Kinetic investigation of an azo dye oxidation by hydrogen peroxide in aqueous surfactant solution

In this study, the oxidation of resorcinol based an azo dye, 5-methyl-4-(2-thiazolylazo)resorcinol (5-Me-TAR) by hydrogen peroxide has been investigated from kinetic, spectroscopic and thermodynamic point of view to examine the influence of a cationic surfactant such as cetylpyridiniumchloride (CPC). Activation energy (298.15–313.15 K) and entropy (298.15 K) of the reaction were calculated as 67 kJ/mol and −72 J mol⁻¹ K⁻¹ in borate buffer, respectively. However, the addition of CPC into 5-Me-TAR solutions at different pH values always reduced the intensity of its azo form, the intensity of its hydrazone form increased. The oxidation of dye proceeds via perhydroxyl anion and hydrazone tautomeric form and oxidation rate was accelerated by the presence of CPC either in micellar or premicellar regions.     

Electroreduction of peroxycitric acid coexisting with hydrogen peroxide in aqueous solution

The electrochemical reduction of peroxycitric acid (PCA) coexisting with citric acid and hydrogen peroxide (H₂O₂) in the equilibrium mixture was extensively studied at a gold electrode in acetate buffer solutions containing 0.1 M Na₂SO₄ (pH 2.0-6.0) using cyclic and hydrodynamic voltammetric, and hydrodynamic chronocoulometric measurements. The reduction of PCA was characterized to be an irreversible, diffusion-controlled process, and the cyclic voltammetric reduction peak potential () was found to be more positive by ca. 1.0 V than that of the coexisting H₂O₂, e.g., the values obtained at 0.1 V s⁻¹ for PCA and H₂O₂ were 0.35 and −0.35 V, respectively, vs. Ag|AgCl|KCl (sat.) at pH 3.3. The of PCA was found to depend on pH, i.e., at pH > 4.5, the plot of vs. pH gave the slope (−64 mV decade⁻¹) which is close to the theoretical value (−59 mV decade⁻¹) for an electrode process involving the equal number of electron and proton in the rate-determining step, while at pH < 4.5, the was almost independent of pH. The relevant electrochemical parameters, Tafel slope, number of electrons, formal potential (E⁰′), cathodic transfer coefficient and standard heterogeneous rate constant (k⁰′) for the reduction of PCA and the diffusion coefficient of PCA were determined to be ca. 100 mV decade⁻¹, 2, 1.53 V (at pH 2.6), 0.29, 1.2 × 10⁻¹² cm s⁻¹ and 0.29 × 10⁻⁵ cm² s⁻¹, respectively, and except for E⁰′, the obtained values were almost independent of the solution pH. The overall mechanism of the reduction of PCA was discussed.     

双氧水氧化工艺安全研究策略

国内双氧水绿色氧化工艺蓬勃发展,但工艺本身危险性较高且发生过多起安全事故,严重阻碍了新工艺的开发和推广。为完善工艺安全研究、促进工艺开发,将工艺流程划分为双氧水储存系统、物料进料系统、反应系统、精馏系统等单元,对系统单元涉及的安全问题进行了阐述,总结和探讨了现有研究方法和研究成果。通过对全流程的双氧水氧化工艺中的安全问题和安全研究思路进行梳理分析,为相关工艺开发应用单位建立系统化的安全研究方法和策略、全面提升工艺安全提供建议和参考。     

Cu-silicalite-1 catalyst for the wet hydrogen peroxide oxidation of phenol

The aim of the present work is to study the heterogeneous wet hydrogen peroxide catalytic oxidation (WHPCO) of phenol using copper bearing Silicalite-1 type zeolite, prepared by direct hydrothermal synthesis. The catalysts used for this study were three: one (Na)Cu-Silicalite-1 and two (H)Cu-Silicalite-1 prepared by different ion exchange methods. The results on catalytic activity for phenol abatement and hydrogen peroxide consumption of these materials are presented. The copper leaching during the reaction was evaluated for all samples. A comparison with the catalytic activity and stability of a Cu-Silicalite-1 material prepared by ionic exchange method is presented.     

