Isotherm and kinetic studies for the biosorption of cadmium from aqueous solution by Alhaji maurorum seed

Cadmium is an extremely toxic metal commonly found in industrial regions. Anthropogenic activity is the most important factor causing its interference to water, soil and air resources. The aim of many researches is to present remediation strategy or to remove cadmium from contaminated resources through an economical and efficient method. Cadmium adsorption from aqueous solution using Alhaji maurorum seed adsorbent has been investigated and optimized in this study. Moreover, isotherm and kinetics of adsorption process was studied. The seeds are washed by distilled water after separation from the plant, and then dried in room temperature for 48 h. They are powdered by grinder and passed through sieve no.18 as well. Adsorption process was optimized in 4 steps regarding pH, contact time, adsorption dose and initial concentration of cadmium effects. The cadmium concentration in solution was measured using ICP-OES method. The results of optimization tests showed that the optimum condition of cadmium adsorption (85.5% removal) occurs at pH of 6.5 with 20 g/L of adsorption dose for 45 min. In addition, the efficiency of adsorption process increases as the cadmium concentration reduces in the initial solution. Adsorption process follows the pseudo second-order kinetics and Freundlich isotherm with correlation coefficients of 0.999 and 0.99, respectively. According to the findings of this analysis, it was concluded that A. maurorum seed is a good biological adsorbent for adsorbing cadmium from aqueous solution.     

氨氮生物硝化分段动力学特性研究

本文利用富集培养的硝化污泥研究了氨氮生物硝化动力学的基本规律.结果表明,氨氮浓度对硝化速率有显著的影响.主体溶液中氨氮质量浓度小于2.3 mg/L时,硝化符合一级反应动力学.随着溶液中氨氮浓度升高,将会出现半级(本文为0.35级)或零级反应动力学,对应的氨氮质量浓度范围分别为2.3～18.2 mg/L和18.2～100 mg/L.各级反应的速率常数分别为0.16 d-1/(mg/L)、0.23 d-1/(mg/L)0.35和0.61d-1.氨氮质量浓度不同,动力学级数不同,硝化速率不同,达到相同的硝化效率反应时间有很大的差别.由于完全混合式反应器的硝化速率主要取决于出水氨氮浓度;因此氨氮出水浓度要求越低,硝化速率越低,反应时间越长,达到较彻底的硝化程度就越困难.     

Comparative Evaluation of Three River Water Quality Models1

Abstract: Selection of a biochemical oxygen demand (BOD) reaction model to incorporate into dissolved oxygen (DO) water quality models is an overlooked choice available to river water quality modelers. Data from rivers can serve in screening methods to discriminate between competing water quality models. In this study, 15 published BOD and DO datasets based on a 7 year long study of the Bormida River in Italy are used to calibrate three‐multiorder BOD models: first‐order, three‐halves order, and second‐order, which are then included in three corresponding DO models which incorporate these BOD models. The adequacy of the first‐order, three‐halves order and second‐order BOD models was evaluated by calculating the root mean square error between a model and data. A similar procedure was followed to evaluate three DO models, each of which incorporated one of the three BOD models. The first‐order BOD model most frequently fit the river data best, followed by the three‐halves order and the second‐order BOD models. The DO model incorporating a first‐order BOD model most frequently fit the data best, followed by the DO order incorporating second‐order BOD and the DO model incorporating three‐halves order BOD.     

硫酸盐还原菌(SRB)污泥固定化小球还原硫酸盐的动力学研究

通过研究硫酸盐还原菌(SRB)污泥固定化小球还原硫酸盐过程硫酸盐浓度的变化规律,建立了反应动力学方程,确定了pH值和球液配比量对反应速率常数的影响,计算了相应的反应表观活化能.结果表明: SRB还原硫酸盐的反应为一级反应,反应动力学方程为:V=-dC/dt=0.080 56C.pH值为6-7时,SRB还原硫酸盐的反应速率常数相差不大,pH＜4和pH＞10时,反应速率常数逐渐减小.球液配比量减少,反应速率常数也随之减小,反应表观活化能增大.在实验条件下,SRB还原硫酸盐属化学控制.并由此确定了SRB污泥固定化小球还原硫酸盐的最佳工艺条件为温度35 ℃、pH值6-7、球液配比量1∶10(g/mL).     

软锰矿烟气脱硫反应过程研究

研究了软锰矿浆体系中SO2和软锰矿的宏观动力学反应过程，考察了搅拌速度、温度、浓度、矿粉粒度、固体浓度等因素对反应速度的影响，应用了反应过程中粒径不断缩小的缩芯模型描述反应过程，计算出此反应的活化能。最终揭示了SO2与软锰矿反应的宏现动力学的数学模型，为工业装置的设计和操作提供了动力学理论依据，为本工艺的工业化应用打下了坚实的基础。     

