Personal Research Database

Full Text: 1997\J Haz Mat55, 115.pdf

Abstract: The strong sorption of hydrophobic contaminants poses a serious challenge to the development of remediation technologies. Their low solubilities in water limit the applicability of treatment technologies such as pump-and-treat, Their dissolution by surfactants is a promising approach for circumventing this difficulty. The solubilized contaminant is subsequently irrigated onto a vegetated zone and mineralized. A two-zone model is developed for a system in which the contaminant is flushed from the aquifer with an aqueous surfactant solution and applied to vegetated soil. The model takes into account dissolution, sorption and biodegradation of the contaminant in the aquifer zone under the assumption that local equilibria prevail. It also takes into account sorption, mineralization and plant uptake in the rhizosphere zone assuming that mineralization obeys Monod kinetics, Model simulation was performed to determine the effects of surfactant and oxygen concentrations in enhancing contaminant removal from the aquifer and to evaluate the number of flushings required to reduce the concentrations of contaminant to desired levels. The results indicate that surfactant appreciably reduces the number of flushings by increasing the solubilization of contaminant. Increasing oxygen concentration enhances contaminant degradation. The model predicts an optimistic outcome because of the assumptions imposed; it is expected that the actual number of flushings will be larger than predicted. (C) 1997 Elsevier Science B.V.

Keywords: Biodegradation, Bioremediation, Contaminant, Contaminants, Degradation, Development, Equilibria, Hydrogen-Peroxide, Hydrophobic, Kinetics, Mineralization, Model, Modelling, Non-Aqueous Phase, Nonionic Surfactant, Organic-Compounds, Outcome, Polynuclear Aromatic-Hydrocarbons, Pyrene, Remediation, Remediation Technologies, Removal, Simulation, Soil, Solubilization, Sorption, Surfactant, Surfactants, Systems, Treat Technology, Treatment, Vegetation, Water

? Torrents, A., Damera, R. and Hao, O.J. (1997), Low-temperature thermal desorption of aromatic compounds from activated carbon. Journal of Hazardous Materials, 54 (3), 141-153.

Full Text: 1997\J Haz Mat54, 141.pdf

Abstract: Low-temperature thermal desorption of three aromatic compounds (toluene, chlorobenzene, and nitrobenzene) loaded on activated carbon was investigated, Desorption kinetics of these compounds followed an exponential-decay-type model assuming a distribution of sites over a range of activation energies. The activation energies of toluene, chlorobenzene and nitrobenzene were 17.6, 26.0, and 35.6 kJ mol^-1, corresponding to initial surface concentrations of 190, 300, and 610 mg g^-1, respectively, The desorption parameters determined using a simplified model predicted the aqueous phase adsorption of toluene and nitrobenzene and were used to estimate the residual contaminant concentrations as a function of time and temperature, The presence of electron-withdrawing functional groups increases the activation energy and thus the higher temperature required for desorption. (C) 1997 Elsevier Science B.V.

Keywords: Activated Carbon, Activation, Activation Energy, Adsorption, Carbon, Contaminated Soils, Desorption, Distribution, Function, Functional Groups, Kinetic Model, Kinetics, Low Temperature, Model, Organics, Presence, Regeneration, Surface, Temperature, Thermal Desorption, Toluene

? Mohammed, N. and Allayla, R.I. (1997), Modeling transport and biodegradation of BTX compounds in saturated sandy soil. Journal of Hazardous Materials, 54 (3), 155-174.

Full Text: 1997\J Haz Mat54, 155.pdf

Abstract: Numerical models have been developed using finite difference and orthogonal collocation methods to simulate one dimensional transport with time-dependent pore water velocity, The modeling process includes sorption given by linear isotherm and biodegradation given by a variety of kinetics such as first-order, zero-order, Monod, non-growth associated Monod (Michaelis-Menten), Haldane and many other inhibitory and non-inhibitory kinetics. A number of initial and boundary conditions such as Dirichlet’s, Neuman’s, mixed, decaying, etc. have been modeled. The method of finite difference (for first order/zero order model only) and the method of orthogonal collocation (for all kinetics models) have been used to solve the governing transport equation. Numerical solutions have been verified with existing analytical solutions for special cases. Three models (first-order and/or zero-order, non growth associated Michaelis Menten, and Monod) have been inverted using a Gauss-Marquardt-Levenberg algorithm to assess the transport parameters. The models have been used to simulate one dimensional transport of BTX compounds in a pilot scale sand tank model. The data have been found to fit to all three kinetic models with acceptable coefficient of determination (R-2) and parameter values. The high concentration data have been found to fit better to the Michaelis Menten and the Monod models than the first order/zero order model. (C) 1997 Elsevier Science B.V.

