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.
a b s t r a c tFabrication of less-fouling and high performance membrane is essential to offer significant cost reductions in membrane bioreactor (MBR) processes. In this regard, nanodiamond (ND) embedded cellulose acetate (CA) nanocomposite membrane was prepared and characterized in a lab-scale submerged MBR system for treating of pharmaceutical wastewater. In order to achieve efficient dispersion and providing more hydrophilic property, NDs were functionalized via heat treatment method. Scanning electron microscopy (SEM), and contact angle measurements were used to determine the surface properties of membranes. To compare the nanocomposite membranes with a pure CA membrane, critical flux, fouling behavior, and anti-fouling properties against extracellular polymeric substances (EPS) were investigated. SEM images showed that in the presence of 0.5 wt% of functionalized ND nanoparticles, porous structure appears on the membrane surfaces. The obtained results showed that in presence of functionalized NDs; ND-COOH, surface hydrophilicity of nanocomposite membrane was much higher than that of pristine CA membrane. Higher critical flux was obtained by CA/ND-COOH (0.5 wt.% of NDs) nanocomposite membrane due to the change of surface characteristics. The filamentous bacteria in the MBR resulted in more foulants on the CA membrane surface, while less filamentous bacteria were attached on the CA/ND-COOH nanocomposite membrane. Analysis of extractable EPS showed that the concentrations of proteins and carbohydrates in the EPS and soluble microbial products (SMP) for CA/ND-COOH (0.5 wt.%) membrane are less than other membranes. Also, COD removal for all of the membranes was higher than 90%, whereas only 83.4% removal efficiency was reached in the activated sludge.
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