Papers by Kalliat Valsaraj
Open Journal of Air Pollution, 2017
Experiments on the reactions of OH radicals in thin films of water were conducted in a photochemi... more Experiments on the reactions of OH radicals in thin films of water were conducted in a photochemical reactor. The OH radical reactivity of a biogenic molecule (methyl jasmonate) was observed to be much larger in thin films of water than in the bulk aqueous phase. The pseudo-first order reaction rate was enhanced by an order of magnitude on a 38-micron film compared to the bulk liquid. However, the first order rate constant increased by 349%. This has implications in atmospheric systems like fog and mist which have large specific surface areas. The enhanced reactivity is attributable to both the partial solvation and faster diffusion at the air-water interface compared to the bulk liquid.
Soil and Sediment Contamination: An International Journal, 2012
Abstract This study investigated the mercury uptake capacity of synthetic mackinawite regarding i... more Abstract This study investigated the mercury uptake capacity of synthetic mackinawite regarding its surface modification with L-cysteine. Mackinawite (FeS) is an excellent material for mercury uptake from anoxic contaminated sediments. However, one limitation to its use is the low oxidation stability; it is easily transformed when applied to natural sediments. The modification of mackinawite with L-cysteine improves its oxidation stability, making it a promising material to be used in sediment remediation by in-situ capping. The results ...
To ensure the safe disposal of nuclear waste, understanding the release process of radionuclides ... more To ensure the safe disposal of nuclear waste, understanding the release process of radionuclides retained in the nuclear waste forms is of vital importance. Iodoapatite Pb9.85(VO4)6I1.7, a potential waste form for iodine-129, was selected as a model system for ceramic waste forms in this study to understand the effect of aqueous species on iodine release. Semi-dynamic leaching tests were conducted on bulk samples in cap-sealed Teflon vessels with 0.1 mol/L NaCl, Na2CO3, Na3PO4, and Na2SO4 solutions under 90 °C, fixed sample surface area to solution volume ratio of 5/m, and periodic replacement of leaching solutions. The reacted solutions were then analyzed by Inductively Coupled Plasma-Mass Spectrometry and Inductively Coupled Plasma-Optical Emission Spectrometry; the leached surfaces were characterized by X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. The result shows that, compared to deionized water, the ion-rich solutions enhanced the iodine release a...
Toxics
This study investigates the air pollution-induced mortality rate during the second wave of COVID-... more This study investigates the air pollution-induced mortality rate during the second wave of COVID-19, which claimed several thousand lives in the capital city of India, New Delhi, even during a lockdown period. Delhi is a hotspot of unhealthy air quality. During the second wave of COVID-19 in 2021, surface ozone levels were observed to be higher, which had a direct impact on lung function, thereby making people more susceptible to COVID-19. The correlation coefficient between surface ozone concentration and mortality has been observed to be 0.74 at a 95% confidence level. This work focuses on the plausible impact and feedback of poor air quality induced by the burning of open-air funeral pyres due to the increased COVID-19 mortality rate in New Delhi, estimated by using an epidemiological model (AirQ+) of the World Health Organization. The mortality rate estimated quantitatively with the aid of AirQ+ is 1.27 excess deaths per 100,000 population due to surface ozone from pyre burning....
Chemical Product and Process Modeling, 2020
Debottlenecking and estimating fouling in a clarifier piping system for the expansion of an exist... more Debottlenecking and estimating fouling in a clarifier piping system for the expansion of an existing chemical manufacturing facility in the U.S. Gulf Coast was analyzed and modified. The existing clarifier piping system fitting data was gathered for the real-world operation from the field. This data was used in the Applied Flow Technology (AFT) Fathom, a program used to study hydraulic systems. The hydraulic results with and without recommended piping modifications along with changing piping roughness factors were also analyzed. The two piping roughness factor cases tested were roughness of 0.152 mm and fouling of 25.4 mm. The AFT Fathom results showed that without piping modifications and specifying fouling of 25.4 mm, required flow cannot be established due to insufficient driving force for liquid movement. The measured field flow data confirmed that the reduced clarifier capacity was due to high pressure losses in the hydraulic system. Also, it was found that the existing clarifi...
