[Show abstract][Hide abstract] ABSTRACT: A platinum modified graphite (Pt/G) electrode was synthesized by electrodeless technique using sodium borohydride (NaBH4) as the electron donor. Cyclic voltammetry (CV) was used to investigate the electrical double layer characteristics of Pt/G in 0.17 M Na2SO4 electrolyte. The surface reactivity was studied by the electrochemical oxidation of chloride. The electrodeless process enables the deposition of Pt metallic nanoparticles of approximately 15 nm in diameter uniformly dispersed on the graphite surface. The Pt/G exhibited both polarizable and reversible electrode properties. By evaluating the current–potential responses at various applied potential and pH values, it is possible to establish the potential and pH at points of zero charge, i.e., Epzc and pHpzc, respectively. The electrochemical reaction over the Pt/G and the G electrode were studied by chloride oxidation in Na2SO4 electrolyte. Results showed that the current efficiency in terms of chlorine evolution at constant current, on the Pt/G electrode was significantly improved over the raw graphite.
[Show abstract][Hide abstract] ABSTRACT: Effects of ferrite materials as supports (CoFe2O4, NiFe2O4, and Fe3O4) on nano-TiO2 were elucidated by their use in the oxidation of methylene blue. These photocatalysts, which were synthesized by co-precipitation, were characterized by XRD, SEM, EDS and VSM. The crystalline phase of TiO2 onto magnetic MFe2O4 was formed by anatase and rutile. TiO2/CoFe2O4 exhibited the strongest magnetic property of the prepared catalysts, and the photocatalytic efficiencies followed the order TiO2/CoFe2O4 > TiO2/NiFe2O4 > TiO2/Fe3O4. MB decolorization was enhanced with the amount of TiO2 on the photocatalyst, and was moderately affected by the extent of structural distortion of ferrite supports.
No preview · Article · Sep 2015 · Catalysis Communications
[Show abstract][Hide abstract] ABSTRACT: Struvite crystallization has been widely studied for phosphate removal and recovery from aqueous systems. In this study, struvite crystallization was carried out in a fluidized-bed reactor. Multivariate optimization was conducted using Box–Behnken design (BBD) with influent pH, influent phosphate concentration, and Mg/P molar ratio as independent variables. The output variables comprised total and dissolved phosphate concentrations, ammonium and magnesium concentrations, and fines concentrations. Experimental values of the total phosphate and dissolved phosphate concentrations ranged from 25.6 to 109.4 mg/L and from 7.6 to 39.3 mg/L, respectively, while the fines concentration varied from 5.2 to 101.6 mg/L. Quadratic mathematical models describing the response behavior of experimental BBD data were generated for total phosphate, dissolved phosphate, and fines concentration. The model p-values ( <0.0001) were significant and their lack-of-fit p-values ( >0.05) were insignificant. Numerical optimization of process parameters was conducted to minimize total and dissolved phosphate, ammonium and magnesium concentrations, and fines concentration in the effluent. At influent phosphate concentration of 300 mg/L, the results converged to a set of operating conditions: pH 9.5 and Mg/P = 1.3. The close agreement between the data from the validation experiment and the model-predicted values (relative error < 10%) indicates the robustness of the models.
Full-text · Article · Jun 2015 · Desalination and water treatment
[Show abstract][Hide abstract] ABSTRACT: In this study, the electro-Fenton process was used to treat synthetic and actual TFT-LCD wastewaters. TFT-LCD wastewater contains high amounts of organic solvents mainly dimethyl sulfoxide (DMSO). For the simulated TFT-LCD wastewater, response surface methodology (RSM) was used to fit experimental data to empirical models with the responses,%DMSO removal and H2O2 efficiency (Δ[H2O2]/Δ[DMSO]). Among the studied independent variables that affect DMSO degradation efficiency, Fe2+ loading was found to be the most dominant, then pH and, H2O2 loading being the least significant. DMSO removal and H2O2 efficiency improved with high Fe2+ loading, low H2O2 loading and low solution pH. The observed decrease in pH was attributed to the production of acidic degradation intermediates of DMSO. At 5 mM DMSO loading, treatment efficiency reached 100% DMSO removal. The electro-Fenton technology was also applied to real TFT-LCD wastewater resulting in TOC and COD removals of 68% and 79%, respectively.
