pH及Zn2+对土壤和铁、铝氧化物吸附苄嘧磺隆的影响

用平衡吸附法研究了3种供试样品(广州赤红壤、铝氧化物、针铁矿)对苄嘧磺隆的等温吸附,同时研究了pH及Zn2 对供试样品吸附苄嘧磺隆的影响.结果表明,在实验所用的苄嘧磺隆的浓度范围内,供试样品对苄嘧磺隆的吸附量各不相同;供试样品吸附苄嘧磺隆的量随溶液pH及Zn2 浓度的改变而变化,且影响不尽相同,这主要与供试样品的组成有关.     

不同粘土处理水中重金属的性能研究

比较了膨润土、高岭土、伊利石等不同粘土对处理重金属离子的效能,探讨了３种粘土去除废水中镍、铜、锌、镉的适宜条件,并对３种粘土去除重金属离子的机理进行了初步探讨,应用于电镀废水中重金属离子的处理,效果良好。     

Sorption behavior of U(VI) on phyllite: experiments and modeling

The sorption of U(VI) onto low-grade metamorphic rock phyllite was modeled with the diffuse double layer model (DDLM) using the primary mineralogical constituents of phyllite, i.e. quartz, chlorite, muscovite, and albite, as input components, and as additional component, the poorly ordered Fe oxide hydroxide mineral, ferrihydrite. Ferrihydrite forms during the batch sorption experiment as a weathering product of chlorite. In this process, Fe(II), leached from the chlorite, oxidizes to Fe(III), hydrolyses and precipitates as ferrihydrite. The formation of ferrihydrite during the batch sorption experiment was identified by M?ssbauer spectroscopy, showing a 2.8% increase of Fe(III) in the phyllite powder. The ferrihydrite was present as Fe nanoparticles or agglomerates with diameters ranging from 6 to 25 nm, with indications for even smaller particles. These Fe colloids were detected in centrifugation experiments of a ground phyllite suspension using various centrifugal forces. The basis for the successful interpretation of the experimental sorption data of uranyl(VI) on phyllite were: (1) the determination of surface complex formation constants of uranyl with quartz, chlorite, muscovite, albite, and ferrihydrite in individual batch sorption experiments, (2) the determination of surface acidity constants of quartz, chlorite, muscovite, and albite obtained from separate acid-base titration, (3) the determination of surface site densities of quartz, chlorite, muscovite, and albite evaluated independently of each other with adsorption isotherms, and (4) the quantification of the secondary phase ferrihydrite, which formed during the batch sorption experiments with phyllite. The surface complex formation constants and the protolysis constants were optimized by using the experimentally obtained data sets and the computer code FITEQL. Surface site densities were evaluated from adsorption isotherms at pH 6.5. The uranyl(VI) sorption onto phyllite was accurately modeled with these newly determined constants and parameters of the main mineralogical constituents of phyllite and the secondary mineralization phase ferrihydrite. The modeling indicated that uranyl sorption to ferrihydrite clearly dominates uranyl sorption, showing the great importance of secondary iron phases for sorption studies.     

Mobility of Cd and Cu in formulated sediments coated with iron hydroxides and/or humic acids: a DGT and DGT-PROFS modeling approach

The diffusive gradients technique in thin films (DGT) was used to investigate the kinetic resupply of Cd and Cu to pore water from the solid phase. For the sake of simplification, experiments were performed using formulated sediments that differed in the presence or absence of humic acids (HA) and/or of iron hydroxides (i.e., goethite and ferrihydrite). The effects of the time after the contamination of the solid phase (aging effect) on formulated sediments that were coated with goethite and HA and spiked with Cd were also evaluated. Kinetic DGT results were interpreted using the newly developed, multi-compartmental model DGT-PROFS.Due to Cu humate formation, the addition of HA slightly increased the Cu concentration in the pore water independent of the effect of the iron hydroxide coating on the formulated sediments and slightly decreased that of Cd. The impact of 8-190 d of aging resulted in a significant decrease in the Cd concentration of the pore water over an increasing incubation time.Modeling our results with DGT-PROFS led to the following conclusions concerning the impact of HA and iron hydroxides on Cd and Cu availability. First, in the presence of HA and absence of iron hydroxides, Cd is associated mainly with weak sites, while Cu is bound to strong sites. Similarly, in the presence of both iron hydroxides and HA, Cu appeared to be more heavily associated with the strong sites than did Cd. When the incubation time increased from 8 to 190 d, a proportion of Cd initially adsorbed onto weak sites transferred to the strong sites, suggesting that the adsorption of Cd on sediments is controlled partially by slow kinetic processes.     

