Comparison of modified montmorillonite adsorbents. Part II: The effects of the type of raw clays and modification conditions on the adsorption performance

This paper builds on the preceding researches to study the effects of the type of clays (montmorillonites K10, KSF) and modifying conditions on the structure and adsorption behavior of resulting clay adsorbents. The raw clays were modified by polymeric Al/Fe species, hexadecyl-trimethylammonium (HDTMA) surfactant and a complex of polymeric Al/Fe-HDTMA. X-ray diffraction spectra was applied to analyze the structure of the raw and modified clays. After modification, the basal spacing of the clays varied, depending on the types of raw clay and modification conditions. Copper and phenol were selected as adsorbates for evaluating the adsorption performance of various clays, which was affected significantly by the types of raw clay and modification conditions. In general the inorganic contaminant (e.g., Cu) tend to be adsorbed by the polymeric Al/Fe modified clay and the organic impurities (e.g., phenol) will be preferably captured by the surfactant modified clay; both due to the specific surface properties resulting from introducing the modifiers. The complex modified clays possessed the ability of adsorbing both inorganic and organic contaminants. In addition, the d 0 0 1 spacing of modified KSF was greater than that of K10; the adsorption performance with modified KSF was thus greater than that with the modified K10. Finally, the ratio of modifiers to the clay (metal:surfactant:clay) has been observed to affect the adsorption performance; the optimal conditions have been defined.     

固定化改性蒙脱土对苯酚吸附性能的研究

利用十六烷基三甲基溴化铵对天然蒙脱土进行改性,并用聚乙烯醇对改性蒙脱土进行固定化处理,然后进行柱状吸附和振荡条件的吸附试验。研究结果表明,HDTMA改性蒙脱土固定化后能有效吸附苯酚,不同环境条件对苯酚的柱状吸附能力产生不同的影响。在pH4~8的范围内,固定化改性蒙脱土对苯酚的吸附效果无显著性差异,pH在10以上,其吸附能力明显下降;温度对吸附效果影响不大;进水苯酚浓度越高,改性蒙脱土对苯酚的吸附量越大,但出水苯酚浓度也高;苯酚的流速越小,吸附容量越高,吸附效果越好。     

Evaluation of modified clay coagulant for sewage treatment

The use of modified clays as coagulants for sewage treatment was investigated in this study. The raw clays were montmorillonites K10 and KSF, and were modified by polymeric Al or Fe and/or Al/Fe mixing polymeric species. The comparative performance of modified clays and aluminium sulphate and ferric sulphate were evaluated in terms of the removal of turbidity, suspended solids, UV(254)-abs, colour, and total and soluble CODs. The results demonstrated that after being modified with mixing polymeric Al/Fe species, two montmorillonite clays possess greater properties to remove the particles (as suspended solids) and organic pollutants (as COD and UV(254)-abs) from the sewage and to enhance the particle settling rate significantly.     

Mg/Al/Fe复合氧化物吸附去除水体中氟化物的研究

采用水热法合成了不同铁掺杂量的Mg/Al/Fe型类水滑石(MAF),根据X射线衍射(XRD)的测定结果,铁存在一个最佳投加量,铁的掺杂量过大则会导致水滑石的层状结构被破坏。通过扫描电镜(SEM)和比表面分析仪(BET)研究了MAF焙烧后的复合金属氧化物(CMAF)的结构和性能,并考察了CMAF对水中氟离子的吸附性能。与CMA相比(铁掺杂量为零),CMAF对氟离子的吸附去除效率明显提高(最大吸附容量75.2 mg/g),整个吸附过程可以用Langmuir吸附等温线更好地描述。通过XRD测定和晶格参数计算,CMAF的结构由吸附前的复合氧化物恢复到层状水滑石结构,表明氟离子在水滑石重构过程中作为层间阴离子进入到水滑石内部,从而达到较高的除氟效率。     

