Investigation on the rapid degradation of congo red
Journal of Hazardous Materials 147(2007)
325–333
Investigation on the rapid degradation of congo red catalyzed by activated
carbon powder under microwave irradiation
Zhaohong Zhang a ,?,Yabo Shan a ,Jun Wang b ,Hongjie Ling a ,Shuliang Zang b ,
Wei Gao a ,Zhe Zhao a ,Huachun Zhang a
a
Department of Environment Science,Liaoning University,Shengyang 110036,PR China
b Department of Chemistry,Liaoning University,Shengyang 110036,PR China
Received 22July 2006;received in revised form 22November 2006;accepted 31December 2006
Available online 12January 2007
Abstract
Azo dyestuff-congo red in aqueous solution can be degraded rapidly under microwave irradiation in the presence of activated carbon powder.The results showed that the degradation ratio could reach 87.79%for 25mL total volume with 50mg/L congo red and 2.0g/L activated carbon powder under 1.5min microwave irradiation.Furthermore,within the same irradiation time,congo red could be degraded fully by increasing addition amount (e.g.3.6g/L)of activated carbon powder and the degradation ratio was up to 96.49%.Otherwise,with the same addition amount,congo red also could be degraded completely by prolonging irradiation time (e.g.2.5min)and the degradation ratio was up to 97.88%.In addition,the in?uences of microwave irradiation time,initial concentration of congo red,addition amount and used times of activated carbon powder as well as solution acidity on the degradation were discussed in details adopting UV–vis spectra,FT-IR spectra,ion chromatography,high phase liquid chromatography (HPLC)and TOC analysis technologies.Here,the method using activated carbon powder as catalyst under microwave irradiation shows many advantages including high degradation ratios,short reaction time,low costs,no intermediates and no secondary pollution.Therefore,it may be ?t for dealing with various azo dyestuff wastewaters on a large scale.?2007Elsevier B.V .All rights reserved.
Keywords:Activated carbon powder;Microwave irradiation;Rapid degradation;Congo red
1.Introduction
In general,the treatment of various dye wastewaters has been regarded to be one of the main aims in controlling environmen-tal pollution all over the world [1,2].Since most of organic dye compounds ordinarily contain benzene and naphthalene rings,they cannot be decomposed easily by conventional biological and chemical methods [3–7].In particular,as well known,ear-lier studies showed that the biological method was carried out under the strict conditions [8,9].And as one of popular chem-ical methods,the photocatalytic degradation generally needs long irradiation time and displays halfway degradation [10,11].Furthermore,sometimes some intermediates such as benzene and aniline derivatives,which are considered to be mutagen,mitotic poisons and suspected carcinogens,may form during
?
Corresponding author.Tel.:+862462205173;fax:+862462202380.E-mail addresses:zzhlyl@https://www.sodocs.net/doc/098971182.html, ,lnuhjhx@https://www.sodocs.net/doc/098971182.html, (Z.Zhang).
degradation process of the organic pollutants in dye wastewater [12,13].Therefore,it is urgent to seek for the novel tech-nologies to degrade various organic pollutants effectively and completely.
Recent years,there have been some reports with respect to wastewater treatment using microwave-assisted approaches.For example,the wet air oxidation on the activated carbon under microwave irradiation was used in treating phenolic wastewater [14];the continuous ?ow mode on the activated carbon ?xed bed was used for microwave-assisted degradation of concen-trated p -nitrophenol [15];the microwave irradiation was used for enhancing a series of advanced oxidation processes in the degradation of 4-chlorophenol [16].Hence,the application of microwave technology has been attached more and more impor-tance to treating environmental pollutants.
The frequency range of microwave,a kind of electromag-netic wave,is from 300MHz to 300GHz,that is,the wavelength lies between 1.0mm and 1.0m.And it has very strong pene-trating ability in many media.The microwave irradiation can
0304-3894/$–see front matter ?2007Elsevier B.V .All rights reserved.doi:10.1016/j.jhazmat.2006.12.083
326Z.Zhang et al./Journal of Hazardous Materials147(2007)325–333
make the polar molecules in solution rotate?eetly,which brings obvious heat effects.At the same time,it can further change the thermodynamics function and reduce the activation energy of the reaction system,and weaken the chemical bond inten-sities of various molecules[17].Moreover,the existence of microwave absorbent can increase these effects.Therefore,the technology of microwave irradiation integrated with some suit-able microwave absorbents as catalysts should be even more suitable for treating dye wastewaters.
As well known,the role of the activated carbon powder may be demonstrated in two aspects,namely,adsorbent and microwave absorbent[18–20].As adsorbent the activated car-bon powder can remove many organic and inorganic pollutants from solution.As microwave absorbent,the activated carbon powder can strongly absorb microwave energy.Due to the non-uniformity,the“hot spots”on the surface of activated carbon particles may be generated,where the temperatures are out and away higher than those of other positions,and chemical reactions may take place easily.
In this study,the microwave technology reported previously was improved and simplied,and a rapid and simple method treat-ing dye wastewater was presented.Here,the azo dyestuff-congo red,because of representability and easy monitoring,as a model compound under microwave irradiation in the presence of acti-vated carbon powder as microwave absorbent was investigated in details.The in?uences of irradiation time,initial concentration of congo red,the addition amount of activated carbon powder and solution acidity on the degradation were discussed,respec-tively.This technology revealed many advantages such as high degradation ratio,short irradiation time,simple equipments,low costs,no intermediates and no secondary-pollution,so the good and extensive application foregrounds were revealed.
