Limitation of Ti02 Application 27 2.7 Synthesis of Immobilized Ti02 Photocatalyst 2.8 Synthesis of Ti02 Microsphere Photocatalyst 2.9 Synthesis of Nano-structured Ti02 Microsphere 2.10 Sol-gel Method 2.1 1 Parameters Involved in Sol-gel Processing 34 2.11.1 Choice of Precursors 3 5 2.11.2 Type of Solvent and Its Mole Ratio to Precursors 36 2.11.3 Calcination Temperature 37 2.11.4 pH 39 2.12 Humic Substances 2.13 Humic Acids in Water Treatment 2.14 Removal of Humic Acids in Water 2.14.1 Coagulation Process 2.14.2 Membrane Filtration 4 5 2.14.3 Advanced Oxidation Process-Ti02 Photocatalysis 2.14.4 Adsorption of Humic Acid on Ti02 2.15 Role of Adsorption in Photocatalytic Oxidation Process