In the present study, response surface methodology (RSM) is employed according to central composite design (CCD) for modeling and optimization NF membranes fabricated and tuned for effective removal of Ni and Cr from electroplating wastewater streams. The effect of concentration of poly(acrylonitrile) (PAN: 21-25 wt. %) as the main membrane material as well as poly(ethylene glycol) (PEG: 0-1.5 wt. %) and titanium dioxide nanoparticles (TiO 2 : 0-1 wt. %) as the additives and their mutual interaction on membrane performance and morphology were investigated. According to the quadratic polynomial model, independent factors were statistically significant and the obtained models were accurate. The optimized responses for Ni and Cr rejection and pure water flux were 87.093 (%), 83.271 (%) and 71.801 (Lit.m-2 .h-1) respectively at optimum membrane formulations of PAN: 23.93%, PEG: 0.41% and TiO 2 : 0.82%. The results of validation experiment confirm the data for predicted model at optimum point (Ni rejection: 88.093 %, Cr rejection: 80.271 % and pure water flux: 76.801 Lit.m-2 .h-1). Both Ni and Cr rejections increased from 60.87% to 80.36% and from 56.35% to 78.64 %, respectively upon increasing PAN concentration in the dope from 21 wt.% to 25 wt.%. It was also found that decreasing PEG concentration led to increase in Ni and Cr rejections and decrease in pure water flux. Using of TiO 2 nanoparticles led to increase of Ni and Cr rejections and pure water flux at different PAN concentrations. From the morphological perspective, increase in polymer concentration led to change of porous to spongy like structure while increasing PEG concentration led to increase in macrovoids area. Both porosity and mean pore size reduced by increase of PAN concentration and decrease of PEG concentration.

Hollow fiber membranes (HFMs) possess desired properties such as high surface area, desirable filtration efficiency, high packing density relative to other configurations. Nevertheless, they are often possible to break or damage during the high-pressure cleaning and aeration process. Recently, using the braid reinforcing as support is recommended to improve the mechanical strength of HFMs. The braid hollow fiber membrane (BHFM) is capable apply under higher pressure conditions. This review investigates the fabrication parameters and the methods for the improvement of BHFM performance.

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