FeAlOx/MMT催化Fenton反应降解高浓度苯酚废水

以蒙脱土为载体制备负载型Fe/Al复合氧化物(FeAlOx/MMT)用于催化Fenton反应降解高浓度苯酚废水。实验结果表明,活性相FeAlOx中Fe/Al摩尔比为0.22时制备所得催化剂对Fenton反应具有最佳活性,且Fe/Al复合氧化物并未嵌入蒙脱土层间。在低温和高pH条件下催化体系存在诱导期,诱导期内FeAlOx/MMT缓释出Fe离子并进而由Fe离子催化溶液中的Fenton反应。通过对非均相催化降解苯酚废水的动力学研究发现,H2O2初始浓度、溶液的pH和反应温度对COD降解效率具有显著影响。调节降解过程中的温度序列和氧化剂引入程序能够缓解高温和高双氧水浓度双重因素耦合导致的HO.自消耗。在优化的降解条件下使用理论用量的H2O2可使得1 g/L的苯酚废水中苯酚降解率达到100%,而COD的降解率则达到97%。     

微孔分子筛的合成及其去除水中氨氮的实验研究

以廉价的天然矿物岩石作为主要原料,采用水热晶化法合成了微孔分子筛。分子筛有效孔径约为0.9 nm,BET比表面积583m2/g,阳离子交换容量(CEC)316 meq/100 g。将其用于水体中氨氮的去除,实验结果表明,分子筛对氨氮的吸附速率较快,吸附时间为20 min时,吸附基本达饱和;分子筛对氨氮的最大吸附量可达11.6 mg/g,其吸附规律很好地符合Fruendlich吸附等温式;在有干扰离子如Ca2+、Mg2+、Al3+和Fe3+等存在的情况下,仍能优先选择吸附NH4+,且吸附率几乎没有变化。动态吸附柱实验的效果好于静态实验,出水12 h内去除率均>85％;饱和了氨氮的分子筛,用氢氧化钠溶液洗脱再生,解吸率达92％,再生后的分子筛与原分子筛相比吸附率几乎没有降低。     

Silane removal at ambient temperature by using alumina-supported metal oxide adsorbents

Copper, zinc, and cerium oxide adsorbents supported on alumina were used to remove silane gas (SiH4). The adsorbents were prepared using a coprecipitation method and characterized by the inductively coupled plasma mass spectrometry, X-ray powder diffractometer, and Brunauer-Emmett-Teller method (BET). The silane removal efficiency and adsorption capacity of the adsorbents were investigated in this study. Test results showed that the adsorbents containing active species had a removal efficiency >99.9% for SiH4 before breakthrough. Adsorbents containing mixed oxides (CuO-CeO2/ Al2O3 and CuO-ZnO/Al2O3), which showed well-dispersed active species and high BET surface areas, had a greater adsorption capacity than the adsorbents containing single metal oxide. However, when the CuO-ZnO/ Al2O3 adsorbents contain >40 wt% of active metal oxides, the increase of active species lowered the BET surface area leading to a decrease of the adsorption capacity. Additionally, when the content of the active metal oxides was between 20% and 40%, the CuO-ZnO/Al2O3 adsorbents demonstrated higher adsorption capacity.     

Electrochemical and FTIR studies of the mutual influence of lead(II) or iron(III) and phenol on their adsorption from aqueous acid solution by modified activated carbons

Cyclic voltammetry and spectral FTIR studies of the influence of activated carbon surface modification on the co-adsorption of metal cation (lead or iron) and phenol from aqueous acidic solution were carried out. The diversity in surface chemical structure was achieved by applying different procedures of inorganic matter removal and by modifying the carbon samples in various ways: heating under vacuum, aminoxidation in an ammonia-oxygen atmosphere, oxidation with concentrated nitric acid. The quantities of adsorbed metal ions (Pb(2+) or Fe(3+)) and phenol from solutions containing cation or phenol separately or in a mixture were determined. The adsorption capacity from acidic aqueous acidic solution depends on the chemical properties of the activated carbon surface (e.g., decrease in phenol adsorption with relative lower basicity of the adsorbent). The electrochemical parameters of electrodes made from the carbon samples were estimated, and some possible electrochemical reactions were determined from voltammograms recorded in acid electrolyte solution containing adsorbed species (separately or as a mixture). Relationships were found between metal ion adsorption and electrochemical behavior of Pb(2+)/Pb(4+) and Fe(3+)/Fe(2+) couples on the one hand, and the presence of phenol in the solutions tested and the influence of surface chemistry of the carbon electrodes on electrochemical processes on the other. The changes in adsorption capacity with respect to the adsorbates used and the changes in FTIR spectra of the carbons as a result of adsorption and/or coupling phenol molecules are discussed.     

