國際環境學科最具影響力的期刊ES&T（Environmental Science and Technology）在2008年8月刊載了同濟學馬魯銘教授關於難降解工業廢水控制的篇論文《Enhanced biological treatment of industrial wastewater with bimetallic zerovalent iron》，該期封面還登載了有關污水處理方法的照片。
Green iron Dec 4th 2008From The Economist print edition
Environment: Treating industrial wastewater with scrap iron can be a cheap and effective way to reduce pollution from factories
SCRAP conjures up visions of rusting junkyards on the wrong side of the tracks. But this image could soon be given a green makeover. Researchers have found that iron filings from factories can be a cheap and efficient way to clean up polluted water. Because such scrap is widely available, the idea could be particularly useful in developing countries.
The new approach is being used to treat wastewater in the Taopu Industrial District of Shanghai, which is home to many small pharmaceutical, petrochemical and textile factories that discharge water contaminated with dyes, phosphorus and nitrogen. The project, which began in August 2006, now treats about 60,000 cubic metres (about 13m gallons) a day of industrially contaminated water—which is about the volume of municipal wastewater that a small town generates.
Wei-Xian Zhang of Lehigh University in Bethlehem, Pennsylvania, and Luming Ma of Tongji University in Shanghai have been using the Taopu wastewater facility to test their methods of treating industrial wastewater using iron filings. Iron powder (technically called zero-valent iron by chemists to show that it has not oxidised) has been used to treat groundwater for more than a decade. It is used to remove dangerous substances such as trichlorethene (used in paint strippers and adhesives) and arsenic. But no one had tried using iron filings to treat water discharged from factories before.
The standard technique for treating wastewater is to pass it through a series of tanks containing biological agents, such as biofilms, bacteria and other aerobic organisms, that break down the contaminants in a few days. But this often does not work with water from factories, especially as it may contain synthetic compounds that are toxic and not biodegradable.
Dr Zhang had previously invented a method to clean groundwater and contaminated soil using iron nanoparticles. It was effective, but such nanoparticles are expensive: about 0 a kilogram, which can prohibit their use in developing countries. Dr Zhang, who did his undergraduate degree in Shanghai before moving to America, thought iron filings, which have a large surface area, might provide a cheap alternative. Scrap iron currently costs about 20 cents a kilogram in China. His idea was to treat industrial wastewater by passing it through the iron filings, and then treat it as municipal wastewater. The non-biodegradable industrial chemicals are attracted to the surface of the iron shavings, where they react by sharing electrons with the iron and become degraded. (The iron gets oxidised in the process.) Any biodegradable contaminants that remain are then neutralised by the second step.
Dr Zhang found that treating the iron filings with a solution of copper chloride increased their effectiveness (and put the cost up by only about five cents a kilogram). He teamed up with Dr Ma in Shanghai about five years ago. Using 40kg of scrap iron, they ran a prototype experiment which showed that the method worked. Then the full-scale treatment facility came into operation. It consists of ten parallel cells containing a total of 914,000kg of iron filings, all purchased locally. (The iron lasts about two years before it has to be replaced.) Some 80% of the water treated is industrial discharge.
Compared with biological treatment alone, big improvements have been recorded. The removal of nitrogen has gone from 13% to 85%; phosphorus from 44% to 64%; and colours and dyes from 52% to 80%. Given the success of the technique, Dr Zhang and Dr Ma have now been invited by several municipalities in China to help with the establishment of similar treatment centres. The two researchers are also working on a much larger treatment centre in Shanghai that can handle 100,000 cubic metres of wastewater a day. Dr Zhang hopes his method will open a new chapter in the treatment of industrial wastewater, not least because the vital ingredient is cheap and abundant.
