污泥-玉米秸秆热解制生物炭及其对Pb^(2+)的吸附特性

Preparation of biochar from co-pyrolysis of sewage sludge-corn straw and its adsorption for Pb^(2+)

开展了脱水污泥单独热解及其与玉米秸秆共热解(泥秆质量分别为9∶1,8∶2,5∶5)制备生物炭吸附剂的研究。采用元素分析、扫描电镜和比表面积仪对4种生物炭的理化特性及微观形貌进行了全面分析。结果表明,在相同热解温度下,随着玉米秸秆掺杂量的增加,生物炭产率及灰分含量降低,全碳含量增加,pH值略有下降,生物炭比表面积和总孔体积增大,棒状残焦分布量增多,孔结构更加发达。生物炭对Pb^(2+)的吸附动力学符合准二级动力学模型,吸附过程分为快反应和慢反应两个阶段,吸附实验前10 min的吸附量达到饱和吸附量的80%以上。Dubinin-A模型较好地描述了生物炭对Pb^(2+)的等温吸附行为,4种生物炭对Pb^(2+)的饱和吸附量大小依次为:SSMT50%(44. 8 mg/g)> SS-MT20%(38. 1 mg/g)> SS-MT10%(30. 7 mg/g)> SS(21. 7 mg/g),表明污泥-玉米秸秆生物炭有作为重金属Pb吸附剂的潜力。

Biochar was prepared by the sole pyrolysis of sewage sludge and co-pyrolysis of sewage sludge/corn straw at different mass ratios(9∶1,8∶2 and 5∶5).The physicochemical properties and surface topography of biochar prepared from sole pyrolysis and co-pyrolysis were compared through elemental analysis,SEM and BET method.The results showed that,at the same pyrolysis temperature,with the increasing of mixing ratio of corn straw,the biochar yield and ash content decreased;the carbon content increased;the pH decreased.Meanwhile,the specific surface area and total pore volume of biochar increased,the rodlike residual char content increased and its surface became very rough and appeared porous.The sorption of Pb 2+on biochar followed the pseudo-second-order dynamic sorption model,the sorption of Pb 2+on the biochar was developed by two processes:rapid adsorption process and slow adsorption process,the adsorption of the biochar in the first ten minutes was>80%of its maximum capacity.The isotherm sorption behavior was described by the Dubinin-A model,the amount of Pb 2+absorbed by biochar was in the order SS-MT50%(44.8 mg/g)>SS-MT20%(38.1 mg/g)>SS-MT10%(30.7 mg/g)>SS(21.7 mg/g)at 298.15 K.Biochar from co-pyrolysis of sewage sludge-corn straw could be used effectively as an adsorbent to remove Pb from wastewater.