Synthesis Of High Silica Zeolite Catalyst From Fly Ash And Purification Of Coal Chemical Wastewater

In this paper,fly ash was treated to meet the requirement of HZSM-5 zeolite synthesis by grinding,screening,calcination?alkali melting?,acid leaching and other pretreatments.Then,the effects of crystallization temperature,reaction time,template type and dosage,pH and Si/Al molar ratio on the synthesis of target zeolite were explored with chemical reagents as raw materials.Then,HZSM-5 zeolite was successfully synthesized by the pre-trated fly ash.Based on the adsorption data of HZSM-5 synthesized under different conditions,the better catalyst carrier was determined by principal component analysis method,and the Cu/HZSM-5 catalyst was prepared by precipitation/calcination method.Phenol,quinoline and indole were used to simulate coking wastewater.The optimum loading of copper was investigated and the catalytic purification of refractory organic compounds was studied by experiments.Finally,a better catalyst was used to treat the actual coal chemical wastewater.The main conclusions are as follows:Higher acid dissolving temperature can promote the removal of impurities from fly ash and increase the Si/Al ratio.Alkali melting can destroy the crystal structure of quartz and mullite in the fly ash and significantly increase the Si/Al ratio of acid pickling products.Synthesizing HZSM-5 zeolite by chemical reagents shows that lower template content and basicity,higher crystallization temperature and longer crystallization time are beneficial to the growth of HZSM-5.The optimum synthesis conditions of HZSM-5 are:solution pH about 11,hydrothermal temperature 180°C,crystallization 48 h,template dosage n?TPABr?/n?SiO₂?=0.1.Under these conditions,powder X-ray diffraction?PXRD?proves that the synthesized product of fly ash is HZSM-5.Scanning electron microscopy?SEM?shows that the zeolite is hexagonal prism.Infrared analysis?FTIR?shows that it has a typical HZSM-5 backbone structure.The results of thermal analysis?DSC/TG?show that the HZSM-5 synthesized by fly ash has good thermal stability.The specific surface area?BET?analysis shows that the zeolite has a large specific surface area.The adsorption experiments of HZSM-5 indicate that it had strong adsorption capacity for quinoline,indole and phenol in aqueous solution,and the sequence is quinoline,indole and phenol.The principal component analysis of adsorption data show that HZSM-5 synthesized from molten fly ash has better comprehensive properties when the mass ratio of Na₂CO₃ to fly ash is 1.2.The prepared catalyst has obvious diffraction of CuO,and its diffraction intensity increases with the increase of loading,but the specific surface area decreases gradually.Under the conditions of oxygenation and heating?temperature range 80²00°C?,liquid chromatography analysis shows that Cu/HZSM-5 catalyst could destroy the molecular structure of phenol,quinoline and indole.Liquid chromatography and COD analysis show that 10%loading of Cu/HZSM-5 has better purification effect.Extending reaction time,increasing dosage,decreasing organic concentration and appropriately lowering reaction temperature are all beneficial to the purification of organic compounds.The catalyst has a COD removal rate of about 50%for the actual coal chemical wastewater which contains more than 50 g/L salt.In conclusion,this study can provide useful reference for the utilization of fly ash and the treatment of refractory wastewater to our country.