Preparation Of Hemp Stalk-based Active Carbon Heterogeneous Fenton Catalyst And Its Application On The Deep Treatment Of Pulping Wastewater

Fenton oxidation technology has the advantages of strong oxidation,high reaction efficiency,low cost and no secondary pollution.It has good development prospects.In this paper,activated carbon was prepared from hemp stalk by phosphoric acid activation method.The effects of various factors on the adsorption performance and pore structure of activated carbon were studied.Activated carbon with high specific surface area and good adsorption performance was prepared.Then,the activated carbon was used as the carrier of heterogeneous Fenton catalyst to support nano-zero-valent iron by solvothermal-carbothermal reduction method,and the key factors in the preparation process were also studied.Finally,the treatment process and effect of the catalysts for papermaking wastewater were discussed.The effects of various factors on the properties of activated carbon prepared from hemp stalk and phosphoric acid as activator were studied.The results show that phosphoric acid concentration,phosphoric acid activation time,carbonization temperature and carbonization time have great influence on the pore structure of activated carbon.With the increase of phosphoric acid concentration and phosphoric acid activation time,the pore size of hemp stalk was gradually opened and enlarged.The activated carbon prepared by 3 mol/L phosphoric acid activation of hemp stalk for 4 hours had good microporous structure.With the increase of carbonization temperature and carbonization time,the wood fibers in hemp stalk were pyrolyzed step by step,and the pore number and structure of activated carbon were increased.However,the pore structure of activated carbon would collapse if the temperature was too high and the carbonization time was too long.The results showed that hemp stalk activated by phosphoric acid could be calcined for 1 hour at 400?,and hemp stalk-based activated carbon with excellent microporous structure could be obtained.The preparation of nano-Fe⁰ heterogeneous Fenton catalyst supported on hemp stalk-based activated carbon by solvothermal-carbothermal reduction was studied.The results show that the magnetic properties and catalytic activity of the catalysts increase with the increase of the reaction temperature of the thermal solvent;controlling the mixing ratio of ethanol and toluene can better support the metal iron on the activated carbon without being oxidized;the appropriate iron-carbon ratio can make the catalysts have sufficient active sites to participate in the catalytic reaction;after calcination at different temperatures,the metal iron can be combined in different ways.Things or elementary forms exist.Therefore,the catalysts prepared by choosing the reaction temperature of thermal solvent at 200 C,the ratio of ethanol to toluene at 4:1,the ratio of iron to carbon at 2:1 and the calcination temperature at 800?have good catalytic activity.The process of treating wastewater with Fe⁰/hemp stalk-based activated carbon catalyst was studied.The results showed that the catalyst had good catalytic effect under acidic conditions.The catalytic activity of the catalyst increased firstly and then stabilized with the increase of the amount of hydrogen peroxide,catalyst and reaction time.The removal rates of COD_Cr and TOC in wastewater could reach 86.64%and 86.27%under the optimum conditions.The COD_Cr removal efficiency of Fe⁰/hemp stalk-based activated carbon catalyst was still 35.36%after six consecutive uses.GC-MS analysis showed that Fe⁰/hemp stalk-based activated carbon catalyst could degrade most of the organic matter in wastewater,effectively reduce the pollution load of the treated pulping wastewater and meet the national discharge standards.