Biotreatability enhancement of aqueous Reactive Black 5 by hydrogen peroxide/ultraviolet advanced oxidation process

The efficiency of ultraviolet/hydrogen peroxide photo‐oxidation processing for enhancing the biodegradability of Reactive Black 5 prior to biological treatment processing of acclimated and non‐acclimated sequencing batch reactors was evaluated. Photo‐oxidation experiments were conducted according to an experimental design method in which aqueous Reactive Black 5 samples with an initial concentration of 200 mg/l were exposed to ultraviolet irradiation for 15, 30 and 60 min in the presence of various concentrations of hydrogen peroxide (250, 500 and 1000 mg/l) at pH 7. Pretreated samples were then subjected to respirometric biodegradability tests using the sludge cultures obtained from acclimated and non‐acclimated sequencing batch reactors for the determination of the kinetic constants of q_max and K_s according to the modified Organisation of Economic Cooperation and Development 209 method. Calculated values of q_max and K_s showed that the acclimated sludge of the sequencing batch reactor showed a better performance than the non‐acclimated sludge in the degradation of photochemically pretreated aqueous Reactive Black 5. The advantage of acclimated sludge compared with non‐acclimated sludge for the biodegradation of Reactive Black 5 diminished when photochemical pretreatment conditions reached higher levels in terms of oxidation time and hydrogen peroxide concentration.     

微波强化臭氧氧化降解苯酚水溶液

The degradation of phenol in aqueous solution with the combination of microwave and ozone（MW/O₃）was studied with laboratory-scale experiments.Effects of ozone dose,pH value,initial phenol concentration and reaction temperature on the reaction kinetics were investigated.In all cases,the degradation of phenol follows a pseudo-first-order kinetics relation.MW/O₃ combined technology is favorable for enhancing the removal efficiency of phenol,with the enhancement factor of the first-order kinetics constant being around 3.6.Experimental results showed that the synergetic effect of MW/O3 combined technology was obvious and up to 99 % of phenol was removed after 30 min reaction with initial phenol concentration of 100 mg·L^-1,ozone dose of 1.1 mg·min^-1,pH value of 9—11,and reaction temperature of 25℃.     

Oxidation of phenol by aqueous hydrogen peroxide catalysed by ferric ion-catechol complexes

Phenol has been oxidised with aqueous hydrogen peroxide under a wide variety of conditions and yields of the catechol and hydroquinone products recorded. Catalysts tested included a number of transition metal and related ions of which only Cu⁺, Cu²⁺, Cr³⁺, WO₄^2-, Hg²⁺, Fe²⁺, and Fe³⁺ gave any degree of success. Extensive tests with ferric ion established 2.5:1000, Fe³⁺:phenol mole ratio as being the optimum catalytic range. Temperatures lower than 30°C gave relatively high catechol:hydroquinone product ratios, about 1.9:1, but lowered the yields of dihydroxybenzenes to about 70% of theory. From experiments conducted over the pH range of 1 to 8 the optimum pH for high yield reactions was found to be 2 to 3. Operating at a hydrogen peroxide:phenol mole ratio of 0.30:1.0 gave the highest catechol:hydroquinone product ratios, 1.6:1.0. The catechol:hydroquinone ratio produced decreased as the ratio of reacting peroxide to phenol was increased. Optimised conditions gave dihydroxybenzene yields of 84 and 53% on phenol and hydrogen peroxide respectively, and ratios of 1.5:1 and 2.0:1, catechol:hydroquinone. A research stage economic summary from averaged pairs of experimental results gave a value added of $3.19 (technical grade products) or $8.47 (pure grades) per kg of catechol on a raw material cost base of $2.87, as two among four calculated cost evaluation scenarios.     

过氧化氢氧化法制偶氮二甲酰胺工艺的研究

采用过氧化氢(含量50%以上)为氧化剂,以溴化钠为主催化剂、铁基物质为助催化剂氧化联二脲制偶氮二甲酰胺产品,工艺操作简单,且反应母液循环套用,减少三废排放,达到清洁文明生产效果。     

