热解温度对污泥碳基材料表面性质及吸附性能的影响

Effect of pyrolysis temperature on the surface properties and adsorption performance of sludge biochar

以市政污泥为原料,在300、400、500、600、700和800℃无氧气氛下,热解制备了污泥基生物炭。采用BET、SEM、XPS、FT-IR对不同热解温度下污泥炭进行了表征分析;研究了不同热解温度下污泥炭对污水中有机物的吸附效果和动力学;探究了热解温度对污泥炭微观调控下吸附实际水体中有机物的匹配机质。结果表明,随热解温度的升高,C—H、C—C结合比例降低,C=C、C—O=C比例升高,芳香化程度增加,且比表面积、孔容及表面粗超度均有所增加,1~2 nm微孔比例增多,介孔向微孔发展趋势逐渐明显。800℃热解温度条件下制备的污泥炭对二沉池出水中有机物的吸附效果优于其他温度下制备的污泥炭。吸附温度为298.15 K时,最大吸附容量为282.5 mg·g^-1,且符合准二级吸附动力学。高温下制备的污泥炭对水体中腐殖酸和富里酸具有较强的吸附效能。这主要是由于表面丰富的含氧官能团、芳香键与腐殖酸和富里酸发生了氢键、化学键缔合作用和π-π共轭作用,同时污泥碳表面发达的孔隙结构和较大的比表面积也提供了更多的活性结合位点,促进了污染物的吸附。

Biochar was derived from municipal sewage sludge at five different temperatures(400,500,600,700 and 800℃)in an anaerobic environment,which was characterized by using BET,SEM,XPS and FT-IR.The adsorption effect and kinetics of organic matter in sewage on sludge biochar at different pyrolysis temperatures were studied.The matching mechanism of organic matter adsorption in actual water on microcontrolled biochar by pyrolysis temperature was also discussed.The results showed that with the increase of the pyrolysis temperature,the ratios of C—H,C—C decreased,while the ratios of C=C,C—O=C increased,the aromatization degree,specific surface area,pore volume,surface roughness and micro-pore ratio of 1~2 nm increased,the transformation trend from meso-pores to micro-pores was gradually obvious.The adsorption capability of organics in the effluent of secondary tank on sludge biochar prepared at pyrolysis temperature of 800℃was better than that prepared at other temperatures.The corresponding maximum adsorption capacity was 282.5 mg·g^-1 at adsorption temperature of 298.15 K,and the adsorption kinetics conformed to the quasi-secondorder adsorption kinetics equation model.Biochar had strong adsorption efficiency towards humic acid and fulvic acid in water.The main reason was the hydrogen bonds,chemical bond association andπ-πconjugation functions occurred between the abundant oxygen-containing functional groups,aromatic bonds on the surface of sludge biochar and humic acid or fulvic acid.Meanwhile,the developed pore structure and large specific surface area of sludge biochar provided lots of active binding sites and promoted the adsorption of pollutants.