**3. Results and discussion**

56 Food Industrial Processes – Methods and Equipment

The quantification of the pesticides and DNP in UV irradiated solution was performed in the next procedure. About 2 g of NaCl was added in 40 ml of UV irradiated solution and each pesticide or DNP was extracted with 4 ml of dichloromethane. The dichloromethane layer was separated from aqueous layer, dehydrated with anhydrous Na2SO4 and analyzed by the GC/MS method (Nakano et al., 2004; Yamaguchi et al., 1997). The GC/MS conditions were shown in Table 3. Each calibration curve showed good linearity in the quantification

pH, suspended solid matter (SS), BOD, KMnO4 consumption, total nitrogen (T-N), total phosphorus (T-P) and electric conductivity (EC) were measured by the method of Japanese

Column DB-5MS (5%Diphenyl 95%dimethyl polysiloxane)

Column temperature 60 oC (1 min)-30 oC min-1-130 oC-5 oC min-1

**2.5 The photodecomposition capability experiments of alumina carrier-TiO2** 

Item Concentration pH 7.6 SS (mg l-1) 6 BOD (mg l-1) 3.5 KMnO4 consumption (mg l-1) 5.8 T-N (mg l-1) 1.52 T-P (mg l-1) 0.08 EC (μS cm-1) 264

Table 4. Quality of the river water used for this experiment

Each alumina or silica gel carrier-TiO2 photocatalyst was packed in the photoreactor. The water samples for DNP and pesticides experiments were prepared by adding 3 ml of each 1,000 mg l-1 DNP or pesticide acetone solution in 3 l of purified water (for the photodecomposition capability experiment of photocatalyst) or the river water (Table 4) (for the photodecomposition experiment of pesticide). The water sample was vigorously shaken for 30 min using a separatory funnel and placed in 5 l glass bottle. The water sample was firstly circulated for 30 min at l min-1 of flow rate by stirring and the system was allowed to reach equilibrium. Then the mercury lamp was switched on. The UV irradiated solution was periodically withdrawn during irradiation and DNP or each pesticide was quantified by the GC/MS method. The photodecomposition experiments of pesticides without a

**photocatalysts and photodecomposition experiments of pesticides** 

0.25 mm x 30 m x 0.25 μm


Industrial Standard K0102 (Japan Industrial Standards Committee, 1995).

**2.4 Analyses of pesticides, DNP and other items** 

range. Their recoveries by the method were over 85%.

Injector temperature 250 oC

Transfer line temperature 260 oC Mode EI

Table 3. GC/MS conditions

photocatalyst were also performed.

Carrier gas He 1.5 ml min-1

### **3.1 Comparison of the photodecomposition capability of alumina carrier-TiO2 photocatalysts**

Figure 5 shows the photodecomposition rates of DNP using the alumina and silica gel carrier-TiO2 photocatalysts. DNP was decreased exponentially with reaction time (t) and the rate of DNP disappearance was nearly represented by a first-order process. The values of pseudo-first-order rate constant (k: C=C0e-kt) of NK124, NKHO24 and silica gel carrier-TiO2 photocatalysts determined from the plot of data points (C/C0 vs. t) were 0.027, 0.016 and 0.030 min-1, respectively. The rate constant of NK124 carrier-TiO2 photocatalyst was near that of silica gel-TiO2 photocatalyst.The micropore volume of NK124 is lager than that of NKHO24 but its relative surface area is smaller than that of NKHO24. The supporting ratio of NK124 was higher than that of NKHO24. It was supposed that the deference of DNP photodecomposition rate was caused by the deference of supporting ratio. Then, the photodecomposition experiments of the pesticides were performed using a NK124 carrier-TiO2 photocatalyst.

Fig. 5. Photodecomposition rates of DNP
