Chitosan-Bentonite Composite For The Removal Of Tartrazine, Malachite Green And Copper (Ii) From Aqueous Solution
Loading...
Date
2011-01
Authors
Md Ariff, Noorul Farhana
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Adsorption of tartrazine, malachite green (MG) and copper (II) ion from aqueous solutions by chitosan-bentonite composite (CCB) beads was investigated. CCB beads was prepared by dissolving chitosan with 5 % acetic acid. Bentonite was then added into the mixture and left overnight. The beads were then cross-linked with epichlorohydrin (ECH) solution before ground, dried and used for the adsorption studies. CCB beads were characterized by Fourier transform infrared (FTIR) spectroscopy in order to determine the functional groups, scanning electron microscopy (SEM) for the information of surface morphology, Brunauer-Emmett-Teller (BET) surface area measurement, Barrett-Joyner-Halenda (BJH) pore size distribution analysis and X-ray diffractometry (XRD) in order to obtain the information regarding the crystallinity. Solubility and swelling tests were carried out to determine the stability of CCB beads in acid solution, basic solution and distilled water. Besides, the value of pH of aqueous slurry (pHslurry) and pH of zero point charges (pHZPC) were also determined in this study. The amount of adsorbates adsorbed were influenced by initial pH of the solution, stirring speed, adsorbent dosage, contact time and initial adsorbate concentration. These were studied in batch adsorption study. Three types of kinetic model were implemented to the experimental data which were pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. Based on the kinetic study, pseudo-second-order models agreed well with the experimental data for all adsorbates. On the other hand, three isotherm models were used in isotherm study; Langmuir, Freundlich and Dubinin-Radushkevich isotherm model. Tartrazine, MG and copper (II) ion fitted well with Langmuir model compared to Freundlich model. Based on the calculation, the maximum adsorption capacity for tartrazine were 250.0, 277.8 and 294.1 mg g-1 at 300, 310 and 320 K respectively. At the same temperatures, 434.8, 555.6 and 2500.0 mg g-1 of MG and 181.8, 434.8 and 82.0 mg g-1 of copper (II) ion were adsorbed onto CCB beads. Adsorption of both types of dyes were due to chemisorption while the adsorption of copper (II) ion was by ion-exchange. From the temperature study, the adsorption of tartrazine, MG and copper (II) ion onto CCB beads were found to be exothermic in nature and occur spontaneously. Desorption tests were carried out at different concentrations of EDTA, H2SO4 and NaOH solutions. Only copper (II) ion could be desorbed from CCB beads by using these desorbing agents but not for tartrazine and MG.
Description
Keywords
Adsorption of tartrazine, malachite green (MG) and copper (II) ion , from aqueous solutions by chitosan-bentonite composite (CCB) beads