盐渍土洗盐废水的吸附脱盐方法研究

发布时间：2018-09-09 20:22

【摘要】：土壤盐渍化现象是我国生态环境和农业发展面临的严重问题之一。我国约有四亿亩盐渍土,其改良利用的重要方法之一是“灌溉洗盐”,但该方法会产生大量的洗盐废水,废水的直接排放不仅会造成水资源的极大浪费,还可能引发次生盐渍化等环境问题。因此,洗盐废水的脱盐处理具有重要的意义。本文以来源广泛、价格低廉、环境友好的粘土矿物作为基础材料,通过实验室合成、改性等方法制备了阴、阳离子吸附材料,以实验室模拟废水和新疆盐渍土洗盐废水为研究对象,系统考察了所制备吸附材料对水中盐分离子的吸附特性,并模拟研究了吸附材料作为夹层对土壤中盐分的水迁移(水盐运动)的抑制作用,为盐渍土洗盐废水的处理提供理论依据。主要研究结果如下:1)镁铝水滑石的制备及其对Cl-和SO42-的吸附特性。分别以Cl-和SO42-的吸附量为依据,优化硝酸根型镁铝水滑石(NO3--LDH)和焙烧碳酸根型镁铝水滑石(CO32--LDO)的制备条件,最佳条件为NO3--LDH摩尔比为2:1,CO32--LDO摩尔比为3:1,并在400℃下焙烧3 h;采用XRD、FT-IR、SEM和TG-DSC对这两种水滑石的结构进行表征,结果证明水滑石具有较好的层状结构和热稳定性。NO3--LDH和CO32--LDO对Cl-或SO42-的吸附特性表明,当p H在4~10的范围内变化时,对Cl-和SO42-的吸附量均随p H值变化不大,而在p H4或p H10时,吸附量则明显降低;对Cl-和SO42-的吸附均呈现先快后慢的特点,在4 h左右基本达到吸附平衡。动力学和吸附等温线分析结果表明:动力学数据可用拟二级速率方程进行拟合,相关系数达到0.99以上,吸附过程符合Langmuir等温模型,表现为单分子层吸附。NO3--LDH对Cl-和SO42-的最大吸附量分别为92.05、151.89 mg?g-1,CO32--LDO对Cl-和SO42-的最大吸附量为51.23、233.38mg?g-1。在Cl-和SO42-的混合体系中,NO3--LDH、CO32--LDO均对SO42-表现出一定的吸附选择性,以CO32--LDO表现更佳。NO3--LDH和CO32-LDO都具有较好的重复使用性,重复使用3次后,吸附量仍分别为最初吸附量的80.35%和52.42%。以上结果表明NO3--LDH、CO32--LDO对Cl-和SO42-均具有较好的吸附性能,但二者区别在于CO32--LDO以OH-交换吸附阴离子,而NO3--LDH则以NO3-交换吸附阴离子。2)改性膨润土的制备及其对Na+、Mg2+、K+、Ca2+的吸附特性。将天然膨润土于200℃下焙烧2 h进行热活化,再分别以不同浓度的(NH4)2CO3和H2SO4对其改性制备了铵化膨润土(Am B)和酸化膨润土(Ac B),采用XRD、FT-IR以及SEM对其结构进行表征,发现Am B和Ac B具有更大的比表面积。以模拟新疆盐渍土洗盐废水为研究对象,Am B、Ac B对单一K+、Ca2+、Na+、Mg2+的吸附特性研究表明,随着p H的增大,K+、Ca2+、Na+、Mg2+的吸附量均呈现上升趋势。动力学数据和吸附等温线结果:动力学数据均可用拟二级速率方程进行拟合,吸附过程符合Freundlich等温模型。Am B对Na+、Mg2+、K+、Ca2+的最大吸附量分别为53.67、25.79、17.77、25.59 mg?g-1;Ac B的最大吸附量分别为:46.32、20.15、22.17、25.72mg?g-1。在四元混合体系中,Am B、Ac B对Na+、Mg2+、K+、Ca2+均表现出一定的吸附选择性,吸附顺序为Ca2+K+Mg2+Na+。二者的主要区别在于Am B和Ac B分别是以NH4+和H+交换吸附阳离子的。3)为了达到脱盐的目的,则应避免在吸附的同时还产生其它盐分离子,故选择将CO32--LDO和Ac B复合处理新疆盐渍土洗盐废水中(盐度0.47%)的阴、阳离子,从而OH-和H+结合生成水,实现脱盐。考察了CO32--LDO和Ac B投加量、组成比例、投放顺序、吸附时间、废水浓度、C-PAM量等对脱盐效果的影响。结果表明:当Ac B与CO32--LDO的总投加量为4 g,质量比为2:1,吸附时间为4 h,C-PAM投加量为0.3 mg?L-1时,脱盐效果最佳,脱盐率可达到27.21%。4)将CO32--LDO和Ac B混合作为夹层置于土壤层中,探索研究了其对土壤中水盐运动的抑制作用,包括吸盐渣厚度、吸盐渣层位以及模拟地下水矿化度等因素的影响。结果表明,CO32--LDO和Ac B的夹层对水盐运动的抑制作用主要基于两方面:吸盐渣对地下水中盐分离子的吸附作用和夹层可以明显减慢地下水上升的速度。双重作用使得土壤中吸盐渣越厚,层位越高时,抑制表土返盐的作用越明显。
[Abstract]:Soil salinization is one of the serious problems facing the ecological environment and agricultural development in China. There are about 400 million mu of saline soil in China. One of the important methods for its improvement and utilization is "irrigation and washing salt". But this method will produce a large number of salt-washing wastewater. The direct discharge of wastewater will not only cause a great waste of water resources, but also may lead to secondary. Therefore, desalination treatment of salt washing wastewater is of great significance. In this paper, anion and cation adsorption materials were prepared by laboratory synthesis and modification with clay minerals as basic materials, which are widely used, inexpensive and environmentally friendly. Objectives: The adsorption properties of the adsorbents for salt in water were investigated systematically, and the inhibition effect of the adsorbents as intercalation layers on the movement of salt in soil was simulated to provide theoretical basis for the treatment of salt washing wastewater from saline soil. Based on the adsorption capacity of Cl-and SO42-respectively, the preparation conditions of nitrate-type Mg-Al hydrotalcite (NO3-LDH) and calcined carbonate-type Mg-Al hydrotalcite (CO32-LDO) were optimized. The optimum conditions were that the molar ratio of NO3-LDH was 2:1, the molar ratio of