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1.
负载硼的针铁矿结构表征研究   总被引：1，自引：0，他引：1  
人工合成了针铁矿（Goethite）及其负载硼的氧化物（硼吸附态针铁矿Ad—B—Goethite，硼包被态针铁矿Oc—B—Goethite），用IR、X射线衍射、TEM对其进行表征，测定了它的比表面积及其对锰离子的吸附性能。IR分析表明，负载硼的针铁矿较之普通针铁矿在888cm。处的Fe—OH—Fe表面羟基弯曲振动、1000cm^-1处的表面Fe—OH弯曲振动及3100cm^-1处的游离羟基峰均减弱；硼吸附态针铁矿在458．5cm^-1处，硼包被态针铁矿在527．2cm^-1和476．5cm^-1处出现了与BO3和B（O，OH）4的弯曲振动有关的吸收峰。X射线衍射分析表明硼吸附态针铁矿的晶形与普通针铁矿相似，而硼包被态针铁矿的衍射吸收峰的位置、个数和相对强度都发生了变化。从TEM图上可看出硼包被态针铁矿的晶体明显要小些。实验测得3种矿物的比表面积分别是：普通针铁矿108．4m^2g^-1，吸附态针铁矿88．69m^2g^-1，包被态针铁矿120．5m^2g^-1。对锰离子的吸附量为硼包被态针铁矿明显大于硼吸附态针铁矿大于普通针铁矿。结果表明：硼包被态针铁矿（Oc—B—goethite）中B进入了针铁矿的品格，影响晶体的生长，使晶体的结晶性较差，晶体较小、比表面积增大，对锰离子的净吸附能力强。这也说明，土壤中的硼不仅起到植物营养的作用，其在形成负载硼的铁氧化物后有利于减轻土壤锰的毒害。  相似文献   

2.
The preparation, characterization, and environmental application of crosslinked chitosan-coated bentonite (CCB) beads for tartrazine adsorption have been investigated. CCB beads were characterized by using Fourier transform infrared spectrophotometer (FTIR), scanning electron microscope (SEM), and Brunauer–Emmett–Teller (BET) surface area and Barrett–Joyner–Halenda (BJH) pore size distribution analyses were also determined. The values of pH of the aqueous slurry and pH of zero point charge (pHZPC) were almost equal. The adsorption at equilibrium of tartrazine was found to be a function of pH of the solution, stirring rate, contact time, and tartrazine concentration. The optimum conditions for tartrazine adsorption were pH 2.5, stirring rate of 400 rpm and contact time of 80 min. Pseudo-first-order and pseudo-second-order models were used to analyze the kinetics of adsorption with the latter found to agree well with the kinetics data, suggesting that the rate determining step may be chemisorption. The two most common isotherm models, Langmuir and Freundlich, were used to describe the adsorption equilibrium data. On the basis of Langmuir isotherm model, the maximum adsorption capacities were determined to be 250.0, 277.8, and 294.1 mg g?1 at 300, 310, and 320 K, respectively. Desorption studies were carried out at different concentrations of EDTA, H2SO4, and NaOH. All desorbing solutions showed poor recovery of tartrazine.  相似文献   

3.
Co(II) adsorption on high-purity amorphous Fe?CMn binary oxide adsorbent was investigated. The Co(II) adsorption behavior of this synthetic material was studied and discussed as a function of contact time, pH and initial concentration. The Langmuir and Freundlich isotherm models were applied to fit the Co(II) adsorption data on Fe?CMn binary oxide with mesoporous particles of irregular surface morphology and a specific surface area of 201.8?m2?g?1 with a maximum capacity of 32.25?mg?g?1. Various kinetic models applied to the adsorption rate data of the Co(II) ion were evaluated. The results show that the pseudo-second order and the intra-particle mass transfer diffusion models correlated best with the experimental rate data. The adsorption activation energy was found to be 9.07?kJ?mol?1 indicating that it corresponds to a physical adsorption. The evaluated thermodynamics parameters of the adsorption values indicated the endothermic and spontaneous nature of the adsorption. The results obtained confirmed that Fe?CMn binary oxide had the potential to be utilized as a low-cost and relatively effective adsorbent for Co(II) removal from wastewater.  相似文献   

