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CONTENTS
Volume 12, Number 1, January 2021
 

Abstract
This study optimized the chemical cleaning process of discarded RO membranes for reuse in less demanding separation processes. The effect of physicochemical parameters, including the temperature, cleaning time, pH of the cleaning solution, and addition of additives, on the cleaning process was investigated. The membrane performance was evaluated by testing the flux recovery rate and salt rejection before and after the cleaning process. High temperatures (45-50oC) resulted in a better flux recovery rate of 71% with more than 80% salt rejection. Equal time for acid and base cleaning 3-3 h presented a 72.43% flux recovery rate with salt rejection above 85%. During acid and base cleaning, the best results were achieved at pH values of 3.0 and 12.0, respectively. Moreover, 0.05% concentration of ethylenediaminetetraacetic acid presented 72.3% flux recovery, while 69.2% flux was achieved using sodium dodecyl sulfate with a concentration of 0.5%; both showed >80% salt rejection, indicating no damage to the active layer of the membrane. Conversely, 0.5% concentration of sodium percarbonate showed 83.1% flux recovery and 0.005% concentration of sodium hypochlorite presented 85.2% flux recovery, while a high concentration of these chemicals resulted in oxidation of the membrane that caused a reduction in salt rejection.

Key Words
chemical cleaning; RO membrane; optimization; reuse

Address
Minsu Jung, Muhammad Yaqub and Wontae Lee: Department of Environmental Engineering, Kumoh National Institute of Technology, 61 Daehak–ro, Gumi 39177, Republic of Korea

Abstract
A novel activated carbon produced from cherry laurel (Laurocerasus officinalisRoem.) seeds (CLSAC) by chemical activation with ZnCl2 was used as an adsorbent to remove Cr(VI) ions from aqueous solutions. CLSAC was characterized by several techniques and the adsorption experiments were performed in a batch model adsorption technique. The effects of various experimental parameters were investigated as a function of solution pH, contact time, initial Cr(VI) concentration, CLSAC concentration, and temperature. The monolayer adsorption capacity of CLSAC was found to be 41.67 mg g-1 for 5.0 g L-1 of CLSAC concentration and, it was concluded that CLSAC can be used as an effective adsorbent for removal of Cr(VI) from waters and wastewaters.

Key Words
chromium(VI); adsorption; isotherms; kinetics; thermodynamics

Address
Nurcan Öztürk: Department of Civil Engineering, Faculty of Technology, Karadeniz Technical University, 61830 Trabzon, Turkey
Murat Yazar and Ali Gündoğdu: Department of Pharmacy Services, Maçka Vocational School, Karadeniz Technical University, 61750 Trabzon, Turkey
Celal Duran and Hasan Basri Şentürk: Department of Chemistry, Faculty of Science, Karadeniz Technical University, 61080 Trabzon, Turkey
Mustafa Soylak: Department of Chemistry, Faculty of Science, Erciyes University, 38039 Kayseri, Turkey


Abstract
A POM-membrane was fabricated by immobilizing a keggin type polyoxometalate (POM) H5PV2Mo10O40 onto the surface of microporous flat-sheet polymeric polyvinylidene fluoride (PVFD) membrane using a chemical deposition method. The POM-membrane was characterized by FT-IR, SEM and EDX to confirm existing of the POM onto the membrane surface. The POM-membrane was used to remove an anionic textile dye (Reactive Black 5 named as an RB5) from aqueous phases with a cross-flow membrane filtration and a batch adsorption system. The dye removal efficiency of the POM-membrane using the cross-flow membrane filtration system and the batch adsorption system was about 88% and 98%, respectively. The influence factors such as contact time, adsorbent dosage, pH, and initial dye concentration were investigated to understand the adsorption mechanism of the RB5 dye onto the POM-membrane. To find the best fitting isotherm model, Langmuir, Freundlich, BET and Harkins-Jura isotherm models were used to analyze the experimental data. The isotherm analysis showed that the Langmuir isotherm model was found to the best fit for the adsorption data (R 2=0.9982, qmax=24.87 mg/g). Also, adsorption kinetic models showed the pseudo second order kinetic model was found the best model to fit the experimental data (R2=0.9989, q=8.29 mg/g, C0=15 ppm). Moreover, after four times regeneration with HNO3 acid, the POM-membrane showed high regenerability without losing dye adsorption capacity.

