氧化钙疏水改性及其对硝基苯的强化固定研究

发布时间：2018-09-10 09:34

【摘要】：石化、化工企业发生污染事故后,场地易受高浓度毒性有机物污染。毒性有机物挥发或溶解发生迁移,会对场地周围大气、土壤和地下水环境造成危害,因而需要快速固定污染物,防治其蔓延扩散。石灰是危险废物处理和污染场地修复中常用的固化/稳定化基材,但用于固定高浓度毒性有机物时,主要依赖微观结构包封作用,有机物易挥发和溶出,固定能力相对较弱。对石灰粉体表面进行改性,使其具有“疏水亲油”特性,可提高其对特定毒性有机污染物的定向捕获与固定能力,对事故情况下高浓度毒性有机物污染土壤的快速固化/稳定化具有重要意义。为开发事故情况下高浓度毒性有机物污染土壤快速稳定化剂,本论文以石灰的主要矿物组分——氧化钙(CaO)为基材,选择硬脂酸(Stearic Acid,SA)和硅烷偶联剂KH570(Silane Coupling Agent KH570,KH570)作为两种改性剂,采用湿法工艺对CaO粉体进行表面疏水改性,探讨不同工艺条件对改性效果的影响,并对改性后CaO的形态和结构进行表征。以接触角指标为疏水性强弱判定依据,硬脂酸改性CaO的最佳工艺条件为:SA添加质量分数5%,改性温度30℃,改性时间30min;KH570改性CaO的最佳工艺条件为:KH570添加量0.02mL/gCaO,改性时间40min。改性后CaO的接触角均大于90°。傅里叶红外和扫描电镜分析表明,两种改性剂均以化学吸附方式包覆在CaO表面,达到了表面疏水改性的目的。选取硝基苯作为代表性毒性有机物,以改性CaO为稳定化剂,对高浓度硝基苯污染土壤进行固化/稳定化,采用硝基苯挥发率、浸出率与固定率三个指标对疏水改性CaO的快速固化/稳定化效果进行评价。结果表明,30%添加量的疏水改性CaO作为稳定化剂能够显著抑制土壤中硝基苯的挥发和浸出,SA改性CaO和KH570改性CaO对硝基苯的固定率分别达到82.9%和75.6%,SA改性CaO对硝基苯的固定效果略优于KH570改性CaO。疏水改性CaO具有强化吸附作用,未改性CaO具有微观结构包封作用,二者联合使用(先添加疏水改性CaO混合搅拌均匀,再添加未改性CaO)对硝基苯具有更为显著的固定效果。20%的SA改性CaO与10%的未改性CaO联合使用,养护3d后硝基苯的固定率可达91.1%;20%的KH570改性CaO与10%的未改性CaO联合使用,养护3d后硝基苯的固定率可达89.2%。疏水改性CaO与未改性CaO可联合使用,作为事故情况下高浓度毒性有机物污染土壤的快速固化/稳定化材料。
[Abstract]:After the pollution accident in petrochemical and chemical enterprises, the site is liable to be polluted by high concentration of toxic organic matter. The volatilization or dissolution of toxic organic compounds will cause harm to the atmosphere, soil and groundwater around the site, so it is necessary to fix the pollutants quickly and prevent their spread and diffusion. Lime is a common solidified / stabilized base material used in hazardous waste treatment and remediation of contaminated sites, but when it is used to fix high concentrations of toxic organic matter, it mainly depends on microstructure encapsulation. Organic matter is volatile and dissolves, and its fixation ability is relatively weak. The surface of lime powder was modified to have hydrophobic and oil-hydrophobic properties, which could improve its ability to capture and immobilize specific toxic organic pollutants. It is of great significance for rapid solidification / stabilization of soil contaminated by high concentrations of toxic organic matter. In order to develop a rapid stabilizer for soil contaminated by high concentration toxic organic compounds, calcium oxide (CaO), the main mineral component of lime, was used as the base material, and stearic acid (Stearic Acid,SA) and silane coupling agent (KH570 (Silane Coupling Agent KH570,KH570) were selected as two modifiers in this paper. The surface hydrophobic modification of CaO powder was carried out by wet process. The effect of different process conditions on the modification effect was discussed. The morphology and structure of modified CaO were characterized. According to the contact angle index, the optimum technological conditions for the modification of CaO by stearic acid are as follows: the mass fraction of CaO is 5: SA, the modification temperature is 30 鈩，

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