Full-text · Article · May 2015 · Separation and Purification Technology
[Show abstract][Hide abstract] ABSTRACT: In this study, phosphate was removed from aqueous solution and recovered as struvite (MAP, MgNH4PO4·6H2O) by fluidized-bed crystallization (FBC) process. The effects of influent pH and Mg/P molar ratio on MAP crystallization were investigated. Thermal analysis and characterization of the MAP crystals collected from the fluidized-bed reactor (FBR) were performed. The kinetics and thermodynamics of the MAP decomposition reaction were determined using the Coats–Redfern method. Experimental results show that the total concentration of phosphate in the fluidized-bed reactor (FBR) increased with influent pH and Mg/P molar ratio. Thermal analysis of MAP decomposition at different temperatures revealed two distinct stages: (1) removal of H2O from the crystal surface and (2) removal of NH3. H2O and NH3 removal were highly endothermic, non-spontaneous and thermodynamically unstable. Low pH and high Mg/P ratio favored the production of more stable MAP crystals. The FT-IR and XRD results verified the formation of magnesium hydrogen phosphate (MgHPO4) by the evolution of ammonium from MAP at temperatures between 200 and 500 °C, and its further conversion to magnesium phosphate oxide (Mg2P2O7) at temperatures greater than 800 °C.
No preview · Article · Sep 2014 · Journal of the Taiwan Institute of Chemical Engineers
[Show abstract][Hide abstract] ABSTRACT: 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).
No preview · Article · Jul 2014 · Journal of Environmental Science and Health Part A
[Show abstract][Hide abstract] ABSTRACT: The effects of influent pH, the magnesium:phosphate (Mg:P) molar ratio, seed type and inorganic ions (F−, SO42- and NO3-) on phosphate removal were investigated in a fluidized-bed reactor (FBR). Environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) were used to characterize the products collected from the FBR. Experimental results show that pH and the Mg:P molar ratio played significant roles in phosphate removal. Increasing the influent solution pH from 10 to 12 increased the final phosphate removal from 55% to around 100%. At influent solution pH of 8, increasing the Mg:P molar ratio from 1 to 1.5, and 2 raised the phosphate removal as well to 17%, 28% and 34%, respectively. The seed used and its presence had an effect on the initial phosphate removal rate. Phosphate removal efficiencies were 86%, 88% and 93% for the unseeded FBR, the FBR seeded with calcium phosphate and the FBR seeded with magnesium phosphate, respectively. The inorganic ions in simulated thin film transistors-liquid crystal display (TFT-LCD) wastewater did not significantly impact the phosphate removal. The XRD analysis confirmed that several magnesium phosphate species formed in all FBR experiments.
No preview · Article · Apr 2014 · Separation and Purification Technology
[Show abstract][Hide abstract] ABSTRACT: The effects of important parameters, Fe2+, H2O2 and initial acetaminophen concentrations, on the initial rate and efficiency of ACT degradation in the electro-Fenton (EF) and photoelectro-Fenton (PEF) processes were investigated. The effect of organic acids on the degradation of ACT molecules was also studied. Experimental results show that the initial rate and removal efficiency of ACT in the EF and PEF processes varied insignificantly with Fe2+ concentration. The initial rate and removal efficiency of ACT in the PEF process were higher than those in the EF process. At a high initial ACT concentration, the initial rate of ACT degradation in the EF process was lower than that in the PEF process. Acetic acid improved ACT degradation efficiency while malonic and oxalic acids reduced it. Oxalic acid exhibited the strongest inhibitory effect, reducing ACT degradation efficiency by 18%. In the presence of oxalic acid in solution, EF yielded a degradation efficiency of 79%, which should be compared to efficiencies of 9% and 3%, for the fluidized-bed and conventional Fenton processes, respectively, showing that the EF process involves beneficial Fe2+ regeneration.
Full-text · Article · Mar 2014 · Journal of the Taiwan Institute of Chemical Engineers
[Show abstract][Hide abstract] ABSTRACT: In this study, concentrations of several heavy metals (Cu, Pb, Zn, Ni, Cr, and Cd) were measured in Katelysia hiantina, Anomalocardia squamosa, Perna viridis, Anadara antiquata, Paphia undulata, and Sanguinolaria diphos bivalve mollusks from Da-Peng Bay Lagoon near the south-southwestern coast of Taiwan. The metal pollution index (MPI) values were highest and lowest in winter and autumn, respectively. The MPI value in the viscera of P. viridis was higher than in muscles. In all four seasons, Zn concentrations in viscera and muscles of P. viridis were higher than for other metals. The capacities of A. squamosa to accumulate the concentrations of Cu, Ni, and Cr and of A. antiquata to accumulate concentrations of Pb, Zn, and Cd were significant. Analytical results suggested that A. squamosa and A. antiquata may be used as bioindicators for monitoring Cu, Ni, Cr, Pb, Zn, and Cd heavy-metal pollution in Da-Peng Bay Lagoon throughout the year.
No preview · Article · Feb 2014 · Journal of Toxicology and Environmental Health Part A
[Show abstract][Hide abstract] ABSTRACT: 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 48cmmin(-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<0.149-0.29mm<0.149mm<0.29-0.42mm 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.
