Coal fly ash and alginate for the removal of heavy metals from aqueous solutions

The use of a basic coal fly ash in the removal of heavy metal ions (Cu2+, Cr3+, Ni2+, Zn2+, Cd2+ and Pb2+) from aqueous solutions has been investigated. It has been shown that the yields depend on ash dosage and metal concentration; the results are generally good and can be improved in some cases by pH lowering. As a matter of fact, fly ash gives a basic pH to the metal solutions; heavy metals are removed principally by precipitation and adsorption on ash particles. The addition of sodium alginate sometimes makes it possible to reach higher yields at a low ash dosage, but its effect must be carefully evaluated in the case of mixed ions.