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.     

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。     

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.     

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.     

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。     

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.     

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.     

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。     

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。     

粉煤灰沸石的合成及其对Pb~（2＋）的吸附研究

以驻马店热电厂粉煤灰为原料,在水热条件下合成了沸石,利用FT-IR对合成沸石进行表征。利用正交试验法研究了所合成沸石吸附Pb2＋的性能,考察了粉煤灰预处理方法、吸附条件（pH值、吸附时间、沸石用量等）对吸附的影响。结果表明：采用加碱焙烧预处理合成的沸石,在pH=7、吸附时间45 min、投加量为1.2 g时,对Pb2＋有很好的吸附作用。该条件下Pb2＋的去除率在83.5%左右。     

改性粉煤灰处理模拟含酚废水的实验研究

通过对粉煤灰进行改性,研究其对模拟含酚废水中苯酚去除效果.探讨了pH、吸附时间、投加量、吸附温度及水样中苯酚初始浓度对粉煤灰去除苯酚效果的影响.实验表明,选用碱改性的粉煤灰,投加15g/L处理苯酚质量浓度30.0 mg/L的模拟含酚废水,当吸附时间为30 min,pH为6～7时,对苯酚去除率达98％,吸附等温线拟合结果...     

Kinetics and equilibrium studies of removal of an azo dye from aqueous solution by adsorption onto scallop

In the present work removal of an azo dye (Reactive Black 5) was investigated from aqueous solution by adsorption onto scallop as a low-cost and widely available adsorbent. The effect of various operational parameters, such as contact time, pH, initial dye concentration and adsorbent dosage on the removal efficiency of dye was studied. Removal efficiency declined with the increase in solution pH and initial dye concentration but with the decrease in adsorbent dosage. Experimental equilibrium and kinetics data were fitted by Langmuir and Freundlich isotherms and pseudo-first-order and pseudo-second-order kinetic models, respectively.     

油页岩灰渣合成Na-A沸石用于去除水溶液中Cu2+（英文）

Na-A zeolite was synthesized using oil shale ash （OSA）, which is a solid by-product of oil shale proc- essing. The samples were characterized by various techniques, such as scanning electron microscopy, X-ray diffrac- tion and Brunaner Emmet Teller method. The batch isothermal equilibrium adsorption experiments were performed to evaluate the ability of Na-A zeolite for removal of Cu （II） from aqueous solutions. The effects of operating pa- rameters, such as concentration of copper solutions, adsorbent dosages, pH value of solutions and temperature, on the adsorption efficiency were investigated. The equilibrium adsorption data were fitted with Langmuir and Freundlich models. The maximum adsorption capacity of Na-A zeolite obtained from the Langmuir adsorption iso- therm is 156.7 mg.g-t of Cu （lI）. The increase of pH level in the adsorption process suggests that the uptake of heavy metals on the zeolite follows an ion exchange mechanism. The batch kinetic data fit the pseudo-second order equation well. The thermodynamic parameters, such as changes in Gibbs free energy （AG）, enthalpy （AH） and en- tropy （AS）, are used to predict the nature of the adsorption process. The negative AG values at different tempera- tures confirm that the adsorption processes are spontaneous.     

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.     

The removal of phosphate ions from aqueous solution by fly ash, slag, ordinary Portland cement and related blends

Phosphate ions have been removed from aqueous solution by fly ash, slag, ordinary Portland cement (OPC) and related cement blends. The rate and efficiency of PO₄³⁻ removal were found to increase in the order: fly ash, slag, OPC, apparently mimicking the order of increasing percent CaO in the adsorbents. Blending OPC with fly ash or slag evidently results in diminished PO₄³⁻ removal efficiency. Better removal was obtained at higher solute concentration, acidic pH and higher temperature. The effect of particle size and the speed of mixing were found not to be significant. A first-order kinetic model was used to obtain values for overall sorption rate constants and intraparticle diffusion constants. The Frumkin isotherm was found to be the appropriate equation for modelling isotherms from the experimental adsorption data, and values have been obtained for the isotherm constants. A 400-mg/l PO₄³⁻ (as P) solution was fed at a steady velocity of 2.0 cm/min through a 2.0-cm fixed-bed column (at pH 9.0 and 25 °C), and breakthrough curves were constructed to obtain estimated adsorption capacity values of 32, 60, 75, 78 and 83 mg PO₄³⁻/g adsorbent for fly ash, slag, OPC+fly ash, OPC+slag and OPC, respectively.     

