The commonly used photocatalyst, TiOl (anatase), has been immobilized on porous nickel using 3 wt.% polyvinyl alcohol (PVA) as the binder. The results show that sulfosalicylic acid (SSal) can be degraded on the developed catalytic system. The adsorption characteristics on TiOz-Ni system have been investigated. The observance of photocalytic degradation of SSal under pH values and initial concentrations can be explained by the adsorption behavior of SSal. The parameters of the Langmuir-Hinshelwood expression have been determined by different experimental ways and the results are satisfactory.

In this study, conventional TiO2 powder was heated in hydrogen (H2) gas at a high temperature as pretreatment. The photoactivity of the treated TiO2 samples was evaluated in the photodegradation of sulfosalicylic acid (SSA) in aqueous suspension. The experimental results demonstrated that the photodegradation rates of SSA were significantly enhanced by using the H2-treated TiO2 catalysts and an optimum temperature for the H2 treatment was found to be of 500-600℃. The in situ electron paramagnetic resonance (EPR) signal intensity of oxygen vacancies (OV) and trivalent titanium (Ti3+) associated with the photocatalytic activity was studied. The results proved the presence of OV and Ti3+ in the lattice of the H2-treated TiO2 and indicated that both were contributed to the enhancement of photocatalytic activity. Moreover, the experimental results presented that the EPR signal intensity of OV and Ti3þ in the H2-treated TiO2 samples after 10 months storage was still significant higher than that in the untreated TiO2 catalyst. The experiment also demonstrated that the significant enhancement occurred in the photodegradation of phenol using the H2-treated TiO2.

The photocatalytic degradation of gaseous trichloroethylene (TCE) without water has been studied. The degradation products were determined to be CO2. HCl and Cl2, and the reaction stoichiometr\,h v was described as C2HCI3+ 2O2hv→HO2 HCI+2C0, +Cl2,. The degradation rate was found to be linear with 0.16 power of the illumination intensity. When the TC’E concentration was low (10-4mol L-1 or a little more), its degradation rate model could be considered as first order kinetics. A mechanism oi valence band hole oxidation was proposed.

The photocatalytic (PC) degradation kinetics of sulfosalicylic acid (SSA) at different pH using TiO2 microspheres were elucidated by modeling. The resultant model had special consideration of adsorption and pH. The adsorption isotherms showed that the LC/MS2-identified intermediateswereweakly adsorbed on the TiO2 microspheres, thus their adsorptionwas neglected in the modeling. By contrast, the SSAwas significantly adsorbed, thus its adsorption retained as an item in the model. Consequently, a non-first-order modelwas obtained. Through the modeling, itwas elucidated that the reaction rate increased non-linearly with the SSA adsorption equilibrium constant. Meanwhile, it was elucidated that a pH increase favored the hydroxyl radical production to accelerate the SSA degradation, while impeded the SSA adsorption to slower it, hence a neutral pH caused the fastest SSA degradation.

To well describe the electro-Fenton (E-Fenton) reaction in aqueous solution, a new kinetic model was established according to the generally accepted mechanism of E-Fenton reaction. The model has special consideration on the rates of hydrogen peroxide (H2O2) generation and consumption in the reaction solution. The model also embraces three key operating factors affecting the organic degradation in the E-Fenton reaction, including current density, dissolved oxygen concentration and initial ferrous ion concentration. This analytical model was then validated by the experiments of phenol degradation in aqueous solution. The experiments demonstrated that the H2O2 gradually built up with time and eventually approached its maximum value in the reaction solution. The experiments also showed that phenol was degraded at a slow rate at the early stage of the reaction, a faster rate during the middle stage, and a slow rate again at the final stage. It was confirmed in all experiments that the curves of phenol degradation (concentration vs. time) appeared to be an inverted ‘‘S’’ shape. The experimental data were fitted using both the normal first-order model and our new model, respectively. The goodness of fittings demonstrated that the new model could better fit the experimental data than the first-order model appreciably, which indicates that this analytical model can better describe the kinetics of the E-Fenton reaction mathematically and also chemically.

In this work, the oxidation mechanism of hypophosphite anion (H2PO2-) in acidic and alkaline media in the presence of Ni(Ⅱ) specie was investigated by using electrochemical impedance spectroscopy (EIS) and density functional theory (DFT). In EIS, three major electrochemical processes in the electroless deposition process were found, when the solution pH ranged from 5.5 to 9.5. To understand the microscopic mechanisms involved, all participate species in the reaction pathways were calculated by the DFT method along with a natural bond orbital (NBO) analysis. Two emulating reactions were demonstrated: Path (Ⅰ) passes through a primary dehydrogenation (D-RP), and Path (Ⅱ) includes a primary addition of OH-(A-RP) on the hypophosphite anion. By comparison of the energy levels of all species, it can be concluded that Path (Ⅱ) is energetically favorable under both acidic and alkaline conditions. The DFT and NBO analysis can provide strong evidence for the loops detected in the EIS, especially especially for the inductive loop (IL-M) in the medium-frequency domain that is caused by the formation of [NiI-H3PO2(OH)] and the capacitive loop (CL-L) in the lowfrequency domain by [H2PO2(OH)]. The combination of electrochemical analysis (EIS) and first principle theory (DFT) analysis proves that it is helpful to explore the nature of the interaction between anodic and cathodic reactions in the electroless deposition process.