Transformation of carbon tetrachloride by bisulfide treated goethite, hematite, magnetite, and kaolinite

This study investigated the transformation of carbon tetrachloride (CT) by goethite, hematite, magnetite, and kaolinite treated with bisulfide to form coatings of iron monosulfide (FeS) and other Fe(II) species. These coatings contribute to abiotic natural attenuation in anaerobic environments. Batch kinetic experiments were performed under anoxic conditions at pH 8.0. Surface-area-normalized pseudo-first-order rate constants for CT transformation did not differ significantly for the three HS- treated iron oxides, but the rate of CT transformation by bisulfide-treated kaolinite was significantly lower, most likely due to kaolinite's lower iron content. The yield of chloroform (CF) from CT transformation was typically approximately 1%. There was negligible or only slight adsorption of several natural organic matter (NOM) model compounds to the surface of HS- treated goethite, and these compounds had no influence on CT transformation rate constants or CF yields. Juglone, on the other hand, adsorbed to a greater extent, and also significantly influenced the CF yield, increasing it by a factor of approximately 20 for HS- treated hematite. We speculate that juglone or its HS- addition product adsorbed to the mineral surface and acted as a hydrogen atom donor that reacted with the trichloromethyl radical intermediate, increasing the CF yield.     

Complexes of fulvic acid on the surface of hematite, goethite, and akaganeite: FTIR observation

The present work extended our knowledge on the binding and complexation of a fulvic acid (FA) derived from leonardite and the iron oxides (hematite, goethite and akaganeite) by Fourier transform infrared spectroscopy (FTIR). As a prerequisite, the iron oxides were firstly prepared and characterized by transmission electron micrograph (TEM). All iron phases were single and well-described crystalloid. The FTIR data obtained by two different sampling preparation methods gave the consisting evidences that under our experimental conditions the interaction mechanism was to the ligand-exchange involving carboxylic functional groups of the FA and the surfaces sites of both hematite and goethite, while no complexation can be evidenced in the case of akaganeite, only surface adsorption. In general, the binding affinities of the iron oxides with the FA was in the order of hematite>goethite>akaganeite. The present method, although associated with some uncertainties, provided an opportunity to increase the knowledge in the field of the humic chemistry.     

Removal of arsenic(V) from aqueous solutions using iron-oxide-coated modified activated carbon.

Removal of arsenic(V) from aqueous solutions was evaluated with the following three different sorption materials: coal-based activated carbon 12 x 40 (activated carbon), iron(II) oxide (FeO)/activated carbon-H, and iron oxide. The apparent characteristics and physical chemistry performances of these adsorbents were investigated by X-ray diffraction, nitrogen adsorption, and scanning electronic microscope. Also, batch experiments for arsenic removal were performed, and the effects of pH value on arsenic(V) removal were studied. The results suggest that the main phases of the iron oxide surface are magnetite, maghemite, hematite, and goethite; fine and uniform iron oxide particles can cover activated carbon surfaces and affect the surface area or pore structures of activated carbon; adsorption kinetics obey a pseudo-first-order rate equation; and adsorption capacities of adsorbents are affected by the values of pH. The optimum value of pH for iron oxide lies in a narrow range between 4.0 and 5.5, and arsenic(V) removal by FeO/activated carbon-H is ideal and stable in the pH range 3 to 7, while activated carbon has the lowest adsorption capacity in the entire pH range. Also, the adsorption characteristics of FeO/activated carbon-H composites and virgin activated carbon match well the Langmuir adsorption model, while those of iron oxide fit well the Freundlich adsorption model.     

