Preparation Of Static Suspension Magnetic Biosorbent And Its Adsorption Of Lead Ions

At present,industrial and mining enterprises will discharge a large amount of industrial wastewater containing heavy metals?such as Pb,Cu,Zn and Cd,etc.?during production and operation,resulting in serious heavy metal pollution in water environment.Heavy metals are bioaccumulative in the environment,difficult to be biodegraded,and pose a direct threat to the environment and human health.Therefore,the discharged heavy metal wastewater must be treated to meet the emission standards of pollutants for secondary copper,aluminum,lead and zink industry?GB31574-2015?.The actual heavy metal wastewater treatment methods mainly include physical methods,chemical methods and biological methods.The physical method is suitable for the treatment of heavy metals with low content,high toxicity and recycling value,but the biggest disadvantage is that the cost is too high.The chemical method has the advantages of wide treatment range,simple and high efficiency,and convenient operation,but the method is ea sy to cause secondary pollution and more waste residue.The biosorption method mainly removes heavy metal ions in wastewater by ion exchange,physical and chemical action,and has the advantages of wide material source,low cost,high cost and no secondary pollution.Finding good adsorbent materials is the focus of research at this stage,and it has important value and meaning for treating heavy metal wastewater.In this study,two kinds of biosorbents containing polyethylene foam and polyethylene-free foam were prepared based on sodium alginate,walnut shell powder,magnetic nanoparticles and polyethylene foam.In addition,the modified mesoporous molecular sieve adsorbent was prepared by hydrothermal synthesis and modified by ammonia triacetic acid.?1?Exploring the enhanced removal effect of ultrasonic technology on the treatment of lead-containing wastewater without polyethylene foam composite biosorbent;?2?Studying the composite biosorbent?AMWSF?containing polyethylene foam in airlift magnetic separation loop system to the adsorption effect of lead-containing wastewater on the lead;?3?The adsorption effect of NTA anhydride-modified mesoporous molecular sieve adsorbent on lead-containing wastewater was studied.Finally,different adsorption conditions(pH,adsorbent dosage,reaction temperature,reaction time and initial Pb²⁺concentration)were optimized.The characteristics of kinetic and isothermal adsorption were discussed,and the adsorption performance and mechanism were studied.The results were as follows:?1?Ultrasound and control treatment experiments showed that,pH 6.0,0.1 g of adsorbent dosage,25?,reaction time 120 min and lead ion concentration of 100mg·L^-1 in 100 mL solution were the optimal conditions for ultrasonic treatment.When sonicated,the adsorption capacity increased from 69.62 mg·g^-1 to 90.85 mg·g^-1;the equilibrium reaction time was shortened from 240 min to 120 min.The ultrasonic treatment process was in accordance with the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model.The hydroxyl,amino,amide and carboxyl groups of the biosorbent played an important role in the removal of lead ions.The enhanced removal effect of actual heavy metal wastewater under ultrasonic treatment provided theoretical support and technical guidance for the removal of industrial scale heavy metal wastewater.?2?In airlift magnetic separation loop system,AMWSF adsorbed lead ion optimal pH,adsorbent dosage,temperature and reaction time were reached at 6.0,0.1g,25?and 180 min,respectively.The equilibrium adsorption capacity of AMWSF could reach 69.45 mg·g^-1.The adsorption process could be well described by pseudo-second-order kinetic and Langmuir isotherm adsorption models.SEM-EDS analysis showed that lead-containing crystals formed on the surface of AMWSF,and FTIR showed that carboxyl,hydroxyl,carbonyl and amino groups played an important role in the removal of lead ions.It was confirmed by competitive adsorption experiments that the coexisting heavy metal ions Cu?II?,Cd?II?and Zn?II?have antagonistic effects on the removal of Pb?II?.The order of antagonism was Cu?II?>Cd?II?>Zn?II?.Since the airlift magnetic separation loop system reduced the shear failure of the mechanically agitated AMWSF,the AMWSF could be effectively reused7 times.?3?The NTA anhydride-modified mesoporous molecular sieve adsorbent prepared by hydrothermal synthesis and ammonia triacetic acid modification could treat lead-containing wastewater well,and the equilibrium adsorption capacity reaches40.8 mg·g^-1.The optimal conditions for the treatment of lead-containing wastewater by modified mesoporous molecular sieve adsorbent:pH 6.0,adsorbent dosage 0.6 g,temperature 25?and reaction time 60 min.The process of treating lead-containing wastewaterbymodifiedmesoporousmolecularsievesconformsto pseudo-second-order kinetics?R²=0.997?and Langmuir?R²=0.999?isotherm adsorption models.As can be seen from the SEM images,the floc structure on the surface of the adsorbent showed more bright crystals,indicating that the modification of ammonia triacetate improved the ability of the adsorbent to bind lead ions.FTIR revealed that the amino,hydroxyl,alkyl,ester and carboxyl groups on the surface of the modified mesoporous molecular sieve adsorbent participated in the lead ions adsorption process.