Ultrasound for low temperature dyeing of wool with acid dye

Effect of ultrasound power on HCl leaching kinetics of impurity removal of aphanitic graphite

This study aimed to investigate the effect of ultrasonic power and temperature on the impurity removal rate during conventional and ultrasonic-assisted leaching of aphanitic graphite. The results showed that the ash removal rate increased gradually (∼50 %) with the increase in ultrasonic power and temperature but deteriorated at high power and temperature. The unreacted shrinkage core model was found to fit the experimental results better than other models. The Arrhenius equation was used to calculate the finger front factor and activation energy under different ultrasonic power conditions. The ultrasonic leaching process was significantly influenced by temperature, and the enhancement of the leaching reaction rate constant by ultrasound was mainly reflected in the increase of the pre-exponential factor A. Ultrasound treatment improved the efficiency of impurity mineral removal by destroying the inert layer formed on the graphite surface, promoting particle fragmentation, and generating oxidation radicals. The poor reactivity of hydrochloric acid with quartz and some silicate minerals is a bottleneck limiting the further improvement of impurity removal efficiency in ultrasound-assisted aphanitic graphite. Finally, the study suggests that introducing fluoride salts may be a promising method for deep impurity removal in the ultrasound-assisted hydrochloric acid leaching process of aphanitic graphite.

A review of plant-based natural dyes in leather application with a special focus on color fastness characteristics

Dyes/colorants are normally used to improve the aesthetic of consumer products, and leather is one of them. The leather industry plays a significant role in the global economy. However, the leather-making process causes severe environmental pollution. Synthetic dyes are one of the major classes of leather chemicals that are responsible for the enhanced pollution load created by the industry. Over the years, excessive use of synthetic dyes in consumer products created severe environmental pollution and health hazard. Many of these synthetic dyes are carcinogenic, allergic, cause serious health problems for human beings, and have been restricted by regulatory authorities for use in consumer goods. Since ancient days, natural dyes and colorants have been used to make lives colorful. Amid the green movements and environment-friendly products/processes, natural dyes are back to mainstream fashion. Moreover, natural colorants have become a trend due to their eco-friendly nature. The demand for non-toxic and eco-friendly dyes and pigments is increasing. However, the question remains "is natural dyeing sustainable" or "how to make it sustainable." Here, we review the literature reports on natural dye's application in leather in the last two decades. This review article provides a detailed overview and current knowledge base on the various plant-based natural dyes used in leather dyeing, their fastness properties, and the need of the hour in terms of product and process development to make natural dying sustainable. The color fastness characteristics of the dyed leather to light, rub, and perspiration have been critically discussed.

Effect of ultrasound on protein functionality

The review focus on the effect of ultrasound on protein functionality. The presence of transient ultrasonic mechanical waves induce various sonochemical and sonomechanical effects on a protein. Sonochemical effects include the breakage of chains and/or the modification of side groups of aminoacids. Sonomechanical modifications by enhanced molecular agitation, might lead to the transient or permanent modification of the 3D structure of the folded protein. Since the biological function of proteins depends on the maintenance of its 3D folded structure, both sonochemical and sonomechanical effects might affect its properties. A protein might maintain its 3D structure and functionality after minor sonochemical effects, however, the enhanced mass transfer by sonomechanical effects might expose internal hydrophobic residues of the protein, making protein unfolding to an irreversible denatured state. Ultrasound enhanced mass transport effects are unique pathways to change the 3D folded structure of proteins which lead to a new functionality of proteins as support shield materials during the formation microspheres. Enzymes are proteins and their reactions should be conducted in a reactor set-up where enzymes are protected from sonic waves to maximize their catalytic efficiency. In this review, focused examples on protein dispersions/emulsions and enzyme catalysis are given.

Algal and cyanobacterial biomass as potential dye biodecolorizing material: a review

The considerable demand for dyes worldwide has triggered a surge in their production globally. The extensive application of dyes and inefficient dyeing processes has elevated the risk of environmental pollution. The effluents from dying industries contain toxic compounds that are dreadful to both the environment and living beings. Besides, conventional effluent treatment processes have proved ineffective in clearing the dye from the effluent. The sole way of tackling this problem would be by applying a more rational approach that would be sustainable and efficient. After a thorough study of the literature, we are convinced to say that cyanophyceae and algae could serve as one of the promising biodecolorizing agents substituting most other biosorbents used in conventional biological effluent treatment technology. To evidence this we compiled data from the literature, wherein, various algal biomasses capable of decolorizing dye effluents have been examined. This paper also gives comprehensive facts on the mechanism of decolorization, pretreatment, influencing factors, and toxicity of treated products.

