Study On The Preparation Of Porous Carbon Adsorbent From Pepper Straw And Its Mercury Removal Performance From Flue Gas

Porous carbon is widely used in adsorption,catalysis and electrode materials due to its rich pore structure,high specific surface area and excellent adsorption property.Pepper straw can be seen everywhere in rural China,and it has the characteristics of high carbon and low ash.Converting pepper straw into porous carbon,which turns the waste into treasure,is anovel method for environmental protection.Therefore,in this paper,We propose a porous carbon adsorbent with high specific surface area and high adsorption capacity that was prepared by one-step activation method using cheap pepper straw as raw material.The relationship between the structure and adsorption performance of porous carbon under different preparation conditions was systematically analyzed.The effect of conditions on the materials’mercury removal performance was discussed,and the mercury removal mechanism was revealed,the main research contents and results are as follows:（1）Porous carbon was prepared by using pepper straw as raw material,KOH,K₂C₂O₄ and K₂CO₃ as activators and ferric nitrate as activation assistants,respectively.A series of porous carbons were prepared by adjusting the parameters such as temperature,time and assistant concentration were optimized.The research results showed that when use potassium oxalate as the activator and 0.4 mol·L^-1iron nitrate as the activation assistants,the activation temperature was 850°C.and the activation time was 2 h,the obtained porous carbon(A_0.075-Fe_0.4-T850-t2)had the best mercury removal activity,and the mercury removal efficiency could remain above97.6%within 2 h under the simulated flue gas atmosphere at 150°C.This mainly attributed to its high specific surface area(428.72 m2·g^-1)and the presence of Fe₂O₃,the active component for mercury removal,and the adsorbent had excellent magnetic function,which can realize the reuse of the adsorbent.（2）The reaction temperature of mercury removal,space velocity and flue gas composition have certain effects on the mercury removal activity of the adsorbent.When the temperature increased from 60°C to 150°C,the mercury removal efficiency of the adsorbent showed an increasing trend.When the space velocity increased,the contact time between the adsorbent and Hg⁰ were shortened,The O₂ and SO₂ introduced into the flue gas can promote the mercury removal performance of the adsorbent,while the presence of NO and H₂O were not conducive to the removal of Hg⁰.Under the simulated flue gas atmosphere of O₂,SO₂,NO and H₂O,the mercury removal activity could remain at 100%within 2 h.The surface oxygen species（lattice oxygen and chemisorbed oxygen）of the adsorbent are the main active species for the removal of Hg⁰_（g）,which is then removed by oxidation of Hg into HgO.