Ammonium removal by modified zeolite from municipal wastewater

Ammonium removal by modified zeolite, H-form and Na-form zeolite, were examined by batch-type methods. The adsorption of ammonium on modified zeolite was exothermic process. The saturation adsorption capacity of ammonium on H-form and Na-form zeolite were 21.23 and 41.15 mg/g, respectively. After ten times adsorption-desorption-readsorption cycles the standard deviations of H-form and Na-form zeolite were 6.34% and 6.59%. The zeolite adsorption process has proved cost effective and practical in reducing ammonium by H-form and Na-form zeolite in municipal wastewater from concentration 27.68 mg/L to 2.80 mg/L and 5.91 mg/L.

Ammonia nitrogen removal from aqueous solution using zeolite modified by microwave-sodium acetate

The characteristics of the zeolite modified by microwave and sodium acetate and its sorption of ammonia-nitrogen from simulated water sample were investigated.The results show that the modified zeolite by microwave-sodium acetate(SMMZ)has a high sorption efficiency and removal performance.The ammonia-nitrogen removal rate of SMMZ reaches 92.90%.The surface of SMMZ becomes loose and some pores appear,the specific surface area,total pore volume and average pore diameter increase after modification.Compared to the natural zeolite,SMMZ has a more concentrated pore size distribution in the range of 0-10 nm.The cation exchange capacity(CEC)of SMMZ is higher than that of the natural zeolite.And the ammonia nitrogen removal rate is consistent with the change of CEC.The SMMZ possesses rapid sorption and slow balance characteristics and ammonia-nitrogen sorption is consistent with both Langmuir adsorption isotherm model and Freundlich adsorption isotherm model.The adsorption kinetics of ammonia-nitrogen follows the pseudo-second order kinetic model.

Removal of Fulvic Acids from Aqueous Solutions via Surfactant Modified Zeolite

A surfactant modified zeolite（ SMZ）, i. e. , a zeolite modified by using hexadecyl trimethyl ammonium bromide （HDTMA） was used to remove fulvic acids（FA） from aqueous solution. The effects of the relevant parameters, such as the loading level of HDTMA, the contact time, the initial FA concentration, the pH, and the types of the metal carious and organics were examined. The results show that SMZ with an HDTMA loading-level of 120% of the external cation exchange capacity（ECEC） of zeolite exhibits the best performance. Although the removal of fulvic acids by SMZ occurs rapidly within the first 30 min of the contact time, a contact time of at least 4 h is required to attain the adsorption equilibrium. The removal capacity of FA by SMZ decreases with the increase of the initial FA concentration. The pH has an effect on the FA removal efficiency because it can influence the characteristics of the FA molecules. The removal of FA is considerably enhanced by Ca^2＋ or Mg^2＋ ions and is adversely affected by phenol or pentachlorophenol（PCP）. Under the optimum conditions, 98% of FA could be removed by SMZ. Furthermore, the desorption of FA and the regeneration of SMZ were studied. The results show that a 30% ethanol solution is sufficient for the regeneration of SMZ.

Improved Stability and Shape Selectivity of 2,6-Dimethylnaphthalene by Methylation of Naphthalene with Methanol on Modified Zeolites

2,6-Dimethylnaphthalene (2,6-DMN) is a key intermediate for polyethylene naphthalate synthesis. The selective synthesis of 2,6-DMN from naphthalene and methanol was carried out over different zeolites (HZSM-5, Hβ, HUSY and SAPO-11) modified by 0.1wt% PdO under atmospheric pressure. Among the adopted zeolites, SAPO-11 exhibits exceptional shape-selectivity and stability to synthesize 2,6-dimethylnaphthalene from methylation of naphthalene, due to the special pore structure of SAPO-11 which inosculated better with 2,6-dimethylnaphthalene than with 2,7-dimethylnaphthalene.

