Due to the formation of disinfection by-products and high concentrations of Al residue in drinking water purification, humic substances are a major component of organic matter in natural waters and have therefore rece...Due to the formation of disinfection by-products and high concentrations of Al residue in drinking water purification, humic substances are a major component of organic matter in natural waters and have therefore received a great deal of attention in recent years. We investigated the effects of advanced oxidation pretreatment methods usually applied for removing dissolved organic matters on residual Al control. Results showed that the presence of humic acid increased residual Al concentration notably. With 15 mg/L of humic acid in raw water, the concentrations of soluble aluminum and total aluminum in the treated water were close to the quantity of Al addition. After increasing coagulant dosage from 12 to 120 mg/L, the total-Al in the treated water was controlled to below 0.2 mg/L. Purification systems with ozonation, chlorination, or potassium permanganate oxidation pretreatment units had little effects on residual Al control; while UV radiation decreased Al concentration notably. Combined with ozonation, the effects of UV radiation were enhanced. Optimal dosages were 0.5 mg O 3 /mg C and 3 hr for raw water with 15 mg/L of humic acid. Under UV light radiation, the combined forces or bonds that existed among humic acid molecules were destroyed; adsorption sites increased positively with radiation time, which promoted adsorption of humic acid onto polymeric aluminum and Al（OH） 3 （s）. This work provides a new solution for humic acid coagulation and residual Al control for raw water with humic acid purification.展开更多
In this paper, we described the optimization of the wet oxidation pretreatment conditions to enhance enzymatic hydrolysis efficiency, using poplar waste from the stock section of a paper mill as the raw material. We s...In this paper, we described the optimization of the wet oxidation pretreatment conditions to enhance enzymatic hydrolysis efficiency, using poplar waste from the stock section of a paper mill as the raw material. We showed that the optimal conditions of the pretreatment for poplar waste were an initial p H value of 10, a temperature of 195℃, a holding time of 15 min, and an oxygen pressure of 1.2 MPa. In this case, the yield of the obtained solid material produced by the process was 51.7% and the reducing sugar yield was 46.8%. The solid part obtained from the pretreatment process was hydrolyzed by cellulase L-10. The optimal enzymatic conditions were a temperature of 49℃, a duration time of 56 h, an enzyme dosage of 38 FPU/g at a p H value of 4.8, and a solid-to-liquor ratio of 1∶50. The resulting cellulose conversion rate reached 96.4% in terms of the pretreated substances. In addition, a chemical composition analysis of the poplar waste and pretreated material indicated that about 92% of the hemicelluloses and 43% of the lignin in the raw material were degraded and dissolved. In addition, the crystallization decreased from 57.5% to 54.8%. An obvious fibrillation of the fiber pretreated by the wet oxidization process was observed by SEM. Moreover, high-performance liquid chromatography(HPLC) results showed a high xylose content and monosaccharide degradation products in the pretreatment solution. In conclusion, the wet oxidation pretreatment process could efficiently degrade or remove the lignin and hemicellulose, as well as reduce the crystallinity of the lignocellulosic material, which resulted in animprovement of the enzymatic ability and an increase in the cellulose conversion rate.展开更多
During the acidogenic fermentation converting waste activated sludge (WAS) into shortchain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (su...During the acidogenic fermentation converting waste activated sludge (WAS) into shortchain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (such as antibiotics) during acidogenic fermentation is unknown. In this study, potassium ferrate (KFeO) oxidation was used as a pretreatment strategy for WAS acidogenic fermentation to increase the hydrolysis of sludge and destruct the harmful antibiotics. Pretreatment with KFeOcan effectively increase the SCFA production during acidogenic fermentation and change the distribution of SCFA components.With the dosage of 0.2 g/g TS, the maximum SCFA yield was 4823 mg COD/L, which is 28.3times that of the control group;acetic acid accounts for more than 90% of the total SCFA. The higher dosage (0.5 g/g