木薯渣基生物质炭的制备及其对土壤中莠去津吸附解吸性能的研究

发布时间：2018-06-16 13:00

本文选题：木薯渣生物质炭 + 结构特征　；参考：《海南大学》2015年硕士论文

【摘要】：本研究以热区特有的农业废弃物木薯渣生物质为前驱材料,采用限氧持续升温法,于350℃、550℃和750℃下热解制得3种不同性质的生物质炭(简称BC,分别标记为：MS350、MS550和MS750),借助热重分析仪、元素分析仪、傅立叶红外光谱仪、扫描电镜等仪器对其性质进行了表征。以莠去津农药为目标污染物,考察了木薯渣基生物质炭的输入对砖红壤、红壤、燥红土中莠去津的吸附解吸行为及再释放的影响。旨在揭示木薯渣基生物质炭对土壤中莠去津的吸附隔离规律和机理,为生物质炭的农用及土壤中农药的污染控制治理与风险评估提供依据。本文取得的主要结论如下： (1)木薯渣的升温裂解是一个芳香性增强、亲水性和极性减弱的过程(O/C和(N+O)/C降低)；生物质炭的灰分含量和pH值随着热解温度的上升而增加；木薯渣经炭化处理后,其表面形貌和结构发生了变化,形成了更多的微孔(0.144cm3/g),从而具有高比表面积(MS750:430.37m2/g)。 (2)砖红壤、红壤和燥红土对莠去津的吸附能力存在明显差异,吸附过程分为快速表面点位吸附阶段和慢速孔隙填充阶段,可用伪二级动力学方程(R20.993)进行描述分析；吸附等温线表现为非线性,Freundlich、Langmuir模型都可用于模拟该过程,解吸过程存在明显的滞后效应；除燥红土外,莠去津在砖红壤和红壤上的吸附是自发进行的,且属于吸热反应。 (3)生物质炭土壤对莠去津的吸附动力学过程包括快速和缓慢两个阶段,可用伪二级动力学方程进行更好的描述；其吸附强度大小与所添加生物质炭的关系为MS750 MS550 MS350,且与同种生物质炭的添加量在0.1%-5%内呈正相关性。Temkin方程更适用于描述莠去津的吸附/解吸等温线,其解吸过程存在明显的迟滞现象,多表现为负滞后作用,生物质炭表面的微孔结构是产生该现象的主要原因之一；莠去津的吸附过程属于吸热反应,是物理吸附(|△G0|20kJ/mol),氢键是主要的吸附作用力。生物质炭的添加可以增强土壤对莠去津的吸附能力。 (4)研究了溶液pH值、固液比、炭投加量和重金属共存对莠去津在添加1%BC的砖红壤上的吸附解吸过程的影响,结果表明：生物质炭土壤对莠去津的吸附强度随着pH值的增大而减少,溶液pH值为7时解吸量最大；固液比变化对莠去津的吸附解吸性能影响表现为1：201：101：5；炭添加水平越高,对莠去津的亲和力越强,解吸越弱：重金属的共存对莠去津的吸附影响较弱,但对解吸过程的影响较明显,可能是重金属存在会抢夺生物质炭土壤提供的吸附位点。生物质炭的输入增强了土壤对莠去津农药的隔离能力,其中以MS750最为明显。4种因素的变化对5%BC处理释放莠去津基本无影响。 (5)生物质炭土壤对莠去津的慢吸附行为表现为：随着吸附过程的进行,农药吸附量逐渐增加,但增加幅度逐渐减少最后达到饱和。考察了pH值、固液比、离子强度和扰动因素对莠去津再释放的影响,发现：随着溶液pH值的增加,莠去津的释放量逐渐增加；低固液比利于莠去津的吸附固定；离子强度变化和扰动强度与莠去津的释放并无明显规律。
[Abstract]:In this study, the biomass of cassava residue, a specific agricultural waste, was used as precursor material, and 3 kinds of biomass charcoal (BC, MS350, MS550 and MS750) were prepared by pyrolysis at 350, 550 and 750 C by constant oxygen limiting method. The effects of atrazine based biomass carbon on the adsorption and desorption behavior of atrazine in the red soil, red soil and dryness red soil were investigated to reveal the adsorption and desorption of atrazine and the mechanism of the adsorption and isolation of atrazine in the soil. The main conclusions of this paper are as follows:
(1) the heating and cracking of cassava dregs is a process of enhanced aroma, the decrease of hydrophilicity and polarity (O/C and (N+O) /C). The ash content and pH value of biomass carbon are increased with the increase of pyrolysis temperature. After carbonization, the surface morphology and structure of cassava residue have been changed to form more micropores (0.144cm3/g). There is a high specific surface area (MS750:430.37m2/g).
(2) there are obvious differences in the adsorption capacity of atrazine in red soil, red soil and dryness red soil. The adsorption process is divided into fast surface point adsorption stage and slow pore filling stage, which can be described and analyzed by pseudo two order kinetic equation (R20.993). The adsorption isotherm is non linear, Freundlich and Langmuir model can be used to simulate the process. In addition, the adsorption of atrazine on laterite and red soil is spontaneous and is endothermic reaction.
(3) the adsorption kinetics of atrazine in biomass carbon soil includes fast and slow two stages, which can be described better by pseudo two kinetics equation. The relationship between the adsorption strength and the added biomass carbon is MS750 MS550 MS350, and the.Temkin equation is positively correlated with the addition of the same biomass carbon in 0.1%-5%. It is more suitable for the adsorption / desorption isotherm describing atrazine. The desorption process has obvious hysteresis, and most of them are negative hysteresis. The microporous structure of the surface of biomass carbon is one of the main reasons for this phenomenon. The adsorption process of atrazine belongs to the endothermic reaction. It is the physical adsorption (G0|20kJ/mol) and the hydrogen bond is the main adsorption. The addition of biochar can enhance soil's ability to adsorb atrazine.
(4) the effect of pH value, solid to liquid ratio, carbon dosage and coexistence of heavy metals on the adsorption and desorption of atrazine on the red soil added to 1%BC was studied. The results showed that the adsorption strength of atrazine decreased with the increase of pH value in biomass carbon soil. The adsorption capacity of Atrazine was the maximum when the solution pH value was 7; the adsorption of atrazine to the solid liquid ratio changed to atrazine The effect of desorption performance is 1:201:101:5, the higher the carbon addition level, the stronger the affinity for atrazine, the weaker the desorption: the adsorption of atrazine is weaker, but the effect on the desorption is more obvious. It may be the adsorption site for the heavy metals to snatch the biomass carbon soil. The isolation ability of soil to atrazine was enhanced. MS750 was the most obvious. The change of.4 factors had no effect on the release of atrazine by 5%BC treatment.
(5) the slow adsorption behavior of atrazine in biomass carbon soil is as follows: with the process of adsorption, the adsorption amount of pesticide increases gradually, but the increase is gradually reduced and finally reached saturation. The effects of pH value, solid to liquid ratio, ionic strength and disturbance factors on atrazine re release are investigated. It is found that atrazine is released with the increase of pH value of the solution. The low solid liquid ratio is favorable for the adsorption and fixation of atrazine. There is no obvious rule for the change of ionic strength and disturbance intensity with the release of atrazine.
【学位授予单位】：海南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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