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| Properties and Ammonia Nitrogen Adsorption Performance of Biochars from Different Raw Materials |
| Received:April 03, 2023 |
| DOI：10.11980/j.issn.0254-508X.2023.07.003 |
| Key Words:biochar adsorption performance low temperature pyrolysis ammonia nitrogen adsorption |
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| Abstract:In this study， three types of agricultural wastes oil sunflower straw （SS）， lentil kernels （AH） and walnut shells （WS）， with widely different tissue structures， were used as raw materials to prepare biochar materials by slow pyrolysis at low temperatures （250， 300 and 350 ℃） to explore their properties and ammonia nitrogen adsorption performance. The results showed that the pyrolysis temperatures and the types of raw materials had significant effects on the properties of biochars， and the charring temperature required for the preparation of stable biochar from SS was lowest， with a higher elemental C content. The content of oxygen-containing functional groups was negatively correlated with the pyrolysis temperature. The contents of oxygen-containing functional groups of biochars produced by SS， AH， WS at 250 ℃ were highest with the value of 2.65， 2.46， and 2.47 mmol/g， respectively. While the equilibrium adsorption of ammonia nitrogen were the highest with the biochars prepared at 300 ℃（pH value of 7）， which were 0.9512， 0.9548， and 0.6085 mg/g， respectively. The adsorption of NH4+ onto biochars was mainly caused by electrostatic adsorption， and the ammonia-nitrogen adsorption capacity of biochars was decreased under acid or cation coexistence conditions. The adsorption processes of biochars and commercial activated carbon （AC） were in accordance with the pseudo-secondary kinetic model and Langmuir model， and belonged to monolayer chemical adsorption， and the adsorption of ammonia nitrogen by biochars was higher than that by AC. |
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