Preparation Of Cellulose-based Composite Beads And Its Application On Adsorption And Degradation Of Methylene Blue

With the rapid development of modern industry and economy,non-renewable biochemical petroleum resources are increasingly scarce,carbon emissions are increasing year by year,and environmental pollution is becoming more and more serious,especially dye wastewater from textile,leather,paper and other industries has brought serious harm to humans.The development of natural polymer renewable materials and the application of wastewater treatment have received extensive attention.Cellulose is one of the most abundant natural renewable resources.As a multifunctional material,cellulose beads can be used in dye wastewater treatment and other fields.However,the performance of pure cellulose beads is relatively single,and the mechanical strength is low.The adsorption performance is not significant,and it is difficult to recycle after use,which hinders its further development.In order to solve the above problems of cellulose beads,microcrystalline cellulose（MCC）was used as the substrate,and the cellulose beads were modified by sepiolite（SEP）,sodium alginate（SA）and magnetic Fe₃O₄nanoparticles.The functional composite beads with porosity and magnetic response were prepared,and the adsorption and degradation of methylene blue dye（MB）were investigated.The results are as follows:First,double network composite beads（MCC/SA/SEP）were synthesized,in which MCC and SA worked as the network frameworks,and SEP was a functional component.The components were cross-linked by interaction forces such as hydrogen bonds;The SEM graphics showed that the beads present a three-dimensional network porous structure;In addition,the addition of SEP greatly improved the thermal stability and specific surface area of the beads,providing more adsorption sites for MCC/SA/SEP beads,and increased the adsorption capacity.Due to the synergistic effect of the double network structure composed of MCC and SA and the high saturation adsorption performance of SEP,the adsorption effect of porous beads were remarkable.The adsorption process of MCC/SA/SEP followed the pseudo-second-order kinetic model and Langmuir isotherm,with the maximum adsorption capacity of 333.3 mg·g^-1for MB.After five consecutive adsorption-desorption cycles,the adsorption capacity of MB can still maintain 85.4%of the initial adsorption capacity,indicating that the MCC/SA/SEP beads had stable,efficient and renewable adsorption characteristics,and had potential application prospects in dye adsorption and wastewater treatment.In order to further solve the problem of dye wastewater pollution,multi-functional and recyclable magnetic cellulose/sepiolite（Fe₃O₄/MCC/SEP）composite beads were constructed with MCC as the framework,and magnetic nanoparticles Fe₃O₄and SEP with high adsorption properties were introduced.A series of characterizations show that Fe₃O₄/MCC/SEP beads had excellent hollow porous structure and superparamagnetism.The synergistic effect of SEP and nano-Fe₃O₄endowed it with versatility such as adsorption,degradation,easy separation and recycling.The adsorption process of Fe₃O₄/MCC/SEP magnetic beads followed the pseudo-second-order kinetic model and Langmuir isotherm,and belonged to the single-molecular layer adsorption.Degradation experiments showed that the removal of MB by Fe₃O₄/MCC/SEP was the result of the synergistic effect of adsorption and heterogeneous Fenton catalysis.When temperature of298 K,p H=3,the addition amount of beads was 0.02 g,and the addition amount of H₂O₂was 5 m L,the removal rate of MB was as high as 99%within 240 min.After five times of repeated use,the removal rate of MB by the beads was still above 83%,indicating that Fe₃O₄/MCC/SEP magnetic composite beads could be used as an environmentally friendly and renewable biomass-based catalyst for the degradation of dye wastewater.