Dynamic Adsorption of Heavy Metals under Various Incineration Temperatures

Previous studies have indicated that an effective control technology, for heavy metal emissions from incinerators, is to use solid sorbents to capture metals by physical deposition and chemical adsorption. The controlling efficiency is affected by the kind and size of sorbents, the operating temperature, and the specific compositions of the waste. However, the dynamic adsorption behavior of heavy metals on sorbents during incineration is rarely discussed, because it is difficult to analyze and identify trace metals at high temperatures. The main objective of this study is to investigate the dynamic adsorption behavior of Cr, Cu, Pb, and Cd on sorbents (silica sand with limestone) at different operating temperatures (600, 700, and 800°C) and to find the adsorption saturation point of the sorbents during fluidized bed incineration. This will help us to determine when the sorbents should be renewed and investigate the adsorption mechanism. The results show that the adsorption saturation points of three of the four metals were: (1) Cr, 1.4 mg∕g at 600°C, 1.04 mg∕g at 800°C; (2) Pb, 16.08 mg∕g at 600°C, 12 mg∕g at 800°C; and (3) Cu, 10.6 mg∕g at 600°C, 5.34 mg∕g at 700°C. The adsorption capacity follows the sequence of Pb > Cu > Cr > Cd.     

Removal of Heavy Metal Ions by Waste Biomass of Saccharomyces Cerevisiae

The kinetics, equilibriums, and thermodynamics of metal ion (Pb2+, Ag2+, Cu2+, Zn2+, Co2+, Sr2+, and Cs+) biosorption by the waste yeast cells of Saccharomyces cerevisiae from a local brewery were investigated. The results showed that the biosorption of these metal ions on the biomass was a very rapid process, following the pseudo-second-order equation gave the better fitting results in describing the kinetic data than the pseudo-first-order equation. The equilibrium data could be fitted well with the Langmuir model. The maximum sorption capacity obtained from the Langmuir model followed Pb>Ag>Cu>Zn>Co>Sr>Cs (based on mmol?g?1). The biosorption process by the yeast was favorable for these metal ions removal according to the constant separation factor (0相似文献   

New procedure for analysing drug binding data, exemplified by warfarin binding to human serum albumin

Determination of binding constants for multiple binding of a ligand usually results in highly variable figures. We have found that the variations depend mainly upon cooperativity of ligand binding, and that cooperativity is generally absent on binding to human serum albumin. When this is taken into account it becomes possible to obtain binding constants with only slight variation. A computerized curve fitting procedure for analysing binding data has been established consisting of the following steps. (1) Fitting of Scatchard's equation to observed binding equilibrium data to obtain a best-fit set of Scatchard binding constants. (2) Repetition of the fitting procedure, not to obtain a best fit but to generate 30 acceptable sets of Scatchard binding constants. (3) Fitting of Adair's equation to the observed points to obtain a best fit. If the sum of weighted and squared deviations is significantly smaller than the fitting of Scatchard's equation, cooperativity should be considered. If not, cooperativity cannot be demonstrated and the binding constants obtained by fitting Scatchard's equation can be accepted, with the variations found. (4) Final transformation of all Scatchard constants to Adair's. To illustrate the method warfarin data obtained by equilibrium dialysis was used.     

Oxidation of 2-Chlorophenol in Water by Ultrasound∕Fenton Method

One of the toxic and refractory pollutants formed during the color removal of fertilizer, chemical, and petroleum industrial effluents by chlorine is 2-chlorophenol (2-cp). The objective of this study is to investigate the effect of H2O2 and Fe2+ dosages on the decomposition of 2-cp using a coupled ultrasound∕Fe2+∕H2O2 process. The extent of 2-cp decomposition and mineralization depends on the dosages of H2O2 and Fe2+. More than 99% of 2-cp was decomposed and 86% of 2-cp was mineralized using the ultrasound∕Fe2+∕H2O2 process at Fe2+ of 10 mg∕L and H2O2 of 500 mg∕L. Oxidation-reduction potential (ORP) monitoring is a useful method for determining the decomposition efficiency of the target compound. There was a slight increase in the ORP values with increasing Fe2+ dosages, and an apparent increase with increasing H2O2 dosages was observed. The major intermediate formed during the decomposition of 2-cp was 2-chloro-p-benzoquinone. It was also readily decomposed using the coupled ultrasound∕Fe2+∕H2O2 process.     