Rapid and complete dechlorination of PCP in aqueous solution using Ni-Fe nanoparticles under assistance of ultrasound

The Ni-Fe bimetallic particles have been laboratory prepared using sodium borohydride (NaBH4) as the reductant to reduce Ni2+ and Fe2+ in aqueous solution simultaneously, and characterized by TEM, XRD, BET and XPS. The particles were proved to be nanoscale amorphous alloy with an average diameter of about 30 nm and a BET surface area of 20.9 m2 g(-1). Experiments for dechlorination of pentachlorophenol (PCP) by the Ni-Fe bimetallic nanoscale particles in aqueous solutions were carried out under the enhancement of ultrasound. Major factors that influence the dechlorination efficiency, such as initial pH value, Ni content in the Ni-Fe particles, and output power of ultrasonic irradiation, were investigated. The results indicated that Ni-Fe nanoscale bimetallic particles were very effective for the dechlorination of PCP. Dechlorination efficiency was 46% in 30 min under the optimal condition without assistance of ultrasound, whereas it increased to 96% when ultrasonic irradiation was present. Initial pH value showed apparent effect on the dechlorination. As the pH varied from acidic condition to neutral condition, the dechlorination efficiency decreased dramatically. In addition, the dechlorination efficiency was improved with increased Ni/Fe ratio and ultrasonic output power. Less chlorinated phenols including tetrachlorophenol, trichlorophenol, dichlorophenol, monochlorophenol were formed during the initial reaction, and phenol was determined by GC-MS as sole product in the end of reaction.     

Optimising the preparation of activated carbon from digested sewage sludge and coconut husk.

Preparation of activated carbon from sewage sludge is a promising way to dispose of sewage sludge as well as to produce a low-cost adsorbent for pollutant removal. This research work aimed to optimise the condition for activated carbon preparation from anaerobically digested sewage sludge with the additive coconut husk. The sewage sludge sample was mixed with the additive coconut husk. The preparation condition variables investigated involved the concentration of the ZnCl2 solutions, heating temperature, dwell time and heating rate in pyrolysis and the mixing ratio of coconut husk to sewage sludge. Surface area, pore size distribution, aqueous phenol adsorption capacity and the production yield of the final products were determined and compared. Experimental results revealed that low concentrations of ZnCl2 solution tended to improve the microporosity of the final product. Heating temperature had a considerable impact on the surface area, pore size distribution and phenol adsorption capacity of the final products, whereas dwell time and heating rate performed comparatively insignificantly. The effect of increasing the mixing ratio of coconut husk to sewage sludge was principally to increase the microporosity of the final products. The activated carbon with the highest BET surface area was produced with the activation of 5 M ZnCl2 solution and, thereafter, pyrolysis at a heating temperature of 500 degrees C for 2 h with a heating rate of 10 degrees C/min. The mixing ratio of 1:4 in terms of coconut husk to sewage sludge based on their dried weights was found to be most cost effective.     

