Oxidation of Organic Pollutants of Water to Mineralization by Catalytic Ozonation

The oxidation of various organic compounds in aqueous solution was studied using catalytic ozonation (TOCCATA process) and conventional ozonation. The aim of the work is to assess catalytic ozonation efficiency for the mineralization of various organic compounds in order to envisage its application on real effluents. The selected organic compounds (about 30) are commonly found in industrial wastewaters. Comparative experiments were performed in batch mode at laboratory scale. Investigations were focused on ozone consumption rate, variations of total organic carbon, oxidation by-products and oxidation rate. Catalytic and conventional ozonation treatments were compared considering kinetic data, mineralization extent, and effect of organic functionalities. Catalytic ozonation system according to the TOCCATA process was able to convert organic compounds which were totally inert to ozone treatment and permitted considerably enhanced reaction rates when compounds were reactive to ozonation.     

污水出水有机物对臭氧氧化舒必利的影响

臭氧氧化可以有效去除诸如药物及个人护理品(PPCPs)等新兴有机污染物, 但去除效果受污水出水水质波动的影响。本研究选择了腐殖酸(HA)、牛血清蛋白(BSA)和海藻酸钠(AGS)3种典型有机物作为模型污水出水有机物(EfOM), 从降解速率和矿化程度两方面出发, 考察了EfOM对臭氧氧化去除一种常用抗精神病药物残留舒必利(SP)的影响。结果表明, 臭氧氧化能有效降低水溶液中SP的浓度, 在各反应条件下, 反应8min后去除率均可达85%以上。然而, 在研究条件下, 臭氧氧化对SP的矿化效果不佳, 反应25min后的TOC去除率小于10%。加入HA和BSA后, SP的臭氧氧化反应受到抑制, 随着HA和BSA浓度的增加, 臭氧氧化SP的反应速率逐渐降低, 反应溶液的矿化程度有所提高;而浓度为0~3.0mg/(L TOC)的AGS对臭氧氧化SP的影响较小。     

臭氧催化氧化机理及其技术研究进展

臭氧催化氧化技术可以提高污水中总有机碳（TOC）的去除效率和臭氧的利用率,近年来得到了广泛的研究。但由于催化反应过程复杂、影响因素多,导致其反应机理一直存在较大的争议。本文回顾了近年来国内外对臭氧催化氧化技术的研究结果,对均相、非均相臭氧催化氧化机理以及非均相催化剂的组成、活性影响因素进行了总结,并对非均相臭氧催化氧化技术用于降解模型化合物和处理典型工业污水的研究进展进行了介绍。文章最后指出催化剂的结构和表面化学性质与催化机理、有机物的降解途径之间的相互关系还需要更深入的研究。     

TiO2-Based Heterogeneous Photocatalytic Water Treatment Combined with Ozonation

The degradations of aliphatic carboxylic acids (formic acid, acetic acid, and propionic acid) were investigated by a combination of TiO₂-based photocatalysis and ozonation at pH = 2. The carboxylic acids were analyzed by high-performance liquid chromatography (HPLC), while the mineralization process was characterized by measuring the dissolved organic carbon (DOC) content. The efficiency of heterogeneous photocatalysis combined with ozonation was compared with that of ozonation and that of heterogeneous photocatalysis alone. In all cases, the combined system proved most effective in the oxidation of carboxylic acids. The degradation of carboxylic acids was accompanied by a continuous decrease in the DOC content, and aldehydes and carboxylic acids containing one carbon atom less than the starting material were formed as intermediates.     

Decomposition of hydrogen peroxide in the presence of activated carbons with different characteristics

BACKGROUND: Catalytic ozonation promoted by activated carbon is a promising advanced oxidation process used in water treatment. Hydrogen peroxide generated as a by‐product from the reaction of ozone with some surface groups on the activated carbon or from the oxidation of some organic compounds present in the water being treated seems to play a key role in the catalytic ozonation process. Hydrogen peroxide decomposition promoted by two granular activated carbons (GAC) of different characteristics (Hydraffin P110 and Chemviron SSP‐4) has been studied in a batch reactor. The operating variables investigated were the stirring speed, temperature, pH and particle size. Also, the influence of metals on the GAC surface, that can catalyze hydrogen peroxide decomposition, was observed. RESULTS: Chemviron SSP‐4 showed a higher activity to decompose hydrogen peroxide than HydraffinP110 (70 and 50% of hydrogen peroxide removed after 2 h process, respectively). Regardless of the activated carbon used, hydrogen peroxide decomposition was clearly controlled by the mass transfer, although temperature and pH conditions exerted a remarkable influence on the process. Catalytic ozonation in the presence of activated carbon and hydrogen peroxide greatly improved the mineralization of oxalic acid (a very recalcitrant target compound). About 70% TOC (total organic carbon) depletion was observed after 1 h reaction in this combined system, much higher than the mineralization achieved by the single processes used. CONCLUSIONS: Of the two activated carbons studied, Chemviron SSP‐4 with an acidic nature presented a higher activity to decompose hydrogen peroxide. However the influence of the operating variables was quite similar in both cases. Experiments carried out in the presence of tert‐butanol confirmed the appearance of radical species. A kinetic study indicated that the process was controlled by the internal mass transfer and the chemical reaction on the surface of the activated carbon. The catalytic activity of hydrogen peroxide in oxalic acid ozonation promoted by activated carbon (O₃/AC/H₂O₂) was also studied. The results revealed the synergetic activity of the system O₃/AC/H₂O₂ to remove oxalic acid. Copyright © 2010 Society of Chemical Industry     

