| For the last few years, with the rapid development of dyeing and printing industry, the pollution from dyestuff is getting worse. As a consequence, it is sorely needed controlling the pollution from dyestuff. As is known to all, adsorption method has benificial advantages, such as, effective treatment, ease of operation, wide applicability, which was applied in the process of pollutants separation.. Silica gel is a kind of typical adsorption materials and shows the huge potential practical value in the aspect of pollutant treatment.However, owing to the larger particles size and uneven distribution, silica gel that was utilized in the controlling the pollution from dyestuff widely was restricted. Pectin is a family of complex heteropolysaccharides consisting of α-1,4-glycosidic linked D-galacturonic acid residues, which widely exists in plants and contains large amount of active groups such as carboxyl, hydroxyl. The pectin is usually used to adsorb the heavy metal pollutants in the water mostly. However, there is little research about application of pectin into alkaline cationic dyes adsorption.In this paper, a new kind of composite materials was prepared by modifying porous silica gel with pectin, and the alkaline cationic dyes adsorption property of composite materials was studied. The adsorption property of Silica gel was increased through modified by pectin,which used the molecule interact between active group in the pectin and silicon hydroxyl in the silica gel and incresed the action area of pectin and enhanced the mechanical stability of pectin.The new kind of adsorption materials(P-Silica gel) was prepared by modifying porous silica gel with pectin extracted from the waste pomelo peel. The preparation conditions of materials and the influence factors of adsorption property was investigated.The P-Silica gel was applied in the adsorption separation of methylene blue in the watrer.The main content of this paper is as follows:(1) The porous silica gel was obtained from ammonium chloride and sodium silicate by adding the surfactant. The materials were characterized by Fourier transform infrared(FT-IR) spectroscopy and fluorescence microscope. The effects of the Na2 Si O3 concentration, different kinds of surfactant, the concentration of surfactant, the amount of disperser ethyl alcohol on the adsorption properties of the porous silica gel were examined.The study showed the best condition as follows:the concentration of NH4 Cl was 1 mol/L, the concentration of Na2 Si O3 was 0.5 mol/L, concentration of CTAB was 0.1 mol/L, the amount of ethyl alcohol was 5%. The porous silica gel prepared in this condition showed the largest removal rate of MB and the best removal rate may reach 51%.(2) The pectin was extracted from the waste pomelo peel by acid hydrolysis. According to the orthogonal experiment, the optimum extraction conditions were ascertained: extraction temperature 95 °C, extraction p H 1.5,solid-liquid ratio 1:15, extraction time 60 min. In this condition, the extraction ratio of pectin was more than 5%. The degree of esterification to the extracted pectin was 67.1% measured by acid-base titration and the structure of pectin was characterized by Fourier transform infrared(FT-IR) spectroscopy.(3) The composite materials(P-Silica gel) was prepared by modifying porous silica gel with pectin.The materials were characterized by Fourier transform infrared(FT-IR) spectroscopy. Its application to Methylene Blue(MB) removal from wastewater was investigated by UV spectrophotometry. The adsorption property of P-Silica gel prepared by self-made silica gel and purchased silica gel HG was compared. The result showed that the adsorption property of porous silica gel was improved significantly after modified by pectin in the condition of the pectin with silica gel mass ratio of 1:2, and its adsorption capacity increased from 30.35 mg·g-1 to 41.33 mg·g-1. The adsorption property of P-Silica gel prepared by self-made silica gel was better than purchased silica gel HG.(4) The effects of the p H, the amount of P-Silica gel, the adsorption time, the temperature, the initial concentration of MB on the adsorption properties of P-Silica gel were examined. And the recyle of P-Silica gel was investigated through eluted by Deionized water, ethanol, hydrochloric acid. With the increase of the solution p H and temperature, the adsorption capacity of P-Silica gel adsorbing methylene blue was increased, and it was conducive for the adsorption of methylene blue in the alkaline conditions. The optimized adsorption condition was as follows: p H=7, the amount of P-Silica gel was 5 mg, the initial concentration of Methylene Blue was 12 mg·L-1. And the maximum adsorption capacity of P-Silica gel to Methylene Blue was 57.75 mg·g-1 at 50 oC. Kinetic studies showed that the adsorption kinetics illustrated the suitability of employing the pseudo-second-order kinetic model, which indicated that the process of P-silica gel adsorbing methylene blue was given priority to chemical adsorption. Adsorption isotherms showed that Langmuir model was more suitable for the experimental data fitting.The P-Silica gel eluted by ethanol showed the best effect of recyle using. The removal rates of MB were more than 90 % in the lake water samples and tap water samples with using P-Silica gel as adsorbent. |
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