Environmental Chemistry Commons^™

Temperature-Dependent Kinetic Studies Of Arsenicals Adsorption From Solution To Hematite Nanoparticles, Sara Soldoozy

Theses and Dissertations (Comprehensive)

Surface chemistry is the study of the chemical and physical phenomena that transpire at interfaces such as liquid-solid, solid-gas, liquid-gas, and liquid-liquid. To study the reactions occurred at the surfaces, surface sensitive techniques come to play. Adsorption of arsenical compounds (liquid adsorbate), particularly arsenate (iAs) and dimethylarsinic acid (DMA), to the surface of iron bearing materials (solid adsorbent) that frequently are found in geosorbents such as hematite (Fe₂O₃) has been studied in this thesis. Arsenical compounds can pollute the environment through natural sources and anthropogenic activities, and ultimately contaminate water. Absorbing these pollutants to a material …

Toxic Gas Sensing On Nanoporous Carbons, Nikolina-Eleni Travlou

Dissertations, Theses, and Capstone Projects

Activated carbons, either synthetic, developed in our laboratory, or commercial, were prepared or further modified, in order to introduce specific heteroatoms such as oxygen, nitrogen and sulfur to their matrices. Chips coated with thin layers of the carbon samples were used for the sensing of gaseous ammonia. They were exposed to continuous cycles of various ammonia concentrations (10-500 ppm), and changes in normalized resistance were analyzed. In all cases linear responses were recorded and the chips reached sensitivities as high as 31%, which are comparable to those of modified graphene-based sensors. The applied specific surface chemical modifications were an effective …

Comprehensive Silica Removal With Ferric Compounds For Industrial Wastewater Reuse, Ehren D. Baca

Civil Engineering ETDs

Cooling towers, integrated circuit (IC) manufacture and reverse osmosis (RO) generate copious amounts of wastewater high in colloidal and reactive silica inhibiting on-site or synergistic reuse. Silica present in cooling water can reach solubility limits via evaporation and form impervious scale on heat transfer surfaces that decreases efficiency. When water is treated by RO operating at high rejection, silica forms difficult-to-remove scale on the membrane feed side in the form of glassy patches and communities of aggregate particles, inhibiting aspirations for zero liquid discharge. Current methods for silica scale mitigation include abundant dosing with chemical antiscalents or complex operating schemes. …

Functionalized Silica Gel For Adsorption Of Cesium From Solution, Kenneth Marshall Seaton Iii

Electronic Theses and Dissertations

Mesoporous silica gel containing embedded phosphotungstic acid (PTA) was synthesized by sol-gel co-condensation of tetraethyl orthosilicate with PTA in acidic media. The obtained material had high Brunauer-Emmett-Teller Theory (BET) surface area and pore volume. A characteristic band of the Keggin structure of PTA was present in its FT-IR spectrum while its X-ray diffraction patterns were absent. This proved the embedding of PTA on a sub-molecular level and not as a second phase. Acidic sites were determined by neutralization with base in aprotic solvent, followed by titration of the remaining base with an acid. The material demonstrated high adsorption capacity of …

Specific Phosphate Sorption Mechanisms Of Unaltered And Altered Biochar, Kathryn D. Szerlag

Masters Theses

Biochar has been shown to act as an effective sorbent for many organic and inorganic contaminants (including phosphate) and can help to improve the quality of our fresh water resources by preventing eutrophication. Most of the high efficiency biochar phosphate-adsorbent feedstocks are modified with chemical pretreatment, phytoremediation or anaerobic digestion to accumulate desired elements. The main objectives of this project were to first engineer magnesium (Mg) and calcium (Ca) altered biochar by chemical pretreatment followed by pyrolysis at either 350 or 550°C and evaluate their phosphate adsorption rate and potential as compared to their unaltered counterparts. Determination of surface physiochemical …

Adsorption Of Antibiotics By Vermiculite, Mosa J. Ferdous

Dissertations and Theses

The occurrence of residual antibiotics in the environment has been a worldwide issue and warrants the development of inexpensive yet effective methods for antibiotics removal from contaminated water. In this thesis work, the adsorption of four antibiotics, namely chlorotetracycline (CTC), oxytetracycline (OTC), ofloxacin (OFL), and enrofloxacin (ENR), onto natural vermiculite has been studied using batch (static) and column (dynamic) adsorption techniques. The Langmuir and Freundlich isotherm models were initially used to explain the adsorption processes. The separation factor (RL) values derived from the Langmuir model and the 1/n values derived from Freundlich model in the present investigation were less than …

Phosphorus Removal Using Titanium Dioxide Nanoparticles In Wastewater Treatment, Suyoung Choi Mr.

Theses and Dissertations (Comprehensive)

Due to eutrophication caused by nutrients such as phosphorus (P), local surface water near military garrisons and camps has been deteriorated for several years in the Republic of Korea. Thus, in order to remove excessive P in local fresh water, various size of titanium dioxide (TiO₂) were used.

In the first investigation, TiO₂ mixed bulk powder (particle size > 5µm) showed maximum P removal with pH dependence (higher pH shows lower P removal), that was approximately 27%. To determine adsorption isotherms, Langmuir and Freudlich models were used. The experimental data was better fit by a Langmuir model compared …

Selective Solid Phase Extraction Of Uranium Using An Aminophosphonic Acid Functionalized Composite Material, Ranalda Tsosie

Graduate Student Theses, Dissertations, & Professional Papers

Uranium is an element of interest because it is an abundant source of concentrated energy. In 1948 the US offered money for uranium ore mined in the US, which created a mining boom in the southwest that included the Navajo Reservation. During the late 1960s the demand for uranium decreased and many mining operations shutdown and left behind a legacy of contamination. As a result many Navajo communities have numerous water sources that exceed established maximum contamination levels for uranium and other toxic metals. These contaminations are a direct result of abandoned Cold War uranium mines and mill waste sites …

Density Functional Theory Calculations On Hydrated Dimethylarsinic Acid And Iron Oxide Clusters, Adrian Adamescu

Theses and Dissertations (Comprehensive)

Dimethylarsinic Acid (DMA) or (CH₃)₂AsO₂H is an important organoarsenical compound detected in arsenic speciation studies of environmental samples and synthesized during pyrolysis of oil shale. DMA was used historically as a herbicide on large agricultural fields and can be detected in the leachates of landfills rich in waste containing arsenic such as glass, alloys, and semiconductors, as well as biologically pre-treated municipal solid waste. Under certain soil conditions DMA can become bio-available and has the potential to be recycled to more toxic inorganic forms of arsenic. Bioavailability of DMA is largely controlled by the …