Waste Derived Functional Materials for Removal of Pollutants and Hydrogen Production

Climate change has put a lot of stress on researchers to address the concerning issues of environment including pollution and energy. Environmental pollution has severely negative impacts on humans and aquatic ecosystems causing several diseases. Whereas burning of fossils to generate energy contributes to CO2 generation, in this work we have tried to utilise an organic waste to value added products that can be used to treat water or soil containing hazardous, toxic and life threating pollutants and to produce H2. In first phase of the work, we converted a hazardous Olive waste to hydrochar using hydrothermal. We optimised the functional groups on the surface by varying parameters (temperature, time and biomass/water ratio). The best hydrochar was selected to remove hazardous dyes from water simultaneously. The developed hydrochar successfully removed different nature of competitive dyes from water due to 2-fold increase in oxygenated functional groups as compared to Olive waste. The results suggested a porous carbon framework with good stability. Dye removal results showed a chemisorption mechanism supported ex-situ characterisation and kinetics. In the next step of work, the upgradation of hydrochar was performed for similar purpose. However, this time it was optimised to achieve a carbon encapsulated iron oxide with the highest magnetic properties for easy separation. The developed material showed core-shell structure with iron in core and carbon in shell. The structured helped to speed up the adsorption and removed successfully cationic and anionic dyes from water. Additionally in this work, Fenton degradation to investigate catalytic performance was also investigated. The results showed complete degradation of dyes and ex-situ analysis showed no leaching on iron even after degradation process due to core-shell structure. Further, the magnetic properties enabled to use it in multiple removal cycles with around 90% removal capacity. In the next phase, functional hydrochar and three carbon encapsulated iron oxide (with different carbon content) were investigated for Arsenic immobilisation in a mine soil contaminated with Arsenic. The results showed that all the materials were effective in immobilising Arsenic from soil due to presences of oxygenated functional groups. However, carbon encapsulated iron oxide outperformed the hydrochar due to presence of iron which binds with Arsenic. The results also showed around 50% decrease in hazard quotient proving hypothesis that carbon-based materials will be effective in immobilising Arsenic. Next project focused on the MP removal. However aforementioned materials were not enough functionality to remove MP. MOF had to introduce to upgrade material properties and to achieve a hetero nano pillared structure derived from carbon encapsulated iron oxide. This magnetic 2D materials completely removed MP from water in an hour. It was able to remove MP in presence of a dye as well. The developed structure was investigated through different surface, elemental, and structural techniques. Ex-situ analysis was also perform showing chemisorption as the main mechanism supported by the kinetics data. In the final phase of the work, we aim to use our material for utilisation of wastewater for hydrogen production. However, first we re-engineered our material to be able to adsorb most of the metals and fluorides from wastewater. The metals and fluoride adsorbed was then transformed and converted into several compounds during electrochemical wastewater splitting, including iron fluoride, graphitic fluoride, Ni carbide, Fe carbide, and CrMoO etc. These compounds contributed to in-situ modification of our material as the catalyst during electrochemical work and was confirmed by several structural and surface techniques. Utilising wastewater resources for water splitting showed exceptionally low overpotential, especially for hydrogen production with exceptional stability for 18 days in alkaline media. The results showed that these materials have to potential to use at large scale for commercial purposes with few modifications.