不同硅铝比的ZSM-5型沸石分子筛吸附水中Cu2＋离子的研究

考察了3种不同硅铝比的ZSM-5沸石分子筛（25H、38H和50H，25、38和50为硅铝比）对水中Cu2＋的吸附过程及其影响因素。结果表明，3种材料均能有效吸附去除水中Cu2＋离子，动力学符合假二阶动力学模型，吸附等温线符合Langmuir吸附等温式。3种材料吸附速率及吸附容量顺序为：25H〉50H〉38H，其中，25H最大吸附容量达到12．83mg／g。投加量由0．8g／L增加至2．0g／L，材料对Cu2＋吸附去除率由87．0％增加至97．5％。考察水中常见阳离子对吸附的干扰作用，结果表明，干扰离子的影响顺序为：Pb2＋〉K＋〉Na＋〉Mg2＋；随着干扰离子浓度的增大，材料对Cu2＋的去除率显著下降。硅铝比及晶粒形貌均对沸石分子筛吸附Cu2＋有较大影响，小的孔径不利于Cu2＋的吸附，低硅铝比有利于Cu2＋在分子筛上的吸附。     

聚合氯化铝铁的形态分布对微污染源水混凝效果的影响

针对微污染源水中浊度、叶绿素a等的强化去除问题,研究了碱化度、铝铁比和加碱方式等对聚合氯化铝铁形态分布的影响,并考察了形态分布与混凝除污效率和混凝沉淀出水中残铝浓度的关系.结果表明:在铁摩尔分数一定时,混凝剂中单体、中等聚合物和无定形凝胶含量与碱化度存在线性相关性,并推导出中等聚合物含量的计算公式;在碱化度一定时,混凝剂中单体、中等聚合物和无定形凝胶含量与铁摩尔分数也存在线性相关性;增加碱化度或降低铁摩尔分数,可以增加中等聚合物含量、降低单体含量,从而影响混凝除污效率和混凝沉淀后出水中残铝浓度.混凝实验结果表明,混凝过程中叶绿素a去除率和浊度去除率均与混凝剂中中等聚合物含量存在线性相关性,但两者相关系数不同.混凝沉淀后出水中残铝浓度与混凝剂中单体含量存在线性相关性.因此,预聚合的无机高分子混凝剂对提高混凝过程中的除浊、除藻效率,降低混凝沉淀后出水中残铝浓度具有重要的意义.     

Removal and pre-concentration of phenolic species onto beta-cyclodextrin modified poly(hydroxyethylmethacrylate-ethyleneglycoldimethacrylate) microbeads

Poly(Hydroxyethylmethacrylate-Ethyleneglycoldimethacrylate), poly(HEMA-EGDMA), microbeads with 150-200 microm in size, was prepared by suspension polymerization. Beta-cyclodextrin was modified onto the polymeric microbeads using glutaraldahyde activation in an acidic medium at pH=2.5. FT-IR and TGA were used for the characterization of modified polymers and the determination of the nature of the interaction between phenolic compounds and the modified polymeric microbeads. Plain and beta-cyclodextrin modified microbeads were used in adsorption-desorption studies of phenolic species in single solution. Adsorption capacities of the phenolic species onto the plain microbeads were found to be 28.2, 17.0, 14.3, 9.8, and 1.92 mg/g polymer for o-chloro phenol, p-nitro phenol, p-chloro phenol, o-nitro phenol, and phenol, respectively. However, for beta-cyclodextrin modified microbeads, adsorption capacity of phenolic species was determined as 274, 365, 128, 182, and 87 mg/g for phenol, o-nitro phenol, p-nitro phenol, o-chloro phenol, and p-chloro phenol, respectively. Desorption ratio for the phenolic species was more than 90%, except for o-nitro phenol. Detection limits of the phenolic species were improved at least 500-fold for UV-Vis spectrophotometric detection, after the pre-concentration of all phenolic species used in this study. Adsorption time for the phenolic species onto beta-cyclodextrin-modified poly(HEMA-EGDMA) microbeads was found to be reasonable short (10-60 min) and suitable for the applications. Also, synthesized microbeads were useful for the repeated use for the removal and pre-concentration of phenolic species.     

