Abstract of PhD Thesis

Development of Chemically Engineered Nanoporous Materials for Water Pollution Remediation

Colm McManamon, University College Cork, 2015

Anthropogenic sources of phosphate (deriving mostly from the use of fertilizer, failing septic systems, detergents and even water treatment plants) can lead to eutrophication of both lake and river water. High phosphate levels therefore represent a significant environmental problem in both urban and rural areas. Phosphorous related pollution issues may have particular relevance in light of recent storms and flood activity in Ireland as a primary source of fresh water phosphorous contamination is associated with storm water run-off. However, remediation of phosphate is challenging and no clear method exists. Biological, electrochemical, chemical and adsorbent technologies have all been proposed. This work focuses on developing advanced adsorbents as a platform for developing a technology for phosphorous pollution treatment.

The aim of this thesis is to synthesise and develop an emerging type of novel mesoporous (nanoporous) materials for environmental use. The Cork based laboratories have pioneered the synthesis and characterisation of these important materials.   Briefly, a silicon source is combined with a surfactant to yield an ordered mesoporous silica (OMS).  These OMS materials can be doped or functionalised with metals or organic compounds to provide highly efficient and specific adsorbents.  OMS doped with titania and iron displayed great ability to adsorb large quantities of orthophosphate as well being able to achieve highly efficient results at very low concentrations of the dopant.  In our work pore sizes were tailored to find the most efficient adsorption materials in terms of application in water treatment plants. Maximum adsorption of orthophosphate was 4 and 4.5 mg l-1 for Ti and Fe, respectively and these values represent some of the highest adsorbent efficiencies recorded.  The same materials could also be chemically functionalized to act as heavy metal sorbents.  An issue barely addressed in the scientific literature is the practical use of these materials and their cost-effectiveness.  Here, we made particular effort in this regard and the regeneration of the OMS materials was achieved using either acidic or basic solutions and the damage to the framework was minimal allowing for repeated use.

Our work was further extended by developing strategies for organic contamination treatments.  We evolved a number of photocatalytic systems for organic degradation using Li2TiO3 nanoparticles, enhancing their activity by doping them with metals and non-metals. It was concluded that S and ZrO2 dopants were the most efficient materials for the photocatalytic degradation of organic compounds.  As a demonstrator we used microporous TiO2 nanoparticles doped with different amounts of ZrO2 as catalysts for the decomposition of phenol, an extremely toxic organic compound. This method displayed very high degradation rates of phenol and out-performed the commercial catalyst P25.  Very high rates of degradation were also observed upon regeneration showing little adverse effect after 5th use.

Although these solutions remain to be scaled to industrial production and application, we are looking to work with a European company to licence the technology.  The work produced seven publications in leading scientific journals and the student in now employed within a university spin-off company for translating scientific research into commercial exploitation.