4.
The effects of different fertilization techniques—mineral [21% nitrogen (N)], organomineral (10% N), mycorrhiza inoculumns, wine-producing residues (three different formulas: distiller's residue, 2.2% N; anaerobic digestate, 2.8% N; and the same plus mycorrhizas inoculum), and compost by farm residues (2.0% N)—on adsorption of boron (B) were investigated. The soils, collected after a triennial lettuce (Lactuca sativa L. cv. ‘Bacio’) cultivation, were equilibrated using six B concentrations [0, 1, 5, 20, 50, and 100 mg B L?1, as boric acid (H3BO3)]. The B adsorption was studied at two soil mass (ms) to solution volume (vs) ratios, ms/vs = 0.5 and 1, and the Langmuir, Eadie–Hofstee, Freundlich, and Temkin adsorption equations were fitted to the B adsorption data. The proportion of adsorbed B was gradually less in the more concentrated solutions, with differences in ms/vs ratio and in treatments: the percentage of B adsorbed was greater for ms/vs = 0.5 and for distiller's residue and mineral fertilizer. The Freundlich isotherm represented the measured B adsorption data well; at ms/vs = 0.5, the values of Freundlich adsorption maxima Xm varied from 93.14 to 111.88 mg kg?1 (organomineral fertilizer and distiller's residue, respectively; at ms/vs = 0.5) and from 32.14 to 40.32 mg kg?1 (mineral fertilizer and control, respectively; at ms/vs = 1). In our study, generally the B adsorption was greater with mineral fertilizers and distiller's residue, whereas the organomineral fertilizer led to a decrease in B adsorption. The parameters of adsorption isotherms were significantly correlated, at various degrees, with the exchangeable cation sodium. The adsorption isotherms were well explained by the lower soil mass to volume solution ratio in the order Freundlich > Temkin ≌ Langmuir > Headie–Hofstee.  相似文献   

5.
A peanut shell-derived oxidized activated carbon (OAC) with high surface area was prepared by zinc chloride (ZnCl2) chemical activation and subsequent nitric acid oxidation. OAC was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and N2 adsorption-desorption. The results showed that OAC had the surface area of 1807 m2 g?1, with the total pore volume of 0.725 cm3 g?1 and average pore diameter of 3.8 nm. More importantly, when OAC acted as an adsorbent, it exhibited high efficiency to remove basic blue 41 (BB-41), congo red (CR), phenol, Cr(VI), and Pb(II) from aqueous solution due to its universality in adsorption. Batch adsorption experiments were carried out to study the effect of various parameters such as pH, initial concentration, temperature, and contact time. Also, the isotherms, kinetic models, and thermodynamics of adsorption process were investigated. The equilibrium data for CR and Pb(II) were fitted to Langmuir isotherm model, while Freundlich model was suitable for the equilibrium isotherm of BB-41, phenol, and Cr(VI), respectively. As the result indicated, peanut shell was a suitable raw material to synthesize OAC which could be employed as an efficient and universal adsorbent for removing organic pollutants and heavy metal ions from wastewater.  相似文献   

6.
Adsorption of polyvinylalcohol (PVA) in aqueous suspension has been used to measure the specific surface area (SSA) of a silicon dioxide, a goethite, a clay, and a sample of a topsoil, the latter before and after treatment with hydrogen peroxide. Surface areas were calculated from each of the plateaus of the isotherms derived from the Langmuir equation fitted to the data, using a value of 0.04268 nm2 for the molecular area of a monomer of PVA. We compared these SSA values with those measured by N2 adsorption. The SSA values of the silicon dioxide, the goethite and the clay are in excellent agreement with the corresponding N2‐BET areas. The removal of organic matter by H2O2 from the topsoil sample led to a marked increase in the SSA measured by the BET‐method. For this sample, the SSA measured by PVA was considerably larger than the one that was obtained by the BET‐method and showed only a little change after removal of SOM.  相似文献   