Preparation of Calcium Cross-linked Nano-Fe3O4 Modified Zeolite Microspheres for Cu^2+ Adsorption from Wastewater

Artificial zeolite was modified by nano-Fe3O4 for development of functional adsorbents.Subsequently,adsorbents such as calcium cross-linked nano-Fe3O4 microspheres (Ca-MS),calcium cross-linked nano-Fe3O4 modified zeolite microspheres (Ca-MZS) and iron cross-linked nano-Fe3O4 modified zeolite microspheres (Fe-MZS) were prepared and compared for their adsorption performance.The effects of adsorbent dosage,solution pH,initial concentration and ion content on the removal of Cu^2+ from wastewater are investigated,and the adsorption kinetics and isotherms for the adsorbent materials were analyzed.The experimental results indicate that for the initial concentration of Cu^2+ of 30 mg/L,the adsorption is noted to be most stable.The optimal initial pH for adsorbing Cu^2+ is observed to be 5.5.At an optimal dosage of Ca-MZS of 900 mg/L,the adsorption capacity is measured to be 28.25 mg/g,along with the removal rate of 72.49%.The addition of Na+ and K+ affects the adsorption of Cu^2+.For the Na^+ and K^+ concentration of 0.2 mmol/L,the Cu^2+ removal rate by Ca-MZS drops to 11.94% and 22.12%,respectively.As compared with the adsorbents such as Natural Zeolite (NZ),Ca-MS and Fe-MZS,Ca-MZS demonstrates the best removal effect in solution,where the removal rate reaches 84.27%,with the maximum adsorption capacity of 28.09 mg/g.The Cu^2+ adsorption kinetics of Ca-MZS is observed to follow the Elovich kinetic model,with the adsorption isotherm data fitting the Freundlich isotherm model by using the non-linear method.

Effects of Modified Zeolite on Adsorption and Desorption of Phosphorus

The influence of natural and modified zeolite on the adsorption and desorption characteristics of phosphorus was studied. The results show that the adsorption isotherm of natural and modified zeolite to phosphorus is conformed to the Langmuir, Freundlich and Temkin equations. As for natural zeolite, the correlation coefficient of Freundlich equation is the highest. The adsorption or desorption capacity order of six kinds of zeolite to phosphorus is H-zeolite 〉 Ba-zeolite 〉 Mg-zeolite 〉 Ca-zeolite 〉 natural zeolite 〉 K-zeolite. The desorption ratio order of natural and modified zeolite is K-zeolite 〉 Ba-zeolite 〉 Mg-zeolite 〉 Ca-zeolite 〉 natural zeolite 〉 H-zeolite. It is thus clear that Ba-zeoUte, Mg-zeolite and Ca-zeolite can not only enhance the adsorption capacity to phosphorus, but also increase the desorption ratio to phosphorus. It shows that Ba-zeolite, Mg- zeolite and Ca-zeolite have the strong ability to supply and retain phosphorus. In comparison to others, the adsorption capacity of K-zeolite to phos- phorus is the lowest, but the desorption ratio is the highest, indicating that applying K-zeolite in soil can not reduce the availability of phosphorus. Therefore, modified zeolite has a broad application prospect in the agricultural production, especially in soil amendment.

Adsorption of Naphthalene on Modified Zeolite from Aqueous Solution

In this study, the modified zeolite with certain hydrophobicity was prepared by modifying natural zeolite by the silane coupling agents such as vinyltrimethoxysilane (VTMO), trimethoxysilane (TMS) and trimethylchlorosilane (TMCS). The modified zeolite has a higher hydrophobicity and adsorption capacity than natural zeolite while ensuring the advantages of natural zeolite, which is more conducive to the adsorption of organic pollutants from aqueous solution. The adsorption experiment on naphthalene in aqueous solution shows that the modified zeolite has a stronger adsorption capacity. In the adsorption thermodynamics experiment, the isothermal adsorption models such as Freundlich and Langmuir can better describe the adsorption of naphthalene on modified zeolite, but the isothermal adsorption model Freundlich has a higher correlation. At 303K, the static adsorption capacity is 339μg/g. The kinetic analysis shows that the adsorption of naphthalene on modified zeolite conforms to the quasi-second order kinetic model.

Studies on Zeolite Modified Electrode(Ⅰ)─Ascorbic Acid Sensor Based on Carbon Paste Electrode Containing Fe(Ⅲ)Y Zeolite

A new ascorbic acid sensor constituted of carbon paste and Fe(Ⅲ)Y zeolite was studied.The characters of the sensor such as linear range. potential window、apparen Michaelis constant、response time、stability and accuracy wee investigated. The experimental results indicate that the analytical performance of the sensor is satisfactory.

