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废水中重金属离子往往会与一些有机配体(EDTA、有机酸等)形成可溶性络合物,对微生物和水生动植物产生毒害作用[1]。由于络合物稳定性较强,因此,在对重金属进行调碱沉淀去除之前,需要对络合物进行氧化破络,使其释放出重金属离子[2-3]。高级氧化技术目前已被广泛应用于络合物的破络处理,如光催化法、电化学法、芬顿法及类芬顿法[4-6]。光催化氧化法反应条件要求较高,在实际应用中局限性较大。电化学法受电极材料限制较大,对于高浓度络合态重金属的去除效果较差。芬顿法的氧化能力较强且反应速度快,但是传统芬顿法对过氧化氢(H2O2)利用率低,所需氧化剂和催化剂的浓度较高,增加了处理成本。PS作为类芬顿法中的一种氧化剂,廉价易得,能在高效催化剂的活化的作用下,快速高效地催化降解污染物[7]。
研究表明,结构对称的PS易被过渡金属类催化剂活化[8]。然而,单独的过渡金属类催化剂具有金属离子较易溶出和碱性条件下催化性能偏低等缺陷,将金属类催化剂与BC结合,能够提高催化剂整体的稳定性和石墨化程度,进而提升催化性能。目前碳基金属负载型材料被广泛应用于水中有机污染物的降解。YAN等[9]将零价铁和BC负载活化PS降解水中的三氯乙烯,负载后材料整体的抗氧化性和催化活性得以提升;OUYANG等[10]将磁性Fe3O4和BC负载,使催化材料的活性点位增多,从而更有效地活化PS降解水中的1,4-二恶烷。在多种过渡金属材料中,CuO由于具有优异的物理和化学性质而被广泛应用在催化,传感和电极材料等领域,尤其是在活化PS的过程中,具有较强导电性的CuO材料可以充当电子中间体,加快电子转移,通过非自由基途径加速污染物的降解,这使得CuO负载型材料在催化性能方面脱颖而出[11-12]。目前关于碳基CuO负载型材料活化PS的研究大多集中在降解水中有机污染物方面,而在处理EDTA-Cu/Ni/Zn络合物方面的研究鲜有报道,同时研发出快速高效去除水中络合态污染物新技术尤为重要。本研究利用CuO@BC活化PS对EDTA-Cu废水进行氧化破络处理,实现对有机物的降解,再进行调碱沉淀实现对重金属的去除,研究CuO@BC-PS体系对EDTA-Cu、TOC和铜的去除效果及影响因素,通过淬灭实验和EPR图谱初步阐明了该体系降解EDTA-Cu的机理。
铜基生物炭活化过硫酸钠处理废水中EDTA-Cu
Removal of EDTA-Cu in wastewater by copper-based biochar activated sodium persulfate
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摘要: 为实现废水中EDTA-Cu的快速破络和去除,以铜基生物炭(CuO@BC)为催化材料活化过硫酸钠(PS),探究了EDTA-Cu、TOC和铜的去除效率及影响因素,初步揭示了催化机理。结果表明,CuO@BC-PS体系能够在60 min时有效去除97.1%的EDTA-Cu和69.6%的TOC,并且通过沉淀去除62.2%的铜。氧化铜(CuO)是提高复合材料催化作用的关键因素,降解反应体系中自由基作用不大,非自由基途径活化PS是降解EDTA-Cu的主要原因。以上研究结果可为络合态重金属污染废水的高级氧化处理提供参考。
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关键词:
- 铜基生物炭(CuO@BC) /
- 过硫酸钠(PS) /
- EDTA-Cu /
- 破络 /
- 非自由基途径
Abstract: To accelerate the decomplexation and removal of EDTA-Cu in wastewater, the copper-based biochar (CuO@BC) was used as a catalytic material to activate sodium persulfate (PS). The removal efficiency of EDTA-Cu, TOC and Cu and their impact factors were studied, and the catalytic mechanism was preliminarily revealed. The results showed that the CuO@BC-PS system could effectively remove 97.1% EDTA-Cu and 69.6% TOC at 60 min, and 62.2% Cu would be removed by precipitation. Copper oxide (CuO) was the key factor to improve the catalysis of composite materials, free radicals had little effect in the degradation reaction system, and the degradation of EDTA-Cu was mainly achieved by the non-radical pathway for PS activation. The research results provide theoretical basis for advanced oxidation treatment of complexed heavy metal contaminated wastewater.-
Key words:
- copper-based biochar (CuO@BC) /
- sodium persulfate (PS) /
- EDTA-Cu /
- decomplexation /
- non-radical pathway
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