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。     

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.     

粉煤灰合成沸石对Cr3＋的吸附性能研究

利用粉煤灰合成沸石吸附重金属Cr3＋,探讨吸附剂量、初始pH值以及反应温度对Cr3＋吸附效果的影响,同时进行吸附等温线和吸附动力学的数据模拟。结果表明：沸石投加量、初始pH值以及反应温度均对Cr3＋的去除效果影响显著。随着吸附剂投加量的不断增大,Cr3＋去除效果不断提高,饱和吸附量逐渐减小。初始pH值为4时沸石吸附Cr3＋的去除率为100％。反应温度的上升不利于沸石对Cr3＋吸附,沸石对Cr3＋的吸附效果随着反应温度的升高逐渐降低。沸石吸附Cr3＋的过程符合Freundlich吸附等温式;准二级反应动力学方程能较好描述沸石对Cr3＋的吸附行为。     

Removal of Metanil Yellow from its Aqueous Solution by Fly Ash and Activated Carbon Produced from Different Sources

Abstract

The present study has been undertaken to observe the relative efficiency of removal of metanil yellow from its aqueous solution by using different adsorbents like fly ash and activated carbon produced from different sources i.e. coconut shell, mehagani saw dust, and rice husk. It has also been observed that the rate of adsorption is highly dependent on contact time, adsorbent dose, pH, and initial concentration of the dyestuff. Rate of removal has been observed to increase with increasing contact time and adsorbent dose but with decreasing initial concentration. Higher removal has been observed generally in acidic range. Adsorptions by the adsorbents under investigation follow the Freundlich and Langmuir isotherm models where Freundlich and Langmuir constants have also been determined at different temperatures. Isotherms have been used to obtain the thermodynamic parameters like free energy, enthalpy and entropy of adsorption. Kinetic studies showed that all the adsorbents follow first order adsorption rate model with respect to the dye solution concentration. Various kinetic parameters such as first order adsorption rate constant, mass‐transfer co‐efficient, pore‐diffusion constant, and activation energy of adsorption were evaluated to establish the mechanism. Adsorption processes were found to be endothermic, spontaneous, and pore‐diffusion controlled for all the adsorbents. Among the adsorbents used in this study, activated carbon produced from mehagani saw dust has been found to be the most effective, which remove almost 100% metanil yellow from its 1000 ppm aqueous solution.     

Removal of methylene blue dye from aqueous solutions by a new chitosan/zeolite composite from shrimp waste: Kinetic and equilibrium study

The adsorption of methylene blue dye (MBD) from aqueous solutions was investigated using a new composite made up of shrimp waste chitosan and zeolite as adsorbent. Response surface methodology (RSM) was used to optimize the effects of process variables, such as contact time, pH, adsorbent dose and initial MBD concentration on dye removal. The results showed that optimum conditions for removal of MBD were adsorbent dose of 2.5 g/L and pH of 9.0, and initial MBD concentration of 43.75 mg/L and contact time of 138.65 min. The initial concentration of dye had the greatest influence on MBD adsorption among other variables. The experimental data were well fitted by the pseudo-second order kinetic model, while the Freundlich isotherm model indicated a good ability for describing equilibrium data. According to this isotherm model, maximum adsorption capacity of the composite was 24.5 mg/g. Desorption studies showed that the desorption process is favored at low pH under acidic conditions.