| Konjac glucomannan(short as KGM)is a kind of plant polysaccharide,which extracted from the tuber of konjac,and since its excellent abilities of film-forming and biodegradable,KGM has became a potential pellicular materials.Although China's membrane technology developed rapidly nowadays,we can not deny the short history of our Microfiltration membrane(short as MF)industry.Therefore,China's MF still exist several obvious shortages,like short service life,poor separation and expensive price etc,This article tried to prepare semi-interpenetrating polymer network hydrogels by blend KGM with Peach gum,and tried to obtain MF with excellent mechanical properties,solvent-resistance properties,acid alkali-resistance,thermal stability and micro pore through phase inversion method and freezing induced phase separation method;The single factor experiment and orthogonal optimization was applied to optimize the processing of the composite MF.The change of MF properties,like pore size,porosity etc,has basically been determined;On this basis,respectively applied PI-MF and FI-MF to metal ion filtering,In order to provide reference for the practical application of composite MF.These KGM/peach gum composite materials were made through two different kinds of method,which showed us a new way to exploit the degradable and environment-friendly MF,and promoting the further processing and utilizing of KGM and peach gum.The main results of this research were showed as follows:(1)Study on the processing of the KGM/peach gum composite MF by phase inversion methodKGM/peach gum-based MF are prepared by phase inversion method and combine with sodium sulfate as pore-forming and glycerin as plasticizer etc.Firstly,preparing the casting Solution based on the blending of KGM/peach,and then raise up the temperature that promoted the processing of solvent and non-solvent mass exchange,which transformed the semi-interpenetrating polymer network hydrogels into film.The effect of peach gum ratio,glycerin content,the weight of casting solution and drying temperature on the properties of MF were explored and studied,Results showed that effect of the drying temperature and the weight of casting solution was insignificant,with the remaining three more significant factor that obtained by orthogonal experiment optimization analysis:the influence of peach gum ratio on the tensile strength,porosity and average pore size is outstanding,the sodium sulfate content has significant effects on porosity,and the effect of glycerol content on the elongation at break is remarkable.The tensile strength is between 19 MPa and 30 MPa,the average pore size distributed between 0.5 ?m and 0.9 ?m,and the porosity distributed between 62%and 82%.In conclusion,the best process parameters was determined as follows:the concentration of total polysaccharides is 1.5%,the peach gum doping ratio is 20%,the sodium sulfate content is 0.7g,the weight of casting solution is 70 g,the glycerin concentration is 0.18%,and the drying temperature is 60?.Apply these data that mentioned above,the composite MF;which the tensile strength is 29.17 MPa,the elongation at break is 32.07%,the porosity is 83.4%and the average pore size is 0.52?m,was produced.2.Study on the processing of the KGM/peach gum composite MF by freezing induced phase separation methodKGM/peach gum-based MF is prepared through freezing induced phase separation method,and discussing the compositing,cross-linking and freeze-drying process.The effect of peach gum ratio,sodium carbonate concentration,SDS concentration,glycerol content,the weight of casting solution and pre-freezing temperature on mechanical strength,porosity,pore diameter size were studied respectively.Based on single factor experiment,and apply the orthogonal experimental design to optimize the peach gum ratio,sodium carbonate concentration,SDS concentration and pre-freezing temperature,which shows that:the effect of peach gum ratio on the tensile strength is outstanding;SDS concentration has significant influence on the porosity,average pore diameter;the effect of concentration of sodium carbonate the elongation at break is remarkable.The tensile strength is between 0.5 MPa and 1.7 MPa,the average pore size is distribute from 39?m to 45?m,and the porosity is distribute from 77%to 93%.As a result,we can ultimately concluded that the FI-MF preparation condition,which the concentration of total polysaccharides is 1.5%,peach gum ratio is 40%,the weight of casting solution is 100 g,concentration of sodium carbonate is 0.15%,glycerol concentration is 2%,and pre-freezing time is 54 hours.Apply these data that mentioned above,the composite MF,which the tensile strength is 1.72 MPa,the elongation at break was 16.53%,the porosity is 92.8%,the average pore size of 36.78 ?m,was produced.3.The structure characterization and peculiarity test of these two different kinds of MF(1)In order to infer the compatibility between the blend and the overall structure of the composite MF,the IR analytical method was adopted in the experiment.Significant peak appeared in these absorption peak wavelengths was observed by the stretching vibration characteristic of FI-MF and PI-MF in KGM‘s beta glycosidic bond,which means that both of them remain the main chain structure of KGM;The absorption peak have the trend of moving towards to lower band in O-H stretching vibration,which suggested that compatibility was possessed both of them.(2)Apply the SEM analytical method on the morphology of these two composite,we found out that,both of these two MF have the large dense pore structure.PI-MF's apertures are uniformly distributed,the ostiole of PI-MF is quite neat,and it has high porosity,besides,these porosity are interconnected.Compared with PI-MF,FI-MF has more uneven surface orifice,more bigger pore size and similar porosity(3)In the characteristics experiments of metal ion filter,the experimental preparation of PI-MF,FI-MF,respectively,are filtered to the 500 mg/L of sodium chloride,calcium chloride,copper chloride,potassium chloride,copper chloride,ferric chloride solution,and the results suggest that the interception of FI-MF to metal ion rate generally higher than PI-MF,besides,the highest interception of these two kinds of MF are both occurred in copper chloride solution,among them,the interception of FI-MF of copper chloride solution is at a rate of 49.78%,while PI-MF intercept a rate of 34.82%in the copper chloride solution;The interception on these monovalent ions,like potassium ion,sodium ion,and etc,are lower than these high-price cationic propyl gallate,like calcium ion,copper ion cation solution.In addition,there exist a gap on the interception of metal ion levels of two kinds MF between the expected value and actual value,which might cause by the pore diameter and material liquid velocity and etc.(4)In the chemical stability experiments,MF was respectively soaked in anhydrous ethanol,50%ethanol,methanol,n-butanol and ethyl acetate,petroleum ether,30%hydrogen peroxide and acetone,20%sodium hydroxide,sulfuric acid,8%hydrochloric acid,20%and 8%acetic acid,and result shows that both of these two MF that were able to tolerate ether,ester,ketone,alcohol and other organic solvent,and after soaked for 48 hours,indexes such as porosity,pore diameter size,are more than 90%of these indexes before MF was soaked.Besides,they have a good alkali resistance that can tolerate 20%naoh solution for 48 hours,while both PI-MF and FI-MF has a poor tolerance in acid solution and strong oxidizer.The PI-MF,which soaked in 20%sulfuric acid,20%hydrochloric acid,30%hydrogen peroxide solution after 48 hours,were broken at the MF surface.FI-MF's acid resistance is better than that of PI-MF's,which can tolerate 8%hydrochloric acid solution.(5)In the thermal stability experiments,Both of them can tolerate dry heat disinfection sterilization under 120? and water bath boiling under 100?.The membrane weight,pore diameter and porosity of the MF are basically remain 80%before and after these experiments,which prove that MF has preferable thermal stability and suit for the operation of disinfection and sterilization under high temperature. |
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