2.Experimental
2.1.Materials
Congo red(Analysis purity,Shanghai Chemistry Reagent Corporation,China)was purchased,and its structure is shown in Plate1.The granular activated carbon(GAC)(Liaoning Med-ical Company,China)was used as a catalyst.It was made from coal,with ash content3–5%,particle size2–3mm,surface area 1300m2/g and average pore diameter2–3nm.Water puri?ed by a Milli-Q water system(Millipore Company,USA)was used throughout the experiment.2.2.Apparatus
Cary-50UV–vis spectrometer(Varian Company,USA),ICS-90ion chromatography apparatus(Dionex Company,USA), Pro-210high phase liquid chromatography(HPLC)apparatus (Varian Company,USA),Nicolet Avatar330Fourier trans-form infrared(FT-IR)spectrometer(Nicolet Company,USA) and Liqui TOC apparatus(Elementar Analysensysteme GmbH Company,Germany)were used to inspect the degradation pro-cesses of congo red.G8023ESL-V8controllable microwave oven(Guangdong Galanz Company,China)was adopted to irradiate the congo red solutions,operating at microwave fre-quency of2450MHz and output power of800W.pHS-3C pH meter(Shanghai Leici Company,China)was used to determine acidities of the congo red solutions.
2.3.Pretreatment of activated carbon powder
For high catalytic activity,?rstly,GAC were properly tritu-rated and sifted out using100mesh sieve,and then the powdery activated carbon(PAC)was obtained.10.00g activated carbon powder was weighted and put into100mL deionized water,then, boiled for30min.After cooling to the room temperature,the activated carbon powder was?ltered out.This operation proce-dure was repeated three times.Afterwards,the activated carbon powder was dried at105?C for about6.0h to constant weight and stored in a desiccator for use.It is noticeable that the gran-ularity of activated carbon powder should not be excessively small for easy separation and high catalytic activity.
2.4.Experimental method
The25mL prepared congo red solution(50mg/L)and treated activated carbon powder(2.0g/L)were put into a self-made glass reactor.As shown in Plate2,in order to prevent volatilization of the solvent a condenser was jointed on the glass reactor.After-wards,the apparatus was installed in the microwave oven.The pH value of the suspension was adjusted to8.0.The microwave was utilized to irradiate this suspension.After1.5min,the UV–vis spectra of?ltered congo red solution(diluted by?ve times)were determined in the wavelength range from190to 800nm.In order to compare the degradation effects,the UV–vis spectra of the treated congo red solutions by one-fold microwave irradiation and one-fold activated carbon powder,respectively, were also given in Fig.1.The maximal absorbencies of 0–40mg/L congo red solutions abide by Lambert-Beer’s
law. Plate1.Structure of congo red molecule.
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327
Plate 2.Schematic illustration of experimental apparatus:(1)microwave gener-ator;(2)reaction solution;(3)activated carbon powder;(4)condenser;(5)time display;(6)time adjuster;(7)power adjuster.
The calibration curve (A =0.04022C (mg/L),R 2=0.9961)of standard congo red solution was used to estimate the degradation ratio.The degradation ratio was calculated by the follow-ing equation:degradation ratio (%)=[(C 0?C t )/C 0]×100%,where C 0represents the initial concentration,C t represents the instant concentration.Table 1gives the reduction ratios (%)of the absorption peaks of congo red solution at different character-istic wavelength.The degradation ratio of congo red at intervals of 0.5min within 2.5min was shown in Fig.2.The relation of ?ln(C t /C 0)and irradiation time (t )was shown in Fig.3,which can infer the kinetics of degradation reaction.
For further validating degradation of congo red in aqueous solution,the ionic chromatogram and HPLC were determined as shown in Figs.4and 5,respectively.During determination of ionic chromatogram,the initial concentration of 50mg/L congo red and irradiation time of 0.5,1.5and 2.5min
were
Fig. 1.UV–vis spectra of congo red solution under different conditions:(a)original solution;(b)one-fold microwave;(c)activated carbon;(d)microwave +activated carbon.
Table 1
Reduction ratio (%)of various absorption peaks of congo red a Reduction ratio (%)
A (499nm)
B (345nm)
C (236nm)Average (%)
Original solution (a)0000One-fold microwave (b) 2.92 2.65 2.31 2.63Activated carbon (c)26.5626.4928.3827.14Microwave +activated carbon (d)
89.1587.42
86.79
87.79
a
For microwave irradiation the reduction ratio is equal to degradation ratio;for activated carbon the reduction ratio is equal to adsorption
ratio.
Fig.2.In?uence of irradiation time on degradation ratio:( )microwave +activated carbon (499nm);( )microwave +activated carbon (345nm);( )microwave +activated carbon (237nm);(?)one-fold activated carbon (499nm);( )one-fold microwave (499nm).
adopted.The other conditions were as follows:AS9-HC column (250mm ×4mm i.d.),9.0mmol/L NaCO 3eluent,1.0mL/min ?ow rate and conductivity detector.For the determination of HPLC,the initial concentration of 200mg/L and irradiation
time
Fig. 3.Kinetics of degradation reaction of congo red (at 499nm):( )microwave +activated carbon;(?)only activated carbon;( )only microwave.
