Polyvinylidene fluoride (PVDF) hollow fiber membranes (HFM) prepared in thermally induced phase separation (TIPS) enormously suffer from several drawbacks. Severe membrane fouling because of membrane hydrophilicity, pure water permeation (PWP) decrease due to the compaction and dense surface structure that resulted in a sharp decrease in PWP and filtration performance are some of the drawbacks.

Although several approaches were introduced (blending, grafting, bath compositing change, and so on) to overcome these drawbacks, all of them come with some disadvantages. Triple-orifice spinneret technology as the in-situ and one-step method employed to precisely tailor membrane physiochemical structure to control membrane PWP, pore size, surface porosity, hydrophilicity, and anti-compaction properties. As shown in Fig. 1, while the bore fluid and PVDF solution flow in the inner and middle layer of the spinneret, organic solvent or amphiphilic copolymer solution was flown on the outermost channel of the spinneret. Ternary interactions of the PVDF, the diluent used for PVDF dissolution, and the outermost layer solvent play a critical role as the roadmap for choosing the appropriate diluent, and solvent membrane with desired  PWP, pore size and surface porosity with considerable anti-compaction was obtained. Hansen solubility parameter used to quantitatively calculate the ternary interactions and compare them to put in the road map and decide the polymer composition and extruded solvent. While the bulk structure of the membrane is controlled mainly by diluent, extruded solvent changed the membrane surface and sublayer structure in an extensive range of PWP, pore size and porosity without any change in membrane mechanical strength. Formation of the spherulites inside the interconnected structure of the PVDF membrane at the underneath structure was the key point to obtain a membrane with considerable anti-compaction properties that are a big drawback for TIPS membranes that resulted in more than 60% in PWP within one hour.

Extruding the commercial surfactant solution or specially synthesized amphiphilic copolymers were used to optimize further to obtain membrane with considerable anti-fouling properties. While HFM entrapped by extruding specially synthesized amphiphilic copolymers solution at the outermost layer of spinneret (HFM outer surface) showed ultra-stable retention of the copolymer in membrane structure, extruded commercial surfactant was not stable in membrane structure and lost 80% of its initial hydrophilicity after one month. Both hydrophilic and hydrophobic segments structures of the amphiphilic copolymer were optimized to ensure enough anti-fouling properties and long-term stability. As the hydrophobic segment of the amphiphilic copolymer, polystyrene played a critical role in ensuring the stability of the entrapped amphiphilic copolymer. Hydrophilic to hydrophobic segment ratio (HBL number) was an essential parameter to be optimized to obtain membrane with high and ultra-stable anti-fouling properties.

Date:

2021 September 6 (Monday)

Time:

14:00 Iran UTC+ 3:30

Registration Deadline (Extended):

2021 September 4, 20:00 Iran UTC+ 3:30

Eligibility qualification for the participants:

Faculty members, researchers, MSc/PhD students and several people from oil & gas industry

Main presenter:

Dr. Saeid Rajabzadeh

Associate professor and membrane preparation and evaluation group leader in Kobe membrane engineering research center (the first and biggest membrane research center in Japan) at Kobe University (QS world ranking 403, 2019), Japan Postdoctoral fellow, Singapore Membrane Technology Centre (Second rank at global water research institutes) at Nanynag Technological University(QS world ranking 13, 2019); 2010 2012. D from Kobe University, Japan, 2009 15 years experience in preparation, characterization, and application of the polymeric membranes (hollow fiber and flat sheet) for water treatment and gas purification in the small pilot, and industrial scales (continuous twin-screw extruder).