Study On Pre-adsorption Of Gas Field Wastewater By Modified Fly Ash

Natural gas is a kind of vital energy source which is in great demand in China.However,the extraction of natural gas is accompanied by a large amount of gas field wastewater whose composition is complex.The content of inorganic salts is high,which poses a great threat to the environment.However,conventional fenton oxidation had the disadvantages of high cost and sludge.As a simple and effective wastewater treatment method,the adsorption methods play an essential role in water treatment industry.The key points of this method are to find a wide range of sources,low-cost and effective adsorbents.In this paper,the modified fly ash is used as an adsorbent to pretreat wastewater from a gas field in Sichuan,with the comparing between new pattern of Fenton oxidation and traditional fenton test.In this paper,the influence of adsorption material types and particle size on the adsorption effect was investigated,and-0.074 mm ash residue was selected for acid-base solution impregnation modification.The results indicate that adding with 1mol/L HNO₃,the modified fly ash will gain a good adsorption effect.With analysis of the adsorbent under different modification conditions,it is illustrated that the modifier has a good effect on the pores,surface roughness and functional groups of the adsorbent.After modified with HNO₃,the internal pores and the surface roughness of the ash increase,while the surface area,pore volume and average pore dimeter go down.Meanwhile,the functional groups on the surface prospect,to form a reticulated silicate.The effects of adsorbent quantity,p H,temperature and adsorption time on COD removal rate were investigated.The results show that with the adsorbent quantity and the adsorption time increasing,the COD removal rates climb up and then tend to remain at a certain level.As p H and reaction temperature increase,the COD removal rate decreases gradually,and the adsorption conditions are optimized to remove,COD decreased from 6480.00 mg/L to 4454.73 mg/L,the adsorption efficiency can be up to31.25%,.Adsorption kinetics study found that the adsorption process is more in line with the quasi-secondary adsorption rate equation,which indicate that the adsorption was affected by chemistry.None of the fitted lines passing the origin by Webber-Morris internal diffusion model fitting showed that intra-particle diffusion is not the only rate-limiting step to control the adsorption process.Comparison of Fenton oxidation conditions of water samples before and after adsorption show that the raw water is directly oxidized by Fenton and the COD can be reduced from 6000.00 mg/L to 3819.00 mg/L with a removal rate of 36.35%.Fenton combined adsorption pretreatment,after treatment COD reduced to 2744.96 mg/L,the total removal rate of raw water 61.54%.Analysis of water samples before and after experiment by gel chromatography and three-dimensional fluorescence spectroscopy show that in the treated sample,the molecular weights of the organic matter after adsorption and oxidation treatment was reduced from 7804 Daltons to 5381 Daltons,and the content of humic acid organic matter that was difficult to biochemical treatment was significantly reduced,and the fluorescence could not be detected,conducive to biochemical reactions.This paper contains 45 figures,11 tables and 102 references.