عنوان مقاله [English]
Background and objectives
The objective of this research was preparation of ultrafiltration membrane from three types of cellulose acetate which obtained from three cellulose sources. Membranes were applied for white water treatment of tissue production line. With regards to previous studies, ultrafiltration membranes reduced 100% of total solids and 10-20% of COD in white water treatment. In another study on Nano filtration of concentrate solution of white water ultrafiltration of recycle paper mill showed that COD of Nano filtration permeates (9,800–12,900 mg/L) by NTR-7450 membrane was decreased about 68-75% by NTR-7450 membrane.
Materials and methods
Three types of cellulose acetate from three sources of cellulose (SEW and Kraft pulp of milkweed wood, and soda pulp of cotton linter) were utilized for producing membrane with phase inversion method. Properties of membrane such as pure water flux, purification of white water and fouling were investigated by closed cell under the presser of 1 to 5 bars. The samples of white water were analyzed after and before purification based on Standard methods for the examination of water and wastewater (1998). In addition, the SEM images were taken from membranes before and after ultrafiltration of white water.
Cellulose acetate from Kraft pulp of Milkweed wood and Soda pulp of cotton linter indicated more porosity and water content in their membranes due to their low DS and crystallite. Actually low DS led to more hydrophilic in these cellulose acetates. The cellulose acetate of SEW pulp showed the low porosity and water content in membrane due to more DS and crystallite. The pure water flux of its membrane was located in rang of ultrafiltration. The SEM pictures from cross section of membranes illustrated that the pore size from water content and pure water flux were larger than the pore size in SEM images. It was due to large hole in the thickness of membranes. The results of ultrafiltration of tissue machine white water which obtained from CA-membrane (SM5) showed that it quite efficient for removing pollution from white water. BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), TS (Total solids) and turbidity were reduced 72.3%, 79.8%, 99.8% and 98.1% respectively.
The cellulose acetate type in terms of DS and crystalinity has considerable impact on membrane properties. Cellulose acetate of SEW pulp with more DS and crystalinity results in ultrafiltration membrane with smaller pores and lower water absorption than Cellulose acetate of milkweed Kraft pulp and soda pulp of cotton linters. The white water ultrafiltration of tissue factory by cellulose acetate membrane (SM5) showed that it considerably able to remove pollution from white water.