Nanoparticulate materials for environmental remediation : adsorption vs. advanced oxidation techniques

Student thesis: Doctoral Thesis

Abstract

The research presented in this thesis examines the performance of silica-based materials as adsorbents in the remediation of air and water environments alongside conventionally used sorbents. In addition, photocatalytic oxidation (PCO) is investigated as an alternative remediation technique.The use of mesoporous silica materials, MCM-41 and SBA-15, as sorbents for the removal of volatile organic compounds (VOCs) from indoor air was assessed. SBA-15 was found to possess the best dynamic adsorption capacity; trapping 12.5 ng cm-3 of toluene and was shown to perform better as a scavenger sorbent than the commercially available material, Tenax TA.A mesoporous titanium dioxide (TiO2) photocatalyst was prepared via a surfactant templated, sol-gel synthesis approach. Optimum photocatalytic activity for the degradation of VOCs required five coatings of TiO2 film on glass bead support material. High photocatalytic activity and long-term performance were demonstrated with respect to the degradation of toluene, ethylbenzene and cumene (96 - 100 %). Reaction intermediates and a possible degradation mechanism were successfully identified. Regeneration proved to be a simple process, achieved by cooling down the system.The aqueous adsorption of pharmaceuticals or nitrobenzene onto powdered activated carbon (PAC) and silica materials; as-synthesised (As-syn) and calcined (Calc) MCM-41, bioinspired silica (Bio-Si) and iron incorporated Bio-Si (Fe Bio-Si) was assessed. The four target pharmaceuticals in the multi-analyte solution were acetaminophen, caffeine, sulfamethoxazole and carbamazepine. Bio-Si and Fe Bio-Si displayed the lowest adsorption capacities, <0.25 mg g-1, for each pharmaceutical target. The maximum adsorption capacities of PAC and As-syn MCM-41, obtained from the Freundlich model, were 97 and 6 mg g-1, respectively. Nitrobenzene adsorption followed the general pattern: PAC > Calc MCM-41> As-syn MCM-41 > As-syn Bio-Si and Fe Bio-Si > Calc Bio-Si and Fe Bio-Si. Both investigations revealed commercially available PAC to be the dominant sorbent in aqueous adsorption.Fe Bio-Si, applied as a heterogeneous Fenton catalyst, was shown to be highly effective for the degradation of nitrobenzene exhibiting long-term catalytic activity ~ 95 % and 85 % degradation at pH 3 and 7 respectively, with no loss in performance after 15 successive recycle runs. Furthermore, the catalyst was shown to successfully mineralise pharmaceutical targets at pH 3, reaching 100 % degradation for all compounds after the initial cycle.Finally, the process of visible-light induced photocatalytic oxidation, using a Fe-TiO2 thin film as a photocatalyst, displayed potential for the degradation of nitrobenzene in aqueous solutions, achieving 49.1 and 54.9 % degradation for 20 and 50 % Fe-TiO2. Where the mesoporous silica materials failed, in large, to compete with commercially available sorbents, the developed PCO systems, for both indoor air and water treatment, excelled and proved to be very simple yet highly effective techniques that could be easily applied industrially for the efficient degradation of organic pollutants.
Date of Award1 Oct 2015
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorLorraine Gibson (Supervisor) & Christine Davidson (Supervisor)

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