Urchin-like CO2-responsive magnetic microspheres for highly efficient organic dye removal.

CO2-responsive materials have emerged as promising adsorbents for the remediation of refractory organic dyes-contaminated wastewater without the formation of byproducts or causing secondary pollution. However, realizing the simultaneous adsorption-separation or complete removal of both anionic and cationic dyes, as well as achieving deeper insights into their adsorption mechanism, still remains a challenge for most reported CO2-responsive materials. Herein, a novel type of urchin-like CO2-responsive Fe3O4 microspheres (U-Fe3O4 @P) has been successfully fabricated to enable ultrafast, selective, and reversible adsorption of anionic dyes by utilizing CO2 as a triggering gas. Meanwhile, the CO2-responsive U-Fe3O4 @P microspheres exhibit the capability to initiate Fenton degradation of non-adsorbable cationic dyes. Our findings reveal exceptionally rapid adsorption equilibrium, achieved within a mere 5 min, and an outstanding maximum adsorption capacity of 561.2 mg g-1 for anionic dye methyl orange upon CO2 stimulation. Moreover, 99.8% of cationic dye methylene blue can be effectively degraded through the Fenton reaction. Furthermore, the long-term unresolved interaction mechanism of organic dyes with CO2-responsive materials is deciphered through a comprehensive experimental and theoretical study by density functional theory. This work provides a novel paradigm and guidance for designing next-generation eco-friendly CO2-responsive materials for highly efficient purification of complex dye-contaminated wastewater in environmental engineering.

Breathable, Antibacterial, and Biocompatible Collagen Fiber Network Decorated with Zwitterionic Silver Nanoparticles for Plantar Pressure Monitoring.

Foot plantar pressure monitoring and gait analysis are of great significant in footwear design, sport biomechanics, injury prevention, and early warning of disease. Flexible and wearable smart insoles pave a feasible way for these application scenarios. However, the majority of the currently developed smart insoles are composed of synthetic polymers (e.g., plastics, rubbers, etc.), leading to inevitable problems associated with air permeability, hygiene condition, biocompatibility, and wearing comfort. Here, a new paradigm of a natural collagen fiber network (CFN) with soft and breathable features, which can be obtained by facilely treating animal hides via conventional leather pretreatment process, is selected as substrate material for constructing smart insoles due to its high permeability and porosity. Further, biocompatible zwitterionic silver nanoparticles (AgNPs) with both carboxybetaine and catechol groups on the interface were designed for firmly and uniformly immobilization onto the hierarchical micro-/nanoscale fibers of CFN through mussel-inspired catechol/amino chemistry, giving rise to both good antibacterial property and pressure sensing capability of the resultant material. The finally developed smart insole by using the AgNPs decorated CFN exhibits good capability for plantar pressure mapping and gait feature analysis. Especially, the smart insole will be very suitable for pressure monitoring and gait analysis of a diabetic foot with sensitive skin that requires a high biocompatible and antibacterial environment.

Polyphenol modified natural collagen fibrous network towards sustainable and antibacterial microfiltration membrane for efficient water disinfection.

Because of their low-cost and high bacterial interception efficiency, large-scale membrane separation technologies like microfiltration (MF) have been widely implemented for water disinfection. However, lack of antibacterial ability and low sustainability are two major drawbacks of most petroleum-based MF membranes, which are normally associated with hazardous issues including biofouling and nonbiodegradable waste. In this work, abundant animal hides, which are by-products of the meat processing industry, were proposed as raw materials to fabricate a sustainable MF membrane due to their natural, hierarchical, and renewable collagen fibrous network (CFN) with inherent biodegradability. After the removal of non-collagen compositions from animal hides, such as hair and fat, through a facile pretreating process base on green chemistry principles, a thin CFN based membrane (CFN-M) with a similar micropore size to that of commercial MF membranes could be produced. Furthermore, inspired by conventional leather tanning technology, tannic acids (TA) were selected as plant polyphenol tanning agent to modify collagen fibers based on tanning chemistry to improve the thermal stability of CFN-M. Moreover, the TA cross-linked CFN-M (TA@CFN-M) exhibited excellent antibacterial properties due to the production of reactive oxygen species (ROS) by the catechol functional group. The resulting TA@CFN-M achieved >99.9% water disinfection efficiency with a flux of ∼150 L m-2 h-1 via gravity-driven operation, while simultaneously showing admirable anti-biofouling ability. Different from the commercial MF membrane, based on the green chemistry principle, this work may shed light on designing new sustainable and antibacterial membranes for anti-biofouling water disinfection.

Hierarchical collagen fibers complexed with tannic acid and Fe3+ as a heterogeneous catalyst for enhancing sulfate radical-based advanced oxidation process.

Efficient sulfate radical-based advanced oxidation processes (SR-AOPs) are important for treating organic contaminants of industrial wastewater. To achieve this goal, tannic acid (TA)-modified skin collagen fibers (CFs) were prepared for the enhanced immobilization of Fe3+ based on multiple complexation interactions, resulting in a heterogeneous catalyst with more catalytic sites (defined as TA-Fe-CFs) for activating peroxymonosulfate (PMS). During the removal of an organic dye (rhodamine B, RhB) from water, the hierarchical TA-Fe-CFs exhibited excellent adsorption capacity at the early stage before the introduction of PMS, which can be ascribed to the π-π interaction between TA and aromatic RhB. Such improved mass transfer of target contaminants into the catalytic support was proved to be beneficial for improving the utilization efficiency of sulfate radicals in subsequent SR-AOPs. After introducing PMS, the reductive TA moieties of the heterogeneous catalyst were able to accelerate the redox cycle of Fe3+/Fe2+ in Fenton reactions, facilitating the activation of PMS to generate sulfate radicals for the degradation of organic RhB.