不同形貌的纳米Mg(OH)2催化臭氧化降解甲硝唑

采用化学沉淀法分别以六水合氯化镁和取自察尔汗盐湖的天然水氯镁石为原料制备了不同形貌的纳米 Mg(OH)₂催化剂，通过扫描电子显微镜、X射线衍射、傅里叶变换红外光谱等手段对所合成的催化剂的表面形貌、晶体结构和表面官能团等性质进行了表征。将两种不同形貌的纳米Mg(OH)₂材料首次应用于催化臭氧化过程，研究了两种不同形貌的纳米Mg(OH)₂[Mg(OH)₂-1和Mg(OH)₂-2]催化剂对甲硝唑的降解和矿化能力。结果表明，在单独臭氧化过程中，反应10min时甲硝唑的降解和矿化效率均较低，分别为51.9%和17.4%，而在臭氧化系统中分别加入Mg(OH)₂-1和Mg(OH)₂-2，甲硝唑的去除效率和矿化效率均明显提高，且Mg(OH)₂-2的催化臭氧化性能要优于Mg(OH)₂-1。另外，单独臭氧化过程、Mg(OH)₂-1催化臭氧化以及Mg(OH)₂-2催化臭氧化过程中甲硝唑的降解均较好地符合伪一级动力学反应模型（R²>0.97）。除此之外，对这两种不同形貌的纳米Mg(OH)₂催化剂的稳定性进行了考察，结果表明，催化剂在循环使用六次后对甲硝唑仍有较高的催化臭氧化去除效率。因此，所合成的两种形貌的纳米Mg(OH)₂催化剂将是一种很有前景的、能用于去除抗生素的臭氧化催化剂。     

Peroxyl and hydroxyl radical scavenging activity of some natural phenolic antioxidants

The autoxidation of linoleic acid dispersed in an aqueous media and the antioxidant effect of hydroxytyrosol, oleuropein, caffeic acid and tyrosol were studied. Linoleic acid autoxidation rate was estimated by the increase of conjugated diene level and by the decrease of linoleic acid content in the samples. The phenolic compounds exhibited an antioxidant activity which increased in the order: tyrosol < caffeic acid < oleuropein < hydroxytyrosol. The analysis of the hydroperoxide isomers pointed out that hydroxytyrosol, oleuropein and caffeic acid at a concentration of 10⁻⁴M inhibited the formation oftrans- trans isomers in the increasing order: caffeic acid < oleuropein < hydroxytyrosol. This inhibition could be related to the ability of phenolic compounds to scavenge peroxyl radical. Tyrosol did not inhibit the formation oftranstrans isomers. Phenolic compounds were degraded as a consequence of their antioxidant activity and their degradation rate was positively correlated to their antioxidant efficacy. These phenolic compounds, at a concentration of 6 × 10⁻³M, also scavenged hydroxyl radical, with an efficiency which increased in the order: tyrosol < hydroxytyrosol < oleuropein < caffeic acid. Polar substituents at the para position, such as in caffeic acid and oleuropein, were correlated with higher hydroxyl radical quenching ability.     

