HASAN GAFRI - Academia.edu (original) (raw)
Papers by HASAN GAFRI
DESALINATION AND WATER TREATMENT
The impacts of the acidity and ionic strength of the solutions were evaluated on the electrical p... more The impacts of the acidity and ionic strength of the solutions were evaluated on the electrical potential of the surfaces as well as the interaction of Pseudomonas putida to quartz and hematite. Zeta potential analysis was performed using the streaming potential technique. Experimental results were performed by the flow cell method. Finally, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory has been applied to describe bacterial-mineral attachment in terms of the sum of repulsive acid-base and electrostatic interaction energies, and attractive van der Waals interaction energies. The results indicate that the zeta potential is obviously influenced by the presence of bacteria, electrolyte concentration, and pH regions. At higher ionic strengths, charge effects on the bacterial cell surface increase adherence by suppressing the thickness of the diffuse double layer. At pH 5-6, at all ionic strengths, the bacteria adhered more on the surfaces of the minerals. Hematite coupons represented the greatest adhesion at pH 5-6 and an ionic strength 0.1 M. XDLVO theory for the attachment of P. putida to the minerals also confirmed the experimental outcomes. The information obtained in this study is of fundamental significance for the understanding of the survival and transport of bacteria in water distribution, groundwater, and soil systems.
Journal of Polymers and the Environment, 2019
Biofouling is one of the major challenges of membrane technology in water and wastewater treatmen... more Biofouling is one of the major challenges of membrane technology in water and wastewater treatments. In this work, we investigated the potential of chitosan/chitosan powder activated carbon (PAC) composite to reduce biofouling of membrane. Polyethersulfone (PES) membrane was modified with chitosan/chitosan-PAC composite and the performance of the modified membrane in river water treatment was evaluated. The effect of different concentration of polymer [(chitosan: 2.0% (w/v), 1.0% (w/v), 0.5% (w/v), 0.1% (w/v), and chitosan-PAC composite: 1.5% (w/v) − 1.0 (w/v), 0.5% (w/v) − 0.2% (w/v)] on the membrane performance was examined. The properties of the modified membrane such as roughness, morphology, surface functional groups wettability, swelling ration and contact angle were analyzed. The membrane water flux increased with increasing chitosan concentration from 0.1% (w/v) (7.36 mL/cm 2 m) to 1.0% (w/v) (9.46 mL/cm 2 m), but decreased at (2.0 w/v) (5.30 mL/cm 2 m). However, the water flux for chitosan-PAC-modified membrane was about 6.86 mL/cm 2 m, which was slightly lower than unmodified membrane (7.36 mL/cm 2 m). The chitosan-modified membrane resulted in 28% reduction in total coliform bacteria while the chitosan-PAC-modified membrane reduced 45% of the total coliform bacteria. These results indicated that chitosan and chitosan-PAC composite could enhance the anti-microbial properties of PES membrane, which would prevent biofilm formation during water treatment.
Reviews in Chemical Engineering, 2019
Bacterial adhesion to surfaces is related to several factors, such as surface charge, surface ene... more Bacterial adhesion to surfaces is related to several factors, such as surface charge, surface energy, and substrate characteristics (leading to the formation of biofilms). Organisms are dominant in most environmental, industrial, and medical problems and processes that are of interest to microbiologists. Biofilm cells are at least 500 times more resistant to antibacterial agents compared to planktonic cells. The usage of ultrafiltration membranes is fast becoming popular for water treatment. Membrane lifetime and permeate flux are primarily affected by the phenomena of microbial accumulation and fouling at the membrane’s surface. This review intends to understand the mechanism of membrane fouling by bacterial attachment on polymeric ultrafiltration membrane modified by natural antimicrobial polymers (chitosan) combined with powder activated carbon. Also, to guide future research on membrane water treatment processes, adhesion prediction using the extended Derjaguin-Landau-Verwey-Ove...
Rivers and lakes are primary sources of water for towns and villages. However, the quality of the... more Rivers and lakes are primary sources of water for towns and villages. However, the quality of these water bodies is currently deteriorating due to urbanization, industrialization, farming, and other anthropogenic activities. This study was conducted within January 25 th to November 26 th 2017at designated points at Pantai River, Anak Air Batu River, and Varsity Lake, University of Malaya, Kuala Lumpur, Malaysia, where the physic-chemical and biological characteristics were determined in order to increase the statistical basis of these regions. In the physic-chemical evaluation of the water samples, diverse parameters were measured, such as the pH, turbidity, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Suspended Solids (SS), ammonia, phosphate and nitrate attention, and biology. These parameters were compared with the Water Quality Index (WQI) standards of water quality. Overall, the result showed that the DO, BOD, COD, and SS fall within cla...