Adsorption of molybdate and tetrathiomolybdate onto pyrite and goethite: effect of pH and competitive anions

The adsorption of two major molybdenum (Mo) species, molybdate (MoO4(2-)) and tetrathiomolybdate (MoS4(2-)) onto two main iron minerals pyrite (FeS2) and goethite (FeOOH) is addressed to elucidate the possible mechanisms of molybdenum immobilization in anoxic sediments. Suspensions of MoS4(2-) (or MoO4(2-)) and goethite (or pyrite) in 0.1M NaCl solution were equilibrated under anoxic conditions at 25 degrees C in the pH range from 3 to 10. The competitive effects of sulfate, phosphate, and silicate on the adsorption of MoO4(2-) and MoS4(2-) by pyrite and goethite are also addressed. Adsorption of MoO4(2-) and MoS4(2-) on pyrite and goethite is in general well described by a Langmuir model at low pH; the extent of sorption is a function of pH and the surface loading. Maximum sorption is observed in the acidic pH range (pH<5) at low surface loading. The adsorption of molybdenum (micromol g(-1)) depends upon Mo species and on the type of iron mineral following the order: MoS4(2-)-goethite > MoO4(2-)-goethite > MoS4(2-)-pyrite > MoO4(2-)-pyrite. Phosphate appears to compete strongly with MoO4(2-) and MoS4(2-) for the sorption sites of pyrite and goethite. The strength of the phosphate competitive effect follows the sequence of MoO4(2-)-goethite approximately = MoO4(2-)-pyrite > MoS4(2-)-pyrite > MoS4(2-)-goethite. Silicate and sulfate have a negligible effect on the sorption of MoO4(2-) and MoS4(2-). The preferred adsorption by iron mineral of MoS4(2-), as well as its behavior in the presence of competitive anions suggests that tetrathiomolybdate species may be an ultimate reservoir and may control Mo enrichment in the sediments.     

Effects of organic acids on adsorption of lead onto montmorillonite,goethite and humic acid

Adsorption isotherms for Pb onto six soil components (quartz, feldspar, kaolinite, montmorillonite, goethite and humic acid) were studied. The influence of pH, EDTA and citric acid on the adsorption of Pb onto montmorillonite, goethite and humic acid were considered. Results indicate that the experimental data fit the Langmuir Adsorption Isotherm. The adsorption capacity for Pb at pH 6 was found to be in the order: humic acid (22.7 mg g(-1)) > goethite (11.04 mg g(-1)) > montmorillonite (10.4 mg g(-1)) > kaolinite (0.91 mg g(-1)) > feldspar (0.503 mg g(-1)) > quartz (0.148 mg g(-1)). Generally, the amount of Pb adsorbed onto montmorillonite, goethite and humic acid decreased with increasing concentrations of EDTA and citric acid and with increases in alkality. However, there were two exceptions: (1) addition of citric acid increased the amount of Pb adsorbed onto humic acid; and (2) the amount of Pb adsorbed onto goethite decreased with increasing pH in the presence of EDTA. Some mechanisms involved in the adsorption reactions are discussed.     

Modeling the competitive effect of phosphate, sulfate, silicate, and tungstate anions on the adsorption of molybdate onto goethite

The mobility of Mo in soils and sediments depends on several factors including soil mineralogy and the presence of other oxyanions that compete with Mo for the adsorbent's retention sites. Batch experiments addressing Mo adsorption onto goethite were conducted with phosphate, sulfate, silicate, and tungstate as competing anions in order to produce competitive two anions adsorption envelopes, as well as competitive two anions adsorption isotherms. Tungstate and phosphate appear to be the strongest competitors of Mo for the adsorption sites of goethite, whereas little competitive effects were observed in the case of silicate and sulfate. Mo adsorption isotherm from a phosphate solution was similar to the one from a tungstate solution. The charge distribution multi-site complexation (CD-MUSIC) model was used to predict competitive adsorption between MoO(4)(2-) and other anions (i.e., phosphate, sulfate, silicate and tungstate) using model parameters obtained from the fitting of single ion adsorption envelopes. CD-MUSIC results strongly agree with the experimental adsorption envelopes of molybdate over the pH range from 3.5 to 10. Furthermore, CD-MUSIC prediction of the molybdate adsorption isotherm show a satisfactory fit of the experimental results. Modeling results suggest that the diprotonated monodentate complexes, FeOW(OH)(5)(-0.5) and FeOMo(OH)(5)(-0.5), were respectively the dominant complexes of adsorbed W and Mo on goethite 110 faces at low pH. The model suggests that Mo and W are retained mainly by the formation of monodentate complexes on the goethite surface. Our results indicate that surface complexation modeling may have applications in predicting competitive adsorption in more complex systems containing multiple competing ions.     

