Investigation of Performance of hybrid nanoparticles Tio2/Sio2 in removing of Mercury from industrial waste water

Mercury is a toxic compound. Biological accumulation of mercury especially in aquatic organisms has brought about many health problems. Various methods have been used to remove heavy metals from industrial wastewater. Adsorption is one of the chemical and physical techniques. This method is useful due to high efficiency, easy usage and availability of its different types. This study was performed to evaluate removal efficiency of TiO2/SiO2 hybrid nanoparticle so as to remove mercury from industrial waste. This study is experimental and was conducted on synthetic and real samples of Binalood paint factory wastewater from October to February 2012. The chemical quality of raw wastewater was determined and synthetic solutions were prepared. Then the effect of pH (3, 5, 7 and 9), the amount of adsorbent (0.25, 0.5, 0.75 and 1 g/L), contact times (30, 60, 90, 120 minutes) and different concentrations of Hg (20, 30, 50, 70 and 90 mg/L) on removal efficiency were studied and optimal conditions were determined for each parameter. The same experiments were performed on real wastewater samples. Absorption kinetics and equilibrium isotherms were investigated to better understand the absorption processes. SPSS software version 16 was applied and regression test as well as pearson coefficients were used for data analysis. The maximum percent of mercury removal was observed at pH=5, absorbent amount of 0.5 g/L and retention time of 30 minutes. Removal efficiency of synthetic and real solutions were 99.86% and 95.56%, respectively.It was found that mercury concentration of 50 mg/L causes the maximum removal percentage (99.86%).The results indicated that mercury adsorption follows Freundlich isotherm with a correlation coefficient of r2 =. 56 and the first type synthetic reaction of r2=0.63. Due to high percentage of mercury removal at optimal conditions by hybrid nanoparticles, this method can be regarded as one of the effective ways to remove mercury compared with other methods.