7.
The adsorption technique using wollastonite has been applied for the removal of Cu(II) from aqueous solutions. The low concentration, high temperature and alkaline pH favor the removal of Cu(II). The Langmuir isotherm was used to represent the equilibrium data at different temperatures. The apparent heat of adsorption has been found to be 5.926 Cal mol?1. The uptake of Cu(II) is diffusion controlled and the mass transfer coefficient is 3.6 × 10?5 cm s?1. The maximum removal of Cu(II) in alkaline medium has been explained on the basis of the uptake of hydrolyzed adsorbate species by the active surface sites of adsorbent.  相似文献   

8.
An explanation is put forward for the shape of adsorption envelopes found for phosphate adsorption by various metallic oxides. The equation xm= C1 (μH3PO4+μ∑anions) is proposed, where μH3pO4 is the chemical potential of undissociated H3PO4; μ∑anions is the chemical potential of all phosphate anions considered as one. component; C1 is a constant that includes influences of surface charge, chemical affinity of the metal for phosphate, specific surface area, etc., and xmis the calculated Langmuir maximum adsorption of P at each pH. The dependence of C1 on the metal present in the oxide is shown.  相似文献   

9.
Aqueous 2-chloronapthalene was contacted with cast iron in batch systems, resulting in an initial rapid increase in the sorbed 2-chloronapthalene concentration (C s ) followed by a slow decline, and an initial rapid decline in the aqueous 2-chloronapthalene concentration (C a ) followed by a slower decline. The initial rapid partitioning of 2-chloronapthalene to the solid phase was due to its adsorption on elemental carbon present on the cast iron surface, while the residual aqueous phase 2-chloronapthalene underwent reductive dehalogenation at a slower rate through interaction with the metallic iron surface. The overall rate of change of total 2-chloronapthalene concentration (C T = C s +C a ) with time, i.e., (d/C T }{{d}t}) could be described by the expression,?k 1 ?M? (C a ) n , where M is the concentration of cast iron. The values of k 1 and n were determined to be 1.576 × 10?5 hr?1 g?1 iron L and 1.945 respectively. Equilibrium partitioning of 2-chloronapthalene between solid and aqueous phases could be described by a Freundlich isotherm, C s = K? [C a ] m , where m and K were determined to be 0.55 and 4.92 × 10?3 L g?1. Considering K to be the ratio of the adsorption (k 2) and desorption (k 3) rate constants, expressions were developed for describing the evolution of C s and C a with time. Putting k 3 = 1 hr?1 in these expressions resulted in adequate model fit to the experimental data. Napthalene was identified as the major dehalogenation by-product, with greater than 99 percent of the naphthalene produced partitioning to carbon present on the cast iron surface. No competition between 2-chloronapthalene and naphthalene for adsorption on the carbon surface was observed, suggesting non-specific adsorption of these compounds restricted only by the physical size of the molecules and the available carbon surface area.  相似文献   

10.
Abstract

Clinoptilolite, a zeolite mineral with a high cation exchange capacity and surface area, has ion‐exchange properties that can be utilized to adsorb NH4 +, protecting it from losses during composting of N‐rich animal manures. Ammonium adsorption by the natural zeolite clinoptilolite was studied to ascertain the effectiveness of the zeolite as an NH4 + adsorbent at pH 4, 5, 6, and 7. The NH4 + adsorption data were fitted to the one‐ and two‐surface Langmuir, Freundlich, and Temkin isotherms. All models described the NH4 +adsorption data successfully (r2≥0.939). The one‐surface Langmuir, Freundlich, and Temkin were converted to pH‐dependent forms. The amount of NH4 + adsorbed increased as pH and initial NH4 +concentration increased. From the one‐surface Langmuir isotherm, the NH4 +adsorption capacity (Xm) of the zeolite increased linearly with pH (r2=0.994), and was estimated to be 9,660 mg N kg‐1 at pH4, 11,220 mg N kg‐1 at pH 5, 12,720 mg N kg‐1 at pH 6, and 13,830 mg N kg‐1 at pH 7. The adsorption of higher amounts of NH4 +with increasing pH and initial NH4 +concentration is an important characteristic of the zeolite that can be beneficial to minimizing N‐losses via NH3volatilization during composting of N‐rich animal manures.  相似文献   

