杨树叶吸附水中硝基苯研究

发布时间：2018-01-16 06:02

本文关键词：杨树叶吸附水中硝基苯研究　出处：《南京林业大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来硝基苯污染事件时有发生,硝基苯在自然界中难以有效降解,往往需要借助吸附、高级氧化等技术进行处理。将林业废弃物——杨树叶进行循环利用,通过研磨成粉、制备成粒、改性、炭化和与其它工艺联用等方式,探究杨树叶在不同条件下对硝基苯的吸附性能,并确定其用于硝基苯吸附处理的有效工艺参数,主要研究结果如下:(1)杨树叶的主要组成元素是O、C、Si、Ca、K等,其中C重量在30%以上。通过电镜扫描图发现杨树叶内部具有丰富的孔隙,它们为杨树叶吸附水中硝基苯提供了有利的通道和空隙。(2)20°C下,投加20g/L杨树叶粉末、成型颗粒处理10mg/L硝基苯废水时,吸附率分别为62.7%、59%。粉末、颗粒的吸附过程分别较好地符合准一级吸附动力学模型、准二级吸附动力学模型;它们的吸附等温线都更符合Langmuir等温方程,是放热吸附过程,也表明杨树叶粉末、颗粒与硝基苯分子主要通过单层吸附发生相互作用。对吸附饱合后的杨树叶粉末、颗粒展开6次解吸重吸附后,吸附率各为首次解吸后的2/3、3/4。(3)利用磷酸对杨树叶进行改性时,做了改性温度、改性剂浓度和用量三个因素的影响实验,并由此确定了最佳改性条件:25°C;2mol/L;15ml/g。对改性后的杨树叶做静态吸附实验。25°C下,向5mg/L的硝基苯溶液中分别投加35g/L的粉末和颗粒,振荡70min和50min后,吸附率达到95%和83%。它们的吸附过程均与准二级吸附动力学模型有较好的拟合,等温吸附符合Freundlich方程。通过红外光谱对改性杨树叶进行吸附的主要官能团展开分析,发现主要是羟基的作用。(4)在300°C下炭化杨树叶后,对其展开吸附实验。向10mg/L硝基苯中分别投加35g/L杨树叶粉末、颗粒,振荡50min后吸附率分别可达到91%、80%,较没炭化之前提高了约30%、15%。吸附过程分别较好地符合Langmuir等温方程和Freundlich等温方程。(5)在与活性炭联合吸附实验中,为使40mg/L的硝基苯废水达到国家排放标准,对于粉末型吸附剂,需投加4g/L的活性炭粉末和15g/L以上的杨树叶粉末;对于颗粒型吸附剂,需投加10g/L的活性炭颗粒和至少20g/L的杨树叶成型颗粒。在臭氧与杨树叶吸附联用实验中,为使100mg/L硝基苯废水达到国家排放标准,要先调节pH为10,在35°C下曝气氧化35min,然后投加30g/L杨树叶粉末或40g/L杨树叶成型颗粒进行吸附。综上所述,杨树叶对硝基苯具有较好的去除能力,特别对其改性或炭化后,吸附性能明显加强,适用于处理中低浓度的硝基苯废水。针对较高浓度的硝基苯废水,可以运用杨树叶与活性炭联合吸附、臭氧氧化与杨树叶吸附联用的方法使其浓度达到国家排放标准。
[Abstract]:In recent years, nitrobenzene pollution events occur from time to time, nitrobenzene in nature is difficult to effectively degrade, often need to use adsorption, advanced oxidation and other technologies to deal with the forest waste-poplar leaves for recycling. The adsorption properties of nitrobenzene in poplar leaves under different conditions were investigated by grinding, granulation, modification, carbonization and combined with other processes. The main results are as follows: (1) the main components of poplar leaves are Ocarinus sinensis, CaAK and so on. The weight of C is more than 30%. It is found that there are abundant pores in poplar leaves by scanning electron microscope, which provide favorable channels and voids at 20 掳C for absorbing nitrobenzene in water of poplar leaves. When 20 g / L poplar leaf powder was added, the adsorption rates of 10mg / L nitrobenzene wastewater were 62.7% and 59.9%, respectively. The adsorption process of the particles is in good agreement with the quasi-first-order adsorption kinetic model and the quasi-second-order adsorption kinetic model respectively. Their adsorption isotherms are more in line with the Langmuir isotherm equation, which is an exothermic adsorption process, which also indicates that poplar leaf powder. The adsorption rate of the adsorbed poplar leaf powder was 2/3 after the first desorption of poplar leaves after 6 desorption resorption. 3 / 4. 3) when poplar leaves were modified with phosphoric acid, the effects of modification temperature, concentration and dosage of modifier on poplar leaves were studied, and the optimum modification conditions were determined as follows: 25 掳C; 2 mol / L; The static adsorption experiment of modified poplar leaves was carried out at 15 ml / g. At 25 掳C, 35 g / L powder and particle were added to 5 mg / L nitrobenzene solution, respectively. After oscillating for 70min and 50min, the adsorption rates reached 95% and 83.The adsorption processes were all fitted well with the quasi-second-order adsorption kinetic model. The isothermal adsorption accords with Freundlich equation. The main functional groups of modified poplar leaves were analyzed by infrared spectroscopy. It was found that hydroxyl group mainly acted on poplar leaves at 300 掳C. after carbonization, adsorption experiments were carried out. 35g / L poplar leaf powder was added to 10mg / L nitrobenzene. After shaking for 50 minutes, the adsorption rate can reach 91% and 80% respectively, which is about 30% higher than that before carbonization. The adsorption process was in accordance with Langmuir isothermal equation and Freundlich isothermal equation respectively. In order to make the 40 mg / L nitrobenzene wastewater meet the national discharge standard, 4 g / L of activated carbon powder and 15 g / L of poplar leaf powder should be added to the powder adsorbent. For granular adsorbents, 10 g / L of activated carbon particles and at least 20 g / L of poplar leaf forming particles should be added. In order to make 100 mg / L nitrobenzene wastewater meet the national discharge standard, the pH should be adjusted to 10, and aeration oxidation at 35 掳C for 35 min. Then 30 g / L poplar leaf powder or 40 g / L poplar leaf molding particles were added for adsorption. In conclusion poplar leaves have better removal capacity of nitrobenzene especially after modification or carbonization. It is suitable for the treatment of middle and low concentration nitrobenzene wastewater. For the higher concentration of nitrobenzene wastewater, poplar leaves and activated carbon can be used to combine adsorption. The combination of ozone oxidation and poplar leaf adsorption makes its concentration up to the national emission standard.
【学位授予单位】：南京林业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703;O647.3

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