Processes, 2021
Waste generated during regeneration of Ion Exchanger (IX), used for deionizing water, needs to be... more Waste generated during regeneration of Ion Exchanger (IX), used for deionizing water, needs to be neutralized before it can be discharged back to a clean water source. An efficient and novel process is disclosed that minimizes the neutralization volume and chemicals required for pH adjustment. The currently employed neutralization setups in the industry are environmentally unsustainable. Various neutralization setups were studied for treating waste generated from IX regeneration. From the collected plant data, the treatment requirements of waste streams generated during regeneration of IX beds were analyzed. An efficient neutralization setup was developed to lower the operating and capital costs by eliminating the need of some equipment and by lowering the neutralization volume. The new process results in considerable savings compared to currently used processes in the industry and is environmentally benign. The improved neutralization setup proposed in this work has achieved a 63% ...
Water Science and Technology, 1993
Natural colloids are part of the carbon cycle arising from sediment diagenesis. Natural colloids ... more Natural colloids are part of the carbon cycle arising from sediment diagenesis. Natural colloids can be quantified as the dissolved organic carbon (DOC) present in the pore-water of sediment beds. In this paper we demonstrate that DOC is mobile in a system in which the dominant transport mechanism is Brownian diffusion. A simple model which assumes constant physico-chemical properties for the DOC adequately predicts the DOC release rate from a sediment bed in a microcosm. A single adjustable parameter, the water diffusivity, is used to fit the model to the experimental data. The experimental diffusivities obtained from the fitted data agree well with previously presented values.
Journal of Atmospheric Chemistry, 2015
Aldehydes and ketones, ubiquitous air, cloud, and fog water pollutants, are precursors to seconda... more Aldehydes and ketones, ubiquitous air, cloud, and fog water pollutants, are precursors to secondary organic aerosol formation and photochemical smog. Traditional aldehyde and ketone determination methods involve the addition of 2,4-dinitrophenylhydrazine (DNPH) as a derivatization agent, but many require a large sample volume or a lengthy extraction/concentration process. For fog water, where the sample size is inherently small, a DNPH derivatization method, based on U.S. EPA Method 8315A, was developed to combat this issue. In this method, a manual injection online concentration system in conjunction with HPLC was used, eliminating all liquid-liquid extraction and concentration steps and reducing the required sample volume. Hence, concentration and separation were combined in a single step. Using this injection method shortened the procedure time and also lowered the limit of detection to the nanomolar range. In this study, fourteen fog water samples, collected from October 2012 through April 2014 in Baton Rouge, LA, were analyzed for the concentration of aldehydes and ketones in order to test the feasibility of this method. Dissolved organic content (DOC), ionic concentration, and pH were measured. Formaldehyde, acetaldehyde, acrolein, butyraldehyde, benzaldehyde, and acetone were quantified. The DOC of the collected fog samples varied between 6.2 and 262.2 mgC/L. The wide range of organic content in the fog water samples corresponds to a diverse sample set, highlighted by the large variation of observed acetone concentration (under 5 nM to 1.05 mM). However, formaldehyde had a relatively stable concentration between each event (0.5 to 4.5 μM).
Atmospheric Environment. Part A. General Topics, 1993
The unusual degree of enrichment of hydrophobic organics in fogwater droplets reported by several... more The unusual degree of enrichment of hydrophobic organics in fogwater droplets reported by several investigators can be interpreted as a result of (a) the effects of temperature correction on the reported enrichment factors, (b) the effects of colloidal organic matter (both filterable and non-filterable) in fog water and (c) the effects of the large air-water interracial adsorption of neutral hydrophobic organics on the tiny fog droplets. The enrichment factor was directly correlated to the hydrophobicity (or the activity coefficient in water) of the compounds, as indicated by their octanol-water partition constants. Compounds with large octanol-water partition coefficients (high activity coefficients in water)"showed the largest enrichment. Available experimental data on the adsorption of hydrophobic compounds at the air-water interface and on colloidal organic carbon were used to show that the large specific air-water interfacial areas of fog droplets contribute significantly to the enrichment factor.
Water Research, 1991
Solvent sublation in a continuous countercurrent mode for the removal of three hydrophobic organi... more Solvent sublation in a continuous countercurrent mode for the removal of three hydrophobic organic compounds (viz. pentachlorophenol, 2,4,6-trichlorophenol and naphthalene) from water into mineral oil was investigated. Mathematical simulations of experimental results were achieved using a steady state "stagewise" model along with the determination of key hydrodynamic parameters for the bubble column such as bubble radius and number of equilibrium stages. The importance of using bubbles of small radii even at high air flow rates was apparent.
