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關鍵詞: 無鹽少水染色;活性染料;染色性能;上染速率;半染時間
中圖分類號: TS193.841 文獻標志碼: A
棉織物傳統染色是用活性染料以水為介質而染色的,由于活性染料水溶性極高,需要鹽來克服染料與纖維之間的靜電排斥力,未經固色的染料和不可降解的無機鹽都會作為染色廢水排放,造成環境問題[1-3]。然而,棉織物的活性染料傳統水浴染色工藝中普遍存在促染無機鹽用量大,耗水量高,廢水處理負擔重等問題[4-6]。染色廢水的常規處理方法有很多,包括利用天然纖維素基材料對廢水中的染料進行吸附去除、光催化降解、膜分離、電化學,以及化學和生物處理方法等[7-9]。然而,它們的缺點是去除印染廢水中的無機鹽及染料昂貴且效率低下,處理這一問題的最佳方法是減少初始用水量[10-11]。因此,活性染料少水污水零排放染色是行業發展重要方向。近年來,一些研究人員開始研究新的染色方法[12],以實現活性染料無鹽或少水染色。其中,非水介質無鹽少水體系被認為是極具前景的安全綠色染色體系之一,具有可以解決傳統水浴法中染料和電解質殘留量大、廢水處理困難、染色效率低等主要問題的優點[13-16]。
在染色非水介質染色過程中,染料溶解在極性的水溶液中,以液滴的形式被非極性的有機非水介質緊緊包覆并在其中均勻分散,在機械力的作用下,向纖維表面快速遷移[17-18]。由于使用少量的水,活性染料的水解被抑制,染色樣品的表觀色深優于傳統水浴染色[19]。為避免上染過快產生色斑現象,并獲得最佳的染色工藝,針對染料在染浴中的擴散過程進行探究十分重要,已取得了一定的成果[20-21]。Tan等[22]認為,準一級、準二級吸附動力學是最常見的液體吸附模型,并在多個領域進行應用。Alberti等[23]討論了間歇吸附模型和動態吸附模型,指出化學物質吸附的程度只取決于初始平衡態和最終平衡態之間的差,而速率則取決于從初始到最終步驟的路徑。Sadeghi等[24]以蘆葦為原料合成了碳納米結構,作為去除廢水中重金屬的方法之一,采用準一階和準二階模型對金屬離子進行了吸附動力學研究,表明吸附劑對吸附質的吸附是通過化學過程或活化表面發生的。另外,染色動力學在染色領域也多有應用,Pei等[25]研究了不同種類活性染料在硅氧烷非水介質染色體系中不同潤濕性棉紗上的染色平衡、動力學及機理,發現隨著棉紗潤濕性的增加,活性染料的染色率提高,最終吸收率基本保持不變,為探究棉纖維潤濕性對硅氧烷非水介質染色動力學的影響探究提供了重要依據。Armagan等[26]探究了活性染料在礦物上吸附的動力學和平衡模型,以尋求去除水中活性染料的有效吸附劑,發現對于不同的染料,平衡吸附有很大差異。
本文選擇常用中溫染料C.I.活性黃145為研究對象,研究其在傳統水浴和硅氧烷兩種體系中的上染性能及其染色動力學,探討影響活性染料在硅氧烷介質無鹽少水體系中上染的關鍵因素,為不同用量活性染料在無鹽少水染色體系中的應用提供理論指導。
1 試 驗
1.1 材料與藥品
100%純棉機織物(平方米質量146 g/m2,紗密度134×257,紗支35 S×35 S)(紹興富閏染整有限公司),C.I.活性黃145(原粉)(湖北力源科技有限公司),純度gt;96%的十甲基環五硅氧烷(D5)(江西藍星星火有機硅有限公司),分析級無水碳酸鈉(Na2CO)和分析級無水硫酸鈉(Na2SO4)(中國國藥化學試劑有限公司)。D5及活性黃145的分子結構如圖1所示。
1.2 儀 器
UV/Vis-2600紫外-可見分光光度計(日本島津公司),Dye-24可調向式染色機(上海千里自動化設備有限公司),顏色品質測色比色儀(美國亨特利儀器有限公司)。
1.3 染色過程
常規水浴染色體系:染料質量分數X%(X=0.5、2.0、5.0、8.0),具有良好潤濕特性的棉織物2 g,浴比1︰20,硫酸鈉質量濃度40 g/L,染色溫度40 ℃,固色溫度60 ℃,碳酸鈉質量濃度15 g/L。將經過前處理的棉織物加入40 ℃染色浴中上染10 min,并在此溫度下每隔15 min加入一半硫酸鈉使染料充分上染。然后升溫至60 ℃,加入15 g/L的碳酸鈉使染
料在纖維上固色30 min。降溫后對染后的棉織物進行皂洗、水洗和烘干,染色過程曲線如圖2(a)所示。
無鹽少水染色體系:染料質量分數X%(X=0.5、2.0、5.0、8.0),經過前處理并在標準條件下恒溫恒濕處理的棉織物2 g,浴比1︰20,帶液率150%(相對于織物),染色溫度40 ℃,固色溫度60 ℃,碳酸鈉質量分數12.5%。將溶解后的染液加入D5非水介質液中,經磁力攪拌器上攪拌使染料在D5中均勻分散,從而形成活性染料/硅基非水介質染色體系。將前處理制得的棉織物在此體系中40 ℃下上染30 min使染料充分上染,然后升溫至60 ℃固色30 min。固色完成后,對染后纖維進行皂洗、水洗和烘干,染色過程曲線如圖2(b)所示。
1.4 染色性能評估
1.4.1 標準曲線繪制
