镀铜废水中Cu^(2+)-H_2O_2体系氧化降解硝基苯

Oxidative degradation of nitrobenzene catalyzed by Cu^(2+)-H_2O_2 system in copper rinse water

镀铜工业废水中除含有大量的铜离子和有机污染物外,还常常含有大量的过渡金属离子、无机阴离子及有机络合剂。这些物质的存在会对铜催化的类芬顿反应降解有机物造成效能上的影响,甚至改变其反应途径。实验体系在单纯的Cu^(2+)-H_2O_2体系氧化降解硝基苯的基础上,研究了过渡金属离子Ni2+、Mn2+、无机阴离子及有机络合剂对于铜催化的类芬顿反应降解硝基苯效能的影响。在常温条件下,单纯的Cu^(2+)-H_2O_2体系中,当p H为5.5,Cu^(2+)为0.8 mmol·L-1,H_2O_2为0.08 mol·L-1,180 min后硝基苯的去除率可达94.67%,有机物的降解率达到最大。Ni2+会抑制Cu^(2+)-H_2O_2体系中硝基苯的降解,然而Mn2+对于Cu^(2+)-H_2O_2体系中硝基苯的降解却有明显的促进作用。无机阴离子Cl O-4、Cl-、NO-3、H2PO2-4对于Cu^(2+)-H_2O_2体系氧化降解硝基苯都有显著的抑制作用。有机络合剂乙二胺四乙酸(EDTA)、柠檬酸(CA)、氨三乙酸(NTA)对于铜催化的类芬顿反应都有显著的抑制作用,然而酒石酸(TA)对于Cu^(2+)-H_2O_2体系中硝基苯的氧化降解却有明显的促进作用。铜催化的类芬顿反应所生成的活跃氧化物的性质对于p H有很强的依赖性,在酸性条件下,羟基自由基是主要的活性氧化物,而在微酸性和中性、碱性条件下,羟基自由基和高价态的铜氧化物是同时参与反应并且相互兼容的,并且体系的p H越高,高价态的铜氧化物的含量也越大。

In addition to containing many copper ions and organic pollutants, copper rinse water also fre- quently contains numerous transition metal ions, inorganic anions, and organic eomplexing agents. The presence of these substances can influence the degradation of organic pollutants in Fenton-like reactions catalyzed by cop- per, even changing the reaction pathway. In this study, the influence of transition ions, inorganic anions, and organic-complexing agents on the degradation of organic pollutants in Fenton-like reactions catalyzed by copper was studied considering the oxidation degradation of nitrobenzene in a pure Cu2＋ -Ha O2system. In a pure Cu2＋- H202system at 25 ℃ and pH 5.5 with concentrations of Cu2＋ and H202 of 0.8 mmol · L-1 and 0.08 mol · L-1 , respectively, the removal rate of nitrobenzene reached 94.67% and the degradation ratio of organic substances reached maximum value. Ni2＋ inhibited the degradation of nitrobenzene in the Cu2-H202 system, whereas Mn2＋ promoted the degradation of nitrobenzene. The inorganic anions, C104 , C1- , NO3- , H2PO2- , all had sig- nificant inhibitory effects on the oxidation degradation of nitrobenzene. The organic-complexing agents, ethylene- diaminetetraacetic acid, citric acid, and nitrilotriacetic acid, all had significant inhibitory effects on the Fenton- like reactions catalyzed by copper; however, tartaric acid had a promoting effect on the oxidation degradation of nitrobenzene in the Cu2＋ -H2 02 system. The nature of the reactive oxidants that originated from the copper-cata- lyzed Fenton-like reactions depended strongly on the pH. Under acidic conditions, hydroxyl radicals were the main active species, whereas under slightly acidic, neutral, or alkaline conditions, hydroxyl radicals and high- valence copper species both participated in the reactions and were compatible. In addition, the higher pH, the more high-valence copper species in the system.