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CONTENTS
Volume 13, Number 4, July 2022
 


Abstract
The analytical results are presented for the mass transfer in a cylindrical pore covering from the macroscale, multiscale to nanoscale owing to the variation of the inner diameter of the pore. When the thickness hbf of the physically adsorbed layer potentially fully formed on the pore wall is comparable to but less than the inner radius R0. of the pore, the multiscale flow occurs consisting of both the nanoscale non-continuum adsorbed layer flow and the macroscopic continuum liquid flow; When R0hbf, the flow in the whole pore is essentially non-continuum; When R0 is far greater than hbf, the flow in the whole pore can be considered as macroscopic and continuum and the adsorbed layer effect is negligible.

Key Words
cylindrical pore; mass transfer; multiscale; non-continuum

Address
Wei Lin: School of Mechanics Technology, Wuxi Institute of Technology, Wuxi, Jiangsu Province, China/ College of Mechanical Engineering, Changzhou University, Changzhou, Jiangsu Province, China

Jian Li and Yongbin Zhang: College of Mechanical Engineering, Changzhou University, Changzhou, Jiangsu Province, China

Abstract
Polyvinylidene fluoride (PVDF) flat sheet hydrophobic membranes were prepared using 16 wt% PVDF in Dimethyl acetamide (DMAc) by phase inversion technique for desalination application using Membrane Distillation (MD). In this work, the effect of coagulation mediums such as ethanol and water as well their synergistic behavior on the fabricated PVDF membrane morphology was studied using SEM. Moreover, other characteristics required for the membrane distillation applications namely porosity, hydrophobicity and tensile strength were measured using the gravimetric method, sessile drop method and universal testing machine respectively. It was observed that the membrane morphology paradigm shifted from the finger-like structure to the sponge-like structure on increasing the ethanol concentration in coagulant. The porosity of the fabricated membrane was under the required MD range and found to be 57.3% at 16 weight % of PVDF in DMAc solvent under a pure ethanol coagulant bath. Moreover, the top surface contact angle ranges from 85° to 115° on increasing the bath concentration from CBC 0 to CBC 100 at 16 weight % of PVDF in DMAc solvent.

Key Words
polymers; membrane distillation; membrane property; membrane fabrication

Address
Meenakshi Yadav, Sushant Upadhyay, Kailash Singh, Tarun Kumar Chaturvedi and Manish Vashishtha: Department of Chemical Engineering, Malaviya National Institute of Technology Jaipur-302017, India

Abstract
This study seeks towards an optimal way to control sulfate ions in semiconductor wastewater effluent with potential eco-toxicity. We developed a system based on ettringite (Ca6Al2(SO4)3(OH)12∙26H2O). The basic idea is that the pH of the water is raised to approximately 12 with Ca(OH)2. After, aluminium salt is added, leading to the precipitation of ettringite. Lab-scale batch and continuous experiment results with real semiconductor wastewater demonstrated that 1.5 and 1 of stoichiometric quantities for Ca2+ and Al3+ with pH above 12.7 could be considered as the optimal operation condition with 15% of sludge recycle to the influent. A mixed AlCl3 + Fe reagent was selected as the beneficial Al3+ source in ettringite process, which resulted in 80% of sludge volume reduction and improved sludge dewaterability. The results of continuous experiment showed that with precipitation as ettringite, sulfate concentration can be stably reduced to less than 50 mg/L in effluent from the influent 2,050 ± 175 mg/L on average (1,705 ~ 2,633 mg/L).

Key Words
eco-toxicity; ettringite; semiconductor wastewater; sludge volume reduction; sulfate ion;

Address
Chong-Min Chung: Department of Environment Science & Biotechnology, Jeonju University, Jeonju 55069, Republic of Korea

