不同原料低温生物炭的性质及氨氮吸附性能

Properties and Ammonia Nitrogen Adsorption Performance of Biochars from Different Raw Materials

关键词:  生物炭  吸附性能  低温热解  氨氮吸附

Key Words:biochar  adsorption performance  low temperature pyrolysis  ammonia nitrogen adsorption

摘要:本研究以油葵秸秆（SS）、扁桃核（AH）和核桃壳（WS）3种组织结构差异较大的农业废弃物为原料，在低温下（250、300、350 ℃）慢速热解制备生物炭材料，探究其性质与氨氮吸附性能。结果表明，热解温度和原料种类对生物炭的性质影响较大，由SS制备性质稳定的生物炭所需碳化温度低，且C元素含量高。含氧官能团含量与热解温度呈负相关，SS、AH和WS在250 ℃时制备生物炭的含氧官能团含量最高，分别为2.65、2.46和2.47 mmol/g；而300 ℃时制备的生物炭对氨氮的平衡吸附量最大（pH值=7），分别为0.9512、0.9548和0.6085 mg/g。生物炭与溶液中NH₄⁺吸附时存在静电作用，在酸性或阳离子共存条件下，吸附量降低。生物炭和商业活性炭（AC）的吸附过程均符合伪二级动力学模型与Langmuir模型，属于单层化学吸附，且生物炭对氨氮的吸附量高于AC。

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.