TS) can further increase the proportion of acetic acid, but inhibit the overall performance of SCFA production. Apart from the promotion of hydrolysis and acidogenesis, KFeOpretreatment can also simultaneously oxidizes and degrades part of the antibiotics in the sludge. When the dosage is 0.5 g/g TS, the degradation efficacy of antibiotics is the most significant, and the contents of ofloxacin, azithromycin, and tetracycline in the sludge are reduced by 69%, 42%, and 50%, respectively. In addition, KFeOpretreatment can also promote the release of antibiotics from sludge flocs, which is conducive to the simultaneous degradation of antibiotics in the subsequent biological treatment process.展开更多
Fresh Pd/CeO/AlOclose coupled catalyst was prepared by the stepwise impregnation method and calcined at 550 °C for 3 h, which was then pretreated at 700, 800, and 900 °C for 3 h, respectively. Finally, these...Fresh Pd/CeO/AlOclose coupled catalyst was prepared by the stepwise impregnation method and calcined at 550 °C for 3 h, which was then pretreated at 700, 800, and 900 °C for 3 h, respectively. Finally, these pretreated catalysts were aged at 1000 °C for 3 h to study their anti-aging properties. The catalytic activities of the catalysts were investigated detailedly, and the results showed that the catalyst pretreated at 800 °C before aging treatment possessed the best anti-aging performance for CHoxidation. XRD and XPS results indicated that well-crystallized CeOparticles were formed during calcinations at 800 °C, which made CeOan effective promoter. HRTEM revealed that Pd particles found on the edge of CeOover the aged catalyst pretreated at 800 °C were relatively smaller than those over the catalysts without pretreatment. H-TPR and XPS results also implied that the interaction between well-crystallized CeOand Pd suppressed the deactivation of PdO sites and further enhanced the catalytic performance.展开更多
To solve the problems generally encountered during the plasma electrolytic oxidation(PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pre...To solve the problems generally encountered during the plasma electrolytic oxidation(PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pretreatment was studied by SEM, EDS and XRD. The pretreatment presents a significant effect on positive voltage at the beginning stage of PEO, leading to higher voltage over the whole process. The difference between the positive voltages of non-etched and etched specimens decreases gradually with the increase of processing time. The pretreatment exhibits much less influence on the negative voltage. For the sample with surface pretreatment, the average growth rate of PEO coating is increased from 0.50 to 0.84 μm·min-1and the energy consumption is decreased from 6.30 to 4.36 k W·h·μm-1·m-2. At the same time, both mullite and amorphous Si O2 contents are decreased in the coating.展开更多
The zinc-containing dust was oxidatively pretreated with calcium hypochlorite,subsequently leached with ammonia/ammonium bicarbonate solution to obtain the ammoniacal leaching solution,and zinc oxide was produced by a...The zinc-containing dust was oxidatively pretreated with calcium hypochlorite,subsequently leached with ammonia/ammonium bicarbonate solution to obtain the ammoniacal leaching solution,and zinc oxide was produced by ammonia distillation of the ammoniacal leaching solution and subsequent calcination. The elements of iron and manganese could not be detected in ammoniacal leaching solution,and the extraction rate of zinc was 98.2% in ammoniacal leaching process. The zinc oxide content in the product is 99.5%(ω),and the contents of iron and manganese in the product were 0.002 8‰ and 0.000 84‰(ω), respectively. The analyses of the valence states of iron and manganese in the zinc-containing dust with and without pretreatment were performed by chemical analysis and XPS,and the possible oxidation mechanism of the oxidative pretreatment of the dust was discussed. It is concluded that Fe 2+-oxide and Mn 2+-oxide in the dust were oxidized to Fe 3+-oxide and/or its hydrate and Mn 4+-oxide and/or its hydrate by calcium hypochlorite during the oxidative pretreatment process,respectively.展开更多
