载铜球形活性炭的制备及其吸附脱硫性能的研究

以122型弱酸性酚醛系阳离子交换树脂为炭前驱体,经过Cu²⁺交换、炭化和CO₂活化等过程制备得到负载金属铜的球形活性炭,对其进行了SEM、XRD、AAS和BET表征,采用动态吸附实验研究了其对模拟汽油中噻吩类硫化物的吸附性能,并且考察了甲苯和环己烯对其吸附性能的影响,对吸附脱硫机理进行了初步研究。结果表明,载铜球形活性炭上Cu以单质形态存在,并主要与硫原子产生配位作用,提高了对噻吩类硫化物的吸附性能,对噻吩(T)、3-甲基噻吩(MT)、2,5-二甲基噻吩(DMT)和苯并噻吩(BT)的饱和硫容依次为0.938、1.230、1.581和3.744 mg/g,吸附选择性依次为T < MT < DMT < BT。模拟汽油中加入甲苯和环己烯后,饱和硫容分别下降了77%和56%,这是甲苯和环己烯通过π电子与Cu发生作用,从而与硫化物产生竞争吸附导致的。     

Preparation and characterization of nanocomposite,silica aerogel,activated carbon and its adsorption properties for Cd (II) ions from aqueous solution

A novel composite adsorbent, silica aerogel activated carbon was synthesized by sol-gel process at ambient pressure drying method. The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Nitrogen adsorption/desorption isotherms (BET).In the present study, the mentioned adsorbent was used moderately for the removal of cadmium ions from aqueous solutions and was compared with two other adsorbents of cadmium, activated carbon and silica aerogel. The experiments of Cd adsorption by adsorbents were performed at different initial ion concentrations, pH of the solution, adsorption temperature, adsorbent dosage and contact time. Moreover, the optimum pH for the adsorption was found to be 6.0 with the corresponding adsorbent dosage level of 0.1 g at 60 °C temperature. Subsequently, the equilibrium was achieved for Cd with 120 min of contact time.Consequently, the results show that using this composite adsorbent could remove more than 60% of Cd under optimum experimental conditions. Langmuir and Freundlich isotherm model was applied to analyze the data, in which the adsorption equilibrium data were correlated well with the Freundlich isotherm model and the equilibrium adsorption capacity (q_e) was found to be 0.384 mg/g in the 3 mg/L solution of cadmium.     

Adsorption of reactive brilliant red K-2BP on activated carbon developed from sewage sludge

Activated carbon was prepared from the sewage sludge of municipal wastewater treatment plant by chemical activation (activation reagent is ZnCl₂) and was used for the adsorption of dye (reactive brilliant red K-2BP). The impact of adsorbent amount, adsorption time and pH value on adsorption effect, the adsorption kinetics, and the adsorption thermodynamics were discussed according to batch adsorption tests. The results indicated that the activated carbon developed from sewage sludge (ACSS), which was mesoporous, possessed opened porous structures. The iodine number of the ACSS was 326 mg·g⁻¹. The rate of achievement was 51.31%. The BET surface area was 298 m²·g⁻¹ and the contents of heavy metals in the leachate didn’t exceed the contents limit. The adsorption kinetics of reactive brilliant red K-2BP on the ACSS was accorded with the two-step kinetics rate equation and pseudo-second-order kinetics equation. Compared to the Freundlich isotherm equation, the Langmuir isotherm equation showed better applicability for the adsorption. The adsorption which was favorable was an endothermic (enthalpy ΔH > 0) and spontaneous (free energy ΔG < 0) process and was accompanied by an increase in entropy (ΔS > 0). __________ Translated from Journal of Shandong University (Natural Science), 2007, 42(3): 64–70 [译自: 山东大学学报(理学版)]     

Enzymes immobilized on montmorillonite: comparison of performance in batch and packed-bed reactors

Summary The enzymes a-amylase, invertase and glucoamylase were immobilized on acid activated montmorillonite using two techniques, viz. adsorption and covalent binding, and their activities were tested in a batch and packed-bed reactor and were compared. The packed-bed reactor showed an improved performance for all immobilized enzymes, which was attributed to lowering of diffusional restrictions to mass transfer. Lower activity in case of batch reactor for immobilized invertase was due to a combined effect of loss of native conformation of enzyme on account of immobilization and mass transfer resistances due to improper diffusion of substrate to the active site of enzyme. For immobilized glucoamylase, the packed-bed reactor demonstrated exceptionally high activity that was very close to the free enzyme. Covalently bound glucoamylase showed higher activity than the free enzyme.     

