摘要: 为探究活性染料在非水介质无盐少水染色体系中的染色性能及染色动力学,文章以不同质量分数的活性黄145染料和硅氧烷组成无盐少水染色体系,对棉织物进行染色,对准一级动力学模型和准二级动力学模型进行分析,且与传统水浴染色效果进行对比。结果表明,在相同质量分数下,无盐少水染色体系染色性能较传统水浴更好,其中固色率及K/S值差异随着染料质量分数的增加而增大。活性黄145在两个染色体系中的染色动力学可以用准二级动力学模型来描述,相较于传统水浴体系,无盐少水染色体系具有更高的染料最终吸附量和更小的半染时间。随着染料质量分数的增大,染料最终吸收量的差距逐渐提高,半染时间逐渐缩短。为活性染料在非水介质无盐少水染色体系中的染色实践提供了理论指导。
关键词: 无盐少水染色;活性染料;染色性能;上染速率;半染时间
中图分类号: TS193.841 文献标志码: A
棉织物传统染色是用活性染料以水为介质而染色的,由于活性染料水溶性极高,需要盐来克服染料与纤维之间的静电排斥力,未经固色的染料和不可降解的无机盐都会作为染色废水排放,造成环境问题[1-3]。然而,棉织物的活性染料传统水浴染色工艺中普遍存在促染无机盐用量大,耗水量高,废水处理负担重等问题[4-6]。染色废水的常规处理方法有很多,包括利用天然纤维素基材料对废水中的染料进行吸附去除、光催化降解、膜分离、电化学,以及化学和生物处理方法等[7-9]。然而,它们的缺点是去除印染废水中的无机盐及染料昂贵且效率低下,处理这一问题的最佳方法是减少初始用水量[10-11]。因此,活性染料少水污水零排放染色是行业发展重要方向。近年来,一些研究人员开始研究新的染色方法[12],以实现活性染料无盐或少水染色。其中,非水介质无盐少水体系被认为是极具前景的安全绿色染色体系之一,具有可以解决传统水浴法中染料和电解质残留量大、废水处理困难、染色效率低等主要问题的优点[13-16]。
在染色非水介质染色过程中,染料溶解在极性的水溶液中,以液滴的形式被非极性的有机非水介质紧紧包覆并在其中均匀分散,在机械力的作用下,向纤维表面快速迁移[17-18]。由于使用少量的水,活性染料的水解被抑制,染色样品的表观色深优于传统水浴染色[19]。为避免上染过快产生色斑现象,并获得最佳的染色工艺,针对染料在染浴中的扩散过程进行探究十分重要,已取得了一定的成果[20-21]。Tan等[22]认为,准一级、准二级吸附动力学是最常见的液体吸附模型,并在多个领域进行应用。Alberti等[23]讨论了间歇吸附模型和动态吸附模型,指出化学物质吸附的程度只取决于初始平衡态和最终平衡态之间的差,而速率则取决于从初始到最终步骤的路径。Sadeghi等[24]以芦苇为原料合成了碳纳米结构,作为去除废水中重金属的方法之一,采用准一阶和准二阶模型对金属离子进行了吸附动力学研究,表明吸附剂对吸附质的吸附是通过化学过程或活化表面发生的。另外,染色动力学在染色领域也多有应用,Pei等[25]研究了不同种类活性染料在硅氧烷非水介质染色体系中不同润湿性棉纱上的染色平衡、动力学及机理,发现随着棉纱润湿性的增加,活性染料的染色率提高,最终吸收率基本保持不变,为探究棉纤维润湿性对硅氧烷非水介质染色动力学的影响探究提供了重要依据。Armagan等[26]探究了活性染料在矿物上吸附的动力学和平衡模型,以寻求去除水中活性染料的有效吸附剂,发现对于不同的染料,平衡吸附有很大差异。
本文选择常用中温染料C.I.活性黄145为研究对象,研究其在传统水浴和硅氧烷两种体系中的上染性能及其染色动力学,探讨影响活性染料在硅氧烷介质无盐少水体系中上染的关键因素,为不同用量活性染料在无盐少水染色体系中的应用提供理论指导。
1 试 验
1.1 材料与药品
100%纯棉机织物(平方米质量146 g/m2,纱密度134×257,纱支35 S×35 S)(绍兴富闰染整有限公司),C.I.活性黄145(原粉)(湖北力源科技有限公司),纯度gt;96%的十甲基环五硅氧烷(D5)(江西蓝星星火有机硅有限公司),分析级无水碳酸钠(Na2CO)和分析级无水硫酸钠(Na2SO4)(中国国药化学试剂有限公司)。D5及活性黄145的分子结构如图1所示。
1.2 仪 器
