【作者】 王征；

【导师】 朱茂旭；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2007， 硕士

【摘要】 染料废水排放造成的环境污染日趋严重,我国染料废水每天排放量约为4×106 m3以上。染料废水具有有机物浓度高、色度高、无机盐含量高、成份复杂、可生化性差、脱色困难等特点,且含有多种具有生物毒性的有机物。锰氧化物在自然界分布广泛,是土壤和沉积物的重要组分。锰氧化物具有表面积大、零电荷点(pHzpc)低、表面活性高、电极电位高等特点,在苯酚类、苯胺类、脂肪胺、芳香胺类和含N杂环等有机物的降解和矿化过程中起关键作用。因此,锰氧化物的存在深刻影响着有机物在土壤和水体系中的浓度和存在形态。本论文主要做了两个部分的研究工作:(1)锰氧化物在自然界中以两种形态存在:在铁锰富集区,锰氧化物主要以颗粒态存在;在多数沉积物和土壤中,锰氧化物则主要以膜的形式覆盖在于粘土颗粒表面,因为在还原条件下,Mn(II)很容易吸附在带负电荷的粘土矿物表面(特别是蒙脱石),经氧化后形成锰氧化物膜。氧化膜的存在改变了粘土颗粒的表面特征,同时锰氧化物膜的表面特征也与纯锰氧化物有很大的不同。目前,关于膜形态的锰氧化物研究较少,本文采用Boonfueng(2005)提出的方法,合成了δ-MnO2和δ-MnO2-钠基蒙脱石复合体(FHT)(FHT中δ-MnO2以膜的形式包裹于蒙脱石表面),在模拟酸性环境(pH = 4.0~5.5)中,首次探讨了颗粒态和膜态的δ-MnO2的吸附和氧化两种作用分别在次甲基蓝脱色过程中的贡献;研究了FHT中Mn含量、溶液pH值、胡敏酸(HA)的存在等因素对次甲基蓝脱色率的影响。结果表明:δ-MnO2表面的非均相氧化是次甲基蓝脱色的主要机制,吸附是氧化的前提条件。在颗粒态和膜态δ-MnO2的氧化作用下,次甲基蓝脱色速率大小相近,但前者略低于后者。次甲基蓝的脱色率随FHT中Mn含量的增加和溶液pH的降低而提高。在次甲基蓝脱色过程中,吸附作用脱色率随pH的升高而提高,而氧化作用脱色率随pH的升高而降低。pH = 4.0~5.5条件下,HA以有机膜的形式包裹在FHT的表面,通过吸附和分配作用提高了次甲基蓝的脱色率。(2)锰氧化物含量较高的海洋铁锰结核以及提取有经济价值的金属后的残余物都可作为去除Pb2+、Ni2+、Cu2+等重金属阳离子、Se和P等含氧阴离子有效吸附剂,应用于废水处理。但将其作为氧化剂对有机污染物降解的研究还未见有报道。本文利用锰氧化物具有较高的表面吸附与氧化还原化学活性的特点,首次研究了采自东太平洋的铁锰结核在不同条件下对阳离子染料次甲基蓝氧化性脱色特征,并探讨了其影响因素。结果表明,铁锰结核表面的非均相氧化是次甲基蓝脱色的主要机制,起氧化作用的是其中的锰氧化物。在通常的染料废水浓度范围内(10~50mg·L-1),铁锰结核可有效地脱色和降解含次甲基蓝染料废水。随染料浓度降低、铁锰结核投放量增加和粒度减小,次甲基蓝的脱色率明显提高。次甲基蓝的矿化程度较高,但低于脱色率。pH对次甲基蓝脱色率的影响主要体现在对表面络合体形成和对体系还原电位的影响上,当pH <4.0时,脱色率随酸度的增加明显提高;当pH在4.0~10.0时,溶液pH值对脱色率影响有限。在铁锰结核连续循环利用过程中,体系中溶解Mn2+浓度和体系pH的增加是脱色率不断下降的主要原因。本论文的研究表明,锰氧化物矿物应用于染料废水处理具有良好的发展前景。更多还原

