Efficient Silver Removal From Resin-based Dopamine And Catalytic Properties Of P-nitrophenol Catalyzed By Nano-silver

Silver,as a kind of active precious metal,has limited reserves and wide uses on the earth.Silver-containing wastewater from electronics industry,photography and other industries is harmful to the ecological environment.P-aminophenol is an active chemical intermediate of many organic substances and has been widely used in many industries,such as medicine,rubber,dyestuff and so on.P-aminophenol is synthesized by catalytic reduction in industry.Although the common noble metal catalysts are green and efficient,they are expensive and are not conducive to widespread use.In this paper,based on mussel inspiration,resin-based dopamine nano-silver composite was prepared by adsorbing and recovering silver ions from waste liquor using the adhesiveness and reducibility of dopamine and the targeting mass transfer characteristics of D001 resin,and the catalytic reduction of p-nitrophenol to p-aminophenol was studied.Polydopamine?PDA?coatings were coated on the surface of macroporous cation exchange resin as matrix to improve the selective adsorption of silver ions by resin matrix.It was proved by TEM,SEM,EDS and XRD that the catalyst existed in sphere and silver only existed in zero valent silver.The reaction mechanism of adsorbing silver ions on resin-based polydopamine coatings was studied by FTIR and XPS.The strong acid condition of polydopamine was not conducive to the carrier adsorbing silver ions.The optimum pH of the solution was between 4 and 6.When the concentration of competitive ions Na⁺,Ca²⁺,Mg²⁺was 64 times of the solubility of Ag⁺.The adsorption efficiency of silver ion on the carrier is still above 75%.The adsorption reaction of silver ion is endothermic.Increasing temperature is conducive to increasing the adsorption capacity of resin-based polydopamine coating for silver ion.The saturated adsorption capacity of silver ion at room temperature is 151 mg/g.The silver nanoparticles in composite resin-based dopamine silver nanoparticles have small particle size,large specific surface area and abundant active sites.From the catalytic reduction process spectra of UV-vis nitrophenol,it can be seen that there are two maximum absorption peaks at 400 and 317 nm from the addition of sodium borohydride to the end of the reaction.There are no other peaks.p-nitrophenol is completely converted to p-aminophenol,and the catalytic reduction of p-nitrophenol reaches within 25 minutes.When the reaction is saturated,the efficiency of p-nitrophenol is over 93%.Increasing the temperature is not conducive to the catalytic reduction of 4-nitrophenol by silver nanoparticles.After recovery and elution,the composite material can be recovered and reused for five times with an efficiency of more than 90%.The catalyst has good stability and has a certain catalytic reduction ability for other nitrobenzene organic compounds.