Key Words
polyoxometalates; membrane; adsorption; dye removal; reactive black

Address
Department of Environmental Engineering, Zonguldak Bulent Ecevit University, Zonguldak, Turkey

Abstract
This paper presents the multiscale calculation results of the very fast volume transport in micro/nano cylindrical tubes with the wall slippage. There simultaneously occurs the adsorbed layer flow and the intermediate continuum fluid flow which are respectively on different scales. The modeled fluid is water and the tube wall is somewhat hydrophobic. The calculation shows that the power loss on the tube no more than 1.0 Watt/m can generate the wall slippage even if the fluid-tube wall interfacial shear strength is 1 MPa; The power loss on the scale 104 Watt/m produces the volume flow rate through the tube more than one hundred times higher than the classical hydrodynamic theory calculation even if the fluid-tube wall interfacial shear strength is 1 MPa. When the wall slippage occurs, the volume flow rate through the tube is in direct proportion to the power loss on the tube but in inverse proportion to the fluid-tube wall interfacial shear strength. For low interfacial shear strengths such as no more than 1 kPa, the transport in the tube appears very fast with the magnitude more than 4 orders higher than the classical calculation if the power loss on the tube is on the scale 104 Watt/m.

Key Words
adsorbed layer; micro/nano tube; multiscale flow; transport; wall slippage

Address
Zhipeng Tang: College of Mechanical Engineering, Changzhou Vocational Institute of Mechatronic Technology, Changzhou, Jiangsu Province, China
Yongbin Zhang: College of Mechanical Engineering, Changzhou University, Changzhou, Jiangsu Province, China


Abstract
The Commercial polymeric membranes like Polysulfone (PSF), Polyvinylidene difluoride (PVDF) and Polyacrylonitrile (PAN) which are an integral part of water purification investigation were chosen for the shockwave (SW) exposure experiment. These membranes were prepared by blending polymer (wt. %) / DMF (solvent) followed by phaseinversion casting technique. Shockwaves are generated by using Reddy Tube lab module (Table-top Shocktube) with range of pressure (1.5, 2.5 and 5 bar). Understanding the changes in membrane before and after shock wave treatment by parameters, i.e., pure water flux (PWF), rejection (%), porosity, surface roughness (AFM), morphology (SEM) and contact angle which can significantly affect the membrane's performance. Flux values PSf membranes shows increase, 465 (pristine) to 524 (1.5wt%) LMH at 50 Psi pressure and similar enhancement was observed at 100Psi (625 to 696 LMH). Porosity also shows improvement from 73.6% to 76.84% for 15wt% PSf membranes. It was observed that membranes made of polymers such as PAN and PSF (of high w/w %) exhibits some resistance against shockwaves impact and are stable compared to other membranes. Shockwave pressure of up to 1.5 bar was sufficient enough to change properties which are crucial for performance. Membranes exposed to a maximum pressure of 5 bar completely scratched the surface and with minimum pressure of 1.5bar is optimum enough to improve the water flux and other parameters. Initial results proved that SW may be suitable alternative route to minimize/control membrane fouling and improve efficiency.

Key Words
shockwaves; polymer; membrane; fouling; surface roughness; morphology

Address
D. Shanthana Lakshmi and Mayank Saxena: RO Membrane Division, CSIR-Central Salt and Marine Chemical Research Institute, Bhavnagar - 364002, India
Shivakarthik Ekambaram and Bhalamurugan Sivaraman: Atomic, Molecular, and Optical Physics Division, Physical Research Laboratory, Ahmedabad - 380009, India


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