1. Blend membrane by using the PVA/chitosan and crosslinking with TEOS for pervaporation separation for water acetic acid mixtures
Shivshankar Chaudhari1, YongSung Kwon1,Myung Jun Moon1,San Tak Kwak Min1 Young Shon1 †
YouIn Park2, HyeRim Song2, SeungEun Nam2
1 Department of Industrial and Engineering Chemistry, Pukyong National University
Busan-city, Republic of Korea
2 Korea Research Institute of Chemical Technology †
Korea Research Institute of Chemical Technology
Pukyong National University
Introduction
Experimental
Proposed reaction scheme of membrane synthesis
Acetic acid is an important chemical reagent and industrial chemical. The global demand for acetic acid has been estimated at around 6.5 million metric tons per year, of that amount approximately 1.5 Mt/a is prepared by recycling. The separation of acetic acid from water using the distillation has a very high energy process and cost making it inefficient since its required azeotropic distillation. Among the propose alternative methods, pervaporation is promising approach to separate acetic acid aqueous solution. In fact membrane based processes are categorized as ecofriendly and clean process.
Pervaporation is membrane process for separation liquid mixture by partial vaporization of through dense membrane. It consist of membrane to the selective side that feed mixture is directly in contact where as permeate remove in the form of vapor from the other side, the driving force can be created by applying the vacuum at the permeate side below the partial vapor the feed liquid.
PVA is semi crystalline , hydrophilic polymer aliphatic polymer but it has relatively lower stability in water,when crosslinked with the suitable crosslinking agent, it become more compact, and result in decrease in free volume.Tetraethyl ortho silicate can be used as crosslinking agent to stabilized the PVA in water. But using PVA –TEOS crosslinked membrane performance in pervaporation dehydration of various organic mixtures obtained opposite trend in terms of flux and separation factor. Membrane performance not only depend upon the chemical property of the membrane components but also it depends on the structure of its components So decrease in hydrophilicity and free volume due to crosslinking of PVA could be restrained by addition of chitosan in to the membrane,since chitosan is hydrophilic natural polymer.
In this study PVA keep as base polymer and chitosan added in various proportion and successfully crosslinked with TEOS. The resulting membrane was characterised by IR spectroscopy, swelling studies, differential scanning calorimetry, X-ray diffraction and contact angle testing, and was finally applied in the pervaporation system using a range of conditions in order to determine the optimum conditions for enhancing the performance of the membrane
Material
Poly vinyl alcohol (PVA)
Tetraethyl ortho silicate(TEOS) - Crosslinking agent
Chitosan
Scheme of Pervaporation Equipment
Membrane preparation
TEOS solution 6 g
1 Wt.% chitosan solution (in 30 wt.%AA)
1 g Conc. HCl catalyst/Stirred 24 hrs.
100 g : 25 g Stirred 24 hrs.
100 g : 37.5 g Stirred 24 hrs.
100 g : 50 g Stirred 24 hrs.
Casting solution
Washed to remove Acetic acid
Casting solutions
Membrane-1
Membrane-2
Membrane-3
Membrane-0
Membrane characterization and Result
■ IR Analysis
■ Contact Angle
■ X-Ray Diffraction studies of membrane
■ DSC Curve
Membrane
Glass transition temperature (Tg) M0
190 M1
188 M2
186 M3
183
Pervaporation studies
Conclusion
■ Effect of feed concentration and Chitosan content on Swelling degree of membranes
On the basis of FTIR spectrum it could be confirmed that,TEOS successfully crosslinked with PVA and Chitosan. From the XRD pattern of membranes, peak corresponding to 2 theta =20 0 crystallinity peak of PVA was decreased with chitosan content showed increased in amorphous region in to the membrane. From the DSC curved of membrane Tg value calculated and was decreased with chitosan addition, suggested that both polymer has a good compatibility. Declined value of contact angle and increased swelling degree of membranes as function of chitosan addition showed the membranes hydrophilicity was increased with increase of chitosan.
From pervaporation data for separation of acetic acid- water mixture (80/20,w/w) by using prepared membranes, it could seen that permeation rate of chitosan blended membranes improved in comparison to the without chitosan membrane, with decreased in the separation factor owing to membrane free volume and hydrophilicity enhancement of membrane supported by the XRD and swelling degree studies.
PVA/TEOS/Chitosan blend membranes prepared in this study showed significant pervaporation performance for separation of water acetic acid.
■ Effect Chitosan addition on pervaporation performance of membrane
Lab of Coating and Joining system