A three-electrode system composed of TiO2/Ni as the working electrode, porous nickel as the counter electrode, and saturated calomel electrode (SCE) as the reference electrode was used for the photoelectrocatalytic degradation of organic compounds. The photoelectrocatalytic degradation of sulfosalicylic acid (SSal) under anodic bias potential was investigated. It is shown that SSal can be degraded effectively as the external potential is increased up to 700 mV (vs SCE). The characteristics by electrochemical impedance spectroscopy (EIS) of the photoelectrocatalytic degradation of sulfosalicylic acid (SSal) was also investigated. It is shown from the EIS that the photoelectrocatalytic degradation appears to be a simple reaction on the electrode surface, suggesting that only one step of charge transfer is involved in the electrode process. The value of the resistance of charge transfer for the photoelectrocatalytic reaction of SSal manifests itself not only in the reaction rate, but also in the separation efficiency of the photogenerated electron-hole pairs. The separation efficiency of the electron-hole pairs under N2 atmosphere is higher than that under O2 atmosphere.

Thiswork investigated the effect of co-existing organic matters on aqueous Cr(VI) reduction by electrodeposited zero-valent iron (ED Fe0) at neutral pH. The ED Fe0 prepared in a solution containing mixture of saccharin, l-ascorbic acid and sodium dodecyl sulfate showed higher activity in reducing the aqueous Cr(VI) at neutral pH than that prepared without any organic presence. XRD and SEM indicated that the structure of ED Fe0 was significantly improved to nano-scale by the presence of organic mixture in the preparation solution. Further, the ED Fe0 activity in the Cr(VI) reduction at neutral pH was increased by the co-existence of citric acid or oxalic acid in the chromate solution. Electrochemical impedance spectroscopy (EIS) demonstrated that the corrosive current increased with the concentration of organic matter in the reaction solution. With the co-existing organic matters in the preparation solution, the ED Fe0 corroded more rapidly due to its nano-size, thus the Cr(VI) reduction by the ferrous iron was accelerated. With the co-existing organic matters in the reaction solution, the Cr(VI) reduction was accelerated by a Fe(II) complex as the main electron donor, and a prevention of the passivation due to the Fe(III) and Cr(III) complexes also accelerated the Cr(VI) reduction.

The conventionally employed zero-valent iron (Fe0) particles suffer a formation of surface oxides to lower their activity prior to use. During their using process for contaminant remediation, such oxide formation is also encountered, while the cumbersome handling of particles impedes the Fe0 recovery. To conquer the drawbacks, a Fe0 film was synthesized by electrodepositing ferrous ion cathodically on titanium (Ti) substrate to form a new Fe0/Ti system. X-ray diffraction (XRD) revealed that the freshly electrodeposited (FED) Fe0 film was free of oxides, which was attributed to the particularity of electrodeposition procedure. Reduction results of 10.0 mg/L chromium [Cr(VI)] indicated that the FED Fe0 film had higher activity than the oxide-covered counterpart. Further analysis of the pH-dependent Cr(VI) reduction reaction indicated that the Fe0/Ti system kept its activity and could be reused for further Cr(VI) reduction at pH 3.0 and 4.0, while it was inactivated at pH 5.0 and 7.0. Due to the easy handling of Fe0/Ti system, the inactivated Fe0 was recovered significantly through a cathodic reduction.

The photocatalytic degradation of aniline was studied in annular photoreactor, with 2 6W (EmaxD365 nm) UV lamp as light source, borosilicate glass as wave filter and titanium dioxide immobilized on porous nickel as catalysts. Parameters such as the initial concentration, flow rate, initial pH, dissolved oxygen, electrolyte, hydrogen peroxide addition, temperature and external potential bias affecting the degradation rate of aniline were studied. The results showed that photocatalysis is an effective process for the degradation of aniline. The activated energy for the photocatalytic degradation of aniline is 6.13 kJ mol-1. The initial quantum yield is 1.89% for aniline 1.10×10-4 mol l-1. Total mineralization requires a much longer illumination time than the disappearance of anilines. The external potential bias can largely improve the efficiency of photocatalytic degradation of aniline. The degradation kinetic of aniline can be described by Langmuir-Hinshelwood equation.