Abstract
In industrial production, the development of traditional polyamide nanofiltration (NF) membrane was limited due to its poor oxidation resistance, complex preparation process and high cost. In this study, a composite NF membrane with high flux, high separation performance, high oxidation resistance and simple process preparation was prepared by the method of dilute solution dip coating. And the sulfonated polysulfone was used for dip coating. The results indicated that the concentration of glycerin, the pore size of the based membrane, the composition of the coating solution, and the post-treatment process had important effects on the structure and performance of the composite NF membrane. The composite NF membrane prepared without glycerol protecting based membrane had a low flux, when the concentration of glycerin increased from 5% to 15%, the pure water flux of the composite NF membrane increased from 46.4 LMH to 108.2 LMH, and the salt rejection rate did not change much. By optimizing the coating system, the rejection rate of Na2SO4 and PEG1000 was higher than 90%, the pure water flux was higher than 40 LMH (60psi), and it can withstand 20,000 ppm.h NaClO solution cleaning. When the post treatment processes was adjusted, the salt rejection rate of NaCl solution (250 ppm) reached 45.5%, and the flux reached 62.2 LMH.

Key Words
composite nanofiltration membrane; high flux; oxidation resistance; solution coating method; sulfonated polysulfone

Address
Feiyue Yu and Qinglei Zhang: Beijing Originwater Membrane Technology Co., Ltd. Beijing, 101407, P.R. China

Zhiqiang Pei, Xuexuan Yang and Yanbin Lu: Beijing Originwater Separation Membrane Technology Co., Ltd. Beijing, 101407, P.R. China

Xi Li: Cansino Biotech Co., Ltd. Tianjin, 300457, P.R. China

Abstract
Emulsion Liquid Membrane (ELM) is a prominent technique for the separation of heavy metal ions from wastewater due to the fast extraction and is a single-stage operation of stripping-extraction. The selection of the components (Surfactant and Carrier) of ELM is a very significant step for its preparation. In the ELM technique, the primary water- in-oil (W/O) emulsion is emulsified in water to produce water-in-oil-in-water (W/O/W) emulsion. The water in oil emulsion was prepared by mixing the membrane phase and internal phase. To prepare the membrane phase, the extractant D2EHPA (di-2-ethylhexylphosphoric acid) was used as a mobile carrier, Span-80 as a surfactant, and Paraffin as a diluent. Moreover, the internal (receiving) phase was prepared by dissolving sulphuric acid in water. Di-(2- ethylhexyl) phosphoric acid such as surfactant concentration, carrier concentration, sulphuric acid concentration in the receiving (internal) phase, agitation time (emulsion phase and feed phase), the volume ratio of the membrane phase to the receiving phase, the volume ratio of the external feed phase to the primary water-in-oil emulsion and pH of feed were studied on the percentage extraction of metal ions at 20°C. The results show that it is possible to remove 78% for As(V), 98% for Cd(II), and 99% for Pb(II). Emulsion Liquid Membrane (ELM) is a well-known technique for separating heavy metal ions from wastewater due to the fast extraction and is a single-stage operation of stripping-extraction. The selection of ELM components (Surfactant and Carrier) is a very significant step in its preparation. In the ELM technique, the primary water-in-oil (W/O) emulsion is emulsified to produce water-in-oil-in-water (W/O/W) emulsion. The water in the oil emulsion was prepared by mixing the membrane and internal phases. The extractant D2EHPA (di-2-ethylhexylphosphoric acid) was used as a mobile carrier, Span-80 as a surfactant, and Paraffin as a diluent. Moreover, the internal (receiving) phase was prepared by dissolving sulphuric acid in water. Di-(2-ethylhexyl) phosphoric acid such as surfactant concentration, carrier concentration, sulphuric acid concentration in the receiving (internal) phase, agitation time (emulsion phase and feed phase), the volume ratio of the membrane phase to the receiving phase, the volume ratio of the external feed phase to the primary water-in-oil emulsion and pH of feed were studied on the percentage extraction of metal ions at 20°C. The results show that it is possible to remove 78% for As(V), 98% for Cd(II), and 99% for Pb(II).

Key Words
D2EHPA; emulsion liquid membrane; metal ions extraction; paraffin; span 80; wastewater treatment

Address
Rajeev K. Dohare, Vishal Agarwal, Naresh K. Choudhary, Sameer Imdad, Kailash Singh and Madhu Agarwal: Department of Chemical Engineering Malaviya NationlaI Institute of Technology Jaipur 302-017 India


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