Study On Treatment Of Lead-containing Wastewater By Carrier Induced Crystallization

Lead is a toxic heavy metal,which is widely used in human production and life;but it can accumulate in the human body,causing great harm and risk to human health and plant growth;with the rapid development of modern industry,lead-containing wastewater The pollution situation is becoming more and more serious,and the harm to human health and the environment has become a hot issue of global concern.The chemical precipitation method is a common disposal method for lead-containing wastewater,but it has the disadvantages of slow reaction speed and complicated disposal process.The carrier-induced precipitation technique is an improvement of the conventional chemical precipitation method,which can shorten the reaction time and simplify the process.In this study,Pb²⁺-containing water was used as the treatment object,and Na₂S·9H₂O was used as the precipitant to obtain the optimal conditions for Pb²⁺removal without carrier.Under these conditions,the effect of Pb²⁺removal by the alternative carrier and its zeta potential in the precipitation system were compared.In order to induce the best effect of Pb²⁺removal,the relationship between Pb²⁺effect and the isoelectric point of the carrier in different systems was investigated.The factors affecting the zeta potential of the carrier during the induction of precipitation were investigated,and the priority of the Pb²⁺process was analyzed.Control factors;investigate the effect of the best carrier induced crystallization in addition to Pb²⁺from different sources;perform the surface dissolution and influence test with the best effect as the carrier,analyze the dissolution kinetics and the effect of dissolved ions on Pb²⁺;Characterization test,combined with surface dissolution test results,analysis of the inductive crystallization process in addition to Pb²⁺process;for the best carrier hardness and brittle defects,the preliminary study of the best carrier composite was carried out to obtain a carrier with good removal effect and high hardness;The magnetic separation technique was used to separate the carriers after the crystallization,and the optimal carrier magnetic composite was initially carried out.The results show:（1）The optimal conditions for Pb²⁺removal without carrier are:system p H is6.0,precipitant dosage ratio is 5:1,reaction time is 40 min;comparison of different carriers induces crystallization except Pb²⁺effect,dolomite is the best induction In the process of induced crystallization,the zeta potential of the carrier is negative,the closer to the isoelectric state,the better the induction effect.The zeta potential of the carrier is closely related to the induction effect during the induction of crystallization,which can be based on the zeta potential of the carrier during the induction of crystallization.Change to choose the best carrier.（2）In the deionized water system,the Pb²⁺-containing water distribution system and the precipitation system,the Pb S precipitation effect is correlated with the isoelectric point of different carriers.The larger the isoelectric point of the carrier,the better the effect of inducing Pb S precipitation,the deionized water system carrier,etc.The electric point determination is the simplest and can be used as the best method for carrier selection.In the induced precipitation,different influencing factors have significant effects on the Zeta potential of the same carrier,and the factors affecting the Zeta potential are different for different carriers.（3）The optimum conditions for the induction of dolomite in Hebei are:p H 5.0,precipitant dosage ratio of 2:1,carrier dosage of 20 g/L,equilibrium time of 20 min;dissolution of Ca²⁺and Mg²⁺on the surface of dolomite in Hebei The kinetic model;the surface exchange of Pb²⁺with Ca²⁺and Mg²⁺in the precipitation system,the induced precipitation can occur on the surface of the carrier;in the induced system,the increased concentration of dissolved Ca²⁺and Mg²⁺can promote the surface exchange of Pb²⁺with Ca²⁺and Mg²⁺,and improve Induction efficiency.（4）The optimum preparation conditions of Hebei dolomite composite particles are:dolomite:quartz sand:bentonite=5:4:1,the amount of pore former Na₂CO₃is5%,the calcination temperature is 700°C,and the calcination time is 2 h.Under the optimal induction condition of dolomite in Hebei,the composite particles induced the removal efficiency of Pb²⁺by 99.00%,which achieved the purpose of improving hardness and not reducing the removal effect.The optimum preparation conditions of Hebei dolomite magnetic composite particles are:dolomite:quartz sand:bentonite:magnetite=5:4:1:2,the amount of pore former Na₂CO₃is 5%,the calcination temperature is 700°C,and the roasting time is 2 h.Under the optimal induction condition of Hebei dolomite,the magnetic composite particles induced Pb²⁺removal efficiency of 99.42%and effluent turbidity of 9.4 NTU.The magnetic separation effect was good,and the purpose of improving hardness,reducing removal effect and rapid separation was achieved.