Photocatalytic Treatment of An Actual Confectionery Wastewater Using Ag/TiO2/Fe2O3: Optimization of Photocatalytic Reactions Using Surface Response Methodology

Abstract

Titanium dioxide (TiO 2 ) photocatalysis is one of the most commonly studied advanced oxidation processes (AOPs) for the mineralization of deleterious and recalcitrant compounds present in wastewater as it is stable, inexpensive, and effective. Out of all, doping with metal and non-metals, and the heterojunction with another semiconductor were proven to be efficient methods in enhancing the degradation of organic pollutants under ultraviolet (UV) and visible light. However, complex degradation processes in the treatment of an actual wastewater are difficult to model and optimize. In the present study, the application of a modified photocatalyst, Ag/TiO 2 /Fe 2 O 3 , for the degradation of an actual confectionery wastewater was investigated. Factorial studies and statistical design of experiments using the Box-Behnken method along with response surface methodology (RSM) were employed to identify the individual and cross-factor effects of independent parameters, including light wavelength (nm), photocatalyst concentration (g/L), initial pH, and initial total organic carbon (TOC) concentration (g/L). The maximum TOC removal at optimum conditions of light wavelength (254 nm), pH (4.68), photocatalyst dosage (480 mg/L), and initial TOC concentration (11,126.5 mg/L) was determined through the numerical optimization method (9.78%) and validated with experimental data (9.42%). Finally, the first-order rate constant with respect to TOC was found to be 0.0005 min −1 with a residual value of 0.998.

Photocatalytic Degradation of Profenofos and Triazophos Residues in the Chinese Cabbage, Brassica chinensis, Using Ce-Doped TiO2

“…In the profenofos molecule, the bond lengths between P 13 -S 15 , C 6 -Br 10 , C 2 -Cl 11 , P 13 -O 26 and P 13 -O 12 are 2.1100 × 10 −10 , 1.91000 × 10 −10 , 1.78000 × 10 −10 , 1.76000 × 10 −10 , 1.76000 × 10 −10 , and 1.76000 × 10 −10 m, respectively, which are longer than other bonds. Similarly, the bond lengths between P 19 -S 20 in the triazophos molecule is the longest with the value of 1.85680 × 10 −10 m, followed by the bond lengths between P 19 -O 18 , P 19 -O 21 and P 19 -O 22 with the same value of 1.76000 × 10 −10 m. According to negative A major metabolic product of profenofos, 4-bromo-2-chlorophenol was widely reported in the photolysis [37], hydrolysis [38], and biodegradation [39,40]. However, there has been no relevant report on photocatalytic degradation products of profenofos using TiO 2 .…”

“…In the profenofos molecule, the bond lengths between P 13 -S 15 , C 6 -Br 10 , C 2 -Cl 11 , P 13 -O 26 and P 13 -O 12 are 2.1100 × 10 −10 , 1.91000 × 10 −10 , 1.78000 × 10 −10 , 1.76000 × 10 −10 , 1.76000 × 10 −10 , and 1.76000 × 10 −10 m, respectively, which are longer than other bonds. Similarly, the bond lengths between P 19 -S 20 in the triazophos molecule is the longest with the value of 1.85680 × 10 −10 m, followed by the bond lengths between P 19 -O 18 , P 19 -O 21 and P 19 -O 22 with the same value of 1.76000 × 10 −10 m. According to negative correlation between bond energy and bond length [49], the above longer bonds tend to cleave when attacked by ROS. This means the P 13 -O 12 bond in the profenofos molecule and the P 19 -O 18 bond in triazophos molecules are attacked first, leading to the P 13 14 1.45200 C 16 -C 17 1.50715 P 13 -O 26 1.76000 C 17 -C20 1.50713 P 13 -O 12 1.76000 O 26 -C 27 1.43000 P 13 -S 15 2.11000 C 27 -C 28 1.50025 C 16 -S 15 1.78000 O 12 -C 3 1.43000 C 3 -C 4 1.39543 C 1 -C 2 1.39516 C 4 -C 5 1.39483 C 2 -Cl 11 1.76000 C 5 -C 6 1.39514 C 2 -C 3 1.39471 C 6 -Br 10 1.91000 C 6 -C 1 1.39483…”

“…Triazophos P 19 -S 20 1.85680 N 3 -C 7 1.47000 P 19 -O 18 1.76000 C 7 -C 8 1.39516 P 19 -O 21 1.76000 C 7 -C 9 1.39483 P 19 -O 22 1.76000 C 8 -C 10 1.39471 O 18 -C 1 1.43000 C 9 -C 12 1.39514 C 1 -N 5 1.40175 C 10 -C 14 1.39543 C 1 -N 6 1.43487 C 12 -C 14 1.39483 C 2 -N 6 1.40185 O 21 -C 30 1.43000 C 2 -N 3 1.39180 O 22 -C 23 1.43000 N 3 -N 5 1.39180 C 30 -C 31 1.50025 C 23 -C 24 1.50025…”

“…To enhance the photocatalytic activity under the visible light, main-group element (Ce, N, C, Ag, etc.) doped nano TiO 2 was extensively applied [17][18][19][20]. Among them, Cerium-doped nano TiO 2 (TiO 2 /Ce) exhibits a strong photocatalytic capability under the visible lights [20][21][22].…”

Optimization of Ammonia Oxidation Using Response Surface Methodology

“…Because of its usability, this method is applied for the design, improvement and optimization of production processes and products [19][20][21]. It is a widely applied method in research of various processes [22][23][24][25][26][27] and approx. 50% of all applications is in medicine, engineering, biochemistry, physics and computer science [28].…”