UV/Vis-2600紫外-可见分光光度计(日本岛津公司),Dye-24可调向式染色机(上海千里自动化设备有限公司),颜色品质测色比色仪(美国亨特利仪器有限公司)。
1.3 染色过程
常规水浴染色体系:染料质量分数X%(X=0.5、2.0、5.0、8.0),具有良好润湿特性的棉织物2 g,浴比1︰20,硫酸钠质量浓度40 g/L,染色温度40 ℃,固色温度60 ℃,碳酸钠质量浓度15 g/L。将经过前处理的棉织物加入40 ℃染色浴中上染10 min,并在此温度下每隔15 min加入一半硫酸钠使染料充分上染。然后升温至60 ℃,加入15 g/L的碳酸钠使染
料在纤维上固色30 min。降温后对染后的棉织物进行皂洗、水洗和烘干,染色过程曲线如图2(a)所示。
无盐少水染色体系:染料质量分数X%(X=0.5、2.0、5.0、8.0),经过前处理并在标准条件下恒温恒湿处理的棉织物2 g,浴比1︰20,带液率150%(相对于织物),染色温度40 ℃,固色温度60 ℃,碳酸钠质量分数12.5%。将溶解后的染液加入D5非水介质液中,经磁力搅拌器上搅拌使染料在D5中均匀分散,从而形成活性染料/硅基非水介质染色体系。将前处理制得的棉织物在此体系中40 ℃下上染30 min使染料充分上染,然后升温至60 ℃固色30 min。固色完成后,对染后纤维进行皂洗、水洗和烘干,染色过程曲线如图2(b)所示。
1.4 染色性能评估
1.4.1 标准曲线绘制
用电子天平称取0.100 g的活性黄145,并用去离子水定容到500 mL容量瓶。然后分别移取1、2、3、4、5、6 mL配制好的溶液于10 mL的容量瓶中,并用去离子水定容。通过紫外分光光度计测定各个质量浓度的活性黄145最大吸收波长处的吸光度,根据不同染料质量浓度与测得的吸光度的关系,制作活性黄145的标准工作曲线。
1.4.2 K/S测试
在颜色品质测色比色仪上测定染色织物K/S值。
1.4.3 上染率测试
根据先前制得活性黄145的标准工作曲线,利用染色前后染料质量浓度与吸光度的关系,上染结束后,将棉织物离心后的残液倒入染色残液中。用等量去离子水萃取出染色前后D5介质中的活性染料,定容并采用UV/Vis-2600紫外分光光度计测试吸光度。传统水浴染色取染色前后染液进行吸光度测试即可,通过残液法计算染料的上染百分率(E)。计算如下式所示:
式中:A0是初始染液的吸光度,A1是染色后残液的吸光度。
1.4.4 固色率计算
染料的固色率是染色完成后与纤维发生共价键结合的染料占投入染料总量的百分比。计算如下式所示:
式中:C1指初始染料质量浓度,mg/L;V1指初始染液体积,mL;C2指染色后残液质量浓度,mg/L;V2指染色后残液体积,mL。
1.4.5 动力学曲线的绘制
非水介质上染速率曲线的绘制:准确称取9份1 g的棉织物,并配置10份活性染料/非水介质染色液,其中染料质量分数为X%(X=0.5、2.0、5.0、8.0),无水碳酸钠的质量分数为12.5%(相对于织物),浴比1︰50。首先,将染液在恒温水浴锅中于设定的室温下保温10 min。然后,带液率为150%的棉织物分别投入染浴中进行染色,以设定的时间(0.5、1、5、10、20、40、60、80、120 min)依次将染色样取出,并用适量去离子水萃取非水介质中剩余的染料,分液定容后用紫外分光光度计测染料在最大吸收波长处的吸光度。按下式计算纤维上染料的含量qt:
qt=E×X(3)
式中:X指初始染料质量,mg。
根据式(1)计算的上染百分率及式(3)计算的纤维上染料的含量,绘制染色动力学曲线。
常规水浴上染速率曲线的绘制:棉织物的质量、份数、浴比、染色温度、染色时间与非水介质体系相同,无水碳酸钠的质量浓度为15 g/L,无水硫酸钠的质量浓度为40 g/L,配置好染液后,在恒温振荡水浴锅中保持10 min,将织物投入染液中,其余步骤同上。
2 结果与分析
2.1 染料质量浓度对染色织物染色效果的影响
为了实现棉织物在不同染料质量浓度的无盐染色,并评价染料在D5染色体系中的吸附动力学和染料与纤维的亲和力,本文对染色效果进行了分析,活性黄145标准曲线如图3所示。
由图3可知,当染料质量浓度较低时,染料溶液质量浓度与吸光度为正比关系,符合朗博-比尔定律。通过染料质量浓度与吸光度的关系计算活性染料染色后的上染率及固色率。