Effect of Ultrasound on the Oxidative Copper Leaching from Chalcopyrite in Acidic Ferric Sulfate Media

The objective of this study is to compare the reaction kinetics of copper leaching from chalcopyrite in acidic ferric sulfate media with (UAL) and without (non-UAL) ultrasound assistance. Four leaching parameters were evaluated and optimized. The parameter with the strongest effect was temperature, followed by ultrasonic power, the solid-to-liquid ratio (S/L), and acid concentration. Copper recovery showed an increase with rising temperatures in both systems. Ultrasonic power had a positive effect on copper leaching, but no significant difference was found among various power amplitudes. Copper extraction increased with decreasing S/L. At 0.1% S/L, the UAL leaching rate was double the non-UAL leaching rate. In both systems, acid concentration had little effect on copper extraction. Under optimized conditions, 20% amplitude power, 1% S/L, 0.5 M acid, and 80 °C leaching temperature, copper extraction was 50.4% and 57.5% in the non-UAL and UAL treatments, respectively. Ultrasonic waves enhanced the leaching rate, shortened the reaction time, and reduced acid consumption. Analysis of the rate-controlling step using a shrinking core model showed that leaching occurs after diffusion through the product layer but also chemical controlled in both non-UAL and UAL systems. The leaching mechanism was confirmed by characterizing the chalcopyrite and leached residue with X-ray diffraction and scanning electron microscopy/energy dispersive X-ray spectroscopy.

Build-up of a continuous flow pre-coated dynamic membrane filter to treat diluted textile wastewater and identify its dynamic membrane fouling

This research built up a continuous dynamic flow filter membrane to treat diluted textile wastewater and basically investigated dynamic membrane fouling mechanism. By pre-depositing particles activated carbon (PAC) on membrane support material (MSM), a thin layer was formed on its surface, which showed excellent results in removing organic pollutants from diluted textile wastewater. Experimental data were regressed by the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich (D-R) and Sips isotherm models. The three two-parameter isotherms (Temkin, D-R and Freundlich) were the models that best fitted, with respectively 0.977, 0.975 and 0.973 regression coefficients. D-R model has registered the maximum calculated adsorption capacity Q_{md, cal.} = 45.499 mg/g and the mean energy which was required to adsorb 1 mol of MB dye by the DM layer E = 4.249 kJ/mol; indicating the energy distribution onto heterogeneous surface of a physical adsorption process. Furthermore, kinetic models results showed that MB adsorption onto PAC at different initial concentrations follows the pseudo-second order. The obtained results also indicated that a flexible DM layer with different thickness can be formed from different amount of PAC pre-deposited on MSMs, which demonstrated that it was convenient to adjust the required DM thickness to filtrate a known initial concentration for >99% organic pollutants removal efficiency rate. However, DM fouling occurred on small pores MSMs; which resulted in an increase of the filtration pressure what have affected the filtration performance. PAC and MSMs surface morphology and texture structure, before and after filtration, were visualized respectively by Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infra-Red and Attenuated Total Reflectance (FTIR/ATR). From these experimental results, a sustainable flux (>6.85 × 10^-5 m/s) was established to discriminate no fouling from fouling conditions based on flux and TMP trends variance.

Dopamine-Dyed and Functionally Finished Silk with Rapid Oxidation Polymerization

Nowadays, more and more attention has been paid to ecological environment problems, and the dyeing and finishing field is no exception. Environmentally friendly dyeing and finishing methods have been extensively studied. Inspired by the bioadhesive force of marine mussels, dopamine (DA) was applied as a dyestuff and investigated in textile dyeing. In this work, dopamine was dyed on silk with a rapid oxidation polymerization in the presence of metal ions (Fe3+) and sodium perborate oxidant (Ox). The polydopamine (PDA) was rapidly deposited on silk fabric and the dyeing process was optimized as follows: the concentration of DA was 2 g·L-1, and that of Fe3+ was 2 mmol·L-1; the total reaction time was 50 min and reacted at 50 °C; 9 mmol·L-1 Ox was added at 20 min. The K/S value of the treated silk fabric reached 11.46. The color fastness of dyed fabric to light fastness reached Level 4. The SEM and AFM tests showed that the particles attached to the fabric surface and increased the roughness. The XPS test further proved that polydopamine (PDA) was deposited on the fabric. The treated fabric also had a good anti-UV property with a UPF >30 and UVA <4%. The water contact angle of treated fabric attained 142.6°, showing better hydrophobicity, and the weft breaking strength was also improved. This environmentally friendly dyeing and finishing method can be applied and extended to other fabrics.