Site-directed mutagenesis of charged and potentially proton-carrying residues in the beta subunit of the proton-translocating nicotinamide nucleotide transhydrogenase from Escherichia coli. Characterization of the beta H91, beta D392, and beta K424 mutants

Conserved and semiconserved acidic and basic residues of the beta subunit of the proton-pumping nicotinamide nucleotide transhydrogenase from Escherichia coli potentially involved in proton pumping were investigated. Out of 16 charged residues studied, 6 have not been previously investigated. The most dramatic effects of mutation were observed with beta H91, beta D392, and beta K424. beta H91E showed a pronounced shift of the pH optimum for both reduction of thio-NADP+ by NADH (forward reaction) and reduction of 3-acetylpyridine-NAD+ by NADPH (reverse reaction) to lower pH. This mutant catalyzed a cyclic reduction of 3-acetylpyridine-NAD+ by NADH in the presence of NADP(H) with a pH profile also shifted toward a lower pH. These results are consistent with a mechanism where the normal forward and reverse reactions are indeed limited by protonation/deprotonation of beta H91. The cyclic reaction was affected by mutations of beta H91, probably through conformational changes involving the active NADP(H) site. The beta D392A mutant was inactive with regard to forward and reverse reactions, but showed a wild-type-like pH dependence for the partly active cyclic reaction. However, Km,app for NADP(H) in this reaction was elevated 50-100-fold, suggesting that beta D392 is located in or near the NADP(H)-binding site. Transhydrogenases contain a conserved beta K424-beta R425-beta S426 sequence that has been proposed to be important for NADP(H) binding. beta K424R was strongly inhibited and showed an 18-fold increased Km,app for NADPH in the reverse reaction as compared to wild type. Consequently, this mutation affected all NADP(H)-linked activities and essentially abolished the unspecific interaction of NAD(H) with this site. The pH dependences of the forward and reverse reactions, as well as the cyclic reaction, were shifted to a lower pH as compared to the wild-type enzyme, and the salt dependence was also altered.     

Empirical Partitioning Leach Model for Solidified∕Stabilized Wastes

A model has been developed to describe dynamic leaching of metal contaminants from solidified wastes using data for calibration that are taken only from batch tests. The model describes the three major factors affecting leaching: (1) acid∕base reactions that determine the pH within the waste; (2) pH-dependent reactions that determine whether the contaminants are in mobile or immobile forms; and (3) diffusion that transports mobile contaminants from the waste. Acid∕base reactions and mobilization∕immobilization reactions of contaminants are described by empirical equations calibrated from batch equilibrium tests. Precipitation or sorption reactions are used to describe partitioning of contaminants among mobile and immobile forms. Fickian diffusion is used to describe transport of soluble compounds. Model predictions for observed diffusivities of copper, chromium, lead, and zinc agreed well with the experimental data obtained from dynamic leaching tests. Little difference was observed in model predictions when contaminant immobilization was assumed to be caused by precipitation or by sorption. Model simulations indicate that the assumption of an infinite bath may not apply to dynamic leach tests when contaminants are strongly immobilized.     

H2O2∕UV-C and Fe2+∕H2O2∕UV-C versus TiO2∕UV-A Treatment for Reactive Dye Wastewater

This study investigated the advanced oxidation of commonly used reactive dyestuffs in exhausted dye-bath effluents in homogeneous (H2O2∕UV-C and photo-Fenton) and heterogeneous (TiO2∕UV-A) media. Photocatalytic treatment efficiencies of two different TiO2 powders (PC 500 and Mikroanatas) and the platinized Degussa P25 were compared with that of the more well-known Degussa P25 in varying pH media. Treatment performance was strongly affected by the initial H2O2 concentration for H2O2∕UV-C and photo-Fenton oxidation systems, whereas for the TiO2∕UV-A process only PC 500 TiO2 powder, an anatase crystal phase of the semiconductor, exhibited a significantly pH-dependent reaction efficiency. The decolorization rate followed the order of Fenton∕UV-C > Pt-P25∕UV-A > Mikroanatas∕UV-A > P25∕UV-A > PC 500∕UV-A > H2O2∕UV-C, whereas the decreasing order for total organic carbon reduction was Fenton∕UV-C > H2O2∕UV-C > Mikroanatas∕UV-A > Pt-P25∕UV-A > P25∕UV-A > PC 500∕UV-A for the studied reaction conditions. Removal of optical density at 254-nm wavelength ranged between 75 and 96%.     

