Font Size: a A A

Syntheses And Application Of Modified Chitosan Adsorbents In Treatment Of Heavy Metal Wastewater And Contaminated Soil

Posted on:2015-09-17Degree:MasterType:Thesis
Country:ChinaCandidate:N N WuFull Text:PDF
GTID:2181330422482305Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
Chitosan has been one of the most popular adsorbents for the removal of heavy metalions and has been widely used in wastewater and contaminated soil treatment. Chitosanmolecule contains large amounts of amino and hydroxyl groups and can excellently interactwith heavy metal ions in solutions through physical and chemical adsorption, such ashydrogen bond, salt bond, chelate, and others. However, it is difficult to directly apply the rawchitosan for removal of metal ions in wastewater treatment because of its disadvantage suchas swelling, solubility in acidic conditions, and unsatisfying mechanical property. Toovercome these problems, physical or chemical modifications of chitosan have been widelycarried out. In this work, the chitosan-based adsorbents were synthesized and their adsorptionproperties were also investigated. The details were showed as follows:(1) A novel glutaraldehyde-thiosemicarbazone-chitosan adsorbent (GT-CTS) wasprepared under microwave irradiation. The chemical structure of GT-CTS was characterizedby infrared spectra analysis, thermo gravimetric analysis, element analysis, scanning electronmicroscope analysis and X-ray diffraction analysis. The Cr(VI) adsorption behavior on theprepared GT-CTS had been studied under various conditions such as pH, amount of adsorbent,temperature, contact time, initial concentration of metal ions. Optimal uptake conditions ofCr(VI) were found at pH2, adsorbent dosage0.02g, temperature303K, contact time of6hours, and initial concentration of metal ions200mg.L-1, with maximum adsorption capacityof340mg·g1. In thermodynamics, the adsorption of Cr(VI) was exothermic (in term of ΔH)and spontaneous (in term of ΔG) process. Meanwhile, the adsorption process should bepredominantly chemical (ΔHa≥40kJ.mol-1). And in kinetics, the adsorption followed thepseudo-second-order kinetics.(2) The N-Maleoyl chitosan adsorbent (MA-CTS) was synthesized via reaction betweenchitosan and maleic anhydride, under water bath. The structure of MA-CTS was characterizedby micrograph analysis and infrared spectra analysis. The effects of various variables, such aspH, adsorption time and initial concentration, on the adsorption of Pb2+by MA-CTS wereinvestigated. The maximum adsorption capacities for Pb2+, with initial concentrations of0.02mol.L-1at pH5, was595mg.g-1. And in kinetics, the adsorption followed thepseudo-second-order kinetics.(3) The water-soluble chitosan-based adsorbent (CTS-AA) was synthesized via Michealaddition reaction between chitosan and acrylic acid under microwave irradiation. Thechemical structure of CTS-AA was characterized by1HNMR analysis and element analysis. The adsorption of CTS-AA on Pb2+, Cr(Ⅵ) and Cu2+in heavy metals contaminated soil wasinvestigated. The results demonstrate that CTS-AA had higher adsorption capacity. Theremoval rate for Pb2+, Cr(Ⅵ) and Cu2+were93%,80%,65%, respectively.The above chitosan derivatives were prepared and had higher adsorption capacity forheavy metal ions from wastewater or contaminated soil. These modified chitosan adsorbentswould have potential applications in wastewater or contaminated soil treatment.
Keywords/Search Tags:chitosan, modification, heavy metal ions, adsorption, soil
PDF Full Text Request
Related items