Extraction, Separation, Identification and Application of Natural Pigments from Water Hyacinth
|Keywords||water hyacinth natural pigment extraction separation identification dyeing|
Synthetic pigments play a primary role in textile processing due to their bright colors, complete chromatography color range, good washing and ligh fastnesses, etc. However, with the improvement in the living standard and increasing deterioration in environment, there is a growing focus on the safety and environmental issues. The disadvantages of synthetic pigments are growing problems. For example, raw materials derive from natural gas, oil and coal and other non-renewable fossil resources; dyeing wastewater treatment is hard; some synthetic pigments intermediates are harmful for human health. As a result, some countries have issued disabled regulations as to the application of synthetic pigments recently. Natural pigments derive from nature, and they have excellent environmental compatibility, biodegradability, and renewability. Additionally, some natural pigments exhibit pharmacological effects such as sterilization, detoxification, anti-inflammatory and ultraviolet resistance. Thus, natural pigment attracted renewed attention of researchers. But natural pigments also have disadvantages, such as instable source, high cost, etc. So it is important to explore new sources, which are cheap, easy for getting natural pigments.In this paper, water hyacinth, one of the worst weed species in our country, are used as raw material of natural pigments to be extracted. First, the solvent extraction, ultrasonic extraction and soxhlet extraction methods were adopted to extract pigments, and the corresponding process are studied respectively. Second, alkali resistance, acid resistance, heat resistance and light resistance of the extracted pigments were discussed. Third, the extraction were separated and purified by column chromatography and thin layer chromatography, and then were identified by chemical reaction, UV-VIS, FTIR, and mass spectrometry. Finally, Nylon and wool were dyed by the extracted pigments without mordant. The dyeing samples were compared to corresponding mordant dyeing fabric respectively. The main results are summarized as following:(1) The optimum process parameters of solvent extraction method are as follows:extraction time6h, material ratio lg/15ml, temperature85℃, twice extraction. The optimum process parameters of ultrasonic extraction method are as follows:material ratio lg/15ml, extraction time90min, temperature35℃, ultrasonic power80W and three times extraction. The optimum process parameters of soxhlet extraction method are as follows:material ratio lg/15ml, extraction time90min and one extraction. The extraction efficiency of natural pigments by different methods are3.59%,4.01%and4.26%respectively under the optimum process parameters(2) Extraction shows good color stablity when pH value is from3to10. When pH is above7, hyperchromic effect occurs. When pH is below7, hypochromic effect appears. When processing temperature is no more than100℃, the heat resisting property of extraction is good, but the lightfastness is poor.(3) There are seven pigments bands observed after column chromatography isolation. The first, the second and the fourth pigment bands are relatively high purity compounds. The main components of these seven pigments bands are cis-β-carotenoids, pheophytin a, pheophytin b, chlorophyll derivatives, chlorophyll a, chlorophyll b, and lutein respectively. The quality percentage of pheophytin-a in the extracted pigments is up to28%. And that of carotenoids in the extracted pigments is about9%.(4) The optimum mordant-free dyeing conditions for nylon fabric are as follows:dyeing time40min, dyeing temperature98β, pH value3, liquor dyeing dosage2%(o.w.f.), bath ratio1:30, the K/S value of dyed samples is near15. The rubbing fastness and washing fastness of dyeing samples show4grade or even higher, but built-up property is poor.(5) The optimum mordant-free dyeing conditions for wool fabric are as follows:dyeing temperature98℃, dyeing time40min, pH value3, bath ratio1:20. The rubbing fastness and washing fastness of dyeing samples show4grade or even higher, and their built-up property is relatively good. The dyeing results of direct dyeing are better than that of the mordant dyeing.