针铁矿对Pb~(2+)的吸附特征及影响因素研究

通过恒温振荡平衡法研究了Pb~(2+)在针铁矿上的等温吸附和吸附动力学特征,探讨了吸附的影响因素.结果表明:(1)随Pb~(2+)平衡浓度和pH的增大,针铁矿对Pb~(2+)的吸附量逐渐增大.(2)针铁矿对Pb~(2+)的等温吸附可用Freundlich和Langmuir方程较好地拟合.(3)在相同温度和pH下,随离子强度的提高,针铁矿对Pb~(2+)的吸附量增大.(4)在相同离子强度和pH下,针铁矿对Pb~(2+)的吸附量总体随温度升高而增大.针铁矿对Pb~(2+)的吸附是自发进行的吸热反应.(5)针铁矿吸附Pb~(2+)的过程可分为初始的快吸附和随后的慢吸附2个阶段.pH影响吸附反应快慢,随pH增大吸附速率增大;随着pH的增大,达到平衡吸附的时间缩短.吸附动力学方程用Elovich方程拟合最佳.     

Sorption of 1-hydroxy-2-naphthoic acid to goethite, lepidocrocite and ferrihydrite: batch experiments and infrared study

The adsorption of naphthoic acids to iron oxides and hydroxides influences strongly their mobility in soils and sediments. Sorption of 1-hydroxy-2-naphthoic acid (HNA) to three iron oxides was examined over a wide range of conditions (pH, ionic strength, sorbate and sorbent concentrations). In the examination of HNA sorption, Tempkin model was performed to fit sorption data of HNA onto all iron oxides. The adsorption in the Henry law range increases in the order: goethite相似文献   

Removal of metal ions and humic acid from water by iron-coated filter media

Iron oxide is an excellent, regenerable adsorbent, and often controls free metals through adsorption reaction. The utilization of heating process for coating iron oxide on sand surface allowed the media to be used in a packed column. Iron-coated sand was investigated for adsorbing metal ions and natural organic matter from water by batch and column experiments. Chemical analysis (energy dispersive analysis of X-ray, EDAX) was used for characterizing the copper and lead adsorption sites on iron-coated sand. From the batch experiment results, the copper and lead ions could be removed simultaneously by the iron-coated sand in the competition adsorption system. The interaction between copper, lead ions and iron oxide on sand surface was primarily the chemical bonds. The maximum adsorption capacities of iron-coated sand for copper and lead were 0.259 mg Cu/g-sand and 1.211 mg Pb/g-sand, respectively. The presence of humic acid led to increase the adsorption of copper and lead. Results from column experiments indicated that the copper ions, lead ions and humic acid could be removed completely before the breakpoint. Consequently, the iron-coated sand may be applied for the adsorption/filtration of metal ions and natural organic matters from water.     