11.
Total S concentrations of Scots pine (Pinus sylvestris L.) needles studied in the Finnish subarctic (66–70°N, 24–30°E) in 1990/1992 ranged from 573 to 1153 μg g-1. Levels were found to be ≈ 900 μg g-1 (i.e. 1.3–1.8 times the ‘normal’ level of 500–700 μg g-1) in areas where the long-term ambient SO2 concentration was ≈ 2–5 μg m-3, particulate SO4 2- ≈ μg m-3 and total S deposition ≈ 0.5 g m-2. A statistically significant increase in needle total S concentrations was found towards the east, i.e. towards the smelters of the Kola Peninsula in Russia, which emit SO2. The increase in needle total S concentrations to over 900 μg g-1 close to the Russian border is thought to result mainly from exposure to high short-term SO2 concentrations. The results also suggest that wintertime S deposition may have an impact on the needle total S content. It is suggested that the UNECE long-term critical level of 15 μg SO2 m-3 for forestry in boreal and high mountain climates in Europe is too high for the pine forests in the extreme north, where the proportion of dry-deposited S may be 60–80%.  相似文献   

12.
Sericite is mica-based natural clay that is annealed at 800 ℃ for 4 h, followed by acid activation using 3.0 mol L-1HCl at 100℃. The interaction of cesium(I), Cs(I), with sericite could provide useful data for the study of soil erosion or mass water movement utilizing the natural radioactive Cs. In this study sericite and activated sericite were used to assess their suitability in the attenuation of Cs from the aquatic environment under both batch and column experiments. The surface morphological studies indicated that a disordered and heterogeneous surface structure was exhibited by the activated sericite, whereas the native sericite exhibited a compact and layered structure. The Brunauer-Emmett-Teller(BET) specific surface area results indicated a significant increase in the surface area due to the activation of sericite. The batch reactor data collected for various parametric studies revealed that an increase in p H(from 2.0 to 8.0) and sorbate concentration(from 10.0 to 100.0 mg L-1) apparently favored the attenuation of Cs(I). The timedependent sorption data revealed that Cs(I) uptake was very rapid, and it achieved its saturation value within just 50 min of contact.The kinetic modeling studies indicated that the uptake of Cs(I) followed a pseudo-second-order rate equation; hence, the attenuation capacity of these solids for Cs(I) was estimated to be 0.858 and 4.353 mg g-1for sericite and activated sericite solids, respectively.The adsorption isotherm modeling data showed a reasonably good applicability of the Freundlich model than the Langmuir model.The effect of background electrolyte concentrations(0.001 to 0.1 mol L-1) of Mg(NO3)2indicated that the presence of this electrolyte could not significantly affect the percent removal of Cs(I) by activated sericite. Furthermore, the fixed-bed column reactor operations were performed to obtain the breakthrough data, which were fitted well to the Thomas non-linear equation. Therefore, the loading capacity of Cs(I) was estimated to be 1.585 mg g-1at the initial influent Cs(I) concentration of 30.0 mg L-1at p H 5.0.  相似文献   

13.
Methodological and experimental studies of the abiotic uptake of gaseous substances by organic soils were performed. The static adsorption method of closed vessels for assessing the interaction of gases with the solid and liquid soil phases and the dynamic method of determining the sorption isotherms of gases by soils were analyzed. The theoretical substantiation of the methods and their practical implementations on the basis of a PGA-7 portable gas analyzer (Russia) were considered. Good agreement between the equilibrium sorption isotherms of the gases and the Langmuir model was revealed; for the real ranges of natural gas concentrations, this model can be reduced to the linear Henry equation. The limit values of the gas sorption (Langmuir monolayer capacity) are typical for dry samples; they vary from 670–4000 g/m3 for methane and oxygen to 20 000–25 000 g/m3 for carbon dioxide. The linear distribution coefficients of gases between the solid and gas phases of organic soils (Henry constants) are 8–18 units for poorly sorbed gases (O2, CH4) and 40–60 units for CO2. The kinetics of the chemicophysical uptake of gases by the soil studied is linear in character and obeys the relaxation kinetic model of the first order with the corresponding relaxation constants, which vary from 1 h ?1 in wet samples to 10 h ?1 in dry samples.  相似文献   

