再生纤维素微孔膜的制备与性能研究
发布时间：2018-10-29 15:57
【摘要】：纤维素是世界上最丰富的天然有机物,具有很多优良特性,如生物可降解性、高亲水性、热化稳定性,由纤维素所制备的再生纤维素膜完全保留了其优良特性。生物可降解性对环境友好,符合可持续发展战略;高亲水性可大大降低膜的污染;热化稳定性可用于条件更为苛刻的环境,如酸碱体系、有机溶剂体系。本论文以棉桨为原料,低温下溶解在9.5wt%NaOH/4.5wt%硫脲水溶液中,通过改变制膜条件来调控再生纤维素(RC)膜的结构和性能,并探讨了干燥方式对膜结构与性能的影响,最后对RC膜进行了耐酸碱性和油水分离应用作了初步研究。首先,通过在铸膜液中加入添加剂、不同凝固浴及溶剂配比条件探究制膜条件对RC膜结构与性能的影响。结果表明,随LiCl含量的增加,RC膜水通量、孔径和结晶度均增加,而对牛血清白蛋白(BSA)截留率减小,LiCl促进孔生成,起致孔作用。RC膜水通量、孔径和结晶度随ZnCl2含量的增加先减小后增加,而BSA截留率一直减小,ZnCl2先抑制后促进孔的形成。以DMAc作凝固浴制备的RC膜,孔径最大,通量最高,NMP凝固浴制备的RC膜,孔径最小,通量最低,但结晶度最高。DMAc水溶液作凝固浴时,随着DMAc含量的增加,水通量增加,BSA截留率降低。不同混合溶剂实验中,得到RC-LU膜的孔径、通量、结晶度和拉伸强度均最小,RC-LTU膜的孔径和通量最大,RC-NU膜结晶度和拉伸强度最大。其次,比较了不同干燥方式对RC膜结构的影响。冷冻干燥方式较好地保留了RC膜的多孔结构,逐级脱水仅保留了少部分孔结构,自然干燥和加热干燥不能保留RC膜的多孔结构。RC膜在干燥过程中结晶度会进行增长,四种干燥方式下的RC膜结晶度大小为:冷冻干燥自然干燥逐级脱水干燥加热干燥。最后,对RC膜进行耐酸碱性测定,其在pH1-14的水溶液中浸泡一周后,水通量、面积变化率和重量变化率仅有微小变化。在对不同pH的含油乳液处理过程中,溶液通量与水通量相比,仅有少量降低,对油的截留率都在98%以上,展现了较高的截留性能。经过水冲洗10min,水通量恢复率在90%左右,说明RC膜具有优良的抗油污染性。
[Abstract]:Cellulose is one of the most abundant natural organic compounds in the world. It has many excellent properties, such as biodegradability, high hydrophilicity and thermal stability. The regenerated cellulose membrane prepared from cellulose completely retains its excellent properties. Biodegradability is environmentally friendly and consistent with sustainable development strategy; high hydrophilicity can greatly reduce membrane fouling; thermal stability can be used in more demanding environments such as acid-base system and organic solvent system. In this paper, cotton oars were used as raw materials and dissolved in aqueous solution of NaOH / 4.5 wt% thiourea at low temperature. The structure and properties of regenerated cellulose (RC) membranes were regulated by changing the conditions of membrane preparation. The effects of drying methods on the structure and properties of the membrane were discussed. Finally, the acid and alkaline resistance of RC membrane and the application of oil and water separation were studied preliminarily. Firstly, the effects of different coagulation bath and solvent ratio on the structure and properties of RC membrane were investigated by adding additives into the casting solution. The results showed that with the increase of LiCl content, the water flux, pore size and crystallinity of RC membrane increased, while the (BSA) rejection of bovine serum albumin (BSA) decreased, and LiCl promoted pore formation, which resulted in pore formation. The water flux of RC membrane increased. The pore size and crystallinity decreased firstly and then increased with the increase of ZnCl2 content, while the rejection rate of BSA decreased. ZnCl2 inhibited the pore formation first and then promoted the formation of pore. RC membrane prepared by DMAc as coagulation bath has the largest pore size and highest flux. The RC membrane prepared by NMP coagulation bath has the smallest pore size and the lowest flux, but its crystallinity is the highest. With the increase of DMAc content, the water flux increases with the increase of DMAc content. The rejection rate of BSA decreased. The pore size, flux, crystallinity and tensile strength of RC-LU membrane were the smallest, the pore size and flux of RC-LTU membrane were the largest, and the crystallinity and tensile strength of RC-NU membrane were the largest. Secondly, the effects of different drying methods on the structure of RC membrane were compared. The porous structure of RC membrane was well preserved by freeze-drying method, and only a few pore structures were retained by step dehydration. The porous structure of RC film could not be preserved by natural drying and heating drying. The crystallinity of RC film would increase during drying. The crystallinity of RC film under four drying methods is as follows: freeze-drying, natural drying, step by step dehydration, drying, heating and drying. Finally, the acid and alkali resistance of RC membrane was determined. After immersion in pH1-14 aqueous solution for one week, the water flux, area change rate and weight change rate were only slightly changed. In the treatment of different pH emulsion containing oil, the flux of solution is only a little lower than that of water flux, and the rejection rate of oil is above 98%, which shows high retention performance. After water washing for 10 min, the recovery rate of water flux is about 90%, which indicates that RC membrane has excellent resistance to oil pollution.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893
