Cr(VI) from water

The coal fly ash produced by gasification is estimated to be over 80 million ton per year in China by 2021. It has mainly been disposed as solid waste by landfill. There is lack of study focused on its utilization. In this paper, the coal fly ash produced by gasification was at first analyzed and then applied to synthesize zeolite as an adsorbent. The effects of synthesis conditions on the cation exchange capacity (CEC) of zeolite were investigated. The results from X-ray diffraction and scanning electron microscope indicated that the crystallinity of the synthesized zeolite is the most important factor to affect the CEC. When the synthesized zeolite with the highest CEC (275.5 meq/100 g) was used for the adsorption of Cr(VI) from aqueous solution, the maximum adsorption capacity for Cr(VI) was found to be 17.924 mg/g. The effects of pH, contact time and initial concentration on the adsorption of Cr(VI) were also investigated. The adsorption kinetics and isotherms can be well described by the pseudo-second-order model and Langmuir isotherm model, respectively.     

Removal of Boron from Aqueous Solutions by Adsorption Using Fly Ash,Zeolite, and Demineralized Lignite

In the present study for the purpose of removal of boron from water by adsorption using adsorbents like fly ash, natural zeolite, and demineralized lignite was investigated. Boron in water was removed with fly ash, zeolite, and demineralized lignite with different capacities. Ninety-four percent boron was removed using fly ash. Batch experiments were conducted to test the removal capacity, to obtain adsorption isotherms, thermodynamic and kinetic parameters. Boron removal by all adsorbents was affected by pH of solution; maximum adsorption was achieved at pH 10. Adsorption of boron on fly ash was investigated by the Langmuir, Freundlich, and the Dubinin-Radushkevich models. Standard entropy and enthalpy changes of adsorption of boron on fly ash were, ΔS ⁰  = ?0.69 kJ/mol K and ΔH ⁰  = ?215.34 kJ/mol, respectively. The negative value of ΔS ⁰ indicated decreased randomness at the solid/solution interface during the adsorption boron on the fly ash sample. Negative values of ΔH ⁰ showed the exothermic nature of the process. The negative values of ΔG ⁰ implied that the adsorption of boron on fly ash samples was spontaneous. Adsorption of boron on fly ash occurred with a pseudo-second order kinetic model, and intraparticle diffusion of boron species had also some effect in adsorption kinetics.     

改性Zr-Na/Zeolite双功能沸石脱除水溶液中氨氮和磷性能研究

采用氯化钠离子交换和氯氧化锆沉积沉淀两步法改性天然沸石,得到具有脱除水中氨氮和磷的双功能锆钠改性天然沸石（Zr-Na/Zeolite）,考察了不同pH、溶液初始质量浓度和温度下Zr-Na/Zeolite对氨氮溶液、含磷溶液及氮磷共存溶液的吸附情况。结果表明,Zr-Na/Zeolite能够在保持Na改性沸石（Na/Zeolite）优良的吸附氨氮性能的基础上,极大地提高吸附磷的能力。在不同pH下,Zr-Na/Zeolite 吸附氨氮和磷的效果呈现不同的规律。对于氨氮,水溶液pH在4~8时具有最佳吸附性能,最高吸附量达到4.5 mg/g。对于含磷阴离子,脱磷能力随pH的升高而降低,吸附容量从pH=2时的4.71 mg/g降到pH=10时的2.20 mg/g。溶液初始质量浓度从10 mg/L提高到200 mg/L时,氨氮和磷的单位吸附容量分别从1.42和2.46 mg/g提高到11.6和11.8 mg/g,去除率分别从57.0%和98.2%降低到23.2%和23.6%。溶液温度从25 ℃升高到45 ℃,氨氮的吸附容量提高了10%,磷的吸附容量提高了11%。磷和氨氮的吸附过程符合准二级动力学模型。0.1 mol/L NaOH和1.0 mol/L NaCl混合溶液可以再生Zr-Na/Zeolite,循环吸附14次,吸附效率几乎保持不变。     

Low cost adsorbents obtained from ash for copper removal

We investigated the utilization of ash and modified ash as a low-cost adsorbent to remove copper ions from aqueous solutions such as wastewater. Batch experiments were conducted to determine the factors affecting adsorption of copper. The influence of pH, adsorbent dose, initial Cu²⁺ concentration, type of adsorbent and contact time on the adsorption capacity of Cu²⁺ from aqueous solution by the batch adsorption technique using ash and modified ash as a low-cost adsorbent were investigated. The optimum pH required for maximum adsorption was found to be 5. The results from the sorption process showed that the maximum adsorption rate was obtained at 300 mg/L when a different dosage of fly ash was added into the solution, and it can be concluded that decreasing the initial concentration of copper ion is beneficial to the adsorption capacity of the adsorbent. With the increase of pH value, the removal rate increased. When the pH was 5, the removal rate reached the maximum of over 99%. When initial copper content was 300 mg/L and the pH value was 5, the adsorption capacity of the zeolite Z 4 sample reached 27.904 mg/g. The main removal mechanisms were assumed to be the adsorption at the surface of the fly ash together with the precipitation from the solution. The adsorption equilibrium was achieved at pH 5 between 1 and 4 hours in function of type of adsorbent. A dose of 1: 25 g/mL of adsorbent was sufficient for the optimum removal of copper ions. For all synthesized adsorbents the predominant mechanism can be described by pseudo-second order kinetics.     