O3 based advanced oxidation for ibuprofen degradation

The degradation of the anti-inflammatory ibuprofen (IBP) was evaluated by several advanced oxidation processes. IBP was treated by single ozonation and oxidation with hydrogen peroxide (H₂O₂), as well as a combination of these treatments. In order to improve the efficiency, the presence of catalysts such as original carbon nanotubes, labelled as CNT, and iron oxide supported on carbon nanotubes, named as Fe/CNT sample, was considered. The evolution of IBP degradation, mineralization and toxicity of the solutions was assessed. The formation of intermediates was also monitored. In the non-catalytic processes, IBP was faster removed by single ozonation, whereas no significant total organic carbon (TOC) removal was achieved. Oxidation with H₂O₂ did not present satisfactory results. When ozone and H₂O₂ were combined, a higher mineralization was attained (70% after 180 min of reaction). On the other hand, in the catalytic processes, this combined process allowed the fastest IBP degradation. In terms of mineralization degree, the presence of Fe/CNT increases the removal rate in the first hour of reaction, achieving a TOC removal of 85%. Four compounds were detected as by-products. All treated solutions presented lower toxicity than the initial solution, suggesting that the released intermediates during applied processes are less toxic.     

Toxicity Assay in Kraft E1 Effluent Treated by Ozone: Algae Growth Inhibition and Cytotoxicity in V79 Cells

The efficiency of an ozonation process in the degradation of the Kraft E₁ effluent was evaluated. The investigation was focused on the reduction of chemical oxygen demand, total phenols, color and the absorbance at 254 nm. The chronic toxicity was evaluated by growth inhibition of algae Selenatrum capricornutum and cytotoxicity evaluation of effluents samples by determination of the nucleic acid content (NCA) endpoint. After 60 minutes of ozonation, COD and UV₂₅₄ only reached 21% and 34% efficiency reduction. Total phenols and color were more rapidly removed (at 10 minutes of treatment). The results showed that the chronic toxicity (Selenastrum capricornutum algae) decreases for all effluent doses studied. The cytotoxicity assay indicated that toxic compounds were not generated by the ozonation process.     

Impact of Ozonation on Decolorization and Mineralization of Azo Dyes: Biodegradability Enhancement,By-Products Formation,Required Energy and Cost

In the present study ozonation process was implemented to analyze the effect of ozonation time on the rate of chemical oxygen demand (COD) removal, mineralization and rate of decolorization of azo dyes. Three types of azo dyes i.e. Acid Red 14, Direct Red 28 and Reactive Black 5 were selected. Decolorization and mineralization of samples were conducted in batch scale. The COD and color removal efficiency were found to be increasing at a certain time of ozonation. The results with Acid Red 14, Congo Red and Reactive Black 5 dyes solutions lead to maximum COD reduction of 75%, 67% & 50% respectively. 93%, 92% and 94% color removal were achieved after 25 min of ozonation time of the same dyes which highlighted that ozonation process was found to be more efficient for reactive dye decolorization. Ozonation by-products analyzed by ion chromatography resulted that it partially mineralized with the formation of chloride, fluoride, sulphate, nitrate and oxalate ions. During ozonation process a rapid decrease in pH value indicated the acidic nature of by-products. The effect of buffered dye solutions on the ozonoation process highlighted that the decolorization efficiency decreases in comparison to unbuffered dye solutions. Ozonation led to enhancement of biodegradability ratio (BOD₅/COD) and increased electrical conductivity of the dye solutions. Optimum ozonation time required for degradation of dye solutions reflected the evaluation of energy consumption and cost of the treatment after ozonation.     

Enhancement in mineralization of some natural refractory organic compounds by ozonation–aerobic biodegradation

Two schemes, the first involving ozonation followed by final aerobic biodegradation (phase I experiments), and the second involving initial aerobic biodegradation, followed by ozonation and subsequent final aerobic biodegradation (phase II experiments), were examined for enhanced mineralization of refractory model compounds, viz. gallic acid, tannin and lignin. In all cases, and irrespective of the applied scheme, chemical oxygen demand (COD), total organic carbon (TOC), COD/TOC ratio, and specific UV absorbance at 280 nm attributed to the model compounds decreased with application of increasing ozone dose. The residual organic matter remaining after ozonation exhibited enhanced aerobic biodegradability in all cases. Further, in all cases and irrespective of the applied scheme, the overall amount of COD and TOC removed through the combination of ozonation and biodegradation processes increased with increase in ozone dose for all three model compounds, and more than 90% COD removal could be achieved with an ozone dose of 3 mg ozone absorbed per mg initial TOC, as compared with approximately 40% COD removal when no ozone was applied. Treatment by the first scheme resulted in the fraction of starting COD removed through biodegradation decreasing with increase in ozone dose in all cases, while this fraction increased or remained constant during treatment using the second scheme. In the case of tannin and lignin, similar overall COD removal could be achieved at lower ozone doses using scheme II. Due to incorporation of the initial aerobic biodegradation step in scheme II, the ozone requirement for additional mineralization, ie mineralization over and above that achieved by aerobic biodegradation, was also lower than that in scheme I. Copyright © 2005 Society of Chemical Industry     

