\ According to the analysis of the residual products by thermogravimetric analysis (TGA), the thermal decomposition process of cefazolin sodium (CEZ·Na) was thought to be similar to the degradation in solid sta...\ According to the analysis of the residual products by thermogravimetric analysis (TGA), the thermal decomposition process of cefazolin sodium (CEZ·Na) was thought to be similar to the degradation in solid state in its storage time. This laid a foundation for estimating the relative chemical stability of the drug by determination of its decomposition kinetics using TGA. Although the observed thermal decomposition kinetics of CEZ·Na was complex, a conversion level of 1% was chosen for evaluation of the stability of CEZ·Na crystalline since the mechanism here was more likely to be that of the actual product failure. The evaluation results suggested that the α form of CEZ·Na had the best stability and the amorphous one was the least stable one among α form, dehydrated α form and amorphous form.展开更多
An alginate-degrading bacterium, identified as Ochrobactrum sp. on the basis of 16S rDNA gene sequencing, was isolated from brown algal samples collected from the waters in close vicinity to the Dongtou isles of the E...An alginate-degrading bacterium, identified as Ochrobactrum sp. on the basis of 16S rDNA gene sequencing, was isolated from brown algal samples collected from the waters in close vicinity to the Dongtou isles of the East China Sea. The strain, designated WZUH09-1, is able to depolymerize alginates with higher enzyme activity than that of others reported so far.展开更多
The factors and mechanisms of oxidative degradation of three organophosphorus pesticides （dichlorvos, methamidophos and phoxim） were studied with sodium percarbonate （SPC） as a solid oxidant. The result showed tha...The factors and mechanisms of oxidative degradation of three organophosphorus pesticides （dichlorvos, methamidophos and phoxim） were studied with sodium percarbonate （SPC） as a solid oxidant. The result showed that SPC has highly activity in degrading these organophosphous pesticides. The most efficient degradation of pesticides occurred under basic conditions and the degradation rates increased with time extension and high temperature. The degradation of organophosphorus pesticides was expected to get even better results at lower initial concentration. Furthermore, we analyzed the intermediate products by NMP, spectrometry. On the basis of the analytical result, the oxidative degradation mechanism was proposed for each organophosphous pesticide. It is significant to understand the environment chemistry of organophosphorus pesticides in environmental system.展开更多
Simulated wastewater of hexahydro-l,3,5-trinitro-l,3,5-triazine （RDX） and octahydro- 1,3,5,7-tetranitro- 1,3,5,7- tetrazocine （HMX） was treated under anaerobic conditions with co-substrates such as ammonium chlori...Simulated wastewater of hexahydro-l,3,5-trinitro-l,3,5-triazine （RDX） and octahydro- 1,3,5,7-tetranitro- 1,3,5,7- tetrazocine （HMX） was treated under anaerobic conditions with co-substrates such as ammonium chloride, dex- trose, sodium acetic, sodium nitrate and sulfate. The results showed that with nitrogen compounds such as ammonium chloride added as co-substrate, no significant change was observed, indicating that the molar ratio of N/C for RDX and HMX is sufficient for biodegradation. With the addition of dextrose and acetate to the system, biodegradation efficiency was enhanced greatly. For example, with dextrose as the co-substrate, degradation efficiency of 99.1% and 98.5% was achieved for RDX and HMX, respectively, after treatment for 7 days. When so- dium acetic was used as the co-substrate, the enhancement of degradation percentage was similar, but was not as high as that with dextrose, indicating the selectivity of RDX and HMX to co-substrate during anaerobic degrada- tion. With sodium nitrate as the co-substrate, the degradation efficiency of RDX or HMX decreased with the increase of salt concentration. Sodium sulfate has no significant effect on the biodegradation of RDX and HMX. A well-selected co-substrate should be employed in applications for degradation of RDX and HMX wastewaters.展开更多
Into the photooxidation process, several factors such as pH, time of irradiation, dose of UV light, lamp power, contaminant concentration, turbidity of the solution and the presence of salts can interfere with the pho...Into the photooxidation process, several factors such as pH, time of irradiation, dose of UV light, lamp power, contaminant concentration, turbidity of the solution and the presence of salts can interfere with the photodegradation of pollutants. This research aims to evaluate the influence of salts： NaCl, MgCl2, CaCI2, BaC12, CuCl2, Na2SO4, MgSO4, MnSO4, FeSO4, CuSO4, Na3PO4, K2CrO4 and K2Cr207 in concentrations of 0.0005 M, 0.005 M and 0.05 M during photodegradation of aqueous solution of 59.5 mg/L of nitrobenzene at a pH of 2.5. It was observed that the presence of salts such as CuCI2, CuSO4, FeSO4, K2CrO4 and K2Cr207 interfere negatively in the system UV/H202 applied for degradation of nitrobenzene; possibly by oxidation of Fe2＋ to Fe3＋ and Cu＋ to Cu2＋ in the Cr case, due to the difficulty of transforming the Cr6＋ to Cr3＋ or because these solutions have color and act as radiation absorbing filter.展开更多
文摘\ According to the analysis of the residual products by thermogravimetric analysis (TGA), the thermal decomposition process of cefazolin sodium (CEZ·Na) was thought to be similar to the degradation in solid state in its storage time. This laid a foundation for estimating the relative chemical stability of the drug by determination of its decomposition kinetics using TGA. Although the observed thermal decomposition kinetics of CEZ·Na was complex, a conversion level of 1% was chosen for evaluation of the stability of CEZ·Na crystalline since the mechanism here was more likely to be that of the actual product failure. The evaluation results suggested that the α form of CEZ·Na had the best stability and the amorphous one was the least stable one among α form, dehydrated α form and amorphous form.
