STUDY ON THE HEAVY METALS ADSORPTION CHARACTERISTICS OF DEHYDRATED POWDER FORM OF HYDRILLA VERTICILLATA

The characteristics and mechanisms of heavy metals (Cu, Cd, Pb, Zn) adsorption by dehydrated powder of Hydrilla verticillata were studied in terms of pH values, reaction times and temperatures, and heavy metal ion concentrations. The results showed that with different pHs, reaction times and temperatures, the removal rates of heavy metal were as follows: Pb(Ⅱ)Cd(Ⅱ)Zn(Ⅱ)Cu(Ⅱ). When Langmuir model of heavy metals adsorption was applied, R2 would demonstrate a huge variation. But in Freundlich model, the R2 values exceeded 0.9 in most cases. It showed that the adsorption process of H. verticillata powders against heavy metals fitted the Lagergren second-order equation whereas the R2 values for first-order equation were less than 0.5. The results indicated that the mechanism of heavy metal adsorption by H. verticillata did not simply work on the mono-molecular layer level. The intra-particulate dispersal is the dominant process. As shown in the FTIR spectra, the peak shape of the powder did not change after adsorption with metal ions. Only absorption peaks of some functional groups shifted, such as hydroxy groups (3330～3400cm-1) , carboxyl groups (1400～1440cm-1), and acidamide groups (1620～1645cm-1) when they participated in the process of absorbing heavy metals.