269733 Application of Noble Catalytic System for Nitrate Removal in Wastewater

Wednesday, October 31, 2012
Hall B (Convention Center )
Min-Sung Kim1, Sang-Ho Chung2 and Kwan-Young Lee1,3, (1)Chemical and Biological Engineering, Korea university, Seoul, South Korea, (2)Chemical and Biological Engineering, Korea University, Seoul, South Korea, (3)Chemical & Biological Engineering, Korea University, Seoul, South Korea

Application of Noble Catalytic System for Nitrate Removal in Wastewater

 

Min-Sung Kima, Sang-Ho Chunga and Kwan-Young Leea,b,*

 

a Department of Chemical and Biological Engineering, Korea University, 5-1, Anam-dong, Sungbuk-gu, Seoul, 136-701, Republic of Korea

b Green School, Korea University, 5-1, Anam-dong, Sungbuk-gu, Seoul, 136-701, Republic of Korea

 

 

Nitrates (NO3-) have no detectable color and taste materials, and have been increasing everywhere in the world because of overusing of man-made fertilizers. Nitrate can occur fatal disease to infants under 6 months of age, called blue baby syndrome. Also high concentration of nitrate may cause some cancers and teratogenic effects. Biological and physicochemical treatments such as sedimentation, filtration, chlorination or pH adjustment, ion exchange and reverse osmosis, can effectively remove nitrates but have several economical disadvantages. Catalytic nitrate removal has been promising method for the reduction of nitrate in water. The method is based on the catalytic hydrogenation of nitrate to nitrogen. The reaction scheme is shown in Fig. 1. Several combinations between a noble and a non-noble metal catalyst have been studied for reduction of nitrate in water. This study evaluated the effectiveness of the catalysts with specific combination, characterized features of the catalysts. 

 

Fig. 1. Reaction scheme of the catalytic nitrate hydrogenation.

 

 

BET isotherms showed that silaca gel support had mesostructure with type ³. Measured BET surface area are 465 m2/g, while pore sizes are 7.34 nm.

 

Fig. 2. (Left) Nitrogen adsorption-desorption isotherms of commercial silica-gel; (Right) Pore size distribution of commercial silica-gel.

 

 

When nitrate is reduced to nitrogen, hydroxide ions are formed, which resulted in increasing pH value of the reactant. Therefore, many studies reported that increasing pH value of the solution was unfavorable to the nitrate removal and nitrogen formation. As can be seen in Fig. 3, the reduction of nitrates is quite different depending on reactant pH. Among the catalysts, Rh-Cu presented relatively maintained nitrate conversion.

 

 

Fig. 3. Nitrate conversion in dependence of the pH value for the hydrogenation of nitrate to nitrogen. Initial concentration of nitrate(C(NO3-)i): 2 mM; catalyst: 0.15 g; amount of gaseous hydrogen: 30 ml/min; HCl: 0.05 M; reaction pressure: 1 atm; reaction temperature: 25C; Reaction time: 5 h.

 

Fig. 4 represented nitrate conversion and nitrogen selectivity of prepared catalysts. The order of activity of the catalysts: Rh-Cu > Pd-Cu > Pt-Cu, with nitrate conversion values of 65%, 47.5% and 68%, respectively, while Pt-Cu had the highest nitrogen selectivity.

 

 

Fig. 4. Nitrate conversion and selectivity to nitrogen of the prepared catalysts. Initial concentration of nitrate(C(NO3-)i): 2 mM; catalyst: 0.15 g; amount of gaseous hydrogen: 30 ml/min; HCl: 0.05 M; reaction pressure: 1 atm; reaction temperature: 25C; Reaction time: 5 h.

 

Consequently, the performance of catalytic nitrate reduction was different according to reactant pH and supported metal. Furthermore, Rh-Cu catalysts had higher activity than other catalysts, retained nitrate conversion notwithstanding pH difference.


Extended Abstract: File Not Uploaded