Tea-industry waste activated carbon, as a novel adsorbent, for separation, preconcentration and speciation of chromium

Activated carbon was produced from tea-industry wastes (TIWAC) and employed as a low cost and effective solid phase material for the separation, preconcentration and speciation of chromium species without using a complexing agent, prior to determination by flame atomic absorption spectrometry (FAAS). The characterization of TIWAC was performed by utilizing several techniques such as Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), and elemental analysis. The adsorption experiments were conducted in a batch adsorption technique. Under the experimental conditions, Cr(VI) adsorption amount was nearly equal to zero, however the adsorption percentage of Cr(III) was in the range of 95–100%. Therefore total chromium was determined after the reduction of Cr(VI) to Cr(III) and Cr(VI) was calculated by subtracting Cr(III) concentration from total chromium concentration. The suitable conditions for adsorption and speciation processes were evaluated in terms of pH, eluent type and volume, TIWAC concentration, adsorption and desorption contact time, etc. Adsorption capacity of TIWAC was found to be 61.0 mg g⁻¹. The detection limit for Cr(III) was found to be 0.27 μg L⁻¹ and the preconcentration factor was 50 for 200 mL of sample volume. The procedure was applied to the determination and speciation of chromium in stream, tap and sea water. Also, the proposed method was applied to total chromium preconcentration in microwave digested tobacco and dried eggplant samples with satisfactory results. The method was validated by analyzing certified reference materials (CRM-TMDW-500 Drinking Water and CRM-SA-C Sandy Soil C) and the results were in good agreement with the certified values.     

活性炭的表面处理对二苯并噻吩催化氧化脱除的影响

将一种木质活性炭经过三种表面处理,即高锰酸钾稀硫酸溶液液相氧化、浓硝酸液相氧化和350℃低温气相氧化处理。实验所选活性炭及相应的表面改性炭使用氮气吸附和Boehm滴定分别进行了结构性质和表面化学表征。研究了所选活性炭和相应的表面改性炭催化过氧化氢氧化脱除二苯并噻吩（DBT）。实验结果表明,活性炭表面化学对二苯并噻吩的氧化脱除影响很大;炭表面化学对DBT吸附脱除的影响不同于对DBT氧化脱除的影响,表面酸性越强越有利于DBT的吸附;表面羰基能加速过氧化氢产生自由基,表面羰基量的增加明显有利于DBT的氧化脱除。活性炭经过热处理后,在二苯并噻吩的氧化脱除中催化活性明显增加,正辛烷溶液中硫的体积质量从0.556g·L-1降到0.009g·L-1。     

Comparison of three digestion methods for the determination of the aqua regia soluble content of lead,cadmium and chromium in sewage sludges by ETAAS

A procedure for the determination of the aqua regia soluble content of lead, cadmium and chromium in a sewage sludge reference material (CRM 145R) by electrothermal atomic absorption spectrometry (ETAAS) is described. A comparison of the dissolution procedure proposed in the certification report, to an oven-assisted digestion and a proposed microwave digestion procedure is performed. In the ETAAS method developed, 1 g of Pt proved to be an appropriate modifier for each of the above heavy metals. Possible sources of error at each analytical step are addressed. The metal contents obtained with the proposed method are in a good agreement at 95% significance level with the certified values given for CRM 145R.     

Square wave voltammetry based on determination of copper (II) ions by polyluteolin- and polykaempferol-modified electrodes

Applicability of square wave voltammetry for the determination of Cu(II) ions by PolyLut/GC and PolyKae/GC electrodes was evaluated in this study. For this luteolin and kaempferol were electrochemically polymerized on glassy carbon (GC) electrode surface in order to get polyluteolin and polykaempferol-modified glassy carbon electrodes (PolyLut/GC and PolyKae/GC, correspondingly). The formation of polyphenol layer on the GC electrode surface was evidenced by atomic force microscopy. Square wave voltammetry was found to be more sensitive in comparison with differential pulse voltammetry. It was determined that PolyLut/GC and PolyKae/GC electrodes offered great sensitivity towards Cu(II) ions with very low limit of detection, good reproducibility, sufficient stability and excellent selectivity of analytical signal.     

