Preparation Of Mn-based Metal Oxide Aerogel And Its Application In VOCs Adsorption

Aerogel adsorbent is a kind of nano-porous adsorbent material which is composed of a unique three-dimensional network in the air medium.Due to its low density,relatively high specific surface area,high porosity,open pore structure and regulated and diversified types and forms,it is often regarded as a new adsorbent,which has a broad application prospect in environmental treatment,especially in the treatment of organic pollutants.Because the surface of metal oxide aerogel has abundant active sites such as metal center and hydroxyl group,it has strong adsorption ability and selective chemical adsorption ability.Manganese is the second most abundant transition metal on earth,and it is cheap.Combining the two to produce manganese metal oxide aerogel is now widely used to remove organic pollutants as a non-toxic and environmentally friendly material.Using potassium sulfate?K₂SO₄?,potassium persulfate?K₂S₂O₈?and manganese sulfate monohydrate?Mn SO₄·H₂O?as raw materials,a K_2-xMn₈O₁₆aerogel with nanorod structure was prepared by hydrothermal method and freeze-drying.To explore the synthesis mechanism of K_2-xMn₈O₁₆aerogel and the effects of K₂SO₄addition and calcination temperature on the synthesis of K_2-xMn₈O₁₆aerogel,the crystal structure,specific surface area and other properties were characterized by XRD,SEM,BET and other methods.The adsorption-regeneration performance was characterized.Studies have shown that K₂SO₄can adjust the reaction rate and sample morphology.The K_2-xMn₈O₁₆nanorods without K₂SO₄are shorter and narrower in size,with the best crystal form,specific surface area of 75 m²/g,and average pore diameter of 36 nm.Static adsorption experiments show that K_2-xMn₈O₁₆nanorod aerogels have better adsorption performance for acetaldehyde when K₂SO₄is not added,and the removal rate is 40%.With the increase of the amount of K_2-xMn₈O₁₆nanorod aerogels,the saturation adsorption capacity increases within a certain range.K_2-xMn₈O₁₆nanorod aerogel adsorbent can be regenerated under mild conditions and can be recycled for 3times.Using manganese chloride tetrahydrate?MnCl₂·4H₂O?,polyacrylic acid?PAA?,propylene oxide?PO?,formamide?FA?as raw materials,sol-gel method and atmospheric pressure drying were used to prepare Mn₃O₄aerogel.TG,XRD,SEM,BET,FT-IR,static contact angle and other methods were used to characterize the adsorbent,the synthesis mechanism of Mn₃O₄aerogel was studied,and the effects of PO,FA,annealing temperature on the synthesis of Mn₃O₄aerogel,and Its adsorption-regeneration performance was characterized.The results show that when the annealing temperature is 350?and the volume ratio of PAA,PO and FA is 3:5:1,the gel time is 85min.The obtained hydrophilic aerogel has a uniform tetragonal crystal nano three-dimensional network skeleton structure,the acetaldehyde removal rate was 54%,and as the amount of aerogel added increased,the saturated adsorption capacity increased within a certain range.Mn₃O₄aerogel can be regenerated under mild conditions and can be recycled 4 times.Using manganese chloride tetrahydrate?MnCl₂·4H₂O?,magnesium chloride hexahydrate?Mg Cl₂·6H₂O?,polyacrylic acid?PAA?,propylene oxide?PO?,formamide?FA?as raw materials,using sol-gel method and constant Press drying to prepare Mg Mn₂O₄aerogel adsorbent.The adsorbent was characterized by TG,XRD,SEM,EDS,BET,XPS and other means.The effects of PAA,Mg²⁺ion concentration and annealing temperature on the synthesis of Mg Mn₂O₄aerogel were studied,and their adsorption-regeneration properties were characterized.The results show that when the molar ratio of Mn:Mg is 2:1,the annealing temperature is 500?,and the volume ratio of PAA,PO and FA is 5:7:1,the aerogel obtained has a uniform tetragonal crystal nano three-dimensional network skeleton structure.The adsorption-regeneration experiment shows that when the temperature is 40?and the air flow rate is 100ml/min,Mg Mn₂O₄aerogel has better adsorption performance for acetaldehyde,and the saturation adsorption capacity is 0.195 mmol/g.The Mg Mn₂O₄aerogel adsorbent exhibits good regeneration performance.After the cyclic adsorption-regeneration experiment,the saturation adsorption capacity changes little and can be recycled 14 times.