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CONTENTS
Volume 13, Number 6, November 2022
 


Abstract
Carbon nanotubes (CNTs), due to their excellent physical, chemical and mechanical properties and their ability to prepare new membranes with attractive properties, have found applications in water and wastewater technology. CNT functionalization, which involves the introduction of different types of functional groups into pure CNTs, improves the capabilities of CNT membranes for water and wastewater treatment. It turns out that CNT-based membranes have many advantages, including enhanced water permeability, high selectivity and anti-fouling properties. However, their full-scale application is still limited by their high cost. With their tremendous separation efficiency, low biofouling potential and ultra-high water flux, CNT membranes have the potential to be a leading technology in water treatment in the future, especially in desalination.

Key Words
carbon nanotube; CNT functionalization; CNT membranes; mixed matrix CNT membranes; water and wastewater treatment

Address
Michal Bodzek: Institute of Environmental Engineering Polish Academy of Sciences, Marii Curie-Sklodowskiej 34, 41-819 Zabrze, Poland

Krystyna Konieczny: Silesian University of Technology, 44-100 Gliwice, Poland

Anna Kwiecińska-Mydlak: Institute for Chemical Processing of Coal, 41-800 Zabrze, Poland

Abstract
In this study, cement/PVDF hollow-fiber hybrid membranes were prepared via a mixed process of diffusion- induced phase separation and hydration. The presence of X-ray diffraction peaks of Ca(OH)2, an AFt phase, an AFm phase, and C-S-H phase confirmed the hydration reaction. Good hydrophilicity was obtained. The cross-sectional and surface morphologies of the hybrid membranes showed that an asymmetric pore structure was formed. Hydration products comprising parallel plates of Ca(OH)2, fibrous ettringite AFt, and granulated particles AFm were obtained gradually. For the hybrid membranes cured for different time, the pore-size distribution was similar but the porosity decreased because of blocking of the hydration products. In addition, the water flux decreased with hydration time, and carbon retention was 90% after 5 h of rejection treatment. Almost all the Zn2+ ions were adsorbed by the hybrid membrane. The above results proved that the obtained membrane could be alternative as basement membrane for separation application.

Key Words
adsorption; asymmetric pore structure; basement membrane; cement/PVDF hybrid membrane; rejection

Address
Yabin Zhang, Xiongfei Du and Taotao Zhao: State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, 399 Binshuixi Road, Xiqing District, Tianjin 300380, People's Republic of China


Abstract
The natural hydrology and geological conditions of Xintian County was investigated, the development law of regional karst fissures was studied, the groundwater was collected and tested through a large-scale collection of groundwater to obtain the change law of chemical characteristics and water quality characteristics of groundwater, and the water quality evaluation was carried out for the regional karst groundwater in this paper. The results show that, the whole area is dominated by carbonate rock distribution areas, and the distribution of water systems is relatively developed. The strata are distributed from the Lower Paleozoic Cambrian to the Cenozoic Quaternary, and contain multiple first-order folds. The regional karst dynamic action is strong, and many tunnels or caves of different scales were shown, which are conducive to the enrichment of groundwater. Karst groundwater is neutral and alkaline water, the water is clear and transparent with good taste, and meets the national drinking water hygiene standards. The content of toxic trace elements and fluoride in the water source is generally lower than the limit value specified by the national standard and the accumulated toxic heavy metals is never found. The overall water quality is of good quality and suitable for the development and utilization of various purposes.

Key Words
karst fissure; underground water; water quality; water chemical characteristics

Address
Xin Zhou, Tengfei Yao, Can Wang, Jian Ou, Pengfei Zheng and
Kaihong Chen: Hunan Geological Disaster Emergency Rescue Technology Center, Hunan Institute of Geological Disaster Investigation and Monitoring, Changsha 410029, China

Xiting Long: Hunan Geological Disaster Emergency Rescue Technology Center, Hunan Institute of Geological Disaster Investigation and Monitoring, Changsha 410029, China/ Shenzhen Key Laboratory of Deep Underground Engineering Sciences and Green Energy, Shenzhen University, Shenzhen 518060, China/ Sichuan University, State Key Lab Hydraul & Mt River Engn, Chengdu 610065, China

Abstract
Theoretical calculation results are presented for the enhancement of the water mass flow rate through the hydrophobic micro/nano pores in the membrane respectively on the micrometer and nanometer scales. The water-pore wall interfacial slippage is considered. When the pore diameter is critically low (less than 1.82nm), the water flow in the nanopore is non-continuum and described by the nanoscale flow equation; Otherwise, the water flow is essentially multiscale consisting of both the adsorbed boundary layer flow and the intermediate continuum water flow, and it is described by the multiscale flow equation. For no wall slippage, the calculated water flow rate through the pore is very close to the classical hydrodynamic theory calculation if the pore diameter (d) is larger than 1.0nm, however it is considerably smaller than the conventional calculation if d is less than 1.0nm because of the non-continuum effect of the water film. When the driving power loss on the pore is larger than the critical value, the wall slippage occurs, and it results in the different scales of the enhancement of the water flow rate through the pore which are strongly dependent on both the pore diameter and the driving power loss on the pore. Both the pressure drop and the critical power loss on the pore for starting the wall slippage are also strongly dependent on the pore diameter.

Key Words
hydrophobic wall; mass transfer; membrane; multiscale; nanopore; wall slippage

Address
Mian Wang: School of Electronic Engineering, Changzhou College of Information Technology, Changzhou, 213164, Jiangsu Province, China

Yongbin Zhang: College of Mechanical Engineering, Changzhou University, Changzhou, 213164, Jiangsu Province, China

Abstract
Copper-based Metal-organic framework (MOF) namely ([Cu (INA)2]-MOF) is synthesized by ball milling and characterized using scanning electron microscopy (SEM) for the topography, microstructure, and elemental evidence determination, powdered X-ray diffraction (XRD) for the crystallinity measurement, thermogravimetric (TG) analysis was performed to determine the thermal stability of the material, and Fourier transformed infrared (FTIR) spectroscopy for functional groups identification. The use of [Cu (INA)2]-MOF as hazardous removal material of Β-agonists as persistent hazardous micro-pollutants in our environmental water is first reported in this study. The removal efficiency of the Cu-MOF is successfully determined to be 97.7% within 40 minutes, and the MOF has established an exceptional removal capacity of 835 mg L-1 with 95 % percent removal on Clenbuterol (CLB) even after the 5th consecutive cycle. The Langmuir model of the adsorption isotherms was shown to be more favourable, while the pseudo-second-order model was found to be favoured in the kinetics. The reaction was exothermic and spontaneous from a thermodynamic standpoint, and the higher temperatures were unfavourable for the adsorption study of the CLB. As a result, the studied MOF have shown promising properties as possible adsorbents for the removal of CLB in wastewater.

Key Words
ball-mill; Β-agonists; clenbuterol; metal-organic frameworks (MOFs)

Address
Marinah Mohd Ariffin, Saw Hong Loh, Wan Mohd Afiq Wan Mohd Khalik and Hanis Mohd Yusoff: Faculty of Science and Marine Environment, Universiti Malaysia Terengganu

Usman Armaya'u: Faculty of Science and Marine Environment, Universiti Malaysia Terengganu/ Faculty of Applied Sciences, Al-Qalam University Katsina, Nigeria



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