| dc.description.abstract | Abstract
Traditionally, there are a lot of chemical and physical methods to remove heavy metal ions from industrial sewage. Due to the variety of industrial effluent, it is very difficult to get good removal efficiency with non-expensive. Presently, many studies devote to develop low cost and reusable biosorbent to get rid of harmful substance in the solution. Fruit peel principally consists of cellulose, hemi-cellulose, pectin substances and other low moleculear weight compounds. As the active binding sites for metals are supposed to be functional groups of hydroxyl and carboxyl in cellulose. Chemical modification has shown great promise in improving the cation exchange capacity due to the increase of functional groups.
This study use orange peel, banana peel and lemon peel as the raw materials to carry out some batch experiments. The experiments include extract cellulose from peels, effects of different chemical modification on peel surface and immobilized cellulose by using Ca-alginate to produce many kinds of biosorbents. The preparation of the biosorbents and its biosorption behaveiors of Cu2+, Pb2+, Zn2+, Ni2+ and Cd2+ were studied.
After peel surface chemical modification and extract cellulose from peels, the adsorption capacities of five heavy metal ions have increased compared to raw peels. The higher of carboxyl group content, the better adsorption capacities it is. It shows that the carboxyl group content will influence the adsorption capacity. The FTIR spectra showed that there are carboxyl groups and hydroxyl groups in biosorbents, which are able to react with heavy metal ions obviously in aqueous solution. It shows that cellulose provides carboxyl groups and hydroxyl groups, which have unshared pairs of electrons, and which can form coordinate linkages with metal ions. The adsorption capacities didn’t increase obviously by using immobilized biosorbents. It shows that heavy metal ions only coordinate with the function groups on Ca-alginate. The heavy metal ions adsorption are strictly pH dependent, and maximum uptake of heavy metal ions on different biosorbents are observed at pH range of 5.0-6.0. The pHpzc value of peel surface also influence the adsorption capacity. The Cu2+ and Ni2+ ions can coordinate with all active groups, so the biosorbents with cellulose have good adsorption capacity to Cu2+ and Ni2+. The Zn2+ coordinate preferentially with ligands containing N, P, and S donor atoms result in the biosorbent with cellulose don’t have good affinity with Zn2+.
Keywords: adsorption, cellulose, biosorbent, surface chemical modification | en_US |