过氧化氢氧化苯酚铜锰复合氧化物催化剂的制备

采用固相法制备了新型催化剂铜锰复合氧化物催化剂。利用高效液相色谱法对苯酚过氧化氢氧化反应产物进行分析,以苯酚转化率和苯二酚收率为评价指标,对催化剂进行了评价。结果表明,催化剂性能随铜与锰物质的量比、焙烧温度、焙烧时间和研磨时间等因素的增大呈先升高再降低的趋势,并与络合剂的还原性有关。确定最佳工艺条件为:室温下,按锰与铜物质的量比1:2将Cu_2(OH)_2CO_3、MnCO_3和适量H_2C_2O_4·2H_2O混匀,置于研钵匀速研磨10 min,马弗炉400℃焙烧2 h。最佳条件下,苯酚转化率为63.7%,苯二酚收率为59.1%。     

双氧水氧化一步法合成TMTD

以二甲胺、二硫化碳为原料，异丙醇作溶剂，在不使用强酸、强碱及其他催化剂的条件下，采用双氧水氧化一步法合成了TMTD。并对合成工艺进行了优化，最佳反应条件为：反应温度为20℃，二硫化碳与二甲胺的摩尔比为1：1．2，二硫化碳与溶剂的重量比为1：16。优化条件下的产物收率可达96．7％。     

电子级过氧化氢水溶液制备技术进展

简要介绍了电子工业用高纯过氧化氢水溶液的应用、现状和杂质来源。综述了通过吸附、离子交换、膜分离、精馏、萃取和结晶等单一单元操作纯化制备高纯过氧化氢水溶液技术,并进行优劣势比较。指出当前高纯过氧化氢水溶液制备技术的发展趋势是单元操作集成,重点介绍了使用较为广泛的"吸附–离子交换–膜分离单元操作集成技术"制备高纯过氧化氢水溶液的工艺。     

Metronidazole photodegradation in aqueous solution by using photosensitizers and hydrogen peroxide

BACKGROUND: The effectiveness of UV radiation on the indirect photodegradation of metronidazole (MNZ) conducting a kinetic study of the process in the presence of radical promoter (H₂O₂) and photosensitizer (Sens) promoters (duroquinone, tetrahydroxyquinone, tetrachloro‐1,4‐benzoquinone, 4‐carboxy‐benzophenone, 2,4‐dihydroxybenzophenone, 4‐hydroxybenzophenone, and 4,4′‐dihydroxybenzophenone) was investigated. RESULTS: The electron‐donating groups of photosensitizers may favor MNZ photodegradation through electron transfer. However, the photosensitizers studied showed low effectiveness of MNZ photodegradation in aqueous phase. The presence of H₂O₂ substantially increased MNZ photodegradation rate, which was enhanced by increasing the concentration of hydrogen peroxide in the system. The contribution of direct photolysis of MNZ in the UV/H₂O₂ system was drastically decreased with increasing H₂O₂ concentrations. CONCLUSIONS: The low effectiveness obtained with most of the Sens used demonstrates that metronidazole cannot be photoxidized by indirect photooxidation in aqueous solution. Copyright © 2012 Society of Chemical Industry     

过氧化氢氧化苯制苯酚的催化剂研究进展

综述了过氧化氢直接氧化苯制苯酚过程中相关催化剂的研究进展,重点介绍了含钛、钒、铁、铜的催化剂,同时给出了各种催化剂所达到的收率和选择性及其工业化前景。     

苯一步法制苯酚反应中TS-1催化剂失活研究

考察了TS-1催化剂在过氧化氢氧化苯一步法制苯酚反应中的催化效果,研究表明在反应初期TS-1具有较高的反应活性,但易失活;采用XRD、SEM、微结构分析、TG-DTA多种方法分析反应前后TS-1的性质,表明反应前后其骨架结构未发生变化,失活催化剂晶型晶貌未发生明显改变,在TG由线中320℃附近有失重;失活催化荆可通过焙烧再生,其活性基本得到恢复,表明反应中催化剂的失活是由羽产物积碳所导致的暂时性失活.     

