Preparation Of Silver Loaded Polyvinyl Alcohol Sponge And Its Catalytic Performance

Polyvinyl alcohol（PVA）sponge is a kind of biodegradable polymer material in the natural environment.The PVA molecular chain has several hydroxyl groups,and the macroporous structure of PVA sponge provides efficient water absorption.Therefore,it is widely used in cleaning and cosmetic materials,functional medical materials,filtration and adsorption materials,buffer and suction packaging materials and biological carrier materials and other fields.Furthermore,discarded PVA sponges may decay totally organically,posing no pollution risk to the environment.PVA silver sponge was made by mechanical foaming using PVA,formaldehyde,and sulfuric acid as raw materials in this article,and its shape,composition,and structure were described,as well as the performance of catalytic reduction of 4-NP using UV-vis spectroscopy.The main work is as follows:（1）Silver loaded polyvinyl alcohol（Ag/PVA）sponges were prepared by one-pot method using water as solvent,polyvinyl alcohol as carrier material.The morphology,constituent and structure of Ag/PVA-1 and Ag/PVA-2 sponges were characterized by FE-SEM,FTIR,Raman,XRD,XPS,TG and microcomputer-controlled electronic universal testing machine.respectively.Ultraviolet-visible spectroscopy was used to test the catalytic performances of Ag/PVA sponges in reduction of 4-NP.The results show that the Ag/PVA sponge prepared by one-pot method has good mechanical properties and a porous structure that effectively prevents AgNPs agglomeration,uniformly distributes silver nanoparticles,and has good catalytic activity in 4-NP reduction.When the concentration of 4-NP is 0.2 mmol/L,the Ag/PVA-1 sponge with 1.9 wt%silver loading completes the catalytic process within 38 min,and the Ag/PVA-2 sponge with 2.2 wt%silver loading completes the catalytic process within 14 min.The apparent reaction rates were 0.0749 min^-1 and 0.2489 min^-1,respectively,and the catalytic efficiencies were above98%.In other words,PVA sponge can be used as an excellent carrier material for AgNPs,and one-pot mechanical foaming method has the characteristics of simple preparation method and high catalytic efficiency.（2）In order to increase the AgNPs loading of PVA sponges and improve the catalytic efficiency,Ag/HNT/PVA sponge was prepared by adding halloysite nanotubes（HNTs）.The morphology and composition of Ag/HNT/PVA were characterized by FE-SEM,FTIR,Raman,XRD,XPS,TG and microcomputer-controlled electronic universal testing machine.The adsorption and catalytic properties of Ag/HNT/PVA for 4-NP were tested by BET and UV-vis spectroscopy.The results show that the Ag/HNT/PVA-3 AgNPs loading is about 3.3 wt%,which is higher than Ag/PVA-1 AgNPs loading is 1.9 wt%,because the hollow tubular structure of HNTs greatly improves the specific surface area and the loading capacity of AgNPs.The specific surface area of Ag/HNT/PVA is about 1.62 m²/g.When HNTs dosage is 5 wt%,Ag/HNT/PVA-3 catalytic rate is the highest,and the apparent rate constant is 0.297 min^-1.After 5 cycles of catalysis,the catalytic efficiency of Ag/HNT/PVA sponge remains above 98%.The cyclic compression test shows that the Ag/HNT/PVA sponge has good mechanical properties and can be used in catalytic applications for a long time.In other words,the addition of HNTs can improve the loading capacity of sponge to AgNPs,making the catalytic reaction more efficient.（3）In order to further increase the AgNPs load of PVA sponges and improve the catalytic efficiency,mannich reaction was added to modify alkali lignin（AL）to prepare lignin amino-polyalcohol（ALAP）rich in hydroxyl groups.FTIR and XPS were used to analyze the ALAP.The results showed that ALAP was successfully prepared by Mannich reaction.The preparation,morphology,composition,mechanical properties and catalytic4-NP performance of ALAP/Ag/PVA were characterized by FE-SEM,FTIR,XRD,XPS,TG,UV-vis and microcomputer-controlled electronic universal testing machine,respectively.The results showed that the silver loading capacity of ALAP/Ag/PVA-6 was about 10.9 wt%due to the rich hydroxyl groups in lignin amine polyols,which greatly improved the loading capacity of AgNPs.ALAP/Ag/PVA-6 has the highest catalytic rate at5 wt%ALAP,and the apparent rate constant is 0.608 min^-1.After 5 cycles of catalysis,the catalytic efficiency of ALAP/Ag/PVA remains above 90%.During the cyclic compression test,ALAP/Ag/PVA sponge has almost no mechanical property loss during the compression process,and the prepared sponge has good resilience.This indicates that the prepared ALAP/Ag/PVA sponge has good mechanical properties and can provide support for catalytic reuse.