Molecular Mechanism of Granulation. II: Proton Translocating Activity

A laboratory-scale upflow anaerobic sludge blanket (UASB) reactor was used in this study to produce granular sludge at mesophilic temperatures (35 ± 1°C). After more than 150 days of operation, a COD removal efficiency of 95% was achieved with an organic loading rate of 8.73 gCOD∕L∕day. At the same time, the sludge granulation process was observed. The mature granules were examined for their stability in terms of the presence of calcium ion, surfactant, pH (buffer and H2SO4∕NaOH solution), metabolic inhibitor (iodoacetic acid and sodium fluoride), and proton translocator (carbonyl cyanide m-chlorophenyl-hydrazone). The results showed that bacterial surface dehydration, biological metabolic activity, and proton translocating activity were directly related to the strength of UASB granules. This indicated that the proton translocating activity on bacterial surfaces was the crucial factor in sludge granulation and, as a consequence, supported the proton translocation-dehydration theory. Experimental results from other studies were also used to support this new theory.     

Applicability of Equilibrium Isotherm Models for the Biosorptive Uptakes in Comparison to Activated Carbon-Based Adsorption

The adsorption isotherm models available in the literature have generally developed for sorption onto metallic surfaces or activated carbon-based sorbents. However, biosorptive uptakes involve interactions of biopolymer-based surfaces with different types of pollutants, which are quite different from metal surfaces or activated carbon. So, in the present study, 16 different types of adsorption isotherm models have been studied. For a ready reference both types of sorbents, i.e., a biosorbent and activated carbon have been employed. Results show that in general the accuracy of models to fit experimental data improves with the degree of freedom. The Fritz–Schluender model gives the most accurate fit (R2?0.85–0.99) to all experimental data in comparison to other models used both for activated carbon and the biosorbent. However, most widely used isotherm models, i.e., Langmuir and Freundlich, could be used to describe the sorption equilibrium of biosorptive processes with a fair degree of accuracy, owing to the mathematical ease in the use of these models. Trends of the applicability of various sorption equilibrium models to biosorptive uptakes are similar to those of activated carbon-based sorptions. Comprehensive equilibrium analysis has assisted in understanding the mechanistic aspects associated with different types of sorbents.     

Organic Removal of Anaerobically Treated Leachate by Fenton Coagulation

The leachate from a Hong Kong landfill, containing 15,700 mg∕L of chemical oxygen demand (COD) and 2,260 mg∕L of ammonia nitrogen (NH3–N), was first treated in a UASB (upflow anaerobic sludge blanket) reactor at 37°C. The process on average removed 90.4% of COD with 6.6 days of hydraulic retention at an organic loading rate of 2.37 g of COD∕L?day. The UASB effluent was further treated by the Fenton coagulation process using H2O2 and Fe2+. Under the optimal condition of 200 mg of H2O2∕L and 300 mg of Fe2+∕L and an initial pH of 6.0, 70% of residual COD in the UASB effluent was removed, of which 56% was removed by coagulation∕precipitation and only 14% by free radical oxidation. It is obvious that H2O2 and Fe2+ had a strong synergistic effect on coagulation. The average COD in the final effluent was 447 mg∕L. Removing each gram of COD required 0.28 g of Fe2+ and 0.18 g of H2O2.     

Adsorption behavior of rare earth elements using polyethyleneglycol (phosphomolybdate and tungstate) heteropolyacid sorbents in nitric solution

A new type of crystalline sorbent was prepared by the reaction of polyethyleneglycol (PEG) with phosphomolybdic (PMo) and phosphotungstic (PW) heteropolyacids. The morphology of the obtained sorbents was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It has been shown that a complexing reaction occurs between PEG and the heteropolyacids. By using these sorbents, the adsorption behaviors of rare earth elements in nitric solution were studied. The effects of temperature, contact time, nitric acid and initial metal ion concentration on the adsorption were investigated. In 0.1–5.0 mol L^− 1HNO₃, the adsorption percentage decreases with the increase of acid concentration. H,PEG400,PW and H,PEG400,PMo exhibited a different selectivity for rare earth metals, with H,PEG400,PW adsorbing in the order of La³⁺ > Y³⁺ > Pr³⁺ > Gd³⁺ > Sm³⁺, and H,PEG400,PMo in the order of Y³⁺ > La³⁺ > Pr³⁺ > Gd³⁺ > Sm³⁺. The experimental maximum adsorption capacities of the sorbents are in the range of 90–225 mg g^− 1 for Y³⁺, La³⁺, Pr³⁺, Sm³⁺ and Gd³⁺. In all cases, the maximum adsorption capacities of H,PEG400,PW are near to those of H,PEG400,PMo. The equilibrium data were evaluated according to the Freundlich and Langmuir isotherms and the Langmuir equation gave a better fit and modeled the adsorption well.     

