Wastewater recovery is one of the most pressing contaminant-related subjects in the textile industry. Many cleaning and recovery techniques have been applied in recent decades, from physical separation to chemical separation. This work reviews textile wastewater recovery by focusing on natural or synthetic nanoclays in order to compare their capabilities. Presently, a wide variety of nanoclays are available that can adsorb substances dissolved in water. This review summarizes and describes nanoclay modifications for different structures (laminar, tubular, etc.) to compare adsorption performance under the best conditions. This adsorbent capacity can be used in contaminant industries to recover water that can be used and be recontaminated during a second use to close the production circle. It explores and proposes future perspectives for the nanoclay hybrid compounds generated after certain cleaning steps. This is a critical review of works that have studied adsorption or desorption procedures for different nanoclay structures. Finally, it makes a future application proposal by taking into account the summarized pros and cons of each nanoclay. This work addresses contaminant reuse, where part of the employed dyes can be reused in printing or even dyeing processes, depending on the fixing capacity of the dye in the nanoclay, which is herein discussed.

In the present work, anthocyanin (ACN) hybrid nanopigments were synthetized by using a natural pomegranate dye (PD) and calcined hydrotalcite (HT) and montmorillonite (MMT) nanoclays. A wide colour gamut was obtained with MMT-based nanopigments ranging from reddish to bluish hues caused by structural transformations of ACNs at different pH values. However, a buffer effect was observed with HT obtaining samples a similar final colour regardless of the synthesis conditions. Nanopigments added with a biomordant extracted from pomegranate peels showed a different colour compared to the incorporation of a commercial mordant due to the intrinsic colouring properties of the pomegranate bioadditive. The developed nanopigments were incorporated at 7 wt% loading to produce novel polyester-based bionanocomposites which were characterized in terms of thermal, mechanical and colour properties. The encapsulation of PD into the nanoclays improved its thermal stability, in particular for MMT-based nanopigments. The pH changes observed during the nanofillers synthesis affected the final colour of the MMT-based nanocomposites, inducing a general increase in ∆E* and a decrease in gloss values. Slight improvements were obtained in terms of elastic modulus for MMT-based polymer samples confirming the applicability of the developed bionanocomposites as colouring and reinforcement materials. A very similar environmental profile was obtained for MMT and HT-based nanofillers showing MMT-based nanopigments a slightly better general behaviour. The results of the LCA study evidenced the suitability of the processes used in this work to the circular bioeconomy approach through sustainable food waste management and the production of bioplastics using waste substrates.

In order to consider 3D objects from suitable Fused Deposition Modelling (FDM) printers as prototypes for the automotive sector, this sample must be able to reproduce textural effects (sparkle or graininess) or metallic or gonio-appearance to reinforce the attractive appeal of these materials. This study worked with two different commercial filaments: grey metallic PLA (poly(lactic acid)) and ABS (acrylonitrile-butadiene-styrene copolymer) with diffractive pigments. For both materials, a statistical design of experiments (DoE) was carried out to find the printing parameters effect on the final 3D-objects gonio-appearance. The selected printing parameters were printing speed (2 levels), layer height (2 levels) and sample thickness (3 levels). Twelve smooth square objects were printed from each material. The ABS-diffractive filaments achieved the most significant flop and higher sparkle values than metallic PLA. Graininess was high when working with PLA filaments instead of ABS. Layer height was the most significant parameter to maximize PLA objects’ flop or sparkle effects. The best result was found when printing at 0.1 mm. For the ABS samples, the stronger flop and sparkle effects were achieved with the 50 mm/s printing speed, the 0.1 mm layer height and the lowest thickness level. This study shows the methodology to study the printing parameters effects and interactions to maximize the FDM-3D-objects gonio-appearance.

In this work, polyester-based nanocomposites added with laminar nanoclays (calcined hydrotalcite, HT, and montmorillonite, MMT) loaded with lemon waste natural dye (LD) and essential oil (LEO) were prepared and characterized. The optimal conditions to synthetize the hybrid materials were obtained by using statistically designed experiments. The maximum LD adsorption with HT was found using 5 wt% of surfactant (sodium dodecyl sulfate), 5 wt% of mordant (aluminum potassium sulfate dodecahydrate) and 50% (v/v) ethanol. For MMT, 10 wt% of surfactant (cetylpyridinium bromide), 5 wt% of mordant, 1 wt% of (3-aminopropyl) triethoxysilane and 100% distilled water were used. LEO adsorption at 300 wt% was maximized with MMT, 10 wt% of surfactant and 50 °C following an evaporation/adsorption process. The obtained hybrid nanofillers were incorporated in a polyester-based matrix (INZEA) at different loadings (3, 5, and 7 wt%) and the obtained samples were characterized in terms of thermal stability, tensile behavior, and color properties. HT_LEM-based samples showed a bright yellow color compared to MMT_LEM ones. The presence of lemon hybrid pigments in INZEA-based systems produced a remarkable variation in CIELAB color space values, which was more visible with increasing the nanofillers ratio. A limited mechanical enhancement and reduced thermal stability was observed with the nanopigments addition, suggesting a limited extent of intercalation/exfoliation of MMT and HT in the polymer matrix. MMT_LEM pigments showed higher thermal stability than HT_LEM ones. A significant increase in Young’s modulus of nanocomposites loaded with hybrid LEO was observed compared to the biopolymer matrix. The LEO inclusion into the nanoclays efficiently improved its thermal stability, especially for MMT.

Interest in applications of natural dye applications has increased because of their antibacterial properties and the possibility of extracting them from nature and residues. Using nanoclays as hosts to reinforce natural dye properties has been successfully demonstrated. However, no one has attempted to optimize the polymer matrix and hybrid pigment properties at the same time to ensure the best final properties for bio-composite applications. Using a statistical design for experiments, we propose the best combination of modifiers with the best nanoclay as the host of three natural dyes: chlorophyll, β-carotene, and betanine. Using the L9 Taguchi designs, we learned both the influence of the nanoclay structure, and the addition moment of surfactant, mordant salt, and silane modifiers. FTIR, XRD, DTG, integration sphere spectrophotometer, and UV-aging tests were used to characterize the hybrid pigments and epoxy bioresin composites. The degradation temperatures of the three natural dyes rose and the reinforcement of the stability of three natural dyes to UV–Vis radiation exposure was demonstrated, which avoided the migration of these dyes from bioresin to wet ribbing. Optimal results were obtained with hydrotalcite clay (calcined or not) by using surfactant and mordant before the natural dye, and before or after silane.