Natural polymer (cellulose)-based fabric was colored using an environmentally friendly natural dye extracted from Jalawe (Terminalia bellirica) in the preparation of Batik fabric, a cultural heritage of Indonesia that is recognized by United Nations Educational, Scientific and Cultural Organization (UNESCO). Despite the significant favorable properties in terms of functions, environmental, and cultural aspects, the combination between natural polymer-based fabric and natural dyes makes the Batik fabric an ideal medium for bacterial growth, leading to lower product quality. In the quest for a sustainable, environmentally friendly, rich-in-culture, yet durable textile, this study aimed at the functionalization of natural dye (ND)-colored Batik fabric with antibacterial ZnO nanoparticles (ZnO NPs) synthesized from Electric Arc Furnace Dust (EAFD) waste. An in situ immobilization process with a Chemical Bath Deposition (CBD) method was explored at a pH range from 6 to 11 at 50 °C. Characterization methods include XRD, XRF, FESEM, EDX, FT-IR, tensile strength measurement, agar diffusion testing, and a CIE L*a*b* scale measurement. The XRD and XRF results showed that pure (>98%) ZnO NPs were formed at pH 11 of the CBD process. FESEM results demonstrated that the pure ZnO NPs either precipitated at the CBD reactor or were immobilized on the cellulose fabric, exhibiting distinct morphology compared to the non-pure ZnO NPs. EDX elemental analysis before and after washing demonstrated the durability of the ZnO NPs attachment, in which 84% of the ZnO NPs remained on the fabric after two washing cycles (equal to 10 cycles of home laundering). The FT-IR spectra provided information on the chemical functional groups, demonstrating the success of the ZnO NPs immobilization on the cellulose fabric through Van der Waals or coordination bonding. Moreover, the in situ immobilization of ZnO NPs enhanced the Batik fabric’s tensile strength but reduced its elongation. ZnO NP-functionalized Batik fabric that was treated at pH 10 and pH 11 showed antibacterial activity against Staphylococcus aureus. The CIE L*a*b* scale results showed that the immobilization process affects the color quality of the ND-colored Batik fabric. However, based on organoleptic observations, the color of the Batik fabric that was treated at pH 11 is still acceptable for Jalawe ND-colored Batik fabric.

Blue dye (indigo) from Indigofera tinctoria leaves is a popular natural dye used worldwide. The lower light fastness of natural indigo dyes compared to that of synthetic blue dyes is one of the drawbacks of the former, limiting its utilization in the textile industry. In this study, zinc oxide nanoparticles (ZnONPs) were synthesized and characterized, and their effect on the photofading of cotton fabric dyed with natural indigo was investigated. ZnO was produced by simple precipitation. Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometry (XRD), and Brunauer–Emmett–Teller analysis were employed to characterize the composition, shape, crystallinity, size, and surface area of the resulting NPs. The optical characteristics and bandgap energy of the ZnONPs were also determined using a UV-Vis spectrophotometer. XRD and scanning electron microscopy (SEM) confirmed the synthesis of ZnONPs. The ZnONPs were applied to cotton fabrics via the dip-coating method. The transmittance of cotton coated with ZnONPs was lower than that of the uncoated sample. Photofading tests with UV-A irradiation were conducted, and the fading rate of natural indigo dye in cotton showed first-order kinetics. Overall, the synthesized ZnONPs provided excellent UV protection to reduce the photofading of cotton dyed with natural indigo.

The stability of natural dyes to the changes of pH is really necessary when the natural dyes are applied either on fabric or food. This research aimed to increase the stability of brazilein, a compound contained within the secang wood extract, to the changes of pH. The methylation process was done by reacting Dimethyl Carbonate (DMC) with the brazilein on the secang wood extract. DMC acts as a substance that substitute hydroxyl group on brazilein. The methylation reaction of brazilein on secang wood extract was operated on a three-necked round-bottomed flask fitted with mercury-sealed stirrer and reflux condenser under 80°C temperature and 250 rpm stirring speed. There were two variables observed in this research; the DMC amount ratio to the amount of secang wood extract and the time of the methylation process. The research showed that at the 1:10 the DMC amount ratio to the amount of wood extract and 8 hours of the methylation process give the better stability of color of the secang wood extract than the variation of the other variables.

The recovery process of indigoid compounds involves enzymatic hydrolysis of indigo precursors continued by oxidation reaction to synthesize indigo pigment. The purpose of this research was to evaluate the effect of physicochemical process variables, i.e., temperature, time, and pH aeration, on indigo yield from Strobilanthes cusia leaves. Small leaf pieces were immersed in distilled water and heated at temperatures (40, 50, and 60 °C) and duration (1, 2, and 3 h). The extract was aerated at different pHs (8, 10, and 12) to form the indigo product. The indigo concentration was quantified through a visible spectrophotometer and high-performance liquid chromatography (HPLC). The optimized condition for indigo production was studied using response surface methodology (RSM). Temperature, time, and interaction between temperature and time significantly affected the indigo yield. The optimized conditions for extraction of indigo dyes were determined to be at 60 °C for 1 h and pH 8 for maximizing the indigo yield. On that condition, the indigo concentration quantified by HPLC was 1.15% (w/v) which was lower than that by the spectrophotometry. By spectrophotometric analysis, the actual indigo content of 1.68% (w/v) on that optimum condition was close to the predicted indigo content of 1.77% (w/v) using RSM.