Preparation And Properties Of Recyclable Natural Polymer Adsorbent

To improve the recyclability and processability of powdery adsorbents,integrating them on microspheres,membranes or gel substrates is a common strategy.At present,the support of powder adsorbent mainly consists of inorganic ceramics and petroleum-based polymers.At the same time,more and more researchers shift their focus to renewable materials.Natural polymers,such as cellulose,sodium alginate and chitosan,are green and renewable polysaccharide materials,and are also considered as excellent matrixs powder sorbents.In this paper,based on natural macromolecular polysaccharide atural clay and powder absorbent material（attapulgite）and composite metal organic framework materials,design and preparation of the easily recycled and microspheres and gel adsorbent adsorption performance is good, reveals the powder and the mechanism of interaction between polymer carrier,the main work includes:（1）Attapulgite（ATP）was introduced into nanocellulose aerogel through group bonding strategy and used for heavy metal ions removal.（2）The metal-organic framework MIL-121 was compounded into sodium alginate microspheres by phase separation process,and the prepared composite material could effectively remove heavy metal ions in wastewater.（3）In situ growth strategy was used to load aminoated metal-organic framework material ZIF-8-NH₂ into bacterial cellulose（BC）aerogel,and the prepared composite aerogel showed excellent gas adsorption capacity.Specific research work carried out is as follows:（1）ATP@nanocellulose composite aerogel was prepared by freeze-drying method. Carboxylated nanocellulose as the substrate can support and disperse ATP powder efficiently.At the same time,due to the hydrogen bonding between the hydroxyl group on the surface of ATP and the group on the surface of cellulose,ATP has a strong interface interaction with cellulose,and the loading capacity of ATP is up to 80 wt%.In addition,the introduction of Ca²⁺can further enhance the mechanical properties of the composite aerogel.The results of heavy metal ion adsorption experiments showed that the composite aerogel had a high adsorption capacity of Cu²⁺ions,and the adsorption process was in good agreement with Langmuir model（R²>0.99）.The maximum adsorption capacity was 116.5 mg/g,and the composite aerogel was easy to recycle and regenerate.ATP@cellulose composite aerogel has good adsorption performance mainly because of good dispersion of ATP and abundant functional groups on the surface of aerogel.The composite aerogel has excellent mechanical properties,biodegradable,flame retardant and non-toxic,and has a good application potential in water purification.（2）In order to optimize the desorption method of the previous experiment,a solvent-free thermal desorption strategy was proposed in this experiment.By loading mil-121（aluminum-based MOF）crystals onto alginate substrate,composite microspheres were formed under Ca²⁺crosslinking.The adsorption experiments of Cu²⁺and Cd²⁺on the composite microspheres were investigated.When the loading capacity of MIL-121 was 50 wt%,the adsorption capacity of Cu²⁺and Cd²⁺was 204.5 mg/g and 88.7 mg/g,respectively.MIL-121@Sodium alginate composite microspheres can be efficiently regenerated by hot water.This desorption is attributed to the fact that MIL-121 is rich in carboxyl groups and can release a large number of protons（H⁺）at elevated temperatures.Compared with traditional strong acid desorption,this solvent-free thermal desorption strategy has better potential in adsorbent regeneration and practical wastewater treatment.（3）In order to further improve the interfacial affinity between MOFs and natural polymer groups,ZIF-8-NH₂ crystals were uniformly grown on bacterial cellulose fibers by in-situ growth method,and BC@ZIF-8-NH₂ aerogel was prepared.The binding effect between the metal（Zn）ions of ZIFs crystal and the surface groups of bacterial cellulose makes the composite aerogel have high interfacial affinity and compatibility.When the ZIF content was34.8%,BC@ZIF-8-NH₂ aerogel had higher specific surface area（455 m²/g）and higher CO₂adsorption capacity（1.63 mmol/g（25 ^oC,1 bar））.In addition,the selectivity of composite aerogel to CO₂/N₂ was 22.This study provides a new method for the synthesis of ZIF/cellulose composite aerogel for gas adsorption.