Carbon nanotube fibers(CNTFs)fabricated using a novel“wet-pulling”technique were evaluated for electrochemical detection of dopamine(DA).To enhance the sensitivity,we employed an electrochemical oxidation pretreatme...Carbon nanotube fibers(CNTFs)fabricated using a novel“wet-pulling”technique were evaluated for electrochemical detection of dopamine(DA).To enhance the sensitivity,we employed an electrochemical oxidation pretreatment and twisting of CNTFs and investigated the performance by cyclic voltammetry(CV)and chronoamperometry(CA).The synergetic eff ect of twisting and pre-oxidation boosted the sensitivity of modified CNTFs compared to the as-obtained CNTFs due to the introduction of new active sites for efficient trapping of DA molecules.For the oxidized twisted CNTFs,we achieved a sensitivity of 10.8μA·μM^(–1)·cm^(–2)and the limit of detection of 330 nM in the case of CV,and 6.4μA·μM-1·cm-2and 102 nM in the case of CA,respectively.The CNTFs showed good potential for an in vitro application,maintaining sufficient sensitivity under various conditions.When coupled with the suited mechanical properties of CNTFs,the results highlight the prospect of implantable and flexible sensors.展开更多
Compared with the gas-solid phase reactions,the epoxidation of light olefins in the liquid phase could realize the highly selective preparation of epoxides at a lower temperature.Nevertheless,the C=C bond of light ole...Compared with the gas-solid phase reactions,the epoxidation of light olefins in the liquid phase could realize the highly selective preparation of epoxides at a lower temperature.Nevertheless,the C=C bond of light olefins is more difficult to activate,and it is still a challenge to realize the dual activation of the oxidant and light olefins in one reaction system.In this contribution,an oxametallacycle reinforced nanocomposite(Mo(O_(2))_(2)@RT)is prepared via an oxidative pretreatment strategy,and its epoxidation performance to 2-methylpropene in liquid-phase with tert-butyl hydroperoxide(TBHP)as an oxidant is evaluated.A set of advanced characterizations including field emission scanning electron microscopy,X-ray photoelectron spectroscopy,in-situ Fourier transform infrared spectroscopy(FT-IR),electron spin-resonance spectroscopy,and high-resolution mass spectrometer are implemented to confirm the physicochemical properties and the catalytic behaviors of Mo(O_(2))_(2)@RT.This catalyst has a fast kinetic response and exhibits excellent catalytic activity in 2-methylpropene epoxidation to produce 2-methylpropylene oxide(MPO;select.:99.7%;yield:92%),along with good reusability and scalability.Moreover,the main epoxidation mechanism is deduced that TBHP is activated by Mo(O_(2))_(2)@RT to generate the highly active tert-butyl peroxide radical,which realizes the epoxidation of 2-methylpropene to yield MPO.展开更多
The present research work aims to explore the potency of piranha solutions at the best-optimized concentrations,i.e.,40%and 30%to reduce the recalcitrant and heterogeneous structure of wheat straw,and the treated whea...The present research work aims to explore the potency of piranha solutions at the best-optimized concentrations,i.e.,40%and 30%to reduce the recalcitrant and heterogeneous structure of wheat straw,and the treated wheat straw was denoted as WS40 and WS30.The effect of pretreatment on wheat straw was determined by anaerobic digestion(AD)in a batch mode,followed by the analysis of soluble chemical oxygen demand(sCOD)and volatile fatty acids(VFAs).After pretreatment,the surface fibers shattered and detached,showing a distorted surface of wheat straw.An increase in the crystallinity of wheat straw after pretreatment was also observed due to the removal of amorphous cellulose and lignin.Enhancement in methane yield was obtained on the 9th day,which was 103±6.92 and 99.33±0.57 mL/d for WS40 and WS30,respectively.Displaced water measurement revealed that the pretreatment of wheat straw minimized the hydrolysis period by 14 days.It also improved the methane yield by 2.65(WS40)and 2.45(WS30)fold in comparison with the control which yielded 35.66 mL/d methane on the 23rd day.The modified Gompertz model(MGM),logistic function model(LFM)and transference function model(TFM)adequately described the degradation process and explained the kinetic behavior of the cumulative methane yield.Among the three models,MGM was found to fit best for the methane yield of WS40 and WS30.展开更多
基金supported by the National Natural Science Foundation of China (No. 21007050)the Changjiang Scholars and Innovative Research Team in University (PC-SIRT) (No. IRT0853)the Natural Science Foundation of Shaanxi (No. 2009JQ7001)
