Research On Adsorption And Catalysis Properties Of Activated Carbon/bio-char Based On Nickel Recovery From Electroplating Wastewater

Reasonable treatment of waste adsorbent and nickel on it is key research direction for application of adsorption technology in electroplating wastewater treatment.This paper proposed a process of nickel recovery as catalyst for tar reforming by adsorption on activated carbon/bio-char.Based on research of activated carbon,the adsorption properties of bio-char,activation and catalysis properties of nickel adsorbed on bio-char were studied successively.To obtain the best adsorption conditions and modification methods,activated carbon?AC?was used to adsorb simulated nickel palting wastewater under different conditions and was modified by different methods.Before and after modification,AC was analyzed by FT-IR,etc.The results showed that Ni???was effectively adsorbed by AC in the form of Ni?OH?₂under pH value of 9 or above,and the removal was as high as 97%with a nickel load of46.8mg/g.There were MnO₂ and more carboxyl,etc,acidic oxygen-containing functional group appeared on AC after modified by KMnO₄,which enhanced the chemisorption of Ni???,and enhancement was higher with the concentration of KMnO₄.The removal of Ni???by AC modified by 0.5 mol/L KMnO₄ was over 93%with a nickel load of 51.60mg/g.Two kinds of used adsorbents with optimal adsorption effects?When the pH value of the solution is 9&AC modified by 0.5mol/L KMnO₄?were selected to be activated to prepare Ni/AC-AA and Ni/AC-MA catalysts.Ni/AC-Im catalyst prepared by impregnation method was used as control,and Ni/AC catalysts were subjected to catalytic steam reforming experiments in which toluene was used as the model compounds of bio-tar.The performance of catalysts was evaluated by MS and GC.The catalysts were characterized by XRD and TEM,etc.The catalytic properties and mechanism of nickel adsorbed on AC were studied.The results showed that the nickel adsorbed on the surface of AC played an important catalytic role in tar reforming reaction.The conversion of toluene catalyzed by Ni/AC-AA and Ni/AC-MA reached 8 times and 5 times of AC,respectively,while H₂ yield increased to131.64mL and 100.00mL,respectively.But the agglomeration of Ni?OH?₂ on AC led to poor dispersibility of nickel particles on Ni/AC-AA,and the size of metal particles on Ni/AC-MA was large and was easy to agglomerate at high temperature due to the loading of MnO,so the activity of Ni/AC-AA and Ni/AC-MA was decreased during reaction,which also led to their lower catalytic activity than that of Ni/AC-Im prepared by impregnation method.The sawdust,rice husk,straw,cotton stalk and corn stalk were selected for pyrolysis to product bio-char.Referring to the research results of AC,modification and adsorption experiments were carried out.The adsorbents with the best adsorption effect were activated and prepared as Ni/char catalysts and used to catalyze steam reforming of toluene.The results showed that the richer carboxyl,alcoholic hydroxy,carbonyl,etc,acidic oxygen-containing functional groups and the relatively more mesoporous structure on char of straw promoted its adsorption performance,and its removal rates of Ni???at pH of 6 and 9 were higher than that of other bio-chars,which were as high as 90%and 100%,their nickel load was42.78mg/g and 47.35mg/g,respectively.The corresponding Ni/straw-Ad and Ni/straw-AA catalysts prepared by the activation of used adsorbent showed better catalytic effects than char of straw.The conversion of Ni/straw-Ad and Ni/straw-AA for toluene reforming were9.5 times and 5.8 times that of char of straw,respectively,and were superior to Ni/AC-AA,while H₂ yield increased to varying degrees;The adsorption capacity of Ni???by the bio-char modified by KMnO₄ was improved,but it was not as significant as the modified AC.For the char of corn stalk with the best modification,the adsorption removal rate of Ni???was increased by 22%compared with that before modification.The toluene conversion catalyzed by Ni/cornstalk-MA which was prepared by activating of nickel adsorbed on modified char of corn stalk was 5 times and 4 times that of char of corn stalk and Ni/AC-MA,respectively.But its H₂ yield?4.34mL?was lower than that of Ni/AC-MA catalyst.