文摘An alginate-degrading bacterium, identified as Ochrobactrum sp. on the basis of 16S rDNA gene sequencing, was isolated from brown algal samples collected from the waters in close vicinity to the Dongtou isles of the East China Sea. The strain, designated WZUH09-1, is able to depolymerize alginates with higher enzyme activity than that of others reported so far.
文摘The factors and mechanisms of oxidative degradation of three organophosphorus pesticides （dichlorvos, methamidophos and phoxim） were studied with sodium percarbonate （SPC） as a solid oxidant. The result showed that SPC has highly activity in degrading these organophosphous pesticides. The most efficient degradation of pesticides occurred under basic conditions and the degradation rates increased with time extension and high temperature. The degradation of organophosphorus pesticides was expected to get even better results at lower initial concentration. Furthermore, we analyzed the intermediate products by NMP, spectrometry. On the basis of the analytical result, the oxidative degradation mechanism was proposed for each organophosphous pesticide. It is significant to understand the environment chemistry of organophosphorus pesticides in environmental system.
基金Supported by the National Natural Science Foundation of China(2117619)Major Project of Innovation of Science and Technology of Shaanxi Province(2011KTZB03-03-01)
文摘Simulated wastewater of hexahydro-l,3,5-trinitro-l,3,5-triazine （RDX） and octahydro- 1,3,5,7-tetranitro- 1,3,5,7- tetrazocine （HMX） was treated under anaerobic conditions with co-substrates such as ammonium chloride, dex- trose, sodium acetic, sodium nitrate and sulfate. The results showed that with nitrogen compounds such as ammonium chloride added as co-substrate, no significant change was observed, indicating that the molar ratio of N/C for RDX and HMX is sufficient for biodegradation. With the addition of dextrose and acetate to the system, biodegradation efficiency was enhanced greatly. For example, with dextrose as the co-substrate, degradation efficiency of 99.1% and 98.5% was achieved for RDX and HMX, respectively, after treatment for 7 days. When so- dium acetic was used as the co-substrate, the enhancement of degradation percentage was similar, but was not as high as that with dextrose, indicating the selectivity of RDX and HMX to co-substrate during anaerobic degrada- tion. With sodium nitrate as the co-substrate, the degradation efficiency of RDX or HMX decreased with the increase of salt concentration. Sodium sulfate has no significant effect on the biodegradation of RDX and HMX. A well-selected co-substrate should be employed in applications for degradation of RDX and HMX wastewaters.
文摘Into the photooxidation process, several factors such as pH, time of irradiation, dose of UV light, lamp power, contaminant concentration, turbidity of the solution and the presence of salts can interfere with the photodegradation of pollutants. This research aims to evaluate the influence of salts： NaCl, MgCl2, CaCI2, BaC12, CuCl2, Na2SO4, MgSO4, MnSO4, FeSO4, CuSO4, Na3PO4, K2CrO4 and K2Cr207 in concentrations of 0.0005 M, 0.005 M and 0.05 M during photodegradation of aqueous solution of 59.5 mg/L of nitrobenzene at a pH of 2.5. It was observed that the presence of salts such as CuCI2, CuSO4, FeSO4, K2CrO4 and K2Cr207 interfere negatively in the system UV/H202 applied for degradation of nitrobenzene; possibly by oxidation of Fe2＋ to Fe3＋ and Cu＋ to Cu2＋ in the Cr case, due to the difficulty of transforming the Cr6＋ to Cr3＋ or because these solutions have color and act as radiation absorbing filter.