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325–333
Fig.4.Ion chromatogram of congo red solution during degradation:(a)0.5min;(b)1.5min;(c)2.5min.
of 1.0,2.0and 3.0min were adopted.The other conditions were as follows:C18(250mm ×4.6mm i.d.)reverse phase column,0.3:0.7–1.0:0.0proportion of ethanol and water,1.0mL/min ?ow rate and UV detector (at 236nm wavelength).Otherwise,total organic carbon (TOC)values of treated solution were also determined.For 50mg/L congo red solution,the irradiation time of 1.5and 2.5min were adopted.The carrier gas was oxygen of 0.95–1.00bar.The other conditions were as follows:max temperature 850?C,200mL/min ?ow rate and IR detector.The in?uences of the initial concentrations (10–90mg/L)of congo red solution,addition amounts (0–3.6g/L)of activated carbon powder,and initial pH (4.0–12.0)of the solution on the degradation were reviewed,respectively,in this work.These results were showed in Figs.7–9,respectively.In addition,in order to validate that all congo red in aqueous solution were degraded under microwave irradiation catalyzed by activated carbon powder,FT-IR spectra of used activated carbon powder
were determined in the wavelength range from 400to 4000cm ?1as shown in Fig.6.For comparison,the FT-IR spectrum of the original congo red was also given in Fig.6.At last,for reviewing the catalytic activities of reused activated carbon powder the degradation of congo red within 1.5min irradiation were also investigated and the results were shown in Fig.10.All con?rmed conditions were used throughout experiment if there was not special demonstration.3.Results and discussion
3.1.UV–vis spectra of congo red solution during degradation
Fig.1shows that the congo red solution gives three absorption peaks at 499nm (A ),345nm (B )and 236nm (C ),respectively,in UV–vis spectra.At the beginning,it could be found that all absorption peaks went down slightly even under one-fold microwave irradiation in the absence of any catalyst,which indi-cated that only a little of congo red could be degraded.And when one-fold activated carbon powder existed,all absorption peaks also went down to a certain extent synchronously.It indi-cated that the activated carbon powder could adsorb some congo red dyes in a way,but the most still left over in the solution except adsorbed congo red.Nevertheless,all absorption peaks of congo red solution fell to a large extent with a bit shift under microwave irradiation in the presence of activated carbon pow-der.It could also be seen from Fig.1that the reduction ratio of absorption peak (C )belonging to the naphthalene rings of congo red was only 2.31%within 1.5min microwave irradi-ation,which meaned that it was dif?cult for the naphthalene rings to degrade only under microwave irradiation without any catalyst.However,the reduction ratio of absorption peak (C )could reach 86.79%in the presence of activated carbon powder under microwave irradiation within the same irradiation time.So great reduction ratio indicated that the naphthalene rings of congo red could be degraded easily in the presence of activated carbon powder under microwave
irradiation.
Fig.5.HPLC of congo red solution during degradation (at 236nm):(a)1.0min;(b)2.0min;(c)3.0min.
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Fig.6.FT-IR spectra of congo red at different conditions:(a)original congo red;(b)congo red adsorbed on activated carbon;(c)3.0min microwave irradiation;(d) 5.0min microwave irradiation.
All results reveal that the activated carbon powder has obvious catalytic activity for degradation of congo red under microwave irradiation.Hence,it is known that the activated carbon powder mainly displays strong catalytic activity under microwave radiation except its adsorption ability.The research results show the degradation process in the presence of activated carbon powder with microwave irradiation is different from that of photocatalytic degradation through?OH radical[21,22].On the one hand,in general,the photocatalytic degradation needs long irradiation time,while the microwave degradation with acti-vated carbon powder occurs rapidly,and it needs only several minutes.On the other hand,a number of intermediate products were usually formed during photocatalytic degradation.Con-trarily,there are few intermediate products under microwave radiation in the presence of activated carbon powder.It indi-cates that whole congo red molecule can burn adequately and then be eliminated thoroughly from solution once it touches the “hot spots”on the surface of activated carbon particles.
3.2.In?uence of irradiation time on degradation ratio and reaction kinetics
As shown in Fig.2,the change of degradation ratio with irradiation time was reviewed for25mL suspension of50mg/L congo red and2.0g/L activated carbon powder.The case under one-fold microwave irradiation was also considered.It could be observed that the degradation ratio increased rapidly with increasing irradiation time in the presence of activated carbon powder.And the degradation ratios calculated based on three absorption peaks(A,B and C)reached97.88%,95.55%and 92.90%,respectively,under2.5min microwave irradiation.It could be known that,under such conditions,the congo red was degraded remarkably.Nevertheless,for one-fold microwave irradiation the average degradation ratio corresponding to three absorption peaks(A,B and C)was only3.70%.Of course,the activated carbon powder can adsorb a part of congo red from solution too,but the saturated adsorption ratio was not higher than27.20%.As shown in Table1,the degradation ratio under microwave irradiation in the presence of activated carbon pow-der was much higher than the sum of degradation ratio from one-fold microwave irradiation and the adsorption ratio from one-fold activated carbon powder.These results indicate that the reduction of congo red mainly results from the combined function of microwave irradiation and activated carbon powder, but not a simple addition of both.