Sequential Oxidation of Humic Acids by Ozonation and Photocatalysis

In this study, humic acids, the natural polymerized organic compounds which are responsible for the formation of disinfection by-products such as haloacetic acids and trihalomethanes upon chlorination, are oxidized in a sequential system incorporating ozonation and photocatalysis. Titanium dioxide is used as photocatalyst in the photocatalytic oxidation phase. Humic acid degradation kinetics is evaluated both for ozonation and photocatalysis. The Freundlich adsorption model is used for defining the adsorption characteristics of humic acid solutions on the photocatalyst after the ozonation step. The Langmuir-Hinshelwood model is also studied for explaining the adsorptive and photocatalytic removal of humic acids.     

畜禽废水中磺胺嘧啶的臭氧氧化特性及机理

察了臭氧对畜禽废水中磺胺嘧啶(SD)的氧化特性,研究了溶液pH、阴离子以及腐殖酸对SD氧化效果的影响。结果表明,臭氧氧化SD符合拟一级表观动力学方程,pH增大有利于SD的氧化;阴离子与腐殖酸对臭氧氧化SD具有抑制作用,且NO3^->Cl^->SO4^2-。O3和HO^-均对臭氧氧化SD具有重要作用,酸性条件下以O3氧化为主,碱性条件下以HO^-氧化为主。臭氧氧化法去除实际畜禽废水中SD的速率低于模拟废水,10 min时实际畜禽废水中SD去除率为55.7%。LC-MS/MS分析确定了SD降解中间产物,推测了其降解途径并评估了各中间产物的生态毒性。     

Effect of Eleven Antioxidants in Inhibiting Thermal Oxidation of Cholesterol

Eleven antioxidants including nine phenolic compounds (rutin, quercetin, hesperidin, hesperetin, naringin, naringenin, chlorogenic acid, caffeic acid, ferulic acid), vitamin E (α‐tocopherol), and butylated hydroxytoluene (BHT) were selected to investigate their inhibitory effects on thermal oxidation of cholesterol in air and lard. The results indicated that the unoxidized cholesterol decreased with heating time whilst cholesterol oxidation products (COPs) increased with heating time. The major COPs produced were 7α‐hydroxycholesterol, 7β‐hydroxycholesterol, 5,6β‐epoxycholesterol, 5,6α‐epoxycholesterol, and 7‐ketocholesterol. When cholesterol was heated in air for an hour, rutin, quercetin, chlorogenic acid, and caffeic acid showed a strong inhibitory effect. When cholesterol was heated in lard, caffeic acid, quercetin, and chlorogenic acid demonstrated inhibitory action during the initial 0.5 h (p < 0.05), with caffeic acid being the best inhibitor. Hesperetin, naringenin, caffeic acid, ferulic acid, vitamin E, and BHT could decrease the peroxide value during the initial 0.5 and 1 h (p < 0.05) in lard. It seemed that 200 ppm antioxidant could not obviously retard the long‐term oxidation of cholesterol and lard under high temperature, but caffeic acid, quercetin, and chlorogenic acid displayed great untapped potential to prevent thermal oxidation of cholesterol 0.5 h at least. For the sake of health and flavor, fast stir‐frying over a high flame is recommended. If baking or deep fat frying food in oil, it is best to limit cooking time to within 0.5 h.     

Gallic acid water ozonation using activated carbon

The ozonation of gallic acid in water in the presence of activated carbon has been studied at pH 5. Hydrogen peroxide, ketomalonic and oxalic acids were identified as by-products. The process involves two main periods of reaction. The first period, up to complete disappearance of gallic acid, during which ozonation rates are slightly improved by the presence of activated carbon. The second one, during which activated carbon plays an important role as promoter, and total mineralization of the organic content of the water is achieved. The organic matter removal is due to the sum of contributions of ozone direct reactions and adsorption during the first period and to a free radical mechanism likely involving surface reactions of ozone and hydrogen peroxide on the carbon surface during the second period. There is a third transition period where by-products concentration reach maximum values and ozonation is likely due to both direct and free radical mechanisms involving ozone and adsorption. Discussion on the mechanism and kinetics of the process is also presented both for single ozonation and activated carbon ozonation.     