FeAlO_x/MMT催化Fenton反应降解高浓度苯酚废水

以蒙脱土为载体制备负载型Fe/Al复合氧化物（FeAlOx/MMT）用于催化Fenton反应降解高浓度苯酚废水。实验结果表明,活性相FeAlOx中Fe/Al摩尔比为0.22时制备所得催化剂对Fenton反应具有最佳活性,且Fe/Al复合氧化物并未嵌入蒙脱土层间。在低温和高pH条件下催化体系存在诱导期,诱导期内FeAlOx/MMT缓释出Fe离子并进而由Fe离子催化溶液中的Fenton反应。通过对非均相催化降解苯酚废水的动力学研究发现,H2O2初始浓度、溶液的pH和反应温度对COD降解效率具有显著影响。调节降解过程中的温度序列和氧化剂引入程序能够缓解高温和高双氧水浓度双重因素耦合导致的HO.自消耗。在优化的降解条件下使用理论用量的H2O2可使得1 g/L的苯酚废水中苯酚降解率达到100%,而COD的降解率则达到97%。     

Adsorption of phenol by bentonite

The potential of bentonite for phenol adsorption from aqueous solutions was studied. Batch kinetics and isotherm studies were carried out to evaluate the effect of contact time, initial concentration, pH, presence of solvent, and the desorption characteristics of bentonite. The adsorption of phenol increases with increasing initial phenol concentration and decreases with increasing the solution pH value. The adsorption process was significantly influenced by the solvent type in which phenol was dissolved. The affinity of phenol to bentonite in the presence of cyclohexane was greater than that in water and was lowest in the presence of methanol. Methanol was used to extract phenol from bentonite. The degree of extraction was dependent on the amount of phenol adsorbed by bentonite. X-ray diffraction analysis showed that the crystalline structure of bentonite was destroyed when cyclohexane was used. The ability of bentonite to adsorb phenol from cyclohexane decreased as the water to cyclohexane ratio was increased. Furthermore, hysteresis was observed in phenol desorption from bentonite in aqueous solutions. The equilibrium data in aqueous solutions was well represented by the Langmuir and Freundlich isotherm models. The removal of phenol from aqueous solutions was observed without surface modification.     

酚类化合物在2-羧基苯甲酰基修饰的超高交联树脂上的吸附

合成了一种用来吸附和去除水溶液中酚类化合物的 2 羧基苯甲酰基修饰的超高交联吸附树脂 (ZH 0 1) ,并从动力学和吸附容量角度比较了XAD 4、AM 1和ZH 0 1分别吸附浓度为 80 0mg/L苯酚的情况。实验结果表明 ,ZH 0 1吸附剂有利于吸附苯酚、对甲苯酚和对硝基苯酚之类的酚类化合物。动力学和热力学研究都得到了相同的结果 :ZH 0 1对苯酚和对甲苯酚吸附是化学吸附的过渡状态 ,而对对硝基苯酚的吸附是一种物理吸附过程 ,并且显示了ZH 0 1表面均孔特性。苯酚在ZH 0 1上的小柱吸附研究表明了吸附穿透容量和总吸附量分别为 2 .38mmol/g和 3.0 5mmol/g ,溶剂甲醇对吸附在ZH 0 1上苯酚的脱附效果较好。     

Sorption of non-ionic surfactants to soil: the role of soil mineral composition

In this study, the importance of individual soil mineral constituents on non-ionic surfactant sorption is evaluated by employing scanning electron microscopy (SEM) equipped with energy-dispersive X-ray analysis (EDAX) to observe microchemical surface composition of model soil colloids and relate surface microchemical composition to the sorption behavior of a non-ionic surfactant, Polyethylene Glyco Mono-p-nonylphenyl Ether (A9PE10), on selected model soil colloids. This information is critical to understanding the fate and transport of this class of contaminants in subsurface. Results obtained from this study indicate that a correlation between the atomic ratio of Si:(Al + Fe) on soil mineral surface and A9PE10 sorption capacity exist, where those soil with larger value of Si:(Al + Fe) ratio exhibit higher sorption capacity. This allows us to predict that the non-ionic surfactant sorption capacity for soil decrease with progressively increasing states of soil maturity.     

