KINETICS AND MECHANISM OF THE REACTION BETWEEN OZONE AND O-CRESOL IN AQUEOUS SOLUTIONS

The stopped-flow spectrophotomctric method was applied to study the kinetics of the ozonation of o-cresol in aqueous solutions of pH values varying from 2 to 9 at 10 to 40°C. The fast reaction between o-cresol and ozone is second order overall with first order in each reactant. The ozonation rale increases with the temperature and pH value of the solution. In neutral solutions, the overall rate constant increases from 422,000 M^-1S^-1 at 10°C to 1,549,000 M^-1 S^-1 at 40°C. The activation energy is about 30 KJ/mol in the neutral solutions; it increases slightly with the acidity of the solution.

A mechanism based on the initial attack of ozone moleculesat the ortho and para positions of o-cresol is proposed for the ozonation reaction. According to this mechanism, three moles of ozone are required to react with each mole of o-cresol resulting in the rupture of the aromatic ring and production of various acids. The oxidation products were identified by these and other investigators. The proposed mechanism yields a second order kinetics for the overall reaction, as confirmed by the kinetic experiments.     

坡缕石对水中亚甲基蓝的吸附动力学

研究了坡缕石对水中亚甲基蓝的吸附动力学,在初始浓度为120～210mg/L,转速为100～200r/min,温度为298～328K时,坡缕石对亚甲基蓝的吸附动力学数据均符合准二级速率方程.结果表明:坡缕石对亚甲基蓝的吸附仅在外表面吸附,吸附表观活化能为13.92 kJ/mol,说明此吸附并不是由单一的化学吸附为速率控制步骤,是由化学吸附和液膜扩散共同控制的吸附过程.     

SYNTHESIS OF ACTIVATED CARBON FROM JATROPHA SEED COAT AND APPLICATION TO ADSORPTION OF IODINE AND METHYLENE BLUE

This article provides evidence that jatropha seed coat residues can be used as a carbon source for preparing activated carbons that have good adsorption properties for iodine and methylene blue. Activated carbons were prepared using three different methods of activation, physical, chemical, and physico-chemical, for a range of activation temperatures (600°, 700°, 800°, and 900°C) and activation hold times (1, 2, and 3 h). The highest BET surface area (1479 m² g^?1) and the highest iodine adsorption (1511 mg g^?1) were obtained with physico-chemical activation at a temperature of 900°C and a hold time of 2 h. This activated carbon gave higher BET surface area and iodine adsorption than commercial activated carbon (1169.1 m² g^?1 and 1076 mg g^?1). The activated carbons prepared by physico-chemical activation at 900°C and 2 h were then tested for adsorption of methylene blue at a range of concentrations of methylene blue (100, 200, 300, 400, and 500 mg L^?1). It was found that a Langmuir isotherm gave a better fit (R ² = 0.999) to the observed adsorptions than a Freundlich isotherm (R ² = 0.884). For the adsorption kinetics, a pseudo-second-order model gave a better fit (R ² > 0.998, Δq _e  = 3.7%) than a pseudo-first-order model (R ² ≈ 0.95, Δq _e  = 85.6%). These results suggest that chemisorption is the rate-controlling step for the adsorption of methylene blue. The experimental results show that jatropha seed coat is a lignocellulosic waste precursor for preparation of activated carbon that is an alternative source for preparation of commercial-grade activated carbons.     

间甲酚臭氧化反应动力学

INTRODUCTION Wastewater containing phenolic compounds is a kind of ordinary industrial wastewater.Phenolic compounds are harmful and toxic to marine life and human being[1].     

废水中氨及甲苯的O3／H2O2氧化降解及其动力学

研究了废水中的无机污染物氨和有机污染物甲苯在Ｏ３／Ｈ２Ｏ２ 中的氧化降解过程。根据Ｏ３／Ｈ２Ｏ２ 反应产生自由基ＯＨ·的机理和污染物在Ｏ３／Ｈ２Ｏ２ 中的氧化降解过程,推导出污染物被Ｏ３／Ｈ２Ｏ２氧化降解时的动力学模型,实验结果与理论模型相符。     

分光光度法测定油井岩芯的吸蓝量

介绍一种确定吸蓝反应终点的新方法。与通常采用的晕环法相比,该方法具有更高的准确性。与普通的分光光度法相比,该方法的优点是不需要用标准蒙脱石样品作标准曲线。根据所建立的方法测定蒙脱石的质量分数时,可以减小由于样品的不均匀性而产生的误差。对于某一油井岩芯样品,经过６ 次平行测定,蒙脱石质量分数的平均值为１５ ．１ ％ ,相对标准偏差为０ ．１ ％ 。     

Decolorization of textile basic dye in aqueous solution by ozone

In this study, the factors affecting the rate of chemical oxygen demand (COD) of a synthetic waste solution containing a water soluble basic dye [Methylene Blue] were investigated. Decolorization of the dye was achieved by ozonation. The research was conducted using a batch bubble column to take the advantage of the intensive back-mixing that prevails in bubble columns. As a result, the COD of basic dyestuff wastewater was reduced to 64.96% and decolorization was observed under basic conditions (pH 12), complete MB degradation occurring in 12 min. Ozone consumption continued for a further 16 min after which time most of the degradation reactions were complete. Kinetic studies showed that direct ozonation of the aqueous dyes represented a pseudo-first-order reaction with respect to the dye. The apparent rate constant, which increased with both the applied ozone dose and higher pH values, declined logarithmically with the initial dye concentration.     