Acidity Evaluation of Industrially Dealuminated Y Zeolite via Methylcyclohexane Transformation

The catalytic transformation of methylcyclohexane as an accepted probe reaction to evaluate zeolitic acidity(concentration,strength,and accessibility)is employed to study the acidity and the reactivity of three commercial dealuminated Y zeolites(DAY)with different Si/Al ratios and meso/microporosities,with their properties analyzed by N_(2) adsorption/desorption,pyridine-IR,and hydroxyl-IR spectroscopy technologies.The global activity(conversion)is largely dependent on the concentration of the acid sites,and the activity of the protonic sites in terms of turnover frequency(TOF)reflects the accessibility of acid sites.The products of aromatics and isomers,and the yield of cracking products increase with the increase of concentration of strong protonic sites in zeolite micropores.Moreover,the decrease of aromatics with the reduction of the concentration of acid sites and the diffusion length within DAY zeolites are observed due to the decrease of the secondary reaction.For the same reason,it results in the increasing of C_(7)products and alkenes/alkanes ratios in the cracking products.The high i-C_(4)product selectivity is a unique reflection of the high percentage of very strong acid sites,which is characterized by the hydroxyl-IR band at 3600 cm^(-1).

Effect of the pH on the Cr(VI)Sorption on HDTMA-zeolites

The uptake of Cr(VI)from aqueous solutions was investigated using clinoptilolite and phillipsite rich tuffs.These minerals were modified using hexadecyltrimethyl-ammonium bromide(HDTMA-Br)and used for Cr(VI)ions removal.The physicochemical characteristics of zeolitic minerals were revealed by XRD,XRF,BET and FT-IR techniques.The concentration of Cr(VI)working solutions,Cinit ranged between 5-100 mg·L-1,were prepared by dilution of the stock solution with distilled water with pHinit adjusted to the value of 3.0 or 4.0 or 5.0.The residual concentrations of chromium in the liquid samples were analyzed by ICP-OES.The uptake capacities of modified zeolites were compared in batch sorption experiments.The comparison of the obtained data identified that efficiency of Cr(VI)sorption onto clinoptilolite is always higher than in phillipsite case.The analysis of the infrared spectra revealed that after adsorption of Cr(VI)the characteristics for HDTMA vibrations were shifted in PHI-HDTMA case,while for CLI-HDTMA the intensity of characteristics peaks decreased.

EC130温拌剂对SBS改性沥青高温性能及抗疲劳性能的影响

作为制备沸石发泡沥青的发泡剂,EC130温拌剂释放的发泡水和残留的沸石矿物对沥青的性能有着不同的影响.为研究EC130温拌剂对SBS改性沥青高温性能和抗疲劳性能的影响,采用石灰岩矿粉、EC130沸石矿物和EC130温拌剂等3种添加物,设计了以添加物掺量为变量的单因素试验.以石灰岩矿粉为参照对象,通过温度扫描试验、多重应力蠕变恢复试验和线性振幅扫描试验,分析了EC130沸石矿物和EC130温拌剂释放的发泡水对SBS改性沥青高温性能和抗疲劳性能的影响.结果表明:同石灰岩矿粉一样,沸石发泡沥青中的EC130沸石矿物使沥青弹性增大、黏性减小,有利于抗车辙性能的提升,但不利于抗疲劳性能;沸石发泡沥青中的发泡水使其黏性增大、弹性减小,有利于抗疲劳性能的提升,但不利于抗车辙性能.

Aspha-Min沸石对SBS改性沥青-填料交互作用的影响

沸石作为制备泡沫沥青温拌混合料的发泡剂,其释放的沸石水和残留的沸石矿物对沥青-填料交互作用有着不同影响.通过流变学试验,研究了沸石、沸石矿物和沸石水对SBS改性沥青及其胶浆流变特性的影响.试验发现,在沥青或胶浆中添加沸石或沸石矿物可使其弹性增大,且随其掺量的增加而增大,沸石水则与之相反.进一步,利用基于流变特性的交互作用评价指标[η]、Palierne-C-G*和Luis Ibrarra-A-δ,研究了沸石、沸石矿物和沸石水对SBS改性沥青-填料交互作用的影响.研究表明,胶浆中添加沸石或沸石矿物可使沥青-填料交互作用增大,且随其掺量的增加而增大,沸石水则与之相反.