The studies on the reaction kinetics of three courses were also carried out and the results were shown in Fig.3.It was found that the degradation reaction of congo red under microwave irradiation in the presence of activated carbon pow-der basically belonged to?rst-order reaction kinetics.Its rate constant(1.5138min?1)was far beyond those(0.1213and 0.0296min?1)corresponding to the degradation reaction of one-fold microwave irradiation and the adsorption process of one-fold activated carbon powder,respectively,which also belonged to?rst-order reaction kinetics.
In addition,the calculated reduction ratios according to the determination of TOC values were73.71%and86.13%,respec-tively,under1.5and2.5min microwave irradiation.These results also demonstrated that the congo red in the treated solu-tion could mostly be degraded under microwave irradiation in the presence of activated carbon powder.
3.3.Ionic chromatogram and HPLC of congo red solution during degradation
In order to con?rm the degradation extent of congo red and the formation of intermediate products during degradation,the ionic chromatogram and HPLC were also determined,respec-tively,at different irradiation time.The results were shown in Figs.4and5,respectively.It could be observed in Fig.4that the ionic chromatographic peaks corresponding to NO3?and SO42?anions gradually increased along with microwave irradi-ation,while the peak corresponding to NO2?anion continually decreased.All of these results indicated that the C S,C N and
330Z.Zhang et al./Journal of Hazardous Materials147(2007)325–333
azo bonds in the congo red molecule were destroyed gradually. The sulfur and nitrogen atoms were oxidized and transferred into NO2?,NO3?and SO42?anions,respectively,but the NO2?anion?nally was oxidized to the NO3?anion.This was the rea-son why the peak corresponding to NO2?anion decreased.By all means,the congo red in aqueous solution could be mineral-ized to a series of simple and innocuous inorganic ions in the end under microwave irradiation in the presence of activated carbon powder.
Additionally,it was showed in Fig.5that the matrix peak of the congo red molecule at10.847min retention time min-ished little by little with microwave irradiation.It meaned the naphthalene rings of congo red were destroyed by degrees, and then disappeared at last.Otherwise,a new peak appeared at12.257min retention time under1.0min microwave irra-diation,which indicated a small quantity of intermediate products formed.But it disappeared immediately under3.0min microwave irradiation.The results demonstrated that the congo red and its intermediate products in aqueous solution could be degraded thoroughly after3.0min microwave irradiation in the presence of activated carbon powder,though intermediate prod-ucts once formed during the degradation.
3.4.FT-IR spectra of congo red on the surface of activated carbon powder
To review the degradation behave of congo red on the sur-face of activated carbon particles,the FT-IR spectra of the used activated carbon powder was determined as shown in Fig.6.It could be seen clearly that some characteristic absorption peaks of congo red appeared in Fig.6b,which indicated that a mass of congo red was adsorbed on the surface of activated carbon particles.According to the decrease of characteristic absorption peaks in Fig.6c,it was known that the amount of congo red adsorbed on the surface of activated carbon particles reduced under3.0min microwave irradiation.After5.0min,the char-acteristic absorption peaks of congo red disappeared almost in Fig.6d,which indicated that most of congo red dyes on the surface of activated carbon were degraded or desorbed.Based on the analysis of UV–vis spectra and TOC values mentioned above,not only the congo red dyes adsorbed on the surface of activated carbon were degraded under microwave irradiation,but also those in the solution were done.Perhaps,the congo red in the solutions may?rstly be adsorbed on the surface of activated carbon particles,and then,they are immediately degraded under microwave irradiation.And it cannot only rest on the adsorbed stage.
3.5.In?uence of initial concentration on the degradation ratio
A series of congo red solutions with different initial con-centrations ranging from10to90mg/L were used for studying the in?uence on the degradation ratio within1.5min microwave irradiation.As shown in Fig.7,the degradation ratio under microwave irradiation in presence of activated carbon powder maintained above96%before30mg/L concentration.And
then Fig.7.In?uence of initial concentration of congo red on degradation ratio(at 499nm):( )microwave+activated carbon;(?)one-fold activated carbon;( ) one-fold microwave.
it decreased gradually with increasing concentration.However, the adsorption ratio in the presence of one-fold activated car-bon powder decreased all through.It means that the adsorption ability of activated carbon powder is limited for congo red. Otherwise,for one-fold microwave irradiation the degradation ratio of congo red was very low throughout the experimental concentration range.
These results revealed that the elimination effects under microwave irradiation in presence of activated carbon powder were much better than those of both one-fold microwave irra-diation and one-fold activated carbon powder.It was proved again that the degradation of congo red mainly resulted from the combined action of microwave irradiation and activated carbon powder,but not a simple addition of the degradation of one-fold microwave irradiation and the adsorption of one-fold activated carbon.In addition,for high concentrated congo red solution (above50mg/L)the activated carbon powder also exhibited rel-atively high catalytic activity under microwave irradiation.Only when the concentration of congo red increased continuously, the catalytic activity of activated carbon powder decreased a lit-tle.Of course,it was obvious that the low initial concentration was bene?t for degradation of congo red.For a large number of congo red molecules the catalytic degradation ability of activated carbon powder became relatively low.