【Abstract】 Environment pollution caused by dye wastewater is becoming progressively serious in recent years. In China, the total discharge of dye wastewaters per day exceeds 4×106 m3. Generally speaking, dye wastewaters are characterized of high concentration of organic matter, high chroma, high salinity, complex compounds, low biodegradability, and contain many organic compounds which are toxic to microbes. Mn (hydro)oxides, which have large surface area, low pHzpc, high surface activity and high reducing potential, are distributed widely in natural environments, such as soils and sediments. It may play a key role in degradation and mineralization of a lot of organic contaminants such as phenol, aniline, aliphatic amine, aromatic amine and heterocyclic N-organism. Therefore, Mn (hydro)oxides significantly affect the concentration and species of organic matters in soil and aquatic systems.The thesis consists of two parts:(1) The presence of Mn (hydro)oxides is mainly in two forms in the nature. In areas rich in iron and manganese, Mn (hydro)oxides exist as granule. In most sediments and soils, Mn (hydro)oxides exist as coating on clay minerals, because, under anoxic conditions, Mn(II) is readily adsorbed on negatively charged surfaces such as clay particles (especially montmorillonite), then is oxidized to Mn (hydro)oxides coating on clay minerals. The coating may cause significant variation in surface properties of clay particles. Also the surface chemistry of Mn (hydro) oxide coating differs greatly from those of pure Mn (hydro)oxides. To date, investigations on Mn (hydro)oxide coating are rare. In this thesis, the method proposed by Boonfueng (2005) is used for synthesis ofδ-MnO2 andδ-MnO2- montmorillonite complexes (FHT). In simulated acidic conditions (pH = 4.0~5.5), contributions of absorption and oxidation ofδ-MnO2 in the form of granule and coating to MB decolorization are evaluated, respectively; effects of Mn content in the FHT, the solution pH and the presence of humic acid on MB decolorization are investigated. The results show that heterogeneous oxidations on the surfaces ofδ-MnO2 are the main mechanism for MB decolorization, and surface absorption is an important process for following oxidation degradation. As for decolorization ratios of MB, the capacities of two forms ofδ-MnO2-granule and coating-to degrade MB are similar, and the former is slightly lower than the latter. The MB decolorization ratio increases with increasing Mn amount and decreasing pH. As for the total MB decolorization, the contribution from absorption mechanism increases with an increase in pH. However, the contribution from oxidation mechanism decreases with an increase in pH. When pH is at the range between 4.0 and 5.5, HA coats FHT in a form of organic film, which can improve the decolorization ratio of MB through both absorption and partitioning mechanisms.(2) The content of Mn (hydro)oxides in Fe-Mn nodules is high. Fe-Mn nodules and their residues after extraction of valuable metals are found to be good adsorbents for a number of pollutants such as Zn2+, Pb2+, Ni2+, phosphate and selenite, and thus can be used in wastewater treatment. But few researches on application of Fe-Mn nodules as an effective oxidant for degradation of organic contaminants in water treatment are arried out. Manganese oxides are powerful oxidizers as well as scavengers for many inorganic and organic compounds. Fe-Mn nodules collected from the East Pacific Ocean are used for decolorization of MB in a batch system. Factors influencing MB decolorization are also evaluated. The results show that heterogeneous oxidations on the surfaces of Fe-Mn nodules are the main mechanism for MB decolorization. In typical concentration range of dye wastewaters (10~50 mg·L-1), Fe-Mn nodules can be used as an effective material for MB wastewater treatments. The percentage of MB decolorization is enhanced rapidly with increasing loading and decreasing particle size of Fe-Mn nodules, as well as decreasing MB concentration. A high degree of MB mineralization can be obtained at an optimal condition, but usually lower than that of MB decolorization. pH exerted effects on MB decolorization by influencing both the formation of surface precursor complex and redox potential of the system. At pH <4.0, MB decolorization increases with a decrease in pH, while pH at the range between 4.0 and 10.0 exerts only limited effect on MB decolorization. In a consecutive reuse system, Mn2+ accumulation due to reductive dissolution of Mn oxides, and pH increase due to H+ consumption are probably two important factors causing a decrease in MB decolorization with time.The results of the thesis showed that there is good development foreground for the application of Mn (hydro)oxides on the dye wastewater treatments.更多还原