Effect of sonochemical scouring on the surface morphologies, mechanical properties, and dyeing abilities of wool fibres

Ultrasonics has the potential to reduce the cost and environmental impact of textile processing. This work investigates the effects of ultrasonic irradiation during wool scouring on fibre surface morphologies, fibre mechanical properties, and fibre dyeing abilities. A range of ultrasonic frequencies were used in the scouring bath to examine the forms of fibre cuticle damage. It is observed that wool fibres underwent ultrasonic irradiation at a low frequency have severe modifications of the fibre surface structure. Despite some visible disruptions to the fibre scale structure however, ultrasonic irradiation has shown a negligible impact on the fibre mechanical properties, especially bending abrasion resistance which depends largely on the fibre surface conditions, and is responsible for the handle and pilling propensity of the resultant fabrics. Dyeing abilities were investigated on wool samples using commercially available acid dye and reactive dye. It is found that ultrasonically scoured wool has a quicker dye uptake in the early stage of low temperature dyeing for both acid dye and reactive dye, than the conventionally scoured wool.

Ultrasound energy to accelerate dye uptake and dye-fiber interaction of reactive dye on knitted cotton fabric at low temperatures

Acoustic cavitation formed due to propagation of ultrasound wave inside a dye bath was successfully used to dye cotton fabric with a reactive dye at lower temperatures. The energy input to the system during sonication was 0.7 W/cm(2). This was within the energy range that contributes towards forming cavitation during ultra-sonication. The influence of ultrasound treatment on dye particle size and fiber morphology is discussed. Particle size analysis of the dye bath revealed ultra-sonication energy was capable of de-agglomeration of hydrolyzed dye molecules during dyeing. SEM micrograph and AFM topographical image of the fiber surface revealed fiber morphology remains unchanged after the sonication. The study was extended in understanding the contribution of ultrasound method of dyeing towards achieving good color strength on the fabric, compared to the normal heating method of dyeing. Study showed color strength obtained using ultra sound method of dyeing is higher compared to normal heating dyeing. Ultrasound energy was able to achieve the good color strength on cotton fabric at very low temperature such as 30 °C, which was approximately 230% more than the color strength achieved in normal heating method of dyeing. This indicates that energy input to the system using ultrasound was capable of acting as an effective alternative method of dyeing knitted cotton fabrics with reactive dye.

A review on textile sonoprocessing: a special focus on sonosynthesis of nanomaterials on textile substrates

The chemical and physical effects of ultrasound with a frequency above 16kHz, higher than the audible frequency of the human ear, have proven to be a useful tool for variety of systems ranging from the application of ultrasound in environmental remediation to the cooperation of ultrasound waves with chemical processing regarding as sonochemistry. Ultrasound opened up new advances in textile wet processing including desizing, scouring, bleaching, dyeing, printing and finishing and also nanoprocessing including nanopretreatment, nanodyeing, nanoprinting and nanofinishing. Use of ultrasound appears to be a promising alternative technique to reduce energy, chemicals and time involved in various operations. Over the past years there has been an enormous effort on using sonochemistry for the synthesis of nanomaterials on various textile materials. In situ sonosynthesis of nanoparticles and nanocomposites on different textiles is a pioneering approach driving future investigations. With such wide range of applications and vast ever increasing publications, the objective of this paper is presenting a comprehensive review on ultrasound application in textile from early time to now by the main emphasis on the sonosynthesis of nanomaterials outlining directions toward future research.

Ultrasound-assisted dyeing of cellulose acetate

The possibility of reducing the use of auxiliaries in conventional cellulose acetate dyeing with Disperse Red 50 using ultrasound technique was studied as an alternative to the standard procedure. Dyeing of cellulose acetate yarn was carried out by using either mechanical agitation alone, with and without auxiliaries, or coupling mechanical and ultrasound agitation in the bath where the temperature range was maintained between 60 and 80 °C. The best results of dyeing kinetics were obtained with ultrasound coupled with mechanical agitation without auxiliaries (90% of bath exhaustion value at 80 °C). Hence the corresponding half dyeing times, absorption rate constants according to Cegarra-Puente modified equation and ultrasound efficiency were calculated confirming the synergic effect of sonication on the dyeing kinetics. Moreover the apparent activation energies were also evaluated and the positive effect of ultrasound added to mechanical agitation was evidenced by the lower value (48 kJ/mol) in comparison with 112 and 169 kJ/mol for mechanical stirring alone with auxiliaries and without, respectively. Finally, the fastness tests gave good values for samples dyed with ultrasound technique even without auxiliaries. Moreover color measurements on dyed yarns showed that the color yield obtained by ultrasound-assisted dyeing at 80 °C of cellulose acetate without using additional chemicals into the dye bath reached the same value yielded by mechanical agitation, but with remarkably shorter time.