Effect of citric acid modification on the spherical activated carbon's ammonia adsorption performance
The pitch-based spherical activated carbon was used as support to load different amounts of citric acid into its pores by equivalent-volume impregnation method.The effect of citric acid modification on the activated carbon's ammonia adsorption was evaluated by a fixed bed dynamic adsorption device.The physicochemical properties of activated carbon before and after modification were characterized by SEM,XRD,FTIR,nitrogen adsorption and desorption.The results showed that the modified activated carbon had the best ammonia adsorption performance when the load of citric acid was 60%.The ammonia protection time was 194min,and the ammonia adsorption capacity was 42.8mg/mL(66.8mg/g),which was 24 times that of unmodified activated carbon.The total specific surface area,pore volume and pH of the adsorbent decreased with the increase of citric acid loading,and the correlation coefficients R2 between the specific surface area and pore volume of the adsorbent,and citric acid loading were 0.9944 and 0.9842,respectively.As the loading capacity increased,the utilization rate of citric acid decreased.Ammonia reacted with citric acid to produce ammonium citrate.The products were mainly deposited in micropores,which were crucial for ammonia adsorption.
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