Study On The Adsorption Behavior Of Metal Ions Onto The Typical Adsorption Resins And The Prediction Model Of Quantitative Structure-Activity Relationship

At present,heavy metal pollution is a persistent and long-standing problem in industrial wastewater.Adsorption technology has become one of the commonly used technologies for the removal and recovery of heavy metal wastewater due to its small footprint and easy operation.In the term of adsorption technology,the functional groups on the surface of the adsorbent play a key role in the removal of metal ions,and one type of adsorption functional groups can often adsorb various metal ions at the same time.Therefore,exploring the adsorption characteristics between different typical adsorption functional groups and metal ions will be beneficial to the development and research of adsorbent materials.This study selected four different types of adsorption resins containing carboxyl,sulfonic acid,amine,and phosphoric acid groups as the research object,choose 9 common heavy metal ions,i.e.Cu（II）,Ni（II）,Zn（II）,Cd（II）,Mn（II）,Pb（II）,Hg（II）,Co（II）and Cr（III）,to study adsorption performance in a single metal component solution and binary metal components.The selective adsorption performance in competitive adsorption was studied;the adsorption mechanism was investigated from the microscopic level with the material characterization analysis and quantum chemical calculation;through the study of adsorption resin structure parameters,metal ion physical and chemical parameters,the quantitative-structure-activity relationship between the adsorption capacity of heavy metal ion and the stryctre parameters of adsorption resin and the physicoehmical parameters was studied.The prediction model for the adsorption of heavy metal ions onto diversified resin was constructed.Finally,the adsorption capacity test was carried out with the resin which contained the same type of group employed in the construction model to verify the applicability of the prediction model.The isothermal adsorption experiments in single and binary metal component solution,respectively,was cariied out.The maxium adsorption capacity in the single and binary metals system was calculated by Langmuir isotherm model.The adsorption energy calculated by the density functional theory（DFT）was employed to to analysis the the adsorption behavior of 9 kinds of heavy metal ions onto four types of adsorotion functional group.The ranking of the maximum adsorption capacity of the of the resin with carboxyl groups in a single metal component solution was obtained;and the ranking of the selective adsorption performance of each metal of the resin with carboxyl groups in the competitive adsorption process of the binary metal component solution was obtained.Accroding to the characterization analysis of FTIR and XPS,it could be inferred that the adsorption mechanism was the mainly the electrostatic adsorption and chelation of negatively charged groups such as carboxyl,sulfonic acid,amine,and phosphoric acid groups on the adsorption resin.Among four type of the resins used in this stydy,electrostatic attraction was speculated as the main mechanism between the resions of WK10,UBK550and metal ions;the mechanism between the resins of TP260,CR11 and metal ions might be the electrostatic attraction combined action of chelation.At the same time,the calculation results of quantum chemistry based on DFT also showed that the adsorption mechanism was mainly the electrostatic attraction and chelation of metal ions on the active group of the resins.The prediction model of the maximum adsorption capacity of four types of adsorption resins for heavy metal ions in a single-component solution was established by using multiple linear regression method.The simulated results showed that some common factors influenced the adsorption capacity of metal ions onto 4 types of adsorption resin.During the adsorption process of metal ions onto resins,as to the characteristics of the metal ions,electronegativity X_m,ion radius AW,and first ionization hydrolysis constant|log K_OH|were convinced to the main effect factors;as for the adsorption resin,the electrostatic potential charge of related functional groups and metals and,Fukui function could affect the adsorption capacity of different typs of resin.In the case of heavy metal ions,the higher the covalent index of the heavy metal ion and the larger the Fukui function value was,the greater the adsorption capacity on the adsorption resin was obtained;the electrostatic potential charge difference between the relevant atom and the metal ion at the active sites of the adsorption resin showed a positive effect on the adsorption capacity.The larger the value of the Fukui function of the relevant atoms on the active sites of the adsorption resin showed a greater the adsorption capacity,indicating a stronger the interaction with heavy metal ions.The models were verified using the same type of functional resin,and the experimental results falled within the prediction interval,indicating a good predictability of the models.Using the principal component regression analysis method,the model analysis of the competitive adsorption of metal ions in the binary component solution was carried out.During a binary component solution,it seemed to be difficult to establish a good linear relationship with the descriptor,since the selectivity coefficient was proposed to be related to the concentration of heavy metal ions,p H,temperature and other factors.However,it was found that the ion selectivity of the adsorption resin was still related to the atomic weight AW and the covalent index X²mr,which was consistent with the rules in the single-component solution.