Extraction And Application Of Natural Mordant Dye Based On Water Hyacinth Containing Intrinsic Hyperaccumulating Metals

Recently,due to their renewability,environmental compatibility and biodegradability,natural dyes have received a renewed interest from researchers.Natural dyes,however,its dyeing fastness is poor when used for fiber dyeing.So it cannot bind to fibers without the application of heavy metal mordant.But the emission of residual heavy metals by mordant results in environmental pollution.Water hyacinth?Eichhornia crassipes?,one of the foreign invasive weeds,which has exuberant vitality and strong ability to reproduce,is now widely applied to wastewater treatment owing to its high bioaccumulation ability for metal ions.Water hyacinth,however,also brings serious problems because of its fast spread and congested growth.Therefore,replacing the heavy metal mordant by hyperaccumulating metals from the natural plants has great development potential.It is also a effective way for people to reduce the dependent of metal salt mordant.In this paper,natural mordant dyes of water hyacinth were extracted by using soxhlet extraction method.The corresponding process parameters were studied respectively.The extraction were separated preliminarily by thin layer chromatography and column chromatography.The characterization of functional groups and metal ions in extraction were identified with the help of 1H NMR,FTIR,UV-VIS and Inductively coupled plasma.Subsequently,the extracted dyes and every pigment band were used to dye wool.The dyeing process parameters were optimized by selecting pigment promoting force,dyeing temperature,dyeing time and p H value of dyeing bath.The color parameters and color fastness of dyed samples were tested respectively,in order to study the impact of intrinsic hyperaccumulating metals to the dyeing performance of natural mordant dye extracted from water hyacinth.The results are summarized as follows:?1?The optimum extraction process of natural mordant dyes extracted from water hyacinth by using soxhlet extraction method is as follows: anhydrous ethanol as extracting agent,solid-liquid ratio 1: 20?g/m L?,extraction temperature 65?,extracting time 2.5h.According to the mentioned optimum process,the best extraction effect can be obtained.The extraction rate of natural mordant dyes from water hyacinth is up to 7.09 wt.%.?2?One of the main ingredients in natural mordant dyes extracted from water hyacinth is anthraquinones acid natural dyes.Its chemical structure contains-Ar,-OH,-COOH,-C=O and-OR groups.Natural mordant dyes based on water hyacinth contains 8 metal elements,including Al,Ca,Fe,K,Mg,Mn,Na and Zn.Fe³⁺ and Fe²⁺ play a main mordanting role,and their content is 0.152 mg/g and 0.098 mg/g respectively.?3?The optimum dyeing process by using natural mordant dyes extracted from water hyacinth is as follows: 2%?o.w.f?.dosage of natural dyes,bath ratio 1:25,dye bath p H value of 3,and dyeing 60 min under 98?.The K/S value of dyed wool samples can reach 4.34.Ten pigments bands that separated from natural mordant dyes have great direct dyeing performance on wool.The K/S value of dyed wool samples by using the fourth dark green pigment band separated from natural mordant dyes is up to 10.51.?4?The intrinsic iron ion of the natural mordant dyes extracted from water hyacinth can greatly improve the dyeing performance.Moreover,the dyeing effect is better than that of traditional iron sulfate mordant.The-C=O and-OH groups in molecular structure of natural mordant dyes extracted from water hyacinth can form coordination compounds with the intrinsic Fe³⁺ and Fe²⁺.At the same time,Fe³⁺ and Fe²⁺ can form coordination compounds with the-C=O and-OH of fibers.The dye molecules can bind to fibers with Fe³⁺ and Fe²⁺,and the dyeing effect is enhanced.?5?The results show that soaping fastness of the dyed wool samples by using natural mordant dyes extracted from water hyacinth can reach grade 4,the light fastness of the dyed wool samples can reach grade 4.5,and the rubbing fastness and perspiration fastness of the dyed wool samples can reach grade 5.Each dyeing fastness shows relatively high level.As a result,water hyacinth is expected to act as a new biomass resource of natural mordant dyes.