Iranian Journal of

Background and Objectives: Toxicity assessment of material related to nanotechnology is necessary before excess development of this industry. On the other hand, specific characteristic of nanomaterials can be used in disinfection of other material. In this study toxicity and antibacterial properties of nano-TiO₂ and nano-CuO were investigated with four bacterial species in solid media.

Material and Methods: Stock suspension of nanoparticles (10g-TSS/L) was diluted using Muller Hinton Agar to achieve 5-6000mg-TSS/L concentration. We prepared three Petri dishes for each concentration and refined bacteria were cultured on these Petri dishes. After culturing of these bacteria on the media containing nanoparticles, growth inhibition was determined. According to this data, 50% growth inhibition (EC₅₀), no observed effect concentration (NOEC) and 100% growth inhibition were determined.

Results: Our results showed that toxicity of TiO₂ is more than CuO in solid media. In this regard, nano-TiO₂ EC₅₀ for Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa was calculated 181, 571, 93 and 933mg-TSS/L respectively. These figures for nano-TiO₂ were 2550, 1609, 946, and 1231mg-TSS/L respectively.

Conclusion: This study showed that compared with other bacteria studied, E. aureus due to high sensitivity and E. coli due to high resistance to both TiO₂ and CuO nanoparticles are more proper as bioindicator in toxicity test and antibacterial test respectively.

Background and Objectives: Phenol is one of priority pollutants produced through leather, paint, resin, and pharmaceutical industries and it can contaminate groundwater after entering to the environment. Hence, it is necessary to use a suitable method for its removal. The aim of this study was synthesize and efficiency evaluation of magnetic nanocomposite of activated carbon powder-zero valent iron/silver (PAC-Fe^o/Ag) in the removal of phenol from aqueous solution. Material & Methods: Reduction method was used for converting bivalent iron to zero valent iron and co-precipitation method for depositing of iron on activated carbon. For coating silver on nano zero valent iron, rapid mixing at high temperature was used. The adsorbent was characterized using SEM, TEM, and XRD techniques. Then, the impact of pH, contact time, agitation speed, temperature, adsorbent, and initial phenol concentration were evaluated and optimized by one factor at the time method. Reaction kinetics and isotherms were also determined. Results: It was found that PAC-Fe^o/Ag has cubic and intertwined structure and has a diameter in the range from 40 to 100 nm. The optimum conditions for phenol removal by PAC-Fe^o/Ag were as pH=3, 90 min contact time, 200 rpm agitating speed and adsorbent concentration equal to 1 g/l. Isotherm and kinetic equations showed that the experimental data of phenol adsorption onto PAC-Fe^o/Ag are correlated to the Langmuir (R²>0.969) and pseudo-second order (R²<0.965) models, respectively. Conclusion: Under optimum conditions, modified adsorbent by zero valent iron and silver with maximum efficiency of 97% has quickly and effectively ability in removal of phenol and it can be easily separated from the solution sample by magnet because of its magnetic properties.