多壁碳纳米管的氨表面改性及其臭氧催化降解草酸

采用水热方法制备了一系列用浓氨水改性的多壁碳纳米管催化剂,该催化剂的活性通过非均相催化臭氧化降解水溶液中的草酸来进行评价。降解过程符合零级反应动力学模型,且催化剂的表观动力学常数与其表面碱性基团数量以及零电位pH值（pHPZC）呈正相关。为此,可断定用浓氨在水热条件下处理多壁碳纳米管能明显提高催化臭氧降解草酸能力是因为提高了催化剂的表面碱性基团数量和pHPZC。     

改性活性炭吸附重金属镉的技术与机理

镉污染对饮用水安全造成了严重的威胁。活性炭吸附是水处理中最重要的处理方法之一,但是对镉等重金属的吸附较弱,通过改性可以改变活性炭的表面特性,从而促进对重金属的吸附。该文对活性炭进行了混酸氧化改性,臭氧氧化改性和乙二胺氨基化的改性,零电荷点和表面官能团大大发生变化,混酸改性后的零电荷点最低。通过吸附动力学的研究发现混酸改性的活性炭（Ac-0）对镉的吸附效果最好,且更加符合二级动力学的吸附模型。对AC-0活性炭进行了不同pH下吸附热力学的研究,结果表明吸附等温线用Freundlich的热力学模型拟合比较好,并且pH越大越有利于镉的吸附,pH对Ac-O吸附镉效果的影响试验也表明,由于零电荷点的影响,在pH小于9的情况下,随着pH的升高静电吸引力越强。     

乙二胺改性制备碱性活性炭的结构与性能特征

利用硝酸对粉末活性炭进行氧化,氯化亚砜酰氯化后,再与乙二胺反直进行表面改性。乙二胺改性活性炭表面特性用滴定分析、比表面及孔结构测定、FT-IR光谱、TG-DTG和催化探针等手段进行表征。结果表明,硝酸氧化后活性炭表面引入了更多的羧基;用乙二胺胺化处理在活性炭表面接枝上了一些含氮官能团,且表面具有一定的碱性,酸碱滴定其碱量为0.83 mmol/g。发现胺化活性炭可以用作丙酮液相Aldol缩合反应催化剂,其催化性能与强碱性大孔树脂D201相当。     

有机/无机酸改性兰炭基活性炭及其对焦化废水的吸附研究

兰炭因其固定碳和化学活性高,且保留了低变质煤丰富的微孔结构,是一种优质且廉价的活性炭原料。但兰炭末制成的兰炭基活性炭具有孔径分布无序、表面化学性质局限等缺点,限制了其应用效果,而化学法改性可以弥补这一不足。笔者研究对比了无机酸和有机酸改性对兰炭基活性炭孔隙结构和表面化学性质的影响。常温下,分别用硝酸、磷酸、草酸和乙酸溶液对水蒸气活化制备的兰炭基活性炭进行改性,采用碘吸附试验、N2吸附/脱附试验、扫描电子显微镜和Boehm滴定等方法考察改性过程对活性炭孔隙结构和表面化学性质的影响,并对焦化废水进行吸附,分别研究了吸附剂投加量、吸附时间和转速对吸附效果的影响,用Langmuir和Freundlich模型模拟等温吸附过程。结果表明:改性后的兰炭基活性炭表面亲和力大的活性点由于受到酸的刻蚀发生了扩孔作用,导致其碘吸附值、比表面积和孔结构参数均降低,又因为活性炭边缘的高活性碳原子遇酸氧化后会结合氧原子形成含氧官能团,故表面含氧官能团含量升高,且氧化性越强的酸,结合的氧原子越多,硝酸改性后含氧官能团升高最明显,含量是改性前的2.41倍。焦化废水吸附试验表明,经酸改性后的兰炭基活性炭对焦化废水的吸附效果明显优于改性前,其中无机酸改性较有机酸更好,硝酸改性效果最佳,COD去除率比改性前最多可提升31.34%。这是因为焦化废水中污染物的主要是有较大分子量和分子直径的有机污染物,而酸改性使兰炭基活性炭平均孔径增加,中大孔比例提升,这有利于大分子有机污染物被吸附,而且改性后活性炭表面所增加的含氧官能团也提高了对污染物的亲水性和对极性有机物的亲和力。等温吸附试验表明,318 K条件下,50 m L焦化废水中加入4 g硝酸改性兰炭基活性炭吸附90 min后,COD去除率可达86.79%,吸附过程符合Langmuir模型。     