CO32-LDO was 3:1, and the molar ratio of CO32-LDO was calcined at 400 C for 3 h. XRD, FT-IR, SEM and TG-DSC were used for the preparation of these two kinds of Mg-Al hydrotalcites. The adsorption properties of NO3-LDH and CO32-LDO to Cl-or SO42-showed that the adsorption capacity of Cl-and SO42-changed little with P H in the range of 4-10, but decreased significantly at P H 4 or P H 10. The results of kinetics and adsorption isotherm analysis show that the kinetic data can be fitted by quasi-second-order rate equation, and the correlation coefficient is above 0.99. The adsorption process conforms to Langmuir isotherm model, showing that the adsorption of Cl-and SO42-by NO3--LDH is monolayer adsorption. The maximum adsorption capacity of Cl-and SO42-were 92.05,151.89 mg?G-1,CO32-LDO and 51.23,233.38 mg?G-1,respectively. In the mixed system of Cl-and SO42-NO3-LDH and CO32-LDO showed a certain adsorption selectivity for SO42-and CO32-LDO showed better performance. The results showed that NO3-LDH and CO32-LDO had good adsorption properties for Cl-and SO42-respectively, but the difference was that CO32-LDO adsorbed anions by OH-exchange, while NO3-LDH adsorbed anions by NO3-exchange. Ammonium bentonite (Am B) and acidified bentonite (Ac B) were prepared by calcination of natural bentonite at 200 C for 2 h and modification with different concentrations of (NH4) 2CO3 and H2SO4 respectively. Their structures were characterized by XRD, FT-IR and SEM. It was found that Am B and Ac B had larger specific surface area. The adsorption characteristics of single K+, Ca 2+, Na+, Mg 2+ by Am B and Ac B were studied. The adsorption capacity of K+, Ca 2+, Na+, Mg 2+ increased with the increase of P H. The kinetic data and adsorption isotherm were fitted by quasi-second-order rate equation. The adsorption process was in accordance with Freundlich isotherm model. The maximum adsorption capacities of Na+, Mg2+, K+, Ca2+ by MB were 53.67, 25.79, 17.77 and 25.59 m g?G-1, respectively, and those of Ac B were 46.32, 20.15, 22.17, 25.72 m g?G-1. In the Quaternary system, Am B and Ac B showed certain adsorption selectivity to Na+, Mg2+, K+, Ca2+, and the order of adsorption was Ca2+K+Mg2+Na+. In order to achieve the goal of desalination, we should avoid producing other salt separators while adsorbing. Therefore, we choose to treat the anions and cations in Xinjiang saline soil washing wastewater (salinity 0.47%) by the combination of CO32-LDO and ACB, and then OH-and H-combine to form water to realize desalination. The results show that when the total dosage of Ac B and CO32-LDO is 4 g, the mass ratio is 2:1, the adsorption time is 4 h, and the dosage of C-PAM is 0.3 mg?L-1, the desalination effect is the best, and the desalination rate can reach 27.21%. 4) The mixture of CO32-LDO and ACB is used as desalination agent. The results show that the inhibiting effects of the intercalation layers of CO32-LDO and ACB on the movement of water and salt in groundwater are mainly based on two aspects: the effect of the salt-absorbing slag on the salt separators in groundwater. Adsorption and intercalation can obviously slow down the rising rate of groundwater. The thicker the salt-absorbing residue in the soil and the higher the horizon, the more obvious the effect of inhibiting the return of salt is.
【学位授予单位】：四川师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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