文摘Due to the formation of disinfection by-products and high concentrations of Al residue in drinking water purification, humic substances are a major component of organic matter in natural waters and have therefore received a great deal of attention in recent years. We investigated the effects of advanced oxidation pretreatment methods usually applied for removing dissolved organic matters on residual Al control. Results showed that the presence of humic acid increased residual Al concentration notably. With 15 mg/L of humic acid in raw water, the concentrations of soluble aluminum and total aluminum in the treated water were close to the quantity of Al addition. After increasing coagulant dosage from 12 to 120 mg/L, the total-Al in the treated water was controlled to below 0.2 mg/L. Purification systems with ozonation, chlorination, or potassium permanganate oxidation pretreatment units had little effects on residual Al control; while UV radiation decreased Al concentration notably. Combined with ozonation, the effects of UV radiation were enhanced. Optimal dosages were 0.5 mg O 3 /mg C and 3 hr for raw water with 15 mg/L of humic acid. Under UV light radiation, the combined forces or bonds that existed among humic acid molecules were destroyed; adsorption sites increased positively with radiation time, which promoted adsorption of humic acid onto polymeric aluminum and Al（OH） 3 （s）. This work provides a new solution for humic acid coagulation and residual Al control for raw water with humic acid purification.
基金financial support of the Twelfth Five-Year National Science and Technology Support Program(2014BAD02B02)
文摘In this paper, we described the optimization of the wet oxidation pretreatment conditions to enhance enzymatic hydrolysis efficiency, using poplar waste from the stock section of a paper mill as the raw material. We showed that the optimal conditions of the pretreatment for poplar waste were an initial p H value of 10, a temperature of 195℃, a holding time of 15 min, and an oxygen pressure of 1.2 MPa. In this case, the yield of the obtained solid material produced by the process was 51.7% and the reducing sugar yield was 46.8%. The solid part obtained from the pretreatment process was hydrolyzed by cellulase L-10. The optimal enzymatic conditions were a temperature of 49℃, a duration time of 56 h, an enzyme dosage of 38 FPU/g at a p H value of 4.8, and a solid-to-liquor ratio of 1∶50. The resulting cellulose conversion rate reached 96.4% in terms of the pretreated substances. In addition, a chemical composition analysis of the poplar waste and pretreated material indicated that about 92% of the hemicelluloses and 43% of the lignin in the raw material were degraded and dissolved. In addition, the crystallization decreased from 57.5% to 54.8%. An obvious fibrillation of the fiber pretreated by the wet oxidization process was observed by SEM. Moreover, high-performance liquid chromatography(HPLC) results showed a high xylose content and monosaccharide degradation products in the pretreatment solution. In conclusion, the wet oxidation pretreatment process could efficiently degrade or remove the lignin and hemicellulose, as well as reduce the crystallinity of the lignocellulosic material, which resulted in animprovement of the enzymatic ability and an increase in the cellulose conversion rate.
基金supported by the National Natural Science Foundation of China (No. 51978595)。
文摘During the acidogenic fermentation converting waste activated sludge (WAS) into shortchain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (such as antibiotics) during acidogenic fermentation is unknown. In this study, potassium ferrate (KFeO) oxidation was used as a pretreatment strategy for WAS acidogenic fermentation to increase the hydrolysis of sludge and destruct the harmful antibiotics. Pretreatment with KFeOcan effectively increase the SCFA production during acidogenic fermentation and change the distribution of SCFA components.With the dosage of 0.2 g/g TS, the maximum SCFA yield was 4823 mg COD/L, which is 28.3times that of the control group;acetic acid accounts for more than 90% of the total SCFA. The higher dosage (0.5 g/g TS) can further increase the proportion of acetic acid, but inhibit the overall performance of SCFA production. Apart from the promotion of hydrolysis and acidogenesis, KFeOpretreatment can also simultaneously oxidizes and degrades part of the antibiotics in the sludge. When the dosage is 0.5 g/g TS, the degradation efficacy of antibiotics is the most significant, and the contents of ofloxacin, azithromycin, and tetracycline in the sludge are reduced by 69%, 42%, and 50%, respectively. In addition, KFeOpretreatment can also promote the release of antibiotics from sludge flocs, which is conducive to the simultaneous degradation of antibiotics in the subsequent biological treatment process.
