Abstract:

Objective: The research aimed to develop a cellulose nanofibers/filter paper (CNF/FPP) composite microfiltration membrane with a low price,a simple production process and an excellent performance. The effects of basis weight of the composite membranes and CNF additions on the filtration performances and mechanical properties of the composite microfiltration membrane were investigated. This study was expect to provide a theoretical basis for the industrial application of the composite CNF/FPP microfiltration membrane. Method: The mature paper production technology was adopted to prepare the composite microfiltration membranes by combining the filter paper pulp (FPP) and cellulose nanofibers (CNF). The CNF retention rate,pure water flux,GCC retention rate,mechanical properties and micro morphology were tested,respectively. The effects of CNF retention,CNF addition and the quantification of composite membranes on the pure water flux,GCC rejection as well as mechanical properties of the composite microfiltration membranes were further studied. Result: The addition of AlCl₃ was beneficial to the aggregation of CNF,leading it bedded into the composite microfiltration membranes. When the ratio of CNF (g)/AlCl₃ (mmol) was 3:2,the retention rate of CNF reached 100%. With the increase of the amount of CNF and the quantitative value of the composite membrane,the pure water flux of the composite microfiltration membrane was decreased and the retention rate of GCC was increased. Specifically,when the amount of CNF was 20% and the composite membrane was 50 g·m^-2,the composite membranes possessed the highest retention rate (up to 85.94%) and the pure water flux was 1 814 L·m^-2h^-1. In addition,the mechanical properties of the composite microfiltration membrane were obviously improved with the retention of CNF. Especially,the tensile strength of the composite microfiltration membrane was up to 2.619 kN·m^-1,which was twice that of the pure FPP pulp membrane. The micromorphology analysis of the composite microfiltration membrane further showed that CNF could be lapped on the filter paper substrate to reduce the original porosity of the filter paper. Conclusion: AlCl₃ was added to the cellulose nanofibers dispersion so that the cellulose nanofibers can be trapped and embedded into the pulp. With the increase of the quantity of the composite microfiltration membrane as well as the addition of CNFs,the pure water flux of the composite microfiltration membrane decreased,while the corresponding retention of GCC increased. When the added amount of CNFs was 20%,the retention rate was up to 85.94%,and the pure water flux was only 1 814 L·m^-2h^-1. Due to the high strength of CNFs,and the fact that it can form crosslinking in the paper pulp substrate thus reducing the porosity of the membrane,the filtration and mechanical performances of the composite microfiltration membrane were superior to those of pure filter paper.

Key words: cellulose nanofibers (CNF), filter paper pulp(FPP), composite, microfiltration membranes