Research On The Preparation And Properties Of Basalt Fiber Based Separation Materials

With the aggravation of global energy shortage and environmental pollution,it is urgent to develop a new type of high-performance separation material.Basalt fiber has outstanding mechanical properties,chemical corrosion and radiation resistance,and excellent thermal and sound insulation performance.In addition,its production process is environmentally friendly.MOFs（metal-organic frameworks）have been widely used in the field of adsorption and separation due to their ultra-high specific surface area,rich adjustable pore structure,and active sites.However,their powdery form makes them difficult to be processed and recycled,which limits their application.Therefore,the research on MOFs functionalized basalt fiber materials is of great significance to expand the application spans of basalt fiber and take full advantage of MOFs.At the same time,it also provides a theoretical basis for fiber functionalization and application of MOFs.In this thesis,the preparations of basalt fiber-based separation materials were realized via high-efficiency methods,and the separation and filtration characteristics of the materials were analyzed.The research content includes the following three aspects:1.Zeolitic imidazolate framework-8（ZIF-8）crystals could be controllably coupled on the surface of the fibrous basalt fiber felt via a mild synthetic route,i.e.,a combined method of biomimetic mineralization and layer-by-layer growth.High loading（47.1%）of ZIF-8 on the fiber surface was achieved in a tunable way,accompanied by considerable mass and mechanical retention.The layers of the uniform and densely distributed ZIF-8 on the fibrous substrate were confirmed by morphology and structural characterization.The high-quality loadings of the ZIF-8 ensured the fiber composite with abundant porosity,featuring a considerable specific surface area of 822 m²/g,which made it a promising candidate as an absorbent.The maximum iodine vapor capacity of the target sample was relatively high and up to 3614 mg/g.The mechanism of iodine adsorption was explored in kinetics and thermodynamics aspects.The remarkable chemical and thermal stability of the composite was confirmed even in harsh environments,which was due to the ultra-stability of single components and strong bonding between them.This study is projected to overcome the defect of the MOF powder in the application and further outline a facile method for the construction of MOF-fiber composite to be used in complex environments.2.In this chapter,a facile and efficient method was proposed to realize the preparation of multiple MOFs functionalized woven basalt fiber fabric（W-BF Fabric）.Three typical MOFs,namely ZIF-8,UiO-66,and HKUST-1 were adopted to decorate the surface of W-BF Fabric.Because of the existence of open metal sites in MOFs,which can enhance the positive charge levels of the W-BF Fabric,thus increasing the probability of the fabric capturing negative particles.Therefore,this makes MOFs@W-BF Fabric potentially useful in the field of particulate matter removal.The filtration efficiency of ZIF-8@W-BF Fabric for PM_2.5 and PM₁₀ was doubled compared to that of the original fabric.However,due to the regular arrangement of fibers in the fabric,the porosity was very limited,which increased the pressure drop of the modified basalt fiber fabric.The pressure drop of the original fabric was 118.4 Pa,and the pressure drop of ZIF-8@W-BF Fabric increased the most,from 118.4 Pa to 358 Pa.In order to comprehensively evaluate the filter efficiency and pressure drop,the quality factor of filtration material is used as an index to evaluate its comprehensive filtration performance.The results showed that the quality factor of MOFs@W-BF Fabric was improved compared with that of the original fabric,and the quality factor of ZIF-8@W-BF Fabric was increased from 0.004 Pa^-1 to 0.005 Pa^-1.In addition,the filtration performance of ZIF-8@W-BF Fabric under high temperature or humidity conditions was also investigated,which implied its potential to be used as a filtration material in complex environments.3.Based on the principle of particulate matter filtration,compared to W-BF Fabric in the last chapter,the filtration materials featuring randomly arranged fibers are more conducive for particle filtration.Therefore,Non-Woven-Basalt Fiber Fabric（NW-BF Fabric）with randomly distributed fibers prepared by wet process exhibited a more concentrated distribution of pore structure size,and the filtration efficiency of PM_2.5 and PM₁₀ was doubled(PM_2.5:80.48%,PM₁₀:77.02%)and the pressure drop was only 2 Pa.To further improve its filtration efficiency,the hot-pressing method was further adopted to prepare ZIF-8@NW-BF Fabric.The filtration efficiency of PM_2.5 and PM₁₀ was increased to 93.79%and 94.66%,respectively,the pressure drop of ZIF-8 was only 5 Pa,which showed its advantage of ultra-low pressure drop.The effect of pore structure and charge distribution on filtration efficiency and pressure drop was explained.The quality factor of ZIF-8@NW-BF Fabric was 0.56 Pa^-1,which was 100 times higher than that of ZIF-8@W-BF Fabric.In addition,ZIF-8@NW-BF Fabric has a long-term filtration efficiency of more than 90%within 6 h,with no significant changes in terms of pressure drop.After three cycles,the filtration performance still retained 80%of the filtration efficiency,which indicated its recyclability as a filtration material.Meanwhile,ZIF-8@NW-BF Fabric also exhibited excellent stability in conditions with high temperatures or humidity.