基金Project supported by the National Natural Science Foundation of China(21173153)the National Hi-tech Research Development Program of China(863 Program,2013AA065304)the Sichuan Science and Technology Agency Supported Project(2012FZ0008)
文摘Fresh Pd/CeO/AlOclose coupled catalyst was prepared by the stepwise impregnation method and calcined at 550 °C for 3 h, which was then pretreated at 700, 800, and 900 °C for 3 h, respectively. Finally, these pretreated catalysts were aged at 1000 °C for 3 h to study their anti-aging properties. The catalytic activities of the catalysts were investigated detailedly, and the results showed that the catalyst pretreated at 800 °C before aging treatment possessed the best anti-aging performance for CHoxidation. XRD and XPS results indicated that well-crystallized CeOparticles were formed during calcinations at 800 °C, which made CeOan effective promoter. HRTEM revealed that Pd particles found on the edge of CeOover the aged catalyst pretreated at 800 °C were relatively smaller than those over the catalysts without pretreatment. H-TPR and XPS results also implied that the interaction between well-crystallized CeOand Pd suppressed the deactivation of PdO sites and further enhanced the catalytic performance.
基金Supported by the Natural Science Foundation of Guangdong Province,China(S2013010015211)
文摘To solve the problems generally encountered during the plasma electrolytic oxidation(PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pretreatment was studied by SEM, EDS and XRD. The pretreatment presents a significant effect on positive voltage at the beginning stage of PEO, leading to higher voltage over the whole process. The difference between the positive voltages of non-etched and etched specimens decreases gradually with the increase of processing time. The pretreatment exhibits much less influence on the negative voltage. For the sample with surface pretreatment, the average growth rate of PEO coating is increased from 0.50 to 0.84 μm·min-1and the energy consumption is decreased from 6.30 to 4.36 k W·h·μm-1·m-2. At the same time, both mullite and amorphous Si O2 contents are decreased in the coating.
基金Supported by the National Basic Research Program of China(973)(No.2007CB613601)Supported by the National Natural Science Foundationof China(No.51134007)Supported by the Science&Technology Plan of Hunan Province(No.2011FJ6005)
文摘The zinc-containing dust was oxidatively pretreated with calcium hypochlorite,subsequently leached with ammonia/ammonium bicarbonate solution to obtain the ammoniacal leaching solution,and zinc oxide was produced by ammonia distillation of the ammoniacal leaching solution and subsequent calcination. The elements of iron and manganese could not be detected in ammoniacal leaching solution,and the extraction rate of zinc was 98.2% in ammoniacal leaching process. The zinc oxide content in the product is 99.5%(ω),and the contents of iron and manganese in the product were 0.002 8‰ and 0.000 84‰(ω), respectively. The analyses of the valence states of iron and manganese in the zinc-containing dust with and without pretreatment were performed by chemical analysis and XPS,and the possible oxidation mechanism of the oxidative pretreatment of the dust was discussed. It is concluded that Fe 2+-oxide and Mn 2+-oxide in the dust were oxidized to Fe 3+-oxide and/or its hydrate and Mn 4+-oxide and/or its hydrate by calcium hypochlorite during the oxidative pretreatment process,respectively.
