Formaldehyde is known to high school pupils in biology class as the chemical in which frogs and other small animals are preserved for dissection. In fact, it is widely used in industry, including the manufacture of adhesives and resins and the wood, paper and textile industries.
An antimicrobial agent used to kill Salmonella bacteria, it is used in the US to manufacture animal feed. But – considered to be one of the most problematic indoor pollutants – it is a carcinogenic pollutant that can penetrate our bodies by breathing it in, eating and drinking.
The discharge of these wastewaters into the environment is, of course, prohibited, so great efforts are taken to safely dispose of them. The removal of formaldehyde from water is essential to prevent contamination of groundwater and soil. However, since removing it from water is very expensive, some companies simply keep the contaminated water in barrels, waiting for the day that a satisfactory solution is discovered.
Now, researchers at the Technion-Israel Institute of Technology in Haifa have developed an innovative, patented technology to remove formaldehyde from water. The research was led by Dr. Adi Radian and doctoral student Yael Zvulunov of the Faculty of Civil and Environmental Engineering, in collaboration with Prof. Ayelet Fishman and Dr. Zohar Ben-Barak Zelas of the Faculty of Biotechnology and Food Engineering. The Technion study deals with the reversal of environmental damage from formaldehyde-polluted water created in industrial processes, and their findings were recently published in the Chemical Engineering Journal.
Radian completed her Ph.D. at the Hebrew University’s Faculty of Agriculture where she studied the use of modified clays to increase the adsorption (the process in which a solid holds molecules of a gas or liquid) of organic pollutants. She went on to complete a post-doctorate at the University of Minnesota, where she developed a gel that attracts and affixes bacteria that break down pollutants like fuel and pesticides. Three years ago, she returned to Israel and joined the Technion’s Faculty of Civil and Environmental Engineering.
The research team’s development is based on Montmorillonite clay, a natural mineral characterized by a very large surface are. One gram of this clay has a surface area of about 760 square meters. This feature gives the clay a rare adsorption capacity. The patent that the Technion researchers developed is based on processing the clay in a way that increases the adsorption as a thin film of formaldehyde.
The other major component in the new technology is a formaldehyde-degrading bacterium. Such bacteria have evolved in the Negev after many years of formaldehyde use for soil disinfection. This use has led to the development of formaldehyde-resistant bacteria, which are able to decompose the dangerous compound. To solve the problem of resilience, Negev farmers were helped by Fishman, who harnessed the bacteria in question for the present study. Ironically, the resilience that was damaging to farmers aided the development of the new Technion technology.
But the researchers first had to overcome a difficult technical problem –
the large amount of formaldehyde in the industrial wastewater kills the bacteria immediately. Thus, a protective system was needed for bacteria to survive and decompose the dangerous material.
The Technion researchers modified the clay using a polymer that changed the overall negative charge to positive. With this modification, the clay absorbs the formaldehyde and reduces its concentration. Bacteria that break down the substance are pre-attached to the material. After each cycle of formaldehyde decomposition, the material cleans itself for another round. The immobilized bacteria removed 15 times more formaldehyde than free cells over several cycles.
Radian suggested that the new technique could be relevant for other uses, such as adsorption and degradation of pesticides that threaten to contaminate groundwater.
