| Water pollution has become a serious problem with the development of industrialization. Nowadays, the water in rivers and lakes has been polluted which resulted in great reduction of waster utility as well as the shortages of water resource. This generated the adverse effects on the implementation of sustainable development strategy in China. In order to promote the national sustainable development strategy, it was urgent to develop an economical, environmental-friendly and efficient treatment methods for various pollutants in wastewater.Linear alkyl benzene sulfonate (LAS) is a kind of important anionic surfactant, which is widely used as formulation components of synthetic detergents, cleaning agents, decontamination powder and so on. The annual total consumption of LAS in our country is more than 1 million tons. Due to the extensive application of LAS, a lot of water resources are contaminated every year, and it may take 20-22 days to degrade the LAS in natural environment. Furthermore, LAS could cause large toxic effects on animals and plants because of its long-term accumulation in environment and organisms. LAS is the most common and representative organic pollutant in the environment, and its environmental behavior and effects have attracted more concern. In our country, there are many kinds of natural zeolite with abundant resources, low cost, a variety of special physical and chemical properties. Zeolite has been widely used in water treatment and catalysis. However, the pores and channels were easily blocked by finely divided particles, resulting in a poor level of interconnected channels, and the aluminium-oxide polyhedron structures in zeolite are negatively charged and highly hydrophilic. So the nature zeolite often needs to be modified to meet the requirements for the treatment of pollutants. In this work, the removal of LAS was studied by adsorption of the modified zeolite and packed column of biological zeolite in waste water, the details are as follows:1. Research on the analysis and experimental method. The determination of LAS and Cetrimonium Bromide (CTMAB) in water were studied by UV spectrophotometr-ic and the first derivative spectrometry, the effects on the determination of the absorption wavelength, measurement time. Moreover, the effect of solution pH, temperature, recoveries, stability, detection limits, and the interference measurements of metal ions on the determination also discussed. The results showed that when the concentration of LAS was between 0-60.00 mg/L, the linear equations was y= 0.0329x+0.0835, R2= 0.996, the average recoveries were between 95.35%-96.74%, the relative standard deviation RSD (n= 6)≤1.32%, and the detection limit was 0.36 mg/L; when concentration of CTMAB was between 0-40.00 mg/L, the linear equations was y= 0.0022x+0.0006, R2= 0.999, the average recoveries were between 96.60%-97.63%, and the relative standard deviation RSD (n= 6)≤0.31%, the detection limit was 0.18 mg/L. The direct spectrophotometry determination of LAS and the derivative spectroscopy determination of CTMAB were operated simply, tested rapidly, provided with high precision, good stability, and low detection limit, but coexistence of LAS and CTMAB was of great interference to the determination methods. Therefore, the ESI-MS methods were investigated for the determination of CTMAB and LAS. The results illustrated that when the concentration of LAS and CTMAB was between 0.050-5.00 mg/L, MS linear equations were y= 979.13x+ 374113 and y= 850.53x+413499, both R2 are 0.996, in which the linear relationship was good, but it needs higher requirement for equipment and operation. The determination methods in this study can be used in the modifying of zeolite and the quantitative determination of LAS and CTMAB in the process of wastewater treatment.2. The study on the modification of the natural zeolite. The Zeolite P (PZ) was prepared by the natural clinoptilolite (Z) that was treated with lye, then the zeolite (Z and PZ) were modified by CTMAB to get the organic modification of zeolite (ZC and PZC). The zeolites were characterized by SEM&EDS, XRD etc to study the differences in micro structure and properties of zeolites before and after modification. The results indicated that the spherical particles on PZ surface distributed more regularly after the alkali treatment. With the silica-alumina ratio decreased, there was no change on the phase composition, but the net charge of zero point, the specific surface area as well as and pore size increased. After modified with CTMAB, the surface of PZC and ZC were