Proteasome inhibitors induce mitochondria-independent apoptosis in human glioma cells

6-Chloro-5,10-dihydro-5-[( 1-methyl-4-piperidinyl)acetyl]-11H-dibenzo[b,e][1,4]diazepine-11one++ + hydrochloride (UH-AH 37) is an analog of pirenzepine that has previously been reported to interact with classical muscarinic antagonists in a competitive manner, yet its binding has also been found to be sensitive to the same epitope as is that of the allosteric ligand gallamine. The present study was carried out with wild-type and chimeric muscarinic receptors to determine whether UH-AH 37 might also have an allosteric mode of action. In assays that detect only allosteric interactions, UH-AH 37 slowed the rate of dissociation of [3H]N-methylscopolamine (NMS) from all five muscarinic receptor subtypes, with the highest apparent affinity at m2. By contrast, studies carried out under equilibrium conditions have found UH-AH 37 to have the lowest affinity for the m2 subtype. Studies with m2/m5 chimeric receptors found the allosteric potency of UH-AH 37 to be sensitive to an epitope in the seventh transmembrane domain (TM). Again, this contrasts with equilibrium studies, wherein an epitope in the sixth TM has been implicated. Simultaneous analysis of the interactions between UH-AH 37 and [3H]NMS at the m2 receptor under equilibrium and non-equilibrium conditions found that a simple allosteric model could not accommodate both sets of data. On the other hand, the model did accommodate such data for gallamine; gallamine also displays concordance in order-of-potency and epitope sensitivity between equilibrium and non-equilibrium assays. Based on these results, we conclude that UH-AH 37 interacts at the classical muscarinic binding site with high affinity and at a second (allosteric) site with lower affinity.     

Oxidative Decolorization of Reactive Dye Solution Using Fly Ash as Catalyst

This paper deals with the potential of coal fly ash as a heterogeneous catalyst in peroxidative decolorization of aqueous solution of several reactive drimarene dyes using hydrogen peroxide (H2O2). The effects of various parameters (source of fly ash, fly ash loading, temperature, pH, initial concentration of dye and hydrogen peroxide, and deactivation of catalytic effect of fly ash) were studied. The rate of decolorization is zero order with respect to concentration of dye in the range of 50–200 mg∕L and first order with respect to concentration of H2O2 in the range of 375–2,500 mg∕L. It was found that at 333 K and pH 2.0, only 2% (weight/volume) fly ash loading can completely decolorize 100 mg∕L dye solution within 180–1,770 s for an initial H2O2 concentration of 1,500 mg∕L, depending on the source of fly ash and dye used. But maximum 25% decolorization was noticed after 3 h duration of reaction without fly ash. The negligible homogeneous catalytic action of trace amount of metals like Fe, Mn, and Cu leached from the fly matrix confirmed the sole heterogeneous catalytic nature of fly ash particles in decolorization reactions. The deactivation of fly ash was found to be <30% in nine repeated uses. Adsorption dynamics and mechanism of dyes onto fly ash also were studied in the absence of H2O2.     

Preliminary results of a phase II study of high-dose radiation therapy and neoadjuvant plus concomitant 5-fluorouracil with CDDP chemotherapy for patients with anal canal cancer: a French cooperative study

The mechanism of modulation of [3H]raclopride binding to dopaminergic receptors in rat brain striatal membranes by sodium ions was studied by means of equilibrium and kinetic measurements. Among different mono- and divalent cations studied, only sodium and lithium ions significantly enhanced [3H]raclopride binding to rat striatal membranes, but the effect of lithium was considerably smaller if compared with that of sodium. The equilibrium binding studies revealed that the increase in Na+ concentration from 0.5 to 150 mM increased both the radioligand affinity and the number of binding sites. The meaning of these changes was established by kinetic studies, which yielded hyperbolic plots of [3H]raclopride binding rate constants over the radioligand concentration. These plots correspond to the two-step ligand binding reaction mechanism, involving fast binding equilibrium followed by a slow isomerization of the receptor-antagonist complex. Sodium ions did not influence the antagonist affinity for the receptor sites in the first step of the binding process, nor the rate of isomerization of the receptor-ligand complex, but slowed down the rate of deisomerization. This led to a change in the value of the receptor-ligand dissociation constant Kd determined under equilibrium conditions. The same change in deisomerization rate was also sufficient to alter the receptor density (Bmax), measured by the conventional ligand binding procedure.     