14.
In this study, high surface area porous carbons were synthesized by chemical activation using petroleum coke as the precursor and KOH as the activation agent. The pore structure of the as-synthesized activated carbons was characterized by nitrogen adsorption, and their CO2 sorption capacities were measured by a magnetic suspension balance at 1 and 10 bar, respectively. The effects of activated carbon preparation parameters (preheating temperature, preheating time, activation time, heating rate during the pyrolysis, and particle size of the precursor) on porous texture, CO2 adsorption capacity, and CO2/N2 selectivity of the activated products were investigated. It has been found that at 1 bar, the CO2 adsorption capacity is determined by the micropore contribution, i.e., the ratio between micropore surface area and Brunauer–Emmett–Teller (BET) surface area of the sorbents, while at 10 bar, CO2 adsorption capacity is related to the BET surface area of the activated products. The maximum CO2 adsorption uptake of 15.1 wt% together with CO2/N2 selectivity of 9.4 at 1 bar were obtained for a sample activated at 700 °C indicating its high potential in the capture of CO2.  相似文献   

15.
Eight samples of goethite ranging in surface area from 18 to 132 m2 g-1 were mixed with phosphate at a range of pH values for periods which ranged from 0·5 h to 6 weeks. The sample with a surface area of 18 m2 g-1 had been hydrothermally treated to improve its crystallinity. Its rate of reaction with phosphate depended on pH but was complete within a day. Its maximum observed reaction was close to the theoretical maximum for surface adsorption of 2·5 μmol m?2. For the other samples, phosphate continued to react for up to 3 weeks and exceeded the value of 2·5 μmole m?2. The duration and extent of the reaction depended on the crystallinity of the goethite. The results were closely described by a model in which the phosphate ions were initially adsorbed on to charged external surfaces. The phosphate ions then diffused into the particles. This was closely described using equations for diffusion into a cylinder. Samples of goethite which had been loaded with phosphate dissolved more slowly in HCl, and had a longer lag phase, than phosphate-free goethite. For the hydrothermally treated goethite, HCl removed much of the phosphate when only a small proportion of the iron had been dissolved. For a poorly crystallized goethite, it was necessary to dissolve much more of the iron to obtain a similar removal of phosphate. Brief treatment with NaOH removed most of the phosphate from the hydrothermally treated goethite but only half the phosphate from a poorly crystallized goethite. These results are consistent with the idea that phosphate ions were not only bound on external surface sites but had also penetrated into meso- and micro-pores between the domains of the goethite crystals and were then adsorbed on internal surface sites. This penetration tied the domains together more firmly thus increasing the lag phase for dissolution. Differences between sites for phosphate adsorption are therefore caused mainly by their location on either external or internal sites. Models that ignore this are incomplete.  相似文献   

16.
The aim of this study was to measure the in situ soil CO2 flux from grassland, afforested land and reclaimed coalmine overburden dumps by using the automated soil CO2 flux system (LICOR‐8100® infrared gas analyzer, LICOR Inc., Lincoln, NE). The highest soil CO2 flux was observed in natural grassland (11·16 µmol CO2 m−2s−1), whereas the flux was reduced by 38 and 59 per cent in mowed site and at 15‐cm depth, respectively. The flux from afforested area was found 5·70 µmol CO2 m−2s−1, which is 50 per cent lower than natural grassland. In the reclaimed coalmine overburden dumps, the average flux under tree plantation was found to be lowest in winter and summer (0·89–1·12 µmol CO2 m−2s−1) and highest during late monsoon (3–3·5 µmol CO2 m−2s−1). During late monsoon, the moisture content was found to be higher (6–7·5 per cent), which leads to higher microbial activity and decomposition. In the same area under grass cover, soil CO2 flux was found to be higher (8·94 µmol CO2 m−2s−1) compared with tree plantation areas because of higher root respiration and microbial activity. The rate of CO2 flux was found to be determined predominantly by soil moisture and soil temperature. Our study indicates that the forest ecosystem plays a crucial role in combating global warming than grassland; however, to reduce CO2 flux from grassland, mowing is necessary. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

