异步周期换向电凝聚法处理活性艳蓝X-BR模拟染料废水及其机理研究

针对传统电凝聚法处理废水过程中易出现的电极表面钝化和极化而影响处理效果的现象,采用铝和铁板作为两极同步换向方法,通过周期性改变电流方向使电极钝化和极化现象得以减缓或消失,并实现两极均可溶,利用铝、铁系无机絮凝剂共存时可提高处理效果的特点,对活性艳蓝X-BR模拟染料废水进行处理;通过正交试验,获得了该方法的最佳处理条件.在此基础上,为避免金属铝成分在废水中出现剩余影响水质,采用异步周期换向方式加以改进,考察了铝、铁电极不同通电时间对处理效果的影响,并利用紫外-可见光分光光度法、高效液相色谱法、ICP法、高分辨质谱技术、激光粒度分析仪等手段对废水处理过程主导因素和污染物去除机理以及该方法对强化处理效果的作用机理进行了分析.研究表明,最佳条件下采用异步换向周期电凝聚法处理活性艳蓝X-BR模拟染料废水30 min可使模拟废水脱色率接近100%,COD去除率可达76%以上;处理过程中起主导作用的是电凝聚过程而非电氧化还原过程;除大部分染料分子被电凝聚气浮或沉降导致脱色外,其余的活性艳蓝X-BR染料分子在电解作用下首先断裂生成了1,4-二氨基蒽醌-2-磺酸根,之后1,4-二氨基蒽醌-2-磺酸根又被直接絮凝上浮或沉降,或者在氢离子作用下发生了加氢反应使双键消失而脱色,模拟废水脱色是上述作用的综合结果.采用改进后的异步周期换向电凝聚法可以使铝铁离子凝聚过程形成的絮体具有更为合理的粒度和结构特性,从而更易于被去除,因此处理效果略优于同步换向和定向电流电凝聚过程,且可以实现处理后废水中铝离子含量降低到无法检出,避免其在处理后的废水中出现剩余影响水质.

Study on the treatment and mechanism of Active Brilliant Blue X-BR synthetic dye wastewater by asynchronous periodic reversal electro-coagulation method

Surface passivation and polarization of electrode reduce the wastewater treatment efficiency of electro-coagulation method. In this article asynchronous periodic reversal electro-coagulation with Al/Fe electrodes was applied to treat Active Brilliant Blue X-BR synthesized dye wastewater in order to avoid passivation and polarization. With the co-existence of iron and aluminium flocculating agents, applying periodic reversal current can dissolve passive film of the electrodes in succession during the electrolyzation process, thus improving the efficiency of decolorization and COD removal. In this study, different operation time was applied on respective anode to avoid the remaining of Al³⁺ in the effluent after treatment, it is different from traditional electro-coagulation method and the method previously reported by the author's research team which synchronism periodically reversing electro-coagulation with Al/Fe was used. Influencing factors, such as operation time, voltage, stirring speed, initial dye concentration, electrode spacing, initial pH, supporting electrolyte concentration, and synchronization alternating period, on the treatment efficiency were investigated, and the optimal experimental conditions were obtained by using orthogonal test. Based on the optimal experimental conditions, asynchronization alternating period of iron and aluminium electrodes were investigated, and the concentration of Al³⁺ in the treated water was monitored to make comparison with synchronization alternating period method. when the initial dye concentration was 200 mg · L^-1, the optimal experimental conditions were obtained as in the following conditions: voltage 10 V, stirring speed 750 r · min^-1, concentration of supporting electrolyte Na₂SO₄ 0.011 mol · L^-1 of dye solution, electrode spacing 0.5 cm, 6< initial pH <8, operation time of iron electrode was 57 s, operating time of aliuminium electrode was 3 s. Almost 100% decolorization rate and more than 76% COD removal rate were obtained after 30 min treatment under the optimal conditions. And the content of Al³⁺ couldn't be detected after treatment with 20 min to 45 min. The treatment process was characterized using UV-Vis spectrophotometry, ICP, HPLC, and TOF spectrometer techniques. The removal of COD mainly depends on the electro-coagulation, and the residual Active Brilliant Blue X-BR molecules was broken into 1,4- two aminoanthraquinone-2-sulfonic acid radical, and then was settled or floated or the hydrogen ions were added to the double bond of 1,4- two aminoanthraquinone-2-sulfonic acid radical. The decolorization of the wastewater was the results of all of the above. Using the asynchronous periodic reversal electro-coagulation method, better structures and particle size of Fe³⁺/Al³⁺ coagulant were obtained, which makes it easier to remove in the wastewater. As a result, Al³⁺ can not be detected after the treatment.