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High chemical oxygen demand (COD) and a strong color, which primarily originates from desizing and dyeing operations, are two major removal objectives in textile wastewater treatment. In this study, crosslinking-induced precipitation via the covalent bonding between –OH groups of PVA and vinyl sulfone groups of reactive dyes is proposed to simultaneously remove poly(vinyl alcohol) (PVA) and reactive dyes. Due to the nucleophilic addition reaction under an alkaline condition, PVA polymers can be efficiently crosslinked by dye molecules and destabilized in the presence of alkali and Na2SO4. Additionally, due to the high coagulation efficiency under the alkaline conditions, MgSO4 was used as a coagulant to facilitate the removal of the residual color after precipitation. After a two-step process, whereby coagulation was followed by crosslinking-induced precipitation, the maximum efficiencies of the removal of COD, PVA, and color attained 88.9%, 86.3%, and 99.2%, respectively, when the PVA monomer/RB5 mole ratio was 400. We hope that this technically feasible, highly efficient, and cost-effective process provides a basis for the practical application of the simultaneous treatment of desizing and dyeing wastewater.

Conjugated organic polymers (COP) are fundamental for the future development of electrochromic devices. Despite the progress of composite materials, the electrochromic performance of pristine COP is still limited by dense three-dimensional (3D) structure. This work reports the fabrication of high optical contrast polyaniline (PANI) films with fast switching speed by electrochemical polymerization. Benefitting from the stereo-structure and size of p-toluenesulfonic acid (pTSA), highly oriented lamellar polyaniline with nanoscale large inter-layer spacing and a disordered in-plane structure is obtained. These structural factors simultaneously improve ion diffusion capability and optimise reaction area, resulting in a high optical contrast of above 70% at a wavelength of 720 nm, a fast response time (0.8 s for coloring and 4.2 s for bleaching), and remarkable coloration efficiency (328.5 cm2 C−1). In addition, the pTSA-PANI quasi-solid-state electrochromic device displayed good electrochromic performance with optical contrast of 82%, suggesting an inherent suitability for use in electrochromic fields. Furthermore, the synthetic method developed here represents a new and simple technique to modulate photoelectronic properties.

The necessity of optical waveguides with low-loss light guiding of biomedical devices is driving increasing demands for development of biocompatible photonic components. Spider silks have extraordinary mechanical properties; thus, the design of high-performance artificial silk fibers as optical waveguides for low-loss light guiding has been one of the focuses of researches in the field of biomimetic fibers. In this study, regenerated silk fibroin (RSF)/cellulose nanofibers (CNF) hybrid fibers were wet-spun through a microfluidic channel that mimics the shape of spider’s major ampullate gland. The generated RSF/CNF fibers with high crystallinity, high mesophase content and small crystallite size, thus showed a low light loss of 1.0 dB/cm, which was much lower than that of degummed-silk and most commercial waveguides. Additionally, the fibers had high sound velocity and was knittable. The break strength of the RSF/CNF fiber containing 5 wt% CNF was as high as 710 ± 33 MPa, which was significantly higher than that of silkworm silk fiber. The developed optical waveguides had high performance, biocompatibility, biodegradability, flexibility, and toughness, thus may be suitably applied in biological media, biophotonics and brain-machine interfaces.

Unlike the removal of chromium (Cr) ions, the efficient treatment of Cr complexes with organic ligands is a challenging issue in wastewater treatment. The generation and accumulation of highly toxic Cr(VI) species should be minimized. In this study, well-dispersed Cu2O and Fe3O4 nanoparticles inlaid in chitosan beads were prepared. This catalyst demonstrated dual functions, i.e., catalytic oxidation of Cr(III)-organic complexes and efficient inhibition of Cr(VI) accumulation in the presence of H2O2. More than 85% of the Cr(III)-organic complexes were removed in a wide pH range and a negligible amount of Cr(VI) remained in solution in the presence of 20 mmol/L H2O2. The synergistic effect of Cu2O, Fe3O4, and the chitosan matrix was the key factor for the ligand disruption and Cr removal. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analysis were used to determine the underlying mechanism. The results showed that the generated Cu+ species of Cu2O transferred electrons to accelerate the Fe(III)/Fe(II) cycle during the Fenton reaction, which favored the production of OH radicals. The generated Cr(VI) in the Fenton-like reaction was efficiently adsorbed by chitosan and reduced to Cr(III) by chitosan and Cu2O. The reduced Cr(III) was then incorporated into the surface structure of Fe3O4 and generated a stable complex oxides of Fe and Cr(III). Overall, this paper demonstrated a new method for the treatment of Cr(III)-organic complexes from wastewater.