Onion Waste Cleans Up Heavy Metals, Study

Onion and garlic waste could be used to mop up hazardous heavy metals, according to new research.

AsianScientist (Dec. 12, 2012) – Onion and garlic waste could be used to mop up hazardous heavy metals in contaminated materials, according new research published in the International Journal of Environment and Pollution.

Phytoremediation – taken from the greek word phyto for plant, and the Latin word remedium, meaning “restoring balance” – describes the treatment of environmental pollution through the use of plants that contain, degrade, or eliminate the contaminant material.

In this study, researchers from the GGS Indraprastha University in Delhi, India show how waste from the processing and canning of onion (Allium cepa L.) and garlic (Allium sativum L.) could be used to remove toxic elements from contaminated materials including arsenic, cadmium, iron, lead, mercury, and tin.

The team studied the influence of pH, contact time, temperature, and concentration of the different materials present on the clean up process.

They found that at 50 celsius or 122 fahrenheit, the efficiency of the clean-up process is largely dependent on the pH, and that a pH of 5 was optimal.

The process was also efficient; they were able to extract more than 10 milligrams of metals per gram of Allium material from a test solution containing five grams per liter of mixed metal ion solution, amounting to recovery efficiency of more than 70 percent. Absorbed metals were released into a collecting vessel using nitric acid and the biomass reused.

Maximal extraction was possible for lead, one of the most troublesome metallic environmental pollutants.

The researchers were successful in treating actual industrial effluents, suggesting the application of this method as a biological heavy metal filter for industrial-scale decontamination.

“The technique appears to be industrially applicable and viable,” the authors write. “This may provide an affordable, environmental friendly, and low maintenance technology for small and medium scale industries in developing countries.”

The article can be found at: Negi R et al. (2012) Biosorption of heavy metals by utilising onion and garlic wastes.

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Source: Inderscience Publishers; Photo: firexbrat/Flickr/CC.
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