Quantum Sized Zinc Oxide Immobilized on Bentonite Clay and Degradation of C.I. Acid Red 35 in Aqueous under Ultraviolet Light

Nano-ZnO supported on bentonite was prepared to form composite photocatalyst by sol-gel method. The photocatalyst was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). C.I. Acid Red 35 was used as simulating contaminant to be treated by ultraviolet light synergistic with nano-ZnO/bentonite. The results show that 5.7 nm ZnO particle was acquired and uniformly dispersed on the surface of the bentonite at calcination temperature of 200°C. The removal of C.I. Acid Red 35 could reach 84.9% after 200 min under optimum ZnO/bentonite dosage of 0.6 g L−1. The 60% ZnO content in ZnO/bentonite composite exhibited a great photocatalytic activity to treat C.I. Acid Red 35. The photocatalytic process followed pseudo-first-order kinetics and the best apparent rate constant was 0.00927 min−1 with correlation coefficient (R2) of above 0.98

Robust antifouling anion exchange membranes modified by graphene oxide (GO)-enhanced Co-deposition of tannic acid and polyethyleneimine

Three polyphenol-polyamine co-deposition systems containing different polyphenols (catechol (CA), gallic acid (GA) and tannic acid (TA)) and Polyethyleneimine (PEI) were established and used to construct adhesive layer on the surface of anion exchange membranes (AEMs). And graphene oxide (GO) was introduced into co-depositions to construct an antifouling modifying layer. The modified AEMs were characterized and applied in electrodialysis for antifouling experiments. The results showed that the TA-PEI-M with a large depositing amount exhibited more hydrophilic surface than those of CA-PEI-M and GA-PEI-M, but still low value in the negative charge density. The introduction of GO increased the negative charge density of membrane surface and endowed AEMs with enhanced antifouling ability significantly. Furthermore, GO-TA-PEI-M could maintain surface properties and antifouling performance after immersing in NaOH solutions, indicating good alkaline-stability. It was attributed to that the abundant phenolic groups in TA played a vital role in the formation of co-deposition layer. The abundant phenolic groups in TA could provide stronger adhesion and multiple reactive sites to generate more stable covalent structures with PEI. In addition, the hydrogel products produced by the electrostatic interaction of TA and PEI helped increase the depositing amount. This work proposed a novel approach to fabricate surface-modified antifouling AEMs with alkaline stability by polyphenol-polyamine co-deposition

Surface composite modification of anion exchange membrane by electrodeposition and self-polymerization for improved antifouling performance

A novel composite modified membrane (PSS&PDA-M) was prepared by constructing polydopamine (PDA) selfpolymerization modified layer covering electrodeposited poly (sodium 4-styrene sulfonate) (PSS) modified layer. The improvement on surface hydrophilicity and negative charge density of PSS&PDA-M mainly benefited from electrodeposited PSS modified layer. PDA self-polymerization modification layer not only improved the stability of the composite modified layer but also reduced the surface roughness of modified membrane. The results of desalination and antifouling experiments indicated that PSS&PDA-M had the best ability to inhibit fouling by sodium dodecyl sulfonate without affecting desalination performance. And it still had excellent antifouling performance after 120 h rinsing test. Moreover, the surface hydrophilicity and negative charge density of PSS&PDA-M with the best antifouling properties were slightly inferior to electrodeposited P55 modified AEM (ePSS-M). Therefore, enhancing the stability of modified layer was also crucial to improving the antifouling performance of AEM

Surface composite modification of anion exchange membrane by electrodeposition and self-polymerization for improved antifouling performance

A novel composite modified membrane (PSS&PDA-M) was prepared by constructing polydopamine (PDA) selfpolymerization modified layer covering electrodeposited poly (sodium 4-styrene sulfonate) (PSS) modified layer. The improvement on surface hydrophilicity and negative charge density of PSS&PDA-M mainly benefited from electrodeposited PSS modified layer. PDA self-polymerization modification layer not only improved the stability of the composite modified layer but also reduced the surface roughness of modified membrane. The results of desalination and antifouling experiments indicated that PSS&PDA-M had the best ability to inhibit fouling by sodium dodecyl sulfonate without affecting desalination performance. And it still had excellent antifouling performance after 120 h rinsing test. Moreover, the surface hydrophilicity and negative charge density of PSS&PDA-M with the best antifouling properties were slightly inferior to electrodeposited P55 modified AEM (ePSS-M). Therefore, enhancing the stability of modified layer was also crucial to improving the antifouling performance of AEM