图4为不同染色介质中染料质量分数对棉织物染色的上染率、固色率、K/S值及ΔE的影响。活性染料本身直接性较低,因此传统水浴染色过程中需加入大量无机盐,从而降低染料与纤维之间的库仑力,进而提高染料的利用率。传统染浴中,活性黄145的固色率随染料质量分数的增高从70.8%降低到43.1%。非水介质染色体系在无盐促染条件下,上染率基本达到100%,总固着率随着染料质量分数增高仅从83.6%降至72.5%。当染料质量分数相同时,无盐促染的D5非水介质体系中染色织物的K/S值均要大于常规水浴染色织物。在染料质量分数为2%时,D5非水介质体系中染色织物的K/S值为17.4,而常规水浴染色织物的K/S值为13.6。不同染浴染色织物ΔE值均在0.5以下,匀染性较好。其中,D5非水介质染色体系中ΔE值由0.46下降到0.16,染深色织物时匀染性较佳。相较于水浴染色,活性染料/D5非水介质染色具有良好的染色效果,并且大量节省无机盐及染料的质量分数。
活性黄145在非水介质染色体系的高K/S值、高固色率应归因于四个关键点。首先,该染料含有两个活性基团,使其对棉纤维的反应性增强,可快速与棉织物表面羟基通过共价键连接[27-28]。其次,D5非水介质染色体系含水量较低,大幅地降低了染料水解[29]。再次,活性黄145的共平面较好,且含有15个共轭双键,这是赋予其与纤维的高亲和力,实现高染料固着率的重要因素,并对其与纤维的亲和力起着重要的作用[30]。最后,活性黄145含有多个水溶性基团,水溶性较好,在非水介质体系中形成的染料高质量分数条件下,染料分子受碱剂作用导致的聚集现象影响较小[31]。
由表1可知,在D5非水介质染色体系中,不同染料质量分数条件下,染色棉织物的水洗色牢度大多在4级以上,褪色色牢度均在4级以上,耐干摩擦色牢度为5级,湿摩擦色牢度大多达到4级以上,仅有8%染料染色棉织物湿摩擦色牢度和水洗色牢度为3~4级,其他各项色牢度优良。因此,活性黄145在D5非水介质染色体系中对棉织物染色的色牢度较好,均达到国标要求。
2.2 染色速率
为了进一步了解活性染料在非水介质中的扩散行为,本文探究了活性黄145在非水介质无盐少水体系和水浴体系中的染色动力学和机理。活性黄145在不同体系中吸附动力曲线如图5所示。
由图5可得,在D5非水介质染色体系,体系含水量仅为150%,相对体系含水量较少,染料溶解在水中形成高质量分数染浴,由于极性染液本身和非极性D5介质互不相容及纤维相和水浴相染料巨大的质量分数差异,染料快速扩散至纤维内部,因此活性染料无须加入任何无机盐就可以得到相对于水浴中较快的上染速率。D5非水介质染色体系中,最终上染率随时间增长而保持不变,随染料质量分数增大而增高。而水浴染色可以明显看出最终上染率在测试时间范围内,随时间增长而增大,随染料质量分数增大而增高(但质量分数高于5%时,增长趋势趋缓。
2.3 准一级反应动力学模型的拟合
吸附机理取决于吸附剂的物理和化学特性及质量传递过程[25],为了探究不同用量活性染料在D5非水介质染色体系及水浴染色体系中扩散情况,进一步提高对非水介质染色下活性染料染棉织物过程的控制及染色工艺优化的理论指导作用,本文采用准一级、准二级动力学模型对活性黄145在D5非水介质染色体系及水浴染色体系上染棉织物的试验数据进行拟合,如图6、表2所示。
准一级动力学模型可用Lagergren表示,如下式所示:
式中:qe为反应平衡时染色棉织物上染量,mg/g;qt为染色时间t时上染棉织物的染料量,mg/g;k1为一级动力学反应速率常数,min-1。
在0~t min内对式(4)进行积分,得到下式:
ln(qe-qt)=lnqt-k1t(5)
由图6及表2可知,活性染料在两种介质中的准一级动力学拟合决定系数R2较低,最低可达到0.687。且D5非水介质染色体系中R2在0.687~0.820,随着染料质量分数变化没有明显的变化趋势。而水浴中R2变化随染料质量分数增大由0.983逐渐减小为0.964,染料质量分数越大,拟合程度越差。另外,相同染料质量分数下,D5非水介质染色体系中R2均小于水浴中R2。以上研究表明,准一级动力学模型并不能准确地描述高质量分数活性染料水溶液在这两种介质中对棉纤维的上染行为。
