Personal Research Database

Full Text: 2010\J Haz Mat179, 424.pdf

Abstract: A novel Al-Ce hybrid adsorbent with high sorption capacity for fluoride was prepared through the coprecipitation method in this study, and its preparation conditions were optimized. X-ray diffraction (XRD) and scanning electron microscope (SEM) results showed that the hybrid adsorbent was of amorphous structure and constituted by some aggregated nanoparticles. As the adsorbent had the zero point of potential at pH 9.6, it was very effective in fluoride removal from aqueous solution via electrostatic interaction. The results of sorption experiments including sorption kinetics, isotherms, and the effect of solution pH showed that the sorption of fluoride on the Al-Ce adsorbent was fast and pH-dependent. Especially, the adsorbent had high sorption capacity up to 27.5 mg g(-1) for fluoride at the equilibrium fluoride concentration of 1 mg L-1, much higher than that of the conventional adsorbents. Fourier transform infrared (FTIR) analysis and zeta potential measurement showed that the hydroxyl groups and the protonated hydroxyl groups on the adsorbent surface were involved in the fluoride adsorption. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Adsorption Capacity, Adsorption Mechanism, Al-Ce Adsorbent, Analysis, Aqueous-Solution, Arsenate, Catalysts, Chitosan, Defluoridation, Drinking Water, Equilibrium, Fluoride, Fluoride Removal, Fourier Transform Infrared, FTIR, Infrared, Ions, Isotherms, Kinetics, Modified Fungal Biomass, Nanoparticles, Oxide Adsorbent, pH, Preparation, Removal, SEM, Sorption, Sorption Behavior, Sorption Kinetics, Water, X-Ray Diffraction, XRD, Zeta Potential

? Wang, X.H., Song, R.H., Teng, S.X., Gao, M.M., Ni, J.Y., Liu, F.F., Wang, S.G. and Gao, B.Y. (2010), Characteristics and mechanisms of Cu(II) biosorption by disintegrated aerobic granules. Journal of Hazardous Materials, 179 (1-3), 431-437.

Full Text: 2010\J Haz Mat179, 431.pdf

Abstract: Disintegrated aerobic granules (DAG) as an effective biosorbent had great potential to remove Cu(II) from aqueous solution. The effects of solution pH value, contact time, initial Cu(II) concentration on the biosorption were investigated. Kinetic studies indicate that pseudo-second-order model with correlation coefficients of 0.9999 best fits the Cu(II)biosorption process. Investigation of the biosorption mechanisms shows that Cu(II) biosorption is associated with a significant release of Ca(II). The adsorption capacity of extracted extracellular polymeric substances (EPS) was 2.34 times as much as that of pristine DAG, indicating the significant role of EPS in adsorption. In order to determine the role of different functional groups, DAG was chemically modified to block specific functional groups and was then used in the adsorption of Cu(II). The anionic carboxyl group, was identified as the key binding site for the cationic Cu(II). Results reveal that ion exchange is the most important biosorption mechanism but other mechanisms to some extent like electrostatic interaction, involving in functional groups, also play a part. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Activated-Sludge, Adsorption, Aqueous-Solution, Aspergillus-niger, Biodegradation, Biosorption, Copper(II) Ions, Disintegrated Aerobic Granules, Extracellular Polymeric Substances, Extracellular Polymeric Substances, Functional Groups, Heavy-Metal Biosorption, Kinetic, Removal, Sequencing Batch Reactor

? Sobczak, I., Pawlowski, H., Chmielewski, J. and Ziolek, M. (2010), Gold and gold-iron modified zeolites-Towards the adsorptive deodourisation. Journal of Hazardous Materials, 179 (1-3), 444-452.

