School of Mechanical Engineering Seminar
Wednesday, August 3, 2016 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Remediation of soils that are heavily contaminated by Chromium and other heavy metals, using biodegradable chelating agents 

Zhanna Katz

MSc Student of Prof. Amos Ullmann, Prof. Neima Brauner

Contamination of soils by heavy metals is a worldwide recognized problem. Methods of remediation of such soils usually involve use of chelators. However, even the strongest chelators (e.g., EDTA, DTPA) are mostly unable to remove Chromium and are non-biodegradable.

We have developed a process that allows to efficiently remove hazardous metals, including large amounts of Chromium, using citric acid (CA) as a convenient, relatively strong, yet eco-friendly chelator. Particularly, CA was found to be efficient towards extraction of heavy metals Cd, Cr, Cu, Ni, Pb, and Zn from heavily metal-contaminated Tel-Nof sludge. The metal extraction process was optimized considering CA/sludge mass ratio, temperature, time, and pH. Also, essential metals like Ca, are mostly remained intact in the media at those conditions.  Search for reducing the required amount of CA was carried out, too. Particularly, a mixture of CA and DTPA was found to be very efficient, and even exhibited synergetic effect towards Cr extraction.

A study of CA recovery and reuse was also carried out. A number of salts that are able to precipitate heavy metal ions, was tested, and disodium sulphide was found to be the best reagent, that precipitates nearly 100% of all the CA-complexed heavy metals, but Cr (~15%). The CA recovery conditions are being optimized. By using the recovered chelator for metal extraction, the concept of the chelator recovery-reuse was proven to be feasible.

The present research is expected to contribute to the current soil remediation technologies with an emphasis on heavy metal-contaminated soils where Cr is present in significant amounts. In addition, the mentioned here developed and optimized processes will serve as a basis for the semi-industrial pilot project that is ongoing in our lab.