Primal Study Of Modification Of Eichhornia Crassipes Cellulose And The Adsorption Properties Of Its Product On Heavy Metals

Adsorption on copper ion by cellulose of Eichhornia crassipes and several other plants were studied. Two kinds of modification method were used to change the chemical property of cellulose, via compared the adsorption amount on copper, we selected a better modification method. Several important factors in the modification process were investigated. The best modification technique was got, and the product made under that technique had the biggest adsorption capacity. The adsorption properties of cellulose xanthogenate on copper were also investigated. At the last, the adsorption on five heavy metals with cellulose xanthogenate and the regeneration were studied. The main conclusions of this paper were listed below:1. Root and stem of Eichhornia crassipes had higher adsorption capacity than other raw plant materials. Reasonable coarse-fiber component, loosen structure and more carboxyl were the most important reasons.2. The product via modification with CS₂ had far higher adsorption capacity than that with citric acid, at the same time, the preparation method is more simply and need less time, is a kind of economical and time-saving modification method. Compared to the cellulose citrate, the adsorption on copper with cellulose xanthogenate is less effected by pH, under the low value, cellulose xanthogenate still had good adsorption effect on copper; The velocity of adsorption was quick; the concentration of the acid used for regeneration of the adsorbent was lower, not only the production cost was saved, but also the loss of the adsorbent in the regeneration was lower.3. The optimum conditions of the modification technique were 5g raw materials alkalized with NaOH for 90 min, and then esterified with 0.1～0.2 ml CS₂ for 90 min. at last reactived with MgSO₄. In this case, the product had the greatest adsorption capacity.4. The adsorption on copper with cellulose xanthogenate was effected by pH, the adsorption capacity on copper increased with the increased of pH from 1 to 4.5, and the greatest adsorption occurred in pH 4.5. The dynamics of adsorption could be described by first order kinetic equation (R²=0.9512). The velocity of adsorption was quick and there was just only 20 min for the process to equilibrium.5. Cellulose xanthogenate of Eichhornia crassipes has a high affinity for copper but a low affinity for sodium, so that sodium would not affected the adsorption on copper. But anions would influenced the adsorption on copper, NO₃^-have the biggest influence, and SO₄^2-have the smallest influence. 6. The powder of cellulose xanthogenate had bigger adsorption amount and higher adsorption velocity than the granule of that, but the practicality of the granule of cellulose xanthogenate was better. It can be used in the fast treatment of waste water.7. The removal efficiency of the four adsorption materials follow the order: stem (powder)＞root (powder)＞stem (granule)＞root (granule), when they used to adsorb single metal. The two powder materials can removed more than 95% of copper and more than 99% of Pb, Cd, Cr and Zn.8. The removal efficiency of the four adsorption materials also follow the order: stem (powder)＞root (powder)＞stem (granule)＞root (granule) when they used to adsorb mixed metals. And the removal efficiency for Cr, Cu and Pb were better than that of Cd and Zn.9. After three times regeneration, the four materials had almost the same removal efficiency, the average removal efficiency for Cd was 30%, Cr was 23%, Zn was 34%, but for Cu and Pb, the four materials had big difference, the stem (powder) had the best removal efficiency, the root (granule) had the worst removal efficiency, after three times regeneration, the adsorption materials lost a lot of weight, the loss ration of the powder materials was about 43%, and the granule materials was about 34%.