Preparation Of Magnetic Adsorbents Via Electrostatic Layer-by-layer Assembly And Its Application In Removal Of Dyes From Aqueous Solution

Due to the rapid development of industry, synthetic dyes are widely applied in many industries such as textile printing, plastics, and paper etc. However, because of toxicity and carcinogenicity properties, dye effluent produced by industries brings about severe environment problem to human health and ecosystem. Most of dyes are resistant to oxidation and degradation, so adsorption method to remove of dyes seems superior to other method in wastewater treatment. The Layer-by-Layer assembly technique has been demonstrated to be a convenient and versatile method, which has been widely used in many practical applications such as drug delivery, catalysis and biosensing. In this paper, two kinds of magnetic adsorbent were designed and synthesized by Layer-by-Layer method. Moreover, the capabilities and mechanisms for adsorption of dyes were further investigated. The details are as below:(1) Two kinds of magnetic adsorbent were synthesized via Lay-by-Layer method: one adsorbent of Na-(CS/PAA)n/MPC was prepared by using chitosan(CS) and polyacrylic acid(PAA) as polyelectrolytes, and the other adsorbent of(ALG/PEI)n/MN was obtained by alginate(ALG) and polyethyleneimine(PEI) as polyelectrolytes. Moreover, the adsorbents were characterized by Fourier Transform Infrared spectroscopy(FT-IR)?Field Emission Scanning Electron Microscope(FE-SEM)?Thermogravimetric Analysis(TGA)?X-Ray Diffractomer(XRD) and Vibrating Sample Magnetometer(VSM).(2) The uptake capacity of methylene blue(MB) and crystal violet(CV) on Na-(CS/PAA)n/MPC increased linearly with the number of(CS/PAA) bilayer. As the representative of Na-(CS/PAA)n/MPC, the maximum adsorption capacity of Na-(CS/PAA)4/MPC was found to be 305.8 and 246.3mg g-1 for MB and CV at pH 8(25oC). The kinetics and isothermal model results suggested that adsorption mechanism was homogeneous monolayer chemisorption, and the number of deposited(CS/PAA) bilayer might have no significant effect on adsorption equilibrium time. The adsorption process of Na-(CS/PAA)4/MPC was endothermic nature, and it shows excellent reusability for adsorption of MB and CV.(3) The uptake capacity of acid orange 10(AO10) on(ALG/PEI)n/MN increased with the number of(CS/PAA) bilayer raise. The maximum adsorption capacity of(ALG/PEI)4/MN was 246.3 mg g-1 at pH 3(25?C). The kinetics and isothermal model results suggest that the adsorption of AO10 was homogeneous monolayer chemisorption process with an exothermic nature. Moreover, the results on reuse experiments showed that(ALG/PEI)4/MN was a potential recyclable magnetic bioadsorbent.