| With the fast economic development, a lot of industrial wastewater have been discharged. Industrial and domestic waste were treated irregularly. Waste waters containing heavy metal ions were discharged by electroplating glass, leather, chemical industry, ceramics, paints and other industries each year. Moreover, heavy metals was also enriched easily through the food chain in vivo, and it is difficult to remove by itself, thus the health of plants, animals and people were threatened seriously. Therefore, the economic and efficiency management of the heavy metal pollution has become a growing topic of concern.Adopting monomer grafting and esterification, the modified peel cellulose CPP-PAM and CPP-SA were prepared with pomelo peel as the raw materials in this paper. Their structure were characterized by means of modern instruments. And effects on the adsorption of heavy metals cadmium was studied by the factors such as the temperature, solution pH and adsorption time. The absorbent activity to heavy metal Cd2+by modified cellulose was studied in terms of adsorption kinetics, isotherm adsorption and desorption experiment.The main results were as follows:1、After the Pomelo peel was prepared, the pectin, hemicellulose and lignin was removed.4-hydrated ceric ammonium sulfate as initiator, acrylamide was grafted to the peel cellulose, cellulose CPP-PAM was prepared. While taking pyridine as catalyst, the succinic anhydride was esterfied to the peel cellulose to prepare cellulose CPP-SA.2、The modified pomelo peel cellulose CPP-PAM and CPP-SA were characterized by XRD、FTIR and SEM. The results showed that Amide and hydroxyl functional group ware respectively introduced into the pomelo peel cellulose molecules3、The effects of the adsorption pH, temperature and time on the removal of heavy metal ions by modified pomelo peel cellulose CPP-PAM and CPP-SA were studied. The results showed that while the solution volume20mL, natural pH, adsorption time40min, adsorbent mass0.02g, temperature20-35℃, the adsorption capacity grew slowly with increasing temperature at first, then slowly declined, their adsorption capacity were highest at30℃. While volume of solution20mL, adsorption time40min, adsorbent mass0.02g. when pH range1-7, adsorption capacity gradually increased with the increasing of pH, their adsorption capacity were highest at pH7.4、The Cd2+adsorption kinetics and adsorption isotherm of modified peel cellulose CPP-PAM and CPP-SA were studied. The results showed that adsorption of the modified peel cellulose CPP-PAM and the CPP-SA on Cd2+were a fast and stable process. CPP-P AM adsorption reached equilibrium after40min, then the adsorption capacity changed by a trace amount; CPP-SA reached the adsorption equilibrium about40min. The sorption kinetics of Cd2+on CPP-PAM and CPP-SA followed pseudo-second-order sorption kinetics. Sorption equilibrium studies indicated that the bio-sorption obeyed Langmuir isotherm model. The maximum adsorption capacity of CPP-SA and CPP-PAM on Cd2+were131.4mg/g and148.7mg/g respectively. Adsorption capacity of the modified peel cellulose CPP-PAM was higher than that of modified peel cellulose CPP-SA.5、At the desorption experiment, the desorption rate on Cd2+of modified peel cellulose CPP-PAM was93.09%by using lmol/L hydrochloric acid.6、The adsorption mechanism of modified cellulose on Cd2+may be partly the result of the ion exchange and complexation, another may be a small amount of physical adsorption.7、The maximum adsorption amount of the modified cellulose CPP-PAM was higher than that of CPP-SA, maybe the molecular weight was higher and the spatial structure was more complex of CPP-PAM than those of CPP-SA, so it is easier to adsorb colloidal particles by forming bridging phenomenon by means of hydrogen bonds, ionic bonds and van der waals. and it is also easy to form two-electron shell, to exchange and adsorb the ions. |
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