Keywords: Aerobic Biodegradation, Analytical Solutions, Aquifer Material, Aromatic-Hydrocarbons, Benzene, Biodegradation, BTX, Coefficient of Determination, Degradation, Difference, Growth, Isotherm, Kinetic, Kinetic Models, Kinetics, Methods, Mixed, Model, Modeling, Models, Monoaromatic Hydrocarbons, Process, Sand, Scale, Soil, Sorption, Subsurface Soils, Toluene, Transport, Values, Water

Keywords: EDTA, Heavy Metals, Electroremediation

? Schwartz, D.T., Buehler, M.F., Christiansen, D.X. and Davis, E.J. (1997), In-situ monitoring of electrochemical transport processes in Hanford Grout Vault Soil. Journal of Hazardous Materials, 55 (1-3), 23-37.

Full Text: 1997\J Haz Mat55, 23.pdf

Abstract: Real-time spatially-resolved radiotracer and soil conductivity measurements were used to assess the fate of contaminants and the interaction of electrolysis products with Grout Vault Soil from the Department of Energy’s Hanford site in Richland, Washington. Radiotracer techniques allowed the extent that a radioactive species was remediated to be unambiguously determined in the laboratory, and the method also provided insight into the immobilization of Cs⁺ by adsorption to the soil. Conductivity measurements provided a window into the changing state of the porous medium and the propagation of electrochemically-generated species that were introduced by water electrolysis at each active electrode. Measurements of the velocity of conductivity fronts generated by water electrolysis were combined with detailed geochemical and geophysical data about the soil to evaluate plausible soil chemistries in the system. Based on ion transport rates, it was shown that the alkaline nature of the soil buffered protons generated at the anode and hydroxide anions generated at the cathode titrated surface groups in the soil. (C) 1997 Elsevier Science B.V.

Keywords: Adsorption, Anions, Anode, Cathode, Contaminants, Electric-Fields, Electrode, Electrokinetic Remediation, Electrolysis, Electroosmosis, Heavy-Metals, Immobilization, Insight, Interaction, Kaolinite, Monitoring, Radiotracer Techniques, Removal, Soil, Soil Remediation, State, Surface, Surface Groups, Transport, Water, Water Electrolysis

Wong, J.S.H., Hicks, R.E. and Probstein, R.F. (1996), EDTA-enhanced electroremediation of metal-contaminated soils. Journal of Hazardous Materials, 55 (1-3), 61-67.

Full Text: J\J Haz Mat55, 61.pdf

Abstract: Precipitation and sorption of heavy metals reduce their mobility and limit the effectiveness of in-situ remediation technologies. In electroremediation, metal mobility can be further impeded by the development of regions of elevated pH near the collecting electrodes. This paper investigates the feasibility of mobilizing precipitated heavy metals by delivering complexing agents into soils by ionic migration. Two metals, lead and zinc, were selected as contaminants, and EDTA, a widely available non-toxic chelating agent, was selected as the complexing agent. It was found that EDTA added to the catholyte can be readily delivered into a sandy soil where it solubilizes the precipitated metals. The resulting complexes are then transported to the anode with metal removal efficiencies, for the spiked laboratory samples, approaching 100%. The poor ligand utilization obtained in the tests is attributed to the low dissolution rate of the metals. Modifying the operating conditions to increase the concentration and the residence time of the ligand in the soil is expected to improve the utilization efficiency of the complexing agent. (C) 1996 Elsevier Science Ltd. All rights reserved.