The affinity of cholera toxin for Ni2+ ion

Cholera toxin (CT) was shown to bind to immobilized Ni2+ ion. The affinity of CT for the complex required the presence of the Ni2+ ion, since CT was unable to bind in its absence. Binding was mediated by the B-subunit (CTB) as both CT and CTB bound to the resin, but not the A-subunit (CTA). Binding was reversible in the presence of imidazole and suggested that the affinity of CT for the Ni2+ ion was mediated by His residues. The heat-labile enterotoxin of Escherichia coli (LT), which is closely related to CT, was unable to bind to the Ni2+ ion. Comparison of amino acid sequences revealed the presence of three His residues in CT (positions 13, 57 and 94), but only one in LT (position 57). To confirm that the residues at positions 13 and 94 of CTB were responsible for the binding, they were changed to residues found in LTB. Changing His13-->Arg completely abrogated the ability of CTB to bind to Ni2+ ion. In contrast, the mutation of His 94-->Asn reduced, but did not abrogate, the ability of CTB to bind to Ni2+ ion. Based on calculated interatomic distances, it is unlikely that His13 and His94 are part of the same complex. There appear to be two separate binding sites, with the principal site involving His13 and a much weaker site involving His94. This latter site can only participate in binding if the complex involving His13 has formed.     

Empirical Model and Kinetic Behavior of Thermophilic Composting of Vegetable Waste

Laboratory-scale temperature-controlled reactors were used to generate experimental data of thermophilic composting of vegetable waste. By fitting in experimental data of thermophilic composting, the obtained empirical model (also verified by F-test) appeared to be a quadratic form. The empirical model can be used to predict operating conditions (ratio of predried vegetable waste to rice husks, aeration rate, and reaction temperature and time) for thermophilic composting of vegetable waste in the subtropical region. Moreover, an innovative method for investigating kinetic behavior of thermophilic composting (an exoenzyme-catalyzed reaction followed by a multienzyme-catalyzed reaction) is proposed. The two biochemical reactions of thermophilic composting of vegetable waste followed Monod-type kinetics with the specific substrate utilization rate constants k1 and k2 of 0.026 and 4.5 mg COD∕mg VSS∕day, respectively. Accordingly, the exoenzyme-catalyzed reaction kinetically controls the overall process of thermophilic composting of vegetable waste.     

Evidence for ryanodine receptors in Schistosoma mansoni

The present study investigated the presence of ryanodine receptors in the trematode Schistosoma mansoni. [3H]Ryanodine specific binding sites were found in the four subcellular fractions of S. mansoni; however, more binding sites were recovered in the heterogeneous fraction P1 and the microsomal fraction P4, as was thapsigargin-sensitive (Ca2+-Mg2+)ATPase activity, marking the sarco/endoplasmic reticulum calcium ATPase (SERCA) pumps. This binding had an equilibrium dissociation constant (Kd) in the nanomolar range, an apparent maximal number of receptors (Bmax) of about 80 fmol/mg of protein, and was modulated by ions (Ca2+, Mg2+) and some pharmacological tools such as caffeine. Ryanodine was able to accelerate the rate of 45Ca2+ release from actively loaded vesicles, and also to induce a transient contraction of the whole worm. We conclude that ryanodine-sensitive Ca2+ release channels are present in S. mansoni, with properties very similar to the ones present in higher animals.     

Methanogenic Characteristics of Formate-Utilizing Sludge

The formate-utilizing sludge was first enriched in a chemostat reactor for over 90 days; at steady state, the sludge yield averaged 0.066 mg volatile suspended solids (VSS)∕mg chemical oxygen demand (COD). The methanogenic characteristics of this sludge were then investigated in three series of batch experiments at 37°C using formate, acetate, and H2∕CO2, individually, as substrates. At pH 6.4–8.0, the formate-degrading rate averaged 0.76 mg∕mg VSS∕h (6.35 mg COD∕mg VSS∕d). At pH 3.0, the sludge completely lost its bioactivity, and required a lengthy recovery period to regain a fraction of its bioactivity after the pH was adjusted to pH 7.1. The sludge was also able to utilize H2∕CO2 as substrate at an average rate of 0.0167 mg H2∕mg VSS∕h (3.21 mg COD∕mg VSS∕d). At pH ≤ 8.0, the sludge degraded acetate at a very low rate of 3.0 μg∕mg VSS∕h (0.077 mg COD∕mg VSS∕d). The sludge exhibited a slight homoacetogenic activity at pH > 8.0 using formate as substrate; the homoacetogenic reaction using H2∕CO2 as substrate was thermodynamically infeasible, according to chemical free energy analysis.