Development of Nano-Zero Valent Iron for the Remediation of Contaminated Water

Abstract

Various materials are currently available to remove heavy metals from groundwater such as activated carbons, carbon nano tubes, bentonite and Zero Valent Iron (ZVI). All these materials are capable to transform toxic substances to non toxic and/or to adsorb toxic substances via ionic exchange, ion precipitation and adsorption. Nano-sized Zero Valent Iron (NZVI) is considered as an effective adsorbent and ideal technology for in-situ remediation of heavy metal contaminated groundwater. Therefore, this study was conducted to produce NZVI via chemical reduction process using FeCl2•4H2O titrated with reduction agent of NaBH4. The process is divided into four stages; mixing, separating, washing and drying. The materials produced from these processes are varies in colours, i.e. black, dark brown, brown and light brown. Colour variation observed is due to the intensity of oxidation process of these materials and became the main predicament of this research, especially during drying stage. Samples produced were marked according to their colours. The particle size of selected Zero Valent Iron samples namely ZVI-1b, ZVI-3b and ZVI-4b were determined using Master-sizer instrument. Sample ZVI-3b has a particle size ranging from 0.4 µm – 1000 µm and it is mainly dominated by 50 µm particles. ZVI-4b has the same size range as ZVI-3b but it is dominated mainly by particles of 60 µm. Meanwhile, the particle size for ZVI-1a could not be detected because of much smaller size which is well below the detection range of the size analyser. Another four samples namely ZVI-1a, ZVI-1b, ZVI-2b and ZVI-3b were analysed using Scanning Electron Microscopy (SEM). The results show that ZVI-1a has a platy texture, ZVI-1b has a dendritic texture and ZVI-2b has both platy and dendritic textures. While ZVI-3b shows a botryoidal texture. All results including colour, particle size and SEM images indicate that there is a potential of producing Nano-Zero Valent Iron especially ZVI-1b that has properties (size and micro texture) similar to Nano-Zero Valent Iron. Batch tests further confirmed the capability of ZVI-1b to effectively remove Cu from contaminated solution for up to 97 %.