Keywords: EDTA, Heavy Metals, Electroremediation

? Haran, B.S., Popov, B.N., Zheng, G.H. and White, R.E. (1997), Mathematical modeling of hexavalent chromium decontamination from low surface charged soils. Journal of Hazardous Materials, 55 (1-3), 93-107.

Full Text: 1997\J Haz Mat55, 93.pdf

Abstract: A new electrokinetic technology has been developed for in-situ decontamination of hexavalent chromium in sand. Imposition of a constant potential gradient across the soil matrix through a graphite cathode and iron anode resulted in successful migration of chromate towards the anode. The hexavalent chromium ions are reduced to the harmless trivalent form by chemical reaction with the anodic electrochemical dissolution product, Fe2+. The alkaline front generated at the cathode due to water reduction flushes across the cell and favors faster transport of chromate by enhancing its conductivity. The acidic front generated due to water oxidation at the anode remains adjacent at the electrode-sand interface due to its consumption by the corrosion reaction with iron. The lower production rate of H+ is also due to the competing anodic dissolution reaction. The low pH at the anodic region favors the reduction of hexavalent chromium to its trivalent state. The experimental results are compared with a theoretical model developed from first principles. The water electrolysis reactions at both electrodes, the sorption processes in sand and the water hydrolysis reaction have been included in the model. Concentration profiles for the movement of ionic species under a potential field were simulated for different times. The model predicts the sweep of the alkaline front across the cell due to the transport of OH- ions. Comparison of the chromate concentration profiles with experimental data after 28 days of electrolysis shows good agreement. The potassium cations are positively charged and remained at the cathode where they had been placed initially. The good agreement between the model and the data demonstrates that the analysis is likely to be an accurate estimation of the physical situation, within the limits of the assumptions made. (C) 1997 Elsevier Science B.V.

Keywords: Agreement, Alkaline Front, Analysis, Anode, Anodic Dissolution, Cathode, Cations, Chemical Reaction, Chromate, Chromium, Comparison, Concentration, Consumption, Diffusion, Electro-Migration, Electrokinetic Technology, Electrokinetics, Electrolysis, Electroosmosis, Hexavalent Chromium, Hydrolysis, In Situ, Ions, Iron, Kaolinite, Migration, Model, Modeling, OH, Oxidation, pH, Potassium, Production, Reduction, Region, Remediation, Removal, Sand, Simulation, Soil, Soils, Sorption, State, Surface, Surface Charge, Technology, Theoretical Model, Transport, Water, Water Electrolysis

? Reddy, K.R., Parupudi, U.S., Devulapalli, S.N. and Xu, C.Y. (1997), Effects of soil composition on the removal of chromium by electrokinetics. Journal of Hazardous Materials, 55 (1-3), 135-158.

Full Text: 1997\J Haz Mat55, 135.pdf

Abstract: Electrokinetic experiments were conducted on three different types of soil: glacial till, kaolin and Na-montmorillonite, in order to investigate the effect of soil mineralogy and naturally occurring hematite (Fe₂O₃) on the removal of chromium from these soils. Batch tests were also performed to characterize Cr(VI) adsorption onto these soils. This study has shown that soils which contain high carbonate buffers, such as the glacial till, hinder the development of an acid front, which results in alkaline conditions throughout the soil during electrokinetic remediation. However, soils possessing low buffering capacity, such as kaolin and Na-montmorillonite, favor the development of an acid front which results in a distinct pH gradient with pH values varying from 2 near the anode to over 11 near the cathode. The results from the adsorption tests showed that Cr(VI) adsorption onto soils depends on the soil type and soil pH. The adsorption of Cr(VI) was found to be governed by soil surface complexation reactions and was significant in Na-montmorillonite, moderate in kaolin and low in glacial till. The Cr(VI) adsorption was found to be pH dependent, with low adsorption occurring at high pH values and high adsorption occurring at low pH values. The low adsorption of Cr(VI) under alkaline conditions in the glacial till resulted in high Cr(VI) removal during electrokinetics. Moderate Cr(VI) adsorption in the acidic regions in kaolin resulted in lower Cr(VI) removal than in the glacial till, High Cr(VI) adsorption in acidic regions of Na-montmorillonite resulted in low Cr(VI) migration. The presence of hematite or iron oxide in soils on the removal of Cr(VI) by electrokinetics depends on the soil mineralogical composition. In sells such as glacial till. the presence of iron oxide creates complex geochemistry and retards Cr(VI) removal. However. in homogeneous clays such as kaolin and Na-montmorillonite, the presence of iron oxide does not significantly affect Cr(VI) removal by electrokinetics. (C) 1997 Elsevier Science B.V.

