Experimental Study On Preparation And Solidification Of Pb²⁺ In Fly Ash Base Polymer

With the improvement of the urbanization process,the improvement of the quality of life,and the rapid increase of urban domestic waste,there is great pressure on environmental protection.Traditional landfill and composting methods not only occupy a lot of land but also have a slow decomposition rate of waste,so efficient and thorough incineration has gradually become the main treatment method.Domestic waste incineration fly ash is a hazardous waste generated in this process,which contains a variety of heavy metals and has the risk of polluting the environment.Geopolymer is a silica-alumina inorganic material,which has the advantages of high strength and good durability.At the same time,due to its three-dimensional network structure of zeolite-like structure can effectively seal heavy metal ions,so in the field of solidification of fly ash/heavy metal Broad prospects.The subject of this article comes from the Dalian Science and Technology Innovation Fund project:solid waste incineration fly ash/fly ash base polymer curing fly ash/heavy metal properties and mechanism,mainly studied the best ratio of fly ash base polymer and its solidified body,The best curing concentration of Pb²⁺and the influence of different external factors on its performance,and through the micro-testing method to analyze the curing mechanism.The main research contents and results are as follows:?1?The effect of the best mix ratio of fly ash base polymer and external factors on its mechanical properties were studied.The results show that the best preparation mix ratio is silicon-aluminum ratio 3.30,sodium-silicon ratio 0.11,water-cement ratio 0.30.The main order of influence on the mechanical properties of geopolymers is:sodium-silicon ratio>water-cement ratio>silicon-aluminum ratio.The compressive strength of the fly ash base polymer 3d,7d and 28d is 45.26MPa,46.66MPa and 48.72MPa respectively.The amount of water glass affects the viscosity of the geopolymer slurry,the amount of NaOH affects its setting speed,and the water-cement ratio affects its fluidity.Alkali activating agent is aged for3h,slurry is stirred for 3min,curing temperature is 65?,and curing time at high temperature is 24h,which is the best preparation and curing conditions.?2?The optimal curing concentration of Pb²⁺based on fly ash base polymer and the effect of various factors on the physical and chemical properties of the cured body were studied,and the curing effect was compared with the cured body of cement.The results show that the optimal solidification concentration of the fly ash base polymer for Pb²⁺is 2.0%.Compared with the pure polymer,the 28d strength of the cured body has decreased,but it still reaches 42.39MPa.At this time,the leaching concentration of Pb²⁺in the 28d cured body was3.35 mg·L^-1,which met the specification requirements.Compared with the Pb²⁺leaching concentration of 4.98 mg·L^-11 of the cement solidified body,the curing effect of the fly ash base polymer is better.Pb²⁺was introduced by the first mixing method,with a stirring time of6 min,a curing temperature of 65°C,and a high-temperature curing time of 24h,which is the best preparation and curing conditions for the polymer solidification body of fly ash base.?3?The mineral composition and micro-morphology of the polymer and solidified body of the fly ash base were studied and the solidification mechanism was analyzed.The results show that the crystalline phases in the fly ash-based polymer are mainly mullite and quartz,and no diffraction peaks of crystalline minerals related to Pb²⁺appear on the solidified body curve,indicating that no new phases appear.The geopolymers are very dense before and after curing,and the structure has not changed significantly.The complex three-dimensional network structure formed by the polymerization of silicon oxytetrahedra and aluminum oxytetrahedra has not been damaged.The solidification of Pb²⁺by the fly ash base polymer is due to the combination of chemical bonding and physical sealing.