الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
He use of nano-materials has increased exponentially in the last decade and it promises to rise even further in the future. Engineered nanoparticles (ENPs), in particular, have found hundreds and thousands of applications in various technologies and processes especially in the environmental sector. Inevitably, a quantity of ENPs will be found in industrial and domestic wastes and as a consequence in water resources. Due to their ultra-small size, nanoparticles may not only pose new hazards for the aquatic environment, organisms and human health, but also cause low separation efficiency by classical water treatments processes. There is a vital need to understand the fate of nanoparticles during the water/wastewater treatment process and to look at innovative techniques to remove them. Despite the need, very few studies are available on the removal of nanoparticles. Thus, it would be an important challenge to develop a specific treatment to remove ENPs from wastewater.
Nano-filtration membranes (NF) are very effective in removing dissolved ions, organic solutes and nano-scale pollutants. However, high pressures (100–1000 psi) are required to operate NF membranes. The nano-filtration membrane technique is not preferred for use in the treatment of wastewater containing nano-scale particles due to the fouling of membrane problems which results in decreasing treated water production. Conversely, ultra-filtration membranes (UF) require much lower pressures (5–60 psi) and the fouling problem is less, but unfortunately, they are not effective in retaining dissolved ions, organic solutes and nano-scale pollutants. Therefore, in the present study use of a coagulation/flocculation step is employed as a pre-treatment process to enhance the ultra-filtration process. The present work investigates the use of membrane filtration in conjunction with
coagulation/flocculation processes for improving the nano-sized materials removal with low cost of energy and high efficiency of removal. The coagulation/flocculation pre-treatment system was coupled with a hollow fibers ultrafiltration membrane (HF-UFM) unit. Synthetic wastewater containing different concentrations of ENPs was used to evaluate the efficiency of the system and different kinds of coagulants were used for the treatment process; viz., a) cationic polymer (Magnafloc LT31), b) anionic polymer (Magnafloc10), and c) inorganic polymer (Dynafloc30).
The use of coagulation as a pretreatment alternative to improve the performance of membrane filtration process for nano-materials removal from wastewater was studied with cross-flow ultrafiltration membrane filtration apparatus. Various processes and operating conditions of the treatment process were examined, including coagulant type and dosage, pH, ionic strength, and trans-membrane pressure. Coagulant dosages and pH values were controlled by using jar-testing and turbidity. Concentrations of ENPs were followed before and after each stage using a turbidity meter and spectrophotometer, respectively. The results were highly positive and the coagulation/flocculation/sedimentation (CFS) process improved the performance of filtration process and reduced the flux decline by decreasing the fouling of the membrane. The removal of nano-materials reached up to 97% in most cases and the efficiency of turbidity removal reached about 98%. The cationic coagulant recorded impressive results with either silica or copper oxide nanoparticles in comparison with the other coagulant types, in addition the other coagulants recorded good results too, but with using higher amount of coagulant dosages.