木薯茎秆连续热解炭吸附特性研究

STUDY OF ADSORPTION CHARACTERISTICS OF CONTINUOUS PYROLYSIS CASSAVA STALK CHARCOAL

以木薯茎秆为生物质原料,利用无轴螺旋连续热解装置制备木薯茎秆炭,针对原料及热解炭的组织结构、酸碱性质、表面官能团属性和表面形貌特征进行特性分析;开展木薯茎秆炭吸附溶液中亚甲基蓝、碘、苯酚和醋酸的试验,研究热解温度、粒径、振荡时间、表面清洗4个因素对炭吸附特性的影响。结果表明:随着热解温度的升高,木薯茎秆炭中挥发分含量减小,灰分及固定碳含量增大;表面逐渐形成芳香化结构,酸性官能团减少,p H值逐渐增大,碱性增强;原料表面结构不断被破坏,部分区域塌陷出现凹凸不平的表面形态。热解温度对木薯茎秆炭的吸附特性影响较大,低温热解炭的亚甲基蓝、碘和苯酚吸附值较大,高温热解炭吸附值减小,醋酸吸附值变化趋势与前三者相反。炭的粒径越小,对4种物质的吸附效果越好;振荡时间对木薯茎秆炭的吸附特性有显著影响,苯酚吸附的最佳振荡时长为60 min,醋酸为30 min。醇-水表面清洗后的木薯茎秆炭p H值减小,虽然亚甲基蓝吸附值基本不变,但碘、苯酚和醋酸吸附值增大,吸附效果改善。

The biomass pyrolysis charcoal from cassava stalk raw material was prepared by the continuous shaftless pyrolysis reactor, and the characteristic analyses of the composition structure, acid and alkali properties, surface functional groups＇ attributes and surface morphology of the raw material and pyrolysis charcoal were carried out. The experiment using charcoal from cassava stalk to adsorb methylene-blue, iodine, phenol and acetic acid was developed. And the effects of four factors, including pyrolysis temperature, particle size, oscillation time and surface cleaning, on the adsorption characteristics of charcoal were studied. The results show that with the increase of pyrolysis temperature, volatile content in cassava stalk charcoal decreases, ash content and fixed charcoal content increase. The aromatic structure is formed gradually in the surface of charcoal, acidic functional groups reduce, pH value increases gradually, alkaline enhances. Surface structure of material is destroyed unceasingly, part area of charcoal surface collapses and forms uneven morphology. The effect of pyrolysis temperature on adsorption characteristics of charcoal from cassava stalk is significant, the adsorption values of methylene-blue, iodine and phenol of low temperature pyrolysis charcoal are larger, and the adsorption values of high temperature pyrolysis charcoals decrease. The variation trend of the adsorption values for acetic acid is contrary to the former three. The smaller the particle size of charcoal is, the better the adsorption effect of four kinds of materials is. Adsorption characteristics of the charcoal are remarkably influenced by oscillation time and the best oscillation time for adsorbing phenol is 60 rain, for adsorbing acetic acid is 30 min. With alcohol-water surface cleaning, pH value of cassava stalk charcoal decreases, the adsorption value of methylene-blue remains nearly the same, but the adsorption values of iodine, phenol and acetic acid increase and the adsorption effect is improved.