羟基化锌催化臭氧化水中痕量p-CNB的动力学和机理

以实验室制备的羟基化锌(ZnOOH)为催化剂,探讨了其催化水中臭氧分解和降解水中痕量对氯硝基苯(p-CNB)的途径,并通过ESR实验验证了自由基反应机理。结果表明:ZnOOH可促进水中臭氧分解,使其一级分解速率常数提高了187%。反应20 min时,O3/ZnOOH对p-CNB的去除可以达到96.1%,比单独O3提高了1倍多。ZnOOH催化臭氧分解过程中促进了羟基自由基生成,用叔丁醇捕获生成的羟基自由基后,ZnOOH催化臭氧氧化p-CNB的反应速率常数降低了至少10倍。催化剂表面羟基含量与催化臭氧化水中p-CNB的效果之间没有直接的关系。当溶液pH值接近表面零质子电荷点pHpzc即表面几乎电中性时,O3/ZnOOH降解p-CNB效果最好。     

氧化改性活性炭吸附浓缩低浓度甲烷研究

采用H2O2和HNO3作为氧化剂,对市售煤基活性炭表面进行化学改性,探究活性炭表面官能团随氧化剂浓度的变化规律及其对甲烷吸附的影响。结果发现,硝酸氧化增加了活性炭表面的酸性官能团,碱性官能团降低,双氧水氧化使活性炭表面的内酯基含量明显增加,酸性官能团不利于活性炭对甲烷的吸附,而碱性官能团有利于甲烷的吸附。     

炼化污泥基催化剂协同臭氧处理难降解废水的研究

将炼化剩余活性污泥进行热解与碱处理,成功制备出可协同臭氧处理难降解废水的污泥基催化剂。在初始pH分别为5.8、7.0、10.0时处理硝基苯废水,与单独臭氧氧化相比,污泥基催化剂协同臭氧氧化处理的TOC去除率分别提高了34.1%、46.5%、27.9%。且在中性条件下的催化臭氧氧化处理过程中,与煤基活性炭相比,该污泥基催化剂能将TOC去除率提高15.7%。催化剂表面丰富的金属氧化物和含碳官能团构成复合活性中心,催化臭氧分解产生自由基。     

活性炭改性及在发黄偏二甲肼脱色中的应用

用活性炭吸附法对发黄偏二甲肼进行脱色处理.用浓氨水、1 mol/L的NH_4Cl溶液和0.5 mol/L的NaOH溶液对活性炭进行改性.结果表明,改性后的活性炭表面含氧酸性官能团的数量降低,碱性官能团的数量增加.由吸附等温线可知,偏二甲肼中氧化杂质在活性炭上的吸附过程是放热的,NaOH改性后活性炭的吸附量及对发黄偏二甲肼的脱色效果均大于原活性炭.     

活性炭的硝酸表面改性及其吸附性能

用硝酸对粒状活性炭进行了表面改性,考察了硝酸浓度及氧化时间对活性炭表面官能团的影响.采用傅里叶变换红外光谱仪(FT-TR)、Boehm滴定、X射线衍射仪(XRD)、物理吸附以及颗粒强度分析仪等对氧化前后样品进行了表征分析.以改性活性炭为载体,浸渍活性组分后制备了浸渍炭催化剂,考察了其对氯化氰防护性能.研究发现,低浓度硝酸氧化改性可增加活性炭表面酸性基团的含量,减少碱性基团的含量,从而提高活性炭的表面亲水性,而对活性炭的结构没有明显影响;制备的浸渍炭催化剂对氯化氰防护时间明显增长.当硝酸浓度为8%,氧化时间为8 h时防护效果最好.     

催化臭氧氧化处理难降解石化废水技术的研究进展

介绍了催化臭氧氧化的主要类别,分述了均相与非均相催化臭氧氧化在难降解石化废水方面的已有应用和催化机理,探讨了非均相催化臭氧氧化中活性炭的主要作用;简述了pH值、温度、臭氧和催化剂投加方式与投加量、催化剂体系等因素在非均相催化臭氧氧化中的影响规律。在已有研究的基础上,提出了将催化臭氧氧化与生化处理相结合的建议并佐证了其可行性;预测了催化臭氧氧化未来的研究方向;针对活性炭在催化臭氧氧化处理难降解石化废水中存在的问题,提出应加强对活性炭的改性研究,同时对某些工艺进行深入研究,全面掌握可能存在的问题,为完善催化臭氧氧化的机理作出努力。     