3.6.In?uence of addition amount of activated carbon powder on the degradation ratio
In general,the addition amount of catalyst is a very impor-tant parameter in treating wastewater for both photocatalytic and sonocatalytic degradations[23–25].Similarly,in order to opti-mize the addition amount of activated carbon powder as catalyst for high degradation ratio,the in?uences of different addition amount from0.4to3.6g/L were also considered.As shown in Fig.8,the degradation ratio of congo red showed a rapid increas-ing trend before addition amount of2.0g/L activated carbon powder,and then went up slowly.This phenomenon could be explained as the mutual screen among activated carbon particles for high addition amount.The degradation ratio could be up to 96.49%for3.6g/L addition amount of activated carbon under
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331
Fig.8.In?uence of addition amount of activated carbon powder on degrada-tion ratio (at 499nm):( )microwave +activated carbon;(?)one-fold activated carbon.
1.5min microwave irradiation.It could also be seen that the adsorption ratio became high with increasing addition amount of activated carbon powder,but the increasing extent was small and it was only 35.66%.The above results testi?ed again that the decrease of congo red in aqueous solution was mainly owing to the degradation under microwave irradiation in the presence of activated carbon powder.
3.7.In?uence of acidity on the degradation ratio
The in?uences of acidities on the degradation of congo red were studied in the range between pH 4.0and pH 12.0.The results were shown in Fig.9.It was found that the degrada-tion ratio of congo red under 1.5min microwave irradiation in the presence of activated carbon powder changed scarcely and maintained a high level from pH 4.0to pH 8.0,and then fell slightly after pH 8.0.Afterwards,it began to go up some-what after pH 10.0again.The similar change regulars were also observed for the adsorption of one-fold activated carbon powder and the degradation of one-fold microwave irradiation.In any case,the degradation ratio of congo red under microwave
irradi-
Fig.9.In?uence of pH value on degradation ratio (at 499nm):( )microwave +activated carbon;(?)one-fold activated carbon;( )one-fold
microwave.
Fig.10.In?uence of reused times on degradation ratio (at 499nm).
ation in the presence of activated carbon powder was obviously higher than the adsorption ratio of one-fold activated carbon and degradation ratio of one-fold microwave irradiation.
In general,the acidity can in?uence the distribution and quan-tity of the charges on the surface of activated carbon particles.When the pH value is lower than isoelectric point (pH 6.38)of activated carbon,its surface is positively charged,whereas its surface is negatively charged when the pH values is higher than the isoelectric point.The congo red molecule with two sul-fonic groups ionizes easily even though in strong acidic solution and then becomes a soluble congo red anion.Therefore,in the acidic and neutral solution the congo red anions are close to the surface of activated carbon particles or adsorbed on it with posi-tive charges.These congo red anions can be oxidized directly by oxygen in aqueous solution under microwave irradiation.Hence,before pH 8.0,the results exhibited a high degradation ratio of congo red.However,at higher pH values the congo red anions were generally excluded away from the charged negatively sur-face of activated carbon particles,so the degradation ratio began to decrease.Furthermore,the reason that the degradation ratio increased slightly in alkali solution may be the occurrence of partial radical oxidation degradation.This is because a num-ber of OH ?anions loss their electrons at high temperature and transfer into ?OH radicals which also have strong oxidation abil-ity.Because the degradation ratio relates to the pH values in solution,the treatment of some organic pollutants like congo red dye should be carried out in the acidic or neutral solution under microwave irradiation in the presence of activated carbon powder.
3.8.In?uence of used times of activated carbon powder on the degradation ratio
As known to all,the important one for any catalyst is recycle.Here,the catalytic activities of reused activated carbon powder were also studied.It was found that the used activated car-bon powder could be separated easily from the treated solution.The used activated carbon powder was washed out and rehan-dled adopting the pretreating method in experiment part,and then reused in the new experiments with fresh congo red solu-tion.As shown in Fig.10,comparing with the new activated
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Fig.11.Possible principle of degradation on the surface of activated carbon on ratio.
carbon powder,the catalytic activity of used activated carbon powder became low gradually along with used times.Although the declined extents became smaller and smaller after several times and maintained a stable level,the catalytic activity wholly decreased about50%comparing with the new one.It was indi-cated that the activated carbon itself could also be destroyed synchronously to a certain extent during degradation of organic pollutants under microwave irradiation.This process results in the catalytic activities of reused activated carbon powder going down considerably.Although a great number of organic pollu-tants can be effectively mineralized under microwave irradiation with activated carbon powder,the reclamation and reuse of it are still an urgently solved problem for widely adopting this method in practical application.
3.9.Principle on microwave degradation of congo red
In present,there are two popular points of view on the fact that the microwave irradiation can accelerate the elimination of organic pollutants in the presence of activated carbon,that is, microwave-assisted oxidation and microwave-assisted adsorp-tion.Although the investigation on the microwave degradation in the presence of activated carbon powder has not been reported too much yet,based on our studies we are inclined to the for-mer.It was thought that the mechanism or process of microwave degradation of organic pollutants in the presence of activated carbon powder should be explained as the formation of“hot spots”and oxidation combustion of organic pollutants.As shown in Fig.11,when the activated carbon particles as microwave absorbent are irradiated by microwave,their uneven surfaces will absorb these microwave energies,and a lot of“hot spots”form synchronically.The temperature of these“hot spots”can ordi-narily reach1200?C above.Due to the functions of both thermal and non-thermal effects,not only the azo bonds of congo red can be destroyed completely but also the naphthalene rings of it can be degraded rapidly.According to the determination of TOC, it is considered that this process is almost equal to oxidation combustion of organic pollutants.CO2and H2O are given out and various simple inorganic ions are also produced,so that the congo red as well as intermediate products in aqueous solution are degraded fully at last.