Full Text: 2010\J Haz Mat179, 444.pdf

Abstract: Zeolites exhibiting different structures (Y, Beta, and ZSM-5) were modified with gold and iron and applied for odour adsorption from the air containing dibutyl sulphide (Bu2S) used as a representative odour producing compound. The structure of the zeolites used determines the rate of adsorption (higher on Y type zeolites and smaller on two other zeolites), whereas hydrophilicity affects the selectivity towards Bu2S adsorption increasing in the order: Y < Beta < ZSM-5. For the same zeolite structure, Bu2S adsorption selectivity depends on the total acidity of zeolites which increases after iron modification. The texture and surface properties of the modified zeolites were studied by XRD, XPS, UV-vis, TEM, pyridine adsorption and FTIR, test reactions (acetonylacetone cyclisation, isopropanol decomposition). (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Acidity, Adsorption, Adsorption Of Bu2S, Au, Fe Modification, Catalysts, Co Oxidation, E-Nose, Fe, FTIR, Isopropanol Decomposition, Oxides, Pyridine, Silica, Sites, TEM, XPS, XRD, Y, Beta and ZSM-5 Zeolites, Zeolite, Zeolites, ZSM-5

? Lin, Y.C. and Lee, H.S. (2010), Effects of TiO₂ coating dosage and operational parameters on a TiO₂/Ag photocatalysis system for decolorizing Procion red MX-5B. Journal of Hazardous Materials, 179 (1-3), 462-470.

Full Text: 2010\J Haz Mat179, 462.pdf

Abstract: In this study, titanium dioxide (TiO2) powder was coated onto the surface of a dendritic silver (Ag) carrier to synthesize TiO2/Ag for decolorizing Procion red MX-5B (MX-5B), and related operation factors were also studied. The results showed that even without ultraviolet-A (UVA) irradiation, the Ag carrier from the TiO2/Ag catalyst had oxidizing ability, which could effectively degrade MX-5B color, but TiO2 was ineffective. In addition, TiO2 from TiO2/Ag demonstrated photocatalysis performance when irradiated, and the Ag carrier further showed an electron-scavenging ability to mitigate electron-hole pair recombination, which can improve the photocatalytic efficacy. With the oxidization and electron-scavenging ability of Ag and the photocatalysis ability of TiO2, TiO2/Ag can decolor MX-5B more efficiently than TiO2. The heavier Ag carrier also improves the solid-liquid separation of nano-TiO2, making TiO2/Ag more suitable for application in slurry systems of photocatalytic water treatment. When the TiO2/Ag coating ratio was 50% by weight, there was a sufficient amount of TiO2 on Ag’s surface with a good distribution, and it exhibited a good photocatalysis decolorizing effect. In a study of how operational factors impact the decolorizing of MX-58 in the TiO2/Ag photocatalysis system with UVA irradiation (UVA-TiO2/Ag), the decolorization efficiency was optimal when the solution was maintained at pH 6.35. The addition of 0.01 M hydrogen peroxide (H2O2) aided the photocatalysis decolorization efficiency, although excessive H2O2 reacted with hydroxyl free radicals and decreased the active groups in the system, thereby reducing the photocatalysis activity. An operating temperature of 40 degrees C was conducive to MX-5B decolorization, which was better than operating at room temperature. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Ag, Aqueous Suspensions, Color, Decolorization, Degradation, Doped TiO₂, Dye, Dye, pH, Photocatalysis, Photodegradation, Reuse, Silver (Ag), System, Textile Waste-Water, TiO₂, Titanium Dioxide (TiO₂), Treatment, Water, Water Treatment, Weight

? Xiang, G.Q., Zhang, Y.M., Jiang, X.M., He, L.J., Fan, L. and Zhao, W.J. (2010), Determination of trace copper in food samples by flame atomic absorption spectrometry after solid phase extraction on modified soybean hull. Journal of Hazardous Materials, 179 (1-3), 521-525.

