| 摘要: | 傳統上已有許多物化學方法來移除溶液中之重金屬，然而工業廢水的多樣性，要得到較佳金屬離子去除效率是非常困難且成本很高。目前已有許多研究致力於發展低成本、可再利用之生物吸附劑來移除溶液中有害物質。果皮中含有纖維素、半纖維素、果膠等物質，纖維素中含有大量氫氧基，金屬離子可鍵結在這些官能基上達到移除重金屬離子之目的。 本研究主要為利用果皮上之纖維素如：橘子皮、香蕉皮及檸檬皮等，利用純化纖維素、果皮表面之酸鹼改質與固定化技術，製備多種含纖維素生物吸附劑，希望藉由生物吸附劑來吸附溶液Cu2+、Pb2+、Zn2+、Ni2+、Cd2+五種金屬。 實驗結果得知果皮經純化以及酸鹼改質後，吸附量有大幅提升趨勢。Carboxyl group含量愈多，對重金屬吸附愈好，顯示Carboxyl group多寡會影響吸附量。由FTIR圖譜可看出羧基與氫氧基之吸收波峰都很大，在進行吸附後，羧基與氫氧基之吸收波峰明顯削減，顯示果皮之纖維素可提供羧基與氫氧基，重金屬可鍵結在官能基所提供之未共用電子對上，達到移除重金屬目的。利用固定化技術所製備出顆粒狀吸附劑，吸附量並未明顯提升，顯示金屬只鍵結在褐藻膠之官能基上。 實驗結果顯示pH =5~6時，吸附效果最好。而果皮表面pHpzc值，也會影響吸附量之一。含纖維素吸附劑對Cu2+與Ni2+吸附效果很好，由於Cu2+與Ni2+可與大多數有機官能基所提供之未共用電子對進行鍵結，顯示對有機物具有很強親和性； Zn2+較易與含S、N、P有機物提供之未共用電子對鍵結，本研究製備之含纖維素吸附劑上主要提供氫氧基與羧基導致對Zn2+吸附量不佳。 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 |
