稀碱-球磨协同制备菠萝皮渣纤维素纳米纤丝及其结构表征

Preparation and characterization of pineapple peel cellulose nanofibrils by dilute alkali-ball milling synergistic method

以菠萝皮渣为原料,不同质量分数(0%~5%)NaOH溶液为湿磨介质,通过机械球磨法制备菠萝皮渣纤维素纳米纤丝(pineapple peel cellulose nanofibrils,PCNF),利用傅里叶变换红外光谱(Fourier transform infrared spectroscopy,FTIR)、X射线衍射(X-ray diffraction,XRD)、X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)、原子力显微镜(atomic force microscope,AFM)、热重分析仪和流变仪等对PCNF进行结构表征。结果表明,随着NaOH溶液浓度的增加,菠萝皮渣中的非纤维组分(木质素和半纤维素)和纤维素中的无定形区域逐渐被除去,PCNF得率降低,但结晶度和纤维素纯度逐渐增加。相比于单一球磨处理样品(PCNF-0%),稀碱-球磨处理未改变纤维素的晶体结构,但促进了原料解纤和纳米化,改善了PCNF形貌和网络结构,导致PCNF的黏度和模量均有所增加,表现出剪切变稀和弹性凝胶行为。当前研究通过不同NaOH溶液质量分数有效调控球磨制备的PCNF结构,为果蔬加工余渣的直接纳米化提供简易途径。

Using pineapple peel as raw material and sodium hydroxide(NaOH)solution with different mass fractions(0%-5%)as wet grinding medium,pineapple peel cellulose nanofibrils(PCNF)were prepared by mechanical ball milling.The obtained PCNF was characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),atomic force microscope(AFM),thermal gravimeter,and rheometer.Results showed that with the increase of NaOH solution concentration,the non-fibrous components(lignin and hemicellulose)in pineapple peel and the amorphous regions in cellulose were gradually removed,the yield of PCNF decreased,but the crystallinity and cellulose purity of PCNF increased gradually.Compared with the single ball-milled sample(PCNF-0%),the dilute alkali-ball-milling treatment did not change the crystal structure of cellulose but promoted the defibrillation and nanocrystallization process.The morphology and network structure of PCNF were also improved which resulted in the increase of viscosity and moduli,exhibiting a typical shear thinning and elastic gel behavior.The current study proved that the structure of PCNF could be effectively controlled by ball milling with different NaOH solution concentrations,which provided an easy approach for the direct nanocrystallization of fruit and vegetable processing residues.