粉煤灰合成沸石除磷机理研究

利用粉煤灰合成沸石，考察了其对模拟废水中磷酸盐的去除效果，并着重研究了其除磷机理。结果表明，粉煤灰合成沸石有优良的除磷效果，其磷酸吸收系数几乎是原料粉煤灰的4倍，比原料粉煤灰有更高的吸附磷的潜力。粉煤灰合成沸石对磷酸盐的去除机理包括化学沉淀作用和吸附作用，且吸附作用随着平衡溶液的pH值的增大而减弱。粉煤灰合成沸石中沸石成分的骨架结构没有磷吸附作用，粉煤灰只能通过化学沉淀作用去除磷酸盐，粉煤灰合成沸石对磷的吸附作用主要来源于粉煤灰合成沸石过程中产生的无定型非晶体的中间体物质。     

粉煤灰制备高纯度X型沸石及其对含铅废水处理的研究

采用经碱熔融-离心提取处理的粉煤灰为原料,经水热反应法研究合成高纯度X型沸石的过程,探讨了碱灰比、焙烧温度对硅铝熔出量的影响,研究了碱度、陈化时间、晶化时间与硅铝比对合成的影响以及其对含Pb2＋废水的吸附性能。结果表明：碱灰比为2．3∶1,焙烧温度为680℃时可获得最佳的硅铝熔出量;当SiO2／Na2 O＝1（摩尔比）,SiO2／Al2O3＝3．5（摩尔比）,陈化时间为5 h,晶化时间为16 h时可获得高纯度X型沸石。合成沸石表现出对含Pb2＋废水较强的吸附能力,在投加0．23 g／100 mL含Pb2＋500 mg／L溶液中,调节pH值为5,常温下30 min,Pb2＋去除率可达99．6％;吸附容量达到了216．8 mg／g。     

不同钙含量粉煤灰合成沸石对污水中磷的去除

进行了以不同钙含量的粉煤灰为原料合成的3种沸石对污水中磷去除的试验，探讨了表面交换性阳离子种类、投加量以及磷浓度对除磷的影响。结果表明：最佳投加量为8g／L，磷去除率可达到70％以上合成沸石除磷能力均高于粉煤灰，钙饱和处理又可明显进一步提高粉煤灰合成沸石的除磷效果。粉煤灰合成沸石钙含量越高，对磷的去除率越高。因此，采用高钙粉煤灰为原料合成沸石并进行钙饱和处理，可以获得除磷能力强的合成沸石材料。     

利用粉煤灰制备分子筛及对水体中六价铬的吸附研究

以粉煤灰为原料,采用湿法加碱煅烧法合成了4A分子筛,研究了粉煤灰与烧碱配比、煅烧温度、煅烧时间对合成4A分子筛的影响,结果表明粉煤灰与烧碱配比1.0:0.8,煅烧温度700℃,煅烧时间1 h有利于4A分子筛的合成.利用合成的4A分子筛对水体中六价铬进行了吸附研究,实验确定的最佳吸附条件为:分子筛投加量为0.3 g,溶液pH值为6～7,吸附时间为30 min,吸附温度为10～25℃.最佳吸附条件下分子筛对六价铬有较好的去除效果.吸附以物理吸附为主,符合Freundlich等温吸附式.同时对4A分子筛的再生性进行了研究,2次循环使用后其吸附能力仍能保持初次吸附能力的90.0％以上.     

Preparation and Application of a Novel Functionalized Coconut Coir Pith as a Recyclable Adsorbent for Phosphate Removal

Abstract

This study was to develop a new adsorbent, Iron(III) complex of an amino-functionalized polyacrylamide-grafted coconut coir pith (CP), a lignocellulosic residue, for the removal of phosphate from water and wastewater. The kinetics of adsorption follows a pseudo-second-order model. The equilibrium sorption capacity of 96.31 mg/g was determined at 30°C from the Langmuir isotherm equation. Complete removal of 16.4 mg/L phosphate in 1 L of fertilizer industry wastewater was achieved by 1.5 g/L AM-Fe-PGCP at pH 6.0. The acid treatment (0.1 M HCl) and re-introduction of Fe³⁺ lead to a reactivation of the spent adsorbent and can be reused through many cycles of water treatment and regeneration without any loss in the adsorption capacity.     

