Iranian Journal of

---

Backgrounds and Objectives: Phenol and phenolic compounds are widely used in industry and daily liFe, and are of high interest due to stability in the environment, dissolution ability in water and health problems. In this regard, phenol removal from water is of high importance. The purpose of this study was to investigate the efficiency of photodegradation process for removal of phenol from aqueous system by use of Fe-doped TiO2 nanoparticles prepared by sol-gel method.
Materials and Methods: Phenol concentrations of 5, 10, 50 and 100 mg/L were prepared and exposed to UV and Fe-doped TiO2, separately and simultaneously. Also the effect of initial phenol concentration, Fe-doped TiO2 loading and pH were studied. Various doses of photocatalist investigated for Fe- doped TiO2 were 0.25, 0.5 and 1 g/L. pH was studied at three ranges, acidic (pH=3), neutral (pH=7) and alkaline (pH=11).
Results: Maximum degradation was obtained at acidic pH, 0.5 g/L of Fe-doped TiO2 for all of phenol concentrations. With increasing initial concentration of phenol, photocatalytic degradation decreased. In comparison with Fe-doped TiO2/UV process, efficiency of UV radiation alone was low in phenol degradation (% 64.5 at 100 mg/l of phenol concentration). Also the amount of phenol adsorbed on the Fe-doped TiO2 was negligible at dark conditions.
Conclusion: Results of this study showed that Fe(III)- doped TiO2 nanoparticles had an important effect on photocatalytic degradation of high initial phenol concentration when Fe(III)-doped TiO2/ UV process applied.

---

Background and Objectives: Pollution of water resources to nitrate is an environmental problem in many parts of the world. This problem possibly causes diseases such as methemoglobinemia, lymphatic system cancer and Leukemia. Hence, nitrate control and removal from water resources is necessary. Considering that application of nanomaterials in treatment of environmental pollutants has become an interesting method, in this research use of Ag-doped TiO₂ nanoparticles synthesized through photodeposition produced under UV irradiation was studied for removal of nitrate from aqueous solutions.
Materials and Methods: Three nitrate concentrations of 20, 50, and 100 mg/L were considered. In order to determine the effect of Ag-doped TiO₂ nanoparticles on  nitrate removal, dosages of  0.1, 0.4, 0.8 and 1.2 g/L nanoparticles were used pH range of 5-9 was also considered. The effect of Ag-doped TiO₂ nanoparticles both in darkness and under UV irradiation was studied. Moreover, the presence of chloride and sulfate anions on the system removal efficiency was investigated.
Results: The optimum performance of nitrate removal (95.5%) was obtained using nitrate concentration of 100 mg/L, in acidic pH and 0.8 g/L Ag-TiO₂. Increase of nanoparticle dosage up to 0.8 g/L, increased the removal efficiency, but for 1.2 g/L dosage of nanoparticles, the removal efficiency decreased. Maximum reduction performance without nanoparticles, under UV irradiation and under darkness conditions were 32% and 23.3% , respectively. In addition, we found that presence of sulfate and chloride anions in aqueous solution reduced efficiency of nitrate removal.
Conclusion: Results of this study showed that Ag-doped TiO₂ nanoparticles may be efficiently used for nitrate removal from aqueous solutions.

---

Background and Objective: Radon is highly regarded because of its impacts on public health. Northern regions of Iran have a high potential for radon emissions. This research aimed to measure residential radon concentrations in Tarom country- Zanjan and to compare the results with international standards and acceptable values.

Materials and Methods: Passive diffusive samplers, Solid State Nuclear Track Detector (SSNTD), with the ability to determine background and longtime concentration, were selected for this study. A total of 30 detectors were located based on a pre-identified network in the residential buildings of Chavarzaq, Ab Bar and Gilvan for a period of three months. Then, detectors were sent to a laboratory for counting the traces.

Results: Based on the results, average radon concentrations in Chavarzaq, Ab Bar and Gilvan were 220.51, 95.25 and 119.84 Bq/m³, respectively. The average radon concentration in Tarom was about 130.57 Bq/m³. There was no meaningful relationship between radon concentration with the age of buildings or number of occupants. In comparison of the results with USEPA standards it was observed that among total samples just one of them was in the range of target level, and 15 detectors were in the range of target to action levels and the remaining samples showed high level of radon requiring corrective measures. In addition, 12 detectors showed values less than the reference level of WHO and the remaining detectors had higher values than WHO level.

Conclusion: Based on results of this research, soil analysis before construction, application of building materials resistant to leakage and regular monitoring of radon levels in region were suggested.