Full Text: 2010\J Haz Mat179, 521.pdf

Abstract: Soybean hull was chemically modified with citric acid and used as a solid phase extraction adsorbent for the determination of trace amounts of Cu2+ in food samples by flame absorption spectrometry (FAAS). The effect of pH, sample flow rate and volume, elution flow rate and volume and co-existing ions on the recovery of the analyte were investigated. The results showed that Cu2+ could be adsorbed on the modified soybean hull at pH 8.0 and eluted by 2.0 mL of 1.0 mol L-1 HCl. Under the optimized conditions, the adsorption capacity of modified soybean hull was found to be 18.0 mg g(-1) for Cu2+. The detection limit of the proposed method was 0.8 ng mL(-1) for Cu2+ with an enrichment factor of 18. The analytical result for the certified reference tea sample (GBW07605) was in a good agreement with the certified value. The proposed method has also been successfully applied to the determination of trace Cu2+ in dried sweet potato, lake water and milk powder, the recovery of Cu2+ for spiked samples was between 91% and 109.6%. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Adsorption Capacity, Atomic Absorption Spectrometry, Cadmium, Copper, Determination, Elements, Faas, Flow-Injection, Food Samples, ICP-AES, Metal Enrichment, pH, Preconcentration, Shell Activated Carbon, Silica-Gel, Solid Phase Extraction, Soybean Hull, Spectrophotometric Determination, Water

? An, C.J., He, Y.L., Huang, G.H. and Liu, Y.H. (2010), Performance of mesophilic anaerobic granules for removal of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from aqueous solution. Journal of Hazardous Materials, 179 (1-3), 526-532.

Full Text: 2010\J Haz Mat179, 526.pdf

Abstract: The performance of mesophilic anaerobic granules to degrade octahydro-1,3,5,7-tetranitro-1,3,57 tetrazocine (HMX) was investigated under various conditions. The results of batch experiments showed that anaerobic granules were capable of removing HMX from aqueous solution with high efficiency. Both biotic and abiotic mechanisms contributed to the removal of HMX by anaerobic granules under mesophilic conditions. Adsorption appeared to play a significant role in the abiotic process. Furthermore. HMX could be biodegraded by anaerobic granules as the sole substrate. After 16 days of incubation, 99.04% and 96.42% of total HMX could be removed by 1 g VSS/L acclimated and unacclimated granules, respectively. Vancomycin, an inhibitor of acetogenic bacteria, caused a significant inhibition of HMX biotransformation, while 2-bromoethanesulfonic acid, an inhibitor of methanogenic bacteria, only resulted in a slight decrease of metabolic activity. The presence of the glucose, as a suitable electron donor and carbon source, was found to enhance the degradation of HMX by anaerobic granules. Our study showed that sulfate had little adverse effects on biotransformation of HMX by anaerobic granules. However, nitrate had significant inhibitory effect on the extent of HMX removal especially in the initial period. This study offered good prospects of using high-rate anaerobic technology in the treatment of munition wastewater. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Bacteria, Batch, Biodegradation, Biotransformation, Degradation, Electron-Acceptor, Enrichment Culture, Explosives, Hexahydro-1,3,5-Trinitro-1,3,5-Triazine, Hydrogen, Mesophilic Anaerobic Granules, Metabolic Inhibitor, Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine (HMX), Performance, RDX, Reduction, Removal, Sludge, Technology, Treatment, Waste-Water Treatment, Wastewater

? Liu, W.M., Hu, Y.Q. and Tu, S.T. (2010), Active carbon-ceramic sphere as support of ruthenium catalysts for catalytic wet air oxidation (CWAO) of resin effluent. Journal of Hazardous Materials, 179 (1-3), 545-551.

Full Text: 2010\J Haz Mat179, 545.pdf

Abstract: Active carbon-ceramic sphere as support of ruthenium catalysts were evaluated through the catalytic wet air oxidation (CWAO) of resin effluent in a packed-bed reactor. Active carbon-ceramic sphere and ruthenium catalysts were characterized by N-2 adsorption and chemisorption measurements. BET surface area and total pore volume of active carbon (AC) in the active carbon-ceramic sphere increase with increasing KOH-to-carbon ratio, and AC in the sample KC-120 possesses values as high as 1100 m(2) g(-1) and 0.69 cm(3) g(-1)(carbon percentage: 4.73 wt.%), especially. Active carbon-ceramic sphere supported ruthenium catalysts were prepared using the RuCl3 solution impregnation onto these supports, the ruthenium loading was fixed at 1-5 wt.% of AC in the support. The catalytic activity varies according to the following order: Ru/KC-120 > Ru/KC-80 > Ru/KC-60 > KC-120 > without catalysts. It is found that the 3 wt.% Ru/KC-120 catalyst displays highest stability in the CWAO of resin effluent during 30 days. Chemical oxygen demand (COD) and phenol removal were about 92% and 96%, respectively at the reaction temperature of 200 degrees C, oxygen pressure of 1.5 MPa, the water flow rate of 0.75 L h(-1) and the oxygen flow rate of 13.5 L h(-1). (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Acetic-Acid, Activation, Active Carbon-Ceramic Sphere, Adsorption, COD, Composites, Cwao, Metal, Oxidation, Phenol, Phenol-Formaldehyde Resins, Pore, Pressure, Removal, Resin Effluent, Ru, Ruthenium, Stability, Water