Zeolite X/chitosan hybrid microspheres and their adsorption properties for Cu(II) ions in aqueous solutions

The preparation of zeolite X/chitosan (CS) hybrid microspheres for efficient removal of Cu(II) ions by an impregnation-gelation-hydrothermal synthesis technique is reported here. Characterizations by various techniques indicate that the microspheres show porous structures and intimate interaction between zeolite and CS. The adsorption experiments are performed to evaluate the adsorption capacity of zeolite X/CS hybrid microspheres and comparisons are made with binderless zeolite X microspheres, pure CS microspheres and mechanical mixed zeolite X/CS microspheres. The effects of Cu(II) solution concentration and the pH are investigated. The results indicate that zeolite X/CS hybrid microspheres with the zeolite content of 60 wt% show the highest adsorption capacity, which is 90 mg/g at the initial Cu(II) concentration of 10 mg/L and 150.4 mg/g at Cu(II) concentration of 500 mg/L. The adsorption capacity increases with increasing initial pH and reaches a maximum at pH 5.5 in the range of 0–6.0. The equilibrium adsorption data are well described by the Langmuir isotherm model, exhibiting a maximum adsorption capacity of 152.0 mg/g, and the kinetic data are well fitted with the pseudo-second-order equation. Complete removal of Cu(II) ions can be obtained even at very low concentrations. The microspheres show high adsorption capacity and efficiency for Cu(II) ions, exhibiting potential practical application in the treatment of water pollution of heavy metal ions.     

Removal of victoria blue from aqueous solution by fly ash

The use of fly ash for the removal of victoria blue (C126, 44045) from aqueous solution at different concentrations and pH has been investigated. The process follows first order adsorption rate expression and the rate constant was found to be 1.70 × 10^?2 min^?1 at a victoria blue concentration of 1.0 × 10^?4 M and 25°C. The uptake of victoria blue by fly ash is diffusion controlled and the value of mass transfer coefficient is 1.25 × 10^?5 cm sec^?1. The equilibrium data fit well in the Langmuir model of adsorption. Maximum removal was noted at pH 8.0. Low desorption of dye from adsorbent surface indicates that the process may not be essentially a reversible one.     

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.     

The use of fly ash from the combustion of poultry litter for the adsorption of chromium(III) from aqueous solution

Fly ash, from the combustion of poultry litter, was assessed as an adsorbent for chromium(III) from aqueous solution. The adsorption process was studied as a function of temperature and time. Adsorption was best described by the Langmuir model. The adsorption of chromium(III) on the fly ash was endothermic and kinetic studies suggest that the overall rate of adsorption was pseudo‐second order. At low initial concentrations film diffusion effects contribute to limiting the overall rate of adsorption while at higher initial chromium(III) concentrations pore diffusion becomes more important. An adsorption capacity of 53 mg dm^?3 was reached at 20 °C. © 2002 Society of Chemical Industry     

由飞灰合成的沸石吸附废水中染料的动态平衡

The removal performance of a basic dye, methylene blue (MB), in aqueous solution was investigated by adsorption process on single-phase and high-crystalline zeolite A (FA-ZA) and X (FA-ZX). Both adsorbents FA-ZA and FA-ZX were synthesized from fly ash prepared aluminosilicate gel followed by the hydrothermal treatment at 100°C with the control of Si/Al molar ratio, respectively. The properties of the synthetic zeolites and commercial grade zeolites, such as thermal stability, elemental composition, and cation exchange capacity, were investigated for comparison. Batch method was used to study the influential parameters, such as initial pH value of the solution, temperatures, and adsorbents dosage, on the adsorption process. The experimental data were well fitted by Ho’ pseudo-second-order model and liquid film diffusion model. The suitability of Langmuir and Freundlich isotherms to the equilibrium data was investigated in the solid-liquid system while the Langmuir model produces the best re-sults. Thermodynamic data (ΔH, ΔS, and ΔG) corresponding to the MB uptake were evaluated from the Langmuir model. In all the adsorption experiments, the adsorption capacity followed the order as follows: FA-ZX > FA-ZA. In addition, attempts were also made to regenerate the adsorbents.     