An Optimization Study of Cobalt Supported on Activated Carbon for the Catalytic Ozonation of Oxalic Acid: Effect of Operating Parameters and Synergetic Combination

In this study, new heterogeneous cobalt (Co) catalysts supported on activated carbon (Co/AC) were developed using a wetness impregnation process. The effect of preparation conditions on catalyst characteristics was examined. This work focused on two key parameters: the impregnation rate and the calcination atmosphere (temperature and time). Different catalysts were prepared by varying the Co loading on AC. Various catalysts were characterized by means of nitrogen sorptiometry at 77K, Boehm and pHpzc analysis. It was found that the catalyst properties and the functional surface groups were affected by the operating conditions. The best surface area was 997.5 m2/g obtained when the activated carbon was impregnated with 5% Co loading and calcined at 350°C for 2 h. The effects of parameters, such as cobalt loading, pH, catalyst dose, and ozone dose, were explored on oxalic acid removal (OA). Results show that the use of Co/AC for heterogeneous catalytic ozonation enhanced the degradation efficiency of oxalic acid (OA) significantly compared with simple ozonation and O3/AC. The main results indicate that the optimum catalytic activity was observed when 5% (wt/wt) of Co was supported on AC reaching a catalytic ozonation efficiency of 95%. The results of total organic carbon removal of 91% were achieved at optimum conditions.     

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.     

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     

Effect of Catalytic Ozonation Coupling with Activated Carbon Adsorption on Organic Compounds Removal Treating RO Concentrate from Coal Gasification Wastewater

This paper reports a novel system of catalytic ozonation coupling with activated carbon adsorption for removing the organic compounds treating in the RO concentrate from coal gasification wastewater. The effect of ozone dosage, catalyst dosage, reaction time, influence pH, and temperature on organic compounds removal were examined for the processes. In the catalytic ozonation process, increasing solution pH, dosages ozone, and catalyst were statistically significant for improving the performance. In addition, the high salinity with chloride concentration of 15 g/L could reduce the catalyst specific surface area by 18%. Thus, high salinity showed negative influence on the catalytic effect in TOC removal. Regarding activated carbon adsorption process, modified activated carbon by NaOH revealed advantages in adsorbing organic compounds treating catalytic ozonation effluent. With the ozone dosage of 120 mg/L, catalyst dosage of 2.0 g/L, catalytic ozonation reaction time of 1 h, and modified activated carbon adsorption time of 1 h, the average TOC removal efficiencies were maintained at the stable level of 58% with the TOC concentration of 26 mg/L.     

活性炭负载Fe~(3+)催化臭氧氧化水中双酚A

采用浸渍法在活性炭上负载铁制备催化剂Fe/AC,用于催化臭氧氧化水中内分泌干扰物双酚A(BPA),研究了Fe/AC/O3体系的协同效应,探讨了Fe/AC投加浓度、臭氧浓度和BPA初始浓度等工艺参数的作用规律,并分析了Fe/AC/O3体系在不同pH值下的催化反应机制。结果表明,在Fe/AC/O3体系下,反应60 min后,BPA和COD的去除率分别为97.44%和69.47%,效果明显优于臭氧体系的70.15%、30.89%和活性炭体系的14.69%、7.53%之和,具有明显的协同作用;Fe/AC/O3体系降解BPA符合一级反应动力学,当Fe/AC的投加浓度为5.0 g/L,臭氧浓度为15.0 mg/L,BPA初始浓度为50.0 mg/L时,Fe/AC/O3体系降解BPA的反应速率常数为0.05972 min-1;其反应机制受溶液pH值的影响,在酸性条件下是吸附和臭氧直接氧化共同作用,而在碱性条件下以·OH间接氧化为主,活性炭上负载的Fe3+促进了·OH的生成,大大提高了BPA的反应效率和矿化率。     

Catalytic Ozonation of Oxalic Acid in the Presence of Fe2O3-Loaded Activated Carbon

