Selective separation of dye/salt mixture using diatomite-based sandwich-like membrane.

A novel nanofiltration membrane was developed by entrapping a layer of modified diatomaceous earth between two layers of electrospun polysulfone (E-PSf) nanofibers. The diatomaceous earth particles and the fabricated membrane were characterized using FTIR, SEM, EDS, zeta potential, and water contact angle techniques. The static adsorption and dynamic separation of pristine E-PSF and sandwich-like membranes for methylene blue (MB) with/without salt were investigated under different operating conditions. The Langmuir model suited the MB adsorption isotherm data with a linear regression correlation coefficient (R2) >0.9955. As pH increased, both flux and MB rejection of the sandwich-like membrane improved by up to 183.8 LMH and 99.7%, respectively, when operated under gravity. The water flux of the sandwich-like membrane was sharply increased by increasing the pressure up to 19,518.2 LMH at 4.0 bar. However, this came at the expense of MB rejection (10.93%) and reduced its practical impact. At a high salt concentration, the sandwich-like membrane also indicated remarkable dye/salt separation with a higher permeation of salt (<0.2% NaCl rejection) and MB rejection (>99%). The performance of the regenerated diatomaceous material and membrane was maintained during five cycles of operation compared to that of the original ones.

Super Effective Removal of Toxic Metals Water Pollutants Using Multi Functionalized Polyacrylonitrile and Arabic Gum Grafts.

Super adsorbent polymers can be considered to be a very efficient solution for wastewater treatment. In general, their adsorption capacities depend on the type and amount of the functional groups present on the surface of the polymers, while their economic value is affected by their cost. Therefore, this study aims to understand the effect of multi-functionalization of cheap Arabic gum on the adsorption capability toward heavy metals. Graft copolymers of polyacrylonitrile (PAN) onto Arabic gum (AG) were prepared in aqueous solution using (KMnO4/HNO3) as a redox initiator. Chemical modification of the graft copolymer was carried out by reaction with hydrazine hydrochloride followed by hydrolysis in the basic medium. The modified graft product was characterized by various techniques, such as Fourier transform infrared spectroscopy (FTIR), elemental analysis, scanning electron microscope (SEM), and X-ray powder diffraction (XRD). The modified graft copolymer was used to adsorb Pb2+, Cd2+ and Cu2+ from their aqueous solutions using batch extraction. Different parameters influence the uptake behavior, including contact time, pH, and the initial concentration of the metal ions; all of these were investigated. The kinetics were investigated using the pseudo first order and pseudo second order, and the equilibrium data were analyzed using the Langmuir and Freundlich model. The modified graft product showed the superadsorbent capacity to obtain maximum values (Qmax) 1017, 413 and 396 mg/g for Pb2+, Cd2+ and Cu2+, respectively. Acid treatment with 0.2 M HNO3 resulted in 96%, 99% and 99% metal recovery for the Pb2+, Cd2+ and Cu2+, respectively. This indicates the recyclability of product for further usage upon drying between treatments.

Influence of nitrogen/phosphorus-doped carbon dots on polyamide thin film membranes for water vapor/N2 mixture gas separation.

Nanoparticles have been attracting attention because they can significantly improve the performance of membranes when added in small amounts. In this study, the effect of polyamide membranes incorporating hydrophilic nitrogen/phosphorus-doped carbon dots (NP-CDs) to enhance water vapor/N2 separation has been investigated. NP-CD nanoparticles with many hydrophilic functional groups are synthesized from chitosan by a one-pot green method and introduced to the surface of the polysulfone (PSf) substrates by interfacial polymerization reaction. The mean particle diameter of NP-CDs, estimated from transmission electron microscopy images, is 2.6 nm. By adding NP-CDs (0-1.5 wt%) to the polyamide layer, the contact angles of the membranes dramatically decreased from 65° (PSf) to <9° (thin film nanocomposite (TFN)), which means that the TFN membranes become significantly hydrophilic. From the water vapor separation results, the addition of NP-CDs in the polyamide layer improves the water vapor permeance from 1511 (thin film composite (TFC) without nanoparticles) to 2448 GPU (TFN with 1.0 wt% NP-CD loading, CD-TFN(1.0)) and the water vapor/N2 selectivity from 73 (TFC) to 854 (CD-TFN(1.0)). To our knowledge, this is the first study of highly functionalized NP-CD-incorporated polyamide membranes to enhance water vapor separation.