Study On Gaseous Hydrogen Sulfide Adsorption By Modified Sargassum/Enteromorpha Biochar

Hydrogen sulfide?H₂S?widely exists in natural gas,biogas and other clean gases,which not only has a strong odor,but also has a huge harm to the human nervous system.Therefore,in order to use these clean energy better,the removal of H₂S has become an inevitable topic.Activated carbon adsorption technology is considered to be an efficient H₂S removal technology,but its relatively high cost limits the further promotion and application.Compared with terrestrial biomass,seaweed has the advantages of rich yield,low cost and easy access,so seaweed biochar is considered as a potential alternative to activated carbon adsorbent.In this paper,two kinds of seaweeds?sargassum and enteromorpha?were used as raw materials to prepare a variety of seaweed biochars,which were modified by sulfuric acid/hydrogen peroxide?H₂SO₄/H₂O₂?and potassium hydroxide?KOH?respectively.In the fixed bed reaction system,the main factors affecting the removal of gaseous H₂S by these adsorbents,the removal mechanism,and the adsorption kinetics/thermodynamics were systematically studied.The main research contents and results are as follows:Sargassum and enteromorpha were selected for preparation of seaweed biochars by pyrolysis.The seaweed biochars were modified jointly by H₂SO₄ and H₂O₂,and used to remove H₂S from mixture gas.The physical and chemical properties of two kinds of modified seaweed biochars were analyzed by various characterization methods.In the fixed bed reactor system,the effects of some parameters?e.g.,modification method,mixture gas composition,total gas flow rate and adsorption temperature,etc.?on the desulfurization performance of two kinds of modified seaweed biochars were studied,and the desulfurization mechanism was studied.The results show that H₂SO₄/H₂O₂ combining modification can improve the desulfurization performance best,and the optimum adsorption temperature is 100?.For modified sargassum biochars,with the increase of NO,SO₂,CO₂ concentrations and total gas flow rate,the desulfurization performance reduces;with the increase of H₂S inlet concentration,the desulfurization performance can be weakened firstly and then enhanced.For modified enteromorpha biochars,with the increase of H₂S,NO,SO₂,CO₂ concentrations and total gas flow rate,the desulfurization performance can be decreased.Low concentration of H₂O?g?enhances the desulfurization performance of two kinds of modified seaweed biochars,while high concentration of H₂O?g?has inhibition effect.H₂SO₄/H₂O₂ combining modification plays an important role in improving the desulfurization performance of two kinds of seaweed biochars from the aspects of improving the pore structure and increasing the oxygen-containing functional groups?such as COO-?.The desulfurization process of two kinds of modified seaweed biochars follows the pseudo-first-order kinetic model.Two kinds of seaweed biochars?sargassum biochar and enteromorpha biochar?were modified by KOH and used to remove H₂S from mixture gas.The physical and chemical properties of the adsorbents were analyzed by various characterization methods.In the fixed bed reactor system,the effects of a series parameters?such as mass ratio of KOH to seaweed biochar,mixture gas composition,total gas flow rate and adsorption temperature,etc.?on the desulfurization performance of two kinds of modified seaweed biochars were investigated,and the desulfurization mechanism was explored.The results show that KOH modification significantly improves the desulfurization performance of two kinds of seaweed biochars,and the optimum mass ratio is 2.For modified sargassum biochars,with the increase of NO,SO₂,CO₂ concentrations and total gas flow rate,the desulfurization performance can be reduced;the increase of H₂S inlet concentration can firstly reduce and then improve the desulfurization performance.For modified enteromorpha biochars,with the increase of H₂S,NO,CO₂concentrations and total gas flow rate,the desulfurization performance decreases;high concentration of SO₂ decreases the desulfurization performance,and low concentration of SO₂has promotion effect.Low concentration of H₂O?g?can improve the desulfurization performance of two kinds of modified seaweed biochars,while high concentration of H₂O?g?can inhibit it.25?is found to be the optimum adsorption temperature within the studied temperature range.The developed pore structure and the alkaline functional groups?such as-COOH?caused by KOH modification are the key reasons for the improvement of the desulfurization performance.For two kinds of modified seaweed biochars,their desulfurization processes both conform to the pseudo-first-order kinetic model.Spent modified sargassum biochars can recover good desulfuration performance by air purging method.