U(VI) adsorption on aquifer sediments at the Hanford Site

Aquifer sediments collected via split-spoon sampling in two new groundwater wells in the 200-UP-1 operable unit at the Hanford Site were characterized and showed typical Ringold Unit E Formation properties dominated by gravel and sand. High iron-oxide content in Fe oxide/clay coatings caused the highest U(VI) adsorption as quantified by batch K(d) values, indicating iron oxides are the key solid adsorbent in the 200-UP-1 sediments that affect U(VI) fate and mobility. Even though U(VI) adsorption on the gravel-sized fraction of the sediments is considered to be negligible, careful characterization should be conducted to determine U(VI) adsorption on gravel, because of presence of Fe oxides coatings and diffusion-controlled adsorption into the gravel particles' interior surfaces. A linear adsorption isotherm was observed up to 10(-6) M (238 microg/L) of total U(VI) concentration in batch U(VI) adsorption tests with varying total U(VI) concentrations in spiked groundwater. U(VI) adsorption decreased with increasing concentrations of dissolved carbonate, because strong anionic aqueous uranium-carbonate complexes formed at high pH and high alkalinity conditions. Noticeable uranium desorption hysteresis was observed in a flow-through column experiment, suggesting that desorption K(d) values for aged uranium-contaminated sediments at the Hanford Site can be larger than adsorption K(d) values determined in short-term laboratory experiments and slow uranium release from contaminated sediments into the groundwater is expected.     

Preparation of a porous clay heterostructure and study of its adsorption capacity of phenol and chlorinated phenols from aqueous solutions.

A porous clay heterostructure (PCH) from a Mexican clay was prepared and characterized, and its aqueous phenol and dichlorophenols (DCPs) adsorption capacities were studied using a batch equilibrium technique. The PCH displayed a surface area of 305.5 m2/g, 37.2 A average porous diameter, and a basal space of 23.2 A. The adsorption capacity shown by the PCH for both phenol and DCPs from water (14.5 mg/g for phenol; 48.7 mg/g for 3,4-DCP; and 45.5 mg/g for 2,5-DCP) suggests that the PCH has both hydrophobic and hydrophilic characteristics, as a result of the presence of silanol and siloxane groups formed during the pillaring and calcination of the PCH. The values of maximal adsorption capacity for dichlorophenols were higher than those reported for aluminum pillared clays and some inorgano-organo clays and comparable with some ionic exchange resins.     

铁盐改性砂制备及其吸附Zn~(2+)的性能研究

通过改变石英砂表面的物理化学性质,提高石英砂的吸附效率,考察其对废水中的Zn~(2+)去除效果.以石英砂为载体,分别用反复高温加热法和反复碱性沉积法制备了三氯化铁改性砂、硝酸铁改性砂,测定2种方法制备的铁盐改性砂的表面含铁量、铁盐的酸稳定性及比表面积,并比较2种铁盐改性砂对Zn~(2+)的吸附效果.结果表明,三氯化铁改性砂、硝酸铁改性砂的比表面积分别为2.468、4.247 m~2/g,比石英砂比表面积分别提高6.910、12.612倍;在pH为中性条件下,石英砂对Zn~(2+)去除率为43%左右,三氯化铁改性砂对Zn~(2+)去除率达到70%左右,硝酸铁改性砂对Zn~(2+)去除率达到85%左右,表明铁盐改性砂对Zn~(2+)去除能力比石英砂有很大提高;铁盐改性砂对Zn~(2+)的吸附有一定容量,表面的活性中心越多,吸附能力越大;铁盐改性砂对Zn~(2+)的去除率随着pH的升高而增加,当pH>8.5时,Zn~(2+)去除率可达90%左右.     

Adsorption of natural organic matter from waters by iron coated pumice

Natural pumice particles were used as granular support media and coated with iron oxides to investigate their adsorptive natural organic matter (NOM) removal from waters. The impacts of natural pumice source, particle size fraction, pumice dose, pumice surface chemistry and specific surface area, and NOM source on the ultimate extent and rate of NOM removal were studied. All adsorption isotherm experiments were conducted employing the variable-dose completely mixed batch reactor bottle-point method. Iron oxide coating overwhelmed the surface electrical properties of the underlying pumice particles. Surface areas as high as 20.6m(2)g(-1) were achieved after iron coating of pumice samples, which are above than those of iron coated sand samples reported in the literature. For all particle size fractions, iron coating of natural pumices significantly increased their NOM uptakes both on an adsorbent mass- and surface area-basis. The smallest size fractions (<63 microm) of coated pumices generally exhibited the highest NOM uptakes. A strong linear correlation between the iron contents of coated pumices and their Freundlich affinity parameters (K(F)) indicated that the enhanced NOM uptake is due to iron oxides bound on pumice surfaces. Iron oxide coated pumice surfaces preferentially removed high UV-absorbing fractions of NOM, with UV absorbance reductions up to 90%. Control experiments indicated that iron oxide species bound on pumice surfaces are stable, and potential iron release to the solution is not a concern at pH values of typical natural waters. Based on high NOM adsorption capacities, iron oxide coated pumice may be a promising novel adsorbent in removing NOM from waters. Furthermore, due to preferential removal of high UV-absorbing NOM fractions, iron oxide coated pumice may also be effective in controlling the formation of disinfection by-products in drinking water treatment.     

