A quantitative comparison between chemical dosing and electrocoagulation
A quantitative comparison between chemical dosing and electrocoagulation
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DOI：
10.1016/s0927-7757(02)00285-6
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发表时间：
2002-12-03
影响因子：
5.2
通讯作者：
Mitchell, CA
中科院分区：
文献类型：
--
作者：
Holt, PK;Barton, GW;Mitchell, CA
由于寻求可靠、经济高效的水处理工艺，人们对电凝聚重新产生了兴趣。由于施加电势，该技术在牺牲阳极腐蚀时原位提供混凝剂，同时在阴极放出氢气，从而可以通过浮选去除污染物。相比之下，传统的化学剂量通常会添加混凝剂的盐，并通过沉降提供主要的污染物去除途径。本文基于与粘土污染物相关的浊度去除，对这两种方法进行了定量比较。通过使用硫酸铝（明矾）的广口瓶测试来评估化学混凝。事实证明，这比酸性条件（pH值类似于4）和低凝结剂水平（4 mg-Al l(-1) 是能够有效破坏胶体粘土颗粒稳定的最小值）下的电凝更有效。在中等明矾剂量水平(4-20mg-A11(-1))下观察到高效的凝固，其中等电点出现在pH值类似于7.8时。在间歇式电絮凝反应器中确定了三个操作阶段（滞后、反应和稳定），操作电流决定污染物去除率。在反应阶段出现的等电点处，发生最大的浊度降低，表明通过吸附机制发生聚集（与化学混凝情况下的电荷中和相比）。在稳定阶段，氢氧化铝的持续沉淀和浊度的降低表明了吹扫混凝机制。最高电流（2 A）在最短的时间内降低了污染物水平，30分钟后残留浊度为1%，但在最低电流（0.25 A）下实现了最高效率（以每添加单位铝去除的污染物计算）。 (C) 2002 Elsevier Science B.V. 保留所有权利。
A renewed interest in electrocoagulation has been spurred by the search for reliable, cost-effective water treatment processes. This technology delivers the coagulant in situ as the sacrifcial anode corrodes, due to an applied potential, while the simultaneous evolution of hydrogen at the cathode allows for pollutant removal by flotation. By comparison, conventional chemical dosing typically adds a salt of the coagulant, with settling providing the primary pollutant removal path. This paper provides a quantitative comparison of these two approaches based on turbidity removal associated with a clay pollutant. Chemical coagulation was evaluated via jar tests using aluminium sulphate (alum). This proved more effective than electrocoagulation under acidic conditions (pH similar to4) and low coagulant levels (4 mg-Al l(-1) being the minimum able to effectively destabilise the colloidal clay particles). Highly effective coagulation was observed at intermediate alum dosage levels (4-20 mg-Al l(-1)), where the isoelectric point occurred at pH similar to 7.8. Three operating stages (lag, reactive and stable) were identified in a batch electrocoagulation reactor with the operating current determining the pollutant removal rate. At the isoelectric point, which occurs during the reactive stage, the greatest turbidity reduction occurs, indicating aggregation by a sorption mechanism (compared to the charge neutralisation as in the case of chemical coagulation). During the stable stage, continued precipitation of aluminium hydroxide and a decrease in turbidity indicated a sweep coagulation mechanism. The highest current (2 A) reduced the pollutant level in the shortest time, 1% residual turbidity after 30 min, though the highest efficiency (in terms of pollutant removed per unit of aluminium added) was achieved at the lowest current (0.25 A). (C) 2002 Elsevier Science B.V. All rights reserved.