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基于活性炭的非均相催化臭氧化研究及其在焦化废水深度处理中的应用
Alternative TitleActivated Carbon Based Catalytic Ozonation and Its Application in Advanced Treatment of Coking Wastewater
邢林林
Subtype博士
Thesis Advisor张懿
2014-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline环境工程
Keyword活性炭 臭氧 催化 草酸 焦化废水
Abstract焦化废水是一种毒性强、难处理的工业废水,处理不彻底的废水排入水体会造成严重的环境影响,日趋严格的国家环保政策对焦化废水深度处理提出了更高的要求。本文在非均相催化臭氧化模拟体系研究的基础上,开发出适用于焦化废水深度处理的非均相催化臭氧化工艺,并逐步实现工程放大。主要研究内容如下: (1)考察了不同操作条件下活性炭对草酸臭氧化的影响,发现活性炭可引发或促进臭氧分解产生HO?,但其对HO?有捕获作用并会抑制臭氧分解。活性炭可显著促进草酸臭氧化,提高活性炭投加量可提高草酸去除率、臭氧消耗量和臭氧效率;提高臭氧投加量可提高草酸去除率和臭氧消耗量,但会降低臭氧效率;提高溶液pH会降低草酸去除率,增加臭氧消耗量,因而降低臭氧效率。在20~40°C范围内,温度的影响很小。在活性炭强化臭氧化体系中,草酸通过本体溶液中的HO?氧化和表面氧化两种途径去除。提高活性炭、臭氧投加量,降低pH和温度会增加表面氧化对草酸的去除率。提高活性炭、臭氧投加量、pH和温度会增加本体溶液中HO?氧化对草酸的去除率。但活性炭投加量较高、臭氧投加量较低或pH过高时,本体溶液中HO?更易被活性炭捕获。活性炭投加量较低,臭氧投加量较高及弱碱性pH时促进本体溶液中HO?的产生。 (2)脱除矿物质实验表明活性炭表面的矿物质在一定程度上可以促进草酸降解。矿物质中的含铁化合物可能是促进草酸臭氧化的主要活性物质,而SiO2对草酸臭氧化没有作用。 (3)考查了活性炭表面碱性位点对草酸臭氧化的影响。在氮气、氢气和氨气下对活性炭进行热处理以获得具有不同种类和含量碱性位点的活性炭并对其进行表征。热处理可以提高活性炭的碱性。氨气处理可以增加活性炭表面的含氮官能团。草酸臭氧化实验表明热改性活性炭比原始活性炭对草酸去除的促进作用更大。草酸去除速率随活性炭改性温度的升高而加快。活性炭改性后碱性更强,比表面积更大,对草酸的吸附增加,因而对草酸臭氧化的促进作用更大。表面氧化对草酸的去除率随碱性位点含量的增加而升高,但本体溶液中HO?氧化对草酸的去除率随之降低(900oC氨气下处理的活性炭除外)。活性炭表面的吡啶基团可能不利于草酸的表面氧化;而吡咯基团会促进臭氧分解产生HO?。其它碱性位点如裸露的石墨基面和碱性含氧官能团有利于草酸的表面氧化,但是间接降低本体溶液中的HO?氧化对草酸的去除。碱性大的活性炭不仅可增加草酸的去除,还能提高臭氧效率。 (4)考察了活性炭表面酸性位点对草酸臭氧化的影响。对活性炭进行预臭氧化以获得具有不同含量酸性位点的活性炭。活性炭表面酸性位点的含量随预臭氧化时间的延长而增加,碱性位点的含量则随之减少。相比采用原始活性炭的臭氧化体系,采用预臭氧化活性炭体系的草酸去除率更低;且活性炭氧化程度越高,草酸去除率越低。活性炭表面的酸性位点不利于草酸通过表面氧化的去除。酸、碱性位点含量较低时可以促进本体溶液中HO?氧化对草酸的去除,含量较高时则有负作用。 (5)开展实际焦化废水催化臭氧化研究,验证技术经济性。研发出适用于焦化废水深度处理的高效催化剂,考察了臭氧投加量、pH、温度、反应器类型等因素对催化臭氧化效率的影响。对处理前后的废水进行多种分析,表明催化臭氧化可有效降解焦化废水生化出水中的多数化合物。在催化臭氧化体系中,有机物的去除是臭氧氧化、活性炭吸附、活性炭表面氧化和本体溶液中的HO?氧化共同作用的结果。水中无机碳对COD降解的影响不大。在某钢铁企业进行现场小试和中试结果表明催化臭氧化系统运行稳定,出水满足国家、地方和行业污水排放标准的要求。
Other AbstractCoking wastewater is a kind of toxic and refractory industrial wastewater. Serious environmental problems would be caused if it were not treated efficiently before discharging into the natural water matrixes. The more stringent wastewater discharge standards urgently require advanced treatment of coking wastewater. Based on the study on activated carbon enhanced ozonation of oxalic acid, an efficient heterogeneous catalytic ozonation process for advanced treatment of coking wastewater was developed and its engineering scale-up was achieved. The main contents and some promising results obtained are as follows: (1) The effects of activated carbon (AC) on oxalic acid ozonation under various operational conditions were studied. It was found that AC enhanced the ozonation of oxalic acid significantly. Higher AC dosage led to higher oxalic acid removal, ozone consumption and ozone efficiency. Higher ozone dosage led to higher oxalic acid removal and ozone consumption, but lower ozone efficiency. Higher solution pH led to lower oxalic acid removal but higher ozone consumption, thus lower ozone efficiency. The effect of temperature was relatively small when the solution temperature varied from 