Keywords: Acid, Adsorption, Affect, Anode, Behavior, Capacity, Carbonate, Cathode, Chromium, Clay, Complexation, Composition, Contaminants, Cr(VI), Cr(VI) Adsorption, Cr(VI) Removal, Development, Electrokinetic Remediation, Electrokinetics, Experiments, Hematite, Iron, Iron Oxide, Kaolin, Migration, pH, Presence, Remediation, Remediation, Removal, Soil, Soil Chromium, Soils, Surface, Surface Complexation, Values

? Puppala, S.K., Alshawabkeh, A.N., Acar, Y.B., Gale, R.J. and Bricka, M. (1997), Enhanced electrokinetic remediation of high sorption capacity soil. Journal of Hazardous Materials, 55 (1-3), 203-220.

Full Text: 1997\J Haz Mat55, 203.pdf

Abstract: In unenhanced electrokinetic remediation of metals, electrolysis reactions at the cathode generate a high pH medium that results in metal precipitation and immobilization in the soil. Different enhancement procedures could be utilized at the electrodes to prevent or hinder the generation and transport of this alkaline medium into the soil. This study investigates the feasibility of enhanced extraction of metals from high sorption capacity soils by the use of acetic acid to neutralize the cathode electrolysis reaction and also the use of an ion selective (Nafion^TM) membrane to prevent back-transport of the OH^- generated at the cathode. Synthetic soil samples spiked with lead were used in the testing. Synthetic soils were a mixture of 40% illite, 8% kaolinite, 5% Na-montmorillonite and 47% fine sand representing an illitic deposit. The results demonstrate the feasibility of extracting lead from the deposit, Acetic acid and Nafion enhancement resulted in better removal efficiencies and lead electrodepositions at the cathode compared to unenhanced tests. However, higher energy expenditure and longer processing periods were required when compared to enhanced extraction of lead from kaolinite. Acetic acid tests required less energy than membrane tests. (C) 1997 Elsevier Science B.V.

Keywords: Acetic Acid, Acid, Capacity, Cathode, Electrokinetic Remediation, Electrolysis, Electroosmosis, Enhancement, Expenditure, Extraction, Feasibility, Generation, Immobilization, Kaolinite, Lead, Membrane, Metal, Metal Precipitation, Metals, OH, pH, Precipitation, Remediation, Removal, Samples, Sand, Soil, Soils, Sorption, Sorption Capacity, Synthetic Soil, Testing, Transport

? Yeung, A.T., Hsu, C. and Menon, R.M. (1997), Physicochemical soil-contaminant interactions during electrokinetic extraction. Journal of Hazardous Materials, 55 (1-3), 221-237.

Full Text: 1997\J Haz Mat55, 221.pdf

Abstract: The feasibility of using electrokinetics to extract contaminants from soils has been established by bench-scale laboratory experiments and small-scale field tests, However, the physics and chemistry associated with the innovative remediation technology are not yet fully understood, Many physicochemical reactions occur simultaneously during the process. These reactions may enhance or reduce the cleanup efficiency of the process. They are particularly important in fine-grained soils because the large specific surface area of the soil provides numerous active sites for these reactions. In this paper, several prominent physicochemical soil-contaminant interactions during electrokinetic extraction and their influences on the cleanup efficiency of the technology are discussed, These interactions include: (1) change of zeta potential at the soil particle/pore fluid interface; (2) resistance of the soil-fluid-contaminant system to pH change; and (3) sorption/desorption of reactive contaminants onto or from the soil particle surface and precipitation/dissolution of metallic contaminants in the pore fluid. The effects on these interactions of injecting an enhancement fluid into the contaminated soil are also discussed. In addition, a brief review on the state-of-development of the technology is presented. (C) 1997 Elsevier Science B.V.

