Date of Award
Doctor of Philosophy
Jorge L. Gardea-Torresdey
The accumulation of engineered nanomaterials (ENMs) in environmental sectors will continue to increase as more applications are discovered for their unique properties and characteristics. Additionally, the presence of nanomaterials in the environment becomes exacerbated as more consumer products containing nanoparticles are approved for use. It is debated whether the toxic effects of nanoparticles stem from the particles themselves, ionic species, or formation of secondary particles. Therefore, understanding the behavior of nanoparticles in the environment becomes key to discerning the toxicological effects of nanoparticles. Many advancements have been made with ICP-MS to understand the behavior of nanoparticles in the environmental systems, as well as improve trace detection of nanomaterials in complex matrices. The development of single particle inductively coupled mass spectroscopy (spICP-MS) has been imperative to studying nanoparticle stability and accumulation in environmental and biological matrices.
Carbon black (CB) is an ENM with numerous industrial applications and high potential for integration into nano-enabled water treatment devices. However, few analytical techniques are capable of measuring CB in water at environmentally relevant concentrations. Therefore, we intended to establish a quantification method for CB with lower detection limits through utilization of trace metal impurities as analytical tracers. The lanthanum impurity was chosen as a tracer for spICP-MS analysis based on measured concentrations, low detection limits, and lack of polyatomic interferences. CB stability in water and adhesion to the spICP-MS introduction system presented a challenge that was mitigated by the addition of a nonionic surfactant to the matrix.
Following optimization, the limit of detection (64 μg/L) and quantification (122 μg/L) for Monarch 1000 CB demonstrated the applicability of this approach for samples expected to contain trace amounts of CB. When compared against gravimetric analysis and UV-visible absorption spectroscopy, spICP-MS quantification exhibited similar sensitivity but with the ability to detect concentrations an order of magnitude lower. Additionally, a more complex synthetic matrix representative of drinking water caused no appreciable impact to CB quantification. In comparison to existing quantification techniques, this method has achieved competitive sensitivity, a wide working range for quantification, and high selectivity for tracing possible release of CB materials with known metal contents.
As nitrate pollution in groundwater continues to escalate, more is being discovered about the detrimental environmental implications associated with this pollutant. Thus, there is a great necessity for the effective and sustainable remediation of nitrate from water. The electrocatalytic reduction of nitrate (ERN) has been identified as a promising technology with respect to selective product formation (N2(g) and NH3/NH4+), adaptable instrument configurations, and compatibility with renewable energy sources. Traditional catalysts for ERN applications include expensive platinum group metals, which makes the widespread utilization of this technology economically unfavorable. Alternatively, research within the last five years has shown cost-effective catalytic materials such as bimetallic systems, graphitic composites, metal oxides, and metal sulfides exhibiting substantial activity/selectivity for ERN applications. Herein, we are developing a bioinspired electrocatalyst, molybdenum disulfide supported on graphene oxide (MoS2/GO), for selective conversion of nitrate pollution into ammonia for resource recovery applications. Utilizing a Cu foam cathode, decorated with MoS2/GO electrocatalytic ink, has culminated to a low cost and effective 3D design with 93.7% selectivity towards NH3/NH4+. Following system optimization this cathodic design has a high potential for implementation as a resource recovery technology for nitrate pollution.
Received from ProQuest
Kenneth Ray Flores
Flores, Kenneth Ray, "Achieving Safe Use Of Advanced Materials In Drinking Water Through Novel Nano Analytics And Enabling Electrification Using Green Catalyst" (2022). Open Access Theses & Dissertations. 3672.