Surface Modification of Polyethersulfone-Based Nanofiltration Membrane Using Carboxylated Graphene Oxide and Polyethyleneimine

Hypothesis: Carbxylated graghene oxide nanosheets were synthesized and the nanosheets were applied to the surface modification of the polyethersulfonebased nanofiltration membranes for water treatment.Methods: Different concentrations of the synthesized carboxylated graphene oxide nanosheets were used as the surface modifiers to prepare the PES/PEI c-GO nanofiltration membranes. The prepared membranes were analyzed by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), 3D surface images (AFM) and X-ray diffraction (EDX) spectroscopy. The permeability and the separation performance of the constructed membranes were evalueted by the water contact angle, water content, the flow of pure water and the rejection of sodium sulfate salt and heavy metals.Findings: the FTIR analysis showed the formation of favorable bonds in the synthesized carboxylated graphene oxide nanosheets and the fabricated membranes. The membrane surface modification by c-GO nanosheets led to a decrease in membrane roughness and the contact angle decreased from 75° for the neat membrane to 36° for M1 at 0.001 g of carboxylated graphene oxide nanosheets. Moreover, the water content increased and M2 showed the highest water content. The highest pure water flux was obtained at 13.065 L/m2.h for the constructed M2 membrane containing 0.01 g of carboxylated graphene oxide nanosheets. In addition, the highest rejection of sodium sulfate salt (Na2SO4) was observed 67.5 % for the M3 membrane containing 0.1 g of c-GO nanosheets and the highest rejection of copper nitrate (Cu(NO3)2) was obtained 87.21% for the M1 membrane containing 0.001 g of c-GO nanosheets. Furthermore the obtained results indicated the improvement of the anti-fouling properties of the modified membranes containing carboxylated graphene oxide nanosheets compared to the base membrane

Current State of Indoor Air Phytoremediation Using Potted Plants and Green Walls

Urban civilization has a high impact on the environment and human health. The pollution level of indoor air can be 2–5 times higher than the outdoor air pollution, and sometimes it reaches up to 100 times or more in natural/mechanical ventilated buildings. Even though people spend about 90% of their time indoors, the importance of indoor air quality is less noticed. Indoor air pollution can be treated with techniques such as chemical purification, ventilation, isolation, and removing pollutions by plants (phytoremediation). Among these techniques, phytoremediation is not given proper attention and, therefore, is the focus of our review paper. Phytoremediation is an affordable and more environmentally friendly means to purify polluted indoor air. Furthermore, studies show that indoor plants can be used to regulate building temperature, decrease noise levels, and alleviate social stress. Sources of indoor air pollutants and their impact on human health are briefly discussed in this paper. The available literature on phytoremediation, including experimental works for removing volatile organic compound (VOC) and particulate matter from the indoor air and associated challenges and opportunities, are reviewed. Phytoremediation of indoor air depends on the physical properties of plants such as interfacial areas, the moisture content, and the type (hydrophobicity) as well as pollutant characteristics such as the size of particulate matter (PM). A comprehensive summary of plant species that can remove pollutants such as VOCs and PM is provided. Sources of indoor air pollutants, as well as their impact on human health, are described. Phytoremediation and its mechanism of cleaning indoor air are discussed. The potential role of green walls and potted-plants for improving indoor air quality is examined. A list of plant species suitable for indoor air phytoremediation is proposed. This review will help in making informed decisions about integrating plants into the interior building design

Polyimides in membrane gas separation: Monomer's molecular design and structural engineering

© 2019 Elsevier B.V. Polyimides (PIs) are an important, well-established, and commercialized class of polymers due to their extraordinary physical and chemical properties. They have been extensively applied as membrane fabrication materials for gas separation, especially in natural gas upgrading and acidic CO 2 gas removal from industrial off-gases. However, two major unsolved challenges still remain for PI-based membranes: overcoming the trade-off relationship between the gas permeability and selectivity, and maintaining the long-term operational performance through controlling thermal and pressure conditioning, physical and chemical ageing, plasticization, swelling, permeation hysteresis, and resistance against impurities or presence of trace contaminants. This review aims to explore practical procedures to give the best insights into synthesis of efficient PI-based gas separation membranes as well as introducing advanced modification methods that have been applied for available PIs in view of obtaining a superior performance. A comprehensive “structure-to-property” relationship is elaborated by molecular design and engineering of PI monomers, i.e., the assembly of sub-objects: diamine and dianhydride monomers. This approach covers all issues from atom, functional group, segment (micro-structure or molecular design) to branch, chain and network assembly of the PIs. Detailed discussions include substitution positions, halogenated groups, bridging functional groups, bulky groups (linear and branched and subdivided into silyl and germyl, fluorine, methyl, iptycene and Tröger's Base groups). Moreover, criteria for designing high quality hyperbranched polyimides (HB-PI), co-polyimides (co-PIs) including polyamide-imides, polyether-imide, triptycene based co-PIs, multi-block co-PIs, and hyper-branched co-PIs are presented. Cross-linked PIs are also discussed by classifying them according to the methods of reaction: thermal, UV, and chemical cross-linking (abbreviated by TCL, UVCL, and CCL, respectively). An additional issue in this regard, i.e., the hyper cross-linked polyimides, HCLPs, is discussed as well.status: publishe