Dechlorination of carbon tetrachloride by the catalyzed Fe-Cu process.

The electrochemical reduction characteristics of carbon tetrachloride (CT) were investigated using cyclic voltammetry in this study. In addition, the difference in reduction mechanisms of CT between Master Builders' iron and the catalyzed Fe-Cu process was discussed. The results showed that CT was reduced directly on the surface of copper rather than by atomic hydrogen produced at the cathode in the catalyzed Fe-Cu process. The reduction was realized largely by atomic hydrogen in Master Builders' iron. The entire CT in 350 ml aqueous solution with 320 mg/L was reduced to trichloromethane and dichloromethane in 2.25 h when 100 g of scrap iron with Fe/Cu ratio of 10:1 (w/w) were used. Moreover, the reduction rate slowed with time. CT could be reduced at acidic, neutral and alkaline pH from solution by Fe-Cu bimetallic media, but the mechanisms were different. The degradation rate was not significantly influenced by pH in the catalyzed Fe-Cu process; in Master Builders' iron it clearly increased with decreasing pH. The kinetics of the reductions followed pseudo-first order in both cases. Furthermore, the reductions under acidic conditions proceeded faster than that under the neutral and alkaline conditions. The catalyzed Fe-Cu process was superior to Master Builders' iron in treating CT-containing water and this advantage was particularly noticeable under alkaline conditions. The reduction was investigated in the cathode (Cu) and anode (Fe) compartments respectively, the results showed that the direct reduction pathway played an important role in the reduction by the catalyzed Fe-Cu process. The catalyzed Fe-Cu process is of practical value.

[Electrochemical reduction characteristics and mechanism of chlorinated hydrocarbon at the copper electrode].

The electrochemical reduction characteristics of chlorinated hydrocarbons were investigated by applying cyclic voltammetry technique. The reduction mechanism and reactivity of the chlorinated hydrocarbons at the copper electrodes were explored. The relation between the reductive reactivity at the copper electrode and the structures of this kind of compounds was discussed. The experimental results show that chlorinated paraffin hydrocarbons and a portion of chlorinated aromatic hydrocarbons could be reduced directly at the copper electrode; however, chlorinated aromatic hydrocarbons aren't easy to reduced directly at the copper electrode. The results provide a theoretical basis for the catalyzed iron inner electrolysis method.

[Electrochemical reduction characteristics of nitro-benzene compounds at the copper electrode and the influence of pH on reduction].

The electrochemical reduction characteristics of nitro-benzene compounds were investigated using cyclic voltammetry technique. The reductive reactivity of the nitro-benzene compounds at the copper electrode was evaluated, the reduction mechanisms of the nitrobenzene compounds at the copper electrode and the influences of pH on them were also discussed in this paper. The experimental results show that nitro-benzene compounds is capable of reducing directly at the copper electrode, and the reduction peaks were at - 0.58V and - 1.32V or so (vs. SCE). Both acidity and basicity favor reduction of nitro-group at the copper electrode: the elimination reaction is easy to occur in the alkaline medium with the formation of nitroso-group; in the acid medium the probability of the reaction between the obtained electrons nitro group and hydrogen ions raises, which causes magnification of the current through the solution; in addition, the growth of hydrogen atoms in number favors the occurring of the addition and substitution reactions at the electrode. pH strongly influenced the electrochemical reduction characteristics of the nitrobenzene compounds at the copper electrode, and it mainly depends on the properties of the substituents on the benzene ring, their configurations and numbers, and their location versus nitro group on the benzene ring. The results provide a theoretical and experimental basis for investigating the reduction mechanisms by the catalyzed iron inner electrolysis process.

Reduction of nitrobenzene by the catalyzed Fe-Cu process.

The electrochemical reduction characteristics of nitrobenzene were investigated using cyclic voltammetry. In addition, the difference in reduction mechanisms between Master Builders' iron and the catalyzed Fe-Cu process was discussed in this paper. The results showed that nitrobenzene was reduced directly on the surface of copper rather than by the hydrogen evolved at cathode in the catalyzed Fe-Cu process. The reduction was realized largely by the hydrogen evolved at cathode in Master Builders' iron. Both acidity and basicity favored the direct reduction at the copper electrode. The catalyzed Fe-Cu process was superior to Master Builders' iron in treating nitrobenzene-containing water, withal. This advantage was particular noticeable under alkaline conditions. The reduction was investigated in the cathode and anode compartments, respectively, and the experimental results showed that the direct pathway had a large role in the reduction by the catalyzed Fe-Cu process. To reduce nitrobenzene directly at the copper electrode is easier than to reduce it by the hydrogen evolved at cathode, copper could be regarded as the electrocatalyst in this case. The influence of copper usage on the treatment efficiency by the catalyzed Fe-Cu process was also studied. The results indicated copper increased the reduction rate. The catalyzed Fe-Cu process is of practical value.

Ammonium removal by modified zeolite from municipal wastewater.

Ammonium removal by modified zeolite, H-form and Na-form zeolite, were examined by batch-type methods. The adsorption of ammonium on modified zeolite was exothermic process. The saturation adsorption capacity of ammonium on H-form and Na-form zeolite were 21.23 and 41.15 mg/g, respectively. After ten times adsorption-desorption-readsorption cycles the standard deviations of H-form and Na-form zeolite were 6.34% and 6.59%. The zeolite adsorption process has proved cost effective and practical in reducing ammonium by H-form and Na-form zeolite in municipal wastewater from concentration 27.68 mg/L to 2.80 mg/L and 5.91 mg/L.

Nitrogen and phosphorus removal under intermittent aeration conditions.

A practice wastewater treatment plant was operated using intermittent aeration activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of CODCr, BOD5, TN, TP, NH3-N, TKN, and SS varied in a range of 207.5-1640 mg/L, 61.8-637 mg/L, 28.5-75.6 mg/L, 4.38-20.2 mg/L, 13.6-31.9 mg/L, 28.5-75.6 mg/L, and 111-1208 mg/L, the effluent means were less than 50 mg/L, 20 mg/L, 5 mg/L, 1.0 mg/L, 5 mg/L, 10 mg/L, and 20 mg/L, respectively. Based on a long time of operating results, this process is very suitable for nutrient biological removal for treating the municipal wastewater those water characteristics are similar as that of the Songjiang Municipal Waste Water Treatment Plant(SJMWTP).