用電子天平稱取0.100 g的活性黃145,并用去離子水定容到500 mL容量瓶。然后分別移取1、2、3、4、5、6 mL配制好的溶液于10 mL的容量瓶中,并用去離子水定容。通過紫外分光光度計測定各個質量濃度的活性黃145最大吸收波長處的吸光度,根據不同染料質量濃度與測得的吸光度的關系,制作活性黃145的標準工作曲線。
1.4.2 K/S測試
在顏色品質測色比色儀上測定染色織物K/S值。
1.4.3 上染率測試
根據先前制得活性黃145的標準工作曲線,利用染色前后染料質量濃度與吸光度的關系,上染結束后,將棉織物離心后的殘液倒入染色殘液中。用等量去離子水萃取出染色前后D5介質中的活性染料,定容并采用UV/Vis-2600紫外分光光度計測試吸光度。傳統水浴染色取染色前后染液進行吸光度測試即可,通過殘液法計算染料的上染百分率(E)。計算如下式所示:
式中:A0是初始染液的吸光度,A1是染色后殘液的吸光度。
1.4.4 固色率計算
染料的固色率是染色完成后與纖維發生共價鍵結合的染料占投入染料總量的百分比。計算如下式所示:
式中:C1指初始染料質量濃度,mg/L;V1指初始染液體積,mL;C2指染色后殘液質量濃度,mg/L;V2指染色后殘液體積,mL。
1.4.5 動力學曲線的繪制
非水介質上染速率曲線的繪制:準確稱取9份1 g的棉織物,并配置10份活性染料/非水介質染色液,其中染料質量分數為X%(X=0.5、2.0、5.0、8.0),無水碳酸鈉的質量分數為12.5%(相對于織物),浴比1︰50。首先,將染液在恒溫水浴鍋中于設定的室溫下保溫10 min。然后,帶液率為150%的棉織物分別投入染浴中進行染色,以設定的時間(0.5、1、5、10、20、40、60、80、120 min)依次將染色樣取出,并用適量去離子水萃取非水介質中剩余的染料,分液定容后用紫外分光光度計測染料在最大吸收波長處的吸光度。按下式計算纖維上染料的含量qt:
qt=E×X(3)
式中:X指初始染料質量,mg。
根據式(1)計算的上染百分率及式(3)計算的纖維上染料的含量,繪制染色動力學曲線。
常規水浴上染速率曲線的繪制:棉織物的質量、份數、浴比、染色溫度、染色時間與非水介質體系相同,無水碳酸鈉的質量濃度為15 g/L,無水硫酸鈉的質量濃度為40 g/L,配置好染液后,在恒溫振蕩水浴鍋中保持10 min,將織物投入染液中,其余步驟同上。
2 結果與分析
2.1 染料質量濃度對染色織物染色效果的影響
為了實現棉織物在不同染料質量濃度的無鹽染色,并評價染料在D5染色體系中的吸附動力學和染料與纖維的親和力,本文對染色效果進行了分析,活性黃145標準曲線如圖3所示。
由圖3可知,當染料質量濃度較低時,染料溶液質量濃度與吸光度為正比關系,符合朗博-比爾定律。通過染料質量濃度與吸光度的關系計算活性染料染色后的上染率及固色率。
圖4為不同染色介質中染料質量分數對棉織物染色的上染率、固色率、K/S值及ΔE的影響。活性染料本身直接性較低,因此傳統水浴染色過程中需加入大量無機鹽,從而降低染料與纖維之間的庫侖力,進而提高染料的利用率。傳統染浴中,活性黃145的固色率隨染料質量分數的增高從70.8%降低到43.1%。非水介質染色體系在無鹽促染條件下,上染率基本達到100%,總固著率隨著染料質量分數增高僅從83.6%降至72.5%。當染料質量分數相同時,無鹽促染的D5非水介質體系中染色織物的K/S值均要大于常規水浴染色織物。在染料質量分數為2%時,D5非水介質體系中染色織物的K/S值為17.4,而常規水浴染色織物的K/S值為13.6。不同染浴染色織物ΔE值均在0.5以下,勻染性較好。其中,D5非水介質染色體系中ΔE值由0.46下降到0.16,染深色織物時勻染性較佳。相較于水浴染色,活性染料/D5非水介質染色具有良好的染色效果,并且大量節省無機鹽及染料的質量分數。
活性黃145在非水介質染色體系的高K/S值、高固色率應歸因于四個關鍵點。首先,該染料含有兩個活性基團,使其對棉纖維的反應性增強,可快速與棉織物表面羥基通過共價鍵連接[27-28]。其次,D5非水介質染色體系含水量較低,大幅地降低了染料水解[29]。再次,活性黃145的共平面較好,且含有15個共軛雙鍵,這是賦予其與纖維的高親和力,實現高染料固著率的重要因素,并對其與纖維的親和力起著重要的作用[30]。最后,活性黃145含有多個水溶性基團,水溶性較好,在非水介質體系中形成的染料高質量分數條件下,染料分子受堿劑作用導致的聚集現象影響較小[31]。
由表1可知,在D5非水介質染色體系中,不同染料質量分數條件下,染色棉織物的水洗色牢度大多在4級以上,褪色色牢度均在4級以上,耐干摩擦色牢度為5級,濕摩擦色牢度大多達到4級以上,僅有8%染料染色棉織物濕摩擦色牢度和水洗色牢度為3~4級,其他各項色牢度優良。因此,活性黃145在D5非水介質染色體系中對棉織物染色的色牢度較好,均達到國標要求。
2.2 染色速率
為了進一步了解活性染料在非水介質中的擴散行為,本文探究了活性黃145在非水介質無鹽少水體系和水浴體系中的染色動力學和機理。活性黃145在不同體系中吸附動力曲線如圖5所示。
