Study On Adsorption Behavior Of Heavy Metals By Functi Onalized Adsorbents From Aquatic Plants

With the rapid advancement of industrial processes,the problem of water pollution caused by the discharge of wastewater containing heavy metal ion has attracted widespread attention worldwide.Heavy metal ions in wastewater have the characteristics of difficult degradation and strong toxicity,which can cause serious damage to organisms.Therefore,it is imperative to develop a simple and efficient technique for repairing heavy metal pollution.Adsorption is a cost-effective,easy-to-use,and easy-to-handle treatment.The choice of adsorbent is the key point of adsorption treatment.Using biomass resources to prepare new adsorbents wit h high adsorption capacity,good reproducibility and biocompatibility,provides not only new functional materials for wastewater treatment and soil remediation,but also a new way for biomass high value.In this paper,Alternanthera philoxeroides,Spirodela polyrhiza,Water hyacinth are used as basic raw materials,and the functionalized adsorbent for aquatic plants is prepared by the cross-linking method,which has the advantages of strong solid-liquid separation ability y,high adsorption ability and good reproducibility.Using functional aquatic plants as adsorbents to remove heavy metal ions in simulated wastewater,the behavior and mechanism of heavy metal ions removal by aquatic plant functional adsorbents are mainly studied.The main contents and results are as follows:1.Adsorption behavior of aminated A.philoxeroides adsorbent（DAP）on Cu（II）in water.The adsorbent particles are prepared by cross-linking the amino group to the surface by a chemical cross-linking grafting method using the biomass A.philoxeroides as a matrix.The morphology,structure and composition of DAP were characterized by SEM,FTIR,XRD and XPS.The influences of influencing factors（such as adsorbent dosage,initial p H value,contact time,temperature and initial concentration）on DAP adsorption performance were studied,and the regeneration performance of DAP was evaluated.The mechanism of removing Cu（II）was discussed based on the characterization of DAP.The results showed that:（1）At p H5.5,100 mg/L Cu（II）,a temperature of 298 K,and an adsorbent dose of 5.0 g/L,the adsorption capacity and removal rate of Cu（II）reached 19.33 mg/g and 95.57%,respectively.（2）Kinetic and equilibrium studies show that the pseudo-second-order kinetic model（R²=0.9964）and the Langmuir model（R²>0.982）are consistent with the adsorption behavior of DAP.（3）Based on FTIR and XPS research shows,the main reason for the enhancement of Cu（II）adsorption is the complexation of amino groups with metal ions.The adsorption mechanism of DAP on Cu（II）is mainly chemical complex adsorption.（4）The adsorption efficiency of the adsorbent was high,and the adsorption efficiency of DAP decreased by only 27.94%after adsorption-desorption for 6 times.（Chapter 2）2.Adsorption behavior of aminated S.polyrhiza adsorbent（DSP）on Ni（II）and Pb（II）in water.The DSP adsorbent was prepared by the joint action of epichlorohydrin,N,N-dimethylformamide and diethylenetriamine on the basis of biomass S.polyrhiza.The morphology,structure and composition of DSP were characterized using SEM,Zeta,FTIR and XPS techniques.The influence of influencing factors（such as adsorbent dosage,initial p H value,contact time,temperature and initial concentration）on the adsorption process of Ni（II）and Pb（II）by DSP was studied.The results show that:（1）DSP has obvious advantages in pollutant adsorption,and it has typical fold structure,key functional groups（-OH and N-H）and high adsorption capacity.The FTIR and XPS analysis indicated that the-OH and N-H functional groups are involved in the adsorption of Ni（II）and Pb（II）.（2）In the experiment,the optimum p H values of the adsorption of Ni（II）and Pb（II）by DSP are about 6.5 and 5.5 respectively,and the optimal adsorbent dosage is 5 g/L.The maximum adsorption capacity of DSP for Ni（II）and Pb（II）is 45.68 and 51.75 mg/g,respectively,while the maximum adsorption capacity of SP was 6.57 and 7.98 mg/g,respectively.（3）Using the pseudo-second-order kinetics model and the Langmuir isotherm adsorption model make a good fit,and this is a spontaneous and endothermic process at high temperature.（4）Using Na₂EDTA as a desorbent,after 5 adsorption and desorption experiments,the adsorption efficiency of DSP for Ni（II）and Pb（II）remained at 56.47%and 62.18%.（Chapter 3）3.Adsorption behavior of carboxylated W.hyacinth adsorbent（CWH）on Cu（II）,Ni（II）and Cr（VI）in water.The biomass W.hyacinth was used as a matrix,and CWH was prepared by cross-linking with citric acid.The effects of influencing factors（such as adsorbent dosage,initial p H value,contact time,temperature and initial concentration）on the CWH adsorption process of Cu（II）,Ni（II）and Cr（VI）were studied.The results show that:（1）The optimum p H values of Cu（II）,Ni（II）and Cr（VI）in CWH adsorption solution are 7.5,6.0 and 5.0 respectively;the optimal contact time is 300,180 and 120 min respectively;the optimum adsorbent dosage is 6.5,5.0 and4.0 g/L,respectively.（2）The adsorption process of Cu（II）,Ni（II）and Cr（VI）by CWH accords with Langmuir model and pseudo-second-order kinetic model.The maximum adsorption capacities are 59.64,77.98 and 96.89 mg/g,respectively.The thermodynamic model shows that the reaction is an endothermic spontaneous process.（3）After 5 experimental studies on regeneration performance,the removal ratios of CWH to Cu（II）,Ni（II）and Cr（VI）remained at 55.23%,65.63%and 71.46%,indicating that CWH still showed good regeneration performance after repeated recycling.（4）The results of SEM,FTIR and XPS analysis showed that the surface roughness of CWH and the number of micropores increased,and the carboxyl group was successfully introduced into the surface of the material particles.（Chapter 4）...