超声化学法降解水中聚乙烯醇的研究

采用超声波辐射法降解聚乙烯醇(PVA)溶液,考察了初始浓度,反应温度,超声频率、溶解气体、pH值,添加氧化剂H2O2、盐和Fe2 等因素对降解效果的影响.结果表明,在超声频率40kHz、温度30℃,pH5.5和PVA初始浓度60 mg/L的条件下,140min时的降解率可达34%.外加Fe2、H2O2可明显提高PVA的降解率.气相色谱、红外光谱的检测结果证实降解过程中生成含C=O基团的中间化合物,最终PVA可完全矿化为CO2和H2O.     

APPLICATION OF SOME DOMESTIC WASTES AS NEW LOW-COST BIOSORBENTS FOR REMOVAL OF METHYLENE BLUE: KINETIC AND EQUILIBRIUM STUDIES

In this study, parsley stalks (PS), cucumber peels (CP), and watermelon seed hulls (WSH) were used as novel low-cost adsorbents to remove methylene blue (MB) from aqueous solutions. The biosorption of MB onto PS, CP, and WSH was investigated as a function of pH (2–10), initial dye concentration (25–450 mg/L), temperature (293–333 K), ionic strength (0.0–1.0 mol/L NaCl), and biosorbent dose (0.1–1.0 g/50 mL). While the biosorption of MB on PS followed the Freundlich isotherm, biosorption on CP and WSH followed the Langmuir isotherm at all the temperatures studied. The monolayer biosorption capacities of PS, CP, and WSH were found to be 400, 111.11, and 57.14 mg/g, respectively. The biosorption of MB onto PS followed pseudo-second-order kinetics, and the biosorption onto CP and WSH followed pseudo-first-order kinetics. Thermodynamic studies showed that the biosorption of MB onto PS, CP, and WSH was spontaneous and feasible. The pH_zpc values _of PS, CP, and WSH were found to be 6.26, 6.42, and 6.83, respectively. Desorption studies were also carried out with various desorbing agents. HCl and H₃PO₄ were more effective desorbents than other desorbents used.     

对硝基苯胺臭氧化反应动力学和吸收过程模拟

采用停流光谱法研究了T＝298 K,pH＝2.1～6范围内对硝基苯胺与臭氧在水溶液中的臭氧化反应动力学.研究结果表明,降解1 mol的对硝基苯胺需要4 mol臭氧,对硝基苯胺臭氧化总的反应是二级,对臭氧浓度和对硝基苯胺浓度分别为一级.臭氧化反应速率常数随溶液pH值的增大而加快:在T=298 K时,当pH值从2.1变化到6,总的反应速率常数从6.17×10⁴ (mol•L^-1)^-1•s^-1增大到1.55×10⁶(mol•L^-1)^-1•s^-1.为了验证其适用性,进行了臭氧在搅拌釜中在对硝基苯胺溶液中吸收过程的模拟.采用Matlab软件求解吸收过程的质量平衡方程,模拟了吸收过程中臭氧和对硝基苯胺浓度的变化,并与实验值进行了比较.结果表明,在80％的对硝基苯胺降解之前,模拟值和实验值能很好地一致.     

纳米二氧化锰的制备及其对亚甲基蓝的吸附研究

利用微乳液还原法,用甲苯还原KMnO4制得纳米MnO2。借助傅立叶红外光谱(FTIR)、扫描电镜(SEM)等手段对其结构性质进行了表征。通过吸附试验研究了溶液pH、煅烧温度、染料初始质量浓度对纳米MnO2吸附亚甲基蓝效果的影响。结果表明,所得纳米MnO2为球型颗粒,其粒径范围为50～80 nm,比表面积大,表面存在大量活性-OH基团,对亚甲基蓝有较强的吸附作用及较强的催化氧化降解能力;在酸性环境下,纳米MnO2对亚甲基蓝的去除能力随pH增大、煅烧温度的升高而呈现减弱趋势。pH=3时,未经煅烧的纳米MnO2对亚甲基蓝去除率高达98.4%,符合Langmuir模型。     

ANODIC REACTIONS OF PROPYLENE IN THE BROMIDE AQUEOUS SOLUTIONS

The formation of propylene oxide actually occurred in the homogeneous bromide aqueous solutions for the anodic oxidation of propylene. It was found that the selectivity was very high and the current yield was mainly affected by the pH values and the spaces between the electrodes. The effect of pH values on the distributions of different types of ions in the solution was also described.     

