Biomimetic Silicification on Membrane Surface for Highly Efficient Treatments of Both Oil-in-Water Emulsion and Protein Wastewater

Enzymatic Cascade Catalysis in a Nanofiltration Membrane: Engineering the Microenvironment by Synergism of Separation and Reaction

Microenvironment plays a significant role in enzymatic catalysis, which directly influences enzyme activity and stability. It is important to regulate the enzyme microenvironment, especially for the liquid with unfavored properties (e.g., pH and dissolved oxygen). In this work, we propose a methodology that can regulate pH and substrate concentration for enzymatic catalysis by a biocatalytic membrane, which is composed of glucose oxidase (GOx) and horseradish peroxidase (HRP) co-immobilized in a polyamide nanofiltration (NF) membrane (i.e., beneath the separation layer). By virtue of the selective separation function of NF membrane and in situ production of organic acid/electron donor with GOx, a synergism effect of separation and reaction in the liquid/solid interface was manipulated for engineering the microenvironment of HRP to enhance its activity and stability for micropollutant removal in water. The outcome of this work not only provides a new methodology to precisely control enzymatic reaction but also offers a smart membrane system to efficiently and steadily remove the micropollutants in portable water.

A Simple Low-Cost Method to Prepare Lignocellulose-Based Composites for Efficient Removal of Cd(II) from Wastewater

The fabrication of functional lignocellulose-based materials has drawn considerable attention because it acts as a green separation/absorption material owing to its multi-porous mesostructure. In this study, a surface functionalized lignocellulose-based adsorbent for the highly efficient capture of Cd(II) ions was prepared through facile in situ co-deposition of wood waste-derived saw powder (SP) in the presence of tannic acid (TA) and aminopropyltriethoxysilane (APTES) mixed aqueous solution. The SP was first modified using TA-APTES coating to synthesize the functional SP substrate (SP-(TA-APTES)). The SP-(TA-APTES) hybrids served as reactive platforms, which enabled further decoration with amino-rich polyethylenimine (PEI) due to the outstanding secondary reactions of the TA-APTES layer. The surface morphology of the resulting SP-(TA-APTES)-PEI (SP-TAPI) composites were investigated using Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Significantly, the combined advantages of the lignocellulosic skeleton, the layer-particle structure, and the hybrid coating contributed to the enhanced adsorption capacity of Cd(II) (up to 22.66 mg/g at pH = 5.0). This removal capacity was higher than that of most reported agricultural waste-based or lignocellulose-based materials. The Cd(II) adsorption mechanism of the surface-modified SP-TAPI composites was studied in detail. These results provide new insights into the high value-added utilization of agricultural waste for water purification applications.

Enhanced Adhesion of Carbon Nanotubes by Dopamine Modification

According to the fact that gecko-inspired vertically aligned carbon nanotubes (VA-CNTs) exhibit ultrastrong adhesion, dopamine is utilized to make a modification to this traditional biomimetic material. The composite material is tested for adhesion performance under different environmental conditions by an atomic force microscope. The adhesion force of the modified VA-CNTs does not show obvious fluctuation during the gradual heating process; however, the material gains improved adhesion when increasing the ambient humidity. In addition, the modified CNTs show a stronger adhesion force than the original CNTs in their performance tests. The dopamine polymer has a good combination with CNTs, which is responsible for the aforementioned excellent performance. Overall, this modification method is simple, convenient, efficient, and environmentally friendly, which all indicates a promising future in its application. The modified CNTs are expected to be used for super-adhesion in harsh environments, as well as in the field of microelectronics.

Fabrication of durable self-repairing superhydrophobic fabrics via a fluorinate-free waterborne biomimetic silicification strategy

A water-based methodology integrating an in situ biomimetic silicification and fluorinate-free modification strategy for preparing self-repairing superhydrophobic fabrics is presented.

An acid-stable positively charged polysulfonamide nanofiltration membrane prepared by interfacial polymerization of polyallylamine and 1,3-benzenedisulfonyl chloride for water treatment

Here, we selected macromolecular polyallylamine (PAH) as the monomer in an aqueous-phase reaction for the first time, which underwent interfacial polymerization with 1,3-benzenedisulfonyl chloride (BDSC) on the surface of a polyethersulfone (PES) ultrafiltration membrane to prepare a new PSA composite membrane with positive charge, acid stability and high separation performance. By tailoring the polymerization conditions, the desired PSA composite membrane exhibited excellent rejection of different salts [MgCl₂ (92.44%) > MgSO₄ (89.2%) > NaCl (56.8%) > Na₂SO₄ (55.2%)] and a high permeation flux of up to 34.10 L m⁻² h⁻¹ at 0.5 MPa. The properties of the membrane were evaluated using various characterization techniques. The results indicated that the new PSA membrane is more positively charged and more compact than reported PSA composite membranes. In addition, it exhibited high acid stability. After exposure to a 20% (w/v) H₂SO₄ solution for 30 days, the MgCl₂ rejection level reached 88.3%. Finally, we used the new PSA composite membrane to test some heavy metal ions and found that the rejection level was always greater than 90%. Therefore, the new PSA composite membrane exhibited potential for water desalination and the removal of heavy metal ions from an acidic environment.

Here, an acid stable PSA membrane with positively charge was prepared through the IP between macromolecular PAH and BDSC on PES substrate. In addition, the PSA membrane exhibited excellent separation performance to divalent metal ions.

Polymer-Decorated Filter Material for Wastewater Treatment: In Situ Ultrafast Oil/Water Emulsion Separation and Azo Dye Adsorption

Aiming to realize the wastewater treatment of various pollutants simultaneously, a dual-functional poly(ether amine)-polydopamine (PEA-PDA)-modified filter material was fabricated in this work for in situ separation of stable oil-in-water emulsion and adsorption of anionic azo dyes. PEA and PDA could be copolymerized via the Michael addition reaction on a polyurethane sponge substrate firmly. The as-prepared filter shows superhydrophilic and underwater superoleophobic wettability. After being squeezed in a glass tube, the material could separate different kinds of stabilized oil-in-water emulsions with high flux and efficiency. Besides, the PEA-PDA copolymer endows the material with the ability to adsorb large amounts of anionic azo dyes during the separation of emulsions with good adsorption capacity. Moreover, adsorbed dyes in the filter material could be easily desorbed in base aqueous solution and the whole process is conducted under gravity without external aid. This dual-functional material shows great potential for the application in industrial field because of its ability for the complex wastewater treatment.