Removal of cadmium (II),mercury(II)and lead(II)by rice husk carbon

摘要

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 satisfacotry with Kl and HCl.Subsequent modification was donw on by carbon by washing SRHC with 1%lime slurry adn 1% NaHCO_3 separately to remove the residual acidity.The lime and bicarbonate wasthed 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.Hwever,when Kl 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 2.5 N HCl and Hg(II)to an extent of 8.0% by using 2% Kl solution.