Printing and dyeing wastewater is known for its complex composition, high volume, intense coloration, and elevated chemical oxygen demand (COD). It often contains rayon saponification products and a variety of new additives, which introduce numerous refractory organic compounds into the water. These compounds make the wastewater resistant to both oxidation and biological degradation, significantly increasing the difficulty of treatment. Removing high color intensity and high COD values from printing and dyeing wastewater remains two major challenges in this field [1]. Currently, most domestic and international approaches to treating this type of wastewater rely on biochemical methods with chemical support. However, these techniques suffer from high operational costs, limited effectiveness, and difficulties in removing COD and color efficiently. Semiconductor photocatalytic oxidation technology has emerged as one of the most promising new methods for pollutant removal. This method offers advantages such as low energy consumption, ease of operation, and no secondary pollution. Among various photocatalysts, nano-TiOâ‚‚ (titanium dioxide) is the most widely used. Its application in the treatment of printing and dyeing wastewater holds significant theoretical and practical value [2-3]. Most studies on photocatalytic oxidation focus on small organic molecules, while the degradation of macromolecular organic compounds using nano-TiOâ‚‚ has not been well documented. In this thesis, we conducted photocatalytic degradation experiments on real printing and dyeing wastewater using quartz sand coated with a nano-TiOâ‚‚ film, and analyzed the reaction kinetics.
**Experimental Procedure** **1.1 Main Testing Equipment and Reagents** Medical ultraviolet lamp (30W); Homemade photocatalytic reactor: a rectangular groove made from mirror glass, measuring 50mm × 15mm × 5mm; quartz sand (particle size 7–10 mm); ammonium fluorotitanate; HCl, anhydrous ethanol, etc., all of analytical grade. **1.2 Experiment** **1.2.1 Preparation of Nano-TiO₂ Film-Coated Quartz Sand** In this experiment, a nano-TiO₂ film-coated quartz sand was prepared using the liquid deposition method. Ammonium fluorotitanate and boric acid were used as precursors and dissolved separately, then mixed uniformly to form an aqueous solution with concentrations of C(NH₄)₂Ti₂F₆ = 0.1 mol/L and CH₃BO₃ = 0.3 mol/L. 100 g of pre-washed quartz sand (washed with deionized water, HCl, NaOH, and absolute ethanol) was placed in a beaker. Then, 250 mL of the ammonium fluorotitanate-boric acid mixture was added. The beaker was covered with a watch glass and kept at a constant temperature. The solution was hydrothermally deposited at 40°C for 50 hours. Afterward, the quartz sand coated with TiO₂ was removed, washed, air-dried, and then heat-treated in a muffle furnace at 450°C for 30 minutes. The sample was stored away from light for further use.
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Hanger Bolts have threaded areas at both ends, a lag screw thread at one end and machine screw thread on the other. They are designed for insertion into a pre-drilled hole and are ideal for overhead application, usually in a wall or ceiling. Plain finish, or bare metal, may or may not have a coating of light oil to resist corrosion. Plain finish, or bare metal, may or may not have a coating of light oil to resist corrosion.
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