4.Conclusion
When the treated activated carbon powders are adopted as cat-alyst and the microwave is used as irradiation source,the organic pollutants like congo red in aqueous solutions can be degraded rapidly and totally.In present work,the congo red as a model compound was?rstly degraded adopting the technology of microwave irradiation integrated with activated carbon powder. For a high degradation ratio of congo red the optimized con-ditions were considered to be initial concentration of50mg/L congo red,addition amount of2.0g/L activated carbon powder, microwave irradiation of800W output power and2450kHz fre-quency and pH8.0.Under such conditions,the degradation ratio could reach89.15%for25mL congo red solution within1.5min. In addition,the degradation ratios reached96.49%and97.88%, respectively,by appropriately increasing addition amount(e.g.
3.6g/L)of activated carbon powder and prolonging irradiation time(e.g.2.5min).Furthermore,the intermediate products in the treated solution were not found through HPLC in the end.Oth-erwise,the activated carbon powder as catalyst could be reused through simple treatment.Thus,as a novel technology treat-ing dyestuff wastewaters,the method of microwave irradiation with activated carbon powder adopted as catalyst reveals many advantages,such as complete and rapid degradation,low cost, no intermediate products,no secondary pollution,and so on. Maybe,it is?t for treating those wastewaters containing concen-trated azo dyes.In conclusion,the research results demonstrate the feasibilities treating dye wastewaters adopting the method combining microwave radiation with activated carbon catalyst in the future.
Acknowledgements
The authors greatly acknowledge The National Natural Sci-ence Foundation of China for?nancial support.The authors also thank our colleagues and other students participating in this work.
References
[1]D.Rajkumar,J.G.Kim,Oxidation of various reactive dyes with in situ
electro-generated active chlorine for textile dyeing industry wastewater treatment,J.Hazard.Mater.136(2003)203–212.
[2]F.I.Hai,K.Yamamoto,K.Fukushi,Development of a submerged mem-
brane fungi reactor for textile wastewater treatment,Desalination192 (2006)315–322.
[3]J.S.Chang,Y.C.Lin,Fed-batch bioreactor strategies for microbial decol-
orization of azo dye using a Pseudomonas luteola strain,Biotechnol.Prog.
16(2000)979–985.
[4]Y.H.Hsien,C.F.Chang,Y.H.Chen,S.F.Cheng,Photodegradation of aro-
matic pollutants in water over TiO2supported on molecular sieves,Appl.
Catal.B:Environ.31(2001)241–249.
[5]U.Zissia,G.Lyberatosa,Axo-dye biodegradation under anoxic conditions,
Water Sci.Technol.34(1996)1102–1108.
[6]G.Annadurai,R.S.Juang,P.S.Yen,D.J.Lee,Use of thermally treated waste
biological sludge as dye absorbent,Adv.Environ.Res.7(2003)739–744.
Z.Zhang et al./Journal of Hazardous Materials147(2007)325–333333
[7]H.Q.Zhan,H.Tian,Photocatalytic degradation of acid azo dyes in aqueous
TiO2suspension.I.The effect of substituents,Dyes Pigments37(1998) 231–239.
[8]https://www.sodocs.net/doc/098971182.html,chheb,E.Puzenat,A.Houas,M.Ksibi,E.Elaloui,C.Guillard,
J.M.Herrmann,Photocatalytic degradation of various types of dyes (alizarin S,crocein orange G,methyl red,congo red,methylene blue) in water by UV-irradiated titania,Appl.Catal.B:Environ.39(2002) 75–90.
[9]M.S.Khehra,H.S.Saini, D.K.Sharma, B.S.Chadha,S.S.Chimni,
Biodegradation of azo dye C.I.acid red88by an anoxic–aerobic sequential bioreactor,Dyes Pigments70(2006)1–7.
[10]T.Matthew,A.John,Bumpus biodegradation of congo red by phane-
rochaete chrysosporium,Water Res.32(1998)1713–1717.
[11]T.Sauer,G.Cesconeto Neto,H.J.Jos′e,R.F.P.M.Moreira,Kinetics of photo-
catalytic degradation of reactive dyes in a TiO2slurry reactor,J.Photochem.
Photobiol.A:Chem.149(2002)147–154.
[12]P.Piccinini,C.Minero,M.Vincenti,E.Pelizzetti,Photocatalytic mineral-
ization of nitrogen-containing benzene derivatives,Catal.Today39(1997) 187–195.
[13]I.Safarik,M.Safankova,Detection of low concentrations of malachite
green and crystal violet in water,Water Res.36(2002)196–200.
[14]I.Polaert,L.Estel,A.Ledoux,Microwave-assisted remediation of phe-
nol wastewater on activated charcoal,Chem.Eng.Sci.60(2005)6354–6359.
[15]L.L.Bo,X.Quan,S.Chen,H.M.Zhao,Y.Z.Zhao,Degradation of p-
nitrophenol in aqueous solution by microwave assisted oxidation process through a granular activated carbon?xed bed,Water Res.40(2006) 3061–3068.
[16]Z.H.Ai,P.Yang,X.H.Lu,Degradation of4-chlorophenol by microwave
irradiation enhanced advanced oxidation processes,Chemosphere60 (2005)824–827.[17]X.Quan,X.T.Liu,L.L.Bo,S.Chen,Y.Z.Zhao,X.Y.Cui,Regenera-
tion of acid orange7-exhausted granular activated carbons with microwave irradiation,Water Res.38(2004)4484–4490.
