Facile in situ decorating polyacrylonitrile membranes using polyoxometalates for enhanced separation performance

A confined expansion pore-making strategy to transform Zn-MOF to porous carbon nanofiber for water treatment: Insight into formation and degradation mechanism

Electrospinning MOFs nanoparticles derived porous carbon nanofibers with rational structure and design are recently as environmentally friendly and highly efficient catalytic materials for wastewater treatment. However, most of the pore-making strategies are based on precursors structural shrinkage during pyrolysis, which is a challenge to create abundant large pores and open channels. Here, a confined expansion pore-making strategy with active MOF is introduced, where energetic Zn-MOF (Zn2+/triazole) and ZIF-67 (Co2+/dimethylimidazole) are utilized as pore forming additive and precursor of active sites, respectively. The high nitrogen content gives triazole the ability to puff up and realizes N-doped during pyrolysis. Moreover, degradation mechanisms and pathways of pollutants were measured by 3D EEM, LC-MS, quenching experiments, and Fukui function. This pore-making strategy via energetic MOF local contraction and expansion provides a novel method to prepare diversiform function porous carbon materials for environmental remediation.

Preparation and Characterization of Polyethersulfone/Activated Carbon Composite Membranes for Water Filtration

Ultrafiltration membrane technology holds promise for wastewater treatment, but its widespread application is hindered by fouling and flux reduction issues. One effective strategy for enhancing ultrafiltration membranes involves incorporating activated carbon powder. In this study, composite polyethersulfone (PES) ultrafiltration membranes were fabricated to include activated carbon powder concentrations between 0 and 1.5 wt.%, with carbon size fixed at 200 mesh. The ultrafiltration membranes were evaluated in terms of membrane morphology, hydrophilicity, pure water flux, equilibrium water content, porosity, average pore size, protein separation, and E-coli bacteria removal. It was found that the addition of activated carbon to PES membranes resulted in improvements in some key properties. By incorporating activated carbon powder, the hydrophilicity of PES membranes was enhanced, lowering the contact angle from 60° to 47.3° for composite membranes (1.0 wt.% of activated carbon) compared to the pristine PES membrane. Water flux tests showed that the 1.0 wt.% composite membrane yielded the highest flux, with an improvement of nearly double the initial value at 2 bar, without compromising bovine serum albumin rejection or bacterial removal capabilities. This study also found that the inclusion of activated carbon had a minor impact on the membrane's porosity and equilibrium water content. Overall, these insights will be beneficial in determining the optimal concentration of activated carbon powder for PES ultrafiltration membranes.

Purification performance of modified polyacrylonitrile fiber-activated carbon fiber filter for heavy metal ions

A heavy metal ion adsorbent (HFPANF) with high surface area was obtained from polyacrylonitrile fibers with fibrillation and alkali hydrolysis, and an activated carbon fiber filter was prepared by using HFPANF as the binder. The surface area of polyacrylonitrile was 48.64 m²/g due to fibrillation, which also led to the carboxyl content of the HFPANF up to 3.4 mmol/g. Batch adsorption experiments on Cu²⁺ and Pb²⁺ showed that the adsorption capacities of HFPANF for Cu²⁺ and Pb²⁺ were 47.5 mg/g and 54.3 mg/g. The adsorption kinetics showed that the adsorption reached equilibrium at 90 min and that the adsorption followed the pseudo-second order model. It indicates that the adsorption process is chemisorption. HFPANF formed a single tooth chelate with Cu and a double tooth chelate with Pb. HFPANF-ACF filter was prepared by wet molding technique. When the HFPANF content was 30%, the filter reached a compressive strength of 15.37 MPa and its maximum flux was 180 L/h. 2.5 mg/L of Cu and Pb were used for dynamic adsorption experiments and the heavy metal removal rate was still above 95% after filtering 600 L. The pressure drop of HFPANF-ACF filter was much smaller compared with that of GAC filter due to the combined effect of fibrillated nanofibers and ACF, which can improve the filtration efficiency of the filter.

The Design of Ternary Composite Polyurethane Membranes with an Enhanced Photocatalytic Degradation Potential for the Removal of Anionic Dyes

Photocatalysis is an efficient and an eco-friendly way to eliminate organic pollutants from wastewater and filtration media. The major dilemma coupled with conventional membrane technology in wastewater remediation is fouling. In this study, the photocatalytic degradation potential of novel thermoplastic polyurethane (TPU) based NiO on aminated graphene oxide (NH₂-GO) nanocomposite membranes was explored. The fabrication of TPU-NiO/NH₂-GO membranes was achieved by the phase inversion method and analyzed for their performances. The membranes were effectively characterized in terms of surface morphology, functional group, and crystalline phase identification, using scanning electron microscopy, Fourier transformed infrared spectroscopy, and X-ray diffraction analysis, respectively. The prepared materials were investigated in terms of photocatalytic degradation potential against selected pollutants. Approximately 94% dye removal efficiency was observed under optimized conditions (i.e., reaction time = 180 min, pH 3-4, photocatalyst dose = 80 mg/100 mL, and oxidant dose = 10 mM). The optimized membranes possessed effective pure water flux and excellent dye rejection (approximately 94%) under 4 bar pressure. The nickel leaching in the treated wastewater sample was determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). The obtained data was kinetically analyzed using first- and second-order reaction kinetic models. A first-order kinetic study was suited for the present study. Besides, the proposed membranes provided excellent photocatalytic ability up to six reusability cycles. The combination of TPU and NH₂-GO provided effective strength to membranes and the immobilization of NiO nanoparticles improved the photocatalytic behavior.