No abstract

In this study the permeation and separation characteristics of acetone/water mixtures were investigated by vapor permeation (VP) and vapor permeation with temperature difference (TDVP) methods using sodium alginate/poly (vinyl pyrrolidone) (NaAlg/PVP) membranes crosslinked with calcium chloride. Membranes were prepared in different ratios (w/w) (100/0, 95/5, 90/10, 85/15, 80/20, 75/25) of NaAlg/PVP. The effects of blend ratio, feed composition, operating temperature and temperature of the membrane surroundings on the separation characteristics (separation factor, permeation rate) were studied for the acetone/water mixtures. The optimum NaAlg/PVP ratio, operating temperature and feed composition were determined as 75/25 (w/w), 40°C, and 20 wt% acetone, respectively. The separation factors decreased whereas permeation rates increased with the increase in permeation temperature for both VP and TDVP methods. In the TDVP method separation factors increased and the permeation rates decreased as the temperature of the membrane surroundings decreased. It was as observed that the permeation rate in TDVP method was lower than in VP; however the highest separation factor was obtained with TDVP method as 73.

No abstract

In this study, graft copolymerization of N-vinylpyrrolidone (N-VP) onto starch was carried out in an aqueous medium using azobisisobutyronitrile (AIBN) as initiator. The variables affecting the graft copolymerization, such as monomer and initiator concentrations, reaction time and temperature, were thoroughly examined. In general, grafting of N-vinylpyrrolidone onto starch increased with the increase in time and monomer concentration up to a certain value and then leveled off. Similarly, increase both in initiator concentration and temperature first favored and than impeded the grafting reaction. Optimum conditions established for grafting were as follows: N-VP = 0.7 M, AIBN = 1.5610 -3 M, T = 707C and t = 5 h. Structural changes of the grafted starch were followed by FTIR, intrinsic viscosity and water absorption capacity studies.

No abstract