[Show abstract][Hide abstract] ABSTRACT: Acetaminophen (ACT), an over-the-counter analgesic and antipyretic, remains one of the most frequently used household medications. This drug persists in domestic effluents in significant concentrations even after conventional treatment. This study demonstrates the effectiveness of fluidized-bed Fenton process to decompose acetaminophen in synthetic wastewater. Parametric studies were conducted to evaluate the effects of initial pH, initial ACT concentration, Fe2+ and H2O2 dosages on ACT oxidation. At optimum operating parameters, up to 97.83% ACT degradation was attained after 2 h of reaction. For interference studies of organic acids (oxalic, fumaric, maleic, acetic, succinic, malonic, and formic acids), oxalic acid was found to limit ACT degradation to only 9.26%.
No preview · Article · Jan 2014 · Journal of Environmental Engineering
[Show abstract][Hide abstract] ABSTRACT: 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 ofo-toluidine in the synthetic catalyst system is also examined. The H3.5 and H7.3 Fe/SiO2 and A7.8 and A 12.5 Fe/SiO2 catalysts were successfully synthesized by adding H202 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 1mM Fe2+ and 17mM H202 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.
No preview · Article · Jan 2014 · Environmental Technology
[Show abstract][Hide abstract] ABSTRACT: Acetaminophen (ACT) was used as the target pollutant in this study. The effects of Fenton’s reagent by electro-Fenton (EF) and photoelectro-Fenton (PEF) processes were investigated to determine the ACT degradation. At pH 3, increasing the Fe2+ and H2O2 concentrations to maximum (from 0.01 to 0.10 mM and 5 to 25 mM), leads to increase on the hydroxyl radicals which improved the degradation efficiency of ACT. The results of Box–Benhken design show that Fe2+ and H2O2 positively affect the degradation efficiency of ACT, while pH was the reverse. The maximum ACT degradation efficiency for EF and PEF processes was 99% at 40 min under pH 3, initial [Fe2+] of 0.10 mM and initial [H2O2] of 25 mM. Result shows that H2O2 to Fe2+ molar ratio obviously affect acetaminophen degradation of both EF and PEF processes. Added UVA irradiation for first stage (PEFi/EFi) increased the acetaminophen degradation, when H2O2 to Fe2+ molar ratio was less than 300. On the contrary, applied UVA efficiency for second stage (PEFk/EFk) was decreased, because there was few hydrogen peroxide available in the solution.
No preview · Article · Dec 2013 · Separation and Purification Technology
[Show abstract][Hide abstract] ABSTRACT: Degradation of dimethyl sulfoxide (DMSO) was examined under varying parameters, including initial pH, initial Fe2+, initial H2O2, initial DMSO concentrations and current density. Efficiency in terms of degradation of DMSO and removal of total organic carbon (TOC) was also compared among Fenton, photo-Fenton and photoelectro-Fenton (PEF) processes. Effects of inorganic ions, namely Cl−, F− and View the MathML source, on DMSO degradation by the electro-Fenton (EF) process were also studied. The experimental results showed that the optimum pH was 2. The DMSO degradation in the double-cathode EF reactor reached 100% when current density and Fe2+ concentration exceeded 1.5 A and 2.0 mM, respectively. During DMSO degradation, application of electricity by EF process obtained a higher DMSO degradation rate compared to UV-assisted Fenton process. The DMSO degradation rate after 20 min was 2.5 times higher in the PEF process than in the Fenton process. Between 20 min and 120 min, the DMSO degradation rates of the Fenton, photo-Fenton, single-cathode EF, double-cathode EF and PEF processes differed by 34%, 50%, 62%, 57% and 59%, respectively. The rate constant of double-cathode EF process was six times higher than the conventional Fenton process. The order of inhibiting effects of inorganic ions on DMSO degradation was View the MathML source > F− > Cl−.
