By Tony Giunta, PG, Director of Project Development
Zeolite, Mother Nature’s aluminosilicate mineral with amazing remedial characteristics, has been studied and utilized for millennia. But as civilization changes, so does its applications.

In my first article in this series, I presented preliminary results of zeolite’s effectiveness in capturing toxic metals leached from coal ash. Why specifically focus on coal ash? Because millions of tons of the stuff currently lie across the globe in conditions highly susceptible to releasing toxic metals into the surrounding environment. Those responsible for managing this waste would welcome a simple inexpensive way to minimize its metal-leaching potential.

Up to now, the United States Environmental Protection Agency has encouraged the re-use of coal ash by adding it to Portland cement and aggregate. Once cured, the resulting concrete has shown promise in effectively locking in those toxic metals.

The drawbacks are you either need lots of customers for all that concrete or a whole lot of space to store all those resulting concrete blocks. Literature studies also report that for maximum metal sequestration you need four parts of Portland cement for every one part of coal ash. With the high cost of Portland cement, this solution can be prohibitively expensive.

Enter Niles International Corporation’s (NIC) patented zeolite. Our research partner, XDD Remedial Solutions (XDD), has found that mixing just one part zeolite with one part coal ash achieved excellent metal sequestration. XDD also found that mixing NIC zeolite with coal ash and then adding this mixture to one part Portland cement concrete achieved exceptional results. As the saying goes, a picture (or in this case a chart) is worth a thousand words, so please review XDD’s summary of findings in the chart located in my LinkedIn article.

Based on these findings, Nobis Engineering, along with NIC, Remedial Technology Distributors (RTD) and XDD, has brought to the coal and power industries several options for substantially reducing metal leachate from coal ash. The simplest, least expensive and effective option would be to blend one part ash with one part NIC zeolite. The somewhat costlier but most effective approach would be to take the blended zeolite/coal ash and mix it with one part Portland cement to form a very stable concrete. With all that coal ash lying around, there’s a huge inexpensive feedstock just waiting to be utilized. Now if we could only find a project that will need a whole lot of concrete? Hmmm… wait, didn’t I hear about a big wall going up somewhere?!

back to all resources