[Sodium peroxydisulfate activation by heat and Fe(II) for the degradation of 4-CP].

The heat and ferrous ion-activated sodium peroxydisulfate (PDS) for the oxidation of 4-chlorophenol (4-CP) was investigated. These processes are based on the generation of sulfate radicals, which are powerful oxidizing species found in nature. The effects of temperature, pH, the initial concentrations of Fe (II), PDS and citric acid on the degradation efficiencies of 4-CP were studied. The results show that the degradAtion efficiency of 4-CP is significantly enhanced as temperature increases. The degradation efficiencies of 4-CP are 2.5% and 43.5% within 4 h at 30 degrees C and 50 degrees C, respectively. Moreover, 4-CP is degraded completely at 60 degrees C. The degradation efficiency of 4-CP follows the order: pH 4.0 > pH 7.0 > pH 10.0. In the PDS/Fe (II) system, ferrous ion played an important role in generating sulfate radicals at ambient temperature. The optimum experimental condition is established and the addition of probe compounds proves the formation of sulfate radicals. Furthermore, the iron availability in the aqueous solution is manipulated with the optimum amount of citric acid, as a chelating agent. The degradation efficiency of 4-CP is 50.9% in the PDS/Fe (II)/citric acid system, which is superior to 43.5% at 50 degrees C under the same initial concentration of PDS.

[Microwave thermal remediation of soil contaminated with crude oil enhanced by granular activated carbon].

The advantage of rapid, selective and simultaneous heating of microwave heating technology was taken to remediate the crude oil-contaminated soil rapidly and to recover the oil contaminant efficiently. The contaminated soil was processed in the microwave field with addition of granular activated carbon (GAC), which was used as strong microwave absorber to enhance microwave heating of the soil mixture to remove the oil contaminant and recover it by a condensation system. The influences of some process parameters on the removal of the oil contaminant and the oil recovery in the remediation process were investigated. The results revealed that, under the condition of 10.0% GAC, 800 W microwave power, 0.08 MPa absolute pressure and 150 mL x min(-1) carrier gas (N2) flow-rate, more than 99% oil removal could be obtained within 15 min using this microwave thermal remediation enhanced by GAC; at the same time, about 91% of the oil contaminant could be recovered without significant changes in chemical composition. In addition, the experiment results showed that GAC can be reused in enhancing microwave heating of soil without changing its enhancement efficiency obviously.

[Selective catalytic reduction of NOx over Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalysts].

Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalyst was prepared by sol-gel and impregnation. Furthermore, selective catalytic reduction of NOx over Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalyst with propylene under lean burn condition was studied. The effects of the concentration of tetra-n-butyl titanate and dipcoat cycles on TiO2 washcoat were studied by SEM, and the effects of Pd concentration, O2 concentration and gas velocity on catalytic activity were investigated. The experimental results showed that the TiO2 washcoat on wire-mesh support is even and crack-free when the support is impregnated in 20.0% tetra- n-butyl titanate sol for 2 cycles. The NOx conversion decreases with Pd concentration increase. When Pd concentration is 0.23%, NOx conversion is highest. NOx conversion increases with oxygen concentration increase in the range of 1.5%-6.0%. However, when oxygen concentration is higher than 6.0%, NOx conversion decreases with increasing oxygen concentration. The NOx conversion decreases with gas velocity increase and its effect is severer at high temperature than low temperature.

[Photochemical degradation of petroleum on soil surfaces under simulated visible light].

The factors influencing photochemical degradation of petroleum on soil surfaces under simulated visible light, such as the initial oil concentrations, soil types and pH, were investigated. The concentrations of petroleum in photolytic processes were analyzed by UV-Vis. GC-FID and FTIR were used for the characterization of petroleum hydrocarbons. Experimental results indicated that photochemical degradation of petroleum on soil surfaces followed pseudo first-order kinetics with the rate constant of 0.0026-0.0172 h(-1) and half-life of 40-267 h. GC-FID analysis showed that, after 50 h of irradiation, the content of saturated hydrocarbons with longer chain decreased, while the proportion of shorter chain ones increased slightly; in addition, most chromatogram peaks of aromatics weakened or disappeared. After 60 h of photolysis, the appearance of carbonyl compounds in FTIR spectra of the extract from soil demonstrated that petroleum was gradually oxidized in the photolytic process.

[Effects of solid-to-solution ratio on sorption of dissolved petroleum hydrocarbons to soils].

The influence of solid-to-solution ratio (SSR) on the sorption and desorption of dissolved petroleum hydrocarbons (DPH) to two surface soils (agricultural and black) was evaluated by batch reactor experiments. Previous characterization suggested that the organic carbon content (OC) of black soil was higher. The sorption and desorption isotherms at different SSRs fit well to a linear equation. Desorption hysteresis due to sorption irreversibility was observed and hysteresis index (HI) used to quantify the desorption hysteresis increased from 1.43 to 2.21 with increasing SSR from 10.00 g x L(-1) to 75.00 g x L(-1) for agricultural soil (OC = 1.54%) and increased from 1.18 to 1.37 with increasing SSR from 2.50 g x L(-1) to 5.00 g x L(-1) for black soil (OC = 15.91%), indicating that an increase of SSR and decrease of OC of soils caused a simultaneous increase in sorption irreversibility of DPH. The organic-carbon-normalized sorption coefficients (K(OC)) derived from sorption isotherms, were dependent on SSR. A SSR-effect isotherm equation for a given system, which could be applied in the extrapolation of batch-measured sorption parameters to field conditions, was established.