β-环糊精增敏催化动力学光度法测定亚硝酸根

在磷酸介质中利用亚硝酸根催化条件下溴酸钾氧化甲基红的褪色反应,建立了β-环糊精（β-CD）增敏催化动力学光度法,对亚硝酸根进行测定。该方法最佳反应条件为：0.05 mol/L甲基红溶液加入量8.0%（φ,下同）,0.1 mol/L溴酸钾溶液加入量12.0%,1.0 mol/L稀磷酸加入量12.0%,0.15 mol/L β-CD溶液加入量16.0%,反应温度40 ℃,反应时间15 min。亚硝酸根测定的线性范围为8.0×10^-6~6.0×10^-4 g/L,线性回归方程的相关系数为0.996 6,检出限为4.0×10^-7 g/L。亚硝酸根的加标回收率为99.0%~102.0%,水样测定结果的相对标准偏差为2.4%~3.2%。加入β-CD后测定亚硝酸根的灵敏度增加了2.5倍。     

炭化核桃壳对废水中Cr（Ⅵ）的吸附

制备了炭化核桃壳,采用SEM,EDX,FTIR等方法对炭化核桃壳进行了表征,研究了炭化核桃壳对废水中Cr（Ⅵ）的吸附效果。表征结果显示,炭化后的核桃壳为片状结构,且形成了大量的微孔,微孔数量的增加使得核桃壳的比表面积明显增大。实验结果表明,炭化核桃壳吸附处理含Cr（Ⅵ）废水的最佳工艺条件为：初始废水pH 2.0、炭化核桃壳加入量16 g/L、吸附温度25 ℃、转速150 r/min、吸附时间180 min,在此最佳工艺条件下吸附处理Cr（Ⅵ）质量浓度为20 mg/L废水,Cr（Ⅵ）去除率高达98.7%,最大吸附量为8.731 mg/g。Langmuir吸附等温模型可更好地描述炭化核桃壳对Cr（Ⅵ）的吸附过程,吸附属于单分子层吸附。拟二级动力学方程能更好地描述炭化核桃壳对Cr（Ⅵ）的吸附行为,此吸附过程以化学吸附为主控步骤。     

Pseudomonas flava WD-3固定化技术及其强化SBR污水处理的应用研究

由南四湖底泥中分离纯化出一株低温菌Pseudomonas flava WD-3,为提高其处理污水的效率并实现重复利用,本试验选取在低温(6~8℃)条件下,采用天然材料海藻酸钠(SA)和人工合成材料聚乙烯醇(PVA)共同作用的复合材料为包埋载体,利用正交试验探索其最优的固定化条件;并将最优的Pseudomonas flava WD-3固定化小球投入到SBR污水处理工艺中,探究其投加量和水力停留时间对生活污水处理效果的影响.结果发现,当SA质量分数为4%,PVA质量分数为6%,Ca Cl_2质量分数为5%,交联时间为24 h时,Pseudomonas flava WD-3固定化小球的物理性能最好,且对污水的处理效果最佳,分别是游离菌对COD、TP和NH+4-N去除效率的1.11、1.17、1.14倍.在SBR工艺中,通过连续3个月的监测数据发现,Pseudomonas flava WD-3的固定化小球对污水NH+4-N、TP、COD和TN的去除率分别介于72.78%~77.48%、62.04%~69.26%、89.08%~92.72%和85.08%~89.08%,且平均去除效率分别为未投加该菌的1.13、1.91、1.25、1.56倍,最终采取的最佳水力停留时间为8 h.并且,Pseudomonas flava WD-3在不同投加量及不同水力停留时间条件下,对污水中各污染物的降解过程符合一级动力学模型.     

UV降解水溶液中吲哚美辛的动力学研究

以中压汞灯为光源,研究水环境中吲哚美辛(IDM)的紫外光降解机制.实验结果表明,IDM的光解反应符合准一级动力学规律,其降解速率常数随自身浓度的增大而减小,当IDM浓度由1 mg·L~(-1)增至12 mg·L~(-1)时,其速率常数由0.0148 min~(-1)减至0.00412 min~(-1).通过模型研究IDM的紫外光解机制时发现,其降解包括直接光解和自敏化光解,直接光解常数为0.0151 min~(-1).研究环境因子对IDM光解的影响时发现,碱性环境有利于IDM的降解,而溶解氧抑制IDM的光解,腐殖酸通过光掩蔽和自由基猝灭两个作用抑制IDM的光解,硝酸根通过接受光量子产生·OH促进IDM的降解,并通过竞争反应实验测得·OH稳态浓度为2.10×10~(-1)4mol·L~(-1),IDM与·OH的二级反应速率常数为9.86×109L·mol~(-1)·s~(-1).     

TGA analysis of tobacco rob pyrolysis and release characteristics of noncondensable gas in a fixed-bed reactor

In this study, the size of tobacco rob (TR) particle was considered as a major factor in determining the mass loss in thermogravimetric analysis (TGA) and product yield and composition at different reactor temperatures in the fixed-bed reactor. The TGA results showed that the conversion rate increased and the activation energy (ranged from 53.29 to 58.25 kJ/mol) decreased with a decrease in particle size. The experiments demonstrated that fuel gas yield (from 0.76 to 0.82 Nm³/kg at 900 °C) increased with a decrease in particle size while char and tar yield decreased. Smaller particle sizes resulted in higher H₂ (25.68%) and CO (27.36%) contents. Minimizing the size of raw materials is an alternative method to improve the gas quality of TR pyrolysis. The increase of gas yield was attributed to the decomposition of char and tar vapor as temperature increased.