Preparation And Application Of The Straw Fiber Composite PVFM

Traditional materials for sewage treatment are non-degradable and easy to be blocked.On the other hand,traditional materials have low volume load and poor sanitary conditions.As a kind of green material,natural fiber composite becomes one of the main promising sewage treatment materials in the future because of its good performance advantages.In this paper,the straw fiber composite PVFM was prepared by chemical cross-linking,mechanical blowing and chemical foaming methods,using polyvinyl alcohol formaldehyde as the framework structure and self-made cellulose as the modification agent.And the biological treatment of domestic sewage was studied by using the composite PVFM.Firstly,the experimental conditions for extracting cellulose from cornstalk were selected and optimized.The intermediate product which called crude cellulose,was obtainded from cornstalk treated by sodium hydroxide.While the intermediate product which called cellulose,was obtainded from cornstalk treated by sodium hydroxide-acetic acid-sodium chlorite.With the content of cellulose as the index,the orthogonal experiments were used to optimize the experimental conditions,and then the optimum experimental conditions for extracting crude cellulose and cellulose were determined respectively.The results showed that the average yield of crude cellulose was 45.98 % and the average purity reached as high as 70.69%;while the average yield of cellulose was32.49 % and the average purity reached as high as 81.45%.FT-IR detection showed that both lignin and hemi-cellulose were removed effectively during the extraction of crude cellulose and cellulose.The emphasis was put on the optimum experimental conditions for the preparation of straw fiber composite PVFM.The crude cellulose-polyvinyl formal CC-PVFM and cellulose-polyvinyl formal C-PVFM were prepared by using crude cellulose and cellulose respectively.In the experiments,the porosity,specific gravity,water absorption ratio and cross-linking degree were detected as indicators to determine the optimum experimental conditions of CC-PVFM and C-PVFM by orthogonal experiments.The tensile strength and specific surface area of the material were measured.The synthesis and foaming of the composites were analyzed by FT-IR and SEM.The experiments used PVA and crude cellulose as the raw materials,formaldehyde as the cross-linking agent,and sodium bicarbonate as the foaming agent to optimize the optimum experimental conditions for CC-PVFM.The results showed that the optimum experimental conditions of CC-PVFM were as follows: PVA mass concentration 10 %,crude cellulose dosage 0.5 g,concentrated sulfuric acid dosage 4 mL,formaldehyde dosage 5 mL,SDS dosage 0.3 g,sodium bicarbonate dosage 0.63 g,reaction temperature40 ?,the dripping time of sulfuric acid 6 minutes,the dripping time of formaldehyde 4minutes and curing time at 60 ? for 8 hours.Equally,the optimum experimental conditions for the preparation of C-PVFM were obtained by using PVA and cellulose as raw materials under similar conditions.Under the optimum experimental conditions,the basic properties and foaming situations of the two materials including porosity,specific gravity,water absorption and cross-linking degree were almost the same.But the tensile strength and specific surface area of CC-PVFM were better than those of C-PVFM,which showed that the performance of CC-PVFM was relatively good.The sewage treatment experiments showed that the two composites had achieved good sewage treatment effects,but the sewage treatment effects of the two composites were not significantly different.After the system was stable,the average removal rate of COD and ammonia nitrogen removal rate of CC-PVFM reached 92.84 % and 96.66 % respectively and the average removal rate of COD and ammonia nitrogen of C-PVFM reached 93.26 %and 96.77 % respectively.The COD of effluent was both less than 50 mg/L,and the ammonia nitrogen of effluent was both less than 5 mg/L,which reached the primary national standard request in GB18919-2002.In summary,the preparation of CC-PVFM was simpler and the performance of CC-PVFM was better than C-PVFM.There were no obvious differences between CC-PVFM and C-PVFM in the sewage treatment effects.Therefore,the composite CC-PVFM was more suitable for process production.