Preparation And Modification Of Solid Waste-based Ceramsite And Its Application For Adsorption Of Pb²⁺

The output of solid wastes in Inner Mongolia is huge and there are many kinds of solid wastes generated in Inner Mongolia,which has a huge output.Therefore,Pollution control and resource utilization of solid wastes are widely concerned environmental problems.In this paper,ceramsite was prepared from solid wastes such as construction waste,fly ash and red mud.Ceramsite was modified by acid-base modification.The modified ceramsite was used to adsorb Pb²⁺in wastewater,and its adsorption mechanism was studied.This study provides a technical route for“Recycling-Preparation-Application”.It achieves the goal of"treating pollution with waste".The results of this study are as follows:（1）The optimum preparation conditions of ceramsite were as follows:construction waste:fly ash:red mud=10:2:3,adding 1/10 rice husk ash,with sintering temperature of 1150℃and heat preservation of 10 min.The properties of the prepared ceramsite met the requirements of standards of CJ/T 229-2008 and GB5085.3-2007.The average pore size of ceramsite was about 1μm.The main phases in ceramsite were quartz,magnetite,anorthite,kaolinite,calcite and mullite.The experiment showed that the ceramsite has a high efficiency for biofilm colonization and short start-up cycle.It can be used as biological filler in water treatment.（2）Ceramsite modification include acid modification and alkali modification.The modification conditions were as follows:（1）acid modification:Taking sintered ceramsite as raw material and mixed acid as modifier,with liquid-solid ratio of 5:1,acid concentration of 5 mol/L,water bath temperature of 80℃,reaction time of 4 h;（2）Alkali modification:taking acid modified ceramsite as raw material and 4 mol/L Na OH as modifier,with liquid-solid ratio 5:1,water bath temperature 60℃,reaction time of 6 h.After acid-base modification,the specific surface area and pore volume of ceramsite were greatly increased,the average pore size was significantly reduced,and a large number of-OH groups were loaded on the surface of ceramsite,which supplied a chemical foundation for the modified ceramsite as a heavy metal ion adsorbent.（3）While the initial concentration of Pb²⁺in the solution was 100 mg/L,the p H was<6.0,the dosage of modified ceramsite is 4.0 g/L,and the adsorption time was 4h,the removal rate of Pb²⁺reached 99.09%.The fitting results of adsorption kinetics and thermodynamics showed that the adsorption process was more in line with the second-order kinetic model and Langmuir isothermal adsorption model,and the maximum adsorption capacity is 34.3407 mg/g.The-OH group in modified ceramsite plays a major role in the adsorption.The appearance of Pb₂Cl OH and Pb O in ceramsite after adsorption indicating that chemical adsorption is happened in the adsorption of with Pb²⁺onto ceramsite.