Mussel-inspired surface functionalization of polyamide microfiltration membrane with zwitterionic silver nanoparticles for efficient anti-biofouling water disinfection.

Mature microfiltration (MF) membrane is a low-cost, effective, and promising technology to provide affordable purified water for people living in developing countries. However, the lack of disinfection ability and inherent membrane fouling problems have seriously restricted the large-scale application of conventional MF treatment system in producing safe drinking water. In this work, zwitterionic silver nanoparticles (AgNPs) with surface modification of poly(carboxybetaine acrylate-co-dopamine methacryamide) (PCBDA) copolymers were robustly immobilized onto commercial polyamide MF membrane via mussel-inspired chemistry for water disinfection. The designed microfiltration membrane, named as PCBDA@AgNPs-MF, exhibited integrated properties of high and stable payload of AgNPs, broad-spectrum anti-adhesive and antimicrobial activities, and easy removal of inactivated microbial cells from membrane surface. Ascribing to the synergetic effect of anti-adhesive and antimicrobial features brought by zwitterionic PCBDA@AgNPs, the biofilms growth on polyamide membrane surface was significantly inhibited, which showed potential access to achieve long-term biofouling resistance and maintain water flux for conventional MF membrane. As water disinfection device, these attributes enabled PCBDA@AgNPs-MF to effectively disinfect the model and natural bacteria-contaminated water.

Facile and Scalable Fabrication of Antibacterial CO2-Responsive Cotton for Ultrafast and Controllable Removal of Anionic Dyes.

A novel CO2-responsive cotton as an eco-friendly adsorbent derived from poly(4-acryloyloxybenzophenone-co-2-(dimethylamino) ethyl methacrylate) and cotton was fabricated via a facile and fast dip-coating method. As expected, upon CO2 stimulation, the protonated cotton presented CO2-induced "on-off" selective adsorption behaviors toward anionic dyes owing to electrostatic interactions. The adsorption isotherms and kinetics of the CO2-responsive cotton toward anionic dyes obeyed the Langmuir isotherm and pseudo-second-order kinetics models, respectively. It is noteworthy that the CO2-responsive cotton exhibited high adsorption capacity and ultrafast adsorption rate toward anionic dyes with the maximum adsorption capacities of 1785.71 mg g-1 for methyl orange (MO), 1108.65 mg g-1 for methyl blue (MB), and 1315.79 mg g-1 for naphthol green B (NGB), following the adsorption equilibrium times of 5 min for MO, 3 min for MB, and 4 min for NGB. Moreover, the CO2-responsive cotton also exhibited high removal efficiency toward anionic dyes in synthetic dye effluent. Additionally, the CO2-responsive cotton could be facilely regenerated via heat treatment under mild conditions and presented stable adsorption properties even after 15 cycles. Finally, the as-prepared CO2-responsive cotton exhibited outstanding antibacterial activity against E. coli and S. aureus. In summary, this novel CO2-responsive cotton can be viewed as a promising eco-friendly adsorbent material for potential scalable application in dye-contaminated wastewater remediation.

Robust immobilization of anionic silver nanoparticles on cellulose filter paper toward a low-cost point-of-use water disinfection system with improved anti-biofouling properties.

Silver nanoparticle (AgNP)-decorated cellulose filter paper (FP), a low-cost point-of-use (POU) water disinfection system, can supply affordable and safe drinking water for people in desperate need, especially in rural areas in developing countries. However, owing to the unstable immobilization of AgNPs, silver can leach into the treated drinking water from the FP and exceed the World Health Organization (WHO) drinking water limit (<100 µg L-1), which is a potential threat to both human health and the environment. In this work, in order to robustly immobilize anionic silver nanoparticles (GA@AgNPs), we facilely prepared lipoic acid-modified cellulose filter paper (LA-FP), in which GA@AgNPs were robustly immobilized onto filter paper (GA@AgNPs-LA-FP) by strong chelation via the disulfide bond of LA with the surface of the silver nanoparticles. GA@AgNPs-LA-FP exhibited both excellent bacterial anti-adhesion activity and strong bactericidal activity, which can synergistically mitigate biofouling by inhibiting biofilm formation on the paper surface. Moreover, employed as a gravity-driven bactericidal filter, the GA@AgNPs-LA-FP membrane treated 100 mL of river water within 10 min, and the resulting water quality met the WHO drinking water standards, indicating this material's practical application for POU water disinfection.

Gallic acid-functionalized graphene hydrogel as adsorbent for removal of chromium (iii) and organic dye pollutants from tannery wastewater.

The pollution caused by tannery wastewater containing high concentrations of trivalent chromium ions [Cr(iii)] and organic dyes has severely restricted the sustainable development of the leather industry. To address this problem, a three-dimensional (3D) porous graphene-based hydrogel with good mechanical strength and large surface area was fabricated by self-assembly of graphene oxide (GO) sheets reduced and modified by gallic acid (GA) through π-π interactions. As an adsorbent, this GA-functionalized graphene hydrogel (GA-GH) can effectively capture Cr(iii) by coordination complexation between Cr(iii) and deprotonated carboxylic groups of GA at pH ∼ 4.0. Moreover, GA-GH could be easily regenerated by desorption of adsorbed Cr(iii) at pH 2.0 and maintained its high adsorption capacity after multiple adsorption-desorption cycles, which was also helpful for reusing desorbed Cr(iii) as tanning agent. In addition, compared with a graphene hydrogel (GH) without modification by GA, adsorption capacity of GA-GH for organic dye was significantly improved due to the enhanced π-π interactions between the GA-GH and aromatic dyes.