? Tan, S.H., Chen, X.G., Ye, Y., Sun, J., Dai, L.Q. and Ding, Q. (2010), Hydrothermal removal of Sr²⁺ in aqueous solution via formation of Sr-substituted hydroxyapatite. Journal of Hazardous Materials, 179 (1-3), 559-563.

Full Text: 2010\J Haz Mat179, 559.pdf

Abstract: We removed Sr2+ in simulating wastewater and simultaneously prepared Sr-substituted hydroxyapatite via chemical precipitation and hydrothermal treatment. Both higher initial pH value and higher molar ratio of Sr/(Sr + Ca) contributed to lower residual Sr2+ concentration and higher removal efficiency. About two thirds of Sr2+ residual in solution after chemical precipitation were further reduced by hydrothermal treatment. The optimal Sr removal result was 99.66% with an ultimate concentration of 2.0 mg L-1 when the initial pH was 12 and Sr/(Sr + Ca) was 0.2. Sr-substituted hydroxyapatite phase with hexagonal structure was identified by XRD and EDS results. However, it was found that SrHPO4 phase was formed in the samples with high Sr composition. The lattice constants became larger with the increase of Sr2+ and the crystallinity became higher with the increase of pH value. Rod-like particles were observed in SEM images of synthesized Sr-substituted hydroxyapatite samples, with the size of 20-30 nm in width and 70-100 nm in length. With little secondary waste and simple treating procedure, this method is an effective and prospective measure to deal with Sr-90 in nuclear waste and industry wastewater. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Composite, Compound, Crown-Ether, High Level Waste (HLW), Hydrothermal Treatment, Hydroxyapatite, Liquid Waste, pH, Powders, Precipitation, Radioactive-Waste, Removal, SEM, Separation, Sr Removal, Sr-90, Strontium, Treatment, Wastewater, XRD

? Saeed, A., Sharif, M. and Iqbal, M. (2010), Application potential of grapefruit peel as dye sorbent: Kinetics, equilibrium and mechanism of crystal violet adsorption. Journal of Hazardous Materials, 179 (1-3), 564-572.

Full Text: 2010\J Haz Mat179, 564.pdf

Abstract: This study reports the sorption of crystal violet (CV) dye by grapefruit peel (GFP), which has application potential in the remediation of dye-contaminated wastewaters using a solid waste generated by the citrus fruit juice industry. Batch adsorption of CV was conducted to evaluate the effect of initial pH, contact time, temperature, initial dye concentration. GFP adsorbent dose, and removal of the adsorbate CV dye from aqueous solution to understand the mechanism of sorption involved. Sorption equilibrium reached rapidly with 96% CV removal in 60 min. Fit of the sorption experimental data was tested on the pseudo-first and pseudo-second-order kinetics mathematical equations, which was noted to follow the pseudo-second-order kinetics better, with coefficient of correlation ≥ 0.992. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacity of 254.16 mg g^-1. The GFP was regenerated using 1 M NaOH, with up to 98.25% recovery of CV and could be reused as a dye sorbent in repeated cycles. GFP was also shown to be highly effective in removing CV from aqueous solution in continuous-flow fixed-bed column reactors. The study shows that GFP has the potential of application as an efficient sorbent for the removal of CV from aqueous solutions. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Adsorbent, Adsorption, Aqueous-Solution, Basic-Dyes, Biosorption, Congo-Red, Crystal Violet, Dye, Dye Sorption, EDX Analysis, Equilibrium, Fixed-Bed Column, FTIR Spectrophotometry, Grape Fruit Peel, Isotherm, Kinetics, Langmuir, Langmuir Isotherm, Methylene-Blue, Removal, Rice Husk, Sorption, Waste-Water

? Altinişık, A., Gür, E. and Seki, Y. (2010), A natural sorbent, Luffa cylindrica for the removal of a model basic dye. Journal of Hazardous Materials, 179 (1-3), 658-664.

