Metal-containing hybrid materials for water remediation from trace heavy metals

Final Report Summary - HY-REM (Metal-containing hybrid materials for water remediation from trace heavy metals)

The aim of the HY-REM project was to produce hybrid composite materials and use these as the basis of prototype, low-cost and effective water clean-up devices.

In the early phases of the project, a range of prototypes of hybrid composite materials including silica with grafted silicon hydride groups and functionalised Polyhedral oligomeric silsesquioxanes (POSS) were produced. Physicochemical characteristics and adsorptive properties of the materials produced were assessed. Several approaches of functionalisation of silica were tested using post-synthesis modification and one-pot synthesis (self-assembly of different organosilanes). POSS production was optimised with the aim to obtain a material with good adsorptive properties. The analysis of modified silica and POSS with LTNA has shown that composites have quite narrow pore size distributions. The combination of Fourier transform infrared spectroscopy (FTIR), 1H and 29Si nuclear magnetic resonance (NMR) confirmed a uniform distribution of functionalised groups, which form reactive sites available for interaction with metal ions. Particle size distribution was estimated via transmission electron microscopy (TEM) and scanning electron microscope - energy-dispersive X-ray spectroscopy (SEM-EDX) methods.

The efficiency of Hg removal from water over a wide pH range at a range of concentrations from 0.001 to 1.6 g / l by silica with attached silicon hydride groups has been studied. Hg adsorption onto hydride silica composites was observed to be a fast (within a few minutes) and efficient process, allowing the loading up to 45 mg of Hg per g of silica.

POSS hybrid materials with different functional groups (SiH, SH) were tested for inorganic Hg removal from aqueous solution allowing an increase in loading by almost two times, up to 106 mg of Hg per g of POSS-SiH and 87 mg of Hg per g of POSS-SH, which indicates their potential usefulness as effective materials for Hg decontamination in natural waters and industrial effluents.

Removal of inorganic Hg from water solution using silica with immobilised silver nanoparticles was also shown to be a very rapid process, allowing the removal up to 30 mg of Hg per g of sorbent. The reaction occurs effectively immediately, at room temperature and is accompanied by a change of the colour of the sorbent, which can potentially be used for colorimetric determination of Hg in solution. The present system studied has revealed a remarkable improvement in the adsorption of Hg (II) using a minimal amount of silver nanoparticles at smaller nanodomains, indicating the potential application of size controlled silver nanoparticle-based composite devices in removal of Hg from industrial and other effluents.

The removal of radioactive silver (110 mAg) from aqueous solution on hydride silica, its loading and pH effects under static conditions were studied in collaboration with the National Oceanography Centre, University of Southampton, United Kingdom. It was found that under the experimental conditions studied, 110 mAg was significantly adsorbed onto modified silica as determined by gamma spectrometry. 110 mAg adsorption is a fast and efficient process, leading to the formation of stable silver on silica with no leaching evident during the testing period. The immobilisation of 110 mAg species on the silica surface is determined by the redox properties of silicon hydride groups present, their absence prohibits any decline of radioactivity in the supernatant solution. Ultimately, the results reveal that hydride silica groups on silica show great promise in the stable removal of 110mAg from natural and waste waters. 110 mAg is a key problem contaminant in nuclear industry wastes.

Silica-based composites production has been optimised to obtain a material with good permeability, high accessibility of functional groups and good efficiency for manufacturing filtration devices. Based on market research (task 4), four key target markets were identified: water industry, contaminated land remediation industry, public health / access to clean water agenda for developing countries and the mining industry. It was decided to focus efforts initially on the water industry as this the largest market and provides the broadest range of market opportunities. HY-REM has been designed to provide a low cost, low energy, technology which fits in well with market conditions in terms of the drive towards sustainability and reduction of greenhouse gas emission.

Project website: http://www.brighton.ac.uk/uncos/HY-REM

Final Report Summary - HY-REM (Metal-containing hybrid materials for water remediation from trace heavy metals)

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