Study On Biochar Based Materials From Agricultural Waste And Its Adsorption Of H₂S

With the rapid development of agricultural and rural technology in China,the output of crops is also increasing year by year,followed by a large number of agricultural wastes.Most of the agricultural wastes have high cellulose content and rich functional groups,so the preparation of high-performance adsorption carbon materials from agricultural wastes has become a hot research direction in the world.The biochar base formed by pyrolysis and carbonization of agricultural waste biomass has rich pore structure,strong adsorption capacity and loading capacity.It is an excellent catalyst carrier material with adsorption performance.In this paper,four kinds of common agricultural wastes with regional representation in rural areas of China were selected as biochar based raw materials,and biochar based materials with specific adsorption for H₂S were prepared by different loading and modified composite processes,which were applied to remove H₂S from ambient air in living and production scenes to achieve the research effect of"treating waste with waste".The main contents and conclusions of this paper are as follows:（1）Peanut shell（PS）,corn straw（CS）,rice straw（RS）and shaddock peel（SP）,which are representative of rural areas in China,were used The results showed that the yield of biochar decreased with the increase of pyrolysis temperature and pyrolysis time,and the highest carbon yield of grapefruit peel biochar reached 41.37%after pyrolysis at 300℃for 60 min.The overall biochar based yield of four kinds of agricultural waste biomass ranged from 29.82%to 41.37%.The results showed that the corn straw biochar prepared by heating rate of 10℃/min,pyrolysis temperature of 600℃and pyrolysis time of 120 min had the best hydrogen sulfide adsorption performance,the breakthrough time was about 12 min,and the sulfur adsorption capacity reached 5.628mg/g.Through the FTIR characterization of each biochar base,it was found that the surface functional groups of common agricultural waste biochar based materials were relatively close,and grapefruit peel biochar based materials had the most abundant functional groups.With the increase of temperature,the richness of functional groups decreased.SEM characterization of different kinds of biochar showed that corn straw biochar had the most abundant pore structure and the most regular arrangement.Through the bet analysis of different agricultural wastes under the best and worst conditions of H₂S adsorption performance,the specific surface area of biochar increased with the increase of temperature and time,and the largest specific surface area was corn straw biochar pyrolysis at 600℃for 120 min,which was about 6.7539m²/g,and the number of mesopores was also the largest,about 0.022535 cm³/g.（2）The pyrolysis temperature of 120℃at 600℃was studied by impregnation,traditional hydrothermal,microwave hydrothermal modification and supported transition metal salt reagent,alkaline reagent and oxidizing reagent Through the FTIR characterization of each composite biochar based materials,it can be seen that the surface functional groups of the samples prepared by the modified loading process are more abundant,among which the KMnO₄ loading and microwave hydrothermal composite process is the most obvious,and its surface has rich energy and the functional group structure of H₂S binding.The bet results show that the samples loaded with KMnO₄ have the largest specific surface area of 201.05 m²/g and the most abundant pore structure.SEM characterization was carried out for the biochar based materials under three different modification processes.KMnO₄ had the most abundant loading under microwave hydrothermal process.EDS characterization showed that the Mncontent of this type of biochar based materials reached 22.14 wt%.XRD characterization showed that KMnO₄ was mainly loaded with high valence Mn,which proved its strong oxidation resistance.The dynamic adsorption experiments of H₂S on27 kinds of biochar based composites were carried out.The experimental results show that the biochar based composites prepared by microwave hydrothermal modification process loading KMnO₄ composite process have the longest H₂S penetration time of129 min,and its sulfur penetration capacity reaches 33.366%mg/g,which is about 6times of the original biochar based adsorption performance,and its removal rate of H₂S is the highest,which is 90.73%,which proves that this sample has a great application prospect of removing H₂S from ambient air.（3）The experimental results of dynamic adsorption of H₂S on unmodified biochar based samples（PSBC09,CSBC09,RSBC09,SPBC09）and composite modified biochar based samples（1-B,4-B,8-C）were fitted with five kinds of kinetic models.The fitting results of kinetic reaction model showed that the unmodified biochar based samples could well fit with the quasi first order kinetic model,and the adsorption mechanism of H₂S on unmodified biochar based samples was studied The results of elovich equation fitting showed that the correlation coefficients R² of unmodified biochar samples were greater than 0.99,which indicated that the reaction mechanism was single,while the correlation coefficient of composite modified biochar samples was low,It shows that the reaction mechanism is more complex;Yoon Nelson model fitting results show that all samples have a high correlation,R²>0.985,and the fitting value at 50%penetration is close to the experimental value,which shows that Yoon Nelson model can accurately predict the adsorption of H₂S on biochar and its composites;Bangham model fitting results show that the correlation coefficients of all samples are greater than 0.98,which has a high correlation The good fitting correlation indicates that the adsorption rate equation of H₂S on biochar based materials can be obtained by Bangham model.