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In this study, nanocomposite membranes based on cellulose acetate (CA) and nanodiamond (ND) were prepared by applying phase inversion methods. In order to achieve efficient dispersion and more hydrophilic NDs, they were functionalized via heat treatment (ND-COOH). The prepared nanocomposite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), contact angle, porosity measurement, tensile strength, and abrasion resistance techniques. Furthermore, the governing fouling mechanisms were determined by using classic models as well as combined fouling models. Moreover, the effect of precoagulation with polyaluminum chloride (PAC) on the humic acid (HA) filtration was investigated. The obtained results showed that in the presence of ND-COOH, the abrasion resistance of nanocomposite CA membrane was three times higher than that of pristine CA membrane. Besides, the nanocomposite membranes with 0.5 wt % of raw and functionalized ND exhibited excellent hydrophilicity and PWF. The analysis of fouling mechanism based on Hermia's model revealed that the cake formation is prevailing mechanism for CA and CA/ND (0.5 wt %) membranes while for CA/ND-COOH (0.5 wt %) membrane, experimental results are fitted by combined cake filtration-complete blocking (CFCB) model. It confirms that pretreatment with PAC can significantly mitigate fouling and improve HA removal.

In this work, the flexibility of polycarbonate (PC) membrane was improved by using polyurethane (PU) additive. However, due to the hydrophobic nature of the PU polymer, alumina (Al2O3) nanoparticles were incorporated to PC‐PU blend membrane. The prepared membranes have been used in a submerged membrane system to eliminate humic acid molecules from polluted water in both the presence and absence of coagulant (polyaluminum chloride). The obtained results showed that introduction of PU into PC membrane diminished hydrophilicity and enhanced porosity. Moreover, the flexibility of the PC membrane remarkably improved. Introduction of 1.5 wt% Al2O3 to the PC‐PU blend membrane led to enhancement in both porosity and hydrophilicity. Results of morphological studies showed that in the presence of Al2O3 nanostructures, finger‐shaped voids seemed to elongate across the entire thickness of the prepared membrane. Atomic force microscopy images showed that incorporation of PU and Al2O3 to the PC membrane resulted in a smoother surface. The antifouling performance of membranes revealed that the PC‐PU/Al2O3 nanocomposite membrane possessed the most favorable antifouling features owing to its lowest surface roughness as well as highest hydrophilicity. For all membranes utilizing coagulant (PAC), the irreversible fouling ratio and the flux recovery ratio significantly diminished and increased, respectively.

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BACKGROUND Membrane bioreactor (MBR) is commonly considered a promising technology for wastewater treatment due to its outstanding effluent quality, low sludge production, and smaller environmental footprint. However, membrane biofouling is regarded as the bottleneck of MBR processes preventing their universal application. Optimizing operating conditions and improving the antifouling properties of membranes have a substantial impact on the rate and characteristics of membrane fouling in MBR systems. RESULTS In this study, a two‐step process was performed to mitigate membrane fouling by optimizing sludge retention time (SRT) and organic loading rate (OLR) and improving membrane characteristics in an MBR system developed for the treatment of pharmaceutical wastewater. At first, pure membrane fouling and sludge characteristics were examined in three identical MBRs at different OLRs (40, 100, and 160 mg chemical oxygen demand(COD)/L.d) under various SRTs (7.5, 22.5, and 37.5 days). The investigation indicated that high protein concentration in loosely bound extracellular polymeric substances (LB‐EPS) caused more irreversible fouling at the OLR and SRT of 40 mgCOD/L.d and 7.5 days, respectively. In the second stage, a modified anti‐biofouling membrane was installed into the optimized submerged MBR at OLR = 100 mgCOD/L.d and SRT of 22.5 days for further mitigation of membrane fouling. Membrane fouling significantly reduced as the protein and gram negative bacteria on the surface of the modified membrane decreased. CONCLUSION The results showed that the reversible and irreversible membrane fouling were controlled successfully through the proposed optimization of operational conditions and by improving the membrane characteristics in MBR. Finally, the protein of LB‐EPS is a vitally important factor affecting the irreversible membrane fouling. © 2020 Society of Chemical Industry (SCI)

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Very fine alumina nanoparticles were loaded in novolac type phenol-formaldehyde (PF) resin using solution mixing method. The concentration of nanoalumina in PF was varied between 2.5 to 20 wt%. All the compounds were compression molded and then subjected to scanning electron microscopy (SEM), tensile, flexural, and dynamic mechanical analysis (DMA) tests. SEM analysis showed that the nanoalumina particles were dispersed uniformly at low concentrations, however, at high concentrations, dispersion was suppressed leading to agglomerates in the composites. Mechanical testing revealed that the nanoalumina particles had a great influence on the strength and stiffness of PF resin particularly at concentrations below 5 wt%. However, at concentration above 5 wt%, the stress concentrations were developed because of the formation of big aggregates that results in strength reduction. Theoretical analyses based on Pukanszky's model for tensile strength and micromechanical models for tensile modulus revealed that strong interfacial interaction and thick interphase region around the alumina nanoparticles was formed. DMA results suggested that the nanoalumina increased the crosslinking density of the PF resin, possibly around the interface region. It was also postulated that an apparent percolation state was established above 5 wt% loading of nanoalumina in which interphase region came to contact before direct contact of particle leading to continuous interphase region. POLYM. COMPOS., 35:1285-1293

Polyethylene glycol-grafted nanodiamond (ND-PEG) was synthesized from pristine detonation NDs and utilized to prepare novel cellulose acetate/polyethylene glycol-grafted nanodiamond(CA/ND-PEG)nanocomposite membranes. Due to unique thermal, mechanical, and antibacterial properties and very easy cleaning of fouled ND-embedded CA nanocomposite membranes, we tried to investigate the performance of CA/ND-PEG membrane for humic acid (HA) removal from contaminated water. Surface functionalization was confirmed by Fourier transform infrared spectroscopy and thermogravimetry analysis. Pristine and functionalized ND with different concentration was added in the casting solution containing CA. The prepared membranes were characterized using contact angle, mechanical strength, scanning electron microscopy (SEM), transmission electron microscopy, and permeation tests. SEM micrographs of the surface of the membranes depicted the increase in the number of pores by the addition of ND and especially ND-PEG into polymer matrix. The results indicated that the nanocomposite membrane with 0.5 wt% ND-PEG exhibited excellent hydrophilicity, mechanical properties, permeability, high rejection, high abrasion resistance, and good anti-fouling performance. The HA adsorption on the membrane surface decreased from 2.85 to 2.15 mg cm −2 when the ND-PEG content increased from 0 to 0.5 wt%. Most importantly, the HA filtration experiments revealed that the incorporation of ND and especially ND-PEG particles reduced membrane irreversible fouling, dramatically. Meanwhile, the analysis of the fouling mechanism based on Hermia's model revealed that cake formation is a prevailing mechanism for all membranes.