由圖5可得,在D5非水介質染色體系,體系含水量僅為150%,相對體系含水量較少,染料溶解在水中形成高質量分數染浴,由于極性染液本身和非極性D5介質互不相容及纖維相和水浴相染料巨大的質量分數差異,染料快速擴散至纖維內部,因此活性染料無須加入任何無機鹽就可以得到相對于水浴中較快的上染速率。D5非水介質染色體系中,最終上染率隨時間增長而保持不變,隨染料質量分數增大而增高。而水浴染色可以明顯看出最終上染率在測試時間范圍內,隨時間增長而增大,隨染料質量分數增大而增高(但質量分數高于5%時,增長趨勢趨緩。
2.3 準一級反應動力學模型的擬合
吸附機理取決于吸附劑的物理和化學特性及質量傳遞過程[25],為了探究不同用量活性染料在D5非水介質染色體系及水浴染色體系中擴散情況,進一步提高對非水介質染色下活性染料染棉織物過程的控制及染色工藝優化的理論指導作用,本文采用準一級、準二級動力學模型對活性黃145在D5非水介質染色體系及水浴染色體系上染棉織物的試驗數據進行擬合,如圖6、表2所示。
準一級動力學模型可用Lagergren表示,如下式所示:
式中:qe為反應平衡時染色棉織物上染量,mg/g;qt為染色時間t時上染棉織物的染料量,mg/g;k1為一級動力學反應速率常數,min-1。
在0~t min內對式(4)進行積分,得到下式:
ln(qe-qt)=lnqt-k1t(5)
由圖6及表2可知,活性染料在兩種介質中的準一級動力學擬合決定系數R2較低,最低可達到0.687。且D5非水介質染色體系中R2在0.687~0.820,隨著染料質量分數變化沒有明顯的變化趨勢。而水浴中R2變化隨染料質量分數增大由0.983逐漸減小為0.964,染料質量分數越大,擬合程度越差。另外,相同染料質量分數下,D5非水介質染色體系中R2均小于水浴中R2。以上研究表明,準一級動力學模型并不能準確地描述高質量分數活性染料水溶液在這兩種介質中對棉纖維的上染行為。
2.4 準二級反應動力學模型的擬合
準二級動力學模型如下式所示:
式中:qe為反應平衡時纖維上活性染料的含量,mg/g;qt為染色時間t時上染棉織物的染料量,mg/g;k2為二級動力學反應速率常數,g/(mg·min)。
簡化式(6)可得:
由式(7)可知,k2和qe可以直接從t/qt-t曲線的截距(b)和斜率(tanα)中計算求得,如下式所示:
則k2=1bqe,qe=1tanα。斜率越大,則qe越小,即染色平衡吸附量就越小。
染色速率也可用一半染料達到平衡吸附量所需的半染時間(t0.5)來表示,計算如下式所示:
由圖7和表3可知,t/qt與染色時間t的擬合曲線呈明顯的線性正相關關系,不同質量分數染料D5非水體系中R2在0.999以上,水浴體系R2在0.990以上。隨著染料質量分數的增大,非水介質無鹽少水染色體系中活性染料的最終吸附量與水浴體系最終吸附量的差距逐漸增大,8%染色時最終吸附量相差兩倍以上。染料計算上染量與D5非水體系和傳統水體系的染料實際上染量非常接近,進一步表明準二級動力學模型適用于描述D5非水體系和傳統水體系中活性染料在棉織物上的染色動力學[32]。
對于不同的染色體系,本文研究發現D5非水體系的染料平衡上染量qe,cal、實驗qe,exp和速率常數值k2均高于傳統水浴染色體系。不同染色質量分數下D5非水介質體系k2均大于水浴體系k2。隨著染色質量分數的增加,水浴染色半染時間t0.5從16.60下降至7.48。而D5非水介質體系t0.5顯著低于水浴染色且與染料濃度相關性較小(分布在2.03~2.58),表明染料質量分數對D5非水介質體系影響較小。這是由于分散在非水介質中的高質量分數染液會因為親纖維而憎D5介質的特性快速吸附至纖維表面[33],并向纖維內部滲透,從而導致染料的t0.5較小且與染料質量分數相關性較小。這些結果表明,活性染料在無鹽少水體系中的染色速度比在傳統水浴體系中的染色速度快、染料利用率高,且染色后織物的得色比較深。
3 結 論
本文研究了不同質量分數活性黃145染料在不同介質染色體系中對棉織物的染色效果、吸附平衡及染色動力學。在D5非水染色體系和傳統水染色體系中,活性染料固色率及染色織物的K/S值隨著染料質量分數的升高而提高。隨著體系內染料量的增加,相較于傳統水浴染色,非水介質無鹽少水染色體系中活性染料的最終固色率降低程度更小。
與傳統的水浴活性染色相比,非水介質無鹽少水染色體系中活性黃145的吸收率更高(gt;95%)。此外,活性染料的固色率也較高(非水染色為72%~84%,傳統染色為43%~71%),棉織物染色后顏色更深。準二級動力學模型對染料吸附過程的擬合效果最好,可以充分描述活性染料在非水染色體系和傳統水染色體系中的吸附和平衡。隨著染料質量分數的增大,活性黃145在水浴體系中的半染時間明顯縮短,但對非水介質無鹽少水染色體系半染時間影響較小。在非水染色系統中,活性染料的吸附速度明顯快于傳統水浴,8%染色質量分數體系中最終吸收率比傳統水浴體系提高了一倍以上。在D5非水染色體系中,活性染料在25℃下的吸附平衡時間僅為5~20 min,而在傳統水浴染色系統中需要更長的時間。