Full Text: 2010\J Haz Mat179, 658.pdf

Abstract: In this work, application of Luffa cylindrica in malachite green (MG) removal from aqueous solution was studied in a batch system. The effect of contact time, pH and temperature on removal of malachite green was also investigated. By the time pH was increased from 3 to 5, the amount of sorbed malachite green also increased. Beyond the pH value of 5, the amount of sorbed malachite green remains constant. The fits of equilibrium sorption data to Langmuir, Freundlich and Dubinin-Radushkevich equations were investigated. Langmuir isotherm exhibited best fit with the experimental data. Monolayer sorption capacity increased with the increasing of temperature. Sorption kinetic was evaluated by pseudo-first-order, pseudo-second-order. Elovich rate equations and intraparticle diffusion models. It was inferred that sorption follows pseudo-second-order kinetic model. Thermodynamic parameters for sorption process were also found out. Spontaneous and endothermic nature of sorption was obtained due to negative value of free energy (Delta G degrees) and positive value of enthalpy (Delta H degrees) changes. FTIR analyses were also conducted to confirm the sorption of malachite green onto L cylindrica. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Activated Carbon, Adsorption Characteristics, Aqueous-Solution, Basic Dye, Biomass, Biosorption, Diffusion, Dye, Dye Removal, Equilibrium, Isotherm, Kinetic, Kinetics, Langmuir, Langmuir Isotherm, Luffa Cylindrica, Malachite Green, Malachite-Green, Methylene-Blue, Sorption, Sorption Kinetic, Sorption Kinetics, Thermodynamic, Thermodynamic Aspects, Waste-Water

? Cheng, H.F. and Reinhard, M. (2010), In-line gas chromatographic apparatus for measuring the hydrophobic micropore volume (HMV) and contaminant transformation in mineral micropores. Journal of Hazardous Materials, 179 (1-3), 596-603.

Full Text: 2010\J Haz Mat179, 596.pdf

Abstract: Desorption of hydrophobic organic compounds from micropores is characteristically slow compared to surface adsorption and partitioning. The slow-desorbing mass of a hydrophobic probe molecule can be used to calculate the hydrophobic micropore volume (HMV) of microporous solids. A gas chromatographic apparatus is described that allows characterization of the sorbed mass with respect to the desorption rate. The method is demonstrated using a dealuminated zeolite and an aquifer sand as the model and reference sorbents, respectively, and trichloroethylene (TCE) as the probe molecule. A glass column packed with the microporous sorbent is coupled directly to a gas chromatograph that is equipped with flame ionization and electron capture detectors. Sorption and desorption of ICE on the sorbent was measured by sampling the influent and effluent of the column using a combination of switching and injection valves. For geosorbents, the HMV is quantified based on Gurvitsch’s rule from the mass of TCE desorbed at a rate that is characteristic for micropores. Instrumental requirements, design considerations, hardware details, detector calibration, performance, and data analysis are discussed along with applications. The method is novel and complements traditional vacuum gravimetric and piezometric techniques, which quantify the total pore volume under vacuum conditions. The HMV is more relevant than the total micropore volume for predicting the fate and transport of organic contaminants in the subsurface. Sorption in hydrophobic micropores strongly impacts the mobility of organic contaminants, and their chemical and biological transformations. The apparatus can serve as a tool for characterizing microprous solids and investigating contaminant-solid interactions. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Analysis, Aquifer Material, Clay-Minerals, Compounds, Dealuminated Y-Zeolites, Desorption, Gas Chromatographic Apparatus, Halogenated Organic-Chemicals, Hydrophobic Micropore Volume (HMV), Long-Term Sorption, Mobility, Model Solids, Organic Compounds, Pore, Sediments, Slow Desorption, Sorbent, Sorption, TCE, Transformation, Trichloroethylene, Trichloroethylene Desorption, Unsaturated Conditions, Zeolite

? Parida, K.M. and Dash, S.K. (2010), Adsorption of Cu²⁺ on spherical Fe-MCM-41 and its application for oxidation of adamantane. Journal of Hazardous Materials, 179 (1-3), 642-649.