Adsorption of metal ions by microwave assisted grafting of cross‐linked chitosan beads. Equilibrium,isotherm, thermodynamic and desorption studies

Chemical modification of chitosan has become increasingly essential due to chitosan versatility that enables the material to be easily modified in a way of increasing its properties in adsorption processes. In this investigation, chitosan solution was cross‐linked with glutaraldehyde the cross‐linked solution was used in producing the beads and thereafter grafted with ethylene acrylic acid. The chemical functionalities of the beads were obtained by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), X‐ray diffraction (XRD) and Thermogravimetric analysis (TGA). Adsorption of Pb²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Cr⁶⁺ and Cd²⁺ ions from single component aqueous mixture by grafted cross‐linked chitosan beads (GXXB) was studied as a function of pH, temperature, initial concentration, contact time, agitation speed and ionic strength. Equilibrium data was obtained from the adsorption experiment, the data were applied in isotherm, thermodynamics and kinetic studies. The Langmuir, Temkin and Dubinin‐kaganer‐Radushkevich (DKR) model were successful in describing the isotherm data for the considered metal ions while the Freundlich model was not efficient in describing the experimental data. Pseudo‐second order and intra‐particle model described the kinetic data quite well. Thermodynamic parameters such as Gibb's free energy change (?G^o), enthalpy change (?H^o) and entropy change (?S^o) were calculated and the results showed the adsorption of Pb²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Cr⁶⁺ and Cd²⁺ ions onto GXXB is spontaneous and endothermic in nature. Regeneration of the used adsorbent was effective for the studied metal ions.     

Monitoring of Fe,Mn, Cu,Pb and Cd levels in two brown macroalgae from the Bulgarian Black Sea coast

Heavy metal contents (Fe, Mn, Cu, Pb and Cd) were determined in two brown macroalgal species (Cystoseira crinita and Cystoseira barbata). Samples were collected during six seasons from spring 1996 to summer 2000 from five different sites of the Bulgarian Black Sea coastal zone – Tuzlata, Ravda, Sozopol, Ahtopol and Sinemoretz. The local and seasonal metal distribution and their variations were examined.

The data obtained indicate that the two investigated species demonstrate various degrees of metal accumulation and can be used as indicators for the type and quantity of anthropogenic contamination in marine ecosystems.     

Effects of activation conditions on the structural and adsorption characteristics of pinecones derived activated carbons

This study was conducted to understand and optimize the activation process for the production of a low-cost activated carbon (AC) using a renewable and plentiful biomass waste, pinecones. This was achieved by tracking the changes in porous structure, surface chemistry and adsorption properties of the AC produced using different activating agents, activation temperatures, holding times and heating rates. Generally, produced ACs were predominantly microporous with small external surface area and were different in terms of H/C and O/C ratios. Study of Pb²⁺ cations adsorption on these samples proved the high affinity of the pinecones derived ACs to this cation. The best adsorption behaviour was recognized in sample prepared by impregnation with H₃PO₄ at weight ratio of 2, then heating at 400?°C for 2?h at 5?°C/min heating rate. This sample possessed the highest BET surface area (1335 m²/g). The adsorption process obeyed the pseudo-first-order and Freundlich model slightly better than the pseudo-second-order kinetics and Langmuir model. The high Langmuir maximum adsorption capacity of 418?mg/g supports the applicability of the produced AC for the removal of Pb²⁺ cations from wastewater.     

Development of a four-zone carousel process packed with metal ion-imprinted polymer for continuous separation of copper ions from manganese ions,cobalt ions,and the constituent metal ions of the buffer solution used as eluent

A three-zone carousel process, in which Cu(II)-imprinted polymer (Cu-MIP) and a buffer solution were employed as adsorbent and eluent respectively, has been developed previously for continuous separation of Cu²⁺ (product) from Mn²⁺ and Co²⁺ (impurities). Although this process was reported to be successful in the aforementioned separation task, the way of using a buffer solution as eluent made it inevitable that the product stream included the buffer-related metal ions (i.e., the constituent metal ions of the buffer solution) as well as copper ions. For a more perfect recovery of copper ions, it would be necessary to improve the previous carousel process such that it can remove the buffer-related metal ions from copper ions while maintaining the previous function of separating copper ions from the other 2 impure heavy-metal ions. This improvement was made in this study by proposing a four-zone carousel process based on the following strategy: (1) the addition of one more zone for performing the two-step re-equilibration tasks and (2) the use of water as the eluent of the washing step in the separation zone. The operating conditions of such a proposed process were determined on the basis of the data from a series of single-column experiments. Under the determined operating conditions, 3 runs of carousel experiments were carried out. The results of these experiments revealed that the feed-loading time was a key parameter affecting the performance of the proposed process. Consequently, the continuous separation of copper ions from both the impure heavy-metal ions and the buffer-related metal ions could be achieved with a purity of 91.9% and a yield of 92.8% by using the proposed carousel process based on a properly chosen feed-loading time.     

