| Abstract |
Nitrate is one of the major pollutants in New Zealand waterways. Nano-zero valent iron (nZVI) has previously been used to reduce nitrate to ammonia with some success. However, as nZVI is inherently magnetic, these particles tend to agglomerate. Agglomerated nanoparticles lose some of their effectiveness due to the reduction of their surface area. Agglomeration also impedes the mobility of the particles within soils. Paradoxically, as nano particles are highly reactive, it is imperative to ensure that the particles are well contained and not loose in the environment. One method to circumvent the shortcomings of nanoparticles for environmental application is to use an inert support material. Ideally, nano particles adsorb evenly on the surface of the support, hence maintaining surface area and reactivity, while reducing the agglomeration of the material. Microsilica 600, a silica fume from the Rotorua geothermal area (Golden Bay Cement) has been used as an additive for cementitious material due to its pozzolanic nature. Raw Microsilica 600 was not an effective support for nZVI. A series of treatments were developed, and these enabled the nZVI particles to be adsorbed successfully on the Microsilica surface. The reactivity of these hybrid materials were tested with 10 mg dm-3 nitrate (as N) on lab scale experiments, and they were successful in reducing 90% of the nitrate into ammonia within 60 minutes. The success of the reduction depends on both the evenness of the adsorption of nZVI and the presence of FeOOH coating on the silica surface. Furthermore, the supported nZVI are able to travel deeper into the soil, making the supported nZVI more effective as a nitrate reductant |