Keywords: Change, Contaminants, Contaminated Soil, Edta, Efficiency, Electrokinetic Extraction, Electrokinetics, Electroosmosis, Enhancement, Equations, Experiments, Extraction, Feasibility, Fundamental Formulation, Influences, Interactions, Kaolinite, Metal, Model, pH, Physicochemical Reactions, Porous-Media, Process, Remediation, Removal, Resistance, Review, Soil, Soil-Fluid-Contaminant, Soils, Sorption, Desorption, Specific Surface Area, Surface, Technology, Zeta Potential

Al-Asheh, S. and Duvnjak, Z. (1997), Sorption of cadmium and other heavy metals by pine bark. Journal of Hazardous Materials, 56 (1-2), 35-51.

Full Text: J\J Haz Mat56, 35.pdf

Abstract: Pine bark sorbs cadmium ions from aqueous solutions. A decrease in the bark concentration with a constant cadmium concentration, or an increase in the cadmium concentration with a constant bark concentration, increased cadmium loading per unit weight of the adsorbent. An increase in the initial pH exhibited the same effect. The maximum cadmium uptake was obtained using very fine particles of pine bark. The isotherms presented in this work fit the Freundlich isotherm model reasonably well. A high concentration of soft and hard ions strongly depressed the uptake of cadmium by pine bark. Bark can be used for the sorption of the following metals from aqueous solutions with the indicated order of capacity (mass basis): Pb²⁺ > Cd²⁺ > Cu²⁺ > Ni²⁺ Generally, the same order of capacity was observed in a mixture containing these metal ions. Bark was found to respond better for sorption of metal ions when preloaded with another metal ion.

Keywords: Adsorbent, Adsorption, Bark, By-Products, Cadmium, Copper, Copper, Desorption, Freundlich Isotherm, Heavy Metals, Ions, Lead, Lead, Metal, Metal Ions, Metals, Nickel, pH, Pine Bark, Removal, Soft Ions, Sorption, Water, Zinc

? Arocha, M., Jackman, A. and Mccoy, B. (1997), Erratum to “VOC immobilization in soil by adsorption, absorption, and encapsulation” [J. Haz. Mats. 51 (1996) 131-1491]¹. Journal of Hazardous Materials, 56 (1-2), 225-226.

Full Text: 1997\J Haz Mat56, 225.pdf

Keywords: Adsorption, Encapsulation, Immobilization, Soil, VOC

Gardea-Torresdey, J.L., Gonzalez, J.H., Tiemann, K.J., Rodriguez, O. and Gamez, G. (1998), Phytofiltration of hazardous cadmium, chromium, lead and zinc ions by biomass of Medicago sativa (Alfalfa). Journal of Hazardous Materials, 57 (1-3), 29-39.

Full Text: J\J Haz Mat57, 29.pdf

Abstract: Previous laboratory batch experiments of Medicago sativa (Alfalfa) indicated that the African shoots population had an appreciable ability to bind copper(II) and nickel(II) ions from aqueous solution. Batch laboratory pH profile, time dependency and capacity experiments were performed to determine the binding ability of the African shoots for cadmium(II), Chromium(III), chromium(VI), Lead(II), and zinc(II). Batch pH profile experiments for the mentioned ions indicated that the optimum pH for metal binding is approximately 5.0. Time dependency experiments for all the metals studied showed that metal binding to the African alfalfa shoots occurred within 5 min. Binding capacity experiments revealed the following amounts of metal ions bound per gram of biomass: 7.1 mg Cd(II), 7.7 mg Cr(III), 43 mg Pb(II), and 4.9 mg Zn(II). However, no binding occurred for chromium(VI). Nearly all of the metals studied were recoverable by treatment with 0.1 M HCl. Column experiments were performed to study the binding of Cd(II), Cr(III), Cr(VI), Pb(II) and Zn(II) to silica-immobilized African alfalfa shoots under flow conditions. These experiments showed that the silica immobilized African alfalfa shoots were effective for removing metal ions from solution, and over 90% of the bound Pb(II), Cu(II), Ni(II), and Zn(II), and over 70%Cd(II), were recovered after treatment with 10 bed volumes of 0.1 M HCl. The results from these studies will be useful for a novel phytofiltration technology to remove and recover heavy metal ions from aqueous solution. (C) 1998 Elsevier Science Ltd. All rights reserved.

