No description available.

Equilibrium isotherms and the adsorption kinetics of heavy metals onto chitosan were studied experimentally. Chitosan, a biopolymer produced from crustacean shells, has applications in various areas, particularly in drinking water and wastewater treatment due to its ability to remove metallic ions from solutions. The adsorption capacity of chitosan depends on a number of parameters: deacetylation degree, molecular weight, particle size and crystallinity. The purpose of this work was to study the adsorption of copper, zinc, mercury, and arsenic on chitosan produced from shrimp shells at a laboratory level. The experimental work involved the determination of the adsorption isotherms for each metallic ion in a batch system. The resulting isotherms were fitted using the Langmuir model and the parameters of the equation were determined. Kinetic studies of adsorption for different metallic ions at different concentrations and with different particle sizes were performed in batch and column systems. Simplified models such as pseudo-first-order, pseudo-second-order, and intra-particle diffusion equations were used to determine the rate-controlling step. Some preliminary studies were carried out to address the application of chitosan as an adsorbent in the removal of heavy metals or other metallic ions from natural water and wastewater. The regeneration of chitosan was also studied. The results showed that the adsorption capacity depends strongly on pH and on the species of metallic ions in the solution. The optimum pH value for the metallic cation adsorption was between 4 and 6, whereas for arsenic adsorption it was about 3. When the pH is not controlled, the adsorption capacity is independent of the initial pH with the solution reaching a final pH of about 7. It was also found that the Langmuir equation described very well the experimental adsorption data for each metallic ion. The adsorption capacity for the metals on chitosan follows the sequence Hg>Cu>Zn>As. The study of the adsorption kinetics of these metallic ions shows that the particle size has a significant influence on the metal uptake rate for copper; but that it has only a slight influence on the adsorption rate of zinc and mercury in the range studied. Arsenic adsorption exhibited an interesting behaviour which depends strongly on the pH of the solution; the uptake increased at short adsorption times and then decreased at long times. The analysis of kinetic models showed that the pseudo-second-order adsorption mechanism is predominant, and the overall rate of the metallic ion adsorption process is therefore controlled by adsorption reactions and not by mass transfer for the range of particle sizes examined in this study. With regard to the regeneration of chitosan, it was found that sodium hydroxide is a good agent for zinc and arsenic desorption, whereas ammonium sulphate and sodium chloride were the most suitable for copper and mercury desorption, respectively. The ability of chitosan to remove arsenic from natural water, and copper and zinc from mining waste water was verified. The use of these results for designing purposes is a subject for future work. / QC 20101104

No description available.