煤灰基沸石电场辅助吸附Ni^2+研究

以热电厂固体废弃物粉煤灰为原料合成了1种高效的Ni^2+沸石吸附剂,研究了在电场辅助作用下,电场强度、溶液pH和电解质NaCl含量对沸石吸附Ni^2+性能的影响。结果表明,当电场强度为0.8 V/cm,NaCl的质量浓度为1 g/L,溶液pH为6时,阴极室中沸石对Ni^2+的吸附量可达到64.44 mg/g,比开路时提高了53.17%,饱和吸附时间缩短了50%。吸附剂经过5次循环使用后,Ni^2+饱和吸附量仍保持原来的94.49%,具有较好的稳定性、吸附/解吸附和再生性。辅助电场不仅可以附加Ni^2+的电迁移作用,还可以对沸石吸附剂产生扩孔作用,增大其比表面积,进而提高沸石的Ni^2+吸附性能。     

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.     

Chemical modification of coal fly ash for the removal of phosphate from aqueous solution

This study investigated the chemical modifications of coal fly ash treated with HCl and NaOH. Sorption behavior of phosphate from water solution on treated fly ash was examined. Results showed that the HCl-treated fly ash (TFA-HCl) had a greater specific surface area (SSA) than the NaOH-treated fly ash (TFA-NaOH) and untreated fly ash (FA). The XRF, XRD patterns, and SEM images revealed the decreased CaO content in the TFA-HCl and observed the presence of NaP1 and sodalite zeolites in the TFA-NaOH. The P sorption capacity of all studied fly ashes increased with increasing initial P concentration and mechanisms of P sorption were influenced by the equilibrium pH. Maximum phosphate immobilization capacity obtained from Langmuir model was in the following manner, TFA-NaOH > FA > TFA-HCl (57.14, 23.20, and 6.90 mg P g⁻¹, respectively). The decreased CaO content and acidic pH in the TFA-HCl were responsible for the lowest capacity of phosphate immobilization, because of unfavorable condition for calcium phosphate precipitation. In contrast, due to alkaline condition and relatively high calcium content, the precipitation of calcium phosphate was a key mechanism for phosphate removal in the FA and TFA-NaOH. The TFA-NaOH had a greatest phosphate immobilization, due to high CaO content and an increased SSA after the conversion of fly ash to zeolite. Both Langmuir and Freundlich models were good fitted for the TFA-NaOH, while was only Langmuir model for the FA and Freundlich model for the TFA-HCl. Results suggested that treating fly ash with alkaline solution was a promising way to enhance phosphate immobilization.     

Preparation of Na‐P1‐Type Zeolite and its Composite Material with Nanosized Magnetite

The Na‐P1‐type zeolite having a high cation‐exchange capacity (CEC) was obtained using the waste coal fly ash from thermal power stations and a 2M NaOH solution at 100°C. The Na‐P1‐type zeolite was formed with the reaction time of 6 h at 100°C, and its CEC value increased with an increase in the reaction time. The addition of a suitable amount of NaAlO₂ to the fly ash was also effective for improving the CEC value. A new composite material consisting of the Na‐P1‐type zeolite and magnetite was synthesized from the fly ash and iron chlorides because the magnetic collection was possible using this composite material after radioactive Cs⁺ ion adsorption. The existence of nanosized magnetites in the polycrystalline zeolite (several micrometers) was confirmed by TEM observations. The CEC and magnetic property of these composite materials were characterized.     

Evaluation of Phosphate Removal Efficiency from Aqueous Solution by Polypyrrole/BOF Slag Nanocomposite

The polypyrrole/basic oxygen furnace slag nanocomposite (PPy–BOFS) was synthesized and characterized by FTIR, SEM, ICP-AES, and X-ray diffraction studies and was employed as an adsorbent for the removal of phosphate ions from aqueous solution by the batch sorption method. The maximal amount of adsorption was found to be 9.13 mg/g (45°C). The Langmuir and Freundlich isotherms were used to describe the adsorption equilibrium. The kinetics of the adsorption process was investigated using the Lagergren rate equation and the Weber Morris intraparticle diffusion model. The FTIR and XRD pattern of the adsorbent before and after the adsorption was recorded to get better insight into the mechanism of the adsorption process. The results of equilibrium and spectral investigations revealed that the removal of phosphate by the nanocomposite involves various mechanisms followed by the nanocomposite and the constituents present in it.     

Adsorption Behavior of Methylene Blue from Aqueous Solution by the Hydrogel Composites Based on Attapulgite

A series of carboxymethyl cellulose-g-poly (acrylic acid)/attapulgite hydrogel composites were synthesized for the removal of cationic dye methylene blue. Various factors affecting the uptake behavior were investigated. Adsorption rate of the hydrogel was quite fast, and adsorption equilibrium could be reached within 30 min. Adsorption kinetics well followed the pseudo-second-order equation for all systems. The Langmuir isotherm was found to best represent the data for the dye uptake. Even when 20 wt% attapulgite was introduced into the hydrogel, the corresponding maximum adsorption capacity reached 1979.48 mg/g at 30°C. The as-prepared adsorbents exhibited excellent affinity for the dye, and can be applied to treat wastewater containing basic dyes.