Keywords: Phytofiltration, Alfalfa, Medicago Sativa, Heavy Metal Binding, Recovery

Viraraghavan, T. and Alfaro, F.D. (1998), Adsorption of phenol from wastewater by peat, fly ash and bentonite. Journal of Hazardous Materials, 57 (1-3), 59-70.

Full Text: J\J Haz Mat57, 59.pdf

Abstract: This study examined the effectiveness of less expensive adsorbents such as peat, fly ash and bentonite in removing phenol from wastewater by adsorption. Batch kinetic studies showed that an equilibrium time of 16, 5 and 16 h was needed for the adsorption of phenol on peat, fly ash and bentonite respectively. Batch studies indicated that the optimum pH for the adsorption of phenol on peat, fly ash and bentonite was between 4.0 to 5.0 at 21±1C. The adsorption of phenol on peat and bentonite was described well by the Freundlich isotherm whereas the Langmuir isotherm described the adsorption of phenol on fly ash. Feat, fly ash and bentonite were found to adsorb 46.1%, 41.6%, and 42.5% phenol respectively from an initial concentration of approximately 1 mg/l.

Keywords: Adsorption, Phenol, Peat, Fly Ash, Bentonite

? Lin, S.H. and Chen, Y.W. (1998), Gas-phase adsorption isotherms and mass transfer characteristics of 1,1-dichloro-1-fluoroethane (HCFC-141b) by various adsorbents. Journal of Hazardous Materials, 57 (1-3), 193-207.

Full Text: 1998\J Haz Mat57, 193.pdf

Abstract: Experiments have been conducted to investigate gas-phase adsorption characteristics of 1,1-dichloro-1-fluoroethane (HCFC-141b) by activated carbon fiber (ACF), extruded activated carbon (EAC), granular activated carbon (GAC), activated alumina and molecular sieve. HCFC-141b is currently regarded as an excellent replacement for CFC-11, a foaming agent widely used in the rigid polyurethane foam industries. Performances of HCFC-14lb adsorption were characterized by the equilibrium adsorption capacity, time to reach equilibrium and desorption efficiency of adsorbent. A simple thermal treatment process with proper operating temperature and treatment duration was found to be effective for pretreatment of fresh adsorbents and regeneration of exhausted ones. The empirical Freundlich adsorption isotherm was observed to adequately represent the equilibrium adsorption data. A mass transfer model based on the pseudo steady state squared driving force was adopted to describe the mass transfer process of HCFC-14lb adsorption. (C) 1998 Elsevier Science B.V.

Keywords: ACF, Activated Alumina, Activated Carbon, Activated Carbon Fiber, Activated Carbon-Fibers, Adsorbent, Adsorbents, Adsorption, Adsorption Capacity, Adsorption Isotherm, Adsorption Isotherms, Agent, Alumina, Capacity, Carbon, Catalyst, CCl₂F₂, CFC-113, Chlorofluorocarbons, Desorption, Destruction, Dichlorodifluoromethane, Efficiency, Equilibrium, Foam, Force, Freundlich, Freundlich Adsorption Isotherm, GAC, Gas Phase, Gas Phase Adsorption, Gas-Phase, Gas-Phase Adsorption, Granular Activated Carbon, Hcfc-141b, Hydrocarbons, Industries, Isotherm, Isotherms, Mass Transfer, Mass Transfer Model, Model, Ozone, Polyurethane, Polyurethane Foam, Pretreatment, Process, Regeneration, Replacement, State, Temperature, Thermal Treatment, Thermal-Decomposition, Transfer, Treatment, Various Adsorbents

? Semer, R. and Reddy, K.R. (1998), Mechanisms controlling toluene removal from saturated soils during in situ air sparging. Journal of Hazardous Materials,