20 to 40 °C. In the AC enhanced ozonation system, oxalic acid was removed through two pathways: hydroxyl radical (HO?) oxidation in bulk solution and surface oxidation. Increasing AC and ozone dosage, decreasing temperature and solution pH led to higher removal of oxalic acid through surface oxidation. Increasing all the four parameters led to higher removal of oxalic acid through HO? oxidation in bulk solution. However, HO? in bulk solution was scavenged by AC under the conditions with high AC dosage and pH, and low ozone dosage. Lower AC dosage, higher ozone dosage and weakly basic solution promoted the generation of HO? in bulk solution. A mechanism involving the initiation, promotion and inhibition effects of AC on ozone decomposition was proposed. (2) A comparison between results of oxalic acid ozonation with original and demineralized ACs indicates that minerals on AC could enhance the oxidation of oxalic acid to some extent. SiO2 had no effect on the ozonation of oxalic acid, while Fe-containing compounds may be the active matter to enhance it. (3) The effect of type and number of basic sites of AC on the ozonation of oxalic acid was studied. A commercial AC was thermally treated with N2, H2, and NH3 at different temperatures to obtain ACs with different type and number of basic sites. Thermal treatment increased the basicity of AC and decreased the acidity of AC. Ammonia treatment increased the number of nitrogen-containing groups on AC. The oxalate removal rate increased in the ozonation systems with modified ACs. Oxalic acid degradation increased when ACs with higher number of basic sites and larger specific surface area were used, except for the AC treated under NH3 at 900 °C. The adsorption of oxalic acid on ACs was considered important in the surface oxidation of oxalic acid. The experimental results indicate the pyrrole groups may enhance ozone decomposition to generate HO? in bulk solution, while the pyridine groups possibly decreased the surface oxidation of oxalate. Other basic sites, such as basal planes and basic oxygen-containing groups, enhanced oxalate removal through surface oxidation, and indirectly weakened the contribution of HO? oxidation of oxalic acid in bulk solution. (4) The effect of acid sites of AC on the ozonation of oxalic acid was studied. AC was pre-ozonized with different dosages of ozone to obtain ACs with different number of acid sites. The results of characterization indicate that the number of acid sites increased while the number of basic sites decreased with increasing pre-ozonation time. The removals of oxalic acid in the ozonation systems with pre-ozonized ACs were lower than that with original AC. And the oxalic acid removal decreased with increasing pre-ozonation time. The acid sites were detrimen
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/15510
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
邢林林. 基于活性炭的非均相催化臭氧化研究及其在焦化废水深度处理中的应用[D]. 北京. 中国科学院研究生院,2014.
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