[18]S.Senthilkumaar,P.Kalaamani,K.Porkodi,P.R.Varadarajan,C.V.Sub-
buraam,Adsorption of dissolved reactive red dye from aqueous phase onto activated carbon prepared from agricultural waste,Bioresource Technol.
97(2006)1618–1625.
[19]N.F.Fahim, B.N.Barsoum, A.E.Eid,M.S.Khalil,Removal of
chromium(III)from tannery wastewater using activated carbon from sugar industrial waste,J.Hazard.Mater.B136(2006)303–309.
[20]X.T.Liu,X.Quan,L.L.Bo,S.Chen,Y.Z.Zhao,Simultaneous pen-
tachlorophenol decomposition and granular activated carbon regeneration assisted by microwave irradiation,Carbon42(2004)415–422.
[21]M.L.Canle,J.A.Santaballa,E.Vulliet,On the mechanism of TiO2-
photocatalyzed degradation of aniline derivatives,J.Photochem.Photobiol.
A:Chem.175(2005)192–200.
[22]H.M.Coleman,K.Chiang,R.Amal,Effects of Ag and Pt on photocatalytic
degradation of endocrine disrupting chemicals in water,Chem.Eng.J.113 (2005)65–72.
[23]J.Wang,G.Zhang,Z.H.Zhang,X.D.Zhang,G.Zhao,F.Y.Wen,Z.J.Pan,
Y.Li,P.Zhang,P.L.Kang,Investigation on photocatalytic degradation of ethyl violet dyestuff using visible light in the presence of ordinary rutile TiO2catalyst doped with upconversion luminescence agent,Water Res.40 (2006)2143–2150.
[24]X.W.Zhang,Y.Z.Wang,G.T.Li,J.H.Qu,Oxidative decomposition of azo
dye C.I.acid orange7(AO7)under microwave electrodeless lamp irradia-tion in the presence of H2O2,J.Hazard.Mater.B134(2006)183–189. [25]J.Wang,B.D.Guo,X.D.Zhang,Z.H.Zhang,J.T.Han,J.Wu,Sonocatalytic
degradation of methyl orange in the presence of TiO2catalysts and catalytic activity comparison of rutile and anatase,Ultrason.Sonochem.12(2005) 331–337.
黄自艺术歌曲钢琴伴奏及艺术成就
【摘要】黄自先生是我国杰出的音乐家，他以艺术歌曲的创作最为代表。而黄自先生特别强调了钢琴伴奏对于艺术歌曲组成的重要性。本文是以黄自先生创作的具有爱国主义和人道主义的艺术歌曲《天伦歌》为研究对象，通过对作品分析，归纳钢琴伴奏的弹奏方法与特点，并总结黄自先生的艺术成就与贡献。 【关键词】艺术歌曲；和声；伴奏织体；弹奏技巧 一、黄自艺术歌曲《天伦歌》的分析 （一）《天伦歌》的人文及创作背景。黄自的艺术歌曲《天伦歌》是一首具有教育意义和人道主义精神的作品。同时，它也具有民族性的特点。这首作品是根据联华公司的影片《天伦》而创作的主题曲，也是我国近代音乐史上第一首为电影谱写的艺术歌曲。作品创作于我国政治动荡、经济不稳定的30年代，这个时期，这种文化思潮冲击着我国各个领域，连音乐艺术领域也未幸免――以《毛毛雨》为代表的黄色歌曲流传广泛，对人民大众，尤其是青少年的不良影响极其深刻，黄自为此担忧，创作了大量艺术修养和文化水平较高的艺术歌曲。《天伦歌》就是在这样的历史背景下创作的，作品以孤儿失去亲人的苦痛为起点，发展到人民的发愤图强，最后升华到博爱、奋起的民族志向，对青少年的爱国主义教育有着重要的影响。 （二）《天伦歌》曲式与和声。《天伦歌》是并列三部曲式，为a+b+c，最后扩充并达到全曲的高潮。