Removal of dinitrotoluenes and trinitrotoluene from industrial wastewater by ultrasound enhanced with titanium dioxide.

Oxidative degradation of dinitrotoluenes (DNTs) and 2,4,6-trinitrotoluene (TNT) in wastewater was conducted using ultrasonic irradiation combined with titanium dioxide (TiO(2)). The batch-wise experiments were carried out to elucidate the influence of various operating parameters on the sonolytic behavior, including power intensity, TiO(2) dosage, acidity of wastewater, reaction temperature and oxygen dosage. It is worthy to note that the nitrotoluene contaminants could be almost completely eliminated by sonochemical oxidation enhanced significantly with the addition of TiO(2) due to the supply of adsorbent and/or excess nuclei. High destruction rate of nitrotoluenes could be achieved by increasing the acidity of wastewater and decreasing the reaction temperature. According to the result given by pyrolysis/gas chromatograph-mass spectrometer (Pyrolysis/GC-MS), it is postulated that DNTs adsorbed on TiO(2) preliminarily undergo denitration pathway to o-mononitrotoluene (MNT) or oxidation pathway to 1,3-dinitrobenzene (DNB), respectively. Further, based on the spectra obtained from GC-MS, it is proposed that DNTs dissolved in wastewater proceed with similar reaction pathways as those adsorbed on TiO(2). Besides, oxidative degradation of 2,4,6-TNT results in the formation of 1,3,5-trinitrobenzene (TNB). Apparently, the sonolytic technique established is promising for direct treatment of wastewater from TNT manufacturing process.

[Simultaneous determination of multi-organotin compounds in seawater by liquid-liquid extraction-high performance liquid chromatography-inductively coupled plasma mass spectrometry].

The hyphenated technique of high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was applied to the simultaneous determination of five organotin compounds (trimethyltin, dibutyltin, tributyltin, diphenyltin and triphenyltin) in seawater samples. Agilent TC-C18 column was used for the separation, the mobile phase of HPLC was CH3CN : H2O : CH3COOH = 65 : 23 : 12 (phi3), 0.05% TEA, and pH value was adjusted to 3.0 by diluent ammonia. The flow rate was 0.6 mL x min(-1). Five mixed organotin compounds in a mix standard solution from 100 to 0.5 microg x L(-1) were applied for the method assessment. The experimental results indicate that the correlation coefficient of calibration curves (R2) for each organotin compound was over 0.998 and the detection limits of the five organotin compounds were lower than 3 ng x L(-1). Different mixed organic solvents including dichloromethane or toluene were used for extraction of organotin and the extraction condition of organotin from seawater was optimized. The 100 mL seawater acidized by hydrochloric acid was extracted by 10 mL carbon dichloride (CH2 Cl2) with 2% tropolone for 10 min twice. Extracted organic solvents were mixed and blown to one drop by nitrogen with the rate of 1.7 mL x min(-1), then 1 mL acetonitrile was added to the drop for redissolving the organotin compounds. Finally, the mixed redissolution was filtered by 0.22 microm organic filter membrane before analysis. It was found that the only organotin compound in seawater was triphenyltin (TPHT) and the content was 53.2 ng x L(-1). The recoveries test from the standard addition for diphenyltin (DPHT), dibutyltin (DBT), tributyltin (TBT) and triphenyltin (TPHT) were over 80%. However, the recovery for trimethyltin (TMT) was relatively low and the value was 50%. The reason might be attributed to the decomposition or adsorption of those compounds during the extraction procedure. Further study on this subject is in progress.