Full-text · Article · Oct 2013 · The Chemical Engineering Journal
[Show abstract][Hide abstract] ABSTRACT: This study investigated the photocatalytic degradation of acetaminophen (ACT) in synthetic titanium dioxide (TiO2) solution under a visible light (λ >440 nm). The TiO2 photocatalyst used in this study was synthesized via sol-gel method and doped with potassium aluminum sulfate (KAl(SO4)2) and sodium aluminate (NaAlO2). The influence of some parameters on the degradation of acetaminophen was examined, such as initial pH, photocatalyst dosage, and initial ACT concentration. The optimal operational conditions were also determined. Results showed that synthetic TiO2 catalysts presented mainly as anatase phase and no rutile phase was observed. The results of photocatalytic degradation showed that LED alone degraded negligible amount of ACT but with the presence of TiO2/KAl(SO4)2, 95 % removal of 0.10-mM acetaminophen in 540-min irradiation time was achieved. The synthetic TiO2/KAl(SO4)2 presented better photocatalytic degradation of acetaminophen than commercially available Degussa P-25. The weak crystallinity of synthesized TiO2/NaAlO2 photocatalyst showed low photocatalytic degradation than TiO2/KAl(SO4)2. The optimal operational conditions were obtained in pH 6.9 with a dose of 1.0 g/L TiO2/KAl(SO4)2 at 30 °C. Kinetic study illustrated that photocatalytic degradation of acetaminophen fits well in the pseudo-first order model. Competitive reactions from intermediates affected the degradation rate of ACT, and were more obvious as the initial ACT concentration increased.
No preview · Article · Jul 2013 · Environmental Science and Pollution Research
[Show abstract][Hide abstract] ABSTRACT: 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 Fe(2+) 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 Fe(2+), 43.6 mM of H2O2, and under a current of 4 A.
No preview · Article · Jul 2013 · Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering
[Show abstract][Hide abstract] ABSTRACT: Ferromagnetic elements Fe, Ni and Co were immobilized on the porous SiO2 to catalyze the hydrogen generation from aqueous alkaline NaBH4 (sodium borohydride). The porous SiO2 was prepared by silica-surfactant self-assembly and the ferromagnetic catalyst was prepared by chemical reduction. The ferromagnetic catalysts were characterized using TG/DTA (Thermogravimetry/differential thermal analysis), BET, XRD (X-ray powder diffraction), ESEM/EDS (environmental scanning electron microscope/energy dispersive spectroscopy), XPS (x-ray photoelectron spectroscopy) and VSM (vibration sample magnetometer) measurements. The surface area of porous SiO2 was affected by the molecular weight of surfactant. The relative catalytic activities in the generation of hydrogen from alkaline NaBH4 solution follow the order Co/SiO2 > Ni/SiO2 > Fe/SiO2. The rates of hydrogen generation using Co/SiO2, Ni/SiO2 and Fe/SiO2 catalysts in 20 ml of 5 wt.% NaBH4 solution at 313 K were 8701, 307 and 130 ml min−1 g−1-metal, respectively. It is found that the degree of metal-oxidation and crystal structure affected the catalytic activity. The hydrogen generation of NaBH4 in alkaline solution increased with increasing cobalt loading, of which the activation energy was 59 ± 2 kJ mol−1.
[Show abstract][Hide abstract] ABSTRACT: Synthetic wastewater containing monoethanolamine (MEA) and phosphate, which was generated during the cleaning and etching processes for thin-film transistor liquid crystal displays (TFT-LCDs) was treated using a novel process. Degradation of MEA was studied and compared using the Fenton and fluidized-bed Fenton processes. Comparison results show that the Fe2+ concentration was an important factor for MEA and chemical oxygen demand (COD) removal in the fluidized-bed Fenton process. The degradation of MEA followed pseudo-first-order reaction kinetics. The MEA, COD and total organic carbon (TOC) removal efficiencies by the fluidized-bed Fenton process after 60 min were 15–26% higher than those by the Fenton process. The phosphate removal rate followed a first-order reaction. Phosphate removal was optimized by selecting sand grains sized (0.24–0.5 mm) and a molar ratio of Fe2+/P of 1.3 at pH 7. In the two stages, optimized conditions were Fe2+/P = 1.3 at pH 7 using 100 g SiO2 for phosphate removal, and 3 mM Fe2+ and 50 mM H2O2 at pH 3 for MEA removal; phosphate removal efficiency was 45% and MEA removal efficiency was 76%.
Full-text · Article · Apr 2013 · The Chemical Engineering Journal
[Show abstract][Hide abstract] ABSTRACT: This study investigates the degradation of acetaminophen (ACTP) using a novel Fenton aerated reactor. The aerator was used to agitate and sludge was removed from a sludge outlet. The effects of operating parameters such as pH, Fe2+ and H2O2 concentrations on the initial rate of ACTP degradation (r), removal efficiency and mineralization were studied. The results indicate that a novel Fenton aerated reactor was successfully performed to degrade ACTP. The highest r value was obtained at pH 3. At pH 3, the r value and ACTP removal efficiency were significantly improved as the [Fe2+]:[H2O2] ratio increased. The removal efficiencies of ACTP, COD and TOC were 99%, 34% and 14%, respectively, at 40 min, when optimum conditions for 5 mM acetaminophen, 25 mM H2O2 and 0.1 mM Fe2+ were used at pH 3.
No preview · Article · Mar 2013 · Journal of the Taiwan Institute of Chemical Engineers