臭氧-过氧化氢氧化预处理H酸废水

采用工业生产中排放的H酸废水作为研究对象,探讨了臭氧-H2O2氧化的预处理方法对该废水的处理效果。结果表明：在单独臭氧氧化反应体系中,初始CODCr的质量浓度为1 200 mg/L,pH值为7,臭氧氧化时间在20 min（通量为1 L/min）时,CODCr和色度去除率分别为36.7%和95%。单独H2O2氧化反应体系中,H2O2投加量为8 mL/L时,CODCr去除率为7.7%,H2O2投加量达到60 mL/L时,CODCr去除率最高仅达到25.6%。臭氧-H2O2联用体系中,相同初始CODCr浓度、pH值、臭氧氧化时间及臭氧通量条件下,质量分数为3%的H2O2溶液投加量为8 mL/L时,CODCr和色度去除率分别可达48.8%和98%。因此,臭氧-H2O2氧化的预处理方法对H酸废水降解效果良好,且明显优于单独臭氧氧化以及单独H2O2氧化。     

2，4-二氯苯氧乙酸臭氧化过程中过氧化氢的生成

引言2,4-二氯苯氧乙酸(2,4-D,又名2,4-滴)是一种广泛使用的除草剂[1],应用历史较长,是我国主要的除草剂品种之一,用量也比较大。2,4-D属于苯氧羧酸类除草剂的一种,可有效去除阔叶杂草,目前仍广泛用于农作物除草和草坪养护[2]。2,4-D的水溶性较高,挥发性较低,在自然界中难以生物     

电位滴定法测定过氧化氢溶液中的过氧化氢含量

利用自动电位滴定仪测定过氧化氢溶液中的过氧化氢含量,研究了仪器的最佳操作条件及方法的准确度和精密度.结果表明:采用电位滴定法,在自动电位滴定仪自动找终点、等量滴定及搅拌速率为8 r/s的条件下测定过氧化氢溶液中的过氧化氢含量,其相对误差为0.10％,相对标准偏差为0.39％,测定1个试样耗时为683 s左右;在电位滴定...     

Oxidation of phenol in aqueous solution with copper catalysts

The oxidation of phenol in aqueous phase over four different catalysts based on copper has been studied in a basket stirred tank reactor. Runs have been carried out at 140°C and 16 bar of oxygen pressure, with a catalyst loading of 60 g/l and at an initial acidic pH. Phenol, total organic carbon and some intermediates have been measured with the reaction time. The improvement achieved with the catalyst is established by comparison with a blank (reaction without catalyst). The commercial catalyst Engelhard Cu-0203T (CuO, 67–77%, Cu chromite, 20–30%, graphite sint., 1–3%) was found to be the most active catalyst with an acceptable mechanical and chemical stability. Copper leaches from the catalyst are higher when the mineralization of the acid intermediates does not occur (lower values of pH are obtained).     

Catalytic oxidation of phenol in aqueous solutions

The objective of this work is to investigate catalyst systems for the oxidation of phenol in water in a batch autoclave. The main experimental variables are the type and the composition of the catalyst, the catalyst loading, temperature, oxygen partial pressure, initial phenol concentration and the stirrer speed. Commercial catalysts were used. Experimental work was conducted in two different laboratories. In one laboratory, the catalysts tested were 35% CuO+65% ZnO; 5–15% CuO+85–95% Al₂O₃; 26% CuO+74% Cu Chromite. In the other laboratory, the catalysts tested included 35% CuO+65% ZnO; 5–10% Ba₂CO₃+<5% C+30–40% CuO+60–70% ZnO; and 8–15% Al₂O₃+1–5% C+35–45% CuO+40–50% ZnO. With some of these catalysts depending on the operating conditions, complete phenol conversion could be obtained within 90 min. Under certain experimental conditions, the reaction underwent an induction period after which there was a transition to a much higher activity regime. The induction period may be due to an autocatalytic reaction system or to a very slow rate of formation of hydroquinone and catechol which then readily oxidize to o- and p-benzoquinone. An increase in the temperature and the oxygen partial pressure decreased the induction period, which increased as the catalyst to phenol ratio increased. 26% CuO+74% Cu Chromite and 8–15% Al₂O₃+1–5% C+35–45% CuO+40–50% ZnO were found to be the most active catalysts.     

Wet oxidation of phenol by hydrogen peroxide using heterogeneous catalysis Fe-ZSM-5: a promising catalyst

This letter presents an original approach to the treatment of phenolic aqueous wastes using H₂O₂ with heterogeneous catalysts. The experimental results indicate that the system using Fe-ZSM-5 zeolite with MFI structure is promising since it allows total elimination of phenol and significant total organic carbon (TOC) removal under mild working conditions. Moreover, Fe-ZSM-5 remains active after after successive runs. Compared with processes using homogeneous catalysis, the possibility of induced pollution caused by the metal ions in the solution is avoided.