Carbon shapes to treat water

Chemistry

The hydrosphere (total amount of water on earth) is composed of enormous amounts of water, of which about 97 per cent is saline and unfit for human consumption. About two per cent is present in the form of ice in the polar regions, and the water we use for potable, industrial and irrigation purposes is hardly one per cent. Sea water is of no use without treatment.

Even though there are many methods for desalination, membrane technology is the most economical and effective. Larger desalination units mainly function on membrane-based technology. But, the major drawback in any membrane is that after their usage for a certain period, minute particles or microbes deposit themselves in the pores, decreasing the efficiency of the membranes. This is termed as fouling (if microbes are involved, it is termed biofouling). Though many remedies have been reported for controlling biofouling, they have not proved to be effective.

Recently, engineers at Duke University have found that buckyballs hinder the ability of bacteria and other microorganisms to accumulate on the membranes used to filter water in treatment plants.

So, what are buckyballs?

A buckyball, or C60, is one shape within the family of tiny carbon shapes known as fullerenes. They have been named after Richard Buckminster Fuller, the inventor of the geodesic dome, because their shape resembles the famous structure.

The attribute of buckyballs to hinder bacteria and microorganisms to accumulate leads researchers to believe that coating pipes and membranes with these nanoparticles may prove to be an effective strategy for addressing one of the major problems and costs of treating water. “Just as arteries can get clogged and the flow of blood is affected, bacteria and other microorganisms can over time attach and accumulate on water treatment membranes and along pores,” said So-Ryong Chae, post-doctoral fellow at Duke’s environmental and civil engineering department. The results of his experiments were published in the Journal of Membrane Sciences.

The only other option to address biofouling is digging up the pipes and replacing the membranes, which can be expensive and inconvenient.” “Biofouling is viewed as one of the biggest costs associated with membrane-based water treatment systems,” said Claudia Gunsch, assistant professor of civil engineering at Duke’s Pratt School of Engineering and senior member of the research team.

According to Chae, the addition of buckyballs to treatment membranes had a two-fold effect. Treated membranes showed less bacterial attachment than non-treated membranes. After three days, the membranes treated with buckyballs had on average 20 colony forming units, the method by which bacterial colonies are counted.

Chae also found that the presence of buckyballs inhibited respiration, or the ability of the bacteria to use oxygen to fuel its activities. “This respiratory inhibition and anti-attachment suggests that the nanoparticle may be useful as an anti-fouling agent to prevent biofouling of membranes or other surfaces.”

Both Gunsch and Chae believe that since buckyballs are one of the most widely used nanoparticles, additional research is needed to determine if they have any detrimental effects on the environment or to humans. This is one of the many issues being studied at Duke’s Centre for Environmental Implications of Nanotechnology.