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Research on the Absorption Property of Cu2+ and Cd2+ by Carboxymethyl-Chitosan

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Tutor: YeShengQuan
School: Guangdong Ocean University
Course: Aquatic Products Processing and Storage Engineering
Keywords: carboxymethyl chitosan,pineapple peel,compounds,heavy metalion,absorption
CLC: X703
Type: Master's thesis
Year:  2012
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Abstract:
Carboxymethyl chitosan (CMC) is a water-soluble derivative of the chitosancarboxylation, and it has unique properties, especially its excellent biocompatibility. Themassive generation of peel waste, which present a potential risk towards environment andecosystems in pineapple(Ananas comosus L.Merryl) processing. As the by-product of thepineapple processing, raw pineapple peel fiber was chemically modified. By making use ofmodified pineapple peel fiber(MPPF) which is used for the filler, two types ofcarboxymethyl-chitosan/modified pineapple peel fiber (CMC/MPPF) compounds wereprepared. The application performance of the two types of CMC/MPPF compounds for Cu2+and Cd2+were evaluated as adsorbent. This research will provide theoretical basis andsome technical advice for effective utilization of pineapple peel in developing novel heavymetal absorbents through the heavy metal adsorption experiment. The main resultsobtained were showed as follows:(1) Preparation and characterization of two types of carboxymethyl-chitosan/modifiedpineapple peel fiber (CMC/MPPF) compounds.Raw pineapple peel fiber after being specially treated was chemically modified withsuccinic anhydride in reflux reactor containing dimethyl sulfoxide at70℃, and thecarboxylic function group was introduced in the backbone of fibre. The modified pineapplepeel fiber has been successfully preparated by the this method. By making use of modifiedpineapple peel fiber(MPPF) which is used for the filler, non-crosslinked CMC/MPPFcompounds and crosslinked CMC/MPPF compounds(Ethylene glycol diglycidyl ether ascrosslinking agent) were prepared. It was found that the addition of MPPF to CMC madethe compounds materially denser and mechanically stronger by hydration rate and tensilestrength test. The results of Thermogravimetric Analysis(TGA) and FTIR showed thatcarboxymethyl-chitosan/modified pineapple peel fiber have good compatibility and astronger hydrogen bonding interaction.(2) Study on the absorption property of copper ion(Cu2+) by carboxymethyl-chitosan andtwo types of CMC/MPPF compounds.Cu2+adsorptions of carboxymethyl-chitosan and two types of CMC/MPPFcompounds well followed the pseudo second-order kinetics model and Langmuir model.The optimum pH values of carboxymethyl-chitosan and two types of CMC/MPPFcompounds for Cu2+removal exhibited at pH7,8and6respectively. The maximumadsorption capacity of carboxymethyl-chitosan and two types of CMC/MPPF compoundsfor Cu2+is42.12mg/g,60.64mg/g and41.73mg/g respectively. (3) Study on the absorption property of cadmium ion(Cd2+) by carboxymethyl-chitosanand two types of CMC/MPPF compounds.Cd2+adsorptions of carboxymethyl-chitosan and two types of CMC/MPPFcompounds well followed the pseudo second-order kinetics model and Langmuir model.The optimum pH values of carboxymethyl-chitosan and two types of CMC/MPPFcompounds for Cd2+removal exhibited at pH7,7and5.5respectively. The maximumadsorption capacity of carboxymethyl-chitosan and two types of CMC/MPPF compoundsfor Cd2+is93.80mg/g,95.69mg/g and92.73mg/g respectively.(4) The absorptive mechanism of the two types of CMC/MPPF compounds for Cu2+andCd2+.From these FTIR spectra it appears that carboxyl(-COOH), hydroxyl(-OH) andamino(-NH2) groups are possible involved in Cu2+and Cd2+binding to the two types ofCMC/MPPF compounds. As the main functional group, carboxyl(-COOH) group mayinteract with Cu2+and Cd2+on the non-crosslinked CMC/MPPF compounds. Amino(-NH2)group may interact with Cu2+, but both of carboxyl group(-COOH) and amino(-NH2) groupmay interact with Cd2+on the crosslinked CMC/MPPF compounds by FTIR analysis.The adsorption process is very complicated, being strengthened by coordinationcomplexation, ion exchange and electrostatic absorption for Cu2+and Cd2+adsorption.
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