Removal of Cadmium (Ii), Mercury (Ii) and Lead (Ii) by Rice Husk Carbon

K. Srinivasan* and N. Balasubramanian**

¹Department of Chemistry, College of Engineering, Salem II (India) ²Department of Chemistry, Indian Institute of Technology, Chennai 36 (India)

The carbon obtained by treatment of rice husk with concentrated sulphuric acid under a weight ratio of 4:3 (SRHC) showed a significant removal of Cd(II), Hg(II) and Pb(II) from aqueous solutions over the pH range of 2.0-7.0. However recovery of the above metal ions from SRHC were not satisfactory with KI and HCl. Subsequent modification was done on by carbon by washing SRHC with 1% lime slurry and 1% NaHCO3 separately to remove the residual acidity. The lime and bicarbonate washed SRHC showed about 99.8% removal of Cd(II), Hg(II) and Pb(II). Ions from aqueous solutions, when a liquid to carbon ratio of 10 is maintained, over the pH range 1.2-5.0. However, when KI and HCl solutions were used for regeneration of metal ions, lime treated SRHC showed significant leaching of lignin from the surface. From the bicarbonate washed material Cd(II), Pb(II) could be recovered to an extent of 99.0% with 2.5N HCl and Hg(II) to an extent of 8.0% by using 2% KI solution.

Removal of Cd(II); Hg(II) ; Pb(II); Rice husk; Carbon