| Dyeing wastewater, featuring on its massive drainage, high organic concentration, high colourity and inorganic salt, complex ingredients, great difficulty to biodegradae and remove colourity and the like, has been a problem in the field of disposing industrial sewage. One of which is the treatment of anion dyeing wastewater due to its good water solubility and physical and chemical characteristics.In this paper, two kinds of anion dyes: azo Acid Chrome Blue K and heteroatomic Eosin Y were selected as targets. Layered double hydroxides and their calcined product were synthesized as the sorbents. This work deals with the adsorption of two anionic dyes contaminants by the sorbents. The affecting factors, including calcining temperature, reaction time, pH value, adsorbent amount, reaction temperature and initial concentration etc, were investigated in the treatment of the anion dyeing wastewater. Simultaneously, this paper also tests the rycycling usage of calcined layered double hydroxides at 500℃ and their physical and chemical mechanism, dynamics, and adsorption isotherms.The hydrotalcite [Mg3Al(OH)8]2CO3·xH2O (Mg3Al-LDH) was prepared by the coprecipitation method at low supersaturation. The prepared samples were calcined in air at different temperatures to obtain calcined magnesium aluminum oxide (Mg3Al-CLDH) . The structures of Mg3Al-LDH and Mg3Al-CLDH (500℃ ) were characterized by X-ray diffraction determination, infraed spectra and transmission electron microscopy. The results show Mg3Al-LDH has single phase, fine crystallinity, obvious layer structure and well-distributed crystal particles. In the calcined samples at 500℃ , a porous system has been developed during the evolution of CO32- as CO2. It can be concluded that used sythesis method is scientific and efficient.It was found that Mg3Al-LDH had the same low sorption capacity for azo Acid Chrome Blue K and heteroatomic Eosin Y. In the same conditions, the maximal removal rate was 47.98% for Acid Chrome Blue K and 15.78% for Eosin Y. The dyes were adsorped on Mg3Al-LDH by the anionic exchange mechanism. This could be explained that C16H9N2O12S33- and C20H6O5Br42- had the steric hindrance by theirbulky size and the carbonate anion had the high affinity of the hydrotalcite layer.The influnce of calcining temperature on removal rate by Mg3Al-CLDH was examinated. And the results indicated that Mg3Al-CLDH (500℃) had the highist sorption capacity, the removal rate 96.62% for Mg3Al-CLDH (500℃) and 83.13% for Eosin Y, whereas Mg3Al-CLDH at the other temperatures had the lower removal rate.In the same conditions, adsorption of Acid Chrome Blue K and Eosin Y respectively on Mg3Al-CLDH (500℃) is much more favoured than on Mg3Al-LDH, in which the removal rate on Mg3Al-CLDH (500℃) is 50% more than that on Mg3Al-LDH for Acid Chrome Blue K after adsorption for 3 hours; the removal rate 80% for Eosin Y after adsorption for 2 hours.The adsorption experiments show that the appropriate conditions determined by the experiments are as following: Mg3Al-CLDH ( 500℃) , [CLDH]=60mg/L,t=2h, pH=3.6,T=25℃ when the initial concentration of the Acid Chrome Blue K dye is 100mg/L ; Mg3Al-CLDH (500℃) , [CLDH]=100mg/L,t=1h, pH=2.5,T=25℃ when the initial concentration of the Eosin Y dye is 100mg/L. At the same time, the removal rate is 99.88% and 99.51% respectively.It was found that the removal ratio for Acid Chrome Blue K was above 90% and 76% for Eosin Y when the fourthly recycled Mg3Al-CLDH (500℃) were used as adsorption material,suggesting that Mg3Al-CLDH (500℃) had great potential application in environmental anion pollution mediation.The structure of Mg3Al-CLDH (500℃) absorbing two anion dyes was characterized by X-ray diffraction determination and infraed spectra. It was found Mg3Al-CLDH (500℃ ) absorbed anions from solution through the reconstruction of their layered structure because of their special "structure memory effect". But their structure was only resumed partly and some CO32- and OH- anions were adsorbed into the l...
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