ABSTRACT

The activity and optimum condition of metal-loaded activated carbon catalyst (Me/AC) for oxalic acid (OA) ozonation were evaluated. Results showed that Fe-loaded activated carbon (Fe/AC) showed better activity in five kinds of Me/AC catalysts prepared by a dipping method. Fe catalyst, crystallizing as γ-Fe₂O₃, dispersed well on AC surface. Fe₂O₃/AC, with 1.12% Fe weight ratio and 450°C calcination temperature and showed better activity for OA ozonation. 89.2% of OA was removed in the Fe₂O₃/AC/O₃ process, which was higher than those in AC/O₃ (79.6%) and O₃ (3.2%) processes. The calcination process helped to promote adsorption capability and catalytic activity of AC. In addition, Surface hydroxyl groups played a key role in Fe₂O₃/AC’s catalytic activity. Acidic condition was more favorable for OA removal in the Fe₂O₃/AC/O₃ process. A hydroxyl radical (?OH) oxidation mechanism was proven in Fe₂O₃/AC/O₃. The catalytic activity of Fe₂O₃/AC remained satisfactory after several cycles, indicating that Fe₂O₃/AC had a good reusability property.     

Influence of the surface chemistry of multi-walled carbon nanotubes on their activity as ozonation catalysts

Multi-walled carbon nanotubes (MWCNTs) with different surface chemical properties were prepared by oxidative treatments with HNO₃, H₂O₂ and O₂ to introduce oxygen-containing surface groups and by thermal treatments for their selective removal. The texture and surface chemistry of the MWCNTs were characterized by nitrogen adsorption, temperature programmed desorption (TPD) and pH at the point of zero charge. A deconvolution procedure of the TPD spectra was used to quantify the oxygenated surface groups. These materials were used as catalysts for ozone decomposition, and for the ozonation of oxalic and oxamic acids. Generally, all these catalytic processes are favoured by carbon nanotubes with low acidic character. MWCNTs were shown to exhibit higher activity for the ozonation of oxalic and oxamic acids, compared to activated carbon. Successive experimental runs of oxalic acid removal carried out with a selected MWCNT sample show that the catalyst suffers some deactivation as a result of the introduction of oxygenated groups on the surface. Therefore, the effect of the surface chemistry is mainly observed for the fresh catalysts.     

活性炭改性对用于甲酸分解的Pd/活性炭催化剂的影响

采用磁力搅拌法和水浴振荡法制备应用于甲酸分解的Pd/活性炭(AC)催化剂,研究了活性炭载体改性和制备方法对催化剂分解甲酸性能的影响。采用恒温水浴振荡装置,在80℃水浴中进行甲酸催化分解反应,以甲酸的催化分解率评价催化剂催化活性。结果表明,以经过不同的酸、碱、盐溶液改性后的活性炭为载体采用不同方法制备的Pd/AC催化剂对甲酸的催化分解效果不同,以Na2CO3改性的活性炭为载体采用磁力搅拌法制备的催化剂活性最好,甲酸水溶液的分解率达85%以上,含甲酸的工业废水的分解率达70%。     

Catalytic Ozonation of Oxalic Acid Using SrTiO3 Catalyst

A new catalyst, strontium titanate (SrTiO₃), has been successfully employed to degrade oxalic acid in catalytic ozonation process. About 4.5%, 9.3% and 45.8% of oxalic acid removal efficiencies were noted in adsorption, ozonation, and catalytic ozonation processes, respectively, which demonstrates the catalytic activity of SrTiO₃ towards ozone_. The optimum amount of catalyst loading on decomposing oxalic acid was found to be 1.25 g/L. The catalytic stability was investigated up to four successive cycles and found that the catalyst was still stable and efficient.     

Pyruvic Acid Removal from Water by the Simultaneous Action of Ozone and Activated Carbon

Activated carbon (AC) has been used to catalyze the ozonation of pyruvic acid in water. Pyruvic acid conversions were found to be 9 and 37% after 90 min of single ozonation and single adsorption with 40 gL^?1 AC, respectively, while 82% was reached at the same conditions during the AC catalytic ozonation. Also, for similar conditions, mineralization reached values of 67% in the AC catalytic ozonation against hardly 5% in the non-catalytic experiment. The process likely develops through both adsorption of ozone and pyruvic acid on the AC surface and generation of hydroxyl radicals that eventually is the responsible oxidizing species. Rate constants for both non-catalytic ozonation and AC-Ozone catalytic surface reaction, at 20°C and pH 7.5, were found to be 0.025 min^?1 and 87.9 Lg^?1s^?1, respectively. For AC concentrations higher than 2.5 gL^?1 gas-liquid mass transfer of ozone constituted the limiting step. At lower concentrations, internal diffusion plus surface reaction controlled the process rate.