Despite claims of nearly 100% access to potable drinking water in the US, issues of drinking water quality, accessibility, and equity persist in many regions of the country. Drinking water is a common health concern in rural communities, where social, geographic, and economic challenges can inhibit the provision of reliable municipal water. Households without access to municipal water often rely on private wells, which are solely the responsibility of the homeowner to test, treat, and maintain, or roadside springs. These water sources often do not employ water treatment and users can therefore be uniquely susceptible to environmental contaminants. The goal of this research was to examine point-of-use (POU) treatment options that can be used by individuals to improve their drinking water quality and reduce exposure to common contaminants prior to consumption. Two drops (~0.10 mL) of unscented, household bleach in one gallon of spring water is a simple, low-cost treatment option that successfully inactivates total coliform and E. coli and provides an appropriate free chlorine residual (> 0.5 mg/L) over a 1-month time period, without exceeding free chlorine taste thresholds (< 2 mg/L). Efforts to distribute information on this disinfection protocol to spring users in southern West Virginia and southwestern Virginia were well-received; however, only 60% of surveyed spring users report that they plan to implement the protocol. POU faucet filters have been successfully implemented in homes reliant on municipal water to reduce metal contaminant levels in drinking water. Few studies have assessed the effectiveness of these filters in improving water quality in homes reliant on private wells. Faucet-mounted POU filters distributed to homes reliant on private wells in Virginia and southern West Virginia statistically significantly lowered levels of Ba, Cd, Cr, Total Coliform, U, Cu, Pb, Al, Fe, Mn, Zn, and Sr in tap water. However, levels of many contaminants of interest still exceeded at least one Safe Drinking Water Act regulation/recommendation in several filtered samples. Additionally, less than half of study participants reported that they liked using the filters with several citing issues with flowrate. Faucet-mounted POU filters can also be a useful tool in assessing exposure to contaminants at the tap. The acid flow-through method of metals recovery has previously proven to be successful in recovering dissolved Pb from dosed filters. In this study, the acid flow-through extraction method was applied to water spiked with high or low levels of Pb, Fe, or Cu. While faucet-mounted activated carbon filters successfully removed Pb and Cu from dosed influent (>91% removal), filter behavior under influent Fe concentrations of greater than 300 ppb was extremely variable. The acid flow-through method of metals extraction provided some recovery from filters dosed with high and low concentrations of Pb (38.9-70.4%). Recovery of Cu and Fe was variable, likely in part due to Fe and Cu leaching from filter media, suggesting that alternative methods of metals extraction and recovery from POU faucet filters dosed with Fe and Cu, or other common water contaminants (e.g., As, Ba, Cd), must be explored. While POU treatment can be useful in improving drinking water quality in rural households, limitations to adoption persist and must be addressed along with efforts to protect drinking water quality in homes in a more permanent, sustainable way. / Doctor of Philosophy / Drinking water quality is a common health concern in rural communities, where social, geographic, and economic challenges can make municipal water quality unreliable. Households without access to municipal water often use private wells and sometimes roadside springs for drinking water. These water sources are often untreated which can expose users to environmental contaminants such as bacteria or metals. The goal of this research was to study point-of-use (POU) treatment options that can be used by individuals looking to improve their drinking water quality and reduce their exposure to common contaminants, perhaps while waiting for more permanent improvements and upgrades. Household bleach is a simple, low-cost way of lowering levels of bacteria in roadside spring water that is being used as drinking water. Two drops of unscented, household bleach in one gallon of spring water successfully kills total coliform and E. coli bacteria and provides an enough leftover chlorine to continue to disinfect the water for 1-month. This information was given to spring users in southern West Virginia and southwestern Virginia and, while most people who provided feedback found the information useful, only 60% of surveyed spring users report that they plan to implement this protocol. Point-of-use faucet filters have been found to successfully reduce metals contaminant levels in drinking water in homes that use municipal water. However, few studies have tested the effectiveness of POU faucet-mounted filters in lowering contaminant levels in water in homes reliant on private wells. Faucet-mounted POU filters given to homes reliant on private wells in Virginia and southern West Virginia lowered levels of many contaminants of interest in tap water, including lead, copper, iron, and total coliform bacteria. However, in some of the filtered samples, levels of many of these contaminants were higher than at least one Safe Drinking Water Act regulation. Less than half of study participants reported that they liked using the filters with several stating that they had issues with low flowrate. Faucet-mounted POU filters can also be a useful tool in better understanding exposure to contaminants at the tap. The acid flow-through method of metals recovery has previously proven to be successful in recovering lead, and other metals, that are collected inside the filters during water treatment. In this study, an extraction method using acid was tested on filters that treated water with high or low levels of lead, iron, or copper. The filters were successful in removing lead and copper from test water, but filters were not as consistently successful in removing iron from test water. The extraction method using acid provided some recovery from filters dosed with high and low concentrations of lead (38.9-70.4%). However, recovery of copper and iron was more inconsistent, suggesting that a different method of metals recovery may be necessary. While POU treatment can be useful in improving drinking water quality in rural households, there are limits to how useful it is in certain situations, such as when treating water with extreme water quality. In order to make sure rural households have access to safe drinking water, these limits need to be addressed and efforts need to be made to figure out a way to protect and supply drinking water in a more permanent way.

No description available.

The objective of this work was the development of an efficient adsorbent for irreversible immobilization of heavy metals in contaminated soils. The adsorbent was prepared by pillaring montmorillonite with silica followed by the grafting of a chelate ligand onto its surface. Its structure was studied by the Brunauer, Emmett, and Teller Method adsorption of N2, Dynamic Light Scattering, and Scanning Electron Microscopy. The adsorption capacity of the organoclay was measured by its mixing with contaminated kaolin soil samples and by analysis of heavy metal contents in leachate. The adsorbent was efficient in immobilization of heavy metals in both neutral aqueous and acidic media. In addition, the adsorbent was efficient in environmental samples reducing the concentration of iron in all samples in aqueous and acidic media. As a result, the adsorbent can be used for reduction of heavy metal leaching from contaminated sites.

