Sulfuric Acid Modification Of Fly Ash Microbeads And Adsorption Of Lead-zinc Beneficiation Wastewater

This paper attempts to apply the fly ash microspheres modified by sulfuric acid to treat the mineral processing wastewater and realize"waste treatment by waste".At first,the fly ash microspheres modified by sulfuric acid were studied and the mechanism of acid modification and activation of fly ash microspheres was investigated.Secondly,the adsorption characteristics of residual mineral processing agents and heavy metal ions in the wastewater were investigated,and the adsorption mechanism was revealed from the viewpoint of thermodynamics and kinetics.Finally,an experimental on the adsorption and reuse of mine wastewater was carried out,and the feasibility of the application of the solid adsorbent to treat the mine mineral processing wastewater was demonstrated.The results show that:1)The adsorption performance of fly ash microspheres was greatly improved after modified by sulfuric acid,and the adsorption rate of butyl xanthate increased from 46.82%to 95.00%.The particle size distribution,specific surface area,microstructure,crystal structure,surface functional group and surface zeta potential of fly ash microspheres were measured after acidification.The results show that the increase of surface activity of fly ash microspheres（the Zeta potential increased from-1.7976mV to-15.5387mV）is the main reason for the improvement of adsorbability.The surface roughness was improved by acid corrosion,and the specific surface area was increased from 2.11 m²/g to 2.55m²/g.2)The adsorption characteristics of four organic reagent for lead-zinc ore dressing are completely different from those of fly ash microspheres modified bysulfuric acid;The thermodynamic results show that the adsorption of butyl xanthate is monolayer and accords with the isotherm equation of langmuir adsorption;The adsorption process of sodium humate diethyldithiocarbamate and BK-906 can be described by Freundich adsorption isotherm equation,and the adsorption capacity is sodium humate>ethionitrogen>BK-906;The kinetic results show that theadsorption rate of modified fly ash microspheres on organic reagent is:butyl xanthate>BK-906,sodium humic acid>diethyldithiocarbamate.3)The adsorption experiment of Pb²⁺and Zn²⁺shows that the alkaline cond-ition is favorable to the removal of heavy metal ions.For the Pb²⁺and Zn²⁺single simulated wastewater with an initial concentration of 700μg/L,the adsorption rates of modified fly ash microspheres at pH=9,adsorption time of 3h and dosage of 7g/L are 50%and 40%,respectively.4)The fly ash microspheres modified by sulfuric acid have good adsorption effect on lead-zinc mineral processing wastewater:at pH=9,adsorption time of 3h and dosage of 10g/L,the removal rate of Pb²⁺Zn²⁺is about 60%,but the adsorption rate of Cu²⁺is only 20%,which may be related to its low concentrateion;The removal rate of COD can reach 90%,which solves the problem of poor removal capacity of organic residues by coagulation sedimentation method.5)The reuse of adsorbed wastewater can effectively improve the grade of concentrate and reduce the mutual content of lead and zinc.When the wastewater is diretly used,the grade of lead concentrate and zinc concentrate were 23.80%and43.12%respectively;After adsorption,however,the index was increased to 25.61%and 50.37%respectively,and the impurity in zinc concentrate decreased to 8.40%.The innovation of this paper:The activation mechanism of fly ash microspheres modified by sulfuric acid was clarified:it is mainly from the superficial Si-O-Al vitreous dissolution by sulfuric acid during the modification process,which activates the active points such as Si and Al.The contribution rate of increasing the specific surface area to improve the adsorption performance is relatively small.The absorption test of practical wastewater from lead and zinc from lead-zinc ore dressing shows that the modified fly ash microspheres can effectively remove organic components COD（removal rate about 90%）,but shows different adsorption characteristics and adsorption mechanisms for various organic reagents.