covered with a layer of gray substance, and the results of IR test displayed strong absorption peak of-CH2 and-CH3 which generated by symmetric and antisymmetric stretching vibration of CTMAB at 2920 cm"1 and 2850 cm-1, while there was no significant peak for the natural zeolite at the same position. The content determination and elemental analysis confirmed the content of CTMAB in zeolite. The ZC was loaded 12.25 mg/g and the PZC was loaded 25.31 mg/g. A serial of characterizations proved that the micro structure and properties of PZ changed and PZC had more loading capacity though both ZC and PZC had been loaded with CTMAB.3. Surface adsorption free energy, dispersive component and acid-base interaction free energy of zeolites were investigated by inverse gas chromatography (IGC) with the chloroform and other small polar molecules and non-polar saturated straight chain alkane molecule as the probe molecules. The results showed that the adsorption free energy of normal octane increased from 18.88 kJ/mol to 21.24 kJ/mol after nature zeolite modified with alkali, while adsorption free energy dropped to 15.90 kJ/mol when the nature zeolite was modified by CTMAB at 383 K. Research showed similar trends at different temperatures for other probe molecules. The dispersion energy of nature zeolite was 34.59 mJ/m2 at 383 K, while it increased to 38.95 mJ/m2 after alkaline treatment and decreased to 27.90 mJ/m2 after CTMAB modification. The weak acid sites of the natural zeolite was enhanced after alkaline treatment and the acid sites were decreased after CTMAB modification. Through determining the surface properties of Z, P, ZC and PZC, it illustrated that moreadsorption free energy, high dispersion energy and strong acid sites could induce more CTMAB loading on the surface of zeolite, and more CTMAB covered on the surface of zeolite resulted in a lower adsorption free energy, dispersion energy and a weaker acid sites.4. The adsorption experiments of LAS onto the ZC and PZC were performed and the adsorption kinetics, thermodynamics, the adsorption mechanism were also discussed. The results indicated that the adsorption achieved equilibrium after 4 hours, the optimized adsorption capacity was at the temperature of 20℃ and the pH was 2, the adsorption capacity were 9.12 mg/g and 23.07 mg/g,while it exhibited poor performance of the adsorption with increase of the temperature. The adsorption process was well fitted with preudo-second order kinetic equation and Langmuir isothermal adsorption model with the adsorption capacity of 27.10 mg/g and 12.66 mg/g, it illustrated that the adsorption process was described primarily for the monolayer and chemical adsorption, PZC had better thermodynamics performance and its adsorption rate constant was larger than ZC. The apparent activation energy was 53.66 kJ/mol in the process of PZC adsorbing LAS, and the adsorption Gibbs free energy was 6.22 kJ/mol. The spill of CTMAB was about 0.31 mg/g during adsorption of LAS by PZC, which was one-thirds of ZC. The modified zeolite has an important application in LAS wastewater treatment in the foreground.5. The treatment of LAS wastewater was studied with the self-made SBR system of laboratory. The SBR processing condition was optimized to discuss the degradation kinetics. According to the promotion of metal ions on degradation of SBR, the natural zeolite was modified with the metal ion, and the zeolite packed column was prepared for the LAS wastewater treatment. The processing conditions were investigated and the treatment model of LAS in wastewater by zeolite packed column was discussed. The results showed that the LAS removal rate was 82.16% when the initial concentration was 10.00 mg/L in 5 L activated sludge. The optimum aeration rate was 0.2 m3/h, solution pH of 7 and degradation time of 14 h. Mn2+ and Na+ has significantly improved the ability of activated sludge to degrade LAS. the removal rate reached 90.94% and 85.44%, respectively. The degradation kinetics equation was v=8.06×10-5×S/(0.81+S). The optimum height of filter layer filled with zeolite was 150 cm with a filtration rate of 3.02 mL/min, and the removal rates of the natural zeolite and modified zeolite packed column were 51.60% and 72.10% in simulated wastewater with the concentration of LAS 10.00 mg/L. By determining the kinetic model parameters of the LAS wastewater treatment by zeolite packed column, the treatment models were as follows: The results provided a theoretical basis for the process design of LAS wastewater treatment. |
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