A reversed phase-high performance liquid chromatography method has been developed that is capable of resolving lead and cadmium diethyldithiocarbamate complexes. The method does not require the presence of hazardous solvents to optimize peak shape and resolution; the mobile phase consists of methanol, water, and a surfactant. Tobacco samples were chemically oxidized and reacted with sodium diethyldithiocarbamate reagent prior to analysis using the HPLC method. The lead diethyldithiocarbamate determination was compromised by the presence of a significant interference in the analysis; lead determinations in 10 foreign and domestic tobacco samples ranged from 27.14 to 134.84 μg/g. The cadmium diethyldithiocarbamate determination was not adversely affected by interferences. Cadmium determinations in 10 foreign and domestic tobacco samples ranged from 0.89 to 6.96 μg/g. The tobacco samples were also analyzed using atomic absorption spectrometry. Foreign tobacco brands that contained clove as a spice showed lower levels of cadmium and lead.

Concentrations of Ni, Cu, Zn, Fe, Cd, and Pb were determined in six different creeks within a city in Tennessee using Atomic Absorption Spectrophotometer. Mean concentrations of Ni, Cu, Zn, Cd, Pb, and Fe in the sites examined reveal that they exceed the USEPA recommended limits. High concentrations of Cu (0.130 mg/L), Zn (13.7 mg/L), Ni (0.267 mg/L), and Cd (0.010 mg/L) were observed in site B and Fe (3.01 mg/L) in site E relative to other sites. The concentration of Pb (0.795 mg/l) was higher in site A. Higher concentrations of Cu, Zn, and Fe were detected in samples collected in the month of January and Cd in samples collected in the month of June. Pb and Ni concentrations did not show any significant difference with respect to dates of sample collection. Their presence in the environment on a particular day depends on the type and volume of human activities.

The concentrations of heavy metals (Cd, Cu, Fe, Ni, Pb, Zn) were measured in water, and fish samples caught from the pond at Fishery Park in Unicoi County, TN. The water samples were collected once a week for 8 weeks. The amounts of metals in the muscle tissues, gill, and liver of the two fish species were measured. This was to determine if any correlation exists between the metal contents in water and those in the fish samples. The concentration ranges for the heavy metals found in the water samples are as follows: Zn 0.04-0.13; Cu, 0.00-0.00; Pb, 0.00-0.59; Cd, 0.0067-0.0071; Fe, 0.208-0.512; and Ni, 0.044-0.270 ppm. The concentration range for the heavy metals found in the fish tissues are as follows: Zn 0.0-0.48; Cu, 0.00-0.00; Pb, 0.00-0.43; Cd, 0.00-99.7; Fe, 25.7-1245.5; and Ni, 0.00-268.5 ppm. There was a strong correlation found between the water and fish tissue samples.

Water pollution represents one of the major concerns of the modern world, after scientific and industrial development that generates hazardous organic and inorganic contaminants. Biochar (BC) has gained tremendous attention in the past decade as a cheap and efficient adsorbent for organic and inorganic contaminants from aqueous solutions. BC is considered to be a low-cost alternative to activated carbon, however, BC typically suffer performance reductions due to their low surface areas and poor mechanical properties. The main objective of this work is to develop novel biochar materials by modifying the biochar surface for the removal of organic and inorganic contaminants from water. In recent years, biochar modifications involving various methods such as, acid/base treatment, impregnation of mineral sorbents, functional groups incorporation, steam activation and magnetic modification have been widely studied. Chapter I summarizes these biochar modification methods. In Chapter II, Chitosan-Modified fast pyrolysis BioChar (CMBC) was used to remove Pb2+ from water. CMBC was made by mixing pine wood biochar with a 2% aqueous acetic acid chitosan (85% deacylated chitin) solution followed by treatment with NaOH. CMBC removed more Pb2+ than non-modified biochar suggesting that modification with chitosan generates amine groups on the biochar surface which enhance Pb2+ adsorption. Chapter III describes the fast nitrate and fluoride adsorption and magnetic separation from water on iron oxide particles dispersed on Douglas Fir biochar. Nitrate and fluoride adsorption occurred by electrostatic attraction over the wide 2 to 10 pH range. In the chapter IV, aniline and nitrobenzene removal from water was studied using magnetized and nonmagnetized Douglas Fir biochar. The adsorption of aniline and nitrobenzene occurred mainly through pi-pi electron interactions over the wide 2 to 12 pH range and H-bonding. The surface morphology, chemistry, and composition of the modified biochars were examined by SEM, SEM-EDX, TEM, PZC, XPS, XRD, FTIR, TGA, DSC, elemental analysis, and surface area measurements.