17.
Sepiolite has a microporous structure the pores of which may be penetrated to differing extents by molecules of different gases. A study has been made of the adsorption of CO2 on outgassed sepiolite (from Amboseli, Tanzania) at 193°, 209·7°, 273·2°, and 298·2 °K using a gravimetric method. Values of the surface area of sepiolite were calculated from BET (Brunauer, Emmett, and Teller) and Kaganer plots of results, assuming molecular areas for CO2 based on extrapolated liquid densities. There were only relatively small deviations from a mean value of 279 m2/g. However, the values were much lower than those previously determined by adsorption of N2 and of other gases. It is suggested that CO2 adsorbed at these temperatures should be assumed to be in the liquid state, but that the usual method of calculating the molecular areas of adsorbed CO2 from the liquid densities at these temperatures yields values which are too low. Molecular areas of 20·8 Å2 at 193 °K and 23·4 Å2 at 209·7 °K are preferred. Isosteric heats of adsorption at different coverages were calculated from the isotherms. The results indicated heterogeneity of the surface, with decreases in the values of the heat of adsorption occurring at low coverages and in the‘monolayer region’. They compare well with values calculated from the BET equation.  相似文献   

18.
The effects of various experimental parameters on adsorption of Zn2+ metal ion from its aqueous solution by castor seed hull and also by activated carbon have been investigated using batch adsorption experiments. It has been found that the amount of zinc adsorbed per unit mass of the hull increases with the initial metal ion concentration, contact time, solution pH and with the amount of the adsorbent. Kinetic experiments clearly indicate that adsorption of zinc on both castor hull and activated carbon is a three-step process??a rapid adsorption of the metal ion, a transition phase, and an almost flat plateau. This has also been confirmed by the intraparticle diffusion model. It has also been found that the zinc adsorption process followed pseudo-second order kinetics. The kinetic parameters including rate constants have been determined at different initial metal ion concentration, pH, amount, and type of adsorbent, respectively. The Langmuir and Freundlich adsorption isotherm models have been used to interpret the equilibrium adsorption data. The Langmuir model yields better correlation coefficients. The monolayer adsorption capacities (q m ) of castor hull and activated carbon have been compared with those for others reported in the literature. The value of separation factor (R L ) derived from the Langmuir model gives an indication of favorable adsorption. Finally, from comparative studies, it has been found that castor hull is a potentially attractive adsorbent as compared to commercial activated carbon for the removal of zinc from aqueus effluents.  相似文献   

19.
For forty-one soils (pH > 5.0) from southern England and eastern Australia, the Langmuir equation was an excellent model for describing P adsorption from solutions < 10-3M P, if it was assumed that adsorption occurs on two types of surface of contrasting bonding energies. For most of these soils, which were relatively undersaturated with P, this equation may be written as: where x = adsorption, k = adsorption/desorption equilibrium constant, xm= monolayer adsorption capacity, and c = equilibrium solution concentration. The relative magnitude of the parameters for each surface were approximately: xm= 0.3 x″m=0.3 and k′= 100 k. More than 90 per cent of the native adsorbed P occurs on the high-energy surface in most soils.  相似文献   

20.
The present study aims to establish the annual NH3 deposition to an inland heathland in Denmark using a micro-meterological approach with passive wind-vane flux samplers. The integrating samplers were replaced at weekly intervals from May 1995 to May 1996. The average concentration, 2.05 μg m-3 at the heathland is at a moderate level when compared to heathlands in other parts of Europe. The average deposition velocity was 0.83 cm s-1 which is within the range of depositon velocities found for other heathlands in Europe. The average canopy resistance was found to be relatively high, 61 s -1. The measurements yielded a total NH3-N deposition of 2.4 (± 0.9) kg ha-1 yr-1 with a data coverage of 71% for 1995/1996. In 40% of this time the flux is regarded as zero because the flux is not significant different from zero. In 60% of this time the significant fluxes varied from –0.052 μg m-2 s-1 (deposition equal 16.4 kg N ha-1 yr-1) to 0.089 μg m-2 s-1 (emission equal 28.2 kg N ha-1 yr-1). The method is only able to direct measure significant fluxes down to the equivalence of 0.010 μg m-2 s-1 (approximately 3.2 kg ha-1 yr-1). Therefore the exact deposition cannot be determined by the applied method at very low deposition sites such as a coastal heathland in Denmark. In a high-deposition area as in the central Netherlands the method gave significant fluxes with a 100% data coverage for a two month period.  相似文献   

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