| With the development of urban industrialization,the problems of heavy metal pollution and solid waste disposal have become increasingly prominent.In this paper,fly ash,slag and dewatered sludge are used as raw materials to prepare ceramsite adsorbent.Through orthogonal experiment,single factor experiment,desorption regeneration experiment and actual wastewater adsorption experiment,the optimal preparation conditions of ceramsite and its adsorption and regeneration characteristics for lead-containing wastewater are clarified.Through the fitting and characterization analysis of adsorption kinetics,adsorption isotherm model and adsorption thermodynamic model,the adsorption mechanism of ceramsite to lead-containing wastewater is explored.Provide a theoretical and data basis for the resource utilization of power plant waste and sludge and the treatment of lead-containing wastewater.The optimal preparation conditions of ceramsite are:raw material ratio（fly ash:slag:sludge）,roasting temperature,roasting time and preheating temperature of 60%:35%:5%,1075℃,15 min and 300℃,respectively.The ceramsite prepared under better conditions meets the requirements of"Artificial Ceramsite Filter Material for Water Treatment"（CJ/T 229-2008）and"Identification Standard for Hazardous Waste-Identification of Leaching Toxicity"（GB 5085.3-2007）,mainly large holes and middle holes.It mainly contains functional groups such as hydroxyl,carbonyl and Si-O,and the main mineral components are quartz,mullite,anorthite and hematite.The optimal adsorption conditions for ceramsite to treat lead-containing wastewater are:ceramsite particle size,p H value,adsorption time and adsorption temperature are 4mm,4.5-5.0,360 min and 25℃,respectively.The best desorbent used in the regeneration of ceramsite is 0.5 mol/L HCl solution,and the best desorption time and times are 120min and 5 times respectively.The removal rate of Pb2+by the ceramsite after 5 times of desorption is 92.67%.When treating a lead storage battery factory with an initial concentration of 3.74 mg/L of chemical precipitation wastewater and ceramsite dosage of20 g/L,the Pb2+concentration in the treated wastewater is 0.24 mg/L,It meets the requirements of the maximum allowable emission concentration limit（1.0 mg/L）of Pb2+for the first category of pollutants in the Comprehensive Wastewater Discharge Standard（GB 8978-1996）.The chemical adsorption between ceramsite and Pb2+is a spontaneous exothermic reaction.This adsorption process better follows the quasi-second-order kinetic model and Freundlich adsorption isotherm model.The CH2,Si-O and O-H functional groups on the ceramsite play a major role in the adsorption of lead-containing wastewater.After the ceramsite adsorbs Pb2+,new phases Pb2Cl3OH and PbO appeared. |
