催化臭氧氧化/沉淀耦合技术处理钨冶炼废水中典型无机污染物的系统优化

Usually the concentration of typical inorganic contaminants such as NH4+-N, As, Cd and other metal ions in APT production wastewater may be several times more than the Integrated Wastewater Discharge Standard (GB8978-1996). Catalytic ozonation process can produce strong oxidant-hydroxyl radicals and be widely used in the field of organic wastewater treatment. Being typical inorganic pollutants in wastewater such as ammonium-nitrogen, arsenic and cadmium as objects, the catalytic ozonation technology is being adopted to solve the problem that oxidating selectively ammonium cation to nitrogen and arsenite anion to arsenate in wastewater. The relationship between the catalyst of the physical structure and surface state and catalytic activity is studied. And the scientific hypothesis of catalytic ozonation degradation of inorganic wastewater is verified. Precipitation technology is introduced into catalytic ozonation process and the coupling effect between precipitation and catalytic ozonation process were studied. Catalytic ozonation/precipitation coupled optimization of process parameters of key scientific issues is revealed. Eventually it is introduced on a technical level in the coupling the least amount of chemicals/ energy, resulting in the least amount of secondary pollutants, achieving the best results, waste is resourced as far as possible at the same time. The target of efficient purification tungsten metallurgy wastewater may be achieved, so as the sustainable development of tungsten metallurgy industry promoted. The new ideas and the experiences for other metallurgy wastewater treatment may be provided. Its environmental, economic and social benefits are also be evaluated.

通常仲钨酸铵(APT)生产废水中典型无机污染物浓度可能超过《污水综合排放标准》数倍，对环境影响极大。催化臭氧氧化技术因能产生大量高氧化性自由基(·OH)氧化污染物而广泛用于有机废水处理。本课题拟以钨冶炼废水中典型无机污染物为研究对象，采用催化臭氧氧化技术，解决催化臭氧选择性氧化降解废水中氨氮阳离子及亚砷阴离子问题，使氨氮氧化为氮气排出，三价砷氧化为五价砷，并研究催化剂微观结构、表面特性与催化活性间的关系，验证催化臭氧氧化降解无机废水的科学假设；在催化臭氧氧化过程中引入沉淀技术，五价砷及镉离子通过沉淀、絮凝作用得到净化，剖析催化臭氧氧化与沉淀过程的耦合机制，揭示催化臭氧氧化/沉淀耦合工艺参数优化的关键科学问题，最终在整个耦合技术层面上达到引入最少化学药剂、产生最少二次污染物、取得最佳净化效果的目的；为钨冶炼行业可持续发展提供科学理论依据，为其它冶炼废水处理提供思路和借鉴；并对该技术进行评价。

通常仲钨酸铵(APT)生产废水中典型无机污染物浓度可能超过《污水综合排放标准》数倍，对环境影响极大。课题以钨冶炼废水中典型无机污染物为研究对象，采用催化臭氧氧化技术，解决催化臭氧选择性氧化降解废水中氨氮阳离子及亚砷阴离子问题。结果表明：1）在焙烧温度500℃、焙烧时间3 h、Mg/Co摩尔比为8∶2条件下制备的复合催化剂对氨氮的降解具有最高的活性，同时对产物氮气具有最高的选择性。当氨氮初始浓度50 mg/L，溶液pH 9，臭氧流量12 mg/min，催化剂投加量1 g/L，反应温度50℃，反应时间2 h时氨氮去除率为81.6 %，氮气转化率为44.1 %。Mg/Co催化臭氧氧化氨氮的主要活性物质为羟基自由基。2）基于氨氮去除率高和气态氮产量高的角度考虑，阳离子表面活性剂/金属氧化物的CTAB/NiO催化剂具有较好的催化活性。在氨氮初始浓度50 mg/L，溶液初始pH值9，O3投加量12 mg/min，磁力搅拌速度600 r/min，反应时间120 min的条件下，投加1.0 g/L CTAB/NiO参与反应时，氨氮去除率达到98.11%，气态氮产量达到74.67%。该催化剂在处理某稀土冶炼厂氨氮废水时，氨氮去除率和气态氮产率分别达到99.28%和75.60%。3）研究了As(Ⅲ)与氨氮被臭氧氧化的竞争机制，发现As(Ⅲ)优先于NH4+-N被氧化。在Ce/Mn摩尔比1∶2，400℃下煅烧3 h下得到的催化剂其催化活性最高。常温下，反应pH为9，臭氧流量为12 mg/min，臭氧曝气时间45 min，催化剂投加量1.50 g/L时效果最佳，含As(Ⅲ)、氨氮溶液中初始浓度为50 mg/L的氨氮经反应后其转化率为80.69%，对气态氮的选择性为40.99%，其中NO2 7.40%，NO 0.85%，NH3 0%，其他32.74%的气体可视为是N2；初始浓度为2 mg/L的As(Ⅲ)被氧化为As(Ⅴ)的效率高达99.20%。共存阳离子Na+、K+、Ca2+、Mg2+并不会影响催化臭氧氧化效能；共存阴离子SO42-和HCO3-会抑制氨氮的氧化，Br-和CO32-则能够促进氨氮的氧化，但是这4种阴离子对As(Ⅲ)氧化为As(Ⅴ)的效能并无显著影响。采用铁盐作为除砷沉淀剂，n(Fe)/n(As)为1.50，溶液pH值为7，沉淀10 min，AsT去除效果高达99.10%。