Ozonation Enhancement with Nonpolar Bonded Alumina Phases

This article presents the results obtained for humic acid (HA) degradation in drinking water by means of an ozonation process in the presence of a nonpolar bonded alumina phase. It was observed that (perflurooctylalumina) (PFOA) is characterized by its high adsorption capacity toward HA. The adsorption properties of bare alumina and alumina modified with perfluorooctanoic acid appeared to differ significantly toward the various organic substances examined. The ozonation process carried out in the presence of PFOA was found to be more efficient for the removal of HA from water than the other two examined ozonation systems: ozonation alone and ozonation in the presence of bare alumina; however, a catalytic activity of bare alumina cannot be denied. The effect of by-products formation and changes in the molecular size distribution of HA were studied in the case of all three examined ozonation systems. The influence of catalyst dosage and ozonation time was also investigated.     

Ozonation of sulfamethoxazole promoted by MWCNT

Multi-walled carbon nanotubes (MWCNTs) with different surface chemical properties were prepared by oxidative and thermal treatments. Samples were characterized by nitrogen adsorption, temperature programmed desorption and pH at the point of zero charge. These catalysts were tested in the ozonation of sulfamethoxazole. Complete conversion of this compound was achieved after approximately 30 min. MWCNTs significantly enhanced the mineralization degree compared to single ozonation. Some oxidation products were quantified. The catalytic process is favored by MWCNTs with basic or neutral properties. Successive experimental runs of SMX degradation show that the catalysts suffer some deactivation.     

Effect of ozonation pretreatment on the surface properties and catalytic activity of multi-walled carbon nanotube

Multi-walled carbon nanotube (MWCNT) has been used in the catalytic ozonation of oxalic acid in aqueous solution, which was pretreated using ozone and was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption and Boehm titration. The effect of ozonation pretreatment on the catalytic activity of MWCNT and the ozonation mechanism of oxalic acid in the presence of MWCNT were investigated. The results indicate that with the increasing pretreatment time, the atom ratio of oxygen to carbon and the number of surface acid groups on MWCNT increase, while the catalytic activity of MWCNT on ozonation of oxalic acid decreases, suggesting that the chemical characteristics of MWCNT mainly determine its catalytic activity on oxalic acid mineralization. The inhibition of tert-butyl alcohol on the degradation of oxalic acid is slight for pristine MWCNT catalytic ozonation and this inhibition trend becomes more obvious when MWCNT was pretreated by ozone. A free radical mechanism was proposed which involves both surface reactions and bulk reactions between the oxalic acid and active species.     

Ozonation of Phenol-Containing Wastewater Using O3/Ca(OH)2 System in a Micro Bubble Gas-Liquid Reactor

The degradation of phenol in aqueous solution was investigated in an integrated process consisting of O₃/Ca(OH)₂ system and a newly developed micro bubble gas-liquid reactor. The effects of operating parameters such as Ca(OH)₂ dosage, reactor pressure, liquid phase temperature, initial phenol concentration and inlet ozone concentration on degradation and mineralization (TOC removal) were studied in order to know the ozonation performance of this new integrated process. It is demonstrated that the degradation and TOC removal efficiency increased with increasing inlet ozone concentration and increasing Ca(OH)₂ dosage before 2 g/L, as well as decreasing initial phenol concentration. The optimum Ca(OH)₂ dosage should exceed Ca(OH)₂ solubility in liquid phase. The reactor pressure and liquid phase temperature have little effects on the removal and TOC removal efficiency. When Ca(OH)₂ dosage exceeded 3 g/L, the degradation and TOC removal of phenol almost reached 100% at 30 and 55 min, respectively. The intensification mechanism of Ca(OH)₂ assisted ozonation was explored through analysis of the precipitated substances. The mechanism for Ca(OH)₂ intensified mineralization of phenol solution is the simultaneous removal of CO₃^2- ions, as hydroxyl radical scavengers, due to the presence of Ca²⁺ ions. Results indicated that the proposed new integrated process is a highly efficient ozonation process for persistent organic wastewater treatment.     

Degradation of Acid Black 210 by advanced oxidative processes: O3 and O3/UV

Acid Black 210 (AB-210) dye is one of the most black dyes used by the leather industry. In the present work, AB-210 degradation in aqueous solution by ozonation (O₃) and ozonation with ultraviolet (UV) radiation (O₃/UV) was investigated. The effects of pH, initial dye concentration and UV radiation were studied in laboratory scale. Removal was evaluated in terms of residual AB-210 concentration in the treated solution and mineralization efficiency was evaluated by total organic carbon (TOC) analysis. The results indicated that AB-210 is quickly degraded after 15 min but not totally mineralized. It was observed that dye removal of 100% was achieved at pH 3, 7, and 11, while mineralization was found to increase with the pH (55% at pH 11). Concerning UV-C radiation, it enhanced AB-210 degradation at pH 3 but did not reveal any significant effect at pH 7 and 11.