Thammarat Panyathanmaporn

Synthesis, preparation and catalytic activities of V-doped TiO2 gel coating on porous α-Al2O3 beads

TiO2 and V-doped TiO2 gel were synthesized and coated onto porous α-Al2O3 beads to study the thermal catalytic activities of oxidation reactions. Titanium isopropoxide (Ti(OPr)4) and 1,2-butadiol(Bu(OH)2) were used as starting chemicals for preparation of TiO2 gel without Vdoping. After aging at ambient temperature for one week, a TiO2 gel was obtained. The concentration of Ti(OPr)4 was varied, 0.2, 0.3, 0.7 and 2.4 M was used. For V-doping of the TiO2 gel, 0.05, 0.20 and 0.75 mole% of V was prepared by ultrasonically dissolving vanadium acetylacetone (V(acac)2) in 1,2-butadiol. The solutions were then added to Ti(OPr)4. Finally, the mixed solutions were kept under ambient temperature for one week to form the V-doped TiO2 gel. TiO2 and V-doped TiO2 were calcined at 300, 400, 500, 600, 700, and 800 °C. XRD analysis, SEM and TEM in conjunction with EDS analysis were used to identify the phases present, grain size and morphology. The TiO2 grains have a particle size in the nano-scale range. Doping TiO2 with V could retard growth of the TiO2 particles and affect phase transformation at higher calcination temperatures. Both the TiO2 and V-doped TiO2 gels were prepared and coated onto α-Al2O3 beads to test oxidation reactions in a purpose-designed reactor. The results of the catalytic reactions indicated that V-doped TiO2 had a higher oxidation activity than the undoped TiO2 gel. The content of vanadium was related to the reaction efficiency.

Ag-Doped TiO2 Immobilized on Al2O3 Bead as Oxidation Catalyst

Ag-doped TiO2 catalyst employed as the oxidation catalyst candidate was prepared by two methods, co-precipitation and dip coating method. Co-precipitation method was conducted by adding AgNO3 into the titanium precursor before gelation and then the obtained solution was coated on the alumna beads. Dip coating method was conducted by coating the first layer on alumina beads with titanium precursor followed by coating the second layer with AgNO3. The fired Ag-doped TiO2 coated on alumina beads was used as catalyst for catalytic oxidation of methanol and carbon monoxide by using oxygen as oxidizing agent in a gas-phase reactor. The methods of catalyst preparation were found to affect the catalytic efficiency. Dip coating method showed better oxidation reaction as Ag-doped TiO2 catalysts were well dispersed on the alumina beads.

Adhesion Improving of TiO2-Coated Fabrics

Adhesion between TiO2 coatings and the fabrics was improved by using a silane adhesive agent. To investigate a suitable method of applying adhesive agent, two different coating methods were conducted. The silane was either mixed with Ti precursor for fabric dipping, or coated onto the fabrics before dipping them in a Ti precursor. The effect of Ti precursor, sol and colloid, on coating morphology was also studied. It was found that continuous coating with no cracking was obtained when the fabrics were pre-treated with the silane. The TiO2 coatings had good adhesion, regardless of the method of applying the adhesive agent. Thick, cracked coatings were obtained from Ti colloid precursor while continuous coating was obtained from the Ti sol precursor.

A Textile Waste Water Treatment System Using Photocatalytic Reactor and Catalyst Recycle Unit

A photocatalytic system for wastewater treatment from textile industries was constructed and tested for its efficiency. The system consisted of two units – a photoreactor for dye decomposition and a catalyst recovery unit. The photoreactor was an annular plug flow photoreactor under irradiation of 36 W Toshiba blacklight. The catalyst recovery unit was 42 L of sediment tank for TiO2 catalyst recovery. In our study, a Cibra Cron red R-W 150% (an anionic azo dye) was used to prepare a synthetic textile wastewater. The experimental parameters such as flow rate, pH, dye initial concentration, catalyst loading and setteled time that affected the system performance were investigated. The photodegradation kinetics were found to follow the Langmuire - Hinshelwood model and also depended on the TiO2 concentration and the pH. The optimum condition for photocatalytic decomposition was at pH 3 and at 1 g/L of TiO2 catalyst loading. The reaction rate constant, k and the adsorption constant, K for the scale-up photoreactor were 3.345 mg/L-min and 0.0204 L/mg, respectively. For the catalyst recycle unit, the overflow and underflow concentration of the TiO2 catalyst were 2.00 and 0.002 mg/L, respectively, at 100 ml/min of inlet flow rate, 50 ml/min of overflow and 50 ml/min of underflow.