The removal (%) pH The process   TiO2/solar* Fenton/solar** TiO2/Fenton/solar*** TOC 5.5 9 17 25.7 7 15 16 23.2 COD 5.5 6 39 61 7 24 27 38

*Experimental conditions; 1 g/L TiO2 and 180 min (RT). ** Experimental conditions; 1 g/L H2O2, 0.04 g/L Fe+2 and 180 min (RT). *** Experimental conditions; 1 g/L TiO2, 1 g/L H2O2, 0.02 g/L Fe+2 and 180 min (RT).

Table 3: Comparing the three processes for degradation of TOC and COD under pH values ranges of petroleum wastewater (5.5-7).