GO–Polymer Modified Anion Exchange Membranes for Antifouling

Organic fouling was one of key issues limiting the application of electrodialysis in the treatment of industrial wastewater, which results in degradation of membranes and high energy consumption. In this study, a novel graphene oxide (GO)–polymer modified anion exchange membrane (AEM) for antiorganic fouling was first developed by layer-by-layer interfacial polymerization (IP). The surface of AEM was alternately contacted with GO and tannic acid (TA) aqueous as the water phase and an n-hexane solution of trimesoyl chloride (TMC) as the organic phase; thus, a multilayer GO–polymer structure was fabricated on the surface of AEM. Results showed that the aqueous phase was preferred to be the final treatment of layer-by-layer interfacial polymerization, which was more conducive to enhancing hydrophilicity and negative charge density of the membrane surface. Compared with TA-TMC modified AEM, the introduction of GO nanosheets with carboxyl groups into aqueous solution significantly increased the negative charge density of the membrane surface and reduced membrane resistance. The desalination rate of (GOTA-TMC)1.5 was mostly close to that of pristine AEM without fouling, exhibiting significant antifouling performance and good stability. The study provides promising insights into the modification of ion exchange membranes with functional materials and a polymer composite layer

The properties and antifouling performance of anion exchange membranes modified by polydopamine and poly (sodium 4-styrenesulfonate)

Fouling of anion exchange membranes (AEMs) is the bottleneck restricting electrodialysis technology, and surface modification is an effective way to solve this problem. This paper investigated the effects of different components such as single poly (sodium 4-styrene sulfonate) (PSS), single polydopamine (PDA) and mixed polydopamine and poly (sodium 4-styrene sulfonate) (PDA@PSS) used as the modifier, respectively, on the surface properties and antifouling performance of AEMs. Comparing the surface properties of different modified AEMs, it was found that the surface hydrophilicity and negative charge density of PDA@PSS modified AEM (PDA@PSS-M) were obviously improved due to the combined action of PDA and PSS. The desalination rate, surface morphology and relative content of surface S element of different AEMs after the fouling experiments were also analyzed. The results indicated that PDA@PSS-M presented the greatest antifouling performance among three modified AEMs. The effect of PDA@PSS co-deposited layer on its desalination performance was negligible and the modification layer had relatively good stability

Anion Exchange Nanocomposite Membranes Modified with Graphene Oxide and Polydopamine: Interfacial Structure and Antifouling Applications

In this work, electrochemical impedance spectroscopy (EIS) was utilized to probe interfacial structures of antifouling anion exchange membranes (AEMs) with different modifying architectures fabricated by graphene oxide (GO) and polydopamine (PDA). Results showed that the GO@PDA modified AEMs with a compact GO@PDA layer exhibited a new interface between the modifying layer and membrane matrix, different from the loose GO-modified AEMs. After fouling experiments, from quantifying electrical equivalent circuits fitted to EIS results, it could be found that GO-modified AEMs and PDA-modified AEMs exhibited a significant foulants layer, although the modifying layer reduced the amount of foulants absorbed in the membrane matrix. For GO@PDA-modified AEMs, the increase in ohmic resistance and the foulants layer was almost negligible. Only a small amount of foulants accumulating on the GO@PDA layer affected the capacitive resistance of the interfacial layer obviously. It was concluded that the electrochemical properties and interface of modified AEMs was influenced by the structure of modifying layer, and a dense and compact modifying layer could be more effective to block the foulants from depositing on the surface of AEMs and entering the membrane matrix. The electrochemical characterizations helped to elucidate the antifouling mechanism of modified AEMs with different structures and get a good understanding of the correlation among the properties, structures, and antifouling performance of the modifying layer.</p