改性沸石去除地下水中铁锰的研究进展

根据沸石的结构特征并利用沸石进行除铁锰的动力学机理总结了影响其除铁锰性能的材料自身的因素,综述了对沸石进行改性的方法以及改性前后的对比,其中包括在合成过程中在保证沸石基本框架的前提下,对影响沸石合成的因素,即硅铝比、杂质去除、碱度、结晶温度、晶化时间、导向剂的人为控制调节,以及进行微波、高温、涂层、化学药剂浸泡的预处理改性。为改性沸石后续研究提出参考和建议。

铜、铈离子交换顺序对Y型分子筛吸附脱除苯中噻吩性能的影响

【目的】利用双金属改性Y型分子筛对焦化苯中的噻吩进行深度脱除具有重要的意义。其中,金属离子交换顺序对分子筛脱硫性能的影响至关重要。【方法】采用Cu、Ce双金属,利用离子交换法制备出系列双金属改性吸附剂,采用静态吸附实验评价了吸附剂对苯中噻吩的脱除性能,并通过XRD、Py-FTIR、XPS、H2-TPR和N2吸脱附等手段表征了吸附剂的物化性质。【结果】结果表明,金属离子交换顺序会影响吸附剂的相对结晶度、离子交换度、金属含量以及L酸酸量。吸附剂的物化性质与脱硫性能进行关联发现,离子交换度越大,吸附剂的脱硫效率越高;同时吸附剂中Cu^(+)和Ce^(4+)含量越高,形成更多的L酸,其脱硫效率越高。利用双金属对Y型分子筛改性,先Ce后Cu进行交换时,金属Ce会对Cu的落位产生影响,Ce提高了Cu的还原性能。3种吸附剂脱硫效率由大到小为:CuCeY,CeCuY,Cu-CeY.CuCeY吸附剂的脱硫效率最高,可达97.3%,且其相对结晶度最高,离子交换度最大。此工作为高效脱硫吸附剂的制备起到了指导作用。

Ce改性HZSM-5分子筛催化甲醇与丁烯耦合转化制丙烯性能研究

为了进一步提高HZSM-5分子筛在甲醇与丁烯耦合转化制丙烯反应中的催化性能,采用浸渍法对HZSM-5分子筛进行Ce改性,得到了一系列具有不同Ce负载量的x Ce/HZSM-5催化剂。考察了Ce负载量和反应条件(甲醇与丁烯物质的量之比、反应温度和空时)对催化性能的影响,并结合催化剂表征结果,分析了Ce改性对催化性能和物化性质的影响,探讨了x Ce/HZSM-5催化剂的构效关系。结果表明,在温度550℃、压力0.1 MPa、甲醇与丁烯物质的量之比0.8、空时2.3(g cat·h)mol CH_(2)的最佳反应条件下,Ce负载量(w)为2.5%的2.5Ce HZSM-5催化剂具有最高的丙烯收率,为41.9%。Ce与HZSM-5分子筛上羟基官能团(OH)发生相互作用,降低了B酸酸量,同时生成新的L酸中心Ce(OH)^(2+),调变了催化剂表面酸中心密度和酸类型分布,提高了丙烯选择性和收率。

强化混凝耦合改性沸石过滤处理微污染水

针对南方某市微污染水源水(XJ)低温低浊及氨氮问题,采用烧杯实验及中试动态运行实验进行复合助凝剂强化混凝耦合改性沸石过滤处理低温低浊及氨氮效能研究。结果表明,配置的Fe/Si复合助凝剂在絮凝初期投加时明显提高了低温低浊水的出水水质。复合助凝剂的存在起到良好的吸附架桥作用,提高混凝效果。强化混凝对氨氮去除作用有限,不足10%。改性沸石颗粒(MZK)能够利用离子交换和化学吸附作用显著提高氨氮去除效果,去除率达到83.1%。在连续中试动态运行中,出水浊度基本控制在0.6 NTU;在240 h的运行周期内,MZK对氨氮的去除效果明显优于石英砂,氨氮的平均去除率为77.6%,出水处氨氮浓度均小于0.5 mg/L。强化混凝耦合改性沸石过滤为低温低浊及氨氮的水处理提供了理论基础和技术参考,具有较好的应用前景和推广价值。

