**4.2 Effect of concentration of reaction media at 50°C**

Hydrothermal reaction was carried out using 4–50% caustic solution for polyester tokens. The reaction was carried out at temperature of 50°C, under dynamic conditions, using un-irradiated polyester tokens. The observations at 50°C temperature are shown in **Figure 6**. There is an improvement in degree of depolyemrisation of more than 100% with 50% and 10% alkali concentrations. The DODP of up to 100% could be observed with 10% and 50% alkali concentrations. It is planned to carry out further studies to explore the possibility of recycling of spent polymers through selective chemical treatments.

#### **4.3 Effect of concentration of reaction media at 75°C**

Hydrothermal oxidation by alkaline hydrolysis is heterogeneous two phase reaction. Hydrothermal reaction was carried out using 4–50% caustic solution for polyester tokens. The reaction was carried out at temperature of 75°C under dynamic conditions using un irradiated polyester tokens. The results are shown in **Figure 7**. There is an improvement in degree of depolymerisation of more than 100% with 50% and 10% concentrations. The DODP of up to 100% could be observed with 10% and 50% concentraions in less than 4 hours.

*Desalination Membrane Management DOI: http://dx.doi.org/10.5772/intechopen.99723*

**Figure 6.** *Effect of concentration of reaction media on HTP-2 process technique at 50 deg. C.*

**Figure 7.** *Effect of concentration of reaction media on HTP-2 process technique at 75 deg. C.*

#### **4.4 Effect of irradiation on HTP-2 process technique**

The purpose of this investigation is to see effect of irradiation on hydrothermal oxidation by various process techniques. Hydrothermal reaction was carried out using 4% caustic solution for polyester tokens. The reaction was carried out at temperature of 50°C under dynamic conditions, using both un-irradiated and irradiated polyester tokens. The results are shown in **Figure 8**. There is an improvement in degree of depolymerisation of more than 100% with irradiation. The DODP of up to 80% could be observed with 4% concentrations. It is planned to carry out further studies to explore the possibility of recycling of spent polymers through selective chemical and non chemical treatments.

**Figure 8.** *Effect of radiation on HTP-2 process technique.*


**Table 2.** *Variation of COD values during hydrothermal process technique w.r.t polyester.*