用空气代替臭氧处理微污染水

在O3＋GAC微污染水原水的深度处理工艺中,O3是一种强氧化剂,并能向水中提供溶解氧,有利于生物净化作用。当水中的COD。含量较低时,用空气代替臭氧可以得到同样的处理效果。     

改性蒙脱石吸附亚甲蓝的研究

取钠型蒙脱石和钙型蒙脱石,经铜离子交换反应使其改性。研究改性前后蒙脱石吸附亚甲蓝的能力及其受温度、介质pH值和离子强度的影响,并就吸附等温线和相关热力学参数进行分析。结果表明：不论是钠型还是钙型蒙脱石,经铜离子处理后,二者吸附亚甲蓝的能力均有所下降,但改性钠型蒙脱石下降的幅度要大于改性钙型蒙脱石;介质pH值和离子强度对蒙脱石和改性蒙脱石吸附性能的影响有差异,而吸附温度对各吸附剂吸附性能的影响程度则相近;改性蒙脱石和蒙脱石吸附亚甲蓝的等温线均能较好的符合BET和Langmuir等温方程,在298．15K下,其吸附过程均为热力学自发过程。     

SECONDARY NUCLEATION OF SUCROSE BY FLUID SHEAR IN AQUEOUS SOLUTIONS

The motivation for this work was based on two hypotheses: subcritical nuclei of sucrose may be generated by secondary nucleation using a fluid shear field acting on the surface of a growing seed crystal in aqueous solutions, and a near-dynamic equilibrium distribution of embryos may be attained. These were supported experimentally. The value of a σ-based model parameter, a, was obtained by describing the system by a Boltzman- like distribution model. The number concentration of subcritical nuclei was well described by the model. Despite differences in experimental method and in the basic nature of the solute, sucrose, the behavior of the system and results were similar to those obtained in the earlier work using aqueous salt solutions [Sung et al. (1973), Jagannathan et al. (1980)].     

SECONDARY NUCLEATION OF SUCROSE BY FLUID SHEAR IN AQUEOUS SOLUTIONS

The motivation for this work was based on two hypotheses: subcritical nuclei of sucrose may be generated by secondary nucleation using a fluid shear field acting on the surface of a growing seed crystal in aqueous solutions, and a near-dynamic equilibrium distribution of embryos may be attained. These were supported experimentally. The value of a σ-based model parameter, a, was obtained by describing the system by a Boltzman- like distribution model. The number concentration of subcritical nuclei was well described by the model. Despite differences in experimental method and in the basic nature of the solute, sucrose, the behavior of the system and results were similar to those obtained in the earlier work using aqueous salt solutions [Sung et al. (1973), Jagannathan et al. (1980)].     

水中邻苯二甲酸二甲酯的光催化氧化研究

以汞灯、氙灯为光源，TiO2为光催化荆，较系统的考察了催化剂用量、光强、反应时间、pH值等因素对水中邻苯二甲酸二甲酯降解的影响。结果表明，只有在催化剂和光源协同作用时，邻苯二甲酸二甲酯才可获得较快的分解，光催化氧化反应符合假一级反应动力学。TiO2的光催化氧化作用受pH值影响不大，催化剂用量有一最佳值。采用胶束电动毛细管电泳技术对邻苯二甲酸二甲酯的光催化降解反应过程进行了跟踪。     

OZONATION TREATMENT OF 2-NITROPHENOLIC WASTEWATER USING A NEW GAS-INDUCING REACTOR

Ozonation is a potential chemical process for the treatment of nitrophenolic wastewater. However, due to the low solubility and utilization rate of ozone, a conventional gas-inducing reactor for ozonation treatment has limited app-lication for treating phenolic wastewater. In this study, 2-nitrophenol wastewater ozonation was conducted in a new gas-inducing reactor that has been investigated in our laboratory over the past few years. The ozonation conducted in this reactor can be operated with a higher ozone utilization rate and lower power consumption than a conventional gas-liquid reactor. The ozone utilization rate increases with increasing pH value and can be maintained at over 95%. Kinetic studies show that a pseudo first-order reaction model derived from a two-film theory can describe the ozonation of 2-nitrophenol. Kinetic study of 2-nitrophenol ozonation shows that there are two stages in 2-nitrophenol ozonation. The observed rate constant in the second stage of 2-nitrophenol ozonation is higher than the first stage. A change in the 2-nitrophenol concentration is responsible for the change in the observed rate constant. Below pH 7, the oxidation rate of 2-nitrophenol increases with increasing pH and increasing ozone inlet concentration. This new gas-inducing reactor can improve the ozone utilization rate. The ozonation of 2-nitrophenol can be effectively conducted in this reactor.