沸石膜在分离烟气中CO_(2)的挑战:沸石与载体间结合力研究进展

发电厂烟气中CO_(2)是主要碳排放源之一,利用沸石膜孔径大小进行CO_(2)分离则是实现碳中和、降低碳排放的重要手段。然而,在高温高压气体环境下使用沸石膜分离烟气时,沸石与载体结合并不紧密,易导致膜层在分离烟气过程中破裂或与载体发生剥离,为沸石膜大规模分离CO_(2)提出挑战。综述了沸石与载体之间的结合方式以及结合力特性,并对定量表征结合力强弱的方法进行归纳、总结。结果表明,Decadodecasil 3R(DD3R)沸石具有全硅结构及介于CO_(2)/N_(2)分子大小的孔隙尺寸,可与经过酸处理的陶瓷载体形成相对稳固的共价键,从而形成结合紧密的沸石膜。即使在水蒸气影响下,该膜仍能有效实现烟气中CO_(2)/N_(2)分离;传统试验方法(如超声法、划痕法和压痕法)在研究载体、沸石和改性剂界面的结合力时无法提供详细数据,分子模拟能有效弥补这些不足,在原子尺度上模拟材料界面的结合情况并进行量化,从而为筛选最优的载体改性方法提供了坚实的理论基础。

改性沸石/聚合氯化铝造粒复合材料对水中氨氮和磷的吸附性能研究

以改性沸石(MZ)和聚合氯化铝(PAC)为原料,添加粘结剂聚乙烯醇(PVA)和造孔剂碳酸氢钠(NaHCO_(3)),制备出可同步脱氮除磷的复合颗粒材料(MZP),并探究了投加量和pH等因素对氨氮和磷吸附性能的影响。结果表明,在MZP投加量为7 g/L,pH为6~8条件下,MZP对氨氮和磷的去除率均高于84%。MZP对氨氮和磷的吸附符合Freundlich吸附等温线模型,且吸附过程受液膜扩散和颗粒内扩散共同控制,符合准二级动力学模型,吸附过程MZP对氨氮和磷的最大理论吸附量分别为5.92、2.25 mg/g。共存离子对MZP吸附氨氮和磷有一定影响。经过5次吸附-解吸再生循环利用后,MZP仍能保持74%的氨氮去除率和52.6%的磷去除率。结合材料表征分析结果,MZP对氨氮的吸附主要为离子交换,对磷的吸附主要为静电吸附和配体交换。

NaCl改性沸石充释氧性能及对黑臭水体中氨氮去除效能研究

基于天然沸石的多孔性能和对氨氮具有良好的选择吸附特性,利用NaCl对其进行改性,研究其载氧、锁氧和缓释氧能力,并以模拟黑臭水体为对象,研究初始氨氮浓度、温度、pH等条件对改性沸石吸附氨氮能力的影响。结果表明,1.0 mol/L NaCl改性天然沸石可将模拟黑臭废水中溶解氧浓度从0.2 mg/L提高到7.2 mg/L,并保持数周,说明改性沸石具有锁氧功能,并且氧的缓释效果明显,有利于持续较长时间的水处理过程;在改性沸石材料投加量为10 g/L,pH为7,温度为25℃,初始浓度为30 mg/L的条件下对氨氮的去除率可达91.0%,表明改性沸石对改善高氨氮水质具有显著而高效的作用。

基于硝酸钠联合焙烧改性天然沸石的水体氨氮动态吸附特性研究

目的:通过硝酸钠浸渍联合焙烧改性天然沸石(NZ),开发出一种氨氮高性能吸附剂,研究改性NZ对水体中氨氮的动态吸附特性及穿透曲线,并与NZ的氨氮动态吸附能力做出对比。方法:考察在不同初始氨氮质量浓度、进水流量和柱深条件下氨氮的去除情况和穿透曲线,运用Thomas模型、Yoon-Nelson模型和BDST模型对吸附过程拟合。结果:当初始氨氮质量浓度为5 mg·L^(-1)、进水流量为20 mL·min^(-1)、柱深为8 cm时,对氨氮的吸附容量达6.81 mg·g^(-1),远大于NZ吸附容量2.18 mg·g^(-1)。结论:硝酸钠联合焙烧改性沸石可提高对氨氮的吸附能力,动态流实验结果为改性沸石实际应用提供了有力指导。