在D5無鹽少堿非水介質少水染色體系中,除了染料組分之外,只有幾種主要組分(如表面活性劑的種類、不同類型及不同質量分數的堿劑等)對其固色牢度及勻染性有著重要影響。但目前在D5非水介質染色體系中,對于這些影響因素的研究還未見報道。
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Study on the dyeing and kinetics of reactive yellow 145 in thesalt-free and low-water dyeing system
ZHANG Chi, WANG Xiangrong
ZHU He1, PEI Liujun1, GUO Peiting1b, WANG Jiping1, DONG Aixue2, WANG Zongqian3
(1a.Shanghai Engineering Research Center of Textile Chemistry and Cleaner Production; 1b.School of Textiles and Fashion, Shanghai University ofEngineering Science, Shanghai 201620, China; 2.Key Laboratory of Clean Dyeing and Finishing Technology of Zhejiang Province,Shaoxing 312000, China; 3.School of Textile and Garment, Anhui Polytechnic University, Wuhu 241000, China)
Abstract: Reactive dyes have been widely used in cotton fabrics’ dyeing due to their excellent application performance such as color diversity and simple use. Traditional dyeing of reactive dyes/cotton fabrics is carried out under water bath conditions, which consumes a large amount of energy and dyeing auxiliaries, and generates a large amount of dyeing wastewater. The non-aqueous medium (decamethylcyclopentasiloxane) dyeing system of reactive dyes has attracted attention due to its significant advantages of zero salt and low water content in the dyeing process, high dye utilization rate, and energy conservation and environmental protection. It can effectively solve the problems of low dye utilization, high electrolyte consumption, and large sewage discharge in traditional reactive dyes’ water bath dyeing. The dye solution is completely insoluble in the non-aqueous phase, but has a strong affinity for cotton fibers, so that more of the dye is rapidly distributed to the fibers with a small amount of water in a non-aqueous medium. However, in the dyeing system, polar aqueous solutions are tightly encapsulated by organic non-polar non-aqueous media, forming a high concentration of dye solution, resulting in poor dispersion of dyes in non-aqueous media. This may also cause aggregation or precipitation of dye molecules and uneven dyeing.