Partitioning and availability of sediment-bound metals following final sewage effluent release to a lowland river

A simple partitioning scheme was used to assess the partitioning and behaviour of copper, cadmium, iron, lead and manganese within the surface waters and sediments of the River Yare, Norfolk, UK, following the discharge of final effluent to the water course from municipal sewage treatment works (STW). Sewage effluent discharges were shown to increase metal concentrations and complexation capacities in receiving waters, but the tidal nature of the river meant that surface water monitoring could not accurately pinpoint the contamination source or the main metal partitioning trends. Sediments formed a more stable base on which to perform contaminant studies: these revealed that metals discharged from the STW rapidly accumulated in bottom deposits in relative stable chemical forms.     

Effects of natural organic matter on the microporous sorption sites of black carbon in a Yangtze River sediment

Black carbon (BC), characterized by high microporosity and high specific surface area (SSA), has been demonstrated to have substantial contributions to the sorption of hydrophobic organic chemicals in soils and sediments. Other naturally occurring organic matters provide soft and penetrable sorption domains while may cling to BC and affect its original surface properties. In this work, we studied the sorption sites of a Yangtze River sediment sample with organic carbon (OC) content of 3.3 % and the preheated sediment (combusted at 375 °C) with reduced OC content (defined as BC) of 0.4 % by gas and pyrene sorption. The SSA and microporosity of the pristine and preheated sediments were characterized by N₂ and CO₂ adsorption. The results suggest that the adsorption of N₂ was hindered by amorphous organic carbon (AOC) in the pristine sediment but CO₂ was not. Instead, the uptake of CO₂ was higher in the presence of AOC, likely due to the partition of CO₂ molecules into the organic matter. The pyrene adsorptions to BC in pristine and preheated sediments show a similar adsorption capacity at high concentration, suggesting that AOC of ca. 2.9 % in the pristine sediment does not reduce the accessibility to the sorption sites on BC for pyrene.     

Adsorption of lead onto smectite from aqueous solution

The purpose of this research is to study the effect of a new method of adsorption using membrane filtration to determine the maximum amount of lead adsorbed by clay and investigate the behavior of the clay after adsorption of the said metal. Treatment of wastewater contaminated with heavy metals depends on the characteristics of the effluent, the amount of final discharge, the cost of treatment, and the compatibility of the treatment process. The process of adsorption of heavy metals by clays may be a simple, selective, and economically viable alternative to the conventional physical–chemical treatment. This is justified by the importance of the surface developed by this material, the presence of negative charges on the said surface, the possibility of ion exchange taking place, and its wide availability in nature. The removal of lead from wastewater was studied by using the adsorption technique and using clay as the adsorbent. A method was optimized for adsorption through a membrane approaching natural adsorption. This new method is simple, selective, and the lead adsorption time is about 3 days. The various properties of clay were determined. It was observed that the cation exchange capacity of the clay was 56 meq/100 g of hydrated clay for the raw sample and 82 meq/100 g for the purified sample. The total surface area determined by the methylene blue method was equal to 556 and 783 m²/g for the raw and purified samples, respectively. The adsorption kinetics depends on several parameters. The Pb(II) clay, obeys the Langmuir, Freundlich, and the Elovich adsorption isotherms with high regression coefficients. The use of this adsorbent notably decreases the cost of treatment. It was concluded that clay shows a strong adsorption capacity on Pb(II), the maximum interaction occurring with purified clay treated at high concentration of lead. It is proposed that this adsorption through a membrane be extended for the treatment of effluents containing other metals.