胶质芽孢杆菌、黑曲霉及与沸石联合对模拟废水中Fe~（3＋）处理研究

研究沸石、胶质芽孢杆菌（Bacillus mucilaginosus）、黑曲霉（Aspergillus Niger）、胶质芽孢杆菌与沸石联合以及黑曲霉与沸石联合对模拟废水中Fe3＋的吸附等温曲线,分析它们对Fe3＋模拟废水的吸附及絮凝作用。结果表明：沸石对Fe3＋吸附作用符合Freundlich方程;胶质芽孢杆菌分泌含有—OH和COO-的胞外多糖,对Fe3＋具有较好的吸附效果;沸石与胶质芽孢杆菌联合对模拟废水中Fe3＋的处理,低浓度以沸石对Fe3＋的吸附为主,加入胶质芽孢杆菌絮凝剂使吸附了Fe3＋的沸石进行絮凝沉降,吸附等温曲线符合Langmuir吸附等温方程,高浓度两者共同作用使吸附量增加;黑曲霉对Fe3＋的吸附符合BET吸附等温方程;沸石与黑曲霉两者共同作用对Fe3＋模拟废水吸附等温曲线为直线。通过去除效果对比分析可知：胶质芽孢杆菌既有吸附又有絮凝功能;胶质芽孢杆菌絮凝剂无论是对Fe3＋的吸附还是对吸附Fe3＋沸石的絮凝都比黑曲霉对Fe3＋处理效果好;胶质芽孢杆菌和一些非金属矿物复合处理污染废水是一种无毒、低成本环保的处理方法,本研究将为它们在工程中的应用提供实践依据。     

多孔水凝胶P（HEA/AMPS）对水溶液中Fe（Ⅲ）的吸附

以2-丙烯酸羟乙酯（HEA）和2-丙烯酰胺基-2-甲基丙磺酸（AMPS）为单体合成了聚合物水凝胶（PHEA/AMPS）,采用水凝胶对水溶液中Fe（Ⅲ）的吸附行为进行了研究。实验主要考察了聚合物组分、溶液pH、初始Fe（Ⅲ）浓度和吸附时间对水凝胶吸附作用的影响,并通过FT-IR和XPS分析了吸附前后水凝胶的变化。结果表明,当单体摩尔比AMPS∶HEA=1∶1,pH=2时,水凝胶对Fe（Ⅲ）的吸附容量最大。水凝胶对水溶液中Fe（Ⅲ）的吸附容量随着溶液中初始Fe3＋浓度的增加而增加,但当初始Fe3＋的浓度达到1 g/L时,吸附容量基本达到饱和。吸附等温线符合Langmuir等温线方程,吸附动力学符合准二级模型。FI-IR和XPS的分析表明,水凝胶的磺酸基和酰胺基是吸附Fe3＋的有效功能性基团,吸附机理为螯合和离子交换。     

Methidathion complexes with homoionic and surfactant-modified montmorillonites

The formation of the insecticide methidathion (S-[(5-methoxy-2-oxo-1,3,4-thiadiazol-3(2H)-yl)methyl] O,O-dimethyl phosphorodithioate) complexes with inorganic cation-saturated (Mg2+, Ca2+, Cu2+, and Ni2+) montmorillonites was investigated. The nature and structure of the complexes was determined by X-ray diffraction and infrared spectroscopy. The arrangement of the pesticide molecule in the interlayer space was also considered from ab initio calculations using simpler related molecules. The insecticide methidathion penetrated the interlayer spaces of the homoionic clay samples. The ligand-cation interactions in these complexes depend on the nature and characteristics of the saturating cations. Mechanisms involving water bridges and direct coordination with the exchange cation were proposed for the adsorption of methidathion by inorganic cation-saturated montmorillonites. The effect of the inorganic cations on the sorption of the cationic surfactant tetradecyltrimethylammonium bromide (TDTMA) by montmorillonite was also studied and the subsequent sorption of methidathion in TDTMA+-Montmorillonite determined. Van der Waals bonds constitute the methidathion adsorption mechanism by montmorillonite saturated with TDTMA+. The arrangements of methidathion and of the cationic surfactant molecules in the montmorillonite interlayer space were demonstrated.