Full Text: 2010\J Haz Mat179, 642.pdf

Abstract: Fe-MCM-41 with varying Si/Fe ratios (20, 50, 70 and 90) were prepared by using cetyltrimethylammoniumbromide (CTAB) as the structure-directing agent (SDA), tetraethylorthosilicate (TEOS) as the silica source and ethanol as co-surfactant in alkaline medium. The characterization was done by SEM: UV-vis diffused reflectance and FT-IR. Adsorption of copper solutions with varying parameters such as concentration, temperature and pH were performed over Fe-MCM-41 samples. The experimental data fitted well to the Langmuir and Freundlich adsorption isotherm. Fe-MCM-41 having Si/Fe ratio (90) showed highest copper adsorption capacity at pH 5.5. Cu2+ concentration of 59.6 ppm and temperature 323 K. Fe-MCM-41(90)-Cu(59.6) was tested as a catalyst for oxidation of adamantane using hydrogen peroxide as the oxidant. The GC analyses revealed significant conversion of 32.5% and selectivity of 54% towards formation of 1-adamantanol. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Adamantane, Adsorption, Adsorption Capacity, Adsorption Isotherm, Catalysts, Containing MCM-41, Copper, Copper Adsorption, Cu²⁺ Adsorption, Epoxidation, Fe-MCM-41, Freundlich, FTIR, Iron, Isotherm, Langmuir, Mechanism, Molecular-Sieves, Oxidation, pH, Removal, Selective Mesoporous Adsorbents, SEM, Separation, Silica, Silicas

? Behera, S.K., Oh, S.Y. and Park, H.S. (2010), Sorption of triclosan onto activated carbon, kaolinite and montmorillonite: Effects of pH, ionic strength, and humic acid. Journal of Hazardous Materials, 179 (1-3), 684-691.

Full Text: 2010\J Haz Mat179, 684.pdf

Abstract: Sorption of triclosan on three sorbents, viz., activated carbon, kaolinite and montmorillonite was studied as a function of pH, ionic strength and humic acid (HA) concentration through controlled batch experiments. Triclosan sorption was found to be higher in the acidic pH range, as varying pH showed significant influence on the surface charge of the sorbents and degree of ionization of the sorbate. Sorption capacity of the sorbents increased with an increase in the ionic strength of solution. At low pH (pH 3), the overall increase in triclosan sorption was 1.2, similar to 4 and 3.5 times, respectively for activated carbon, kaolinite and montmorillonite when ionic strength was increased from 1 x 10(-3) to 5 x 10(-1) M. Triclosan sorption onto activated carbon decreased from 31.4 to 10.6 mg g(-1) by increasing the HA concentration to 200 mg C L-1. However, during sorption onto kaolinite and montmorillonite, the effect of HA was very complex probably due to (i) hydrophobicity (log K-ow = 4.76) of triclosan; and (II) complexation of HA with triclosan. Though triclosan sorption onto activated carbon is higher, the potential of kaolinite and montmorillonite in controlling the transport of triclosan in subsurface environment can still be appreciable. (C) 2010 Elsevier B.V. All rights reserved.

Keywords: Activated Carbon, Adsorption, Aqueous-Solution, Batch, Complex, Environment, Humic Acid, Ionic Strength, Kaolinite, Montmorillonite, Organic-Matter, pH, Pharmaceuticals, Phenolic-Compounds, Products, Removal, Sorption, Sorption Capacity, Toxicity, Triclosan, Waste-Water Treatment

? Yan, C.Z., Li, G.X., Xue, P.Y., Wei, Q.S. and Li, Q.Z. (2010), Competitive effect of Cu(II) and Zn(II) on the biosorption of Lead(II) by Myriophyllum spicatum. Journal of Hazardous Materials,