Photoelectrocatalytic modification of nanofiltration membranes with SrF2/Ti3C2Tx to simultaneously enhance heavy metal ions rejection and permeability

Sodium alginate-based nanocomposite hydrogel membrane for removal of heavy metal ions and dyes in water

Membrane filtration technology plays a crucial role in the field of water treatment because of its efficient separation and purification capability. However, it remains a major challenge to develop reusable membranes with high retention, stable filtration to remove heavy metal ions and dyes from water in the field. In this study, sodium alginate (SA), cellulose nanofibers (CNF) and metal-organic frame UiO-66 were innovatively used as raw materials to prepare SA/CNF/UiO-66 dual-network composite hydrogel membrane by unique cooking method. UiO-66 was homogeneously distributed within the SA matrix with the help of CNF, thereby achieving a synergistic interaction among the three components. As a result, the SA/CNF/UiO-66 composite hydrogel filter membrane not only showed excellent water flux and excellent mechanical properties, but also possessed excellent performance in improving the filtration efficiency and long-term filtration stability of heavy metal ions and dyes. The optimal removal rates of 200 mg/L Pb2+, Cu2+ and Cd2+ by SA/CNF/UiO-66 composite hydrogel membranes were as high as 99.9 %, 98.5 % and 96.5 %, respectively. At the same time, the filter membrane could maintain a flux of up to 71 Lm-2 h-1 and a permeability of 17.8 Lm-2h-1bar-1 at a working pressure of 0.4 MPa. The best removal rate for high concentration Congo red dyes could also reach >99.8 %. This study not only provides a new idea for the development of high-performance water treatment membranes, but also provides a practical and effective technical scheme for solving the problem of water resources pollution.

Multi-ligand strategy for enhanced removal of heavy metal ions by thiol-functionalized defective Zr-MOFs

Given the significant global concern about heavy metal pollution, the development of effective adsorbents to capture pollutants has become an urgent issue. In this work, thiol-functionalized defective Zr-MSA-DMSA was designed by mixing 2,3-dimercaptosuccinic acid and mercaptosuccinic acid, which was applied for the rapid and efficient removal of M(II) (i.e., Pb(II), Hg(II), Cd(II)) from wastewater. Zr-MSA-DMSA exhibited excellent adsorption performance, and the maximum adsorption capacities for Pb(II), Hg(II), and Cd(II) were 715.2 mg g-1, 862.7 mg g-1, and 450.5 mg g-1. In actual wastewater, Zr-DMSA-MSA exhibited up to 97 % M(II) removal efficiency and excellent anti-interference ability. It also maintained good structural stability after five adsorption/regeneration cycles. Thus, the abundant oxygen vacancies and unsaturated adsorption sites on Zr-MSA-DMSA significantly improved the adsorption performance of M(II). Spectral analysis and DFT calculations confirmed that Zr-MSA-DMSA mainly relied on the coordination of sulfur and oxygen atoms, electrostatic attraction and a large number of defective sites to achieve the adsorption of M(II). Fixed bed experiments showed that Zr-MSA-DMSA exhibited a depletion time of 10500 min and a volume of 7.0 L. In summary, Zr-MSA-DMSA holds significant potential for treating heavy metal wastewater and provides potential applications for defect engineering.

Characteristics and Influence Factors of Pb(II) Adsorption by Graphene Oxide-Montmorillonite Composite

This study presents the fabrication of a novel porous composite of graphene oxide-montmorillonite (GO-MMT) through the modification of montmorillonite using the freeze-drying method for the purpose of Pb removal. The characterization of the GO-MMT composite was conducted using scanning electron microscopy, Fourier transform infrared spectrometry, and X-ray diffraction. The results from batch adsorption experiments revealed that the GO-MMT composite exhibited a superior capacity for Pb removal compared to MMT. Furthermore, a single factor experiment confirmed that the dosage of the GO-MMT composite or GO, pH, temperature, and reaction time all significantly influenced the adsorption of Pb by the GO-MMT composite, MMT, or GO. This superiority can be attributed to the presence of oxygen-containing functional groups, the site-blocking effect, and the ion exchange mechanism exhibited by the GO-MMT composite.