[Effect of temperature and denitrifying phosphorus on nitrogen and phosphorous removal in SBMBBR].

The effect of two kinds of temperature conditions (14 degrees C +/- 1 degrees C and 24 degrees C +/- 1 degrees C) on the removal of phosphorus and nitrogen were studied in a sequencing batch moving bed biofilm reactor (SBMBBR). The experiments were performed at the concentrations of COD, nitrogen and phosphorus in the feed fixing at about 450 mg/L, 40 mg/L and 10 mg/L, respectively. The results indicated that under the two temperatures the phosphorus release amounts were 54.7 mg/L, 19.7 mg/L, and the phosphorus removals were 98.3%, 83.4%, and the total nitrogen removals were 87.8%, 98.4%, respectively. It found that PAOs (phosphorus-accumulating organisms) predominated in the biomass and the nitrifying level was low at the lower temperature. However, with increase of temperature, PAOs were no longer the predominant microbial species and the total nitrogen removal efficiency increased. A denitrifying phosphorus experiment was carried out under the mode of anaerobic/anoxic in the SBMBBR after 3 months anaerobic/oxic operation. The results showed the ratio of denitrifying phosphorus removal to total phosphorus removal was about 80%.

[Kinetics of enhanced adsorption by polarization for organic pollutants on activated carbon fiber].

The adsorption kinetics for model pollutants on the activated carbon fiber (ACF) by polarization was investigated. Kinetics data obtained for the adsorption of these model pollutants at open-circuit and 400mV, -400mV polarization was applied to the Lagergren equation, and adsorption rate constants (Ka) were determined. With the anodic polarization of 400mV, the capacity of sodium phenoxide increases from 0.0083mmol x g(-1) at open-circuit to 0.18mmol x g(-1), and a seventeen-fold enhancement is achievable; however, the capacity of p-nitrophenol decreases from 2.93 mmol x g(-1) at open-circuit to 2.65 mmol x g(-1). With the cathodal polarization of -400mV, the capacity of aniline improves from 3.60 mmol x g(-1) at open-circuit to 3.88 mmol x g(-1); however, the capacity of sodium dodecylbenzene sulfonate reduces from 2.20 mmol x g(-1) at open-circuit to 1.59 mmol x g(-1). The enhancement for electrosorption changes with different groups substituting. Anodic polarization enhances the adsorption of benzene with electron-donating group. But whether anodic or not cathodal polarization has less effect on the adsorption of electron-accepting aromatic compounds, and decreases the adsorption of benzene bearing donor-conjugate bridge-acceptor but increases the adsorption rate. Electrostatic interaction plays a very important role in electrosorption of ion-pollutants.

Enhanced photodegradation of phenolic compounds by adding TiO2 to soil in a rotary reactor.

Photodegradation of pentachlorophenol (PCP) and p-nitrophenol (PNP) in soil was carried out in a designed rotary reactor, which can provide the soil particles with continually uniform irradiation, and on a series of thin soil layers. TiO2, as a kind of environmental friendly photocatalyst, was introduced to the soil to enhance the processes. Compared with that on the soil layers, photodegradation of PCP at initial concentration of 60 mg/kg was improved dramatically in the rotary reactor no matter whether TiO2 was added, with an increase of 3.0 times in the apparent first-order rate constants. The addition of 1 wt% TiO2 furthered the improvement by 1.4 times. Without addition of TiO2, PNP (initial concentration of 60 mg/kg) photodegradation rate in the rotary reactor was similar to that on the soil layers. When 1 wt% additional TiO2 was added, PNP photodegradation was enhanced obviously, and the enhancement in the rotary reactor was 2 times of that on the soil layers, which may be attributed to the higher frequency of the contact between PNP on soil particles and the photocatalyst. The effect of soil pH and initial concentrations of the target compounds on the photodegradation in the rotary reactor was investigated. The order of the degradation rate at different soil pH was relative to the aggregation of soil particles during mixing in the rotary reactor. Photodegradation of PCP and PNP at different initial concentrations showed that addition of TiO2 to enhance the photodegradation was more suitable for contaminated soil with higher concentration of PCP, while was effective for contaminated soil at each PNP concentration tested in our study.

Interaction of humic substances and hematite: FTIR study.

The present work extended the knowledge on the binding and complexation of humic substances( humic acid or fulvic acid) and hematite by Fourier transform infrared spectroscopy( FTIR) . The FTIR data gained gave the consist evidences by two different sampling preparation methods that the interaction mechanism between humic substances and hematite was mainly conform to the ligand-exchange involving carboxylic functional groups of humic substances and the surfaces sites of hematite. The present method, although associated with some uncertainties, provided an opportunity to increase the knowledge in this field.