The Journal of Physical Chemistry A, 2012
The adsorption of gas-phase naphthalene and ozone molecules onto air/ice interfaces coated with d... more The adsorption of gas-phase naphthalene and ozone molecules onto air/ice interfaces coated with different surfactant species (1-octanol, 1-hexadecanol, or 1-octanal) was investigated using classical molecular dynamics (MD) simulations. Naphthalene and ozone exhibit a strong preference to be adsorbed at the surfactant-coated air/ice interfaces, as opposed to either being dissolved into the bulk of the quasi-liquid layer (QLL) or being incorporated into the ice crystals. The QLL becomes thinner when the air/ice interface is coated with surfactant molecules. The adsorption of both naphthalene and ozone onto surfactant-coated air/ice interfaces is enhanced when compared to bare air/ice interface. Both naphthalene and ozone tend to stay dissolved in the surfactant layer and close to the QLL, rather than adsorbing on top of the surfactant molecules and close to the air region of our systems. Surfactants prefer to orient at a tilted angle with respect to the air/ice interface; the angular distribution and the most preferred angle vary depending on the hydrophilic end group, the length of the hydrophobic tail, and the surfactant concentration at the air/ice interface. Naphthalene prefers to have a flat orientation on the surfactant coated air/ice interface, except at high concentrations of 1-hexadecanol at the air/ice interface; the angular distribution of naphthalene depends on the specific surfactant and its concentration at the air/ice interface. The dynamics of naphthalene molecules at the surfactant-coated air/ice interface slow down as compared to those observed at bare air/ice interfaces. The presence of surfactants does not seem to affect the self-association of naphthalene molecules at the air/ice interface, at least for the specific surfactants and the range of concentrations considered in this study.
Soil and Sediment Contamination: An International Journal, 2002
Remedial dredging of bed sediments in rivers and lakes results in the suspension of sediment soli... more Remedial dredging of bed sediments in rivers and lakes results in the suspension of sediment solids in the water column, which can potentially be as a source for evaporation of hydrophobic organic compounds (HOCs) associated with the suspended solids. Laboratory experiments were conducted in an oscillating grid chamber to simulate the suspension of contaminated sediments with air flowing over the surface of the water column. A contaminated field sediment from Indiana Harbor Canal (IHC) and a laboratory inoculated ...
Separations Technology, 1991
Two nonfoaming separations, bubble fractionation and solvent sublation, are reviewed. These unit ... more Two nonfoaming separations, bubble fractionation and solvent sublation, are reviewed. These unit operations are interfacial (gas bubble-liquid) separation techniques that have significant potential for the removal of several metal ions and hydrophobic organic compounds of environmental significance from aqueous solutions. Experimental and theoretical work on the two processes relating the effects of process variables are summarized. The underlying mechanisms of the two processes are identical although solvent sublation is found to have significant advantages over bubble fractionation, air stripping, and the related process of solvent extraction. Specifically, sublation can achieve a greater degree of removal than extraction, can remove both volatile and nonvolatile compounds, unlike air stripping, and has less sensitivity to axial dispersion than bubble fractionation. The potential use of these processes for large-scale separations is examined; the limitations and need for further work are clearly evident. Questions of scale-up, bubble generation, and reduction of axial dispersion all require further investigation.
Journal of Environmental Monitoring, 2012
Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants in the atmosphere, predominantly... more Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants in the atmosphere, predominantly known for their toxicity. Although there has been substantial work on the atmospheric degradation of PAH, little is known about how the presence of atmospheric droplets (e.g., a fog cloud) affects the fate of PAH. In order to assess the processing of PAH and their corresponding oxidation products during a fog event, two field-sampling campaigns in Fresno, CA and Davis, CA were conducted. The simultaneous evaluation of concentrations of the PAH and oxygenated polycyclic aromatic compounds (OPAC) in the gas phase, particulate matter and fog water droplets before, during and after fog allows for the characterization of transformative and transport processes in a fog cloud. By tracking the ratio of OPAC to PAH in the individual atmospheric phases, two major polycyclic aromatic compounds-processing pathways can be identified: (i) the dissolution of OPAC from particulate matter and (ii) the uptake and oxidation of PAH in the fog water droplets. Wet deposition steadily decreases the pollutant concentration in the fog cloud droplets during a fog event; however, uptake and concentration via evaporative water loss upon the dissipation of a fog cloud cause an increase in the atmospheric pollutant concentration.