The research on the adsorption mechanism of a reactive dye solution in salt-free and low-water dyeing systems is limited. In particular, the comprehensive information on the effects of media on the diffusion and adsorption models of reactive dyes has not been systematically studied. In order to study the dyeing properties and dyeing kinetics of reactive dyes in the traditional water bath system and siloxane system, and to explore the key factors affecting the dyeing of reactive dyes in non-aqueous medium salt-free and low-water dyeing systems, the reactive dye of cyanuric acid-vinyl sulfone (reactive yellow 145) was selected. The dyeing of reactive yellow 145 in the non-aqueous medium dyeing system and the traditional water bath dyeing system was investigated, and an adsorption kinetic model of reactive dyes was established to explore the key factors affecting the dyeing of reactive dyes in non-aqueous medium salt-free and low-water dyeing systems. The intrinsic relationship between the diffusion behavior of reactive yellow 145 in non-aqueous dyeing systems was successfully determined, and the adsorption kinetics and mechanisms of reactive dyes in non-aqueous dyeing systems and water bath systems were revealed. The experimental results show that the absorption rate of active yellow 145 is higher (gt;95%) and the fixation rate is also higher (72%-84% for non-aqueous dyeing and 43%-71% for traditional dyeing) in the non-aqueous medium salt-free and low-water dyeing system. The K/S value of cotton fabric after dyeing is higher (5.97-26.63 for non-aqueous dyeing and 4.35-21.92 for traditional dyeing). The dyeing kinetics of reactive yellow 145 in the two dyeing systems can be described by using a quasi-second-order kinetic model. As the dye concentration increases, the difference between the final adsorption amount of reactive dyes in the non-aqueous medium salt-free and low-water dyeing system and the final adsorption amount in the water bath system gradually increases. When the dye dosage is 8%, the final adsorption capacity of the traditional water bath system (68.32) is more than twice compared to 29.20. The half dyeing time distribution of the water bath dyeing system is between 16.60 and 7.48. The half dyeing time distribution of the water bath dyeing system is between 16.60 and 7.48. The distribution of semi staining time in non-aqueous media is between 2.03 and 2.58. These results indicate that the dyeing speed of reactive dyes in salt-free and low-water systems is much higher than that in traditional water bath systems, and the dye utilization rate is high. The K/S value of the dyed fabric is also high.
Non-aqueous dyeing technology provides an innovative method to increase dye uptake at low energy consumption, in addition to saving large amounts of water. This study provides theoretical guidance for the dyeing of cotton fabrics with different dyeing depth requirements in the salt-free and low-water dyeing system, and it is of great significance to improve the practical application of reactive dyestuffs in non-aqueous medium salt-free and low-water dyeing system as well as industrial production.
Key words: salt-free and low-water dyeing; reactive dyes; dyeing performance; dyeing rate; half-dyeing time
收稿日期: 2023-12-12; 修回日期: 2023-04-30
基金項目: 國家自然科學基金項目(22072089);安徽省重點研發項目(2023t07020001);海寧市科技計劃工業、農業項目(2021003);上海市松江區科學技術攻關項目(23SJJBGS2);浙江省清潔染整技術研究重點實驗室開放基金項目(QJRZ2301)
作者簡介: 朱赫(1998),男,碩士研究生,研究方向為非水介質染色。通信作者:裴劉軍,副教授,peilj@sues.edu.cn。