作品中引子和coda所使用的音乐材料相同，前后呼应，合头合尾。这首艺术歌曲结构规整，乐句进行的较为清晰，所使用的节拍韵律符合歌词的特点，如三连音紧密连接，为突出歌词中号召的力量等。 和声上，充分体现了中西方作曲技法融合的创作特性。使用了很多七和弦。其中，一部分是西方的和声，一部分是将我国传统的五声调式中的五个音纵向的结合，构成五声性和弦。与前两首作品相比，《天伦歌》的民族性因素增强，这也与它本身的歌词内容和要弘扬的爱国主义精神相对应。 （三）《天伦歌》的伴奏织体分析。《天伦歌》的前奏使用了a段进唱的旋律发展而来的，具有五声调性特点，增添了民族性的色彩。在作品的第10小节转调入近关系调，调性的转换使歌曲增添抒情的情绪。这时的伴奏加强和弦力度，采用切分节奏，节拍重音突出，与a段形成强弱的明显对比，突出悲壮情绪。 c段的伴奏采用进行曲的风格，右手以和弦为主，表现铿锵有力的进行。右手为上行进行，把全曲推向最高潮。左手仍以柱式和弦为主，保持节奏稳定。在作品的扩展乐段，左手的节拍低音上行与右手的八度和弦与音程对应，推动音乐朝向宏伟、壮丽的方向进行。coda 处，与引子材料相同，首尾呼应。 二、《天伦歌》实践研究 《天伦歌》是具有很强民族性因素的作品。所谓民族性，体现在所使用的五声性和声、传统歌词韵律以及歌曲段落发展等方面上。 作品的整个发展过程可以用伤感――悲壮――兴奋――宏达四个过程来表述。在钢琴伴奏弹奏的时候，要以演唱者的歌唱状态为中心，选择合适的伴奏音量、音色和音质来配合，做到对演唱者的演唱同步，并起到连接、补充、修饰等辅助作用。 作品分为三段，即a+b+c+扩充段落。第一段以五声音阶的进行为主，表现儿童失去父母的悲伤和痛苦，前奏进入时要弹奏的使用稍凄楚的音色，左手低音重复进行，在弹奏完第一个低音后，要迅速的找到下一个跨音区的音符；右手弹奏的要有棱角，在前奏结束的时候第四小节的t方向的延音处，要给演唱者留有准备。演唱者进入后，左手整体的踏板使用的要连贯。随着作品发展，伴奏与旋律声部出现轮唱的形式，要弹奏的流动性强，稍突出一些。后以mf力度出现的具有转调性质的琶音奏法，要弹奏的如流水般连贯。在重复段落，即“小
我国艺术歌曲钢琴伴奏-精
我国艺术歌曲钢琴伴奏-精 2020-12-12 【关键字】传统、作风、整体、现代、快速、统一、发展、建立、了解、研究、特点、突出、关键、内涵、情绪、力量、地位、需要、氛围、重点、需求、特色、作用、结构、关系、增强、塑造、借鉴、把握、形成、丰富、满足、帮助、发挥、提高、内心 【摘要】艺术歌曲中，伴奏、旋律、诗歌三者是不可分割的重 要因素，它们三个共同构成一个统一体，伴奏声部与声乐演唱处于 同样的重要地位。形成了人声与器乐的巧妙的结合，即钢琴和歌唱 的二重奏。钢琴部分的音乐使歌曲紧密的联系起来，组成形象变化 丰富而且不中断的套曲，把音乐表达的淋漓尽致。 【关键词】艺术歌曲；钢琴伴奏；中国艺术歌曲 艺术歌曲中，钢琴伴奏不是简单、辅助的衬托，而是根据音乐 作品的内容为表现音乐形象的需要来进行创作的重要部分。准确了 解钢琴伴奏与艺术歌曲之间的关系,深层次地了解其钢琴伴奏的风 格特点,能帮助我们更为准确地把握钢琴伴奏在艺术歌曲中的作用 和地位，从而在演奏实践中为歌曲的演唱起到更好的烘托作用。 一、中国艺术歌曲与钢琴伴奏 “中西结合”是中国艺术歌曲中钢琴伴奏的主要特征之一，作 曲家们将西洋作曲技法同中国的传统文化相结合，从开始的借鉴古 典乐派和浪漫主义时期的创作风格，到尝试接近民族乐派及印象主 义乐派的风格，在融入中国风格的钢琴伴奏写作，都是对中国艺术 歌曲中钢琴写作技法的进一步尝试和提高。也为后来的艺术歌曲写 作提供了更多宝贵的经验，在长期发展中，我国艺术歌曲的钢琴伴 奏也逐渐呈现出多姿多彩的音乐风格和特色。中国艺术歌曲的钢琴
写作中，不可忽略的是钢琴伴奏织体的作用，因此作曲家们通常都以丰富的伴奏织体来烘托歌曲的意境，铺垫音乐背景，增强音乐感染力。和声织体，复调织体都在许多作品中使用，较为常见的是综合织体。这些不同的伴奏织体的歌曲，极大限度的发挥了钢琴的艺术表现力，起到了渲染歌曲氛围，揭示内心情感，塑造歌曲背景的重要作用。钢琴伴奏成为整体乐思不可缺少的部分。优秀的钢琴伴奏织体，对发掘歌曲内涵，表现音乐形象，构架诗词与音乐之间的桥梁等方面具有很大的意义。在不断发展和探索中，也将许多伴奏织体使用得非常娴熟精确。 二、青主艺术歌曲《我住长江头》中钢琴伴奏的特点 《我住长江头》原词模仿民歌风格，抒写一个女子怀念其爱人的深情。青主以清新悠远的音乐体现了原词的意境，而又别有寄寓。歌调悠长，但有别于民间的山歌小曲；句尾经常出现下行或向上的拖腔，听起来更接近于吟哦古诗的意味，却又比吟诗更具激情。钢琴伴奏以江水般流动的音型贯穿全曲，衬托着气息宽广的歌唱，象征着绵绵不断的情思。由于运用了自然调式的旋律与和声，显得自由舒畅，富于浪漫气息，并具有民族风味。最有新意的是，歌曲突破了“卜算子”词牌双调上、下两阕一般应取平行反复结构的惯例，而把下阕单独反复了三次，并且一次比一次激动，最后在全曲的高音区以ff结束。这样的处理突出了思念之情的真切和执著，并具有单纯的情歌所没有的昂奋力量。这是因为作者当年是大革命的参加者，正被反动派通缉，才不得不以破格的音乐处理，假借古代的