[Abstract]:Cellulose is one of the most abundant natural organic compounds in the world. It has many excellent properties, such as biodegradability, high hydrophilicity and thermal stability. The regenerated cellulose membrane prepared from cellulose completely retains its excellent properties. Biodegradability is environmentally friendly and consistent with sustainable development strategy; high hydrophilicity can greatly reduce membrane fouling; thermal stability can be used in more demanding environments such as acid-base system and organic solvent system. In this paper, cotton oars were used as raw materials and dissolved in aqueous solution of NaOH / 4.5 wt% thiourea at low temperature. The structure and properties of regenerated cellulose (RC) membranes were regulated by changing the conditions of membrane preparation. The effects of drying methods on the structure and properties of the membrane were discussed. Finally, the acid and alkaline resistance of RC membrane and the application of oil and water separation were studied preliminarily. Firstly, the effects of different coagulation bath and solvent ratio on the structure and properties of RC membrane were investigated by adding additives into the casting solution. The results showed that with the increase of LiCl content, the water flux, pore size and crystallinity of RC membrane increased, while the (BSA) rejection of bovine serum albumin (BSA) decreased, and LiCl promoted pore formation, which resulted in pore formation. The water flux of RC membrane increased. The pore size and crystallinity decreased firstly and then increased with the increase of ZnCl2 content, while the rejection rate of BSA decreased. ZnCl2 inhibited the pore formation first and then promoted the formation of pore. RC membrane prepared by DMAc as coagulation bath has the largest pore size and highest flux. The RC membrane prepared by NMP coagulation bath has the smallest pore size and the lowest flux, but its crystallinity is the highest. With the increase of DMAc content, the water flux increases with the increase of DMAc content. The rejection rate of BSA decreased. The pore size, flux, crystallinity and tensile strength of RC-LU membrane were the smallest, the pore size and flux of RC-LTU membrane were the largest, and the crystallinity and tensile strength of RC-NU membrane were the largest. Secondly, the effects of different drying methods on the structure of RC membrane were compared. The porous structure of RC membrane was well preserved by freeze-drying method, and only a few pore structures were retained by step dehydration. The porous structure of RC film could not be preserved by natural drying and heating drying. The crystallinity of RC film would increase during drying. The crystallinity of RC film under four drying methods is as follows: freeze-drying, natural drying, step by step dehydration, drying, heating and drying. Finally, the acid and alkali resistance of RC membrane was determined. After immersion in pH1-14 aqueous solution for one week, the water flux, area change rate and weight change rate were only slightly changed. In the treatment of different pH emulsion containing oil, the flux of solution is only a little lower than that of water flux, and the rejection rate of oil is above 98%, which shows high retention performance. After water washing for 10 min, the recovery rate of water flux is about 90%, which indicates that RC membrane has excellent resistance to oil pollution.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893
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