准分子灯光照降解水相中烷基酚的动力学

准分子灯辐射的206 nm紫外光可以直接光解4-壬基酚(4-NP)和4-辛基酚(4-OP),但不能使之完全氧化为CO2.相同光照条件下,4-OP的去除率高于4-NP.采用拟一级动力学模型和修正的动力学模型对光解过程进行拟合,得到两种烷基酚206 nm直接光解的速率常数.结果表明,烷基酚初始浓度越低,光解速率常数越高.两种动力学模型对低浓度烷基酚直接光解都具有一定的适用性,但修正的模型不适合高浓度4-OP直接光解.UV/H2O2体系中,烷基酚的降解速率明显提高,但只有当H2O2加入量很高时,TOC去除才比较明显.最后,推导出4-OP直接光解的速率常数kd为0.0328 min-1,4-OP与H2O2反应的速率常数kpH为17.4520 L·(mol·min)-1.     

铁锰氧化物/生物炭复合材料对水中硝酸根的吸附特性

热解经过氯化铁和高锰酸钾浸渍的小麦秸秆,制备铁锰金属氧化物/生物炭复合材料,用以去除水中硝酸根.通过X射线光电子能谱和扫描电镜分析,发现复合材料表面形成了Fe(Ⅲ)/Mn(Ⅳ)二元金属氧化物颗粒.制备优化结果表明,复合材料比表面积可达153.116 m2·g-1,零电荷点可达9.76.同时,还调查了固液比、溶液初始pH值和共存阴离子等因素的影响.研究发现,复合材料在溶液pH值1.00~9.05时对NO-3的去除率维持在75.40%~78.70%,且以配位交换为主要吸附机制.共存阴离子对吸附NO-3竞争吸附的影响顺序为:Cl-SO2-4PO3-4.等温吸附实验数据符合Langmuir方程,且最大吸附量为37.361 3 mg·g-1.吸附动力学分析发现,吸附过程遵循二级动力学方程,且以化学吸附为主.热动力学分析表明,吸附过程为自发吸热过程.上述结果说明铁锰氧化物/生物炭复合材料对于去除水中NO-3具有潜在价值.     

Inhibition kinetics of acid and alkaline phosphatases by atrazine and methomyl pesticides

The main objective of this work was to investigate the kinetic characteristics of acid and alkaline phosphatases isolated from different sources and to study the effects of the herbicide atrazine and insecticide methomyl on the activity and kinetic properties of the enzymes. Acid phosphatase (ACP) was isolated from the tomato plant (Solanum lycopersicum L. var. lycopersicum); alkaline phosphatase (ALP) was isolated from two sources, including mature earthworms (Aporrectodea caliginosa) and larvae of the Egyptian cotton leafworm (Spodoptera littoralis). The specific activities of the enzymes were 33.31, 5.56 and 0.72 mmol substrate hydrolyzed per minute per milligram protein for plant ACP, earthworms ALP and cotton leafworm ALP, respectively. The inhibition kinetics indicated that atrazine and methomyl caused competitive–non-competitive inhibition of the enzymes. The relationships between estimates of K_m and V_max calculated from the Michaelis–Menten equation have been explored. The extent of the inhibition was different, as estimated by the values of the inhibition constant K_i that were found to be 3.34 × 10^?3, 1.12 × 10^?2 and 1.07 × 10^?2 mM for plant ACP, earthworms ALP and cotton leafworm ALP, respectively, with methomyl. In the case of atrazine, K_i were found to be 8.99 × 10^?3, 3.55 × 10^?2 and 1.36 × 10^?2 mM for plant ACP, earthworms ALP and cotton leafworm ALP, respectively.     

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。