Influence of the Process Conditions on the Formation of AOX Compounds during Wool Chlorine Pretreatm

Journal of Dong Hua University ( Eng. Ed.) Vol. 18 No .4(2001) 1Influence of the Process Conditions on the Formation 0f A0XCompounds during Wool Chlorine PretreatmentWang Jing(王晶), He Jinxin(何瑾馨), Dai Jjinjin(戴瑾瑾)Institute of Chemisiry and Chemical Engineering , Dong Hua University , Shanghai , 200051Chlorination occurred simultaneously with oxidationwhen wool was treated by chlorine-containing reagents. .The adsorbable organic halogens( A0X) compounds wereExperimentalproduced by the chlorination of amino acid residues,especially tyrosine residue. The factors that might1. Chemicalsinfluence the reaction of dichloroisocyanuric acidDichloruisocyanuniec acid ( DCCA) ( Basolaun DC) was(DCCA) with tyrosine residue were discussed. Highersupported by BASF. Oher chemicals were purchased as chenicaltemperature, appropriate pH value and lowerreagents and they are aill AR grade rcagents.concentration of chloride ion are favorable to decrcase2. Analytical methodthe percentage of chlorination. Determination of(1) Determination of available chlorine concentration'optimum process conditions would be helpful to controlThe determination of available chlorine in reaction mixture isA0X compounds formation during wool chlorinebased upon the quantitative liberation of iodide in an acidifiedpretreatnent.solution, he iodine then being titrated with sodium thiosulphate,Keywords: wol, srinkprofirg , adsorbable organic halogensusing starch as indicator. The relevant chemnical reactions were(AOX)，controlshown as fllows:H20+ CI0*+2I---→h+ C- + 20H"Introduction25:03- +h-+2I*+ S,O8-The mole of available chlorine is half that of sodiunIn recent years adsorbable organic halogen compoundsthiosulphate.(AOX) produced during wool shrinkproofng treaunent have(2) Determination of chloride ion in reaction mixturesassumed great importance throughout most of the world. A0XAvailable chlorine in reaction mixture can be reduced intobecomes a new parameter for the quantitative determination ofchloride ion by sodium sulfite. The chloride ion was thenorganic halogens in effluents. Most of the chlorinated organicdeternined by indirect precipitation titration based on Volhard"'scompounds are resistant to biodegradaion, they are lipopilic andmethod. According to uhe difference of reduced chlonide ion inconcentrate in fatty tsse. As a consequence they renbain in thesystem before and after reaction, we can calculalte the percentagebiosphere for long periods, causing damages in many differentof chlorine which chlorinated phenol (egn， 1) . The titrationways!"l.procedure and calculation equation were as follows;①ExcessAlthough some reseurchers suggest he zero-chlorine processsodium sulftc solution was put into reaction system, and left forfor wool fl-esist treaument(2-4), it is necessry to study how tolen minutes; ②The sulftce and sulfate ions which influencecontrol the concentration of AOX compounds in wool chlorineitration were renoved by precipitaing with barium nitrate;③Apretreatment because this process is so economical and effectivemeausured excess of AgNO3 was added to precipitalc the chloridethat it is sil the only method used extensively in practice up toion，and the excess Ag' was determined by back tiuration withnow.standard potassium thiocyanate solution:It is reported that the reactionamino acid residues,especially tyrosine residue with chlorine containing reagents mayC-+ Ag*-→ AgCl↓+ cxccss Ag'result in the formation of AOX compounds' 1. Phenol was chosenexcess Ag* + SCN~→AgSCN↓as a model substance of tyrosine residue and its reaction withDOCA was examined. The reslts indicated that temperature, pHthe end point was delected by ading iron( M), in frric alum,and inorganic salts would influence the quantity of A0Xwhich fomms a soluhle red comnlex with the first excess of tiunant:compounds fomed during wool chlorine pretrealment.中国煤化工(SCN)2+TYHCNMHGRezival Nov. 2, 20002Journal of Dong Hua University.(Eng. Ed.) Vol. 18 No. 4 (2001)[Pcc= reduced chloride ion befor reaction (blank) = reduced chloride .ion after reacion x 100%eqn.Iavailable chlorine ( blank)lPC0= 1- PCCIeqn.2Where PCCI; percentage of available chlorine that chlorinated phenolPCO: percentage of available chlorine that oxidized phenolobtained under diferent pH were shown in Fig. 2:Results and Discussion50lt is supposed that oxidation and chlorinating occurred at thesame tine during the reaction of DOCA with phenol. Il0fchlorination was suppressed to a lower exlent under suitableconditions, the AOX compounds in efluent would be reduced.It is common knowledge that the chlorine reacts with anumber of amino acid residues present in wool, but only10monochloro-and dichloro-tyrosine were positively identifed!l. Innonstabilized chlorination liquors the tyrosine residues will be78broken down!n]， suggesting that AOX