Journal of Environmental Engineering, 1996
Organic colloids resulting from sediment diagenesis in porewaters are transported across the sedi... more Organic colloids resulting from sediment diagenesis in porewaters are transported across the sediment-water interface via Brownian diffusion. The sediment selected for this study was from the University Lake, Baton Rouge, La. The effects of electrolytes on the sediment-to-water flux of colloids varied depending on the type and concentration of the electrolyte. An ionic strength of 0.5 M reduced the flux of colloids; the effect being greater for KCl than for NaCl at the same ionic strength. The effects of different electrolytes (viz., NaCl, KCl, and ...
Journal of Colloid and Interface Science, 2006
Using a new computational model, we have studied the dynamics and coalescence of a pair of two-di... more Using a new computational model, we have studied the dynamics and coalescence of a pair of two-dimensional droplets in pressure-driven flow through a constricted capillary tube, which is a prototype problem for the analysis of the interaction of emulsion droplets in porous media. We present simulations that quantify the effects of various system parameters on the droplet stability. These include the capillary number, the interfacial tension, the suspended-to-suspending-phase viscosity ratio, the valence and concentration of added electrolytes, the droplet-to-poresize ratio, the pore-body-to-throat-size ratio, and the type of pore geometry. Our simulations show that the capillary number Ca plays an important role in determining whether the drops coalesce. At low Ca, drops deform only slightly and coalescence occurs at the entrance of the pore throat, whereas significant deformation enables the drops move through the pore without coalescence at high Ca. Coalescence is favored at intermediate values of the viscosity ratio. The destabilizing effect of added electrolytes is found to be insignificant for 10-µm drops, but significant for micronsize drops. Among the geometric-related parameters, the drop-to-pore-size ratio is the most significant.
Estuaries, 1998
The development of models of contaminant migration via bioturbation is the focus of this work. Tw... more The development of models of contaminant migration via bioturbation is the focus of this work. Two models are developed from two types of organism activity: organisms that mix sediment vertically (e.g., by burrowing) and those that mix sediment horizontally by movement confined to a given depth below the sediment-water interface. The models are compared to experimental measurements with deposit-feeding oligochaetes that are of the burrowing type. Both models provide a good description of the contaminant flux and average concentration profile. It is not possible to differentiate between the models on the basis of the available data.
Atmospheric Environment, 1994
Semi-volatile organic compounds (SOCs) are present in the atmosphere as vapors and are adsorbed t... more Semi-volatile organic compounds (SOCs) are present in the atmosphere as vapors and are adsorbed to particulate matter. Knowledge of the gas-to-particle distribution of these compounds is important in understanding their atmospheric fate and transport. A baseline experimental study to estimate the vapor-and particle-phase-associaled concentrations of the SOCs (specifically. polycyclic aromatic hydrocarbons, PAHs) in the Baton Rouge (Louisiana) air was carried out. A comparison of the levels of concenlrations of PAHs obtained in Baton Rouge to those obtained in other parts of the world is made. The sampling artifacts associated with a traditional high-volume sampler introduced errors in the estimation of the partition coefficient. DiRerent air sampling procedures (a modified.low-volume sampler and an annular denuder) were evaluated in order to obtain a more accurate measure of the gas-to-particle partition coefficient. The effects of temperature and precipitation on the partitioning of PAHs between the vapor and particulate phase were ascertained.
Atmospheric Chemistry and Physics, 2013
The goal of this research is to characterize the irreversible desorption of hydrophobic organic c... more The goal of this research is to characterize the irreversible desorption of hydrophobic organic contaminants to sediments and couple with the assessment of bioavailability to bioturbating macroflora, microorganisms, and aquatic plants. The specific objectives of the project included:• determine the extent of irreversible adsorption to historically contaminated and laboratory prepared sediments and the effect of process variables such as T, pH, TDS, OC, flow and weathering on that adsorption.• determine the impact of irreversible (or ...
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Papers by Kalliat Valsaraj