2.4 准二级反应动力学模型的拟合
准二级动力学模型如下式所示:
式中:qe为反应平衡时纤维上活性染料的含量,mg/g;qt为染色时间t时上染棉织物的染料量,mg/g;k2为二级动力学反应速率常数,g/(mg·min)。
简化式(6)可得:
由式(7)可知,k2和qe可以直接从t/qt-t曲线的截距(b)和斜率(tanα)中计算求得,如下式所示:
则k2=1bqe,qe=1tanα。斜率越大,则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达到平衡吸附量所需的半染时间(t0.5)来表示,计算如下式所示:
由图7和表3可知,t/qt与染色时间t的拟合曲线呈明显的线性正相关关系,不同质量分数染料D5非水体系中R2在0.999以上,水浴体系R2在0.990以上。随着染料质量分数的增大,非水介质无盐少水染色体系中活性染料的最终吸附量与水浴体系最终吸附量的差距逐渐增大,8%染色时最终吸附量相差两倍以上。染料计算上染量与D5非水体系和传统水体系的染料实际上染量非常接近,进一步表明准二级动力学模型适用于描述D5非水体系和传统水体系中活性染料在棉织物上的染色动力学[32]。
对于不同的染色体系,本文研究发现D5非水体系的染料平衡上染量qe,cal、实验qe,exp和速率常数值k2均高于传统水浴染色体系。不同染色质量分数下D5非水介质体系k2均大于水浴体系k2。随着染色质量分数的增加,水浴染色半染时间t0.5从16.60下降至7.48。而D5非水介质体系t0.5显著低于水浴染色且与染料浓度相关性较小(分布在2.03~2.58),表明染料质量分数对D5非水介质体系影响较小。这是由于分散在非水介质中的高质量分数染液会因为亲纤维而憎D5介质的特性快速吸附至纤维表面[33],并向纤维内部渗透,从而导致染料的t0.5较小且与染料质量分数相关性较小。这些结果表明,活性染料在无盐少水体系中的染色速度比在传统水浴体系中的染色速度快、染料利用率高,且染色后织物的得色比较深。
3 结 论
本文研究了不同质量分数活性黄145染料在不同介质染色体系中对棉织物的染色效果、吸附平衡及染色动力学。在D5非水染色体系和传统水染色体系中,活性染料固色率及染色织物的K/S值随着染料质量分数的升高而提高。随着体系内染料量的增加,相较于传统水浴染色,非水介质无盐少水染色体系中活性染料的最终固色率降低程度更小。
与传统的水浴活性染色相比,非水介质无盐少水染色体系中活性黄145的吸收率更高(gt;95%)。此外,活性染料的固色率也较高(非水染色为72%~84%,传统染色为43%~71%),棉织物染色后颜色更深。准二级动力学模型对染料吸附过程的拟合效果最好,可以充分描述活性染料在非水染色体系和传统水染色体系中的吸附和平衡。随着染料质量分数的增大,活性黄145在水浴体系中的半染时间明显缩短,但对非水介质无盐少水染色体系半染时间影响较小。在非水染色系统中,活性染料的吸附速度明显快于传统水浴,8%染色质量分数体系中最终吸收率比传统水浴体系提高了一倍以上。在D5非水染色体系中,活性染料在25℃下的吸附平衡时间仅为5~20 min,而在传统水浴染色系统中需要更长的时间。
在D5无盐少碱非水介质少水染色体系中,除了染料组分之外,只有几种主要组分(如表面活性剂的种类、不同类型及不同质量分数的碱剂等)对其固色牢度及匀染性有着重要影响。但目前在D5非水介质染色体系中,对于这些影响因素的研究还未见报道。
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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
基金项目: 国家自然科学基金项目(22072089);安徽省重点研发项目(2023t07020001);海宁市科技计划工业、农业项目(2021003);上海市松江区科学技术攻关项目(23SJJBGS2);浙江省清洁染整技术研究重点实验室开放基金项目(QJRZ2301)
作者简介: 朱赫(1998),男,硕士研究生,研究方向为非水介质染色。通信作者:裴刘军,副教授,peilj@sues.edu.cn。