الفهرس 
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Abstract
Water treatment processes are increasingly necessary due to environmental pollution and the growing needs of the global population. Oily wastewater is one of environmental pollutes contains sticky oily compounds toxic, chemicals, and miscible organic at the concentrations of 100 to 1000 mg/L which are damaging to human health and have a negative influence on the environment. Among various water treatment technologies, filtration membrane technology is considered a good alternative for secondary and tertiary treatment. Polyacrylonitrile (PAN) is now extensively used as polymeric material in membrane formation for oil-water separation in ultrafiltration, nanofiltration, and reverse osmosis because of its chemical and thermal stability.
In this work different molecular weights of polyacrylonitrile (PAN) homopolymers were prepared based on the process of aqueous phase precipitation polymerization of acrylonitrile. The polymerization processes were investigated at different monomer and initiator ratios, and at different pHs. The results showed that the molecular weight of prepared polyacrylonitrile rose with raising the monomer ratio, and at the same time conversion percent decline. This is due to the increase in monomer concentration which leads to an increase in the formation of precipitated radical oligomeric chains. These precipitated radical oligomeric chains can absorb the radicals of AN monomer, and consequently the propagation process could continue and leading to an increase in polymerization rate.
However, when the initiator ratios were increased, the molecular weight decreased and the conversion percent increased, since a higher initiator concentration initiates more radicals, resulting in many propagated chains, fast chain termination, and a low molecular weight polymer with a high conversion yield. The reaction was then optimized at pH 2.25 with a monomer concentration of 90 g/L for 6 hours, resulting in an appropriate molecular weight (depending on initiator concentration) and a high conversion percent (84 %).
The structure of prepared PAN were characterized by FTIR, H1NMR, XRD, TGA, and DSC. XRD findings demonstrated that the crystallinity of the prepared polymers was decreased with increasing its molecular weight, due to the incorporation of high molecular weight chains prevent the interactions between intermolecular C≡N groups. As well as thermal examination (TGA) revealed that greater molecular weight PAN is more thermally stable than lower molecular weight, may due to the chain length of polymers.
Ultrafiltration membranes were fabricated using the prepared PAN by phase inversion approach, as a flat sheet forms for separation of oil emulsion in water. Ultrafiltration experiments were conducted by RO lab scale unit using 900 ppm castor oil emulsified by SDS in water as feed solution, at flow rate 160 l/h, and 3 bar of operating pressure. The results showed that membrane roughness, porosity, and pore size increase with PAN molecular weight due to decreasing the entropy of the solution system leading to increase in Gibbs free energy which make the system unstable going to faster solvent-non solvent exchange, and leads to formation of more porous membrane with larger pore size. Otherwise, contact angle values increase with increasing and molecular weight, due to the roughness nature of membrane surface which increases with increase of PAN molecular weight. Furthermore, the oil emulsion separation performance of theses membranes depends on their porosity and pore size.
from all obtained results, the PAN1 and PAN4 membranes are the best membranes to separate the oil from oily-water emulsion, due to their high porosity (97.5 and 96.3% respectively) and high pore size (63.8 and 66.5 nm respectively), and also their high performances of flux (126 and 125 Lm-2h-1 respectively) and rejection (99.7 and 99.5 % respectively). However, PAN4 has a lower fouling tendency than PAN1.
The optimally prepared membrane performs very well for the purification of real oilfield wastewater (sample of crude oil that contains 1200 ppm from emulsion crude oil and 11,000 ppm from salts is fetched from North Baharia Petroleum Company (NORPETCO) located in Egypt), and a significant permeate flux is obtained with crude oil rejection reached 99.1% and its maximum flux reached ∼102 (Lm−2h−1). Therefore, it could be deduced that those membranes could be applied in mass scale in ultrafiltration process of salted oily wastewater.