compounds be mainlyptproduced by the reaction of chlorine with tyrsine residue. In thisFigure2 cfict of pH on PCO (perenuge of available chlorine thatpaper phenol was chosen as a model subsance of tyrosine residuegxidized phenol)and ils reaction with DCCA was examined.1. Efect of temperature on percentage ofIt is known that phenol cam be chiorinated aund oxidized bychlorine simultancously. Phenol is easier to be chlorinated thanavailable chlorine that oxidized phenol (PCO)The results of reaction of phenol with DCCA under differentbenzene because the hydroxy group on the former is aun electron-donating substiwent that has the potential to stabilize theemperatues were shown in figure 1 (pH3.0, 1hr.): .cyclohexadienyl cation intermediate. The chlorination are mainlyortho and para substiution of phenol. In addition, oxidution of40phenol produced a class of cormpounds known as quinones!'Hence, the competition between these two kinds of reactions must3:exist at the same time.It can be seen from figure 1 that PC0 value reached3o-maximum (48.26%) at pH 4.0, which indicated that chlorinationwas prevailing to oxidaion if pH value was higher or lower uhan254.0. As pH increased the phenol would be dissociated intophenoxide. The produced negatively charged oxygen ion hasstronger activating effect on the chlorinaion and will direct to the20position of subsitution of chlorinel71. On the other band, us the20 253035i04555pH decreased the electophilicity of lhypochloric acid wouldincrease with the increase of acidity because of the fllowingTemperature(°C)reaction'8l . Thus the chlorination was aulso a main reaction underFigure 1 efct of Lemperature on . PCO ( percentage of availableRC00H + HC0= RC00CI + H20chlorine that gxidized phenol)It was found that PCO value increased when the temperaurestrong acid conditions. The above results indicated that uhe pHincreased from 24C to 5sC. However, it reached a plateau afterplayed a very important role during the reaction of phenol withDCCA. It detemined the ratio of chlorination to oxidaion. In45C. The results indicated that higher temperature might beorder lo reduce the concentration of AOX compounds formed, pHadvantageous 10 oxidation, in other words, the tale of chorinationshould be controlled to about 4 during wool chlorineshould be more rapid than oxidation under lower temperature. Inpretreatment.agreement with this analysis, the GCMS identification proved that3. Effect of saltsthe most products of the reaction of phenol with DCCA (pH 3.5,is nonmally used in the30C) were chlorinated. Higber temperature seemed to be中国煤化工procewool with DOCA. Thebeneficial to decrease the quantity of AOX conpounds during woolchlorine breaunent.perceMYHC N M H G diferent suls into reaction .system of DCCA and phenol were shown in figure3. { pH 4.0,2. Effect of pH on PCO45C)Phenol reacled with DCCA at 30C for 1 hr.. The resultsThese resuls showed that the PCO value was reducedJoumal of Dong Hua University(Eng. Ed.) Vol. 18 No.4(2001) 3apparently in the presence of chloride, e.g. NaCl and KC. Therole of chlonide ions in promoting chlorinaion could be explainedConclusionby fllowing series of equilibrumn reactions. The chloride ionsadded promoted the formation of a stronger electrophilic speciesDuring shrink-proofing reatment of wool with DOCA,C- -0H, which would strenghen the atck to the aromatic ringchlorination and oxidation of tyrosine residue wouid occursimultaneously. The reaction degrocs of them were variousof phenol, (71(8) thus favourmble to chlorination.acconding to different treating conditions. The factors influencingthe two competition reacions were: ①Temperature. A higher501 blank KNo, NaNO, Na,SO,tenperature was favorable for oxidation.②pHls. The efet o[ pHswas noticeable. PCO value would reach meaximum when pH4CKCIapproached 4.0.③Chloride ion. Addidion of chloride ion wouldNa1suppress PCO value and promote the production of A0Xcompounds.From the above esults, it could be deduced thal process& 20-condition should have the similar influence on the reacion ofDOCA and tyrosine residues during the wool chlorine preureaument.In order to reduce AOX parameter it seemned necessary to treat10wool under the appopriate conditions, which was favorahle to theoxidation and suppressing chlorination.Figure3 effect of slt on PCO (percentage of available chlorineReferencesthat gxidizd phenol)[1] Betina M. Mulle, Rev. Prog. Coloralion, 1992, 22, 14CI[2] DenningR, J. ctal., Texrile Res. J., 1994, 64(7), 4133] 戴班瑾,纺织学报1996, 17(6) ,384[4] FElisabeth Heine and Harwig Hocker, Review of progress in colom-0=C C=00-=C C-0tion, 1995, 25, 57+ H20=+ 2HCOCI-N N- -NaI -N N-Na[S]韩倬玄 主编,定址分析,纺织T.业出版社.北京, 1982.348[6] Sunley H. Pine, Jamcs B. Handnickson, Donald J. Cam. Gouryes. Hammond, Organic Chemisty, fourh cdition, 999[7]恽魁宏 主编,有机化学,第二版,商等教育出版社,北京，1991,483a- +C0~ + 2H=*∞=≈C2+ H20= =a- -0H2+C1[8] 王积涛编,高等有 机化学,人民教自出版社,北京, 1982, 192中国煤化工MYHCNMHG