Photocatalytic remediation of gamma-HCH contaminated soil induced by alpha-Fe2O3 and TiO2.

Heterogeneous photocatalytic degradation of gamma-HCH on soil surfaces was carried out to evaluate the photocatalytic effectiveness of alpha-Fe2O3 and TiO2 toward degrading gamma-HCH on soil surfaces. After being spiked with gamma-HCH, soil samples were loaded with alpha-Fe2O3 or TiO2 and exposed to UV-light irradiation. Different catalyst loads, 0%, 2%, 5%, 7%, and 10% (wt.) alpha-Fe2O3; 0%, 0.5%, 1%, 2: (wt.)TiO2, were tested for up to 7 d irradiation. The effects of soil thickness, acidity, and humic substances were also investigated. The obtained results indicated that the gamma-HCH photodegradation follows the pseudo-first-order kinetics. The addition of alpha-Fe2O3 or TiO2 accelerates the photodegradation of gamma-HCH, while the photodegradation rate decreases when the content of alpha-Fe2O3 exceeds 7% (wt.). The degradation rate increases with the soil pH value. Humic substances inhibit the photocatalytic degradation of gamma-HCH. Pentachlorocyclohexene, tetrachlorocyclohexene, and trichlorobenzene are detected as photodegradation intermediates, which are gradually degraded with the photodegradation evolution.

Effects of nature organic matters and hydrated metal oxides on the anaerobic degradation of lindane, p, p '-DDT and HCB in sediments.

Effects of natural organic matters( NOM) and hydrated metal oxides( HMO) in sediments on the anaerobic degradation of gamma-666, p,p'-DDT and HCB were investigated by means of removing NOM and HMO in Liaohe River sediments sequentially. The results showed that the anaerobic degradation of gamma-666, p,p'-DDT and HCB followed pseudo-first-order kinetics in different sediments. But, the extents and rates of degradation were different, even the other conditions remained the same. Anaerobic degradation rates of gamma-666, p,p'-DDT and HCB were 0.020 d(-1), 0.009 d(-1) and 0.035 month(-1) respectively for the sediments without additional carbon resources. However, with addition of carbon resources, the anaerobic degradation rates of gamma-666, p,p'-DDT and HCB were 0.071 d(-1), 0.054 d(-1) and 0.088 month(-1) in the original sediments respectively. After removing NOM, the rates were decreased to 0.047 d(-1), 0.037 d(-1) and 0.066 month(-1); in the sediments removed NOM and HMO, the rates were increased to 0.067 d(-1) , 0.059 d(-1) and 0.086 month(-1). These results indicated that NOM in the sediments accelerated the anaerobic degradation of gamma-666, p,p'-DDT and HCB; the HMO inhibited the anaerobic degradation of gamma-666, p,p'-DDT and HCB.

Electrically enhanced photodegradation of an azodye (acid orange II) using a Pt/TiO2 film electrode irradiating with an UV lamp.

A photoelectrochemical process in the degradation of an azodye (Acid Orange II) on a Pt/TiO2 film electrode was investigated. By using the glass device and the voltage stabilized source of direct current, decolorization ratios higher than 78% were observed during aperiod of 5 h. Comparing this value with the sum of the decolorization ratios obtained by a sole application of electrochemical (lower than 3%) and photochemical (about 23%) procedures, a significant synergic effect between both processes was observed. The effects of adscititious voltage and pH value on the decolorization ratios were obvious while the effect of the amount of aeration was minor.

Description of adsorption of hydrophobic organic compounds on sediment using multi-component adsorption model.

A chemical sequential separation procedure for sediment has been developed for the adsorptive investigation of hydrophobic organic compounds(HOCs) including four fractions: carbonate, hydrous metallic oxide(ferric oxide, manganese oxide and alumina), clay and organic matter. Adsorption isotherms of these hydrophobic solute probes, such as hexachloroethane, lindane and 1, 2, 4, 5-tetrachlorobenzene were measured for model sorbents, model and natural sediment, and the latter of which was pretreated with the simplified sequential separation method. The linear and Langmuir models are applied to correlate the experimental data of humic substance and other model sorbents respectively. Multi-component Adsorptive Model (MCAM) was used to simulate adsorption isotherms of model and natural sediment. The results reveal that(1) the separation efficiencies of carbonate, organic matter, ferric oxide, manganese oxide and alumina are 98.1%, 72.5%, 82.6%, 93.5% and 83.3%, respectively; (2) except for removing metallic oxide, the external structure of sediment is not changed greatly after separation; (3) the MCAM correlates the data of adsorption isotherm rather well with the maximal relative deviations of 9.76%, 6.78% and 9.53% for hexachloroethane, lindane and 1, 2, 4, 5-tetrachlorobenaze in model sediment, respectively. The MCAM can clearly give expression to the different adsorptive mechanisms for HOCs in organic and inorganic matter, though the experimental data in each component are not very accurate due to the sequential separation efficiency.