DESALINATION AND WATER TREATMENT
The impacts of the acidity and ionic strength of the solutions were evaluated on the electrical p... more The impacts of the acidity and ionic strength of the solutions were evaluated on the electrical potential of the surfaces as well as the interaction of Pseudomonas putida to quartz and hematite. Zeta potential analysis was performed using the streaming potential technique. Experimental results were performed by the flow cell method. Finally, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory has been applied to describe bacterial-mineral attachment in terms of the sum of repulsive acid-base and electrostatic interaction energies, and attractive van der Waals interaction energies. The results indicate that the zeta potential is obviously influenced by the presence of bacteria, electrolyte concentration, and pH regions. At higher ionic strengths, charge effects on the bacterial cell surface increase adherence by suppressing the thickness of the diffuse double layer. At pH 5-6, at all ionic strengths, the bacteria adhered more on the surfaces of the minerals. Hematite coupons represented the greatest adhesion at pH 5-6 and an ionic strength 0.1 M. XDLVO theory for the attachment of P. putida to the minerals also confirmed the experimental outcomes. The information obtained in this study is of fundamental significance for the understanding of the survival and transport of bacteria in water distribution, groundwater, and soil systems.
Journal of Polymers and the Environment, 2019
Biofouling is one of the major challenges of membrane technology in water and wastewater treatmen... more Biofouling is one of the major challenges of membrane technology in water and wastewater treatments. In this work, we investigated the potential of chitosan/chitosan powder activated carbon (PAC) composite to reduce biofouling of membrane. Polyethersulfone (PES) membrane was modified with chitosan/chitosan-PAC composite and the performance of the modified membrane in river water treatment was evaluated. The effect of different concentration of polymer [(chitosan: 2.0% (w/v), 1.0% (w/v), 0.5% (w/v), 0.1% (w/v), and chitosan-PAC composite: 1.5% (w/v) − 1.0 (w/v), 0.5% (w/v) − 0.2% (w/v)] on the membrane performance was examined. The properties of the modified membrane such as roughness, morphology, surface functional groups wettability, swelling ration and contact angle were analyzed. The membrane water flux increased with increasing chitosan concentration from 0.1% (w/v) (7.36 mL/cm 2 m) to 1.0% (w/v) (9.46 mL/cm 2 m), but decreased at (2.0 w/v) (5.30 mL/cm 2 m). However, the water flux for chitosan-PAC-modified membrane was about 6.86 mL/cm 2 m, which was slightly lower than unmodified membrane (7.36 mL/cm 2 m). The chitosan-modified membrane resulted in 28% reduction in total coliform bacteria while the chitosan-PAC-modified membrane reduced 45% of the total coliform bacteria. These results indicated that chitosan and chitosan-PAC composite could enhance the anti-microbial properties of PES membrane, which would prevent biofilm formation during water treatment.
Reviews in Chemical Engineering, 2019
Bacterial adhesion to surfaces is related to several factors, such as surface charge, surface ene... more Bacterial adhesion to surfaces is related to several factors, such as surface charge, surface energy, and substrate characteristics (leading to the formation of biofilms). Organisms are dominant in most environmental, industrial, and medical problems and processes that are of interest to microbiologists. Biofilm cells are at least 500 times more resistant to antibacterial agents compared to planktonic cells. The usage of ultrafiltration membranes is fast becoming popular for water treatment. Membrane lifetime and permeate flux are primarily affected by the phenomena of microbial accumulation and fouling at the membrane’s surface. This review intends to understand the mechanism of membrane fouling by bacterial attachment on polymeric ultrafiltration membrane modified by natural antimicrobial polymers (chitosan) combined with powder activated carbon. Also, to guide future research on membrane water treatment processes, adhesion prediction using the extended Derjaguin-Landau-Verwey-Ove...
Rivers and lakes are primary sources of water for towns and villages. However, the quality of the... more Rivers and lakes are primary sources of water for towns and villages. However, the quality of these water bodies is currently deteriorating due to urbanization, industrialization, farming, and other anthropogenic activities. This study was conducted within January 25 th to November 26 th 2017at designated points at Pantai River, Anak Air Batu River, and Varsity Lake, University of Malaya, Kuala Lumpur, Malaysia, where the physic-chemical and biological characteristics were determined in order to increase the statistical basis of these regions. In the physic-chemical evaluation of the water samples, diverse parameters were measured, such as the pH, turbidity, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Suspended Solids (SS), ammonia, phosphate and nitrate attention, and biology. These parameters were compared with the Water Quality Index (WQI) standards of water quality. Overall, the result showed that the DO, BOD, COD, and SS fall within cla...