基金supported by Russian Science Foundation,21-73-10288Ministry of Science and Higher Education of the Russian Federation,FZSR-2024-0005。
文摘Carbon nanotube fibers(CNTFs)fabricated using a novel“wet-pulling”technique were evaluated for electrochemical detection of dopamine(DA).To enhance the sensitivity,we employed an electrochemical oxidation pretreatment and twisting of CNTFs and investigated the performance by cyclic voltammetry(CV)and chronoamperometry(CA).The synergetic eff ect of twisting and pre-oxidation boosted the sensitivity of modified CNTFs compared to the as-obtained CNTFs due to the introduction of new active sites for efficient trapping of DA molecules.For the oxidized twisted CNTFs,we achieved a sensitivity of 10.8μA·μM^(–1)·cm^(–2)and the limit of detection of 330 nM in the case of CV,and 6.4μA·μM-1·cm-2and 102 nM in the case of CA,respectively.The CNTFs showed good potential for an in vitro application,maintaining sufficient sensitivity under various conditions.When coupled with the suited mechanical properties of CNTFs,the results highlight the prospect of implantable and flexible sensors.
基金This work was financially supported by the National Key Research and Development Program Nanotechnology Specific Project(No.2020YFA0210900)the National Natural Science Foundation of China(Nos.21908256,21938001,and 21878344)+1 种基金Guangdong Provincial Key R&D Program(No.2019B110206002)the Fundamental Research Funds for the Central Universities,Sun Yatsen University(No.2021qntd13).
文摘Compared with the gas-solid phase reactions,the epoxidation of light olefins in the liquid phase could realize the highly selective preparation of epoxides at a lower temperature.Nevertheless,the C=C bond of light olefins is more difficult to activate,and it is still a challenge to realize the dual activation of the oxidant and light olefins in one reaction system.In this contribution,an oxametallacycle reinforced nanocomposite(Mo(O_(2))_(2)@RT)is prepared via an oxidative pretreatment strategy,and its epoxidation performance to 2-methylpropene in liquid-phase with tert-butyl hydroperoxide(TBHP)as an oxidant is evaluated.A set of advanced characterizations including field emission scanning electron microscopy,X-ray photoelectron spectroscopy,in-situ Fourier transform infrared spectroscopy(FT-IR),electron spin-resonance spectroscopy,and high-resolution mass spectrometer are implemented to confirm the physicochemical properties and the catalytic behaviors of Mo(O_(2))_(2)@RT.This catalyst has a fast kinetic response and exhibits excellent catalytic activity in 2-methylpropene epoxidation to produce 2-methylpropylene oxide(MPO;select.:99.7%;yield:92%),along with good reusability and scalability.Moreover,the main epoxidation mechanism is deduced that TBHP is activated by Mo(O_(2))_(2)@RT to generate the highly active tert-butyl peroxide radical,which realizes the epoxidation of 2-methylpropene to yield MPO.
基金the financial support received from University Grant Commission(UGC),New Delhi,in the form of National Fellowship for Scheduled Caste Students(UGC-Ref.No.200510367941)。
文摘The present research work aims to explore the potency of piranha solutions at the best-optimized concentrations,i.e.,40%and 30%to reduce the recalcitrant and heterogeneous structure of wheat straw,and the treated wheat straw was denoted as WS40 and WS30.The effect of pretreatment on wheat straw was determined by anaerobic digestion(AD)in a batch mode,followed by the analysis of soluble chemical oxygen demand(sCOD)and volatile fatty acids(VFAs).After pretreatment,the surface fibers shattered and detached,showing a distorted surface of wheat straw.An increase in the crystallinity of wheat straw after pretreatment was also observed due to the removal of amorphous cellulose and lignin.Enhancement in methane yield was obtained on the 9th day,which was 103±6.92 and 99.33±0.57 mL/d for WS40 and WS30,respectively.Displaced water measurement revealed that the pretreatment of wheat straw minimized the hydrolysis period by 14 days.It also improved the methane yield by 2.65(WS40)and 2.45(WS30)fold in comparison with the control which yielded 35.66 mL/d methane on the 23rd day.The modified Gompertz model(MGM),logistic function model(LFM)and transference function model(TFM)adequately described the degradation process and explained the kinetic behavior of the cumulative methane yield.Among the three models,MGM was found to fit best for the methane yield of WS40 and WS30.