Effects of heavy metals and oxalate on the zeta potential of magnetite

Zeta potential is a function of surface coverage by charged species at a given pH, and it is theoretically determined by the activity of the species in solution. The zeta potentials of particles occurring in soils, such as clay and iron oxide minerals, directly affect the efficiency of the electrokinetic soil remediation. In this study, zeta potential of natural magnetite was studied by conducting electrophoretic mobility measurements in single and binary solution systems. It was shown that adsorption of charged species of Co(2+), Ni(2+), Cu(2+), Zn(2+), Pb(2+), and Cd(2+) and precipitation of their hydroxides at the mineral surface are dominant processes in the charging of the surface in high alkaline suspensions. Taking Pb(2+) as an example, three different mechanisms were proposed for its effect on the surface charge: if pH<5, competitive adsorption with H(3)O(+); if 56, precipitation of heavy metal hydroxides prevails. Oxalate anion changed the associated surface charge by neutralizing surface positive charges by complexing with iron at the surface, and ultimately reversed the surface to a negative zeta potential. Therefore the adsorption ability of heavy metal ions ultimately changed in the presence of oxalate ion. The changes in the zeta potentials of the magnetite suspensions with solution pH before and after adsorption were utilized to estimate the adsorption ability of heavy metal ions. The mechanisms for heavy metals and oxalate adsorption on magnetite were discussed in the view of the experimental results and published data.     

修饰沙粒对Pb(Ⅱ)的吸附性及其在痕量Pb(Ⅱ)分离富集与测定中的应用

本文用不同浓度的氢氧化钠溶液修饰天然沙粒并通过扫描电镜、静态氮吸附和红外光谱法考察了修饰天然沙粒的表面结构、比表面积和功能基团,优化了修饰条件;以修饰天然沙粒为填料制备分离富集微柱,采用FAAS着重研究了修饰沙粒对Pb2+的动态吸附及其在痕量Pb2+分离富集和测定中的应用;结果表明:天然沙粒被修饰后其表面形貌、比表面积、表面孔体积和粒径分布发生变化,表面变得更粗糙,孔体积和比表面积增大,硅羟基红外吸收峰强度也明显增强;其比表面积为12.55m2/g,平均孔(坑)径为25.29nm,平均孔体积48.04mm3/g(D8.3 nm);在室温下,溶液pH为5.5,上样流速为1.50m L·min-1时,修饰天然沙粒对Pb2+的动态吸附量可达到32.6 mg·g-1,吸附率为93.6%,选用0.5mol·L-1的盐酸溶液以3.0m L·min-1流速进行洗脱,洗脱率为97%;适用于痕量Pb2+的分离富集和测定,结果令人满意。     

Speciation of trace metals in natural waters: the influence of an adsorbed layer of natural organic matter (NOM) on voltammetric behaviour of copper

The influence of an adsorbed layer of the natural organic matter (NOM) on voltammetric behaviour of copper on a mercury drop electrode in natural water samples was studied. The adsorption of NOM strongly affects the differential pulse anodic stripping voltammogram (DPASV) of copper, leading to its distortion. Phase sensitive ac voltammetry confirmed that desorption of adsorbed NOM occurs in general at accumulation potentials more negative than −1.4 V. Accordingly, an application of negative potential (−1.6 V) for a very short time at the end of the accumulation time (1% of total accumulation time) to remove the adsorbed NOM was introduced in the measuring procedure. Using this protocol, a well-resolved peak without interferences was obtained. It was shown that stripping chronopotentiogram of copper (SCP) in the depletive mode is influenced by the adsorbed layer in the same manner as DPASV. The influence of the adsorbed NOM on pseudopolarographic measurements of copper and on determination of copper complexing capacity (CuCC) was demonstrated. A shift of the peak potential and the change of the half-peak width on the accumulation potential (for pseudopolarography) and on copper concentration in solution (for CuCC) were observed. By applying a desorption step these effects vanished, yielding different final results.     

Removal of chemical oxygen demand,nitrogen, and heavy metals using a sequenced anaerobic-aerobic treatment of landfill leachates at 10-30 degrees C

