Chia-Chi Su

Acetaminophen degradation by electro-Fenton and photoelectro-Fenton using a double cathode electrochemical cell.

Acetaminophen is a widely used drug worldwide and is one of the most frequently detected in bodies of water making it a high priority trace pollutant. This study investigated the applicability of the electro-Fenton and photoelectro-Fenton processes using a double cathode electrochemical cell in the treatment of acetaminophen containing wastewater. The Box-Behnken design was used to determine the effects of initial Fe(2+) and H(2)O(2) concentrations and applied current density. Results showed that all parameters positively affected the degradation efficiency of acetaminophen with the initial Fe(2+) concentration being the most significant parameter for both processes. The acetaminophen removal efficiency for electro-Fenton was 98% and chemical oxygen demand (COD) removal of 43% while a 97% acetaminophen removal and 42% COD removal were observed for the photoelectro-Fenton method operated at optimum conditions. The electro-Fenton process was only able to obtain 19% total organic carbon (TOC) removal while the photoelectro-Fenton process obtained 20%. Due to negligible difference between the treatment efficiencies of the two processes, the electro-Fenton method was proven to be more economically advantageous. The models obtained from the study were applicable to a wide range of acetaminophen concentrations and can be used in scale-ups. Thirteen different types of intermediates were identified and a degradation pathway was proposed.

Kinetic study of acetaminophen degradation by visible light photocatalysis.

In this work, a novel photocatalyst K3[Fe(CN)6]/TiO2 synthesized via a simple sol‐gel method was utilized to degrade acetaminophen (ACT) under visible light with the use of blue and green LED lights. Parameters (medium pH, initial concentration of reactant, catalyst concentration, temperature, and number of blue LED lights) affecting photocatalytic degradation of ACT were also investigated. The experimental result showed that compared to commercially available Degussa P‐25 (DP‐25) photocatalyst, K3[Fe(CN)6]/TiO2 gave higher degradation efficiency and rate constant (kapp) of ACT. The degradation efficiency or kapp decreased with increasing initial ACT concentration and temperature, but increased with increased number of blue LED lamps. Additionally, kapp increased as initial pH was increased from 5.6 to 6.9, but decreased at a high alkaline condition (pH 8.3). Furthermore, the degradation efficiency and kapp of ACT increased as K3[Fe(CN)6]/TiO2 loading was increased to 1 g L−1 but decreased and eventually leveled off at photocatalyst loading above this value. Photocatalytic degradation of ACT in K3[Fe(CN)6]/TiO2 catalyst system follows a pseudo–first‐order kinetics. The Langmuir–Hinshelwood equation was also satisfactorily used to model the degradation of ACT in K3[Fe(CN)6]/TiO2 catalyst system indicated by a satisfactory linear correlation between 1/kapp and Co, with kini = 6.54 × 10−4 mM/min and KACT = 17.27 mM−1.

Barium recovery by crystallization in a fluidized-bed reactor: effects of pH, Ba/P molar ratio and seed.

The effects of process conditions, including upward velocity inside the column, the amount of added seed and seed size, the pH value of the precipitant or the phosphate stream and the Ba/P molar ratio in a fluidized-bed reactor (FBR) were studied with a view to producing BaHPO₄ crystals of significant size and maximize the removal of barium. XRD were used to identify the products that were collected from the FBR. Experimental results show that an upward velocity of 48 cmmin(-1) produced the largest BaHPO₄ crystals with a size of around 0.84-1.0mm. The addition of seed crystals has no effect on barium removal. The use of a seed of a size in the ranges unseeded<0.149-0.29 mm<0.149 mm<0.29-0.42 mm produced increasing amounts of increasingly large crystals. The largest BaHPO₄ crystals were obtained at pH 8.4-8.8 with a Ba/P molar ratio of 1.0. In the homogeneous and heterogeneous processes, around 98% of barium was removed at pH 8.4-8.6 and [Ba]/[P]=1.0. The XRD results show that a significant amount of barium phosphate (Ba₃(PO₄)₂) was obtained at pH 11. The compounds BaHPO₄ and BaO were present at a pH of below 10.

Effect of the iron oxide catalyst on o-toluidine oxidation by the fluidized-bed Fenton process

This study investigates the effects of the Fe2+ concentration and synthetic iron oxide catalysts on o-toluidine degradation using a fluidized-bed Fenton process. The mineralization of o-toluidine in the synthetic catalyst system is also examined. The H3.5 and H7.3 Fe/SiO2 and A7.8 and A12.5 Fe/SiO2 catalysts were successfully synthesized by adding H2O2 and injecting air process, respectively. The optimum initial ferrous ion concentration for degradation of 1 mM o-toluidine was 1 mM. Experimental results reveal that 1 mM o-toluidine can be 100% degraded at 60 and 120 min in the modified fluidized-bed Fenton process with A7.8 Fe/SiO2 and the conventional fluidized-bed Fenton process with SiO2 carrier, respectively, when the optimum conditions of 1 mM Fe2+ and 17 mM H2O2 at pH 3 were used. The A7.8 Fe/SiO2 catalyst had a stronger oxidation ability than the H3.5 Fe/SiO2, H7.3 Fe/SiO2 and A12.5 Fe/SiO2 catalysts, and was attributed to the high iron content on the surface of the SiO2 support. The Fenton and Fenton-like reactions occurred in the A7.8 Fe/SiO2 catalyst system. Degradation of o-toluidine in the Fenton-like process follows pseudo-first-order kinetics. The A7.8 Fe/SiO2 catalyst efficiently enhanced o-toluidine oxidation under the pH range of 2–4.

Application of Fered-Fenton process for m-phenylenediamine degradation

This study was undertaken to investigate the feasibility of applying the Fered-Fenton process to the degradation of m-phenylenediamine, by examining the effect of varying the initial H2O2 and Fe2+ concentrations, the initial pH and electric current on the process efficiency. The degradation behavior of m-phenylenediamine was also compared to that of aniline. The Fered-Fenton reactor consists of anodes and cathodes with mesh-type titanium metal coated with IrO2/RuO2 and stainless steel, respectively. The experiments showed that m-phenylenediamine was rapidly degraded by the Fered-Fenton process. Initial pH of 3.2 is optimal for the removal of m-phenylenediamine and chemical oxygen demand (COD). m-Phenylenediamine and COD removal efficiencies increased with the increasing electrical current from 0 A to 4 A, and decreased with a further increase in electrical current. Optimum efficiency resulting in 100% degradation of m-phenylenediamine and elimination of 30% of COD was achieved at pH 3.2 at 60 min in the presence of 10 mM of m-phenylenediamine, 0.268 mM of Fe2+, 43.6 mM of H2O2, and under a current of 4 A.