| The dyes wastewater has the characteristics of large quantity, strong toxicity, deep color, high concentration of organic and inorganic salt and it is difficult to be biodegraded. At present, the treatment methods for dye wastewater include physical method, chemical method and biological degradation method. In the various methods, adsorption has been recognized as a practical technology because of its high efficiency, simple operation and low energy consumption. Chitosan is cheap, easy to obtain, biocompatible, non-toxic and biodegradable. Numerous studies have demonstrated that, chitosan is a natural polymer material with excellent performance, and can be used as the adsorbents for water treatment. As the adsorption material, chitosan has the shortcomings of easy to loss, low mechanical strength, and can not be regenerated in practical application, which limite the practical use of chitosan. However, the modification for improving the ability of the acid and alkali resistance, mechanical strength, is the better way to overcome the use of bottleneck.On the one hand, this research first used glycine hydrochloride ionic liquid aqueous solution as reaction medium, ceric ammonium nitrate (CAN) as an initiator, p-Quinone as resistance polymerization retarder, no external crosslinking agent, to preparae cross-linking copolymerization (CS/AMPS) of 2-acrylamide-2-methylpro panesulfonic acid (AMPS) and chitosan. The results showed that, reaction temperature, reaction time, initiator content, monomer amount and inhibitor had significant influence on the grafting rate. At the reaction temperature 60℃, reaction time 2.5 h, n(CAN):n(CS)=1.5, n(AMPS):n(CS)=3.5, the mass percentage of inhibitor was 0.06%, CS/AMPS had the best performance. SEM found CS/AMPS had smooth surface, was regular spherical with about 2μm particle diameter. TGA showed copolymer microspheres had high thermal stability. In addition, CS/AMPS had good resistance to acid and alkali and swelling properties.0.02 g of micro spheres for the removal of the crystal violet solution of 20 mg·L-1 could reach more than 94%.On the other hand, this research also made use of ionic liquid-glycine hydrochloride ([Gly]C1). And then quaternary ammonium salt of chitosan (CS/EPTAC) was prepared by 2,3-epoxypropyltrimethyl ammonium chloride(EPTAC) and chitosan(CS) in the aqueous solution of [Gly]Cl ionic liquid. The results showed that the reaction temperature, reaction time, reactant ratio, ionic liquid concentration were the main factors affecting the degree of substitution. In a certain range, the degree of substitution was higher. Experiments of reuse of ionic liquids showed that, under the same conditions, three times degree of substitution of the product was more than 120%. Using ionic liquid as solvent, can not only be used in homogeneous reaction, but also can reduce the reaction temperature (30℃), shorten the reaction time (3 h), reduce the proportion of reactants (m(EPTAC):m(CS)=1.5:1).Further, using CS/EPTAC as shell, Fe3O4 as nucleus and glutaraldehyde as cross linking agent, CS/EPTAC/Fe3O4 was prepared through inverse suspension. And using the adsorption removal rate of methyl orange as the study index, effect of amount of surfactant, degree of substitution of CS/EPTAC, the molar ratio of CS/EPTAC and Fe3O4on the adsorption properties of the agent was studied. The structure and properties of CS/EPTAC/Fe3O4 were characterized by SEM, FTIR, TGA and saturation magnetization. The results show that, compared to the chitosan magnetic particles, quaternized chitosan greatly improved the adsorption rate and adsorption effect of anionic acid dye. SEM results showed that magnetic particles were spherical and spheroidal regular spherical, and particle size was uniform, was about 300 nm. Through the analysis of FTIR and TGA confirmed that Fe3O4 particle was in the sorbent. CS/EPTAC/Fe3O4 saturation magnetization of 11.04 emu·g-1 was decreased compared to Fe3O4 saturation magnetization of 74.3 emu·g-1, But it still had good magnetic properties, and it was helpful to solid-liquid separation.Using CS/EPTAC/Fe3O4 as adsorbent, the adsorption effects of five acid dyes, methyl orange (MO), orange G (OG), acid red 1 (AR1), xylenol orange (XO) and alizarin red (AR) were studied. The results showed that, CS/EPTAC/Fe3O4 had good adsorption capacity for five kinds of dyes. The removal rate decreased with the increase of pH value, and had the maximum value under the condition of pH=3.0. And the salt concentration could reduce adsorption of five acid dyes on the adsorbent. The studies of adsorption isotherm, adsorption kinetics and thermodynamics found: chemical and physical adsorption existed at the same time in the adsorption of five kinds of dyes, and the adsorption process is a favorable adsorption. The maximum adsorption capacities were calculated as 380.39,781.55,537.40 and 992.61mg·g-1 by Langmuir equations. The adsorption kinetics of five kinds of dyes was in line with pseudo-second order kinetic model. And study on adsorption thermodynamics showed that the adsorption of five kinds of dyes was spontaneous exothermic process. Saturated CS/EPTAC/Fe3O4 could be desorbed using 20% (W/V) NaOH solution. Adsorbent recycling six times, removal rate still reached 99%. Compared with activated carbon, CS/EPTAC/Fe3O4 magnetic dsorbent had fast separation performance and easy regeneration when reaching the near adsorption effect.Selecting azo dye AR1, triphenylmethane dyes XO and anthraquinone dye AR, and using different kinds of binary and ternary system as subjects, we investigated the competitive adsorption of various dyes on CS/EPTAC/Fe3O4. The results showed that, with the increase of adsorbent dosage, the concentration of AR decreased the fastest, and then AR1, finally XO. The spatial effect and characteristics of groups of dye was the factors affecting the adsorption order. Scatchard research showed that different dyes had stage characteristics at high concentration and low concentration range. Among them, there were two kinds of acting force between AR1 or XO and magnetic particles, and two forces was the mutual inhibition. However there were three different forces between AR and magnetic particles, which was promote each other. |
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