As a first step of treatment of landfill leachates (total chemical oxygen demand [COD]: 1.43–3.81 g/L; total nitrogen: 90–162 mg/L), performance of laboratory upflow anaerobic sludge bed reactors was investigated under mesophilic (30°C), submesophilic (20°C), and psychrophilic (10°C) conditions. Under hydraulic retention times (HRTs) of about 0.3 d, when the average organic loading rates (OLRs) were about 5 g of COD/(L·d), the total COD removal accounted for 81% (on average) with the effluent concentrations close to the anaerobic biodegradability limit (0.25 g of COD/L) for mesophilic and submesophilic regimes. The psychrophilic treatment conducted under an average HRT of 0.34 d and an average OLR of 4.22 g of ducted under an average HRT of 0.34 d and an average OLR of 4.22 g of COD/(L·d) showed a total COD removal of 47%, giving effluents (0.75 g of COD/L) more suitable for subsequent biologic nitrogen removal. All three anaerobic regimes used for leachate treatment were quite efficient for elimination of heavy metals (Fe, Zn, Cu, Pb, Cd) by concomitant precipitation in the form of insoluble sulfides inside the sludge bed. The application of aerobic/anoxic biofilter as a sole polishing step for psychrophilic anaerobic effluents was acceptable for elimination of biodegradable COD and nitrogen approaching the current standards for direct discharge of treated waste-water.     

A voltammetric sensor for simultaneous determination of lead,cadmium and zinc on an activated carbon fiber rod

A simple, low cost and sensitive voltammetric sensor was developed for the simultaneous detection of Pb²⁺, Cd²⁺, and Zn²⁺ based on a disposable carbon fiber rod (CFR). The important factors to enhance the sensing property were creation of a clean surface by dealing with CFR at a high potential and electrochemical deposition of Bi film to improve the accumulation of heavy metal ions.     

Comparison of original and modified BCR sequential extraction procedures for the fractionation of copper, iron, lead, manganese and zinc in soils and sediments

This article describes a detailed comparison between the original BCR sequential extraction procedure, step 2 of which involves treatment with 0.1 mol l⁻¹ hydroxylammonium chloride at pH 2, and the revised BCR procedure (step 2: 0.5 mol l⁻¹ hydroxylammonium chloride at pH 1.5). An intermediate protocol was also evaluated in which 0.5 mol l⁻¹ hydroxylammonium chloride at pH 2 was used. The procedures were applied to five soil and sediment substrates: a sewage sludge-amended soil, two different industrially contaminated soils, a river sediment and an inter-tidal sediment. Extractable iron and manganese concentrations were measured to assess the effects of the procedural modifications on dissolution of the reducible matrix components. Trace elements copper, lead and zinc were also determined. Statistical analysis (two-tailed t-tests at 95% confidence interval) indicated that recovery of iron in step 2 was not markedly enhanced when the intermediate protocol was used. However, significantly greater amounts were isolated with the revised BCR scheme than with the original procedure. Copper behaved similarly to iron. Lead recoveries were increased by use of both modified protocols, with the greatest effect occurring for the revised BCR extraction. In contrast, manganese and zinc extraction did not vary markedly between procedures. The work indicates that the revised BCR sequential extraction provides better attack on the iron-based components of the reducible matrix for a wide range of soils and sediments.     

Calibrationless determination of cadmium, lead and copper in rain samples by stripping voltammetry at mercury microelectrodes: Effect of natural convection on the deposition step

Mercury microelectrodes were prepared by ex situ deposition of Hg onto Pt microdiscs. By exploiting the known properties of microelectrodes in stripping analysis, an absolute method based on a simple equation derived from the stripping charge and the microelectrode steady-state current was assessed for the simultaneous quantification of Cd²⁺, Pb²⁺ and Cu²⁺ concentrations. The method was tested with synthetic solutions containing known amounts of Cd²⁺, Pb²⁺ and Cu²⁺. Then, it was used to determine the labile and total fractions of these metal ions in rain samples. The labile fractions were measured from samples at their natural pH while the total concentrations were determined from samples at pH=2.     

Effect of chromium(III) and of other ions on the absorptiometric determination of copper with 2, 2'-biquinolyl

In the determination of small amounts of copper in certain alloys by liquid-liquid extraction of the bis-chelate of copper(I) with 2, 2'-biquinolyl, recovery of copper has been reported to be low when chromium(III) is present. The adverse effect of chromium(III) could be overcome by adding iron(II). It is now shown that the inhibiting effect of chromium is attributable to the formation of a kinetically inert ternary complex of chromium(III), copper(II) and citrate ions containing an equal number of atoms of each of the two metals. Copper can be displaced from this complex by any of the transition cations Mn(II), Fe(II), Co(II), Ni(II) and Zn(II). Zinc is shown to form a ternary complex formally analogous to that of copper. The formation of the ternary complexes has been studied polarographically. The formation of binuclear complexes of various hydroxy-acids is reviewed and a probable structure for the ternary complex is proposed which explains its stability and kinetic inertness. Analogies are drawn between this complex and ternary complexes of UO(2)(VI)-Al(III)-citrate and Cu(II)-Al(III)-tartrate which also cause interference in established analytical procedures.